introduction · 1. unlike standard volumetric analysis, it is not possible with karl fischer...

1

Introduction

The methods used to analyze moisture content in substances range fromthe loss-on-drying method to physical, electrical and optical systems.Moisture content measurement by means of Karl Fischer reagents is nowwidely employed as the only reliable chemical method. Today the method is widely accepted as a moisture content measurementsystem for both chemicals and manufactured products. It has beenadopted as an international standard by the International StandardsOrganization (ISO), as an American Standard Testing Method (ASTM) in theUnited States, and is also included in the German DIN standards and theBritish BS system. The method has also been incorporated into Japanesestandards, including the Japanese Industrial Standards (JIS) and JapaneseAgricultural Standards (JAS). It is also included in Japanese pharmaceuticalpractice, the official food additive manual, and the Japan Petroleum InstituteStandards.

Development of Karl Fischer Reagents

The German scientist Karl Fischer (1901-1958) first revealed his newreagent to the world in a paper [NOTE 1] published in 1935. A mixture ofiodine, sulfur dioxide, pyridine and methanol, it was named after its inventor.As shown in the following formula, Karl Fischer reagents react selectively towater in specific amounts. Mitchell & Smith subsequently carried out adetailed study of the reaction [NOTE 2] and published findings thatindicated a reaction of 1 mole of iodine to 1 mole of water. This basicreaction formula remains in use today.

H2O�I 2�SO2�3 P y � 2 Py � HI�Py � SO3

Py � SO3�CH3OH � Py � HSO4CH3

In recent years, however, the Karl Fischer reaction mechanism has beenstudied on a more theoretical level. A published paper [NOTE 3] shows thatthe pyridine acts simply as a buffer and that it is not essential to thereaction. The following reaction formula, in which pyridine is expressed as abase, has been put forward.

2

H2O�I2�SO2�3Base�CH3OH � 2Base � HI�Base � HSO4CH3

Note: Base = Amin. "Base" is sometimes shown as RN.

Characteristics of the Karl Fischer Titration Method

The measurement of moisture content using Karl Fischer reagents issuperior to other methods such as loss-on-drying, distillation and infraredabsorption, or to electrolysis and other electrical methods, for the followingreasons:(1) The absolute amount of moisture can be determined without a

working curve (in the case of coulometric titration). Moisturecontent can be determined accurately, even where moisture is present at levels of only a few ppm.

(2) Measurements can be taken over short periods of time. (3) Measurements can be taken using small samples (from a few

mg to a few gm). (4) The method can be used with liquid, solid and gaseous

samples.(5) The method is suitable for unstable substances that can alter

when heated.

Mitsubishi Chemical Corporation and Karl Fischer Reagents

Mitsubishi Chemical Corporation recognized early on the advantages of theKarl Fischer reagent, when it was introduced into Japan in the postwar era.The company began to investigate this in 1950. It subsequently developedKarl Fischer reagent SS, a single solution with stable titer that could be usedby anyone in factory research or analytical laboratories. It also developedand supplied a variety of dehydrating solvents for use with various types ofsamples. In addition, Mitsubishi Chemical Corporation developed simplemethods for measuring the moisture content of various substances andmanufactured products. With each new methodology, the companyendeavored to promote the use of the Karl Fischer titration method throughpapers for scientific symposiums and society journals (about 60 to date). In 1985, Mitsubishi Chemical Corporation developed a new Karl Fischerreagent without the pyridine odor. The new pyridine-free products werenamed the "S-Series". The company continues to respond to the needs of itscustomers. In 1992, it added the X-Series products, which do not containcarbon tetrachloride or chloroform, to its range of coulometric reagents. This manual has been written to provide basic information on Karl Fischer

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reagents and analytical methods. As we want this manual to haveimmediate application, we have used the Q&A approach to make it easy tofind needed information. We hope that this manual will become a usefulreference guide and one that will serve to build and improve knowledge ofour range of Karl Fischer reagent products.

(1) Fischer, K.; Angew. Chem., 48,394 (1935).(2) Smith, D.M., Bryant. W.M.D., Mitschell; J.; J.Am.Chem.Soc., 61,2407

(1939).(3) Verhoef, J.C.; J. Electroanal.Chem., 71,305 (1976), 75,705 (1977).

March 2004

5

CONTENTSCapter I: Basic Knowledge

I-1 Questions & Answers about Karl Fischer Reagents

1. Karl Fischer Titration

Q1 :What are the other methods currently avaikable for themeasurement of moisture content? Please explain howthese differ from karl fischer titration?

Q2 :Please explain briefly how moisture content is measuredusing Karl Fischer reagents?

Q3 :Could you outline the principle and procedures involvedinvolumetric titration?

Q4 :Please outline the principles and procedures involved incoulometric titration.

Q5 :What is the moisture vaporization method, and when is itused?

2. Karl Fischer Reagent Products

Q6 :Wha volumetric titration reagents are available? Please explain the types of reagents and their uses, and themethods employed.

Q7 :What coulometric titration reagents are there? Pleaseexplain the types of reagents and their uses, and themethods employed.

3. Applicability of Karl Fischer Titration

Q8 :Whaat substances is Karl Fischer titiration suitable for?

Q9 :What is interference in the context of the Karl Fischertitiration? Please explain what is meant by interferencereactions.

Q10:Please outline any methods that can be used to suppressinterference reactions so that Karl Fischer titration can beemployed.

4. Procedures for Karl Fischer Titiration

Q11:How should we actually carry out volumetric titration?Please describe the preparations and procedures involved.

Q12:How can we actually measure moisture content usingcoulometric titration? Please describe the preparations andprocedures involved.

Q13:Sampling procedures aro one of the most important aspectsof moisture content measurement. What are the specificmethods and equipment invokved?

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5. Officiak Testing Methods and Documentation

Q14:Karl Fischer titiration is classed as an official testing method.What Japanese standards have been adopted?

Q15:Please provide some example of the internationalstandards(ISO)and foreign standards that have been adoptedfoe the Karl Fischer titration method.

Q16:What reference works aare there concerning Karl Fischermeasurement methods?

6. Important Informatiom about Handling and Using Karl FischerReagents

Q17:Are there any safety requirements or other precautions thatshould be followed when using Karl Fischer reagents?

Chapter II Applications Part 1

II-1 Organic Compounds

1.Hydrocarbons

2.Halogenated Hydrocarbons

3.Alocohols

4.Ethers

5.Phenols

6.Ketones

7.Aldehydes

8.Organic Acids

9.Esters

10.Organic Acid Salts

11.Organic Hydrates

12.Amines

13.Amides, Anilides

14.Nitriles, Cyanohydrins

15.Hydrazines

16.Other Nitrogenous Compounds

17.Acid Anhydrides

18.Acid Chlorides

19.Quinones

20.Peroxides

21.Sulfur Compounds

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 59

� � � � � � � � � � � � � � � � � � � � 59

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 63

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� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 67

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� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 82

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� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 96

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 100

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 101

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 102

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 103

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 105

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 105

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 106

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 107

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 108

7

II-2 Inorganic Compounds

1.Metals and Simple Substances

2.Inorganic Acids

3.Hydroxides

4.Oxides

5.Halides(halogenides)

6.Carbonates, Bicarbonates

7.Sulfates, Sulfites

8.Other Salts

9.Inorfanic Gases

Chapter III Applications-2

III-1.Industrial Products

1.Fertilizers

2.Agricultural Chemicals

3.Glasss/Ceramics

4.Liquefied Petroleum Gases

5.Coals, Tars

6.Petroleum Products

7.Plastics

8.Rubber, Rubber Products, Compounding Agents

9.Fibers, Papers

10.Dyestuff Intermediates

11.Pigments

12.Paints

13.Printing Inks and Imaging Materials

14.Adhesives

15.Soaps and Detergents

16.Cosmetics

17.Chemicals & Materials for Electronic Equipment and Electrical Parts

III-2.Foodstuffs

1.Food Additives and Flavorings

2.Cereals and Dried Vegetables

3.Sugars and Condiments

4.Confectionery

5.Dairy Products, Fat Products

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 112

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 113

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 115

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 118

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 119

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 121

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 123

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 125

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 127

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 129

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 131

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 133

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 133

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 135

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 136

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 138

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 141

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 143

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 147

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 150

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 152

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 153

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 155

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 156

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 158

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 159

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 161

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 163

� � � � � � � � � � � � � � � � 165

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 167

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 167

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 171

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 173

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 174

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 176

8

6.Goument Foods, etc.

III-3.Pharmaceuticals

1.Biochemical Products

2.Pharmaceuticals

3.Chinese Herbal Medicines, Biological Tissue, etc.

III-4.Minerals and Natural Products

1.Minerals

2.Natural Products

Chapter IV List of Karl Fischer Reagents

Chapter V Summary of Selection Procedures for KarlFischer Reagents

Chapter VI Index

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 178

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 180

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 180

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 182

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 184

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 186

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 186

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 189

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 191

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 199

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 201

Capter I: Basic Knowledge

9

Capter I: Basic Knowledge

Chapter I: Basic Knowledge

11


I-1. Questions & Answers about Karl Fischer Reagents

1. Karl Fischer Titration

Q1 What are the other methods currently available for the measurement ofmoisture content? Please explain how these differ from Karl Fischertitration?

There are many ways of measuring moisture content. Methods based onnew principles are still being announced. The following table lists theprimary methods in current use. Karl Fischer titration is regarded as themost useful of these methods by virtue of its wide applicability and itscapacity to measure absolute values. It is the focus of continuing research.

Q2 Please explain briefly how moisture content is measuredusing Karl Fischer reagents?

There are two methods based on the use of Karl Fischer reagents, or KarlFischer titration, to measure moisture content.

1. Methods

Measurement method Measuring range Applications Interfering substances

Karl Fischer titration

Drying

Azeotropic distillation

Colorimetric method

Infrared absorption

Gas chromatography

Dew point method

Electrolysis

Electric resistance (Conductimetric method)

Dielectric constant method

Neutron scattering method

Quartz oscillation method

A few ppm - 100%

0.01%

0.05%

0.1-a few %

0.01-a few %

ppm-a few %

ppm-a few %

1-1000ppm

0.3%-a few %

1-a few %

a few %

1-1000ppm

gases,liquids, solids

solids

liquids

solids, liquids

gases, liquids, solids

gases, liquids

gases

gases

gases, liquids

gases, liquids

solids

gases

Oxidizing,reducing substances

Volatile substances, unstable substances

Volatile water-soluble substances

Colored substances

Alcohol,amine, etc.

Substances with the same retention capacity

Condensable substances

ROH, RCHO, NH3, HF

Conductive substances

Substances with high dielectric ratios

Substances containing hydrogen

Substances thatreact with sensing membranes


12

(1) Volumetric titration (2) Coulometric titration

Your choice should reflect a proper understanding of each method. It is alsoessential to use the appropriate reagent in each case. The following tablecompares the characteristics of each method.

For your information

1. Unlike standard volumetric analysis, it is not possible with Karl Fischertitration simply to fill a buret with Karl Fischer reagent and add it one drop

With Karl Fischer titration, electrical detection methods are used todetermine the end point. It is important to use the following types of titrationequipment.Volumetric titration : Automatic volumetric moisture meter Coulometric titration : Automatic coulometric moisture meter There are now convenient automatic moisture measurement systemsdesigned for ease of operation. As Karl Fischer reagents are affected by atmospheric moisture, an airtighttitration cell must be used.

2. Titration Equipment

Principle

Titration reagents

Characteristics

A method of volumetric analysis used todetermine moisture content from thetitrated amount of Karl Fischer reagent

Karl Fischer reagent and titration solvent(dehydrated solvent)

1) Since a Karl Fischer reagent is used asthe titration agent, the titer must beknown in advance.

2) A wide range of reagents can be usedas various dehydrating agents areavailable.

3) The method can be used to measuremoisture content across a wide range.However, it is not suitable at themicrogram level.

Iodine produced through electrolyticoxidation undergoes a KF reaction withwater. Moisture content is determined bymeasuring the amount of electricityrequired to the point where excessiodine is produced.

Anolyte and catholyte

1) The factors measured are current andtime. Since electrons act as the titrationagent, a standard solution is notrequired. The method allowsmeasurement of absolute quantitiesbased on the Faraday constant.

2) The same anolyte can be usedrepeatedly.

3) The method is effective for measuringminute amounts of water. Electricitycan be measured in tiny increments,so it is possible to measure water inquantities of a ug

Item Volumetric titration Coulometric titration


13

at a time to a flask or beaker that is exposed to the air. Since Karl Fischerinstantly reacts with atmospheric moisture, the end-point would never bereached.

2. At present there is no method that allows the color change at the end-point of Karl Fischer titration to be detected visually. The only method isto detect minute amounts of surplus iodine electrically.

Helpful hint -1 !How is the end-point detected electrically?

The volumetric and coulometric titration systems currently on the marketemploy controlled current voltage detection (constant-current polarizationvoltage detection). A constant current of 1-30uA is applied to two platinumelectrodes, and the end-point is detected by measuring the voltage(polarization voltage) between the electrodes. If the titration solution has arelatively high water content, a polarization voltage of 300-500mV will beproduced. The voltage varies according to the type of solvent used and thesample. In general, high voltages are produced in the case of substanceswith low conductivity, such as hydrocarbons. As the Karl Fischer titration continues and the end-point approaches, thevoltage will suddenly drop to 10-50mV. With volumetric analysis, the end-point is deemed to have been reached after the voltage has remains at thislevel for a specific period of time. With commercially available titrationsystems, the period is 30-60 seconds. With coulometric analysis, an end-point voltage is specified, and the end-point is reached when the voltagefalls below that level.


14

This value is used to determine the quantity of a substance from the amount ofreagent titrated. It shows the equivalent amount of water per unit of volume andis usually expressed as mgH20/ml.

Memo "Titer"

[Procedures]

a) A dehydrated solvent suitable for the sample is placed in a flask attachedto an automatic volumetric moisture meter (Figure 1).

b) The Karl Fischer reagent is titrated until all water has been eliminatedfrom the titration flask. (It is not necessary at this time to read the amounttitrated.) The titer of the Karl Fischer reagent is determined using water,etc.

c) The sample is added. d) The Karl Fischer reagent, the titer of which (mgH20/ml) has now been

determined, is titrated until the end-point is reached. The end-point isdetected electrically by means of a detection circuit built into the titrationsystem.

e) Moisture content is determined from the amount titrated according to the

Q3 Could you outline the principle and procedures involved involumetric titration?

[Principle]

Karl Fischer titration is a volumetric analysis method that takes advantage ofthe fact that iodine contained in Karl Fischer reagents reacts quantitativelyand selectively with water, as shown in the following formula.

I2 � SO2 � H20 � 3Base � CH3OH � 2Base � HI � Base � HSO4CH3

The quantification is based on the stoichiometrical principle that 1 mole ofiodine (254g) reacts with 1 mole of water (18g). In practice, the titer of a KarlFischer reagent is expressed as a water equivalent. Unlike normalvolumetric analysis methods, the concentration of iodine is not shown. Forexample, Mitsubishi Chemical's SS-X Karl Fischer reagent is adjusted sothat 1ml will react with approximately 3mg of water, which means that thesolution contains approximately 42mg of iodine and has a 3mg titer. Oncethe water equivalent of a Karl Fischer reagent is known, it is possible todetermine moisture content from the amount used (titrated).


15

following formula:

Moisture content (%)= � 100Titration quantity (ml) � titer (mgH2O/ml)

Sample quantity (g) � 1000

Figure 1: Automatic Volumetric Moisture Titration System

Drying tube

Sampleinjection port

Detection electrode

Titrationbath flask

Rotor

Control system

Display/recording system

Magnetic stirrerKarl Fischer reagent

Drying tube

Buret

Titrationnozzle

Automatic switching valve

Detectionunit

Recording Display

C o n t r o lunit

Measurement system


16

Q4 Please outline the principles and procedures involved incoulometric titration.

[Principle]

With coulometric titration, electrolytic oxidation is achieved by adding thesample to an iodide ion solution, instead of the iodine contained in the KarlFischer reagent and used as the titration agent for volumetric titration. Asshown in the following formula, electrolytic oxidation produces iodine at theanode. The electrolytic solution immediately begins to act as a Karl Fischerreagent and reacts with the water in the sample. At the end of the process,the excess iodine can be detected electrically.

2I- - 2e � I2

According to Faraday's laws, the iodine is produced in proportion to thequantity of electricity. This means that the water content can immediately bedetermined from the Coulombs required for electrolysis. To produce 1 moleof iodine requires 96485 x 2 Coulomb {current (amperes) x time (seconds)}.Since 1 mole of iodine reacts with 1 mole of water, the amount of electricityrequired to cause a reaction with 1mg of water will be as follows.

96485 � 2/18020 = 10.71 Coulombs

This means that if electrolysis takes 1 second with a current of 107mA, theamount of water can be quantified as 10ug. Normally, titration systems soldover the counter carry out electrolysis at 300-400mA. This design allowstitration at the rate of about 30ug per second.

The laws relate to electrolysis. (1) The mass of an electrolyzed substance deposited on an electrode is

proportionate to the amount of electricity.(2) The quantity of a substance deposited by a given amount of

electricity is proportionate to its chemical equivalent weight. Faraday constant = 96485 C/mol

Memo " Faraday's Laws"


17

[Procedures]

a) Electrolyte solutions (Aquamicron AX and CXU) are introduced into theanode and cathode chambers of an electrolysis cell (Figure 3) attachedto an automatic coulometric moisture meter (Figure 2).

b) An electrolytic current is passed through the anolyte as it is stirred in theanode chamber. All water is removed from the electrolysis cell byproducing iodine until the end-point is reached. (It is not necessary at thistime to read the amount titrated.)

c) The sample is then introduced, and the electrolysis process is startedagain.Coulometric titration is continued until the end-point is reached.The end-point is detected electrically by means of a detection circuit builtinto the titration system.

d) Moisture content is automatically calculated from the amount of electricityrequired for electrolysis in the automatic coulometric moisture meter. Theamount of water is expressed in ug units.

Moisture content (ppm) = Measured value (ug)

Quantity of sample (g)

Figure 2: Automatic Coulometric Moisture Meter

Measurement system

Titration bath Electrolysis cell

Sample injection port

Anodechamber

Anode Diaphragm

Cathode

Power sourcefor electrolysis

current

Detectionunit

Control unit

Display

Recording

Catholyte

Drying tube

Cathode chamber

Anolyte

RotorMagnetic stirrer

Detectionelectrode


18

Helpful hint - 2!Are there any criteria to guide the choice between volumetric andcoulometric titration?

The following factors should be taken into account when making thisdecision.

(1) Using the characteristics of coulometric titrationThe need to check titer is eliminated, since it is not necessary tostandardize the Karl Fischer reagent. This feature is very useful forreducing the work involved in everyday analysis tasks.

(2) Moisture content as a criterionCoulometric titration should be used if the moisture content is 1% orlower. It is especially useful for measuring moisture content at the ppmlevel within tolerances of a few ppm. Coulometric titration can still be used if the moisture content is higherthan about 1%, but it is necessary to use small samples, and analysisresults will be influenced by weighing error. Normally volumetric titrationis used in such cases.

(3) Electrode reactions Coulometric titration is not used for substances that react with

(1) Anode chamber (2) Cathode chamber(3) Anode(4) Cathode(5) Diaphragm(6) Rotor(7) Drying tube for anode chamber(8) Drying tube for cathode chamber(9) Stopper(10) Sample injection port(11) Drain cock(12) Detection electrode

(12)

(11)

(10)

(1)

(2)

(7) (8)

(9)

(3)

(4)

(5) (6)

Figure 3: Electrolysis Cell


19

electrodes, such as anilines, diamines and some phenols. Volumetrictitration is carried out using a suitable dehydrated solvent.

(4) Solids that do not dissolve in electrolyteSolids that do not dissolve in organic solvents can reduce currentefficiency by obstructing electrodes and diaphragms. In principle,coulometric titration should be avoided in such cases. Use volumetrictitration with a suitable dehydrated solvent, or the moisture vaporizationmethod.

Q5 What is the moisture vaporization method, and when is itused?

[Outline]

The moisture vaporization method is used to measure samples of solids thatcannot be dissolved in dehydrated solvents or electrolytes, or samples thatinclude interfering substances. The moisture content is vaporized byheating the sample in a flow of dried nitrogen gas. It is then captured in adehydrated solvent or electrolyte and subjected to Karl Fischer titration.Either coulometric or volumetric titration is used. This method is commonly used with natural substances, such as mineralsand rocks, and with macromolecules such as polymers and rubber. Newareas of use include electronic materials, including printed circuit boardsand wafers, and printing materials, such as toners. This method is alsouseful for petroleum products containing additives, such as lubricants. Convenient moisture vaporization systems are available commercially to suitvarious purposes. They can be connected to either volumetric orcoulometric titration systems and used to measure moisture content.


20

[Procedures]

a) Solid samples i) Nitrogen gas (or air) is first passed through a drying tube (filled with

silica gel or phosphorus pentoxide, etc.) and then supplied at a rate ofapproximately 300ml/min. to an oven that is maintained at a suitabletemperature for vaporization.

ii) The sample boat is placed in the heating tube and exposed to the flow ofnitrogen gas to ensure that the heating system is free of moisture.

iii) The sample is immediately placed in the sample boat and inserted intoan oven that is maintained at the required temperature.

iv) The vaporized moisture is absorbed into a dehydrated solvent in atitration flask (or into an electrolyte in an electrolysis cell).

v) The absorbed water is subjected to Karl Fischer titration.

b) Liquid samples, such as lubricating oilsi) Approximately 20ml of a base oil (mineral oil, vacuum pump oil, etc.) is

placed in the heating unit of a moisture vaporization system and heatedto 100-150�C.

ii) The moisture content of the base oil is totally removed by introducing aflow of dried nitrogen gas into the moisture vaporization system at therate of approximately 300ml/min.

iii) 1-10g of the sample is added to the base oil, which is now free ofmoisture.

iv) The vaporized moisture is absorbed into a dehydrated solvent in atitration flask (or into an electrolyte in an electrolysis cell).

v) The absorbed water is subjected to Karl Fischer titration.

Figure 4: A Moisture Vaporization System (for Solid Samples)

Measurement unit

Drying tubeRibbon heater

Oven

Temperature regulationsystem

Carrier gasExhaust vent

Blowing tube

Sample boat

Oven

Thermocouple

Titration flask or electrolysis cell

Titration solvent or anolyteMagnet

Drying tube Carrier gas supply unit

Nitrogen

Flowmeter

Push rodScrew lid

Sample injection port

Heating tube

Measurement system

Detection electrode

Vaporization unit


21

Helpful hint - 3!How can we check for accuracy when a moisture vaporization apparatus isadded to the system?

The accuracy of capture is an important concern, since moisture vaporizedin the moisture vaporization apparatus is carried through the heating tubeand blowing tube by means of dried nitrogen gas before being absorbedinto a dehydrated solvent (or into an electrolyte in an electrolysis cell). Thecapture ratio (recovery ratio) can be checked using the following threemethods.

(1) Using waterWith the water method, which is usually the simplest, 5 or 10ul (5 or10mg) of water is placed directly into the sample boat using amicrosyringe (capacity: 10ul).

(2) Sodium tartrate dihydrate method (theoretical moisture content:15.66%)When using this method, the sodium tartrate dihydrate must first be driedat 105 �C.

(3) Glass capillary pipette methodThe glass capillary pipette method is simple and is suitable for checkingamounts in the order of 1,000ug. Glass capillary pipettes are commonlyused in biotechnology fields, and their capacities are extremely precise.They provide an easy way to obtain a required volume of water bymeans of the capillary phenomenon.

Reference:Bunseki, p587, 1995

Figure 5: A Moisture Vaporization System (for Lubricating Oils)

Electrolysis cell

Titration system

OvenDrying agent (silica gel, etc.)

Flowmeter

Nitrogen gas(300ml/min.)

Temperature regulation system

Moisture vaporization system

22


Q6 What volumetric titration reagents are available? Please explainthe types of reagents and their uses, and the methods employed.

2. Karl Fischer Reagent Products

Mitsubishi Chemical Corporation has a range of products to suit everypurpose. Its products can be broadly divided into the following fourcategories.

Karl Fischer reagents and dehydrated solvents have traditionally beenavailable in both pyridine types and pyridine-free types, which do not havethe pyridine odor. There is no significant difference in performance betweenthe two types, and they can be used interchangeably.

�Mitsubishi Karl Fischer ReagentsTitrantCan be used in various titer according to anticipatedmoisture content

�Mitsubishi Dehydrated Solvents They are suitable as titration solvents for the Karl Fischerreaction, to dissolve or disperse a sample in order to extractwater.

�Mitsubishi Standard Water Methanol This is used to determine the titer of a Karl Fischer reagent.The type used depends on the titer. Water methanol can alsobe used a titration agent for back titration.

�Mitsubishi Standard Liquid This is used to determine the titer of a Karl Fischer reagent.

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Product Purpose Titer Applications Packaging

SS 10mgSamples with high moisture

content (40% or higher)8-12mg/ml

Foodstuffs, CosmeticsDetergents, etc

500ml bottles

SS-Z 3mgSS 3mg

General normalsamples

2.5-3.5mg/mlGeneral samples, Organic

solvents500ml bottles

SS-Z 5mgGeneral normal

samples4.5-5.5mg/ml

General samples, Organicsolvents

500ml, 1Lbottles

SS-Z 1mgSS 1mg

Samples with low moisturecontent (0.1% or lower)

0.7-1.2mg/mlOrganic solvents, Petroleum

products, Gas products 500ml bottles

1. Karl Fischer Reagent SS-Z, SS

Initially the titer of Karl Fischer reagents was unstable, and it was necessaryto use them in the extremely inconvenient form of binary solutions.Mitsubishi Chemical was the first manufacturer in the world to perfect asingle solution version, which it called "Karl Fischer Reagent SS". In the 50years since that time, Mitsubishi Chemical has continued to enhance andexpand its technology, and today enjoys an excellent reputation for itssuperior products.

Mitsubishi Chemical has also developed Karl Fischer Reagent SS-Z, whichis pyridine-free and does not contain chloroform or methyl cellosolve. Userscan choose from an extensive product range, as listed below.

Karl Fischer Reagent SS-Z: Pyridine-Free and Methyl Cellosolve-Free Types

Instead of pyridine, Karl Fischer SS-Z contains a solid amine. As a result,the product is free of the pyridine odor. All the ingredients required toimplement Karl Fischer reactions stoichiometrically are included in a singlesolution. The product is available in either 5mg/ml, 3mg/ml or 1mg/ml titer.

24


[Characteristics]

a) The titer is stable.Even when stored properly under air-tight conditions,Karl Fischer reagents tend to lose titer due to self-reaction. With SS-Z,the titer remains extremely stable and changes at less than 0.05% perday even when stored at room temperature.

b) SS-Z is suitable even for moisture titration of ketones, which have aninterfering effect.SS-Z does not contain methanol, which reacts withketones. The moisture content of ketones can be measured easily byusing SS-Z in combination with the Dehydrated Solvent KTX. (Foraldehydes, use SS in combination with CP or PP Dehydrated Solvent).

c) SS-Z Karl Fischer reagent is available in three titers to suit samples withdifferent moisture contents. The 3mg/ml product is generally regardedas a standard type and should be used first.

KarFischer Reagent SS: Pyridine Type

Karl Fischer Reagent SS is the traditional product containing pyridine. Itsperformance is similar to that of Karl Fischer Reagent SS-Z. It is available ina titer of 10mg/ml, making it suitable for samples with a high moisturecontent.

Mitsubishi Chemical's series of Karl Fischer reagents are supplied in brownglass bottles sealed with lids containing packing. Provided that the bottlesare sealed, they can be stored for long periods with only a minimal declinein titer due to moisture absorption. Once the seal is broken, however,moisture absorption could cause titer to decline unless storage conditionsare optimal. Care should be taken to close caps tightly.

Karl Fischer Reagent SS is a high-titer product and maintains a stable titerover long periods. Depending on the storage environment, however, minuteamounts of sediment may be observed. This has no effect on theeffectiveness of the reagent, which can be still used.

For Your Information

25


Helpful hint - 4!What is the difference between traditional pyridine products and non-pyridine products?

Pyridine-free types use another amine in place of pyridine as the base.Pyridine requires special handling because of its strange odor. Pyridine-freeproducts use a liquid or solid amine with a high boiling point in place ofpyridine. Apart from the base, the composition of pyridine-free types is virtually thesame as traditional products, and safety requirements are identical.Furthermore, it has been confirmed that the performance of pyridine-freetypes is not significantly different from that of traditional types. The speed of the Karl Fischer reaction varies according to the pH of thetitration liquid, the concentration of sulfur dioxide, the type of organicsolvent used, the amount of sample added, and changes in the matrix. It isnot possible to generalize about the relative speeds of traditional andpyridine-free products, which should be considered on a case-by-casebasis.

2. Mitsubishi Dehydrated Solvents

Moisture content measurement using Karl Fischer Reagent SS or SS-Xinvolves the extraction of moisture from a liquid, solid or gaseous sampleinto a dehydrated solvent from which all moisture has been removed,followed by titration. Ideally, titration solvents should have low moisturecontent and contain no impurities. However, it is extremely troublesome andtime-consuming to refine solvents through distillation and dry them beforeeach use. Mitsubishi Chemical has solved this problem by developing arange of dehydrated solvents so that a solvent suitable for each type ofsample will always be available. In terms of applications, dehydrated solvents can be broadly categorizedinto those used to dissolve samples and those used to prevent interferencereactions. These are shown in the following table. Users should select asolvent that is suitable for the samples.

26


(1) Mitsubishi Dehydrated Solvents for Use in Dissolving SpecimensA commonly used titration solvent is methanol, which has a large polarityand considerable capacity to extract water. However, a titration solventto which other solvents have been added is desirable for substancesthat do not readily dissolve in methanol. Mitsubishi Chemical offers arange of blended solvents to suit user requirements. Please choose thetype that is suitable for the characteristics of the sample. With someexceptions, most of the products are blended at 0.2mg/ml or lower.

Principal ingredients Name Use Packaging

Methanol

MethanolChloroformMethanolFormamideMethanolEthylene glycol

GEX (pyridine-free)MSMLOL II (pyridine-free)CMSU (pyridine-free)FMME

General samples

Petroleum productsOils and fatsSugars, proteinsFood additivesGasesInorganic salts

500ml bottles

500ml bottles

500ml bottles

500ml bottles

Dehydrated Solvents GEX and MS

[Uses]

The solvent most commonly used to extract water from samples is methanol.The main ingredients of Dehydrated Solvents GEX and MS is methanol thathas been thoroughly dehydrated. In general, these products can be usedimmediately to measure moisture content. In addition, a reaction acceleratorhas been added to make the reaction between Karl Fischer reagent andwater occur more rapidly than with ordinary methanol. This allowsmeasurements to be taken quickly and with a clear titration end-point.

Organic solvents (n-heptane, cyclohexane, xylene, toluene, benzene, ethylacetate, N,N-dimethylformamide, etc.), inorganic chemicals, pesticides,pharmaceutical products, fertilizers, synthetic detergents, refrigerants,foodstuffs, etc.

27


[Characteristics]

Reference: Muroi, K., Ono, M., Bunseki Kagaku 20, 975 (1971).

a) Minute amounts of water can be measured accurately. b) The reaction between water and the Karl Fischer reagent occurs rapidly.c) The end-point can be readily determined and measured over a short

period of time. d) By first adding salicylic acid, it is possible to measure the moisture

content of amines (strong basicity).

[Applications]

Crude oil, electrical insulating oil, refrigerator oil, diesel oil, naphtha,gasoline, resins, adhesives, pharmaceutical products (caffeine, lecithin,ointments), printing inks, etc.

Dehydrated Solvents OL II and CM

[Characteristics]

Dehydrated Solvents OLII and CM are mixtures of dehydrated chloroformand dehydrated methanol, to which a reaction accelerant has been added.Applications include petroleum-related JIS and ASTM tests. Thesedehydrated solvents are ideal as solvents for petroleum products. They canalso be used to dissolve resins, pharmaceutical products, rubber and othersubstances and can sometimes be used as titration solvents for these items.

a) Petroleum products, resins and adhesives dissolve well in these products. b) The reaction between water and the Karl Fischer reagent occurs faster

than with ordinary solvent mixtures. c) The end-point can be readily determined and measured over a short

period of time.

Dehydrated Solvents SU and FM

In the past the moisture content of sugars and foodstuffs was measuredthrough drying at normal or low pressures. Measurement required longperiods of time with these methods, however, and samples were frequentlyaffected by heat decomposition. These drawbacks meant that the results didnot always reflect the true moisture content. Measurements could not easilybe taken even with the Karl Fischer method, since there was no suitableextraction solvent. Dehydrated Solvents SU and FM developed by Mitsubishi

28


Chemical are mixtures of dehydrated formamide and dehydrated methanol,to which a reaction accelerant has been added. Substances that dissolvewell in the main ingredient, formamide, include casein, glucose, starch andlignin. These solvents are therefore ideal for use in the extraction of moisturefrom sugars and foodstuffs.

[Applications]

Sugars (sugar, drops, caramel, butter sweets, black sugar sweets, maltsyrup, syrup), gelatin (medical capsules, etc.), nucleic acid food additives,pharmaceutical products, dried vegetables, cereals, animal feeds, wool, etc.

[Characteristics]

a) Sugars and protein dissolve well in these products. b) The reaction between water and the Karl Fischer reagent occurs rapidly. c) The end-point can be readily determined and measured over a short

period of time.

Reference: Muroi, K., Tsutsui, C., Koizumi, H., Nihon Shokuhin KogyoGakkaishi 16, 39 (1969).

Dehydrated Solvent ME

The moisture content of gases can be measured indirectly using thephysical or physical-chemical characteristics of water (see Q1), or by meansof the Karl Fischer method, which involves a direct reaction with the water.The Karl Fischer method is the more reliable, since the water is captureddirectly. It is widely used as the standard method and has been included inthe JIS system and other systems. Dehydrated Solvent was created as a moisture capturing solvent for use withgases. It is a mixture of dehydrated methanol and dehydrated ethyleneglycol, to which a reaction accelerant has been added. Moisture content canbe measured easily and accurately by passing a certain amount of gasthrough about 100ml of Dehydrated Solvent ME, followed by immediatetitration using a Karl Fischer reagent. Similar measurements can be obtained with a solvent prepared simply bymixing Dehydrated Solvent GEX or MS with propylene glycol in the ratio of3:1 (by volume).

29


[Applications]

Inorganic gases (hydrogen, nitrogen, oxygen, argon, helium, etc.)hydrocarbons (ethylene, acetylene, propylene, propane, butane, etc.)Vaporization solvent for plastics, minerals, greases, lubricants, etc. Alsoexcellent for use with inorganic salts, which dissolve readily in this product.

Reference: Muroi, K., Ono, M., Sekiyu Gakkaishi [Journal of JapanPetroleum Society] 11 (No. 6), 440 (1968).K. Muroi, Bunseki Kagaku 20, 975 (1971).

[Characteristics]

a) The moisture content in gases can be captured completely, and there isminimal vaporization of the solvent even when large volumes of gas arepassed through it.

b) The reaction between water and the Karl Fischer reagent occurs rapidly. c) The end-point can be readily determined and measured over a short

period of time.

(2) Dehydrated Solvents used to Prevent Interference ReactionsAldehydes or ketones that include active carbonyls cause interferencereactions by reacting with methanol to produce water (see Q8). Toprevent such reactions and measure moisture content accurately, it isnecessary to use a dehydrated solvent designed for use with ketones.The same dehydrated solvent can be used with lower carboxylic acid,which causes a similar reaction. Reactivity varies according to thespecific substance and users should be aware that there are limitationson the size of the samples that can be measured.

Principal ingredients of solvent

Propylene carbonateDiethylene glycol monoethyl ether

Chloroform Propylene carbonate

Pyridine Ethylene glycolPyridine Propylene glycol

KTX(pyridine-free)

CP

PE

PP

Ketones Lower carboxylic acidKetones Lower carboxylic acidSilicone oilsSpecial-purposepaints and varnishesAldehydes

500ml bottles

500ml bottles

500ml bottles

500ml bottles

Name Use Packaging

30


[Applications]

Acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.Propionaldehyde, butyraldehyde, crotonaldehyde, etc.Aniline, cresidine, toluidine, anisidine, etc.Silicone oils

Dehydrated Solvents KTX and CP

[Characteristics]

The method usually employed to measure the moisture content ofsubstances that react with alcohol, such as ketones and silicon oils, involvesthe use of glycolic solvents which show relatively low reactivity, wheregenerally used, at low temperatures. Dehydrated Solvent KTX is a pyridine-free titration solvent produced by mixing dehydrated propylene carbonateand diethylene glycol monoethyl ether. It should always be used inconjunction with Karl Fischer Reagent SS-Z. It cannot be used withaldehydes. The main ingredients of Dehydrated Solvent CP are chloroform andpropylene carbonate. With this blended solvent, the moisture content ofsubstances such as ketones, aldehydes (except acetaldehydes) andsilicone oils can be measured easily at room temperature.

Dehydrated Solvent PE

Dehydrated Solvent PE is a mixture of dehydrated pyridine and dehydratedethylene glycol, to which a reaction accelerator has been added. It is usedat the amount of no more than 15ml of sample to 30ml of PE, accompaniedby direct titration using Karl Fischer Reagent SS. With this product it ispossible to suppress the interference reaction that is caused by ketones andto measure moisture content accurately. The solubility of piridine, which isone of the main ingredients, also allows the product to be used for specialapplications, such as paints.

a) These solvents limit interference reactions with methanol, allowingketones, aldehydes (except acetaldehydes), carboxylic acid, etc., to bemeasured at room temperature.

b) These products can be used with aminobenzene group and areespecially suitable for direct titration of aniline.

c) These products can be used to measure trace moisture in silicone oils.

31


[Applications]

Acetone, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, aceticacid, paints, varnishes, etc.

Dehydrated Solvent PP

Dehydrated Solvent PP is a mixture of dehydrated pyridine and dehydratedpropylene glycol. As a result of work carried out by Mitsubishi Chemical inrelation to active aldehydes, which present the greatest problem in terms ofaccurate measurement of moisture content, it is now possible to suppresstwo interference reactions (see Q9) and achieve precise measurementthrough direct titration with Karl Fischer Reagent SS, simply by adding nomore than approximately 1ml of sample to 25ml of Dehydrated Solvent PP.In the case of acetaldehydes, which are the most active, about 5ml ofsample is added to 25ml Dehydrated Solvent PP. The resulting mixture isthen expelled with dried nitrogen and titrated.

[Characteristics]

a) This solvent allows direct titration of ketones and lower carboxylic acid. b) PE can be used as a titration solvent for paints, varnishes, etc.c) With this product the reaction between water and the Karl Fischer reagent

occurs rapidly. d) The end-point can be readily determined and measured over a short

period of time.

Reference: Muroi, K., Ogawa, K, Bunseki Kagaku 12, 963 (1963).

[Applications]

Acetaldehydes, n-butyraldehyde, iso-butyraldehyde, propionaldehyde,crotonaldehyde, other higher aldehydes

[Characteristics]

This solvent allows direct titration of active aldehydes.

Reference: Muroi, K., Bunseki Kiki 3 (No.11), 40 (1965).

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The titer of Karl Fischer Reagent SS-Z and SS can be standardized usingwater, standard water-methanol, standard water solution and sodium tatratedihydrate. The most commonly used methods are those involving water,standard water-methanol and standard water solution. Standard water-methanol is also used as a titration agent for back titration. The followingthree standard water-methanol and standard water solution products areavailable.

3. Standardization Reagents of Karl Fischer reagents

a) Standard water-methanol must be stored in such a way that it cannotabsorb moisture from the atmosphere.

b) Once the seal is broken the moisture content may change because ofatmospheric humidity. The product should be re-standardized before use as a back titration.

Product Application Packaging

Standard water-methanol2.0mg/ml

Standard water-methanol0.5mg/ml

Aquamicron standardwater 10mg

Standardization of KarlFischer reagents with titerof 3~10mg/ml, reversetitrationStandardization of KarlFischer reagents withpotency of 1mg/mlStandardization of KarlFischer reagents with titerof 1~10mg/ml

250ml bottles

250ml bottles

10-ampoule cases

Helpful hint -5!Why is salicylic acid used to suppress the interference reaction caused byamines with strong basicity (pKa9 or higher)?

Interference reactions are observed when amines with strong basicity (pKa9or higher) undergo direct Karl Fischer titration. Consequences of thesereactions can include unstable end points and higher than normal analyticalreadings. To suppress these reactions, samples are first treated with acidsto reduce the basicity. Traditionally, acetic acid was used, but this tended totrigger a reaction producing esters. Other problems include the fact thatacetic acid itself has a high moisture content. Studies concerning the use ofsalicylic acid yielded promising results and the following advantages wereidentified.

33


a) No esterification reaction during normal titration.b) Since methanol can be used as the titration solvent, Karl Fischer titration

yields good results.c) Salicylic acid has a low moisture content.

The fact that salicylic acid is a solid, is a drawback. However, preparationsimply involves the measurement of about 10g of salicylic acid into a titrationflask and the addition of 50ml of Dehydrated Solvent GEX (or MS), thenstirring until dissolved. Up to 70mmol of amines can be measured with 10gof salicylic acid.

Mitsubishi Chemical Corporation offers a range of coulometric titrationreagents to suit user requirements. These products can be broadlycategorized into the following four types.

Q7 What coulometric titration reagents are there? Please explain thetypes of reagents and their uses, and the methods employed.

�General-purpose electrolytes (two types)These are general-purpose reagents for use with normalsamples.

�Ketone electrolyte (one type)This is used with ketones and lower carboxylic acid, etc.

�Check solution (one type)This product is used for end point checking.

�Standard liquid (two types)This reagent is used to check the moisture meters used incoulometric titration.

Advice to Users

Electrolytes are of two types; anolyte, which is placed in the anode chamberof the electrolysis cell, and catholyte, which is placed in the cathodechamber. Both these products form one pair.

34


Characteristics of the Aquamicron Series

When using the Aquamicron Series of electrolytes it is important tounderstand the following characteristics of the products.

a) Very small quantities of water (about 10ug) can be measuredaccurately.

b) Titration procedures are very simple. c) Measurements can be carried out quickly (1-10 minutes).d) It is not necessary to assess the titer of the reagent.e) The reagent can be used repeatedly.f) The composition of the solvents has been enhanced to make them

suitable for immediate use with various samples. This eliminates thetroublesome task of adding other solvents.

The general-purpose Aquamicron Series of products are ideally constitutedto facilitate Karl Fischer reactions with solvents, including methanol andpropylene carbonate. Sample solubility is excellent, and even trace amountsof moisture can be extracted and titrated coulometrically with ease. Theseproducts also offer superior reagent stability, which is the most importantrequirement when measuring minute amounts of water. This means thatmeasurements can be taken with good reproducibility. The Aquamicron Series is suitable for a wide range of products includingaromatics and other organic solvents, petroleum products, inorganicproducts and gas products. They are also the ideal reagents for the water vaporization method. Aparticularly convenient feature is the fact that they can be used immediatelywithout the need to add other solvents. Aquamicron products have anexcellent reputation for use in day-to-day moisture measurement for plasticsand other solid samples.

1. General-Purpose Electrolytes

Product Packaging

Pyridine-free, chloroform-freeAquamicron AXAquamicron CXU

Pyridine-freeAquamicron ASAquamicron CXU

Anolyte Catholyle

AnolyteCatholyle

500ml glass bottles5ml ampoules (10 per case)


Type

35


Product Type Packaging

Pyridine-free, chloroform-free

Aquamicron AKXAquamicron CXU

AnolyteCatholyle


Ketones are used as industrial solvents and for many other purposes.Specially prepared Aquamicron products that do not contain methanol mustbe used for ketones because they trigger an interference reaction with themethanol in general-purpose Aquamicron products. The same speciallyprepared products are also excellent for use with lower carboxylic acid,which causes an esterification reaction with methanol. Aquamicron products prepared for use with ketones can also be used withusual chemical substances such as alcohols. They should not be used withnon-polar hydrocarbons or halogenated hydrocarbons which have lowpermittivity.

2. Electrolytes for use with Ketones

[Applications]

Acetone, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, siliconoils, acetic acid, dichloroacetic acid, etc.

Reference: Muroi, K., Fujino, H., Sekiyu Gakkaishi [Journal of JapanPetroleum Society] 26, 97 (1983).

36


Moisture Content Packaging

3.8-4.2mgH2O/ml 100ml glass bottles with septum caps

Check Solution P is a solution of organic solvent containing a trace amountof water (approximately 4mg/ml). It is used to adjust the end point ofcoulometric titration by providing surplus water when free iodine is producedin the electrolytes. It can also be used for day-to-day inspections ofcoulometric titration systems. Since methanol is not used as the organicsolvent, this product can also be used with both general-purposeAquamicron products and products prepared for use with ketones.

3. Check Solution P

Aquamicron Water Standard Solution is a water solution containing astandard amount of water. It is used to verify coulometric moisture metersand to determine the titer of KF reagents when used in volumetric moisturemeters. The following products are available.

4. Water Standard Solution

[Method of Use]

A red tinge in the anolyte solution indicates the presence of free iodine.Normally, the measurement of moisture content cannot be initiated. In suchcases, Check Solution P is added to the anolyte as required (until the redtinge disappears) to supply surplus water and turn all of the iodine intoiodide ions. The end point for the anolyte solution can be fine-tuned byadding Check Solution P in 100ul increments until the red tinge disappears.Titration is then started. Check Solution P can also be used for day-to-day verification of moisturemeter. This is done by precisely measuring the moisture content of theCheck Solution P itself.

Product Application Packaging

Aquamicron Water Standard 0.2mg

Aquamicron Water Standard 1mg

Aquamicron Water Standard 10mg

Verification of moisture meters(coulometric titration) Verification of moisture meters(coulometric titration)Determination of titer of KF reagents(volumetric titration)

5ml ampoules (10 per case)



37


3. Applicability of Karl Fischer Titration

Q8 What substances is Karl Fischer titration suitable for?

One of the most useful characteristics of Karl Fischer titration is its extremelywide range of applications.

�Organic compounds: Karl Fischer titration can be used with almost all compounds.

�Inorganic compounds: The scope of application is limited for a number of reasons,including the fact that inorganic compounds are generallydifficult to dissolve in organic solvents and the fact that manyreact with Karl Fischer reagents. For this reason, themeasurement of moisture content in inorganic compounds iscommonly carried out using either the drying method orother procedures. However, the Karl Fischer method isuseful for compounds that contain volatile substances andfor compounds that are amenable to thermal decomposition.

The following are typical compounds that can be measured directly.

1. Organic compounds

(1) HydrocarbonsSaturated hydrocarbons, unsaturated hydrocarbons, aromatichydrocarbons

(2) AlcoholsMonohydric alcohols, polyhydric alcohols, phenols

(3) Ethers(4) Acids

Monobasic acids, polybasic acids, sulfonic acids, hydroxy acids, aminoacids

(5) EstersOrganic acid esters, inorganic acid esters, carbamate esters

(6) Aldehydes Formaldehyde, chloral

(7) Ketones

38


Normal ketones, diisopropyl ketone, benzophenone, benzoin, alizarin,quinalization, dibenzalacetone, camphor, etc.

(8) Acetals RCH(OR')2

(9) Acid anhydrides (RC=O)2O(10) Peroxides

Dialkyl peroxide(11) Nitrogen compounds

Amines (pKa9 or lower)AminoalcoholsAmides RCONH2

Nitriles RCNAzo compounds RN=NR'Imines RCHNR' Cyanhydrine RCH(OH)CNOximes R2C=N'OHLactam NH(CH2)nCOIsocyanide compoundsNitroso compounds R2N-N=O, nitro compounds RN02

Cyanic acid derivatives HOC=NHydroxamic acid RC-NH

O OHAnilides C6H5NHCORPurines, proteins

(12)Halogenated hydrocarbons(13)Halogenated acyls(14)Sulfur compounds

Thioether RSR, disulfides RSSR, thiocyanate compounds RSCN,isothiocyanates RNCS, thioesters RCOSR

2. Inorganic compounds

(1) Organic salts and their hydratesSodium acetate, potassium oxalate, sodium tartrate, Ammonium acetate, barium acetate, lead acetate, ammonium oxalate, etc.

(2) Inorganic salts and their hydratesAlkaline salts of strong acids, sulfates, acidic sulfates, disulphates,dithionates, phosphates (I), phosphates (II)

(3) AcidsSulfur dioxide, hydriodic acid, hydrochloric acid, hydrofluoric acid,nitric acid, sulfuric acid (92% or lower), phosphoric acid

(4) Chelate compoundsCobalt complexes

(5) Polytungsten salts

= -


39

Q9 What is interference in the context of the Karl Fischer titration?Please explain what is meant by interference reactions.

Karl Fischer reagent reacts selectively with water, but its other constituentsmay react with substances other than water. In such cases, titration may failto reach an end point, or an abnormal amount of Karl Fischer reagent maybe consumed, leading to negative or positive errors in the analysis values.This type of phenomenon is called an interference reaction. It is necessaryto be aware of this problem when using Karl Fischer titration.

Interference reactions can be broadly divided into the following two types.

•Reactions with iodine (or iodide ions)•Reactions with other ingredients of Karl Fischer reaction (mainly

methanol, sulfur dioxide)

The following are examples of substances that cause interference, anddescriptions of the reactions that occur.

1. Reactions with iodine (or iodide ions)

The Karl Fischer method is a form of non-aqueous oxidation-reductiontitration. Since the reaction betwen Karl Fischer reagent and water is a kindof iodometry, it is subject to interference by substances that trigger anoxidation-reduction reaction with iodine and iodide ions. Samples containingsubstances that react with iodine and iodide ions will therefore producepositive errors in measurements, while those that contain iodine producedthrough the oxidation of hydriodic acid, which is a reactive substance, willproduce a negative error.

(1) Substances that consume iodine (reduction reaction) andcause a positive error

These are substances that react directly with free iodine in the Karl Fischerreagent. Because they consume iodine, they have the same effect as water,which means that the analysis results will be correspondingly higher.

1.1 Organic compounds (a) Thiol (mercaptan), thiourea and their nitrogen substitutes

2RSH+I2 � RSSR+2HI(b) Hydrazine hydrochloride

Hydrazine hydrochloride reacts on a mole by mole basiswith iodine.

(c) Thio acid


40

2RCSSH+I2 � RCSSSSCR+2HI(d) Vinyl ether and 2,3-dihydofurane, dihydroprane

ROCH=CH2+I2+R'OH � ROCH(OR')CH2I+HI(e) Ascorbic acid (Vitamin C)(f) Amines and aminoalcohols (pKa9 or higher)

These consume iodine gradually.

1.2 Inorganic compounds (a) Ammonia

This reacts with iodine to produce nitrogen iodideNH3+3I2 � NI3+3HI

(b) Hydroxylamines 2NH2OH+3I2+2SO2+2CH3OH � 6HI+2HSO4CH3+N2

(c) Ferric chlorideIron(III) salt causes the following reaction, with the resultthat only 5.5 molecules of water are titrated.

FeCl3 � 6H2O+5.5I2+6SO2+6CH3OH �FeI2+9HI+3HCl+6HSO4CH3

(d) Metal oxidesManganese dioxide, ferric oxide and lead dioxide react withKarl Fischer reagent. However, the reaction is notquantitatively constant, since these substances do notdissolve readily in the reagent.

MnO2+I2+2SO2+2CH3OH � MnI2+2HSO4CH3

However, interference does not occur with hydrogenperoxide, sodium peroxide, barium peroxide, pottasiumpersulfate or ammonium persulfate, since these substancesreact selectively with sulfur dioxide.

H2O2+SO2 � H2SO4

Na2O2+SO2 � Na2SO4

(e) Weak acids and oxidesBoric acid, metaboric acid, boron oxide and arsenic trioxideall react with Karl Fischer reagent.

H3BO3+3I2+3SO2+6CH3OH � 6HI+3HSO4CH3+B(OCH3)HBO2+2I2+2SO2+5CH3OH � 4HI+2HSO4CH3+B(OCH3)As2O3+3I2+3SO2+3CH3OH � 2AsI3+3HSO4CH3

(f) Salts In general, the weakly acidic salts of alkaline metals reactwith Karl Fischer reagent in the same way as oxides.Carbonates, bicarbonates, sulfites and pyrosulfites react inapproximately constant amounts.

K2CO3+I2+SO2+CH3OH � 2KI+CO2+HSO4CH3

KHCO3+I2+SO2+CH3OH � KI+HI+SO2+HSO4CH3

Na2SO3+I2+CH3OH � 2NaI+HSO4CH3


41

Na2S2O5+I2+CH3OH � 2NaI+SO2+HSO4CH3

Sodium tetraborate (Na2B4O7) and sodium metaarsenitereact in approximately the same quantities as shown in (d). The following are examples of salts that cause non-quantitative reactions with Karl Fischer reagent, and saltsfor which the reaction mechanism is not fully understood.

Na2CrO4 � H2O, Mg(NH4)2(CrO4)2 � 6H2O, (NH4)2Cr2O7, Na2S �

9H2O, 20MoO3 � 2H3PO4 � 48H2O, ZrOCl2 � 8H2O, ZrO(NO3) �

2H2O, Al2O(OOCCH3)2 � 4H2O(g) Reducing agents

When strong reducing agents are titrated, the amount ofmoisture will be higher. Stannous chloride and sodiumthiosulfate react with Karl Fischer in approximately constantquantities.

SnCl2 � 2H2O+3I2+2SO2+2CH3OH �SnI4+2HCl+2HI+2HSO4CH3

2Na2S2O3 � 5H2O+11I2+10SO2+10CH3OH �2NaI+Na2S4O6+20HI+10HSO4CH3

Sodium sulfide also reacts with iodine. Na2S+I2 � 2NaI+S

(2) Substances that produce iodine (oxidation reactions) and cause anegative error

(2.1) Organic compounds (a) Dichloroisocyanuric acid

Iodine is freed through the oxidation of hydriodic acid.(b) Quinone

Iodine is freed through the oxidation of hydriodic acid.(c) Peroxy acid

Iodine is freed through the oxidation of hydriodic acid.RC(O)OOH+2HI � I2+H2O+CH3COOH

(d) Peroxides (diasyl)Iodine is freed through the oxidation of hydriodic acid

(C6H5COO)2+2HI � I2+2C6H5COOH

(2.2) Inorganic compounds (a) Chlorine

Iodine is freed through the oxidation of hydriodic acidCl2+2HI � I2+2HCl

(b) Oxidizing agents Moisture content appears lower when strong oxidizing aremeasured.


42

(3) Substances that react with hydriodic acid and produce water Metal oxides and hydroxides.Oxides and hydroxides of alkaline metals and alkaline earth metals reactin approximately constant quantities with the hydriodic acid in KarlFischer reagent.

MO+2HI � MI2+H2OM(OH)2+2HI � MI2+2H2ONaOH+HI � NaI+H2OCaO+HI � CaI2+H2Oe.g. MgO, ZnO, Ag2O, HgO, Cu2O, LiOH, KOH, Ba(OH)2, etc.

However, weakly acidic oxides react much less. Substances that do not react at all include Al2O3, CuO, NiOand PbO.

Oxides that react in constant amounts dissolve completely in the KarlFischer at the titration end point, but Ni and Al compounds do notdissolve.

2. Other Substances that react with ingredients of KarlFischer Reagents

If methanol is used as the solvent for Karl Fischer reagent and the titrationsolvent, the following interference reactions will occur. In the case ofaldehydes, there will be interference resulting from reactions with both sulfurdioxide and water.

(1) Carbonyl compounds The following reactions with alcohol cause interference by producingwater, leading to high analysis results. Frequently, the end point willnever be reached.

R2CO+2ROH � R2C(OR)2+H2ORCHO+2ROH � RCH(OR)2+H2O

In addition to these reactions, aldehydes also capture water through thefollowing interference reaction. This results in low analysis results.

C6H5N � SO2+RCHO+H2O � C6H5NHSO3CH(OH)R

(2) Lower carboxylic acids and their derivativesFormic acid, acetic acid, monochloroacetic acid and dichloroacetic acidtrigger an esterification reaction with methanol at room temperature (20�C) or higher. This reaction causes interference by gradually producingwater.

CH3COOH+CH3OH � CH3COOCH3+H2OFormic acid in particular is not suitable for Karl Fischer titration.


43

(3) Silanol and silanol derivativesIf methanol is present during Karl Fischer titration, the silanol in siliconoils will trigger the following interference reaction.

R3SiOH+I2+SO2+2CH3OH �R3SiOCH3+2HI+CH3SO4H

The countermeasures used to suppress interference depend on the type ofinterference reaction.

�Basically, Karl Fischer titration cannot be used with substances thatcause oxidation/reduction reactions. Special preliminary processesmust therefore be used to convert these substances into othersubstances before titration.

�Where substances react with methanol, Karl Fischer titration is carriedout under conditions that do not involve the use of methanol. With Karl Fischer Reagent SS-Z and SS, methanol is not used as thesolvent, so it is possible to measure the water content in carbonylcompounds and other substances simply by using the reagent inconjunction with a dehydrated solvent formulated for use withketones. These expanded range of uses greatly enhances the valueof these products.

�In the case of interference substances that do not change whenheated, it is possible to carry out Karl Fischer titration by using a watervaporization system.

�With substances that have strong basicity, such as amines, it ispossible to use Karl Fischer titration if the substances are firstneutralized by adding acid.

Q10 Please outline any methods that can be used to suppressinterference reactions so that Karl Fischer titration can be employed.

Specific examples are shown in the following tables. Individual researchersshould optimize their approaches on the basis of these examples.


44

1. Substances requiring special treatment

Compound Treatment

AmmoniaFerric saltsHydrazine derivativesHydroxylamine saltsThiol (mercaptan)Sulfuric acid

Thio acidThiourea

Add acetic acid.Add 8-Hydroxyquinoline.Add acetic acid.Add sulfur dioxide:pyridine solution (1:1).Prevent interference by adding olefins (octene, etc.).If the sulfuric acid is 92% pure or higher, add a largesurplus of pyridine and titrate it as a salt.Prevent interference by adding olefins (octene, etc.).Prevent interference by adding olefins (octene, etc.).

2. Using Karl Fischer reagents with interference substances

With ketones, aldehydes, lower carboxylic acid and amines with strongbasicity, titration should be carried out using the Karl Fischer reagent inconjunction with the reagents shown below.

Substance

Ketones

Aldehydes

Low-gradecarboxylic acid

Strong-base amines(pKa9 and above)

Karl Fischer Reagent SS-Z

Karl Fischer Reagent SS





Karl FischerReagent SS-ZKarl FischerReagent SS

Dehydrated Solvent KTX

Dehydrated Solvent CP


Dehydrated Solvent CPDehydrated Solvent PP



Dehydrated Solvent GEX+ salicylic acidDehydrated Solvent MS+ salicylic acid

Aquamicron AKXAquamicron CXU

Aquamicron AKXAquamicron CXU(suitable only forcertain aromaticaldehydes)Aquamicron AKXAquamicronCXU

Aquamicron AX+ salicylic acidAquamicron CXU

Reagent UsedVolumetric titration Coulometric titration

Note:Do not use Karl Fischer SS with Dehydrated Solvent KTX.


45

Measuring Moisture Content of Strong-Base Amines

Put 10g of salicylic acid into a titration flask (electrolysis cell).Add 50ml of Dehydrated Solvent GEX or MS (100ml in the caseof Aquamicron AX) and mix together. Add the sample (amine)after dehydrating it with Karl Fischer reagent. Then initiate KarlFischer titration. The amount of sample that can be measuredwill vary according to the type of amine.

4. Procedures for Karl Fischer Titration

Q11 How should we actually carry out volumetric titration?Please describe the preparations and procedures involved.

To measure moisture content by means of volumetric titration, you will firstneed to prepare the following items.

�Titration agent: Karl Fischer Reagent SS-Z (or SS)(It is necessary to assess the titer before use.)

�Titration solvent: Select the dehydrated solvent to suit the samples.�A Karl Fischer volumetric titration system

(Reagents manufactured by Mitsubishi Chemical can be used withany commercially available system.)

Next, the amount of the sample is determined according to the anticipatedmoisture content. In general, one of the following three methods of titration are used. Theprocedures for each are explained below. (1) Direct titration(2) Back titration (3) Water vaporization

1. Sample Size

It is important to determine the size of the sample according to the moisturecontent. If there is excessive moisture, Karl Fischer reagent will be wasted,and if there is too little, there will be significant effect on titration error andthe results will lack precision. The following table can be used as a guidewhen determining the appropriate amount of sample in relation toanticipated moisture content. The figures shown here assume that the KarlFischer reagent has a titer of 3mg/ml. If the titer is different, it will benecessary to adjust the figures accordingly.


46

2. Direct titration (standard method)

This is the standard and most commonly used method of volumetric titration.The sample is dissolved in a dehydrated solvent and titrated with KarlFischer reagent. Titration is carried out in a sealed system isolated from theatmosphere.

3. Back Titration

In the case of solid samples that cannot readily be dissolved in dehydratedsolvents, moisture is extracted by stirring for a specific period. An excess ofKarl Fischer reagent is then added and the sample is left for a specificperiod to allow the moisture to react thoroughly with the reagent. The excessKarl Fischer reagent is then subjected to back titration using standardwater/methanol solution.

Anticipated moisture content (%) Amount of Sample (g)

0.1 or lower0.1-0.50.5-11-55-10

10-5050 or higher

10-2052

0.50.30.1

0.03

[Procedures]

a) Place 25-50ml of dehydrated solvent in a thoroughly dried flask. b) Titrate the Karl Fischer reagent SS-Z to the end point to remove all

moisture.(This procedure is known as "pre-titration". It is not necessary toread the titration volume at this stage.)

c) Measure out the sample (A, g) according to the anticipated moisturecontent and immediately place it in a titration flask.

d) Titrate to the end point (B, ml) using Karl Fischer SS-Z for which the titer(F, mg/ml) is known, stirring continuously.

e) Calculate the moisture content (W, %) according to the following formula. B x F

W = x 100 A x 1000


47

[Procedures]

a) All moisture is removed from the dehydrated solvent using the proceduresdescribed in the previous section.

b) The sample (A', g) is immediately placed in a titration flask. c) A specific amount (C, ml) of excess Karl Fischer reagent SS-Z (titer

F'mg/ml) is then added and the sample is stirred for the required period oftime.

d) The sample is then titrated to the end point (D, ml) using a standardwater/methanol solution (titer f, mg/mg).

e) Moisture content (W', %) is calculated according to the following formula. (C x F')-(D x f )

W' = x 100A' x 1000

[Procedures]

a) An oven is maintained at a temperature suitable for vaporizing themoisture content of the sample. Nitrogen gas, which has previously beenpassed through a drying tube, is passed through the moisturevaporization system at the rate of approximately 300ml/min.

b) The titration system is dehydrated by means of pre-titration in the titrationsystem in a flow of nitrogen gas.

c) The sample is then quickly transferred to a sample boat and placed in anoven that has been maintained at the required temperature.

d) The vaporized water is absorbed into a dehydrated solvent (GEX, MS orME).

e) Karl Fischer titration is then carried out according to the direct titrationmethod.

4. Moisture Vaporization Method

The moisture vaporization method is used with solid samples that do notreadily dissolve in dehydrated solvents, or for samples that causeinterference reactions. Moisture vaporization is carried out using acommercially available moisture vaporization system in combination with avolumetric titration system.

Note:Dehydrated solvent GEX or MS should be used in a mixtureconsisting of one part of propylene glycol to three parts ofdehydrated solvent by volume.


48

(1) Using pure waterThis method is the most accurate, since the standard for determining titer iswater itself. The drawback with this method is the difficulty of measuringsmall amounts of water accurately. A microsyringe is used for conveying thewater. It is convenient to use a commercially available dropping bottle with asmall dripping pipette. Each drop from the pipette is 20-30mg.

5. Determining Titer

The titer of the Karl Fischer reagent SS-Z (or SS) that is placed in the titrationsystem must always be determined before use. Karl Fischer reagent SS-Z(or SS) is very stable and needs to be tested only once a week, providedthat the bottle is kept airtight. Where particularly high accuracy is required,titer should be checked daily. Titer can be determined using one of thefollowing four methods.

�Using pure water�Using standard water solution�Using standard water/methanol solution�Using sodium tartrate dihydrate

The characteristics of these methods and the procedures for using them aredescribed below.

[Procedures]

The amount of water obtained should be 10-30mg. The procedures are thesame as for direct titration. The following calculation formula is used.

F=S/TWhere F: Titer (mgH2O/ml)

S: Amount of water obtained (mg)T: Amount of Karl Fischer reagent required for titration (ml)

(2) Using standard water solutionWith this method, a standard water solution with a guaranteed value is usedin place of water. Where the value of the standard water solution is around10mg/g, approximately 1g is obtained. The following calculation formula isused.

F=S x K/TWhere F: Titer (mgH2O/ml)

S: Amount of standard water solution obtained (g)K: Guaranteed value of standard water solution (mgH2O/g)T: Amount of Karl Fischer reagent required for titration (ml)


49

(3) Using standard water/methanol solutionStandard water/methanol solution is a standard water solution for which themoisture content has been accurately determined. It is especially suitablefor determining the titer of Karl Fischer Reagent SS-Z (or SS). The moisturecontent is shown in the label (e.g. 2.02mgH2O/ml).

[Procedures]

a) 25-50ml of dehydrated solvent GEX (or MS) is placed in a titration flask. b) Karl Fischer Reagent SS-Z (or SS) is titrated to the end point to remove all

moisture content. (It is not necessary to read the titration value at thisstage.)

c) 5-10ml of standard water/methanol solution is taken and added to thedehydrated solvent in the titration flask.

d) The Karl Fischer Reagent SS-Z (or SS) that is to be assessed is titrated. e) Titer is calculated from the titration volume according to the following

formula.

F=A x f/BWhere F: Titer of Karl Fischer Reagent SS-Z (or SS) (mgH2O/ml)

A: Amount of standard water/methanol solution obtained (ml)f : Titer of standard water/methanol solution (mgH2O/ml)B: Amount of Karl Fischer Reagent SS-Z (or SS) titrated (ml)

Note:Standard water/methanol solution has the same expansioncoefficient as methanol. If it is used at a temperature that issignificantly different from the assessment temperature shownon the label (20�C), it will be necessary to correct the volume(ml) of standard water/methanol solution used.

(4) Using sodium tartrate dihydrateSodium tartrate dihydrate is the most stable of the hydrate standardsubstances in relation to changes in atmospheric humidity. It has atheoretical moisture content of 15.66%. The low solubility of commerciallyavailable sodium tartrate dihydrate means that large amounts cannot beobtained. The amount for 50ml of methanol would be about 200mg or less.Users should be aware that the crystal size of commercially availableproducts may vary. If the crystals are too small they may scatter whenadded, leading to errors.


50

[Procedures]

The amount of sodium tartrate dihydrate obtained should be around 150mg.The procedures are the same as for direct titration. The following calculation formula is used.

F=m x 0.1566/VWhere F: Titer (mgH2O/ml)

m: Amount of sodium tartrate dihydrate obtained (mg)V: Amount of Karl Fischer reagent required for titration (ml)

Helpful hint -6!Why does a solution that reached the titration end point change color if it isleft standing?

If a solution is left standing for a period after it has reached the titration endpoint, it will turn yellow and will start to consume Karl Fischer reagent again.Conversely, it may turn the reddish brown color associated with over-titration.This phenomenon results from contamination by external moisture, and fromthe free iodine from the iodide in the solution through the action of ultravioletrays and oxygen.


51

Q12 How can we actually measure moisture content using coulometrictitration? Please describe the preparations and procedures involved.

To measure moisture content by means of coulometric titration, you will firstneed to prepare the following items.

�Electrolytes: Aquamicron seriesTo ensure proper functioning, it is essential to use the correctanolyte-catholyte combination.

�A Karl Fischer coulometric titration system(Aquamicron series products manufactured by MitsubishiChemicals can be used with most commercially availablesystems.)

Next, the size of the sample is determined according to the anticipatedmoisture content. There are actually two coulometric titration methods.

(1) Direct titration (2) Moisture vaporization 1. Sampling amounts Coulometric titration is suitable for the measurement of trace quantities ofmoisture. Sample size is an important consideration as excessive quantitieswill extend the time required for analysis. Normally a sample containing 0.1-5mg of water is used. The guidelines inthe following table assume that the appropriate moisture content range forcoulometric titration is 1% or lower. This is not to say that coulometrictitration cannot be used for samples with a moisture content above 1%. Insuch cases, however, the need to obtain samples in extremely smallquantities will increase measurement errors, leading to problems withaccuracy. If possible, volumetric titration should be used in such cases.

2. Obtaining a Sample A carefully dried syringe (1-10ml) should be used. First, flush the syringe 2-3times with the sample substance. Next, the amount required for the sampleshould be taken. A piece of silicon rubber should be attached to the end ofthe syringe needle, and the syringe should then be weighed precisely. The silicon rubber should then be removed, and the sample inserted into the

Anticipated moisture content (%) Sample quantity (g)

0-0.050.05-0.10.1-0.20.2-0.50.5-2.0

5-1021

0.50.1


52

3. Combination of Aquamicron Products

4. Direct TitrationThis method is suitable for liquid, solid or gaseous substance that can bedissolved in Aquamicron. Direct titration should not be used for insolublesolid samples since these may clog the membranes or affect the efficiencyof the current.

system. The rubber should then be replaced, and the syringe weighedagain. The difference in weights should be equal to the weight of thesample.

General use With ketones

Anolyte

Catholyte

Aquamicron AKX

Aquamicron CXU

Aquamicron AX or Aquamicron ASAquamicron CXU

[Procedures]

a) Approximately 100ml of anolyte (Aquamicron AX, AS or AKX) is placed inan electrolyte cell (Figure 3) that has been carefully dried.

b) The entire contents of a catholyte ampoule (Aquamicron CXU, 5ml) isplaced in the catholyte chamber.

c) An electrolytic current is applied to the anode-cathode while it is stirred toproduce iodine and trigger the Karl Fischer reaction in order to remove allwater from the electrolysis cell. (It is not necessary to read the moisturecontent at this stage.)

d) The sample is introduced into the electrolysis cell and coulometric titrationis then carried out until the end point.

e) Moisture content is calculated according to the following formula. W1=M/S

or W2=M x 100/(Sx106)Where W1: Moisture content (ppm)

W2: Moisture content (%)M: Measurement value (µgH2O)S: Amount of sample (g)


53

5. Moisture VaporizationWith this method, the coulometric titration system is used in conjunction witha moisture vaporization system. Approximately 150ml of anolyte(Aquamicron AX or AS) is placed in an electrolysis cell. Two ampoules(10ml) of catholyte (Aquamicron CXU) are used. The condition for moisture vaporization should be optimized for theparticular sample. Detailed instructions for various types of samples areprovided later in this manual.

Figure 6: Sampling Syringe

Silicon rubber

Anolyte chamber

Catholyte chamber

Electrolysis cell

Figure 7: Sample Injection System


54

Q13 Sampling procedures are one of the most important aspects of moisture contentmeasurement. What are the specific methods and equipment involved?

At a room temperature of 25�C with 50% humidity, the moisture content ofthe atmosphere is 0.01mg per 1ml. Depending on the procedures used,moisture (humidity) may infiltrate the electrolysis cell (or titration flask),adhere to the equipment used to obtain samples, or adhere to or dissolve inthe sample. It is important to be aware of this possibility as it can lead toerror. It is also essential to vary sample quantities in accordance with individualcharacteristics and moisture content. It is convenient to use commerciallyavailable sampling equipment of the types shown in Figures 9-17. These aredesigned to allow samples to be varied according to the particularcircumstances. The procedures for using this equipment are describedbelow.

1. Liquid SamplesEquipment used with liquid samples includes micro-syringes, syringes,pipettes and dropper bottles. (1) Micro-syringesMicro-syringes are used to obtain specific amounts of water, substanceswith a high moisture content, or check solutions for coulometric titration.Products are available commercially with capacities of 10, 25, 50 and 100ul.The needle should be as long as possible. Most commercial products have50mm needles. The following precautions should be taken when usingmicro-syringes. a) Where possible, avoid using the full stroke of the micro-syringe when

measuring the sample. We recommend using 2/3 or less of the stroke.(This is because the plunger could be contaminated by atmosphericmoisture.)

b) Dry the micro-syringe thoroughly. After the micro-syringe has beenwashed with an organic solvent (methanol, etc.) with a low boiling point, itshould be thoroughly dried in a flow of dried nitrogen, etc., and thenplaced in a drier.

c) Flush the micro-syringe 2-3 times with the sample. d) When adding the sample, push the plunger down quickly to ensure that

no sample remains on the tip of the needle. Sometimes samples are tested by weight using the same procedures aswith syringes. The weight of the sample normally should be determined frommeasurements of volume and relative gravity (or density).


55

(2) SyringesThese are used for most liquid samples. Glass syringes are most commonlyused, however plastic products (disposable) are also convenient. The mostcommonly used commercial products are 1, 2, 5 and 10ml syringes. Generalprocedures for using syringes are described below. a) After carefully drying the syringe (figure 6), flush it two or three times with

small amounts of the sample. Then draw in the required amount of thesample.

b) Attach a piece of silicon rubber to the needle and weigh the syringe. c) Remove the silicon rubber and insert the syringe needle through the

stopper attached to the side valve of the titration cell (Figure 8). Inject thesample.

d) Pull out the syringe needle and weigh it accurately with the piece ofsilicon rubber attached to the needle.

e) The difference between the two weights is the weight of the sample.

Figure 8: Stopper

Cap nut

Silicon washer

Common fitting

(3) Pipettes Because a stopper cannot be used with a pipette, the side stopper (orsample injection stopper) must be removed. With the stopper removed theexperiment is exposed to the air and the results must be corrected for theinfiltration by atmospheric moisture by conducting a blank test for the sameperiod of time that the flask was open. The method is unsuitable, therefore,for the coulometric titration used to measure trace amounts of moisture. The weight of the sample is determined by separate measurement of therelative gravity (or density). We recommend the use of syringes whereverpossible.

(4) Dropper bottleDropper bottle (Figure 9) are used for water or for samples with a highmoisture content. They are especially convenient for measuring water whendetermining the titer of Karl Fischer Reagent SS-Z (or SS) using water. Withcommercially available products, the pipettes produce droplets of about30mg each.


56

[Procedures]

a) After carefully drying the dropper bottle, introduce the sample. Attach thepipette and extract the sample.

b) Accurately weigh all the equipment. c) Remove the pipette from the dropper bottle and titrate the titration solvent. d) Replace the pipette on the dropper bottle and weigh the equipment

accurately. e) The difference between the two weights is the weight of the sample.

(5) Dropper bottle (for high-viscosity substances)This equipment (Figure 10) is used for samples with the viscosity of treacle.Procedures are the same as in (4) above.

2. Solid Samples

The appropriate method must be selected with reference to the varyingcharacteristics and forms of solid samples. There are commercial productsthat are suitable for each method and it is convenient to use these. As the sample insertion aperture on the titration flask must be opened toinsert the sample, a blank test must be carried out to adjust for the timewhile the flask is open. In general, the following procedures are used. a) Obtain the required amount of sample using a thoroughly dried sampling

bottle. b) Accurately weigh the sampling bottle.c) Remove the stopper of the sample insertion aperture on the titration flask

and quickly insert the sample. d) Close the stopper and record the time that stopper was open. (The lid

should be opened for exactly the same period of time during the blanktest.)

e) Weigh the sampling bottle.

Figure 9: Dropper bottleFigure 10: Dropper bottle

(for high-viscosity substances)


57

(1) Upright solid sampling bottleAn upright solid sampling bottle (Figure 11) is used for ordinarypowdered, granular or lumpy samples. This type of sampling bottle isused frequently.

(2) Angled solid sampling bottleA drawback with upright sampling bottles is that the sample must beshaken to some extent to make it drop to the bottom. The angled bottlesolves this problem by means of a half-rotational bend that allows thesample to fall (Figures 12, 13). The angled-neck bottle is especiallysuitable for plastic pellets.

(3) Trace solid sampling bottle This container (Figure 14) is used to obtain extremely small amounts ofsamples with a high moisture content. It is suitable for powderedsamples.

(4) Syringe-type sampling bottle The syringe-type sampling bottle (Figure 15) is used for consolidatedpowders and viscous solids. The sample is drawn into the syringe bypulling out the plunger, and then expelled the contents into the system bypushing in the plunger.

(5) Sampling bottle for semi-solidsThis container (Figure 16) is used for high-viscosity samples, such asgreases. The sample is first taken onto the sampling spoon (A), which isthen weighed together with the bottle (B). Next, the sample is insertedinto the titration flask together with the sampling spoon. The spoon isstirred for a period to allow the sample to dissolve. On completion of themeasurement the sampling spoon is returned to the sampling bottle,which is then weighed. The difference between the two weights is theweight of the sample.

Figure 11:Upright Sampling Bottle

Figure 12:Angled Sampling Bottle

Figure 13:Angled-neck Sampling Bottle


58

3. Liquefied Gas Samples A dual-aperture pressurized sampling bottle and stainless steel pipes areused. Commercial products are available to suit specific purposes andthese are recommended. The key requirement for sampling is to ensure that the liquid phase isintroduced into the dehydrating solvent (or electrolyte). Errors may result ifonly the gaseous phase is introduced. Also, the entire amount of samplemust be added. The general procedures are summarized below.

a) Position the gas bottle upright or at an angle. b) Connect a pipe between the gas bottle and the sampling bottle. c) Introduce the liquid phase into the sampling bottle. d) Keep the amount of the sample to 80% or less of the vessel's capacity

and determine the weight.

Figure 14: Trace Sampling Bottle

Figure 15: Syringe-Type Sampling Bottle

Figure 17: A Typical Sampling Bottle

Extension pipe

Injection needle

Figure 16:Semi-Solid Sampling Bottle

Sample


59

5. Official Testing Methods and Documentation

Q14 Karl Fischer titration is classed as an official testingmethod. What Japanese standards have been adopted?

Karl Fischer Reagent SS-Z (or SS), dehydrating solvent, and the Aquamicronseries of products all conform with Japanese standards and can be usedwith confidence.

1. Japanese Industrial Standards (JIS)

C2101 Testing methods for electrical insulating oils.K0068 Test methods for water content of chemical products K0113 General rules for methods of potentiometric, amperometric,

coulometric, and Karl-Fischer titrations K1422 Carbon tetrachloride K0068,K0113K1424 Ammonium nitrate K0068K1508 Trichloroethylene K0068,K0113

JIS Name of Standard Cited Standards

Electrolysis cell Figure 18: Example of an Injection Assembly

Aquamicron AX

Aquamicron CXU

Gas vent


60

K1521 Perchloroethylene K0068,K0113K1522 Isopropyl alcohol K4101K1527 Ethylene glycol K4101K1530 Propylene glycol K4101K1557 Testing method of polyether for polyurethane K0068K2211 Refrigerating machine oils K2275K2220 Lubricating grease K2275K2234 Engine antifreeze coolants K0068K2242 Heat treating oils K3362K2275 Crude oil and petroleum products

- Determination of water content K0113K2436 Naphthalene, anthracene, carbazole K0068,K0113K2437 Phenols K0068,K0113K2438 Pyridine bases K0068,K0113K3351 Glycerines for industrial use K0068K3362 Testing methods for synthetic detergent K0068K4101 General testing methods for organic intermediates K0113K4108 Nitrobenzenes K0113K4109 Aminobenzenes K0113K4112 N-Substituted anilines K0113K4127 Benzoic acid K0113K4129 Naphthol K0113K4132 1-Naphthylamine K0113K4137 Anisidine K0113K4148 Dinitrobenzenes K0113K4153 Diphenylamine K0113K4156 Nitrophenols K0113K4809 Analytical methods of explosives K6724 Vinyl AcetateK6759 Testing methods for acrylonitrileK6910 Testing methods for phenolic resinsM8001 General testing methods for reagent chemicals M8211 Iron ores-Method for determination of combined water content K0113K8231 Method for determination of combined water

in manganese ores


61

2. Japan Pharmaceutical Codex (Revision 14)

Item Tolerance (sample amount)

General Test Method 27: Moisture Content Test (Karl Fischer Method)The items listed in the Pharmaceutical Codex that stipulate the use ofmoisture content testing by means of Karl Fischer reagent are as follows.

Aspirin aluminum 4.0% (0.15g)Aminophylline 7.9% (0.3g)Isopropanol 0.7%w/v (2ml)Quinine ethylcarbonate 3.0% (0.5g)Ethosuximide 0.5% (2g)Suxamethonium chloride 8.0-10.0% (0.4g)Suxamethonium chloride for injection 10.0% (0.4g)Berberine chloride 15.6% (0.3g)Benzalkonium chloride 15.0% Thiamine hydrochloride 5.0% (0.5g)Anhydrous citric acid 0.5% (2g)Clofibrate 0.2% (5g)Cyclophosphamide 5.5-7.0% (0.5g)Distigumine bromide 1.0% (1g)Dextromethorphan hydrobromide 4.0-5.5% (0.2g, back titration)Isosorbide dinitrate 1.5% (0.3g)Hydroxyzine pamoate 3.0% (1g)Potassium guaiacolsulfonate 3.0-4.5% (0.3g)Metothrexate 12.0% (0.2g, special method)Mercaptopurin 10.0-12.0% (0.2g, back titration)Folic acid 8.5% (0.2g, special method)Riboflavin sodium phosphate 10.0% (0.1g, back titration)Protirelin tartrate 4.5% (0.2g)Terbutaline sulfate 0.5% (1g)Chlorobutanol 6.0% (0.2g)


62

3. Notes to Official Food Additive List (7th ed., 1999)

Item Tolerance

General Test Method 17: Moisture Content Test (Karl Fischer Method)The Karl Fischer method is stipulated for the following food additives.

Sorbitan sesquioleate 0.5% (1g)Propylene glycol 0.5% (2g)Polysorbate 80 3.0% (1g, back titration)Sodium lauryl sulfate 5.0% (0.5g)Polyvinyl pyrrolidone K25 5.0% (1.0g)Polyvinyl pyrrolidone K30 5.0% (1.0g)Polyvinyl pyrrolidone K90 5.0% (1.0g)Macrogol 400 1.0% (2g)Macrogol 1500 1.0% (2g)Macrogol 4000 1.0% (2g)Macrogol 6000 1.0% (2g)Berberine tannate 6.0% (0.7g)

5'-Inosinic acid sodium salt 29.0% or lower (0.15g, back titration)5'-Uridine acid sodium salt 26.0% or lower (0.15g, back titration)Citric acid (anhydrous) 0.5% or lower (2g)Disodium glycyrrhizate 13.0% or lower (0.2g, back titration)5'-Cytidine acid sodium salt 26.0% or lower (0.15g, back titration)Sucrose fatty acid ester 4.0% or lower (back titration)Sodium dehyroacetate 8.3-10.0% or lower (0.3g, back titration)Folic acid 8.5% or lower (0.2g, back titration)5'-Calcium ribonucleotide 23.0% or lower (0.15g, back titration)5'-Sodium ribonucleotide 27.0% or lower (0.15g, back titration)

4. Japan Petroleum Institute Standards

Test for water in liquid petroleum products (Karl Fischer Method)JPI-5S-14-76


63

5. Japan LPG Association Standards

Moisture Content Test Method in LPG: Karl Fischer MethodJLPGA-S-02-99

6. Japan Agricultural Standards (JAS)

Vegetable Oils (Karl Fischer Method, moisture content 0.2% or lower) (1969)

Q15 Please provide some examples of the international standards (ISO) and foreignstandards that have been adopted for the Karl Fischer titration method.

Listed below are some examples of standards established by theInternational Organization for Standardization (ISO) and the AmericanSociety For Testing and Materials. The BS (U.K.) and DIN (Germany)systems are also based on these standards.

1. General Testing Methods (1) Volumetric titration

ISO 760-1978Determination of water - Karl Fischer method (General method)

ASTM E203-01Water using Karl Fischer reagent

(2) Coulometric titration ASTM E1064-92

Water in organic liquids by coulometric Karl Fischer titration

2. Individual StandardsASTM D1364-95

Water in volatile solvents (Fischer reagent titration method)ASTM D1533-96

Water in insulating liquids (Karl Fischer reaction method)ASTM D1631-94

Water in phenol and related materials by the iodine reagent methodASTM D1744-92

Water in liquid petroleum products by Karl Fischer reagentASTM D3277-95

Moisture content of oil-impregnated cellulosic insulationASTM D3466-85

Water content of trichlorotrifluoroethane


64

ASTM D3621-84Water in acetate esters

ASTM D4017-96Water in paint and paint materials by Karl Fischer method

ASTM D4377-93Water in crude oils (Karl Fischer) titration

ASTM E700-79Water in gases using Karl Fischer reagent

ISO 2097: 1972Glycerols for industrial use - Determination of water content - KarlFischer method

ISO 2514: 1974Acetaldehyde for industrial use - Determination of water content - KarlFischer method

ISO 2596: 1994Iron ores - Determination of hygroscopic moisture in analyticalsamples - Gravimetric and Karl Fischer methods

ISO 2753: 1973Urea for industrial use - Determination of water content - Karl Fischermethod

ISO 3699: 1976Anhydrous hydrogen fluoride for industrial use - Determination ofwater content - Karl Fischer method

ISO 4317: 1991Surface-active agents and detergents - Determination of water content- Karl Fischer method

ISO 5381: 1983Starch hydrolysis products - Determination of water content - KarlFischer method

ISO 5791: 1978Ammonium nitrate for industrial use - Determination of water content -Karl Fischer method

ISO 6191: 1981Light olefins for industrial use - Determination of traces of water - KarlFischer method

ISO 7105: 1985Liquefied anhydrous ammonia for industrial use - Determination ofwater content - Karl Fischer method

ISO 7335: 1987Iron ores - Determination of combined water content - Karl Fischermethod

ISO 10101-1-3: 1993Natural gas - Determination of water by the Karl Fischer method -

Part 1: Introduction


65

Part 2: Titration procedure Part 3: Coulometric titration

ISO 10362-2: 1994Cigarettes - Determination of water in smoke condensates - part 2:Karl Fischer method

ISO 11817: 1994Roasted ground coffee - Determination of moisture content - KarlFischer method

Q16 What reference works are there concerning Karl Fischermeasurement methods?

The following is a list of basic references concerning Karl Fischer titration. Itconsists mainly of works written by members of the Mitsubishi ChemicalCorporation research team.

1. Mitchell & Smith: Aquametry, 2nd Edition, Part 3 (1980).

2. Funasaka, W., Muroi, M., Suibun no Teiryo [Measuring Moisture Content]II: Karl Fischer Method (out of print).Bunseki Raiburari 14 [Analysis Library 14], published by Tokyo KagakuDojin(1969).

3. General IntroductionsMuroi, K., "Karu Fissha Ho ni Yoru Suibun no Sokuteiho" [MeasuringMoisture Content Using the Karl Fischer Method] (in Keisoku Gijutsu[Measurement Technology], 3, 49, 1977).Muroi, K., "Bunseki Kagaku ni Okeru Mizu" [Water in Chemical Analysis],(in Bunseki [Analysis] 2, 74, 1979).

4. Papers Concerning Pyridine-Free TypesKato, H., Ono, M., Kuwata, S.:

(1) "New Karl Fischer Volumetric Reagent Composed of a Base" (in BunsekiKagaku 35, 91, 1986).

(2) "Determination of Moisutre by Karl Fischer Coulometric ReagentComposed of New Bases" (in Bunseki Kagaku 33, 638, 1984).

(3) "Determination of Moisture in Ketones and Lower Carboxylic Acids byNew Karl Fischer Coulometric Reagent"(in Bunseki Kagaku 34, 147,1985).


66

(4) "Determination of Moisture in Amines by New Karl Fischer CoulometricTitration"(in Bunseki Kagaku 34, 805, 1985).

ISO: The International Organization for Standardization (ISO) wasestablished to promote the discussion and adoption of globalstandards with a view to facilitating the international exchangeof goods and services and to developing cooperation in thespheres of intellectual, scientific, technological and economicactivity. Formally established in 1947, ISO has its headquartersin Geneva, Switzerland. JIS is currently reviewing its standardswith the aim of making them compatible with these internationalstandards.

ASTM: The American Society For Testing Materials (ASTM) is anAmerican organization dedicated to science and technology. Itwas formed in 1898 to standardize specifications and testmethods, etc., for industrial materials. It has publishednumerous ASTM standards which include testing methods.

BS: British Standards (BS) are standards established by the BritishStandards Institution, which was founded in 1901.

DIN: Industrie Normen (DIN) are standards established by theDeutsches Institut fur Normung, which was renamed in 1975 tomatch the name of the standards.

Memo "Outline of official testing methods in other countries"


67

6. Important Information about Handling and Using Karl Fischer Reagents

Q17 Are there any safety requirements or other precautionsthat should be followed when using Karl Fischer reagents?

1. Safety and Hygiene Requirements 1) Never drink the reagent or inhale it's vapor. 2) Avoid skin contact. If the reagent does come in contact with the skin,

wash it off with soap, etc., and rinse well with water. 3) If reagent splashes into an eye, flush the eye immediately with water, for

at least 15 minutes. The eye should be checked by an eye specialist. 4) Make sure that the room is adequately ventilated when handling Karl

Fischer reagents. 5) Keep the reagents away from naked flames. 6) Observe general rules for handling reagents, including the following.

Organic Solvent Poisoning Prevention RegulationsInjury Prevention Rules For Specified Chemical Substances, etc.Poisonous and Deleterious Substances Control LawFire Prevention Law (hazardous substances)

The regulations vary according to the specific type of reagent. Fordetailed information, contact the Mitsubishi Chemical Corporation.

2. Handling Requirements(1) General Requirements a) Sampling bottles and other equipment must be dried thoroughly before

use. During testing, take care to prevent contamination by atmosphericmoisture. The following paper includes detailed information about theprevention of moisture contamination.

Muroi, M., "Measuring Trace Moisture Content Using the KarlFischer Method - With Particular Emphasis on the Influence ofAtmospheric Moisture and the Prevention Thereof" (in BunsekiKagaku 12, 858, 1963)

b) Check to find out if the sample will cause an interference reaction. If thesample is one where the interference reaction can be prevented, take theappropriate steps to do so.

In addition to handling requirements related to the characteristics of KarlFischer reagents, there are precautions to be taken in relation to safety andhygiene. It is important to fully understand both sets of requirements.


68

(2) Volumetric Reagents a) Refer to the relevant sections for information about points that require

particular care during volumetric titration, such as changes over time inthe titer of Karl Fischer Reagent SS-Z (or SS), the titer of standard water-methanol and the evaluation procedures.

b) Avoid the following combination when using volumetric reagents;� Karl Fischer Reagent SS and Dehydrating Solvent KTX� Karl Fischer Reagent SS-Z and Dehydrating Solvent CP

(3) Coulometric Titration a) The analytical capabil ity of Aquamicron AX and AS anolytes is

approximately 800-1,000mgH2O per 100ml of anolyte. However, if asample is added in stages so that the total amount exceeds 150ml, thesample will have an effect that causes a gradual decline in currentefficiency. This may lead to inaccurate results. In such cases, discard allthe reagent and begin again with fresh reagent.

b) The analytical capability of Aquamicron CXU catholyte is approximately130-150mgH2O per 5ml of catholyte. With prolonged use, however, thereagent will gradually turn light brown and then dark brown. If the colorbegins to change, the reagent should be completely removed, with apipette, etc., and replaced with fresh reagent. Do not add fresh reagent todiscolored reagent.

c) Store Karl Fischer reagents at or below room temperature and in alocation that is not exposed to the light. Seal bottles to prevent theabsorption of moisture.

Chapter II: Applications - 1

69



70


71


This section is a summary of technical knowledge accumulated byMitsubishi Chemical Corporation over many years. This information isincluded as a guide for those actually using Karl Fischer titration to measurethe moisture content of individual compounds. There are specific examplesfor both organic and inorganic compounds.

II-1. Organic Compounds

Karl Fischer titration is the ideal method for measuring the moisture contentof organic compounds. With very few exceptions, it is suitable for almost allcompounds. Measurement is straightforward, as organic compounds cangenerally be dissolved in the solvents used with Karl Fischer reagents. The section of Basic Knowledge gave an overview of the range ofapplications, grouped into those that can be measured directly, those thatcause interference but which can be measured after modification, and thosethat cause interference. Refer to the relevant parts of the manual foressential information on the reactive functional groups that causeinterference. In the Section on Applications, we will describe specific Karl Fischer titrationmethods for individual compounds, together with examples that illustrate keyfactors to be taken into account when actually using these methods. Ofcourse, it is impossible to cover every type of substance, so users shouldrefer to the examples for similar compounds when establishing theconditions for moisture measurements.

Some of the examples refer to earlier reagent products.The latest products are those named as the "reagents touse". There may be exceptional cases in whichmeasurements cannot be carried out as shown in thetables. Users should choose the most appropriate type ofreagent and measurement method.

Important!


72

1. Hydrocarbons

Hydrocarbons can be measured readily using standard procedures.Both volumetric and coulometric titration can be used. Moisture contenttends to be very low, however, because of the low water solubility ofhydrocarbons and because of their low water absorption capacity. Forthis reason, coulometric titration is suitable. In the case of volumetric titration, standard dehydrated solvents areused. Solubility may be inadequate with long-chain hydrocarbons, butmoisture content can be measured through dispersal extraction aftersufficient stirring. Dehydrated solvents formulated for use with oils canbe used to enhance solubility with good effect. Substances with low moisture content can be measured accuratelyusing Karl Fischer Reagent SS-Z (or SS) with a low titer. With coulometric titration, the sample is added directly to the electrolytesolution (anolyte). Measurement is carried out after dissolution ordispersal. In the case of olefins, double bonding may cause interference. usingthe electrolyte solution (anolyte), the interference can be lowered.

Key Points

Examples of substances that can be measured directly:

Ethylene, propylene, butadiene, propane, butane (see the discussion onindustrial LPG in Chapter III: Applications 2, III-1). Pentane, 2,4-dimethyl pentane, 2,2-methyl pentane, 2,2,4-trimethyl pentane,octane, 3-methylhexane, decane, octadecane, 2-pentene, dipentene, 1,3-pentadiene, isooctane, cyclopentane, methyl cyclopentane, cyclohexane,methyl cyclohexane, cyclohexene, benzene, toluene, xylene, ethyl benzene,mesitylene, styrene, naphthalene, diphenyl, decalin, hexamethyl benzene,anthracene, phenanthrene


73

[Examples of Measurement](1) Volumetric titration

Reagents used: Karl Fischer Reagent SS-Z (or SS)General-use Dehydrated Solvent GEX (or MS) 25-50ml

(2) Coulometric titration Reagents used: Aquamicron AX (or AS) 100ml

Aquamicron CXU 5ml

Substance Dehydratedsolvent

Samplequantity (g)

Measurementvalue (mg)

Moisturecontent (ppm)

n-HexaneBenzeneTolueneXylene

Substance Sample quantity(g)

Measurement value(µg)

Moisture content(ppm)

n-Pentanen-HexaneIsooctanen-Decanen-DodecaneLigroinCyclohexene1-Hexene1-Decene1-TetradeceneBenzeneTolueneXyleneNaphthalene

2.57751.88283.46002.04802.10482.13152.23350.76000.74751.54602.52972.51512.49301.7755

4837895463

12469543021

334380174129

19202626305831714014

132151

7073

General-use

"""

6.58708.72068.55114.3511

0.250.780.450.72

388953

165

All liquid samples can be measured continuously up to 20-50ml, usingapproximately the same amounts as shown in the table.

It is convenient to use a syringe-type sampling bottle fornaphthalene. Refer to JIS K2436 for details of the test method.

Note:


74

2. Halogenated Hydrocarbons

The behavior of halogenated hydrocarbons is similar to that ofhydrocarbons. Measurements can be carried out using standardprocedures without problems. Both volumetric and coulometric titration can be used, but coulometrictitration is recommended because of the minute amounts of moistureincluded in these substances. In the case of volumetric titration, standard dehydrated solvents areused. Halogenated hydrocarbons dissolve well in methanol, butsolubil i ty may become inadequate if the substance is addedcontinuously. With sufficient stirring, however, it will be possible toextract and measure the moisture content. An effective way ofenhancing solubility is to use dehydrated solvents formulated for usewith oils. Substances with low moisture content can be measured accuratelyusing Karl Fischer Reagent SS-Z (or SS) with a low titer. For coulometric titration, the sample is added directly to the electrolytesolution (anolyte). Measurement is carried out after dissolution ordispersal. There is no interference, even in the case of substances such as vinylchloride, with double bonding. Direct titration can be used in the sameway. Because of the processes used in their production, halogenatedhydrocarbons sometimes contain trace amounts of free chlorine. Thiscauses interference through the oxidation of iodide ions to produce freeiodine. As a result, the moisture measured will be reduced in proportionto the amount of free iodine. This can be prevented by usingDehydrated Solvent MS as the titration solvent, and by agitating thesolution thoroughly before the Karl Fischer titration, to render the freechlorine inactive. This is because of the reaction between amine andsulfur dioxide in the dehydrated solvent, as shown in the followingformula.

Cl2+SO2+2CH3OH+2C5H5N �C5H5N•HCl+C5H5N•HSO4CH3+CH3Cl

Key Points

Muroi, M., Bunseki Kagaku 16, 1061 (1967)"Determination of Water in Subtances Containing ActiveChlorine by Karl Fischer Titration"

Reference:


75


Methyl chloride, vinyl chloride, methylene chloride, methylene iodide,chloroform, carbon tetrachloride, iodoform, ethyl iodide, ethylene bromide,ethylidene bromide, 6-chloropropylene, 1,4-dichloro-2-butene,bromobenzene, iodobenzene,chloronaphthalene, bromonaphthalene



(2) Coulometric titrationReagents used: Aquamicron AX (or AS) 100ml

Aquamicron CXU 5ml


Samplequantity (g)



ChloroformCarbon Tetrachloride1,2-Dichloroethane1,1,2-TrichloroethaneChlorobenzene




Methylene chlorideEthylene chlorideChloroform1,1,1-Trichloroethane1,1,2,2-TetrachloroethaneCarbon tetrachlorideChlorobenzeneMethylene bromideEthylene bromideBromoform1-Bromotetradecane1-BromohexadecaneTetrabromoethaneMethyl iodideEthy iodideHexadecyl bromide

3.74453.51934.17213.71467.93004.45593.10382.46602.21252.65182.04001.02552.90792.31041.93921.0067

62244332380

3553101207715202

1747168

52478476337

50

177080

102430

2267

29091

6597551

164206174

50

General-use

"""

14.499915.78256.160514.077610.9400

1.600.491.480.740.71

11031

2405365


76

3. Alcohols

The moisture content of alcohols can be measured easily using directtitration. End-points are stable and highly accurate analytical results areattainable. Both volumetric and coulometric titration can be used. In the case of volumetric titration, the sample is dissolved in a general-use dehydrated solvent and titrated. Alcohols dissolve very well in thistype of solvent and there should not be any problems. Solubility may beinadequate with higher alcohols (such as stearyl alcohol). In such casesit is appropriate to use dehydrated solvents formulated for use with oils. Propargyl alcohol interferes with the titration by reacting with the KarlFischer reagent. For coulometric titration, the sample is dissolved in the electrolytesolution (anolyte). Titration will be prolonged if samples have a highmoisture content (2% or above). We recommend either the reduction ofthe sample quantity, or the use of volumetric titration.

Key Points


-Monohydric alcohols-Methanol, ethanol, isopropanol, alkyl alcohol, n-, iso-, tert-butanol, isoamylalcohol, 2-methyl-4-butanol, 2,4-dimethyl-3-pentanol, decanol, dodecanol,octadecanol, geraniol, citronellol, cyclohexanol, borneol, terpinenol, benzylalcohol, cholesterol-Polyhydric alcohols-Ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerine, 1,4-butanediol,1,4-butenediol, 2-methyl-1, 3-propanediol, diethylene glycol, pentaerythritol,D-mannitol, D-sorbitol


77




Aquamicron CXU 5ml


Samplequantity (g)



MethanolEthanoln-ButanolEthylene glycolPropylene glycolDiphenyl carbinol




Ethanoln-Propanoli-Propanoli-Butanoltert-Butanoln-Amyl alcoholBenzyl alcoholEthylene glycolPropylene glycolEthylene glycol monoethyl ether2-Ethyl hexanolUndecanolGlycerin

2.19362.24882.22442.23612.18294.12002.95113.15362.93812.67770.83100.82400.7572

30261291

590104313153024

280539

1212639282

63930

1379574265467602722

95171412239339

761228

General-use

"""""

3.82402.21023.92105.50025.17260.5953

0.433.330.490.460.780.33

1121507

12584

151554

Samples can be measured continuously up to 20-50ml usingapproximately the same quantities as those shown in the table.

Samples can be measured continuously up to 20-50ml usingapproximately the same quantities as those shown in the table.


78

4. Ethers

The moisture content of ethers can be measured readily using directtitration. End-points are stable and highly accurate analytical results areobtainable. The behavior of ethers is similar to that of hydrocarbons.Both volumetric and coulometric titration can be used.With volumetric titration, the sample is dissolved in a general-usedehydrated solvent and measured. Solubility may be inadequate withethers that have a high carbon number. In such cases we recommendthe use of dehydrated solvents formulated for use with oils. In the ether group, the following compounds need special care: Substances that have double bonding and cause interference - Vinylether (Note 1) For coulometric titration, add the sample to the electrolyte solution(anolyte) and take the measurement. With most ethers, measurementcan be carried out without difficulty. With propylene oxide, however,there is a limit to the quantity of sample that can be added (Note 2).

Key Points


Dimethyl ether, diethyl ether, isopropyl ether, ethylene oxide, tetramethyleneoxide, methyl carbitol, diethylene glycol, ethylene glycol dimethyl ether,diphenyl ether, dioxane, tetrahydrofuran




Samplequantity (g)


�-ButyrolactamDioxaneTetrahydrofuranPropylene oxideEthyl vinyl ethern-Butyl vinyl ether2,3-Dihydrofuran

General-use

""""""

5.63644.96182.45484.34720.18330.16570.2647

209228

1206711

3200600

2400

1.181.132.963.090.590.100.65



79


Aquamicron CXU 5ml




Isopropyl etherEthylene glycol monoethyl etherDiethylene glycol Monoethyl etherDiethylene glycol Ethyl etherDioxaneTetrahydrofuran�-Butyrolactam2-Methyl tetrahydrofuranPropylene oxide

2.06132.71752.82984.51302.90900.82783.12564.32901.7117

430653

10943961120923507944

1217

208240387878

411115

162218711

Vinyl ether causes interference by reacting with the Karl Fischerreagent to produce iodoacetal in accordance with the followingformula.

ROCH=CH2+I2+R'OH � ROCH(OR')CH2I+HIThe same type of interference occurs with 2,3-dihydrofuran anddihydropyran. Corrected titration method: Add a small amount of the sample (0.5g or less) to 50ml ofDehydrated Solvent CP and titrate this with Karl Fischerreagent. If the amount added is greater than 0.5g, aninterference reaction will gradually occur.

Note 1:


80

It proved possible to add propylene oxide in three amounts of1.7g (total: 5.1g). Thereafter the analytical readings rose untilfinally, an end point was not reached. With volumetric titration, it proved possible to add 50g andmeasure this directly without any problems.

Note 2:

5. Phenols

With most phenols the moisture content can be measured directly. As ageneral rule there are no limitations with volumetric titration, but it isimportant to be aware that limitations do exist in the case of coulometrictitration. With volumetric titration, the sample is dissolved in a general-usedehydrated solvent in the same way as for alcohols, before undergoingKarl Fischer titration. Solubility is not a problem.Aminophenols cannot be measured in methanol because ofinterference reactions. Measurements can be taken, however, by usinga titration solvent prepared by adding salicylic acid to DehydratedSolvent MS (see "12. Amines"). The size of the sample used in suchcases should not exceed 2g. In the case of coulometric titration, anodic oxidation produces aprecipitate that adheres to the anode. The resulting contamination ofthe electrode precludes normal electrode performance and reduces theefficiency of the current. An end point cannot be reached withhydroquinone and aminophenols. This kind of interference is commonwith coulometric titration, and care should be taken when using themethod. In tests carried out by Mitsubishi Chemical Corporation,however, measurements have proved possible under controlledconditions, as follows. To 100ml of Aquamicron AX, a) approximately 1g of phenol is added to begin with. b) The total cumulative quantity added is approximately 5g. If there is

too much phenol the efficiency of the current will decline andgradually lead to higher analytical values.

Key Points


81


Phenol, catechol, resorcinol, pyrogallol, guaiacol, picric acid, o-cresol, p-cresol, 5-methyl resorcinol, eugenol, p-tert-butyl catechol, �-naphthol, ß-naphthol




Aquamicron CXU 5ml


Samplequantity (g)


Moisturecontent (%)

Phenolm-Cresol


Measurement value(µg) Moisture content

Phenolm-Cresolo-Cresol2,6-Xylenol

1.89062.03190.60421.4616

1241242

30481737

656ppm119ppm0.504%0.119%

General-use

"

1.91392.6048

1.941.92

0.1010.074


82

6. Ketones

If the Karl Fischer reagent and the titration solvent contain methanol,ketones react with the methanol (ketal bonding) as shown in thefollowing formula. As it produces water this causes an interferencereaction.

R2CO+2CH3OH � R2C(OCH3)2+H2OThis may increase the time needed to reach the end point, or may meanthat it is never reached. Excessively high moisture readings are amongother phenomena that can adversely affect accuracy and precision.However, Karl Fischer titration can be carried out if the followingcounteracting steps are taken. a) Use a Karl Fischer reagent and titration solvent that do not contain

methanol. b) The degree of interference varies according to the type of ketone

compound.Determine the size of the sample to use with reference tothe specific type of compound.

In general, acetone and cyclohexanone show the strongest reactivityamong the aliphatic ketone compounds and reactivity decreases inproportion to the carbon number. Aromatic ketone compounds arereported to be less reactive than the aliphatics. Either volumetric orcoulometric titration can be used with these ketones, but a reagentformulated for ketones should be chosen. Karl Fischer Reagent SS-Z (or SS) is used for volumetric titration. Itcontains absolutely no methanol and can be used safely with ketones.Use Dehydrated Solvent KTX (or CP), which is formulated for ketones. For coulometric titration, use a combination of Aquamicron AKX/CXU.

Key Points

(1)Reference: Muroi, M, et al., J. Japan Petrol. Inst.,26, 97(1983)."Determination of Water in Ketones and Silicone Oilsby Karl Fischer Titration Method"

(2) Kato, H.: "Determination of Moisture in Ketones and LowerCarboxylic Acids by New Karl Fischer Coulometric Reagent"(in Bunseki Kagaku 34, 147, 1984).

Reference:


83

Dehydrated Solvent KTX should be used in combination withKarl Fischer Reagent SS-Z, and Dehydrated Solvents CP andPP with Karl Fischer Reagent SS.

Note:


The following inactive carbonyl compounds can be added to methanol(Dehydration Solvent GEX, MS) and measured directly.Di-isopropyl ketone, camphor, benzophenone, deoxybenzoin, benzyl,benzoin, alizarin, quinalizarin, ninhydrin

For other substances, use a ketone-type reagent.


Reagents used: Karl Fischer Reagent SS-Z (or SS)Ketone-type Dehydrated Solvent KTX (or CP, PP) 25-50ml


Samplequantity (g)


Moisturecontent (%)

AcetoneAcetylacetoneMethyl ethyl ketoneMethyl isobutyl ketoneCyclohexanoneAcetophenoneFurfuralDiacetone alcohol

Ketone-type

"""""""

1.46161.83272.24902.27790.88392.05620.57991.8455

3.311.461.130.440.803.585.943.33

0.230.0800.0500.0190.0900.171.020.18

A feature of Dehydrated Solvents KTX and CP is that they can be used totake measurements at normal temperatures. This is particularly convenientas interference can be suppressed and measurements made withoutregulating the reaction temperature. Dehydrated Solvent KTX must always be used with a pyridine-free KarlFischer Reagent SS-Z. A normal end point will not be achieved if KarlFischer Reagent SS is used. In general, the interference state of ketones is ascertained through thecontinuous addition of reagent. When the analytical reading begins toappear abnormally high, it should be assumed that interference has begun.Beyond that point, analytical readings must be discarded.


84

(2) Coulometric titration Reagents used: Aquamicron AKX 100ml

Aquamicron CXU 5ml



MoistureContent(%)

Measurable amount (ml)

AcetoneMethyl ethyl ketoneMethyl isobutyl ketoneAcetylacetoneAcetophenoneCyclopentanoneCyclohexanoneDiacetone alcohol2-Methoxy-2-methyl-4 -pentanone

0.39540.41410.80100.97600.54510.49550.31170.96021.8963

907464102683215

1090635217

81

0.2290.112

127ppm0.700

394ppm0.2200.204

226ppm043ppm

1015151515

5

2

It is important to be aware of patterns of blank current (also described as"background" or "drift" current) in the moisture meter. If a gradual rise in theblank current causes the end point to fluctuate, it will not be possible toobtain accurate analytical results. In such cases the electrolyte must bereplaced.


85

7. Aldehydes

If the Karl Fischer reagent and the titration solvent contain methanol,aldehydes react with the methanol (acetal bonding) as shown in thefollowing formula. As it produces water, this causes an interferencereaction.

RCHO+2CH3OH � RCH(OCH3)2+H2OThis may cause end point fluctuation, or may mean that the end point isnever reached. Other phenomena include excessively high moisturereadings. As shown in the following formula, aldehydes may also react with aningredient in the Karl Fischer reagent (sulfur dioxide), causing aninterference reaction that consumes water (bisulfite addition) andreduces the moisture content reading.

C5H5NSO2+RCHO+H2O � C5H5NHSO3CH(OH)RFurthermore, since aldehydes are more reactive than ketones, thereaction speed will vary considerably according to the specificaldehyde involved. Because of these complex problems it is verydifficult to obtain accurate analytical readings for aldehydes. In general, Karl Fischer titration can be carried out if the followingcounteracting steps are taken. a) Use a Karl Fischer reagent and titration solvent that do not contain

methanol. b) Keep the size of the sample used for titration to a minimum to

suppress the reaction that consumes water. c) Acetaldehydes are highly reactive and must be titrated under special

conditions.These are described later in this manual. With coulometric titration, sulfur dioxide in the electrolytic solutioncauses interference that leads to low moisture readings. Although anend point may be reached the analytical reading is unlikely to beaccurate and using this method is difficult. In practice, this methodshould never be used with acetaldehydes.

Key Points

Muroi, K, et al., Bull. Chem. Soc. Japan, 38,1176 (1965). "The Determination of the Water Content in Acetaldehyde byMeans of Karl Fische Reagent"

Reference:


86

Dehydrated Solvent KTX should be used in combination withKarl Fischer Reagent SS-Z, and Dehydrated Solvent CP withKarl Fischer Reagent SS.

Note:


The following inactive carbonyl compounds can be dissolved in a general-use dehydrated solvent and measured directly.

Formaldehyde, chloral

However, these substances tend to react with methanol at room temperature(above 25�C) and we recommend a titration method whereby the sample isdissolved in a ketone-type dehydrated solvent.


Reagents used:Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent KTX (or CP) 25-50ml

Substance Dehydratedsolvents

SampleQuantity (g)

MeasurementValue (mg)

MoistureContent (%)

n-ButyraldehydeIsobutyraldehydeCrotonaldehydePropionaldehydeFormalinChloral hydrate

Ketone-type

"""

General-use

"

0.40200.39520.42390.20140.03280.1752

3.560.960.677.3617.4219.27

0.8860.2430.1583.6553.111.0

Measuring moisture content in acetaldehydes

Given the intensity of the interference reaction that occurs withacetaldehydes, Dehydrated Solvent PP should be used as it contains nopyridine-sulfur dioxide. The following guidelines should apply. If the acetaldehyde has a high moisture content, 0.2ml samples can bemeasured. If the moisture content is less than about 0.2%, however, thesample will be too small and this method cannot be used. Accordingly,when measuring trace amounts of moisture, 5-10ml of sample should beadded to 5ml of Dehydrated Solvent PP in the apparatus shown in thediagram. The sample should be vaporized using dried nitrogen during thetitration.


87

1) Sampling Attach a piece of silicon rubber to the needle of a carefully dried syringe(capacity: 5-10ml, needle length: approx. 10cm). Place the syringe in a drypolyethylene bag and store it in a refrigerator. Remove the thoroughly chilledsyringe from the refrigerator, together with a sample container (fitted with ametal sampling stopper) that has also been stored in the refrigerator. Insertthe needle of the syringe into the metal stopper and extract some of thesample. Flush the syringe twice with the sample. On the third occasion,extract 5-10ml of sample.

2) Titration Pour 5ml of Dehydrated Solvent PP into a titration flask (capacity: approx.50ml), as shown in the diagram. Place the flask in a water bath at atemperature of 20-25 �C. Add dried nitrogen to the titration flask through athree-way cock (E) at a rate of approximately 0.9l/min. Titrate with KarlFischer Reagent SS until the end point is reached. Stop the agitation of theDehydrated Solvent PP and the nitrogen flow. Insert the syringe through oneof the holes in the three-way valve (E) until the tip of the needle reaches thesurface of the Dehydrated Solvent PP. Inject the sample immediately. Startthe agitation of the Dehydrated Solvent PP and the nitrogen flow. At thesame time, titrate to the end point, using Karl Fischer Reagent SS to drive offthe vaporized acetaldehyde.

A: 50ml titration flaskB: Water bathC: Magnetic stirrerD: Platinum electrodeE: Three-way valveF: Nitrogen drying tube

(phosphorus pentaoxide)G: Karl Fischer Reagent SSH: Standard water/methanol

buret I: Drying tubeJ: Nitrogen ventK: Sampling point

Figure 19: Acetaldehyde Moisture Titration System


88

(2) Coulometric titration Reagents used: Aquamicron AKX 100ml

Aquamicron CXU 5ml



Moisture Content(%)

BenzaldehydeSalicylaldehyde3-PhenylpropionaldehydeChloral hydrate

0.52050.62570.54350.0441

343751

14674916

660ppm0.1200.27011.1

No Sample amount(ml)

Measurement(ml)

Measurement(mg)(mg) (%)

12345

1357

10

0.140.410.651.061.32

0.421.231.953.173.95

0.0530.0520.0500.0500.050

Examples:

Titer of Karl Fischer reagent: 3.00mg/mlNote:


89

8. Organic Acids

With most organic acids, moisture content can be measured directlyand easily. If a dehydrated solvent with methanol as its main ingredientis used, however, interference will occur as the result of an esterificationreaction between methanol and lower carboxylic acids such as formicacid, acetic acid and adipic acid. These reactions produce water andwill be evidenced by a delayed end point or an unusually highanalytical result. Esterification reactions vary, depending on the individual acid. Formicacid shows a strong esterification reaction and will react very quicklywith methanol. Reactivity lessens as the carbon number increases.Normally, during volumetric titration, propionic acid will not triggerinterference attributable to an esterification reaction. Aromaticcarboxylic acid is another substance that does not cause interferencerelated to esterification. Interference can also result from a reaction with iodine. Formic acidappears to be affected by the oxidation of iodine and L-ascorbic acidreacts quantitatively with Karl Fischer reagent.For volumetric titration, a ketone-type dehydrated solvent is used withlower carboxylic acids. A general-use dehydrated solvent can be usedwith higher carboxylic acids and aromatic carboxylic acid. If problemsare encountered with the methanol solubility of substances with highcarbon numbers, a dehydrated solvent formulated for oils (such asstearic acid) should be used. For measurements based on coulometric titration, a ketone-type ofanolyte is used with the lower carboxylic acids. Coulometric titrationcannot be used for formic acid, however, as an end point cannot bereached. A general-use electrolyte can be used with higher carboxylicacids and aromatic carboxylic acid.

Key Points


Acetic acid, mono-, di-, trichloroacetic acid, trifluoroacetic acid, propionicacid, acrylic acid, methacrylic acid, trimethylacetic acid, caproic acid,stearic acid, oleic acid, linolenic acid, cyclohexane carboxylic acid,cyclohexyl acetic acid, camphoric acid, abietic acid, 3,5-dinitrobenzoicacid, cinnamic acid, anisic acid, benzilic acid, 2,4-dichlorophenoxy aceticacid, benzoic acid


90

Polybasic acidsOxalic acid, malonic acid, maleic acid, succinic acid, diglycolic acid, adipicacid, sebacic acid, nitrilotriacetic acid, phthalic acid, terephthalic acid

Sulfonic acids Benzenesulfonic acid, toluenesulfonic acid, xylenesulfonic acid,naphthalenesulfonic acid, sulfanilic acid

Hydroxy acidsGlycolic acid, � -hydroxybutyric acid, citr ic acid, tartaric acid, � -hydroxycaproic acid, �-hydroxyadipic acid, �,�-dihydroxyadipic acid,ricinoleic acid, salicylic acid

Amino acidsGlycine, leucine, sarcosine, valine, aspartic acid, iminodiacetic acid,creatine, asparagine, methionine, phenylalanine, glutamic acid


Reagents used:Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent KTX (or CP) 25-50mlDehydrated Solvent OL II (or CM)


Samplequantity (g)


Moisturecontent (%)

Acetic acidMonochloroacetic acidDichloroacetic acidPropionic acidSalicylic acidOxalic acidStearic acid

Ketone-type

""

General-use

""

Oil-type

4.83651.01100.78174.96703.51860.12112.4937

07.8602.7000.8610.9200.8535.1900.42

00.1600.2700.1100.2200.02429.100.017

Dehydrated Solvent KTX should be used in combination withKarl Fischer Reagent SS-Z, and Dehydrated Solvent CP withKarl Fischer Reagent SS.

Note:


91

Substance Electrolyte Samplequantity(g)

Measurementvalue (µg)


Formic acidAcetic acidPropionic acidDichloroacetic acidSalicylic acidStearic acidOxalic acid

Ketone-type

"""

General-use

""

1.22001.05000.99301.56301.62222.14180.0222

Not measurable068713211313034101306645

06551330084002100061

29.9%

(2) Coulometric titration Reagents used: Aquamicron AKX (or AX) 100ml

Aquamicron CXU 5ml

9. Esters

Esters are substances for which moisture content can be measuredvery easily using standard Karl Fischer titration procedures. There areno significant interference reactions and behavior is similar to that ofhydrocarbons. Both volumetric and coulometric titration can be usedwithout any problem. For volumetric titration, a general-use dehydrated solvent is used.Solubility will be a problem with long-chain aliphatic esters and adehydrated solvent formulated for oils is recommended. With coulometric titration, measurements are carried out by adding thesample directly to the electrolyte (anolyte).

Key Points


EstersMethyl formate, ethyl formate, methyl acetate, ethyl acetate, aryl formate,methyl acrylate, methyl methacrylate, ethyl malonate, methyl valerate, methyladipate, methyl sebacate, methyl glycolate, 2,3-butylene di-acetate, ethylcitrate, cyclohexyl acetate, methyl benzoate, methyl salicylate, phenylacetate

Inorganic estersEthyl carbonate, ethyl chlorocarbonate, butyl nitrite


92

Lactones �-butyrolactone

Carbamic acid estersMethyl carbamate, ethyl carbamate


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX (or MS) 25-50ml


Aquamicron CXU 5ml


Samplequantity (g)



Methyl acetateEthyl acetateMethyl acrylate�-Butyrolactam




Methyl acetateMethyl isoamyln-Butyl acetateIsopropyl isovalerateDi-isopropyl malonateBenzyl benzoate

2.52500.85482.45890.91861.07401.58253.1695

1051280

1951256

449319512

421494

791367

418202162

General-use

"""

0.94674.35572.80985.6364

2.150.865.311.18

2224197

1890210


93



10. Organic Acid Salts

Since organic acid salts containing water of crystallization dissolvereadily in methanol, their moisture content can be measured easilyusing a general-use dehydrated solvent. In the case of organic acidsalts that do not contain water of crystallization, moisture content canbe measured by dissolving or dispersing the substances in a general-use dehydrated solvent. As these substances are solids with a highmoisture content, we recommend measurement using volumetrictitration. The organic salt sodium tartrate dihydrate was formerly sed as astandard reagent for determining the titer of Karl Fischer reagents foruse in volumetric titration.

Key Points


Organic acid salts containing water of crystallizationBarium acetate, cadmium acetate, cobalt acetate, lead acetate, magnesiumacetate, nickel acetate, sodium acetate, zinc acetate, uranyl acetate, sodiumcitrate, l ithium citrate, calcium lactate, calcium malonate, sodiumnaphthionate, ammonium oxalate, potassium oxalate, calcium propionate,sodium succinate, sodium benzoate, sodium tartrate

Organic acid salts without water of crystallizationAmmonium acetate, sodium adipicate, potassium hydrogen tartrate,ammonium citrate, sodium formate, sodium phthalate, zinc stearate


94


Samplequantity (g)


Moisturecontent (%)

Sodium L-aspartateLithium citrateSodium citrateAmmonium acetateCadmium acetateMagnesium acetateLithium acetateSodium acetateSodium napthionateCalcium lactateOxalic acidManganese benzoateCalcium stearate

General-use

"""""""""""

Oil-type

0.08410.03540.08121.28840.27500.19180.10030.06780.07310.20030.08250.08620.2046

04.3208.7310.0806.4437.0764.2704.1310.7505.8558.3923.5809.4505.98

05.14024.70012.40000.50013.50033.50011.50015.80022.80029.20028.60011.00002.920

11. Organic Hydrates

Since organic hydrates are solids, measurements can normally becarried out directly using volumetric titration. For measurements usingvolumetric titration, these substances can be dissolved or dispersed ina general-use dehydrated solvent. As with organic acid salts,volumetric titration is generally recommended for organic hydrates. Water of crystallization is not always stable in organic hydrates andmoisture content frequently varies with reference to temperature andhumidity. Cyanuric acid, in particular, tends to lose most of its water ofcrystallization.

Key Points


Pyromellitic acid, L-asparagine, creatine, L-histidine, dextrose, L-rhamnose,raffinose, chloral hydrate, ninhydrin, alloxan, piperazine, o-phenantholine,brucine, brucine sulfate


95




Sample quantity(g)


Moisturecontent (%)

Chloral hydrateHydrazine hydrate

General-use

"

0.17520.0732

19.2725.68

11.035.1


96

12. Amines

Some amines exhibit unusual behavior during Karl Fischer titration. Thatbehavior falls into two categories; that caused by basicity and thatcaused by other chemical interference reactions. The titrationconditions must be modified in accordance with the nature of thebehavior that is involved. In terms of basicity, substances can be divided into two groups usingbenzylamine with a pKa value of 9.4 (Ka=2.4 x 10-5) as the dividing line. 1) Amines below pKa9.4 Titration can be carried out without difficulty using standard proceduresand behavior is comparable with hydrocarbons. In the case ofvolumetric titration, the substances are dissolved in a general-usedehydrated solvent and titrated directly. With coulometric titration, thesample is introduced into a general-use electrolyte (anolyte) and titrateddirectly. 2) Amines with strong-basicity (above pKa9.4)Aside from the Karl Fischer reactions with water, interference reactionscaused by the strong basicity of these substances gradually consumethe Karl Fischer reagent and are known to cause the followingphenomena. a. Poor end point stabilityb. Failure to reach end pointc. Abnormally high analytical results To suppress these interference reactions, the substances must beneutralized with acids before titration and the Karl Fischer titrationsystem must be kept in a state that is close to neutrality. Salicylic acid isnormally used for this purpose as it causes almost no esterificationreaction with titration solvents which have methanol as their mainingredient. If acetic acid is used, the esterification reaction must besuppressed by chilling the system to 15 �C or below during the KarlFischer titration. For volumetric titration the titration solvent is prepared by dissolving 10gof salicylic acid in 50ml of Dehydrated Solvent GEX (or MS). For coulometric titration the electrolyte is prepared by dissolving 10g ofsalicylic acid in 100ml of general-use electrolyte (anolyte).

Key Points

Note: Up to 70mmol of amine can be neutralized with 10g ofsalicylic acid. This is why titration is normally carried outcontinuously with a quantity that corresponds to a sample of70mmol.


97

Substances that react with electrodes or cause other interferencereactionsCoulometric titration cannot be used for substances that react withelectrodes, such as aniline, toluidine, diamines and aminophenol. With substances such as aniline or toluidine, the end point will not be clear ifmethanol is used as the titration solvent for volumetric titration. Volumetrictitration is possible, provided that Dehydrated Solvent CP is used. Diaminescause an interference reaction with iodine, with the result that the end pointis never reached.

Reference:(1) Muroi, K. et al., "Measuring Trace Moisture Content inAmines Using the Karl Fischer Method" (in Bunseki Kiki[Analytical Equipment] 8, 374, 1969).

(2) Kato, H. et al., "Determination of Moisture in Amines by KarlFischer Coulometric Titration" (in Bunseki Kagaku 34, 805(1985).

Examples of substances that can be measured directly using standardmethods:Pyridine, 2-aminopyridine, 2-picoline, quinoline, pyrrole, imidazole, triazine,triazole, indole, carbazole, benzothiazole, N,N-dimethylanil ine,diphenylamine, 2-pyridyl ethanol, 4-pyridyl ethanol

Examples of substances that require neutralization with acid:Trimethylamine, ethylamine, diethylamine, triethylamine, propylamine,isopropylamine, 3-methoxypropylamine, butylamine, di-isobutylamine, di-sec-butylamine, dipentylamine, hexylamine, N,N-dimethylcyclohexylamine,dicyclohexylamine, benzylamine, pyrrolidine, piperidine, piperazine,morpholine, ethanolamine, N,N-dimethylethanolamine, diethanolamine,triethanolamine, di-isopropanolamine, tr i- isopropanolamine, Tris(hydroxymethyl) aminomethane

Examples of substances that require a methanol-free titration solvent:Aniline, toluidine, anisidine, naphthylamine


98

[Examples of Measurement](1) Volumetric titration --neutralization using salicylic

Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX (or MS) approx. 50mlSalicylic acid approx. 10g


or with approx. 10g of Salicylic acid addedAquamicron CXU 5ml


Samplequantity(g)


Moisturecontent (%)

n-ButylamineDiethylamineDiethanolaminePiperidineTri-n-butylamineDi-isopropyl amine2-MethylaminopyridineTriethanolamineN-Ethyl morpholineN,N-Dimethyl benzylamineN-Ethyl anilineAniline

General-use+Salicylic acid

""""""""""

Ketone-type

0.73350.72341.02400.90341.63671.50101.05201.12400.90500.90000.95801.0185

1.451.022.621.001.271.210.470.700.881.550.551.49

0.2000.1400.2600.1100.0770.0810.1200.1700.2600.1700.0570.150

Note: Salicylic acid crystals are bulky and difficult to handle. Toovercome this problem, place 10g of salicylic acid in an emptytitration flask and add Dehydrated Solvent GEX. The salicylicacid will dissolve readily and can be rendered moisture-freethrough a Karl Fischer titration that prepares for the maintitration.


99

Substance pKa Sample quantity(g)


Moisturecontent (%)

i-Propylamine 10.6 0.694 321 463ppmn-Butylamine 10.6 0.732 2440 0.333n-Hexylamine 10.6 0.766 496 648ppmDiethylamine 11.0 0.707 989 0.140Di-i-propylamine 11.1 0.722 931 0.129Di-n-butylamine 11.3 0.760 3231 0.425Triethylamine 10.7 0.726 5582 0.769Tri-n-propylamine 10.7 0.753 1159 0.154Tri-n-butylamine 10.9 0.778 626 805ppm3-Dimethylamino propionitrile 6.9 0.870 2635 0.303Cyclohexylamine 10.6 0.867 1741 0.201Monoethanolamine 9.5 0.269 614 0.228Diethanolamine 9.0 1.097 1199 0.109Triethanolamine 7.8 1.124 1870 0.1662-Diethylaminoethanol 9.4 0.884 2757 0.3121,3-Diaminopropane 0.218 1471 0.6751,2-Propane diamine Cannot be measuredPyrrolidine 11.3 Cannot be measuredPiperidine 11.2 0.861 3971 0.4614-Benzyl piperidine 10.3 0.997 6314 0.633Piperazine 0.200 210 0.105Pyrrole 0.967 3104 0.321N-Methyl morpholine 7.7 0.905 1907 0.211Benzylamine 9.4 0.268 452 0.169N,N-Dimethyl benzylamine 8.9 0.900 1042 0.1162-Amino-3-picoline 6.7 1.031 2621 0.2542-Methyl aminopyridine 6.7 1.052 1280 0.122o-Toluidine 4.4 Cannot be measuredm-Toluidine 4.7 Cannot be measuredp-Anisidine 5.3 Cannot be measuredm-Aminophenol 4.2 Cannot be measuredDimethyl aminomethyl phenol 7.9 0.986 1606 0.163N,N-Dimethyl-p-toluidine 5.6 0.937 494 527ppmAniline 4.6 Cannot be measuredN,N-Diethyl aniline 6.6 0.938 102 109ppmo-Chloro-aniline 2.6 1.213 361 298ppm2-Anilinoethanol 4.0 1.085 2614 0.241


100

13. Amides, Anilides

The moisture content of amides and anilides can be measured easilyusing standard methods. Amides behave in the same way as weak-basicity amines. Both volumetric and coulometric titration can be used. For volumetric titration, use either a general-use or an oil-typedehydrated solvent, depending on the solubility of the sample. In the case of coulometric titration, the sample is added directly to theelectrolyte (anolyte).

Key Points


Formamide, acetamide, malonamide, dimethyl formamide, urea, ethyleneurea, biuret, acetyl urea, alloxan, benzamide, salicylamide, acetanilide,propionanilide




SampleQuantity (g)


MoistureContent (%)

FormamideN,N-Dimethyl formamideUreaAcetanilideStearamide

General-use

"""

Oil-type

2.23072.64662.50004.91103.6953

1.713.281.4010.350.15

0.0770.1240.0560.2110.004


101

14. Nitriles, Cyanohydrins

Nitriles have weak basicity and can be measured easily using standardmethods. Reliable moisture measurement is also possible withcyanohydrins. Both volumetric and coulometric titration can be used. For volumetric titration, a general-use dehydrated solvent is used. Forcoulometric titration, the sample is added directly to the electrolyte(anolyte).

Key Points


Acetonitrile, aminoacetonitrile, acrylonitrile, sebaconitrile, methyleneaminoacetonitri le, adiponitri le, acetone cyanhydrin, formaldehydecyanohydrin, acrolein cyanohydrin acetate




SampleQuantity (g)


MoistureContent (%)

Acetonitrile General-use 2.1687 3.22 0.148


Aquamicron CXU 5ml



Moisture Content(ppm)

FormamideN,N-Dimethyl formamideAcetamideN,N-Dimethyl acetamideOleylamideErucamide

2.11732.64844.68661.15902.17903.8854

1510552314707

78148

713208067612036038


102


Aquamicron CXU 5ml




AcetonitrileAcrylonitrile

0.76910.0800

822295

10703690

15. Hydrazines

Iodine oxidation causes hydrazine derivatives to react with Karl Fischerreagent as shown in the following formula.

2C6H5NHNH2+2I2�3HI+C6H5NH2 HI+C6H5NN=NKarl Fischer titration is possible also with acidic solvents. Moisturecontent can be measured without this reaction if the sample is firstdissolved in an excess of acetic acid (approx. 2g of sample in 25ml ofacetic acid). The moisture content of dinitrophenyl hydrazine and benzoyl hydrazinecan also be measured accurately if the sample is dissolved in aceticacid and then titrated. Hydrazine hydrochloride reacts with iodine on amole-for-mole basis, but hydrazine sulfate does not react with KarlFischer reagent and can be dissolved in methanol for titration. In the case of hydrazine compounds, volumetric titration is the onlymethod that can be used. Coulometric titration is not suitable.

Key Points


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX (or MS) approx. 50mlTitrate after cooling to 15�C or lower.


SampleQuantity (g)


MoistureContent (%)

Hydrazine General-use 0.0296 0.84 2.85


103

Substance Sample moisture(%) Added moisture

content (%)Amount addedMeasurement value

Semicarbazide hydrochloridePhenylhydrazine hydrochloride

0.39�0.000.37�0.01

2.522.50

2.502.53

16. Other Nitrogenous Compounds

Both volumetric and coulometric titration can be used directly for othernitrogenous compounds. For volumetric titration, the substance isdissolved in a general-use dehydrated solvent and titrated. If asubstance is difficult to dissolve its solubility can be improved with theaddition of another solvent. Coulometric titration is carried out using a general-purpose electrolyteand in accordance with standard procedures.

Key Points

Examples of substances that can be titrated directly:Lactam, Imines

-Caprolactam, benzal-n-butylimineCyanohydrine

Formaldehyde cyanohydrin, acetone cyanhydrin, acrolein cyanohydrinesAzo-, azole compounds

p-Aminoazobenzene, diazoaminobenzene, benzotriazoleIsocynates, nitroso compounds

1-Naphthyl isocynate, phenyl isocyanate, N-nitrosodiphenylamineNitro compounds

Nitromethane, nitroglycerine, 2-nitropropane, m-dinitrobenzene, 3,5-dinitrobenzoic acid

Oximes, hydroxamic acidsAcetone oxime, dimethylglyoxime, butylaldoxime, hepta-aldoxime,cyclohexanone oxime

Cyanic acid derivatives Cyanamides, dicyanamides, cyanuric acid, melamine

AmidinesGuanidine nitrate


104




SampleQuantity (g)


MoistureContent (%)

NitromethaneNitroethane1-Nitropropanem-Nitroanilinep-Nitrophenol o-Nitro-p-chloroanilinem-Dinitrobenzene2,4-Dinitrotoluene

-CaprolactamN-Methyl pyrrolidinem-Nitro-p-toluidinep-Dichloro nitrobenzene

General-use

"""""""""

*1*2

5.62352.06721.85752.32330.98440.92091.08351.99351.53363.15192.1785

10.1400

0.994.632.751.26

11.300.300.150.063.222.140.450.78

0.0180.220.150.0541.150.0330.0140.0030.210.0680.0210.008

*1: Dehydrated Solvent MS 25ml + dinitromethane 10ml*2: Dehydrated Solvent MS 25ml + dichloromethane 10ml


Aquamicron CXU 5ml




NitromethaneNitroethane1-Nitropropane2-Nitropropanep-Nitrophenol m-Nitroanilinem-Nitro-p-toluidineo-Nitro-p-chloroanilineN-Vinyl pyrrolidone

-CaprolactamIsocyanate

1.1312102370.97571.03380.51961.51202.01931.00601.06750.64483.3597

99322241324

8165507

875404295340

129095

8790.217%0.136%

7891.06%

579200293319

0.200%028

In all cases, samples can be measured up to a volume of 20-50ml, as shownin the table.


105

17. Acid Anhydrides

Acid anhydrides and acylates can be measured directly usingvolumetric titration. The sample is subjected to Karl Fischer titrationafter it has been dissolved in either a general-use dehydrated solvent ora compound solvent made up of one part pyridine to four partsmethanol by volume.

Key Points

Examples of substances that can be titrated directly:Acid AnhydridesAcetic anhydride, propionic anhydride, butyric anhydride, n-valericanhydride, succinic anhydride, benzoic anhydride, phthalic anhydride

The following acid chlorides cause interference through oxidation of thehydriodic acid in Karl Fischer reagent and the release of free iodine. Forthis reason, water content is measured using volumetric titration asfollows. To suppress the interference, neutralize the sample by adding 1-3g ofthe sample to a methanol solvent that includes 20% pyridine/sulfurdioxide (SO2 32g/pyridine 100ml). Then carry out the Karl Fischertitration. 1) Potassium dichloroisocyanurate

C3N3O3Cl2K+2SO2+3C5H5N+CH3OH �C3N3OH(OCH3)2+C5H5N•HCl+KCl+2C5H5N•HSO4CH3

2) Aryl sulfonyl chlorideArSO2Cl+CH3OH+C5H5N � ArSO3CH3+C5H5N•HCl

Coulometric titration cannot be used because of the interference.

Key Points

18. Acid Chlorides

Examples of substances that can be titrated directly:Acid Chlorides Propionyl chloride, butyryl chloride, valeryl chloride, caproyl chloride, caprylchloride, stearoyl chloride, benzoyl chloride


106


Reagents used:Karl Fischer Reagent SSDehydrated Solvent MS + SO2/pyridine solvent 25-50ml

Substance

Potassium dichloroisocyanuratep-Toluene sulfonyl chloridep-Chlorobenzene sulfonyl chlorideToluene 2,4-disulfonyl chloridep-Ethylbenzene sulfonyl chlorideMethanesulfonyl chloride

Sample quantity(g)

Measurement value(mg)

Moisture Content(%)

1.02281.05411.00590.87211.67082.9444

2.450.821.202.180.542.10

0.24*0.0780.12**0.250.0320.071

*: Drying method 0.23%**: Infrared method 0.14%

19. Quinones

Quinones interfere with the titration through the oxidation of hydriodicacid, which is produced from a reaction between water and KarlFischer reagent, to produce free iodine. For this reason, direct titrationis impossible. Instead, an indirect method based on water vaporizationis used. Either volumetric or coulometric Karl Fischer titration can be used. Referto the section on Basic Knowledge for information on the watervaporization method.

Key Points

[Examples of Measurement](1) Water vaporization - Volumetric titration

Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml

Substance Heatingtemperature (�C)

Samplequantity (g)


Naphthoquinone (wet)Naphthoquinone (dry)p-Quinone

160160130

Moisturecontent (%)

6.430.0370.0042

7.620.820.15

0.11852.20963.5710


107

20. Peroxides

As shown in the following formula, peroxides react with the sulfurdioxide in Karl Fischer reagent. In general, however, there is nointerference.

ROOH+SO2 � RHSO4

It is important to ensure that there is always an adequate excess ofsulfur dioxide. Acetyl peroxide is highly reactive and causes interference by releasingiodine through the oxidation of hydrogen iodide.

(CH3COO)2+2HI � 2CH3COOH+I2

Other substances may also cause interference if there is insufficientsulfur dioxide. Dialkyl peroxides (R-OO-R) are not reactive and have noeffect on Karl Fischer titration. Diacyl peroxides (RCO-OO-OCR) causeinterference through the oxidation of hydrogen iodide as shown in thefollowing formula.

RCO-OO-OCR+HI � 2RCOOH+I2

Key Points

Examples of substances that can be measured directly:Di-tert-butyl peroxide (this substance causes an exothermic reaction whentitrated with Karl Fischer reagent, but moisture content can be measuredaccurately), diethyl peroxide, lauryl peroxide, triacetone peroxide


108

21. Sulfur Compounds

The moisture content of most sulfur compounds, including sulfides,disulfides, thiocyanic acid and sulfonic acid, can be measured bymeans of direct t i tration using standard procedures. As withhydrocarbons, these compounds have a tendency to slow the rate ofthe reaction between water and Karl Fischer reagent, so they shouldalways be measured in excess methanol. For volumetric titration, the substances are measured after they havebeen dissolved in a general-use dehydrated solvent. For coulometric titration, the sample is added directly to a general-useelectrolyte (anolyte).

The only substances that cause interference are mercaptan, thiourea,thioacetic acid and dithio acid. These consume Karl Fischer reagent byreacting with iodine as shown in the following formulae.

2RSH+I2 � RSSR+2HI2RCSSH+I2 � RCSSSSCR+2HI

Before these substances can be titrated, they must be neutralized usingspecial procedures. Dimethyl sulfoxide (DMSO) exhibits unusual behavior. Karl Fischertitration appears to move toward a stable end point without anydifficulty, but with sequential addition of the sample the moisturecontent declines with each analysis. It is important to note that thepresence of DMSO reduces the percentage of water recovered.

Key Points

Examples of substances that can be measured directly:SulfidesCarbon disulfide, allyl sulfide, n-butyl sulfide, n-butyl disulfide, thiophene,benzothiopheneThiocyanates, etc. Ethyl thiocyanate, ethylene thiocyanate, n-butyl thiocyanate, ethylisothiocyanate, 1-naphthyl isothiocyanate, ethyl thioacetate, benzothiazole,1-acetyl-2-thiourea, methyl isothiourea


109




Samplequantity (g)



Carbon disulfideDimethyl sulfoxide

General-use

"

6.30503.0721

0.620.92

098298


Aquamicron CXU 5ml




Dimethyl sulfoxideBenzothiophene

1.07731.1633

784158

728136

Measuring the Moisture Content of MercaptanInterference caused by mercaptan can be eliminated by reacting an activeolefin such as octene with the sample using boron trifluoride as the catalyst.

BF3

RSH+R'CH=CHR' � R'CH(SR)CH2R'

a) Reagent Solution of boron trifluoride and ethyl ether (BF3 45%)or Solution of boron trifluoride and acetic acid (100gBF3/l)Isooctene, glacial acetic acid, pyridine

b) Measurement method Put 5-10ml of glacial acetic acid into a 250ml measuring flask. Add thesample making sure that the amount of mercaptan does not exceed 15millimoles. Next, add 3ml of boron trifluoride/ethyl ether solution or 10ml ofboron trifluoride/acetic acid solution and 6ml of isooctene. Mix well andleave for about 30 minutes at room temperature. Carefully add 5ml ofpyridine and then titrate the solution with Karl Fischer reagent. Using thesame procedures, obtain a dummy test result for the reagent. Subtract thisfrom the titration value to determine the moisture content. However, thereagent used should always be thoroughly dehydrated.(JACS., 62, I (1940))


110

Note:

Reference:

An error will occur at the rate of 0.3ppm of water for every 1ppmof sulfur in the mercaptan. If the mercaptan content is low, anaccurate measurement of the moisture content can be obtainedby adjusting the measurement value.

JISK2275 Crude oil and petroleum products - Determination ofwater content

Test Examples

Sample Moisture(%)

Ethyl mercaptanIsopropyl mercaptanButyl mercaptanIsoamyl mercaptanHexyl mercaptanHeptyl mercaptanBenzyl mercaptanThiophenol2-ThionaphtholThioglycollic acid

0.700.900.850.400.150.700.250.250.053.85

6.306.303.052.851.854.602.80

-1.356.95

6.356.253.052.901.854.602.80

-1.357.00

Other Substances that Cause Interference It may not be possible to obtain a clear end point with thiourea as it reactswith iodine. This is because thiourea triggers tautomerism and interconvertsto isothiourea, which causes the same reaction as mercaptan.

NH2 NH2�S=C HSC �NH2 NH

content (%)Added moisture Observed moisture(%)


111

1-Phenyl-2-thiourea, 1, 3-diphenyl thiourea and thiobenzamide also react inthe same way as thiourea. However, N-methyl thiourea and 1-acetyl-2-thiourea can be titrated directly without causing a reaction. When thioacetatic acid is titrated directly, it reacts quantitatively with KarlFischer reagent and consumes 1 mole of iodine per mole. Dithio acidcauses a similar quantitative reaction. This interference can be prevented bytaking the following preliminary steps.

First, add an equivalent amount of n-butanol to the sample and treat it witholefin using boron trifluoride as the catalyst. It appears that the butylmercaptan produced in this way combines with the olefin as shown in thefollowing formulae.

CH3COSH+C4H9OH � CH3COOH+C4H9SHRCSSH+C4H9OH �RCSOH+C4H9SH

If excess butanol is used it will react with the acid during titration andproduce ester and water. The results must be corrected to allow for this.

II-2. Inorganic Compounds

112


Interference reactions are more common with inorganic compounds thanwith organic compounds. Refer to the comments on interference in Q9 of thesection on Basic Knowledge. Also, the moisture vaporization method is usedmore often because there are a number of substances that cannot bedissolved in the titration solvents. For each substance, it is essential toconsider whether or not to use the moisture vaporization method (heatvaporization system). In addition, when taking measurements carefulconsideration must be given to the way in which moisture is present(adhesion water or compounded water).


113

1. Metals and Simple Substances

Since these substances are solids and cannot be dissolved inmethanol, they are normally measured using the moisture vaporizationmethod. The sample is powdered in preparation for the measurement.During this preliminary process it is important to prevent absorption ofhumidity or dissipation of the moisture content. For volumetric titration, it is possible to disperse the sample indehydrated solvent and carry out Karl Fischer titration directly.However, the moisture vaporization method is normally used. With coulometric titration the presence of insoluble substances, such aspowdered metal, interferes with the electrode reaction. Other causes ofinterference include membrane blockage. For these reasons,coulometric titration cannot be used directly. In most cases the moisture vaporization method is effective with thesesamples. Because moisture content is commonly low, Karl Fischertitration is carried out using the coulometric method. The heatingtemperature for moisture vaporization is 100-250�C. If necessary, theprocess can be carried out at temperatures of 600-700�C.

Key Points


114




Samplequantity (g)


Moisturecontent (%)

Aluminum pastePowdered aluminum + oilPowdered tungstenTitaniumSulfurFerrite

General-use

"""""

0.25240.59684.28800.45411.17100.3121

00.8300.1500.7110.9700.4711.11

0.3290.0750.0172.420.0423.56


Aquamicron CXU 10ml

Substance HeatingTemperature (�C)

Samplequantity (g)


Moisturecontent (%)

Aluminum pastePowdered aluminumPowdered metal (Cd)

"Powdered metal (zinc)Powdered siliconPowdered cobalt alloyPowdered brassCopper wirePowdered lead tinNickelPowdered sulfurRed phosphorusFerrite

110600110250250700200250200400250100180700

0.26463.32840.25720.14943.83450.05372.34611.52772.44549.90061.07242.31430.20360.0774

3831524354787

351252

5631951

332531316151

14703034

1.45157ppm

0.1380.5279ppm2.33

240ppm0.128

136ppm54ppm295ppm65ppm0.7223.92


115

Examples of test methods1) Sulfuric acid

Concentrated sulfuric acid (95% or higher) causes an esterificationreaction in methanol and produces water. By adding 50ml of DehydratedSolvent MS and using a small sample (approx. 0.5g or less), it is possibleto carry out direct titration without any interference reaction.

2) Nitric acid The reagent nitric acid can be titrated directly by adding about 0.3g ofsample to 50ml of Dehydrated Solvent MS. In the case of fuming nitricacid, the sample will have to be neutralized with pyridine.

2. Inorganic Acids

The following problems arise when methanol is used as the titrationsolvent for inorganic acids.

1) The pH of the Karl Fischer titration system is shifted to the acid side. This lowers the reaction rate.

2) An esterification reaction occurs with acids at high temperatures. This produces water, raising the measurement value.

To suppress these interference reactions the sample should beneutralized with an amine, such as pyridine, before Karl Fischertitration. Since these substances commonly have a high moisture content,volumetric titration is used. It is convenient to use Dehydrated SolventMS (manufactured by Mitsubishi Chemical). As this product contains arelatively high percentage of pyridine as a reaction accelerant, it is notnecessary to add more pyridine. In the case of hydrogen chloride gas, moisture is condensed in specialapparatus at -78�C. The main constituent, hydrogen chloride, is thenseparated so that the condensed water can be dissolved in pyridine-methanol and titrated.

Key Points

Reference:Muroi, Ono: Microchem.J., 18,234 (1973)"Determination of Trace Moisture in Hydrogen Chloride Gas byKarl Fischer Titration."


116

3) Hydrochloric acid The reagent hydrochloric acid can be titrated directly by adding about0.03g of sample to 50ml of Dehydrated Solvent MS.

4) Hydrofluoric acid The reagent hydrofluoric acid can be titrated directly by adding about0.03g of sample to 50ml of Dehydrated Solvent MS. However, as hydrofluoric acid erodes glass parts of the titration cell andthe electrodes, teflon-coated parts should be used.

5) Hydrocyanic acid The reagent hydrocyanic acid can be dissolved in Dehydrated SolventMS for direct titration.




Samplequantity (g)


Moisturecontent (%)

97% Sulfuric acid92% Sulfuric acidNitric acidNitric acid (85%)Hydrochloric acid (38%)Hydrofluoric acid (48%)Hydrocyanic acidPhosphoric acid (85%)

General-use

"""""""

0.24230.11450.03600.11550.03790.03680.38880.0533

07.6908.7435.0416.8723.6718.9605.5607.85

03.1707.6397.3014.6062.5051.5001.4314.70

Hydrogen chloride gas

Hydrogen chloride gas reacts with Karl Fischer reagent and cannot betitrated directly. The moisture content is titrated after condensation in a trapat -78�C, using the following procedures.

a) To ensure that the system is free of moisture, nitrogen gas that has firstbeen dried with silica gel and phosphorus pentaoxide is passed insidetitration flask D in the direction L � M � y at a rate of approximately0.5l/min. (The moisture content of the nitrogen that passed through thesystem is titrated.)


117

b) Titration flask D is cooled to -78�C in a methanol dry ice cooling bath. c) Immediately after the nitrogen flow has been stopped, the sample gas is

passed into titration flask D in the direction A � M � y at a rate ofapproximately 0.5l/min.

d) When 5~20l of gas has passed through the system, the three-way cock isswitched to allow nitrogen to flow into titration flask D in the direction L �M � y for about one minute to drive out all of the sample gas.

e) The flow of nitrogen is then stopped and 20ml of a 1:1 pyridine/methanolsolution is introduced from B to flush out the water that has condensed inE.

f) Titration flask D is removed from the methanol dry ice cooling bath. Whenthe flask has returned to room temperature, the water captured in thepyridine/methanol solution is titrated.

g) A dummy value is established from 20ml of pyridine/methanol solutionusing the same procedures. Moisture content is determined bysubtracting this value from the titration result.

A:Flowmeter for hydrogen chloride gas

B: Solvent injection portC: Cooling bathD: Titration flask E: Condensing tubeF: Nitrogen supply tubeG: Platinum electrodeH: Stirrer barI: Buret protectorJ: Buret for KF reagent K. Back-up titration flaskL,M,N: Three-way stop cocksO,P: Drying tubes

Figure 20: Titration Apparatus for Hydrogen Chloride Gas

Driednitrogen gas

Hydrogenchloride gas

Hydrogenchloride gas Nitrogen gas


118

Volume(l)

Gas flow rate (l/min.)



202020202020

0.30.40.50.60.70.8

0.440.430.450.400.380.33

12.612.412.811.510.409.4

Test Examples

Note:Karl Fischer Reagent SS with a titer of 0.35mg/ml was used. (At present there is no reagent with this titer.)

3. Hydroxides

Metallic hydroxides generally react with the iodine in Karl Fischerreagent in accordance with the following formula. In particular, alkalinemetal and alkaline earth hydroxides (strong basicity) react quantitativelyand rapidly.

M(OH)2+2HI � MI2+H2OFor example, lithium hydroxide, sodium hydroxide, potassium hydroxideand barium hydroxide all produce water and react immediately withKarl Fischer reagent. For this reason, direct titration cannot be used.Moisture content is measured using the moisture vaporization method.

Key Points

[Examples of Measurement](1) Moisture vaporization - Coulometric titration

Reagents used: Aquamicron AX (or AS) 150mlAquamicron CXU 10ml


119

4. Oxides

Metallic oxides generally react with the iodine in Karl Fischer reagent inaccordance with the following formula. In particular, alkaline metal andalkaline earth oxides (strong basicity) react quantitatively and rapidly.

MO+2HI � MI2+H2OA number of substances, such as magnesium oxide, zinc oxide, silver(I)oxide, mercury (I) oxide and copper (I) oxide, react with Karl Fischerreagent in accordance with the formula below.

ZnO+I2+SO2+CH3OH�ZnI2+HSO4CH3

Manganese dioxide reacts with Karl Fischer reagent as shown below.Lead dioxide and red lead cause similar reactions.

MnO2+I2+2SO2+2CH2OH�MnI2+2HSO4CH3

As a result, direct titration is not possible and moisture content ismeasured using the moisture vaporization method. For measurementusing moisture vaporization, the heating temperature for normaladhesion water is set at 100~200�C.

Key Points

Substance Heatingtemperature(�C)

Samplequantity (g)


Moisturecontent (%)

Calcium hydroxide

"Magnesium hydroxide Nickel hydroxide

"

110900150150600

0.63750.02890.49560.12220.1092

29536708

6701797

22098

0.463*23.2**0.135*1.47*

20.2**

*Adhesion water, ** bonded waterNote:


120




Samplequantity (g)


Moisturecontent (%)

Zinc oxide 200 2.1892 1715 783ppmAluminum oxide 200 1.4522 1801 0.124

" 700 0.7433 1581 0.213Antimony oxide 150 1.9930 211 106ppmCadmium oxide 250 0.7301 228 312ppmGadolinium oxide 800 0.1192 977 0.820Calcium oxide 100 1.3610 261 192ppm

" 800 0.2526 1862 0.737Silicon oxide 250 0.1295 1313 1.010Copper (I) oxide 110 0.4958 654 0.132

" 700 0.3140 4734 1.510Copper (II) oxide 700 0.6090 2366 0.389Titanium oxide 300 0.3858 3691 0.957Nickel oxide 250 0.9014 1135 0.126Bismuth oxide 100 2.5479 182 71ppmMagnesium oxide 130 0.2773 906 0.327Manganese oxide 750 0.1382 6650 4.810Iron (III) oxide 200 0.5168 1460 0.283

" 500 0.5353 1729 0.323Red iron oxide 200 0.4209 1751 0.416

" 700 0.4079 2076 0.509


121

5. Halides (halogenides)

As a general rule, halides do not cause interference and can bemeasured directly. Also, some halides can be dissolved in titrationsolvents and titrated with either volumetric or coulometric titration. Volumetric titration is carried out using a general-purpose dehydratedsolvent. If a substance cannot be dissolved or causes interference, themoisture vaporization method is used. Care needs to be taken whentaking samples as many of these substances absorb humidity veryreadily. Some substances, such as ammonium chloride, sodium chloride,potassium chloride, potassium iodide and cerium iodide, occlude theirmoisture content during crystallization. The extent of this effect isreported to be 0.1~0.3%. Since these salts generally dissolve readily informamide, moisture content can be measured using a dehydratedsolvent formulated for sugars as the titration solvent. Reference:Solubility of salts in formamide (g/100g)

NaCl 9.33 Nal 62.7KCl 6.31 Kl 62.5NH4Cl 11.05

Alkaline earth halides crystallize as hydrates. Substances that can bemeasured without major problems include magnesium chloride 6-hydrate, calcium chloride 2-hydrate, strontium chloride 6-hydrate, andbarium chloride 2-hydrate. The same is true of bromides and iodides.Potassium fluoride (anhydride and 2-hydrate) is soluble and can bemeasured without any difficulty. Calcium fluoride is insoluble and itsmoisture content cannot be measured through direct titration. Similar measurement procedures can be used for substances such asaluminum chloride 6-hydrate, manganese (II) chloride 4-hydrate, cobaltchloride 6-hydrate, cadmium chloride 2.5-hydrate and tin (IV) chloride5-hydrate. However, care is needed with the following salts as theirwater does not react with iodine on a mole-for-mole basis. With copper (II) chloride 2-hydrate, only 1.5 mole of water is measured.

CuCl2 � 2H2O+1.5I2+2SO2+2CH3OH�CuI+2HCl+2HI+2HSO4CH3

With iron (III) chloride 6-hydrate, only 5.5 mole of water can bemeasured.

FeCl3 � 6H2O+5.5I2+6SO2+6CH3OH�FeI2+3HCl+9HI+6HSO4CH3

Tin (II) chloride 2-hydrate is a powerful reducing agent. Directmeasurement is not possible as it reduces the iodine in Karl Fischerreagent.

SnCl2 � 2H2O+3I2+2SO2+2CH3OH�SnI4+2HCl+2HI+2HSO4CH3

Key Points


122




Aquamicron CXU 5ml

(3) Moisture vaporization - Coulometric titrationReagents used: Aquamicron AX (or AS) 150ml

Aquamicron CXU 10ml


Samplequantity (g)


Moisturecontent (%)

Aluminum chloride 6-hydrate General-use 0.0331 15.17 45.8Potassium chloride " 0.5178 1.37 0.26Magnesium chloride 6-hydrate " 0.0554 30.04 54.2Magnesium chloride anhydride " 0.6703 3.01 0.45Lithium chloride " 0.1004 5.11 5.09Manganese chloride " 0.0759 27.94 36.8Strontium chloride " 0.0412 16.75 40.6Vanadium chloride " 0.0766 18.10 23.6Barium chloride " 0.5933 86.92 14.7Lithium chlorate " 0.1053 13.77 13.1Dried lithium chlorate " 0.0783 2.13 2.72Sodium iodide " 3.3707 1.63 0.048

Sample Sample quantity(g)


Moisture content(%)

Aluminum chloride 6-hydrateManganese chloride Lithium chloride Sulfur hexafluoride

0.01660.16070.0932

10.29

7490070047800230

45.10000.43605.13022ppm


123


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX, OL II (or MS, CM) 25-50ml

6. Carbonates, Bicarbonates

Direct measurement is not possible with carbonates and bicarbonatesas they react with Karl Fischer reagent and cause interference. Thedegree of interference depends on the solubility of each substance. Forexample, alkaline metal carbonates and bicarbonates react as shown inthe formulae below.

K2CO3+I2+SO2+CH3OH�2KI+CO2+HSO4CH3

KHCO3+I2+SO2+CH3OH�KI+HI+CO2+HSO4CH3

Direct measurement is possible with calcium carbonate. Since it doesnot dissolve in dehydrated solvent it is dispersed and the moisturecontent extracted. This is only possible with volumetric titration. Direct measurement is not possible with sodium bicarbonate and themoisture vaporization method is also unsuitable as the substancereleases water when heated. In general, for carbonates that are stablewhen heated, the moisture content is measured using the moisturevaporization method.

Key Points


Samplequantity (g)


Moisturecontent (%)

Potassium chloride

"Lithium chloride Cesium iodide Sodium iodide Barium fluoride Aluminum fluoride Zinc fluoride

100750200200400800800500

0.99031.00210.10359.59752.90790.53230.62440.8577

105630445117

181510

29155

596

0.1070.3044.9402ppm

519ppm547ppm88ppm

695ppm


124

Measuring the moisture content of sodium bicarbonateSodium bicarbonate is used in fire extinguishers and various other applications. Eventrace amounts of moisture can lead to problems during storage or use. It is difficult tomeasure moisture content accurately using the conventional sulfuric acid dessicatormethod, so the Karl Fischer titration method is used together with a moistureextraction-correction technique as described below. Approximately 100g of sample is taken in a 500ml separating funnel. To this, 130ml ofdehydrated methanol is added. The mixture is stirred well and then left to stand.When the sample and methanol have separated, 50ml of liquid is extracted andplaced in the titration flask of a Karl Fischer titration system, and titrated. The smallquantity of sample dissolved in the extracted liquid is titrated by neutralizationtitration, and the moisture content is determined by correcting the Karl Fischertitration result.

N.G. Leavitt, C.B. Robert: Anal.Chem., 26,1367 (1954).


Samplequantity (g)


Moisturecontent (%)

Calcium carbonateCalcium carbonate

General-useOil-type

1.02721.0053

1.861.63

0.1810.162

Note:The end point was more stable with an oil-type dehydratedsolvent.


Aquamicron CXU 10ml


Samplequantity (g)


Moisturecontent (%)

Calcium carbonate

"Potassium carbonateSodium carbonate Barium carbonate

"Basic magnesium carbonate Manganese carbonate

"

100600200180300700250110600

0.12230.09750.62780.20040.67610.84370.02490.03340.0466

623155417124099

8051103360517233699

0.5091.580.2732.050.1190.131

14.55.167.94

Reference:


125

7. Sulfates, Sulfites

Differences in reactivity to Karl Fischer reagent mean that the choice ofdirect titration method must be made with reference to the individualsubstance. In most cases we recommend the measurement of moisturecontent using the moisture vaporization method. Sulfates crystallize ashydrates. In general, hydrates with six or more molecules of water ofcrystallization dissolve in methanol and remain in solution duringtitration. This means that they can be measured directly using ageneral-purpose solvent. Some examples of this type of substance arelisted below.

Na2SO2 � 10H2O, MgSO4 � 7H2O, NiSO4 � 6H2O, ZnSO4 � 7H2O,Al2(SO2)2 � 18H2O,KAl(SO4)2 � 12H2O, FeSO4 � (NH4 )2SO4 � 6H2O

Water is strongly bonded in zinc sulfate 1-hydrate and manganesesulfate 1-hydrate and cannot be measured. Karl Fischer titration cannotbe used for calcium sulfate 2-hydrate at normal room temperatures asthe water is released very slowly. Total moisture content can bemeasured by using the moisture vaporization method at a temperatureabove 200�C. Copper sulfate causes interference by oxidizinghydrogen iodide, the reactive substance in Karl Fischer reagent. Thisreaction frees 0.5 moles of iodine.

CuSO4+2HI � CuI+0.5I2+H2SO4

As the resulting free iodine acts as a reagent, the measurement resultswill be low. In general, the weakly acidic salts of alkaline metals react inthe same way as oxides. Sulfites and pyrosulfites react quantitatively. Sodium sulfite and sodium pyrosulfite react as shown in the following formulae.

Na2SO3+I2+CH3OH � 2NaI+HSO4CH3

Na2S2O5+I2+CH3OH � 2NaI+SO2+HSO4CH3

Accordingly, the moisture vaporization method is used with these salts.

Key Points


126


Samplequantity (g)


Moisturecontent (%)

Sodium metabisulfitePotassium metabisulfiteGypsum

150150250

0.19260.22150.2060

11.393.85

14.76

5.911.747.17


Samplequantity (g)


Moisturecontent (%)

Sodium dithionite(Sodium hydrosulfite)Sodium sulfiteAluminum sulfate

100�C dried200�C dried

Sodium sulfateCalcium sulfate

""

200

250

700700250200600900

0.4796

4.0301

0.02290.05153.13050.05210.06840.0612

2671

247

87878139

375331043373868

00.557

61ppm

38.40015.800120ppm06.350006.340006.3200

[Examples of Measurement](1) Moisture vaporization - Volumetric titration


(2) Moisture vaporization - Coulometric titration Reagents used: Aquamicron AX (or AS) 150ml

Aquamicron CXU 10ml


127

8. Other Salts

Some salts react with Karl Fischer reagent and others do not. Directmeasurement is possible with salts that do not react with Karl Fischerreagent and that can be dissolved or dispersed in a titration solvent. Asa general rule, moisture content can be determined easily by using themoisture vaporization method. First, however, it is necessary to take theheating temperature into consideration because of the need to checkfor such factors as intramolecular dehydration. Procedures for thevarious types of salts are described below. Nitrates can be measured directly using volumetric titration. A general-purpose dehydrated solvent is used. Depending on the solubility of thesubstance, a solvent formulated for sugars may be used. Examples ofsubstances for which this method is suitable include ammonium nitrate,sodium nitrate, potassium nitrate, chromium nitrate, cobalt nitrate andmercury (I) nitrate. Sodium nitrite cannot be measured directly as it reacts quantitativelywith Karl Fischer reagent as shown in the following formula.

NaNO2+0.5I2+SO2+CH3OH � NaI+NO+HSO4CH3

Chromates and bichromates also react with Karl Fischer reagent, butthe reactions are not quantitative. Potassium permanganate is insolubleand will not react. Sodium tetraborate produces a similar reaction withboric acid, and direct measurement is not possible.

Na2B4O7+7I2+7SO2+19CH3OH�2NaI+12HI+7HSO4CH3+4B(OCH3)3

Sodium arsenite reacts in the same way with oxides (anhydrousarsenites.)

NaAsO2+2I2+SO2+2CH3OH � NaI+AsI3+2HSO4CH3

Primary phosphates can be measured directly using volumetric titration. The behavior of secondary phosphates reflects their weak basicity, butthey do not cause any significant interference. Tertiary phosphatescause interference because of their strong basicity and they must beneutralized with acid before Karl Fischer titration.

Key Points


128


Samplequantity (g)


Moisturecontent (%)

Di-ammonium hydrogen phosphateSodium nitrateSodium nitrate

General-use

"Sugar-type

0.15112.11162.2079

3.942.462.73

2.610.116*0.124**

(2) Moisture vaporization - Volumetric titrationReagents used: Karl Fischer Reagent SS-Z (or SS)

Dehydrated Solvent GEX (or MS) 50-100ml


Samplequantity (g)


Moisturecontent (%)

Sodium metasilicate 200 0.1039 41.52 40.0


Aquamicron CXU 10ml


Samplequantity (g)


Moisturecontent (%)

Aluminum nitrateSodium nitrate

"Sodium tripolyphosphate

""

Di-ammonium hydrogen phosphateTri-sodium phosphateMagnesium hypophosphite

700130400100150250110150180

0.02002.09030.49481.18211.12191.15230.09600.03420.0338

0885300721015010155506044

End point 025681844913640

44.300345ppm00.30300.13200.539

not reached02.68053.90040.400



Note:* Partially insoluble. ** Soluble


129

9. Inorganic Gases

The moisture content of non-condensing gases, such as nitrogen,oxygen and hydrogen, is captured by passing the sample gas througha titration solvent or electrolyte. Karl Fischer titration is then carried out. It is necessary, therefore, toobtain and assemble equipment which includes pipes for the samplegases and gas meters. Metal pipes should be used at the injectionports. Pipes made of vinyl chloride or other plastics should be avoidedas these absorb atmospheric moisture. For volumetric titration, an absorption solution is prepared by mixing ageneral-use dehydrated solvent with propylene glycol in a ratio of 3:1.For short periods, general-use dehydrated solvent can be used alone.In such cases, changes in the quantity of the titration solvent, causedby volatilization, must be monitored carefully. For substances with low moisture content, accurate measurements canbe obtained by using a low-titer Karl Fischer reagent. Because of the minute amounts of moisture in inorganic gases, werecommend coulometric titration.

Key Points

[Examples of Measurement](1) Volumetric titration Place 150ml of dehydrated solvent in a titration flask. Titrate the Karl Fischer reagent to the end point to remove all moisture. Next pass the sample gasthrough the dehydrated solvent in the titration flask at a rate of 0.2-0.5l/min.The flow of gas should be measured using a gas meter. Stop the flow of gas(A) after the amount of water absorbed into the dehydrated solvent hasreached 5-50mg. Titrate (Bml) immediately using a Karl Fischer reagent witha known titer (FmgH20/ml). Calculate the moisture content (W%) accordingto the following formulae.

B �F�1.244 � �

A �100

A � � � �1000

B �F

W (Vol%) =

W (Wt%) =

� 100

� 100

760–––––––––

P

P–––––––––760

M–––––––––22.4

273–––––––––––––––273� t

(273�t)––––––––––––––––––

273


130

Here, P: Atmospheric pressure (mmHg) at time of measurementt: Temperature of gas at time of measurement (�C)M: Molecular weight of sample gas

Sample gas Sample quantity (l) Titration quantity (ml)

Moisture content (v/v%)

HydrogenNitrogenOxygen

10.030.030.0

2.210.383.09

0.0300.00170.014

Sample gas Sample quantity (l) Titration quantity (µg)

Moisture content (v/vppm)

NitrogenOxygenHydrogenArgon

20202020

475171099028

31.611.4

6.81.9

Note:Using Karl Fischer Reagent SS (titer: 1mg/ml)

Reference:Muroi, K., Bunseki Kagaku [Analytical Chemistry] 10, 847(1961)."Determination of a Micro-quality of Water in Gaseous Sampleby the Karl Fischer Method"

(2) Coulometric titration Inject 150ml of Aquamicron AX into the anode chamber of an electrolytic cellfitted with a gas adapter. Inject 10ml of Aquamicron CXU into the cathodechamber. Apply an electrolytic current to the Aquamicron AX while stirring,and use coulometric titration to remove all water from the system. Next, passthe sample gas into the electrolytic cell via the gas adapter at a rate of 0.3-0.5l/min. Use a gas meter to measure the volume of the gas flow. Stop theflow of gas after the amount of water absorbed into the Aquamicron AX hasreached 0.1-5mg. Immediately, carry out coulometric titration to the endpoint and calculate the moisture content.

Chapter III: Applications - 2

131


III-1. Industrial Products

132


133


In this section we provide some actual examples of the use of Karl Fischertitration with chemical products, other industrial products, foodstuffs,pharmaceuticals and other substances.


Most general chemical and industrial products consist of organic orinorganic compounds, either singly or as mixtures. This means that for manyproducts moisture content can be determined using Karl Fischer titration.Because of the wide variety of substance characteristics and forms,however, it is important to choose the most appropriate measurementmethod with reference to the substances that make up each product. In thischapter we give actual examples of moisture measurement for as manyproducts as possible.

1. Fertilizers

Single-salt fertilizers, such as ammonium sulfate, ammonium chloride,ammonium nitrate, urea and potassium chloride, can be eitherdissolved or dispersed in a general-use dehydrated solvent for KarlFischer titration. Other substances, such as synthetic fertilizerscontaining urea, should be dispersed in a general-use dehydratedsolvent in preparation for Karl Fischer titration. The moisture content ofsynthetic fertilizers that do not contain urea can be measured using themoisture vaporization method. Coulometric titration can be used only in conjunction with moisturevaporization. Moisture vaporization is sometimes effective with fertilizers, but accountmust be taken of the fact that some ingredients in compound fertilizers,such as urea, ammonium phosphate and single superphosphate, breakdown when heated to certain temperatures.

Key Points




134



Moisture Content(%)

Heating loss method(%)

Ammonium sulfateAmmonium chlorideSodium nitrateAmmonium nitrateUreaPotassium chlorideUrea+ammonium nitrateUrea+ammonium sulfate+ammonium phosphateChemical fertilizerHigh-grade chemical fertilizer

5.13215.05412.57845.06352.50892.51132.52132.5055

0.49200.1500

0.701.80

15.605.011.408.80

23.7533.75

14.635.34

136ppm356ppm

0.6050.099

558ppm0.3500.9421.35

2.973.56

0.0160.0440.590.0800.0600.360.941.30

2.233.30

Substance Heating Temperature(�C)

Sample Quantity(g)

Measurement Value(µg)

Moisture Content(%)

Ammonium sulfateChemical fertilizerHigh-grade chemical fertilizer

100100100

0.62940.09980.0929

282720003539

0.4492.003.81


Aquamicron CXU 10ml


135

Substance Sample Quantity(g)


Moisture Content(%) Remarks

Chloropicrin

Kitazine-PInsecticideCaptanNamekatPowdered sulfur

3.3387

1.08755.12630.23940.14371.0222

0.31

2.273.516.645.695.93

0.0093

0.2090685ppm2.77003.96000.5800

Turns brown immediately after end point

Insoluble


Aquamicron CXU 5ml

2. Agricultural Chemicals

Direct Karl Fischer titration is possible for substances that can bedissolved in dehydrated solvent. Samples of main ingredients and otherproducts can be dissolved in a general-use dehydrated solvent andtitrated directly. Powders that include fillers and other substancesshould be stirred for a while in a general-use dehydrated solvent. Themoisture content can then be fully extracted and titrated. Alternatively, the moisture vaporization method can be used. However, chloropicrin is oxidative and causes interference by freeingiodine. Substances that may react with Karl Fischer reagent include copperpowders, mercury powders, copper-mercury powders, zineb granulesand arsenate-lime powders. The normal moisture vaporization methodis suitable for agricultural chemicals in solid form. Adhesion water canbe measured at 100-150�C. The heating temperature should bedetermined in accordance with the individual substance.

Key Points




136


Measurement value (µg)

Moisture content (%)

IBP* 1.0260 2210 0.215

*:O,O-Diisopropyl-S-benzylthiophosphate


Aquamicron CXU 10ml


Sample Quantity(g)


Moisture Content(%)

TPN (Daconil)Zineb (Diefar)NamekatCaptanBryeslin powder

100110110110150

0.48670.10210.13140.06790.1109

02411459660619144822

495ppm1.435.032.824.35

Captan: N-Trichloromethylthio-4-cyclohexene-1,2-dicarboximideTPN: TetrachloroisophthalonitrileZineb: Zinc ethylenebisdithiocarbamate

3. Glass/Ceramics

Because glass, ceramics and similar substances do not dissolve inorganic solvents, both volumetric titration and coulometric titration areused in combination with moisture vaporization. The heating temperature and other conditions for moisture vaporizationmust be determined with reference to the type of sample. Particularcare is required with glass as it will melt at certain temperatures andadhere to the sample boat used in the moisture vaporization method.Up to about 600�C, adhesion can be stopped if the boat is covered withaluminum foil. Direct titration is not possible with cement. The moisture content ofcement is chemically bonded, while the oxides in cement causeinterference by reacting with Karl Fischer reagent to produce water. Theusual method is to carry out moisture vaporization at 800-1,000�C,followed by Karl Fischer titration.

Key Points


137


Measurement Value(mg)

Moisture Content(%)

Vaporization method(%)

Porous glass powder 0.1589 2.50 1.56 1.55



Substance Heating temperature(�C)

Sample quantity(g)


Moisture Content(%)

Hydrated cement 700 0.1291 19.85 15.3

(2) Moisture vaporization - Volumetric titration Reagents used:Karl Fischer Reagent SS-Z (or SS)

Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml


Sample quantity(g)



Glass woolLead glass (powder)Fluorine glassPhosphate glassPorous glass (powder)SealerGlassCeramics (powder)IC ceramicsCementCellite (dried)

200400700800300800600130800800180

0.51270.74710.98560.27570.20622.27301.01212.54296.70100.31020.1721

196811

79285

3199339

342974

2222219

128

3820.109%

0800.103%0.155%

149034

0.117%033

0.715%743


Aquamicron CXU 10ml


138

4. Liquefied Petroleum Gases

Liquefied petroleum gases, such as propane and butane, can beadded directly to dehydrated solvents or electrolytes and subjected toKarl Fischer titration, using either the volumetric or coulometricmethods. Coulometric titration is most suitable, since liquefiedpetroleum gases usually contain only trace amounts of moisture. To obtain accurate measurements of moisture content, it is important toadd the sample in the liquid phase. In particular, allowance must bemade for a marked tendency for fluctuations in the moisture content ofsamples at around the 50ppm level. Be sure to inject the entire sampleinto the sampling bottle. For details of the methods used, refer to the LPG Testing Method Standards of the Japan LPGAssociation.

Key Points

Reference:Muroi, K. et al., "Rapid Determination of Water in LPG byKarlFischer Method" J. Japan Petroleum Institute 11, 440(1968).

Liquid-phase samples are obtained as follows. (1) Place the canister containing the gas upside-down or on an angle.

Connect a high-pressure sampling bottle to the canister outlet using ahose designed for this purpose (Figure 22).

(2) Open valves A and B of the sampling bottle. Next, gradually open thevalve on the canister, allowing a small amount of the gas to vaporize.Release the gas through the sampling bottle.

(3) Close valve B, and open the valve on the canister to release the sampleinto the sampling bottle.

Sampling Method

Note:The sample can be moved into the sampling bottle by openingand closing valve B, repeatedly. Do not fill the bottle completelywith liquid sample. Always keep the sample below 80% of thevolume and leave some vapor space.


139

(4) Close valve A and the valve on the canister. Remove the hose. Weighthe sampling bottle, and then attach a syringe needle to valve B (Figure21).

Figure 21: Sampling bottle and hose Figure 22:Obtaining a sample from agas canister

Titration Method

Coulometric titration (or volumetric titration) is carried out as follows. (1) First place 150ml of anolyte (or 100ml of general-use dehydrated

solvent) in an electrolytic cell and use coulometric titration (or KarlFischer Reagent SS-X) to remove all moisture.

(2) Introduce the syringe needle through the side port of the electrolytic cell(or titration flask) until it reaches the bottom of the cell (or titration flask),as shown in Figure 23.

Figure 23: Injecting the sample (coulometric titration)

Electrolytic cell

Aquamicron CXU

Aquamicron AX

Gas vent

Extension pipe

Syringe needle


140

(3) Gradually open valve B while stirring the anolyte (or general-usedehydrated solvent). Inject the sample for 10-15 minutes (at a rate ofabout 1g/min.).

Note:The sample will gasify as it is injected and it will escape throughthe upper vent valve into a draft chamber, or to the outside air.

(4) Withdraw the syringe from the sampling bottle. (5) Weigh the sampling bottle. Subtract this weight from the weight before

the injection of the sample to determine the weight of the sample. (6) Titrate the moisture absorbed into the anolyte (or general-use

dehydrated solvent) to the end point, using coulometric titration(volumetric titration).

(7) Calculate the moisture content using the following formulae. For coulometric titration:

Moisture content (ppm) = measurement value (µg)/sample quantity (g)

For volumetric titration


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX (or MS) 100ml


Aquamicron CXU 10ml


Titration quantity (mg)

Moisture content (ppm)

LPGPropaneMethyl chlorideVinyl chlorideSulfur dioxideAerosol

25.129.018.315.753.127.4

1.401.114.957.4117.61.18

5638

27147533135

Moisture content (ppm) = Titration volume(ml)�Titer(mgH2O/ml)

sample quantlty (g)�1000 �100


141




Titration quantity (µg)

Moisture content (ppm)

LPGEthylenePropaneButadieneFlon gas R113Spray cans

23.2440.06 L6.50

16.637.976.26

25355

280120234

1008

111.7

437.2

29161

5. Coals, Tars

The moisture content of coals is normally measured using a moisturevaporization system. Measurements can be obtained using eithervolumetric or coulometric titration. Tars are subjected to Karl Fischer titration using the moisturevaporization system designed for oils.

Key Points


Sample Quantity(g)


Moisture Content(%)

Brown coalCoal tar

General-useOil-type

0.03890.1619

4.387.30

11.304.5


Sample Quantity(g)


Moisture Content(%)

Powdered coal 150 0.1262 5.76 4.56

(2) Moisture vaporization - Volumetric titration Reagents used: Karl Fischer Reagent SS-X (or SS)



142


Sample Quantity(g)


Moisture Content(%)

Brown coalPowdered coalCoal tarCokePitch tar

110130150500180

0.04970.25090.11140.04480.4892

5456118847181813335

11.00.4734.244.05

685ppm


Aquamicron CXU 10ml


143

6. Petroleum Products

Karl Fischer titration is an excellent method for the measurement oftrace moisture in petroleum products. Karl Fischer titration has been thestandard test method for the Petroleum Society since 1976, and itbecame a Japan Industrial Standard in 1982. As moisture is generally present only in trace quantities in petroleumproducts, coulometric titration is presently in widespread use.Coulometric titration is carried out by adding a sample, such asinsulating oil, refrigerating machine oil, transformer oil, kerosene ordiesel oil, to an electrolyte. The sample is added 5-10ml at a time. Though some substances fail todissolve and may cloud the solution, their moisture content can bemeasured once they are thoroughly dispersed. For volumetric titration, the substance is dissolved in a dehydratedsolvent formulated for oils. Karl Fischer titration can then be carried outdirectly. Silicon oils can be titrated directly by adding samples to aketone-type dehydrated solvent. Some additives, such as antioxidants, cause interference reactions withKarl Fischer reagent. If lubricants (e.g. gasoline engine oils and dieselengine oils) and other products contain such substances, Karl Fischertitration must be carried out using an oil-type moisture vaporizationsystem. Dissolve greases that do not contain interference substances in oil-typedehydrated solvent and titrate directly. For those that do containinterference substances, Karl Fischer titration should be carried outindirectly using a moisture vaporization system. Petroleum products occasionally contain trace amounts of mercaptanor hydrogen sulfide. These react with Karl Fischer reagent. They reactquantitatively with iodine on a mole for mole basis, however, soprovided that the amount of mercaptan or the hydrogen sulfide contentis known, moisture content can be determined accurately throughadjustment of the titration result.

2RSH+I2 � 2RSSR+2HIH2S+I2 � 2S+HI

As shown in the above formulae, 1ppm of sulfur in mercaptan orhydrogen sulfide is equivalent to 0.28ppm and 0.56ppm of moisturecontent, respectively.

Key Points


144



Substance Dehydrated solvents Sample Quantity(g)



Industrial gasoline Oil-type 20.0 0.42 21

Aviation gasoline " 20.0 0.30 15

Kerosene " 20.0 1.22 61

Diesel oil " 20.0 1.66 83

Heavy oil " 1.0805 27.88 2.58%

Crude oil " 1.5023 5.41 0.360%

Transformer oil " 20.0 0.52 26

Refrigerating machine oil " 20.0 1.24 62

Rust preventive oil " 20.0 1.80 90

Compressor oil " 15.0 3.60 240

Air filter oil " 20.0 1.96 98

Heat treatment oil " 20.0 1.10 55

Hydraulic oil " 20.0 0.30 15

Rolling oil " 20.0 1.08 54

Hydraulic actuation oil " 20.0 0.84 42

Rotary pump oil " 30.0 0.30 10

Aviation oil " 15.0 1.50 100

Fluoride oil " 20.0 0.34 17

Liquid paraffin " 30.0 0.45 15

Asphalt " 5.0 0.95 190

Cutting oil " 15.0 1.58 105

Grinding oil " 15.0 2.01 134

Wax " 0.1001 4.72 4.72%

Brake oil General-use 1.0555 1.27 0.120%


145







Sample Quantity(g)


Moisture Content(%)

[Insulating oil]Mineral oil Oil-type 8.8431 0.20 23

Alkylbenzene 2-1 " 8.5784 0.17 20

Alkylbenzene 2-2 " 8.7058 0.55 63

Alkylbenzene 2-3 " 8.3116 0.23 28

Polybutene 3-1 " 8.1933 0.14 17

Polybutene 3-2 " 6.8850 0.19 28

Polybutene 3-3 " 5.9730 0.11 18

Alkyl naphthalene 4-1 " 9.2462 0.15 16

Alkyl naphthalene 4-2 " 9.3594 0.14 15

Alkyl diphenyl ethane " 9.4135 0.38 40

Silicon oil Ketone-type 9.6343 0.37 38

Gasoline engine oilDiesel engine oilMarine engine oilMarine cylinder oilCap grease JIS 1-1

JIS 2-2Fiber greases JIS 2-3

JIS 2-4Graphite greases JIS 1-1

JIS 2-1

150150150150120140140140140120

4.37935.51455.49985.45651.08651.07761.01121.05231.05191.0219

0.660.941.041.912.394.200.390.431.891.11

0.0150.0170.0190.0350.2200.3900.0390.0410.1800.109


Aquamicron CXU 5ml


146




Gasoline 3.9353 351 89Naphtha 0.7280 117 161Kerosene 0.7940 27 34Heavy oil 4.4103 286 65Rolling oil 4.3029 233 54Aviation oil 2.5869 270 104Refrigerating machine oil 2.4350 101 42Actuation oil 4.2943 387 90Brake oil 2.9758 904 304Liquid paraffin 8.6600 130 15Electric insulating oils 4.1460 77 19Alkylbenzene 4.3132 73 17


Aquamicron CXU 10ml


Sample Quantity(g)



Diesel oil 130 4.0973 241 59Heavy oil 110 4.4278 290 66C heavy oil 150 0.3820 2188 0.573%Mineral oil 130 4.5434 273 60Turbine oil 130 8.4001 296 35Rolling oil 110 4.3029 233 54Aviation oil 130 3.3879 328 97Engine oil 130 0.9133 908 994Gasoline engine oil 180 4.6133 168 36Diesel engine oil 130 4.3132 1298 301Gear oil 130 2.6322 244 93Cutting oil 150 1.7824 134 75Actuation oil 130 4.2394 98 23Grinding oil 150 1.7166 186 108Turbine oil 130 4.4632 149 33Brake fluid 150 2.9758 904 304Hydraulic oil 130 4.3793 392 90Rust preventive oil 130 1.7590 532 303Machine oil (paraffin) 130 4.3941 263 60Machine oil (naphthene) 130 4.5122 274 61Crude oil 130 0.4156 1506 0.362%Wax 150 0.7235 8 11


147

7. Plastics

Plastics reach high temperatures during the molding process and traceamounts of moisture can cause bubbling or seriously affect theperformance of a plastic by reducing its molecular weight throughpyrolysis. This means that moisture management is a very importantaspect of the drying processes for plastics. Karl Fischer titration is theideal method for measuring trace moisture content in plastics. Themoisture vaporization method permits accurate and relatively fast (10-30 minutes) determination of moisture content.When using the moisture vaporization method, it is important to set theheating temperature with reference to the type of plastic. The optimaltemperature range must be determined for each plastic. The generallyaccepted view is that plastics should be heated to around meltingpoint. Figure 24 provides guidelines on the appropriate heatingtemperatures

Key Points

[If the analytical result is low]

If the heating temperature is too low, moisture vaporization will be delayedand the analytical time will be longer. The measurement process may endbefore the moisture has been vaporized, leading to a low analytical result.The result may also be low if vaporized moisture is absorbed by additives ordegraded plastic constituents that have condensed in the tubes of themoisture vaporization system.

[If the analytical result is high]

Plastics that contain OH bases, such as polyvinyl alcohol, phenol resin andpolyvinyl acetate, may produce high readings if the heating temperature istoo high. It may be impossible to complete titration in some cases. Suchphenomena appear to be caused by the formation of water through heating.Moisture content of urea resin cannot be measured normally at temperaturesabove 120�C because ammonia produced through the breakdown of urearesins reacts with iodine. Melamine resins appear to cause interference inthe same way.


148

Reference: Kato, H. et al.: Kobunshi Kako, 35, 584 (1986).Muroi, K. et al.: Bunseki Kagaku, 11, 351 (1962).

Figure 24: Optimal Moisture Vaporization Temperature Ranges for Plastics

Ionomer resins

Polymethyl methacrylate

Urethane resins 183

Epoxy resins 120-150

ABS resins

6-Nylon 225

6,6-Nylon 267

Urea resins

Phenol resins

Low-density polyethylene 108-120

Polyethylene terephthalate 248-260

Polybutylene terephthalate 218-219

Polyvinyl chloride 200-210

Polyoxymethylene 175-180

Polycarbonate 222-230

Polystyrene 230

Polypropylene 168-170

Polyvinyl alcohol 245

Polyvinyl butyral

Melamine resin

Polytetrafluoroethylene 320-330

Polyimide

Ethylene-vinyl acetate copolymers

Sample Meltingpoint (�C)

Heating temperature (�C)120 160 200 240 280

Polyethylene 180 3.7702 67 18Cross-linked polyethylene 180 1.2786 145 113Polypropylene 160 2.3185 97 42Vinyl chloride 130 0.9815 412 420Vinyl acetate 130 1.5925 1549 973Ethylene vinyl acetate copolymer 180 0.4743 1005 0.212%Polyvinyl alcohol 150 0.1392 3739 269Polyvinyl butyral 180 0.5641 1486 0.263%Polystyrene 180 2.7896 965 345Styrol foam 130 0.2892 218 753Polyester 230 2.4615 512 208PET 230 4.6003 171 37PBT 250 1.2020 223 186Polycarbonate 250 1.0830 972 898Polyacetal 200 1.5227 2181 0.143%Phenol resins 200 0.1142 5227 4.58%6-Nylon 230 0.2211 3007 1.36%6,6-Nylon 250 0.0492 1200 2.44%Metacrylic resins 250 1.6017 1337 835ABS resins 200 0.8455 2073 0.245%Urea resins 110 0.4898 3587 0.732%Fluorine resins 160 2.4470 18 7Epoxy resins 120 0.4142 2360 0.570%Polyol 150 1.0286 1258 0.122%Urethane 180 1.4886 3136 0.211%


149




Sample Quantity(g)



8. Rubber, Rubber Products, Compounding Agents

The qualities of rubber are adversely affected by the presence ofmoisture in raw materials or in compounding agents. Moisture contentcan be measured accurately, quickly (10-20 minutes) and convenientlyby combining moisture vaporization with coulometric titration.

Key Points


150

Hints: 1. The sample should weigh between 0.5g and 1g. 2. The heating temperature for moisture vaporization should be 130-200�C.Direct titration is not possible with vulcanization accelerators andantioxidants as these react with Karl Fischer reagent to release iodine.The moisture content of carbon black cannot be measured throughdirect titration as the end point cannot be determined.

Reference: Muroi, K. et al.: Journal of Japan Rubber Institute, 52, 61(1979).




Sample Quantity(g)


Moisture Content(%)

[Rubber]NBR (nitrile-butadiene rubber) 150 0.8001 2554 000.319SBR (styrene--butadiene rubber) 150 1.2264 0475 387ppmCR (chloroprene rubber) 130 1.4352 1148 800ppmButyl rubber 150 1.9435 0894 460ppmSilicon rubber 200 0.1657 2081 001.25EPR (ethylene propylene rubber) 180 3.4106 1001 293ppmNatural rubber 150 0.6374 1734 000.272[Rubber products]Rubber caps 150 0.6121 3158 000.516Power cable rubber 130 0.0977 0871 000.892Oil seal rubber 150 0.3228 1661 000.515Tire rubber 200 0.5031 2635 000.524Silicon rubber 200 0.4937 1199 000.243


151

Reference: Muroi, K. et al.: Journal of Japan Rubber Institute, 52, 61(1979).

Figure 25: Optimal Heating Temperature Range for Raw Rubber andCompounding Agents

Raw rubber

NR

SBR

BR

CR

NBR

Vulcanization accelerants

OBS

D

DM

CZ

TT

Antioxidants

DMBPPD

IPPD

Stearic acid

Zinc oxide

Paraffin wax

Carbon black

Sulfur

Process oil

SampleHeating temperature (°C)

80 100 120 130 150 160 180 200


152

9. Fibers, Papers

Because samples of fibers and paper do not dissolve in dehydratedsolvent, moisture content is measured using moisture vaporizationfollowed by Karl Fischer titration (volumetric or coulometric). A heating temperature of 130-150�C is appropriate for moisturevaporization. Moisture content in samples of these substances typicallyreaches several per cent. The following guidelines are suggested forsample quantities. 1) Volumetric titration: 0.5g 2) Coulometric titration: 0.05-0.1g

Key Points

Reference: Muroi, K. et al., "Determination of Water Content in ElectricInsulating Papers by the Karl Fischer Method" in BunsekiKagaku 30, 624 (1981).

[Examples of Measurement](1) Moisture vaporization - Volumetric titration

Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml


Aquamicron CXU 10ml


Sample Quantity(g)


Moisture Content(%)

Bakelite paperCondenser paperPressed board paperFilter paper

150150150230

0.51110.49550.66460.1700

34.7036.7449.2908.82

6.807.427.425.19


153

10. Dyestuff Intermediates

Many dyestuff intermediates are solids and must be dissolved insolvents. Most Japanese Industrial Standards stipulate volumetrictitration. These standards should be taken into account when settingconditions for the moisture content test methods that should be usedwith individual compounds. To raise the solubility of specific substances in the dehydrated solventused for the volumetric titration, it may be necessary to add othersolvents, such as those listed below, to the methanol. It should also benoted that special solvents are sometimes used with amines.

Volumetric titration solvents and the main compounds for which theyare used1) Dehydrated Solvent MS (or GEX)2) Dehydrated Solvent CP : anilines, o-anisidines, p-cresidines, p -

chloroanilinesCP+acetic acid : p-anisidines, p-phenetidines,m-aminophenols

3) Dehydrated Solvent PE : Peri acid

Key Points


Sample Quantity(g)


Moisture Content(%)

Kraft paper 150 0.0663 3840 5.79Synthetic paper 150 0.0563 2910 5.17Woodfree paper 150 0.0201 0722 3.59Machine-made paper 150 0.0948 4793 5.06Photocopy paper 150 0.0665 3099 4.66Oil paper 180 0.0526 3160 6.01Paper tape 150 0.2057 4892 2.38Cellotape 150 0.0741 6975 9.41Copy paper 150 0.8160 2553 0.313Cellulose (paper) 150 0.0500 3057 6.11Acrylic fibers 110 0.2396 2653 1.07Polyester 180 0.2177 0430 0.198Chemical fibers 180 0.0497 2596 5.22Wool 150 0.0838 7225 8.62Absorbent cotton 150 0.0631 4379 6.94


154

4) Dehydrated Solvent MS+pyridine : metanilic acid, o-toluenesulfonamide, C-acids

5) Dehydrated Solvent MS+dichloromethane : nitro compounds, some chloro compounds

Coulometric titration can be used. However, interference reactionsmake it unsuitable for some substances (* e.g. anilines and otherelectrode-reactive substances).

Substances for which coulometric titration cannot be usedAnilines, p-anisidines, m-aminophenols, p-chloroanilines, p-toluidines,metanilic acid


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX, KT (or MS, CP) 25-50ml




p-Toluidines CP+acetic acid (2:1) 2.9253 0.89 304p-Anisidines " 2.0115 0.46 229p-Phenetidines " 1.1072 1.68 0.152%m-Aminophenols " 1.0152 0.29 286Anthranilic acid General-use 1.0164 0.11 108Diphenyl amine " 8.3429 0.25 302-Aminonaphthalene " 0.5290 1.62 0.306%-1-sulfonic acidSodium naphthionate " 0.0593 13.45 22.7J-acid " 0.1051 5.88 5.60%Carbonyl J-acid " 0.2062 6.15 2.98%m-Nitroaniline " 1.5089 0.95 630p-Nitrophenol " 0.9844 11.30 1.15%1-Hydroxy-2-naphthoicacid " 2.0959 0.54 258Anilines Ketone-type 2.1601 1.92 8895-Amino-2-chlorotoluene MS+pyridine (5:1) 1.9911 0.09 45-4-sulfonate(C-acid)


155


Aquamicron CXU 5ml

Anthranilic acid General-use 1.1934 370 310Diphenyl amine " 4.0630 104 0262-Aminonaphthalene-1- " 0.5500 1721 0.313%sulfonic acid(Tobias acid)Sodium naphthionate " 0.0514 11653 22.7%8-Amino-2-naphthalene " 0.0561 4260 7.59%sulfonic acid(Peri acid)m-Aminophenol Ketone-type 0.4592 117 255

Substance Electrolyte Sample Quantity(g)




Sample Quantity(g)


Moisture Content(%)

11. Pigments

Most pigments are insoluble in titration solvents and cannot be titrateddirectly. In particular, direct titration should be avoided with inorganicpigments which react with Karl Fischer reagent. The moisture content of any pigment can be measured quickly (10-30minutes) and accurately using the conventional drying method basedon moisture vaporization. Either volumetric or coulometric titration canbe used, depending on the moisture content.

Key Points



Zinc white 300 3.1135 3.73 0.120Titanium oxide 200 1.0405 4.16 0.400Prussian blue 200 0.4002 22.17 5.540Red iron oxide 300 3.0021 10.21 0.340Chrome yellow 300 2.9988 8.40 0.280Aluminum powder 400 5.0211 1.00 199ppmAntimony oxide 300 3.5011 3.85 0.110Calcium carbonate 100 2.1111 10.77 0.510

" 600 1.0050 16.18 1.610Barium carbonate 500 3.1009 4.03 0.130


156


Sample Quantity(g)


Moisture Content(%)

Cuprous oxide

"Titanium oxideYellow pigmentRed pigmentBarium carbonate

230700200230200500

0.36510.14971.03780.19490.04153.1009

295919533631202823704.30

0.8101.3000.3501.0405.7100.130


Aquamicron CXU 10ml

12. Paints

Moisture content in paints causes bubbling, condensation and lumps inpainted surfaces. Moisture measurement is, therefore, very importantfor quality management. Drying methods cannot be used as there is a risk that other constituentswill vaporize with the water. Distillation is also unsuitable because ittakes too long, and because many paints include hydrophilicsubstances that are difficult to separate. As a result, Karl Fischertitration has been chosen as the moisture measurement method forpaints and it is stipulated as a Japanese industrial Standard (K5407).Paints include a variety of film-forming substances as well as variousother ingredients such as enamels with pigments and varnishes, someof which may react with Karl Fischer reagent. The possibility that some of these substances will cause an interferencereaction is something that must be checked in advance. JIS K5407 (testing method for paint constituents) stipulates bothvolumetric and coulometric titration. The level of moisture content inpaints is generally within the range for either method. If a productcontains a number of substances that will not dissolve in solvents,volumetric titration should be used in preference to coulometric titration. For volumetric titration, the sample must be dissolved or dispersed in asuitable solvent in preparation for Karl Fischer titration. A ketone-typedehydrated solvent is excellent for samples that contain ketones. If asample contains other substances that cause interference reactions,Karl Fischer titration should be used in combination with moisturevaporization. Either volumetric or coulometric titration can be used in

Key Points


157


Sample Quantity(g)


Moisture Content(%)

EnamelPaintsLacquer paintPowder paintEpoxy resin paintFluoroethylene resin paintPolyester paintLiquid varnishMelamine varnish

150130200180150180150300110

0.13881.31750.06500.45132.21011.05070.19310.11220.1894

190207422798139514541170097819341324

1.37563ppm

4.300.309

658ppm0.1110.5061.73

0.699


Sample Quantity(g)


Moisture Content(%)

Epoxy resin paints Oil-type 0.6645 0.43 647ppmFluoroethylene resin paints " 1.0017 1.11 0.111Paints " 0.9953 4.97 0.499Paint thinners (incl.MEK) Ketone-type 4.8894 4.33 886ppmMelamine varnish " 0.1504 1.09 0.725

such cases. Because of the high viscosity of most paints, it is difficult to obtain asample and inject it into a titration cell. Select equipment that matchesthe characteristics of the sample, such as a thick needle (2mmdiameter), a sampling spoon or a glass rod. (now, JIS K5407 is abolished.)


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent OL II, KT (or CM, CP) 25-50ml


Aquamicron CXU 10ml


158

13. Printing Inks and Imaging Materials

Volumetric titration is used for printing inks and imaging materials. Inksin particular may have a high moisture content. Samples can beobtained in small quantities and directly dissolved or dispersed indehydrated solvent for Karl Fischer titration. Coulometric titration iscommonly used in conjunction with moisture vaporization for samplesthat cannot be dissolved in solvent or that contain interferencesubstances. Because of the high viscosity of many inks, it may be difficult to obtain asample and inject it into a titration cell. Select equipment that matchesthe characteristics of the sample, such as a thick needle (2mmdiameter), a sampling spoon or a glass rod.

Key Points


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX, KTX, OL II (or MS, CP, CM) 25-50ml

Printing ink General-use 0.4511 5.85 1.30Offset ink Oil-type 1.0834 4.33 0.400Metallic ink " 0.3172 1.66 0.523Oil-based ink " 0.1768 22.83 12.9Water-based ink " 0.0209 17.51 83.8Emulsion ink " 0.0561 31.75 56.6Inkjet ink " 0.0372 27.34 73.5Gravure ink Ketone-type 0.4125 1.38 0.335[Printing ink pigment]Carmine 6B Oil-type 0.4606 3.28 0.712Lake red " 0.4174 0.71 0.170Copper phthalophenone yellow " 0.5640 0.74 0.131Benzidine yellow " 0.6273 0.74 0.118[Ink raw materials]Acrylates General-use 0.6104 1.54 0.252Epoxy resins Oil-type 0.8443 4.80 0.569Phenolic novolak " 0.7655 3.87 0.506Photosensitive resins " 0.0315 6.90 21.9Toners Ketone-type 0.1374 1.02 0.742


Sample Quantity(g)


Moisture Content(%)


159

14. Adhesives

The moisture content of adhesives ranges from minute to high, so bothvolumetric and coulometric titration are used. For volumetric titration,the sample is dissolved or dispersed in a suitable solvent. Moisturevaporization is used for substances that are totally insoluble. Coulometric titration can be carried out directly in the case ofsubstances that dissolve in electrolytes. Moisture vaporization is usedfor samples that are even slightly insoluble. Adhesives are very viscous and instant adhesives solidify quickly whenexposed to air. Because of these and other characteristics, a number ofsamples are very difficult to handle and sampling equipment must beselected with reference to the attributes of each sample. If the viscosityof the product allows it to be sampled in a syringe, use a thick needle(2mm diameter). For substances with higher viscosity, use a samplingspoon or glass rod. Special procedures are needed for instantadhesives. Refer to the following document.

Key Points

(2) Moisture vaporization - Volumetric titration Reagents used: Karl Fischer Reagent SS-Z (or SS)



Sample Quantity(g)


Moisture Content(%)

Emulsion inksWater-based ball-pen inks

200200

0.06260.0338

34.7818.68

55.755.3

Reference: Muroi, K. et al., "Determination of Minute Traces of Water inCyanoacrylate Adhesive Compositions by the Coulmetric KarlFischer Titration Method Using the Anodic Electrolytic forKetones" in Journal of the Japan Adhesive Society 21, 186(1985).


160


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent OL II, KTX (or CM, CP) 25-50ml


Sample Quantity(g)


Moisture Content(%)

Porcelain adhesivesAluminum adhesivesWoodworking bondsConstruction puttiesRubber-metal adhesivesAdhesives

Oil-type

"""

Ketone-type

"

1.50010.55080.07850.23240.68834.4427

1.653.7546.701.783.140.79

00.11000.68159.50000.76600.456

178ppm




Sample Quantity(g)


Moisture Content(%)

PastesWoodworking bondsConstruction putties

150200250

0.49600.05460.8479

01.5932.2402.33

00.32159.10000.275

Substance Electrolyte Sample Quantity(g)



Epoxy resinsIsocyanate hardenersBondsCyanoacrylatesAdhesives

General-use

""

ketone-type

"

0.51121.53680.94031.97862.3736

1507098524430430

295064557217181

(3) Coulometric titration Reagents used: Aquamicron AX (or AS), AKX 100ml

Aquamicron CXU 5ml


Aquamicron CXU 10ml


161


Sample Quantity(g)


Moisture Content(%)

Epoxy resins (powder)Isocyanates (principal)Silicon bondsAluminum adhesivesPastesPorcelain adhesivesSealing compounds

250180210200150180230

0.70740.30790.48000.26700.32300.93360.4367

1080094109091180095409641218

0.1530.3060.1890.4420.2950.1030.279

15. Soaps and Detergents

Because soaps and detergents generally have a high moisture content,volumetric titration is used. The moisture vaporization method is usedfor metallic soaps, some of which cause interference. Direct coulometric titration can be used for samples that will dissolve in electrolyte.

Key Points


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX, OL II(or MS,CM) 30-50ml


162


Sample Quantity(g)


Moisture Content(%)

Cosmetic soapSoft soapFacial soapCleansersShampooAlkyl benzene sulfonateABS detergentsLaundry detergentsHigh-grade alcohol detergentsLiquid detergentAnionic surfactantsCationic surfactantsNonionic surfactantsAmphoteric surfactantsPolyglycerine

Oil-typeGeneral-use

"""""""""""""

0.08630.21330.05490.03910.03530.25510.03450.07070.13660.04530.53233.00843.01551.02951.5572

09.6141.5910.8421.3627.6802.2926.2306.0381.4120.5410.8601.8401.4811.4305.45

11.50019.50019.80054.60078.40000.89776.00008.60059.90045.40002.040

612ppm491ppm

1.1100.350

(2) Moisture vaporization - Volumetric titration Reagents used:Karl Fischer Reagent SS-Z (or SS)



Sample Quantity(g)


Moisture Content(%)

Cosmetic soapsFacial soapsAlkyl benzene sulfonateABS detergentsLaundry detergentsCleansers

200180150130180200

0.07390.09980.18700.03030.06900.0503

07.6519.7601.6922.8005.8427.47

10.40019.80000.90476.00008.46054.600


Aquamicron CXU 5ml



Moisture Content(%)

SoapsShampoos

0.29340.0209

0131416073

00.44876.900


163


Sample Quantity(g)


Moisture Content(%)

DetergentsSoapsCleansers

180150600

0.03240.49010.0330

508415172475

15.70000.31007.500


Aquamicron CXU 10ml

16. Cosmetics

Creams, emulsions, rinses, hair tonics, lotions and other cosmeticshave high moisture content. Accordingly, volumetric titration is the mainmethod used with these items. When carrying out the volumetric titrationit is convenient to use a high-titer Karl Fischer reagent. An oil-typedehydrated solvent is used for products with a high oil content, such ascreams. A general-purpose dehydrated solvent is used for hair tonicsand lotions. Coulometric titration can also be used. However, the high moisturecontent of these products means that titration will be prolonged, evenwith small samples. For this reason, volumetric titration should be usedwhenever possible. Sampling devices should be selected carefully. Viscous products suchas creams should be sampled with a sampling spoon and dissolveddirectly in the dehydrated solvent.For lotions and similar products, asampling flask with pipette is convenient. For cosmetics that will notdissolve in dehydrated solvent, volumetric or coulometric titrationshould be used in combination with moisture vaporization.

Key Points




164

Substance Dehydrated solvents

Sample Quantity(g)


Moisture Content(%)

CreamEmulsionRinseNourishing creamCleansing creamCold creamHair tonicHair treatments

Oil-type

"""""

General-use

"

0.10720.10110.11510.02810.04540.05560.04090.0328

61.2174.6188.3912.7215.0014.0917.3316.92

57.173.876.845.333.025.342.451.6




Sample Quantity(g)


Moisture Content(%)

MascaraEssence

150150

0.02620.0660

13.5343.42

51.665.8


Sample Quantity(g)


Moisture Content(%)

Lip creamCream lotion

180180

0.07220.0180

0487113600

06.7575.60


Aquamicron CXU 5ml



Moisture Content(%)

CreamCleansing creamEmulsionCream lotion

0.03640.04160.03300.0153

23089111882861111580

63.426.986.775.7


Aquamicron CXU 10ml


165



Moisture Content(%)

Liquid crystalPhotoresist

1.05040.5578

196998

187ppm0.179

Materials for electronic equipment and electrical parts are made ofmixed or composite materials. They vary widely in terms of both the rawmaterials and their form. The methods used to measure moisturecontent must be selected with reference to the characteristics of eachitem. These items generally have a low moisture content and many areinsoluble in solvents. For this reason, moisture content is measuredusing moisture vaporization and coulometric titration. Chemical products such as liquid crystals, photoresists and capacitorelectrolytes can be dissolved in dehydrated solvents or electrolytes.This means that they can be titrated directly using volumetric orcoulometric titration. Chemical substances may be either liquid or solid. For viscous liquids,a syringe with a 2mm diameter needle should be used.

Key Points

17. Chemicals & Materials for Electronic Equipment and Electrical Parts



Substance Dehydrated solvents

Sample Quantity(g)


Moisture Content(%)

Capacitor electrolyteLiquid crystalPhotoresist

General-use

"Oil-type

0.04541.09981.0823

3.670.233.23

8.080209ppm

0.298


Aquamicron CXU 5ml


166


Aquamicron CXU 10ml


Sample Quantity(g)


Moisture Content(%)

Liquid crystalPhotoresistCapacitorIC chipSilicon waferPrinted circuit boardPolycarbonate disk

180180260250700200230

2.23031.76530.11940.68724.11670.09760.4430

0248033402171709002913030678

111ppm189ppm

0.1820.249

007ppm1.3400.153


167

III-2. Foodstuffs

The food category encompasses a wide range of substances with varyingproperties. It includes agricultural, livestock and marine products and processedproducts, as well as food additives. The moisture content of these items alsovaries widely. It is necessary, therefore, to select the most appropriatesample handling procedures and measurement method for each individualproduct. Test methods for foodstuffs are mostly stipulated in the JAS standards. Inmost cases moisture content is measured using heating and dryingmethods, but Karl Fischer titration is specified for some items. In the case ofchemically defined foodstuffs, such as sugars and additives, Karl Fischertitration can be applied using the same methods as for normal chemicals. Food items with complex structures, such as cereals and meats, contain notonly adhesion moisture but also moisture incorporated within cells.Measurement results for these items are provided for your information. Because many food items do not dissolve in organic solvents, the moisturevaporization method is used extensively. However, foodstuffs commonlybecome unstable when heated, and water may be formed as substancesbreak down. Care must be taken, therefore, when setting analyticalconditions.

Food additives are substances used in the manufacture, processingand preservation of foodstuffs. There are many types with varyingattributes. Most are solid, but those that dissolve in dehydrated solventsor electrolytes can be titrated directly using Karl Fischer titration.However, it is necessary first to determine whether or not interferencesubstances are present. Direct titration should be avoided in the caseof insoluble substances, and the moisture vaporization method isrecommended. As the moisture content of these substances isgenerally high, volumetric titration is used. However, coulometric titration can also be used if the sample quantity iskept small. When using moisture vaporization, it is necessary to set themeasurement conditions after determination of the heating temperature.Official specifications for food additives commonly stipulate the loss-on-drying method, so conformance with that method should be checked.

Key Points

1. Food Additives and Flavorings

III-2. Foodstuffs

168


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX, SU (or MS, FM) 25-50ml


Sample Quantity(g)


Moisture Content(%)

[Flavorings]Flavor General-use 0.0228 10.93 48.0Orange powder " 0.2623 5.01 1.91Palm lemon Sugar-type 0.0765 7.08 9.25Strawberry powder " 0.2789 3.69 1.33[Condiments]Sodium citrate General-use 0.1711 20.97 12.3Sodium 5'-inosinate Sugar-type 0.0802 20.65 25.7Sodium glutamate " 0.1303 13.38 10.3Yeast extract " 0.0810 2.84 3.65[Emulsifiers]Sorbitan fatty acid ester General-use 2.0962 2.95 0.141[Sweeteners]Potassium glycyl rhizinate General-use 0.1652 12.45 7.54Maltitol Sugar-type 0.1891 25.77 13.6Sorbit " 0.4317 2.71 0.628Aspartame " 0.0535 1.33 2.49[Preservatives]Sorbic acid General-use 1.0059 1.14 0.113Potassium sorbate " 1.0489 0.53 505ppmSodium benzoate " 1.0787 6.89 0.639[Strengtheners]Thiamine hydrochloride General-use 0.2321 9.89 4.26Calcium lactate Sugar-type 0.0475 13.75 28.9[Acidulants]Malic acid General-use 1.0382 2.52 0.243Citric acid " 0.1044 9.23 8.84[Water-retaining emulsifying stabilizer]Sodium chondroitin sulfate Sugar-type 0.0483 4.49 9.30


169


Sample Quantity(g)


Moisture Content(%)

[Flavorings] Cheese powder 130 0.1915 12.34 6.44Vanilla powder 130 0.1161 4.70 4.05Yoghurt powder 130 0.0984 8.47 8.61Strawberry powder 050 0.3188 4.25 1.33Orange powder 150 0.2943 6.01 2.04Palm lemon 180 0.0630 5.68 9.02[Strengtheners]Calcium lactate 200 0.0513 14.50 28.3

(2) Moisture vaporization - Volumetric titration Reagents used: Aquamicron SS-Z (or SS)150ml



Aquamicron CXU 5ml



Moisture Content(%)

Sodium 5'-inosinateSodium citrateSorbic acidPotassium sorbateSodium benzoateMalic acidSaccharin

0.05240.07850.92211.07281.01791.07280.0921

1346796491048

41164632471

12813

25.712.3

0.114383ppm

0.6350.230

13.9


Aquamicron CXU 10ml

III-2. Foodstuffs

170


Sample Quantity(g)


Moisture Content(%)

[Condiments]Sodium glutamate 80 1.1071 358 323ppmSodium glutamate 180 0.0484 4739 9.79Disodium succinate 120 0.0536 21575 40.3Trisodium citrate 200 0.1071 13056 12.2Yeast extract 80 0.0391 1446 3.70Sodium 5'-guanylate 200 0.0249 4744 19.1Sodium 5'-inosinate 200 0.0165 4256 25.8[Sweeteners]Saccharin 150 0.0648 8869 13.7Aspartame 150 0.0426 1001 2.35[Preservatives]Sorbic acid 160 1.0252 3495 0.341Potassium sorbate 160 1.0139 341 336ppmSodium benzoate 160 1.0259 6456 0.629[Strengtheners]Calcium citrate 150 0.0940 12257 13.0[Acidulants]Malic acid 105 1.0389 2132 0.205[Quality enhancers]Sodium polyphosphate 130 2.0194 4988 0.247[Water-retaining emulsifying stabilizer]Sodium chondroitin sulfate 150 0.0440 4182 9.50


171

Volumetric titration is suitable for cereals and starches which have ahigh moisture content (approximately 10%). If the sample is in powderform it can be dispersed in dehydrated solvent, allowing the moisturecontent to be extracted for direct Karl Fischer titration. When using adehydrated solvent with sugars, solubility is sometimes enhanced if thetemperature is raised to 40-45�C before titration. The moisturevaporization method is suitable for the many items that do not dissolvein solvents. Care needs to be taken with the heating temperature formoisture vaporization. Temperatures in the 130-180�C range arecommonly used. High temperatures may cause various phenomena,including discoloration, abnormal results or failure to reach an endpoint. In such cases the measurement must be repeated at a lowertemperature. Moisture vaporization should be used with coulometric titration. Cerealscannot be titrated directly as they do not dissolve in electrolytes. Cereals are sometimes sampled after preliminary processing (e.g.pulverization). Care is needed to avoid moisture vaporization or absorption duringthese processes. Volumetric titration is the principal method used for dried vegetables.The sample is added to the dehydrated solvent and stirred well for aperiod of 5-10 minutes before direct titration. Moisture vaporization isused when the moisture content cannot be fully extracted from samplesin this way. Karl Fischer titration can be carried out using either thevolumetric or coulometric methods. As moisture content tends to behigh, however, volumetric titration is usually preferable. The precautions stipulated for moisture vaporization in connection withcereals also apply to dried vegetables.

Key Points

2. Cereals and Dried Vegetables



III-2. Foodstuffs

172


Sample Quantity(g)


Moisture Content(%)

Apple powderDried carrot powderDried onionsDried tomato powderSweet potato starchCorn flourSoy proteinCorn starchWheatSoy proteinSoy flourPotato powder

General-use

""""""Sugar-type

"""Sugar-type (45�C)

0.09890.12310.03660.13090.18850.06270.05740.16120.06350.07560.06920.0721

2.163.742.813.07

31.106.064.09

21.159.055.435.265.80

2.193.047.682.35

16.509.677.13

13.1014.30

7.187.608.04




Sample Quantity(g)


Moisture Content(%)

Corn starchMaizeWheat flourCorn flourDevil's-tongue flourApple powderDried onions Soy flour

150130180180130110070150

0.11030.05290.08260.14210.12700.16470.04570.0719

13.776.34

13.1053.6511.30

3.603.445.33

12.512.015.937.88.902.197.537.41


Sample Quantity(g)


Moisture Content(%)

Corn starchWheatMaltMaizeWheat flourSoy proteinPotato powder

150150110150130150110

0.04900.05240.07640.04820.06590.04630.0602

6409749845307009638233374876

13.1014.30

5.9314.50

9.687.218.10


Aquamicron CXU 10ml


173

Sugars are dissolved in a sugar-type dehydrated solvent and titrated.Volumetric titration is used. If a substance is slow or difficult to dissolvethe solvent can be heated (up to 50�C) and titrated. (If the temperatureexceeds 50�C the formamide in the sugar-type dehydrated solvent willgradually break down. The Karl Fischer reagent will be consumed insmall amounts leading to uncertainty about the end point.) Condiments are normally dispersed in general-use dehydrated solvent.This is followed by extraction and titration. If the ingredients of aparticular item give it a high sugar content, a sugar-type dehydratedsolvent is used. An oil-type dehydrated solvent is used for products witha high fat content. Moisture vaporization should generally be avoided for sugars as thesetend to break down when heated. Moisture vaporization is unnecessaryfor condiments, since in almost all cases moisture content can bemeasured using direct titration. When using the moisture vaporizationmethod the optimal heating temperature must be determined first.Changes in the sample could lead to errors.

Key Points

3. Sugars and Condiments


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX, SU, OL II (or MS, FM) 25-50ml


Sample Quantity(g)


Moisture Content(%)

Wasabi paste General-use 0.0465 10.23 22.0Roast meat gravy " 0.0187 10.66 57.0Soy sauce " 0.0265 17.55 66.2Soup powder " 0.0754 2.89 3.83Bonito stock " 0.1475 7.48 5.07Sugar syrup " 0.0691 40.56 58.7Powdered miso " 0.1228 3.79 3.09Glucose Sugar-type 1.1052 1.64 0.148White sugar " 0.2550 3.51 1.38Maltose " 0.0695 3.56 5.12Malt syrup " 0.0505 12.49 24.9Soup " 0.0322 19.87 61.7Refined sugar Sugar-type (40�C) 0.4729 4.04 0.854Soup stock Sugar-type (40�C) 0.4363 5.66 4.22Granulated sugar Sugar-type (45�C) 2.8133 0.71 252ppmMayonnaise Oil-type 0.1425 28.93 20.3

III-2. Foodstuffs

174




Sample Quantity(g)


Moisture Content(%)

Soup powderWasabi pasteSoy sauceMayonnaise

090110200200

0.08240.05220.03990.1408

03.7011.6824.0728.61

04.4922.4060.3020.30


Sample Quantity(g)


Moisture Content(%)

SugarSpices

130130

0.48530.0412

36695830

01.9814.20


Aquamicron CXU 10ml

Because sugar is the main ingredient of confectionery, these items aredissolved in a sugar-type dehydrated solvent for titration. Volumetrictitration is used.Coulometric titration is normally avoided as these products will notdissolve in electrolytes. The moisture vaporization method is also insome cases unsuitable as heating causes sugars to break down andproduce water. Caramels, candies and similar items are titrated after they have beendissolved in a sugar-type dehydrated solvent that has been heated (upto 45�C). (If the temperature exceeds 45�C the formamide in the sugar-type dehydrated solvent will gradually break down. The Karl Fischerreagent will be consumed in small amounts and this will lead touncertainty about the end point.) The moisture vaporization method canbe used for snack-type confectionery.

Key Points

4. Confectionery


175


Sample Quantity(g)


Moisture Content(%)

Potato chipsBiscuitsCorn snacks

130130130

0.18140.38210.2462

3.7312.723.44

2.063.331.40


Sample Quantity(g)


Moisture Content(%)

Small rice crackers 130 0.0377 2776 7.36


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent SU (or FM) at 40�C 25-50ml



Moisture Content(%)

Malt syrupCandyDropsMilk caramelCream caramelChocolateWafersChocolate creamChocolate emulsifierChewing gumCorn snack

0.05050.18930.26740.28690.12060.31530.55000.09990.25270.29780.2217

12.595.785.77

23.429.933.18

12.7612.135.835.633.24

24.903.052.168.168.241.012.32

12.102.311.891.46




Aquamicron CXU 10ml

III-2. Foodstuffs

176

Because of their high moisture content, most dairy products are titrateddirectly using the volumetric method. A sugar-type dehydrated solventis normally used as the titration solvent. However, products that havefats as their principal ingredients, such as butter, are dissolved in an oil-type dehydrated solvent for titration. When volumetric titration is usedfor fat products they are dissolved in an oil-type dehydrated solvent.The moisture content of vegetable oils, which contain little water, can bemeasured more accurately using coulometric titration. If a product will not dissolve readily in the electrolyte, the addition ofchloroform to the anolyte (equivalent to 20% by volume of anolyte) willallow the substance to dissolve for repeat titrations. The moisture vaporization method can be used for samples of thesetypes. However, the conditions must be determined with care. As ageneral rule, a heating temperature in the 110-180°C range is used.

Key Points

5. Dairy Products, Fat Products


Reagents used:Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX, OL II, SU (or MS, CM, FM) 25-50ml


Sample Quantity(g)


Moisture Content(%)

Powdered milk General-use 0.0572 2.64 4.56

Cream cheese " 0.0485 25.04 51.6

Natural cheese " 0.1143 72.16 63.1

Milk powder Sugar-type 1.0888 30.55 2.81

Condensed milk " 0.0730 19.42 26.6

Fresh cream " 0.1142 16.74 14.7

Powdered cheese " 0.1269 5.43 4.28

Meat extract " 0.1067 18.59 17.4

Rapeseed oil Oil-type 4.6163 0.51 110ppm

Butter " 0.0303 4.25 14.0

Margarine " 0.0970 15.49 16.0

Sugar-type dehydrated solvent should be heated to 40�C before use intitration.


177


Sample Quantity(g)


Moisture Content(%)

Cream cheeseNatural cheeseMeat extractMargarine

130130180150

0.11470.08980.07050.1281

59.1457.0012.1719.97

51.663.517.315.6




Sample Quantity(g)


Moisture Content(%)

Powdered milkCheese

110130

0.06480.0217

29538982

4.5641.4


Aquamicron CXU 10ml


Aquamicron CXU 5ml



Moisture Content(%)

Powdered milkButterCheesePalm oilSesame oilSoy bean oilSalad oil

0.20710.04220.01420.31890.90174.51182.7354

5852584558400303053400290394

02.8313.9041.10

950ppm592ppm51ppm144ppm

III-2. Foodstuffs

178


Sample Quantity(g)


Moisture Content(%)

Volumetric titration is normally used for gourmet foods because of theirhigh moisture content. They are dissolved in a sugar-type dehydratedsolvent and subjected to Karl Fischer titration. If a product will notdissolve readily the solvent can be heated to 40�C. An oil-typedehydrated solvent is used for high-fat foods. A general-purposedehydrated solvent may be used for some samples. If the moisturecontent cannot be extracted fully using these solvents, Karl Fischertitration is used in conjunction with moisture vaporization. Eithervolumetric or coulometric titration can be used in such cases. In the case of coulometric titration, direct titration should be avoidedbecause of problems with the solubility of samples.

Key Points

6. Gourmet Foods, etc.


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX, SU, OL II (or MS, FM, CM) 25-50ml

Powdered egg yolk General-use 0.0610 2.96 4.85Dried beer yeast " 0.0820 3.02 3.68Coffee Sugar-type 0.1287 3.87 3.01Cocoa " 0.3632 5.60 1.54Juice powder " 0.4695 4.07 0.867Raw coffee beans Sugar-type (40�C) 0.0574 5.45 9.49Tea Sugar-type (40�C) 1.0516 5.80 0.552Gelatine Sugar-type (40�C) 0.0170 2.59 15.2Soy milk Oil-type 0.0663 57.26 86.4Curry roux " 0.1353 4.57 3.38


179


Sample Quantity(g)


Moisture Content(%)

Coffee beansDried beer yeastCurry roux

130200130

0.19190.08400.1217

4.118.864.31

02.1410.603.54


Sample Quantity(g)


Moisture Content(%)

CoffeeRaw coffee beansCocoaHopsBeetGelatine

090150110130130180

0.12820.05550.24860.01890.09130.0114

322950123973153676691790

02.5209.0301.6008.1408.4015.70




Aquamicron CXU 10ml

III-3 Pharmaceuticals

180

III-3. Pharmaceuticals

In this field, Karl Fischer titration is the most effective tool for precisemoisture content measurement. Moisture content tends to be high, rangingfrom a few percent up to a few tens of percent. For this reason, volumetrictitration is generally used. The examples in this section show the application of Karl Fischer titration to biochemical and pharmaceutical products. Where the chemical ingredientsof these products are known direct titration can be used as it is possible todetermine whether or not interference will occur. Even if products cause interference, they can still be measured usingmoisture vaporization and Karl Fischer titration, provided that they remainstable when exposed to heat. Special pharmaceutical items are listed in the Japanese Pharmacopoeia.Aside from volumetric titration, the coulometric titration and moisturevaporization methods can also be used. This chapter gives examples basedon the actual implementation of these methods.

Sugar-type dehydrated solvents are generally used when applyingvolumetric titration to biochemical products such as amino acids,nucleic acids, sugars, enzymes and lipids. Even substances that do notdissolve in general-use dehydrated solvents can be titrated directlyusing a general-use dehydrated solvent, provided that the moisturecontent of the sample can be extracted adequately. Direct coulometric titration is not suitable as many samples cannot bedissolved in the anolytes used for this type of titration. Coulometrictitration is carried out using the moisture vaporization method. Somesamples break down at certain heating temperatures and there must becareful consideration of the temperature used for moisture vaporization. L-cystime and vitamin C react with Karl Fischer reagent and cannot betitrated directly. Care is needed with general vitamin preparations thatinclude vitamin C since these can also cause interference reactions.(Vitamin C reacts quantitatively with iodine. If the amount of vitamin Cincluded in a sample is known, then the moisture content can bedetermined by adjusting the results. Refer to the Basic Knowledgesection for more information.) Moisture vaporization is used with thesesubstances.

Key Points

1. Biochemical Products


181




Sample Quantity(g)


Moisture Content(%)

L-alanine General-use 0.5316 0.13 245ppmPotassium asparaginate " 0.1026 5.29 5.16Glycylglycine " 0.2882 0.24 833ppmVitamin B12 " 0.1452 11.27 7.76Vitamin B1 hydrochloride " 0.2321 9.89 4.26ATP Sugar-type 0.0750 6.55 8.73Citidine (5') diphosphocholine sodium " 0.0466 1.92 4.12Dextran " 0.0901 5.93 6.58Chlorella " 0.0550 3.54 6.44Yeast extract " 0.0810 0.95 3.58Cyclodextrin " 0.0386 1.55 4.02


Sample Quantity(g)


Moisture Content(%)

Adenosine triphosphate 200 0.0430 3.28 8.41




Sample Quantity(g)


Moisture Content(%)

L-alanine 150 0.7408 56 076ppmSodium asparaginate 180 0.0366 2020 5.52Glycylglycine 130 0.2765 70 253ppmL-cystine 130 0.1123 796 0.709Dextran 180 0.0457 3093 6.76Vitamin preparations 110 0.1211 2235 1.85Vitamin C 100 0.1264 1275 1.01Vitamin B12 130 0.0403 3128 7.76Chlorella 150 0.0659 4180 6.34Yeast extract 80 0.0391 1446 3.70Yeast nucleic acid 200 0.0230 5875 25.5


Aquamicron CXU 10ml


182

The Japanese Pharmacopoeia (7th revision) designates Karl Fischermethodology as the general testing method for 28 pharmaceuticalproducts. In addition to volumetric titration, the coulometric titration andmoisture-vaporization methods have also been specified. Normally,samples are placed in a general-use dehydrated solvent and stirred fora period before titration. Alternatively, surplus Karl Fischer reagent maybe added to the solution, which is then stirred for a period and reversetitrated with standard water-methanol. Depending on the solubility of thesample, a sugar-type or oil-type dehydrated solvent should be used. The chemical constituents of pharmaceutical products are usuallyknown so it is possible to determine in advance whether or not aparticular product is suitable for Karl Fischer titration. Coulometrictitration is convenient when only a limited amount of sample can beobtained (such as when a substance is too valuable to use more than afew milligrams), or when moisture content is low. The moisturevaporization method is used when it is difficult to draw the moisture intothe dehydrated solvent, or when interference would occur. As with other types of substances, the heating temperature must beselected with care. Moisture vaporization should be used only after careful consideration.

Key Points

2. Pharmaceuticals


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent SU(or MS, FM) 25-50ml


183


Sample Quantity(g)


Moisture Content(%)

Aminophylline General-use 0.2115 8.90 4.21Digitalis " 0.3502 5.46 1.56Antibiotics " 0.1245 8.35 6.71Gibberellin methyl ester " 0.2005 3.31 1.65Berberine chloride " 0.0433 4.23 9.55Glutathione " 0.2713 11.51 4.24Aspirin aluminum " 0.1638 2.33 1.42Carbetapeten citrate " 0.3053 0.13 0.043Chlorobutanol " 0.0896 4.35 4.85Patenol " 0.1243 0.13 0.10Erythromycin lactobionate " 0.0431 1.43 10.3Rutin " 0.1202 11.36 9.45Libotite Sugar-type 0.1337 31.18 23.3Hemin " 0.1838 1.47 0.800Phosphomycin Ca " 0.1533 14.65 9.49Pantechinan " 0.1375 28.30 20.6Sodium aspartate Sugar-type (40�C) 0.0543 5.77 10.6Throat drops " (40�C) 0.2970 10.79 3.63


Sample Quantity(g)


Moisture Content(%)

Phosphomycin CaPotassium xanthogenate

250150

0.11420.5009

10.5802.42

9.2600.483




Aquamicron CXU 5ml



Moisture Content(%)

AlbuminPolypeptideAminophylline

0.22360.00370.0427

069303161795

0.3108.5404.200


184


Sample Quantity(g)


Moisture Content(%)

AlbuminGlutathioneBerberine chlorideBufferinAspirin aluminumSynthetic penicillin

110110150130150150

0.18180.42080.02880.06620.17150.0837

057816352735264523322616

0.3180.3899.5604.0001.3603.130


Aquamicron CXU 10ml

Either a general-use or a sugar-type dehydrated solvent is used forchinese herbal medicines. In general, however, these products aredifficult to dissolve. This means that insufficient moisture is extractedand accurate analytical results cannot be obtained. The moisturevaporization method is used for this reason. The heating temperaturemust be considered carefully as heating can cause some products tochange color or break down. In the examples shown, biological tissue was dispersed in a general-use dehydrated solvent and subjected to Karl Fischer titration. Similar procedures should be used for capsules and other items.

Key Points

3. Chinese Herbal Medicines, Biological Tissue, etc.




185


Sample Quantity(g)


Moisture Content(%)

Pills (heart tonic) General-use 0.1356 8.86 6.53Muscle " 0.1018 75.74 74.4Brain " 0.0994 77.23 77.7Blood serum " 0.0916 83.90 91.6Pancreas " 0.6645 33.36 5.02Bile acid " 0.9185 15.15 1.65Licorice powder " 0.1111 9.91 8.92Crude drugs Sugar-type 0.0608 18.80 30.9Capsules " (40�C) 0.0697 9.81 14.1Soft capsules " (40�C) 0.0528 5.09 9.64


Sample Quantity(g)


Moisture Content(%)

Pills (heart tonic)Crude drugsMedicinal wafersCapsulesToothpasteBlack hairBlond hair

110130150170200200200

0.22150.05320.07760.07260.20690.07260.1583

14.5116.4612.8210.1464.3308.0918.38

06.5530.9016.5014.0031.1011.1011.60




Sample Quantity(g)


Moisture Content(%)

Crude drugs 130 0.0961 1254 1.30Licorice powder 130 0.0439 3977 9.06Cinnamon 130 0.0620 3464 5.59Mint 110 0.0428 2411 5.63Soft capsules 150 0.0463 4463 9.64Gelatine capsules 150 0.0201 3262 16.2


Aquamicron CXU 10ml

III-4. Minerals and Natural Products

186


This chapter provides examples of the use of Karl Fischer titration tomeasure the moisture content of mineral substances such as rock, sand andiron ore. As these substances are not soluble in solvents the moisturevaporization method is, of course, used in most cases. Particular care mustbe taken with reference to the heating temperature as water of compositioncan cause problems. Natural products vary widely and it is possible to present only a fewexamples here. Refer to these when determining the analytical conditions.

With the traditional drying methodology, substances like ores and rocktended to oxidize. Measurement had to take place over long periods oftime and the results were frequently inaccurate. By combining moisturevaporization with Karl Fischer titration moisture content can bemeasured quickly and accurately. Karl Fischer titration can be carried out using either volumetric orcoulometric methods. Volumetric titration is generally used forsubstances with a high moisture content. Since minerals commonlyoccur in lumps or granular form, samples must first be crushed intosuitably fine grains. During this process care is needed to preventmoisture vaporization into, or absorption from the atmosphere. With minerals, problems can arise not only with water of adhesion butalso with water of composition (water of crystallization). Fractionalmeasurement is achieved using the moisture vaporization method. Theheating temperature is set between 100 and around 200�C for water ofadhesion, and between 500 and 1,000�C when measuring water ofcomposition. Thus, the temperature for moisture vaporization is setaccording to both the type of sample and the purpose of themeasurement. A commercially available dual-system heating oven provides aconvenient way of obtaining accurate fractional measurements of waterof adhesion and water of composition.

Key Points

1. Minerals

Reference: JIS M8211 "Iron Ores--Method for Determination ofCombined Water Content"


187


Sample Quantity(g)


Moisture Content(%)

SoilDried soilPowdered quartz

General-use

""

0.05080.08581.6711

23.6304.2100.94

46.50004.91000.056


Reagents used:Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX (or MS) 25-50ml


Sample Quantity(g)


Moisture Content(%)

RocksClay

"SoilIron oreLimestoneCementFerriteCoalAmphiboleBlack micaKaolinTalcBentoniteManganese ore

900110700200750700800200180

10001000

8001000

800750

0.07980.88370.10330.04830.56380.24621.55550.89671.00221.02831.10050.14140.20030.11350.2313

13.1134.4614.9922.8813.58

0.8411.20

9.2033.4716.0425.7519.9414.4018.6124.29

16.403.9014.547.202.4100.3400.72001.0303.3401.5602.3414.107.1916.410.5




188


Sample Quantity(g)


Moisture Content(%)

Black micaAmphiboleRocksSilicaCasting sand

"ClaySoilTalc

"Sintered oreManganese ore

"Iron orePowdered quartz

"

10001000700900110900110180200900750110750750200900

0.07330.21670.11760.04761.52381.19270.05200.07360.45790.18710.09850.17000.01850.11151.10640.8052

17163391633123331515668820483747

8439512

65833

19222653

564937

002.34001.56005.38004.900

994ppm00.56103.94005.09000.18405.080

660ppm00.49010.40002.380

510ppm00.116


Aquamicron CXU 10ml


189


Sample Quantity(g)


Moisture Content(%)

Silver fir leavesTree rootsPollenPine resinRosin

General-use

"Sugar-typeKetone-type

"

0.04620.02790.00711.01060.7388

3.122.530.640.746.15

6.769.079.00.0730.832


Reagents used: Karl Fischer Reagent SS-Z (or SS)Dehydrated Solvent GEX, KTX, SU (or MS, CM,FM) 25-50ml


Sample Quantity(g)


Moisture Content(%)

Pine resin 130 1.6708 0.83 0.050



2. Natural Products

Natural products vary widely and the appropriate Karl Fischer titrationshould be selected to suit the particular sample. Direct titration is usedfor substances that dissolve in dehydrated solvent or that are unstablewhen heated. If the sample is stable when heated, use the moisturevaporization method. The heating temperature must be consideredcarefully when using that method. If the temperature is too high thebreakdown of the substance could lead to interference. (For example,the end point may not be reached, or the analytical results that areobtained may be abnormally high.) Karl Fischer titration can be carried out using either volumetric orcoulometric methods, but volumetric titration is probably more suitablesince natural products tend to have a high moisture content.

Key Points


190


Aquamicron CXU 10ml


Sample Quantity(g)


Moisture Content(%)

Silver fir leavesTree roots

130100

0.05410.0189

38001723

7.029.12



Moisture Content(%)

0.02470.1211

Raw lacquerProcessed lacquer

34663810

14.0003.15


Aquamicron CXU 5ml

Chapter IV: List of Karl Fischer Reagents

191


192

List of Karl Fischer Reagents


193

Volumetric Titration Reagents

The requirements for volumetric titration are a Karl Fischer reagent, standard water-methanol to assess the titer and a dehydrated solvent in which todissolve or disperse the sample. Mitsubishi Chemical Corporation has an extensive range of reagentssuitable for all levels of moisture content. Choose the combination ofproducts that is most suitable for your particular purpose.

Karl Fischer Reagent SS Series (Pyridine-Type)

The SS Series has enjoyed an excellent reputation for quality andperformance for many years.

Product Standard Packaging UsesKarl FischerReagent SS(Mitsubishi)

Titer2.5-3.5mgH2O/ml

500mlglass bottles

General-useThis titration preparation can beused for a wide range of purposes.

Dehydrated Solvent MS

Moisture content0.2mgH2O/ml or lower

500mlglass bottles

General-use (*recommended product)Suitable for organic solvents,inorganic chemicals, agriculturalchemicals, pharmaceuticals,fertilizers, detergents, foodstuffs,etc.

Dehydrated Solvent ML


500mlglass bottles

General-useSuitable for organic solvents,inorganic chemicals, agriculturalchemicals, pharmaceuticals,fertilizers, detergents, foodstuffs,etc.

Titer8-12mgH2O/ml

500mlglass bottles

High moisture contentThis product allows quick, accuratemeasurement of moisture contentover about 40% in foodstuffs,cosmetics, etc.


500mlglass bottles

Low moisture content This product is suitable for measuring moisture content below 100ppm in organic solvents, electrical insulating oils, gases, etc.


194

Product Standard Packaging UsesDehydrated Solvent CM


500mlglass bottles

Oil-typeSuitable for naphtha, gasoline,diesel oil, heavy oil, electricalinsulating oil, oils and fats (hardened oil, margarine, etc.), etc.



500mlglass bottles

Ketone-type (*recommended product)For ketones, silicon oils, acetic acidand other lower carboxylic acids,aldehydes (except acetaldehydes),anilines, etc.

Dehydrated Solvent PE


500mlglass bottles

Ketone-type For ketones, silicon oils, acetic acidand other lower carboxylic acids,aldehydes (except acetaldehydes),anilines, etc.

Dehydrated Solvent PP


500mlglass bottles

Aldehyde-typeAcetaldehydes, propionaldehydes,butyraldehydes, etc.

Dehydrated Solvent FM


500mlglass bottles

Sugar-typeSugars, proteins, gelatine,additives, animal feeds, etc.

Dehydrated Solvent ME


500mlglass bottles

For gaseous samplesNitrogen, etc.

Mix Dehydrated Solvent MS with propylene glycol (PG) in a 3:1 ratio (e.g. MS90ml:PG30ml) when using a moisture vaporization system.

Standard Reagents for Titer Assessment

Mitsubishi Chemical Corporation supplies two types standard water-methanol products that include a known amount of water. These productsare used to assess the titer. Select the product according to the titer of the Karl Fischer reagent that youare using. These standard reagents are also convenient for use in backtitration.


195

Product Standard Packaging UsesStandardWaterMethanol(Mitsubishi)

Moisture content:2.0�0.04mgH2O/ml

250mlglass bottles

Used to assess titer of Karl Fischer reagents(3-10mgH20/ml)

Moisture content:0.5�0.02mgH2O/ml

250mlglass bottles

Used to assess titer of Karl Fischer reagents (1mgH20/ml)

Karl Fischer Reagent SS-Z Series (Pyridine/Chloroform-Free Type)

Mitsubishi's SS-Z range of titration products is free of both pyridine andchloroform. These products are kind to both people and the environment. Karl Fischer Reagent SS-Z is a volumetric titration reagent that containsneither chloroform nor methyl cellosolve. It is also free of pyridine so there isalmost no odor. A low-toxicity solvent system has been used to develop a product that iskind to both people and the environment while providing the sameperformance as earlier products. These products can be used with existing moisture content measuringsystems. Combine them with the dehydrated solvent that is appropriate forthe sample.

Product Standard Packaging UsesKarl Fischer ReagentSS-Z(Mitsubishi)


500ml, 1Lglass bottles

General-useThis titration preparation can beused for a wide range of purposes.

Dehydrated Solvent GEX

Moisture content:0.2mgH2O/ml orlower

500mlglass bottles

General-useSuitable for organic solvents,inorganic chemicals, agriculturalchemicals, pharmaceuticals,fertilizers, detergents, foodstuffs,etc.

Dehydrated Solvent OLX


500mlglass bottles

Oil-type Suitable for naphtha, gasoline,heavy oil, electrical insulating oil,oils, etc.

Dehydrated Solvent OL II


500mlglass bottles

Oil-type (*includes chloroform)Suitable for naphtha, gasoline,heavy oil, electrical insulating oil,oils and fats, etc.


500mlglass bottles

Low moisture contentThis titration preparation is suitablefor samples with low moisturecontent.


196

Product Standard Packaging UsesDehydrated Solvent KTX


500mlglass bottles

Ketone-typeFor ketones, silicon oils, acetic acidand other lower carboxylic acids,aldehydes (except acetaldehydes),etc.

Dehydrated Solvent SU


500mlglass bottles

Sugar-typeSugars, proteins, gelatine,additives, animal feeds, etc.

Mix Dehydrated Solvent GEX with propylene glycol (PG) in a 3:1 ratio (e.g. GEX90ml:PG30ml) when using a moisture vaporization system.

Coulometric Titration Reagents

Coulometric titration reagents consist of anolytes which are placed in theanode chamber and catholytes which are placed in the cathode chamber.These products have a worldwide reputation for excellent performance andcan be used in all manufacturers' coulometric titration systems. A general-use product and a ketone-type product (for ketones, lower carboxylic acids,sil icon oils, etc.) are available. These products can be used withAquamicron CXU catholyte. These products are kind to both people and the environment. They containno carbon tetrachloride, methyl cellosolve, pyridine or chloroform.

Aquamicron Series

Product Standard Packaging UsesAquamicronAX (anolyte)

Moisture content:0.15mgH2O/ml or lower

500mlglass bottles

General-useUsed with organic solvents,inorganic chemicals, petroleumproducts, gases, and a wide rangeof other substances.

AquamicronAKX (anolyte)


500mlglass bottles

Ketone-useKetones, silicon oils, lowercarboxylic acids, etc.

AquamicronCXU (catholyte)


5mlampoules/10per case

AquamicronCXU (catholyte)


5mlampoules/10per case


197

Single-Solution Coulometric Titration Reagent

Aquamicron FLS is a single-solution coulometric titration reagent. It shouldbe used in single-solution electrolytic cells without diaphragm. Use this product in combination with single-solution electrolytic cells. This product is kind to both people and the environment. It contains nocarbon tetrachloride, methyl cellosolve, pyridine or chloroform.

Product Standard Packaging UsesAquamicronFLS

Moisture content:0.15mgH20/ml or lower

500mlglass bottles

Used for moisture vaporizationmethod. Organic solvents.

Product Standard Packaging UsesAquamicronSolid WaterStandard

Moisture content:3.83�0.05%

10gglass bottles

For evaluation a moisture meter witha water vaporizer.

Using Single-Solution Karl Fischer Titration

As the single-solution coulometric titration version of Karl Fischer titration has not been adopted as an official method (JIS, etc.), it should be regardedonly as a convenient methodology. (It may not be possible to use thisproduct in some types of equipment.)

Aquamicron Solid Water Standard

Aquamicron Standard SolutionMitsubishi Chemical Corporation has traditionally supplied standard water-methanol as a standard reagent for assessing titer. Recently we have begunto sell a new product which has been developed in response to growingawareness of the importance of day-to-day management needs. It alsoreflects the demand for products that are easy to use and manage. This product is the result of long years of experience in the fields ofproduction technology and moisture measurement technology. For addedpeace of mind, it is also environmentally friendly thanks to the use of low-odor, low-toxicity solvents.


198

Product Titer Packaging UsesAquamicronwater Standard 0.2mg

0.2mgH2O/g 5mlampoules/10per case

Used to check the accuracy ofcoulometric titration systems.

Aquamicronwater Standard 1mg

1mgH2O/g 5mlampoules/10per case

Used to check the accuracy ofcoulometric titration systems.

Aquamicronwater Standard 10mg

10mgH2O/g 8mlampoules/10per case

Used to assess the titer of KFreagents used in automaticvolumetric titration systems.

Product Moisture Content Packaging UsesCheck

Solution P(Mitsubishi)

3.8~4.2mgH2O/ml 100ml glassbottles withseptum caps

Used when the presence of free iodinein the anolyte has caused reddish-brown discoloration. Add a suitableamount to restore a water surplus.Normally a 100µl microsyringe is used.The readiness of a coulometric moisturemeasurement system for normal usecan be checked periodically bymeasuring a specific volume of CheckSolution (e.g. 100µl).

Mitsubishi Check Solution P

This end-point adjustment solution can be used with both general-use andketone-type products. It can also be used for day-to-day management ofcoulometric moisture measurement systems.

199

ChapterV: Summary of Selection Procedures for Karl Fischer Reagents

PlasticsInorganicsMinerals

General samples AminesKetones

Lower carboxylic acidAromatic aldehydes

Amines General samples

GEXMS

pH change intitration solvent?

Soluble inchloroform?

Interferencereaction with

sulfur dioxide?

Interferencereaction withmethanol?

Add salicylicacid

Soluble inmethanol?

Change inanolyte pH?

Interferencereaction with KF

reagent?

Interferencereaction withmethanol?

Moisture-vaporization

Interferencereaction with KF

reagent?

Moisturevaporization

Liquid or gas?

SS10mg/ml

SS-Z1,3,5mg/ml

Liquid or gas?

Expected moisturecontent 40% or

lower?Coulometrictitration

VolumetrictitrationSample

YES

YES

YES

NO

NO

YES

YES

NO

YES

NO

NO

NO

NO

NO

NO YES

YES

YES

YES

NO

NO

YES

YES NO

YES

Expected moisturecontent 1% or lower?

GEXMS

Add salicylicacid

AquamicronAKX/CXU

AquamicronAX/CXU

AquamicronAX/CXU

AquamicronAX/CXU

OLX, OL IICM

SUFM

Soluble informamide?

KTXCP PP GEX + PG

MS+PG

Petroleumproducts Sugars Ketones Aldehydes Solids

Soluble indehydrated

solvent?

Chapter VI: Index

201

Chapter VI: Index

Index

202

Chapter VI: Index

203

A:

Abietic acidAbsorbent cottonABS resinAcetaldehydeAcetamideAcetanilideAcetic acidAcetic anhydrideAcetoneAcetone cyanhydrinAcetone oximeAcetonitrileAcetophenoneAcetylacetonAcetyleneAcetyl peroxideAcetyl thioureaAcetylureaAcrolein cyanohydrin acetateAcrylic acidAcrylic fiberAcrylonitrileActuation oilAdenosine 5'-triphosphate disodiumAdhesiveAdipic acidAdiponitrileAerosolAir filter oil(L-)AlanineAlbuminAlizarinAlkyl alcoholAlkylbenzeneAlkyl benzene sulfonateAlkyl diphenyl ethaneAlkyl naphthaleneAlloxanAluminum chlorideAluminum fluorideAluminum nitrateAluminum oxideAluminum pasteAluminum powderAluminum sulfateAmino acid

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 89� � � � � � � � � � � � � � � � � � � � � � � 153

� � � � � � � � � � � � � � � � � � � � � � � � � � 148,149� � � � � � � � � � � � � � � � � � � � � � � � � � � � 86

� � � � � � � � � � � � � � � � � � � � � � � � � 100,101� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 100� � � � � � � � � � � � � � � � � � � � � � � 89,90,91

� � � � � � � � � � � � � � � � � � � � � � � 105� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 84,101

� � � � � � � � � � � � � 101,103� � � � � � � � � � � � � � � � � � � � � � � � � 103

� � � � � � � � � � � � � � � � � � � � � � � � 101,102� � � � � � � � � � � � � � � � � � � � � � � � 83,84

� � � � � � � � � � � � � � � � � � � � � � � � � � 83,84� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 29

� � � � � � � � � � � � � � � � � � � � � � � � 107� � � � � � � � � � � � � � � � � � � � 108,111

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 100� � � � � � � 101

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 89� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 153� � � � � � � � � � � � � � � � � � � � � � � 101,102� � � � � � � � � � � � � � � � � � � � � � � � � � � � 146

� � 181� � � � � � � � � � � � � � � � � � � � � � � � � � 159,160

� � � � � � � � � � � � � � � � � � � � � � � � � � � 89,90� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 101

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 140� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 144� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 181

� � � � � � � � � � � � � � � � � � � � � � � � � � � � 183,184� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 83

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 76� � � � � � � � � � � � � � � � � � � � � 145,146

� � � � � � � � � � � � � � � 162� � � � � � � � � � � � � � � � � 145

� � � � � � � � � � � � � � � � � � � � � 145� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 94,100

� � � � � � � � � � 121,122,133� � � � � � � � � � � � � � � � � � � � � 123

� � � � � � � � � � � � � � � � � 128,133� � � � � � � � � � � � � � � � � � � � � � � 120� � � � � � � � � � � � � � � � � � � � � � � 114

� � � � � � � � � � � � � � � � � � � � � 155� � � � � � � � � � � � � � � � � 126,133

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 180

Aminoacetonitrile(p-)Aminoazobenzene( -)Aminocapronitrile(5-)Amino-2-chlorotoluene-4-sulfonate(C-acid)(2-)Aminonaphthalene-1-sulfonic acid

(m-)AminophenolAminophylline(2-)Amino-3-picoline(2-)AminopyridineAmmoniaAmmonium acetateAmmonium chlorideAmmonium citrateAmmonium nitrateAmmonium oxalateAmmonium phosphateAmmonium sulfateAmphibole(n-)Amyl alcoholAniline(2-)AnilinoethanolAnisic acidAnisidine (p-anisidine)AnthraceneAnthranilic acidAntibioticsAntimony oxideAntioxidantApple powderArgonArsenic trioxideAryl formateAscorbic acidAsparagineAspartameAspartic acidAsphaltAspirin aluminumAviation oil

� � � � � � � � � � � � � � � � � � � � � � 101� � � � � � � � � � � � � � � 103

� � � � � � � � � � � � � � � � 101

� � � � � � � � � � � � � � � � � � � � � � 154

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 154,155� � � � � � 80,97,99,153,154

� � � � � � � � � � � � � � � � � � � � � � � � � � 183� � � � � � � � � � � � � � � � � � � � 99

� � � � � � � � � � � � � � � � � � � � � � � 97� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 40

� � � � � � � � � � � � � � � � � � 93,94� � � � � � � � 121,133,134

� � � � � � � � � � � � � � � � � � � � � � � 93� � � � � � � � � � 127,133,134

� � � � � � � � � � � � � � � � � � � � � 93� � � � � � � � � � � � � � � � 133

� � � � � � � � � � � � � � � 133,134� � � � � � � � � � � � � � � � � � � � � � � � 187,188

� � � � � � � � � � � � � � � � � � � � � � � � � 77� � � � � � � � � � � � � � � � � � 97,98,99,153,154

� � � � � � � � � � � � � � � � � � � � � � 99� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 89

� � � 97,99,153,154� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 72

� � � � � � � � � � � � � � � � � � � 154,155� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 183

� � � � � � � � � � � � � � � � � � 120,155� � � � � � � � � � � � � � � � � � � � 143,150,151

� � � � � � � � � � � � � � � � � � � � � � � � � � 172� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 130

� � � � � � � � � � � � � � � � � � � � � � � � � � � 40� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 91

� � � � � � � � � � � � � � � � � � � � � � � � � � � � 40� � � � � � � � � � � � � � � � � � � � � � � � � � � 90,94� � � � � � � � � � � � � � � � � � � � � � � 168,170� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 90

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 144� � � � � � � � � � � � � � � � � 183,184

� � � � � � � � � � � � � � � � � � � � � � � � � 144,146

Index

204

B:

Bakelite paperBarium acetateBarium carbonateBarium chlorideBarium fluorideBarium hydroxideBarium peroxideBasic magnesium carbonateBeer yeastBeetBentoniteBenzal-n-butylimineBenzaldehydeBenzamideBenzeneBenzenesulfonic acidBenzidine yellowBenzilic acidBenzoic anhydrideBenzoinBenzophenoneBenzothiazoleBenzothiopheneBenzotriazoleBenzoyl chlorideBenzoyl hydrazineBenzyl alcoholBenzylamineBenzyl benzoateBenzyl mercaptan(4-) Benzyl piperidineBerberine chlorideBile acidBiscuitBismuth oxideBiuretBlood serumBoric acidBorneolBoron oxideBrainBrake oilBrassBromobenzeneBromoform(1-) Bromohexadecane

� � � � � � � � � � � � � � � � � � � � � � � � 152� � � � � � � � � � � � � � � � � � � � � � � � � � 93

� � � � � � � � � � � 124,155,156� � � � � � � � � � � � � � � � � � 121,122

� � � � � � � � � � � � � � � � � � � � � � � � 123� � � � � � � � � � � � � � � � � � � � � � 118� � � � � � � � � � � � � � � � � � � � � � � � 40

� � � � � � � � 124� � � � � � � � � � � � � � � � � � � � � � � � 178,179

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 179� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 187

� � � � � � � � � � � � � � � � � � � 103� � � � � � � � � � � � � � � � � � � � � � � � � � � 88

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 100� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 72,73

� � � � � � � � � � � � � � � � � � 90� � � � � � � � � � � � � � � � � � � � � � 158

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 89� � � � � � � � � � � � � � � � � � � � 105

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 83� � � � � � � � � � � � � � � � � � � � � � � � � � � 83� � � � � � � � � � � � � � � � � � � � � � 97,108

� � � � � � � � � � � � � � � � � � 108,109� � � � � � � � � � � � � � � � � � � � � � � � � � 103

� � � � � � � � � � � � � � � � � � � � � � � 105� � � � � � � � � � � � � � � � � � � � � 102

� � � � � � � � � � � � � � � � � � � � � � � � 76,77� � � � � � � � � � � � � � � � � � � � � 96,97,99

� � � � � � � � � � � � � � � � � � � � � � � � 92� � � � � � � � � � � � � � � � � � � � 110

� � � � � � � � � � � � � � � � � � 99� � � � � � � � � � � � � � � 183,184

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 185� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 175

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Chapter VI: Index

205

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� � � � � � � � � � � � � � � � � � � � � � � � � � 156� � � � � � � � � � � � � � � � � � � � � � � � � 178,179

� � � � � � � � � � � � � � � � � � � � � � � � � � � 144,146� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 103

� � � � � � � � � � � � � � � � � � � � � � � 94,103� � � � � � � � � � � � � � � � � � � � � � � � � 144,145

� � � � � � � � � � � � � � � � � � � � � � � � � � � � 181� � � � � � � � � � � � � � � � � � � � � � � � 72,73

� � � � � � � � � 89

Index

206

CyclohexanolCyclohexanoneCyclohexanone oximeCyclohexeneCyclohexyl acetateCyclohexyl acetic acidCyclohexylamineCyclopentaneCyclopentanone(L-) Cystine

D:

(n-) DecaneDecanolDecalin(1-) DeceneDeoxybenzoinDetergentDextranDextroseDiacetone alcohol(1,3-) DiaminopropaneDi-ammonium hydrogenphosphateDiazoaminobenzeneDichloroacetic acid(2,4-) Dichlorophenoxy acetic acid(1,4-) Dichloro-2-butene(1,2-) Dichloroethane(p-) DichloronitrobenzeneDicyanamidesDicyclohexylamineDiesel oilDiesel engine oilDiethanolamineDiethylamine(2-) DiethylaminoethanolDiethyl peroxide(N,N-) DiethylanilineDiethylene glycolDiethylene glycol ethyl etherDiethylene glycol monoethyl etherDiethyl etherDiglycolic acidDihydropyran(2,3-) Dihydrofuran(�,�-) Dihydroxyadipic acidDi-isopropylamineDi-isobutylamine

� � � � � � � � � � � � � � � � � � � � � � � � � � � � 76� � � � � � � � � � � � � � � � � � � � � � 83,84

� � � � � � � � � � � � � � � � 103� � � � � � � � � � � � � � � � � � � � � � � � � 72,73

� � � � � � � � � � � � � � � � � � � � � � 91� � � � � � � � � � � � � � � � � 89

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� � � � � � � � � � � � � � � � � 99� � 128

� � � � � � � � � � � � � � � � � � 103� � � � � � � � � � � � � 89,90,91

� � � 89� � � � � � � � � � � � � � � 75

� � � � � � � � � � � � � � � � � � 75� � � � � � � � � � � � 104

� � � � � � � � � � � � � � � � � � � � � � � � 103� � � � � � � � � � � � � � � � � � � � � � 97

� � � � � � � � � � � � � � � � � � � � � 143,144,146� � � � � � � � � � � � � � � � � � � � � � � 145

� � � � � � � � � � � � � � � � � � � 97,98,99� � � � � � � � � � � � � � � � � � � � � 97,98,99

� � � � � � � � � � � � � � � 99� � � � � � � � � � � � � � � � � � � � � � � � 107

� � � � � � � � � � � � � � � � � � � � 99� � � � � � � � � � � � � � � � � � � 76,78

� � � � � � � � � � � 79� � � � 79

� � � � � � � � � � � � � � � � � � � � � � � � � � � � 78� � � � � � � � � � � � � � � � � � � � � � � � � � � 90� � � � � � � � � � � � � � � � � � � � � � � � � � � 79

� � � � � � � � � � � � � � � � � � 78,79� � � � � � � � � � � 90

� � � � � � � � � � � � � � � � � � � 98,99� � � � � � � � � � � � � � � � � � � � � � � � � 97

Di-isopropanolamineDi-isopropyl ketoneDi-isopropyl malonate(N,N-) Dimethyl acetamideDimethyl aminomethyl phenol(3-) Dimethylamino propionitrile(N,N-) Dimethylaniline(N,N-) Dimethyl benzylamine(N,N-) Dimethylcyclohexylamine(N,N-) DimethylethanolamineDimethyl ether(N,N-) Dimethyl formamideDimethylglyoxime(2,4-) Dimethyl pentane(2,4-) Dimethyl-3-pentanol(N,N-) Dimethyl-p-toluidineDimethyl sulfoxideDi-n-butylamine(m-) Dinitrobenze(3,5-) Dinitrobenzoic acidDinitrophenyl hydrazine(2,4-) DinitrotolueneDioxaneDipenteneDipentylamineDiphenylDiphenyl carbinolDiphenyl etherDiphenylamine(1,3-) Diphenyl thioureaDi-sec-butylamineDi-tert-butyl peroxideDithio acid(n-) DodecaneDodecanolDried vegetableDropsDyestuff

E:

Egg yolkElectric insulating oilEmulsifierEmulsionEnamelEngine oilEnzymeEpoxy resin

� � � � � � � � � � � � � � � � � � � 97� � � � � � � � � � � � � � � � � 38,83

� � � � � � � � � � � � � � � � � � 92� � � � � � � � � � � 101

� � � � � � � � � 99� � � � � � 99

� � � � � � � � � � � � � � � � � � 97� � � � � � 98,99

� � � � � 97� � � � � � � � � 97

� � � � � � � � � � � � � � � � � � � � � � � � � 78� � � � � 100,101

� � � � � � � � � � � � � � � � � � � � � 103� � � � � � � � � � � � � � � � 72

� � � � � � � � � � � � 76� � � � � � � � � � � 99

� � � � � � � � � � � � � � � 108,109� � � � � � � � � � � � � � � � � � � � � � � � � 99

� � � � � � � � � � � � � � � � 103,104� � � � � � � � 89,103

� � � � � � � � � � � � � � 102� � � � � � � � � � � � � � � � � � 104

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 78,79� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 72

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� � � � � � � � � � � � � � 111� � � � � � � � � � � � � � � � � � � � � 97

� � � � � � � � � � � � � � � � � 107� � � � � � � � � � � � � � � � � � � � � � � � � 108,111

� � � � � � � � � � � � � � � � � � � � � � � � � � � 73� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 76

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� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 178� � � � � � � � � � � � 146,143

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 168� � � � � � � � � � � � � � � � � � � � � � � � � � � 163,164� � � � � � � � � � � � � � � � � � � � � � � � � � � 156,157

� � � � � � � � � � � � � � � � � � � � � � � � � 145,146� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 180

� � � � � � � � � � � � � � � � � � � � � � � � � 148,149

Chapter VI: Index

207

ErucamideEthanolEthanolamineEthyl acetateEthylamine(N-) Ethyl anilineEthyl benzene(p-) Ethylbenzene sulfonyl chloride

Ethyl carbamateEthyl carbonateEthyl chlorocarbonateEthyl citrateEthyleneEthylene bromideEthylene chlorideEthylene glycolEthylene glycol dimethyl etherEthylene glycol monoethyl etherEthylene oxideEthylene propylene rubberEthylene thiocyanateEthyleneureaEthylene vinyl acetateEthylene vinyl acetate copolymer

Ethyl formate(2-) Ethyl hexanolEthylidene bromideEthyl iododeEthyl isothiocyanateEthyl malonateEthyl mercaptan(N-) Ethyl morpholineEthyl thioacetateEthyl thiocyanateEthyl vinyl etherEugenol

F:

FatFerriteFertilizerFiberFilter paperFlavoringFluorine glassFluorine resin

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 101� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 76,77

� � � � � � � � � � � � � � � � � � � � � � � � � � � � 97� � � � � � � � � � � � � � � � � � � � � � � � � � 91,92� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 97

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� � � � � � � � � � � � � � � � � � � � � � 76,77� � � � � � � 78� � � 77,79

� � � � � � � � � � � � � � � � � � � � � � � � � � 78� � � � � � � � � 150

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� � � � � � � � � � � � � � � � � � � � � � � � � � 137� � � � � � � � � � � � � � � � � � � � � � � � � � 149

FormaldehydeFormaldehyde cyanhydrineFormalinFormamideFormic acidFurfural

G:

Gadolinium oxideGasolineGasoline engine oilGear oilGelatinGeraniolGibberellin methyl esterGlass powderGlass woolGlucoseGlutamic acidGlutathioneGlycerineGlycineGlycolic acidGlycylglycineGranulated sugarGreaseGrinding oilGuaiacolGuanidine nitrateGypsum

H:

Hair (black,blond)Hair tonicHeat treatment oilHeavy oilHeliumHeminHepta-aldoxime(n-) HeptaneHeptyl mercaptanHexadecyl bromideHexamethyl benzene(n-) Hexane(1-) Hexene(n-) HexylamineHexyl mercaptanHigh-grade chemical fertilizer

� � � � � � � � � � � � � � � � � � � � � � � � � 86� � � 101,103

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Index

208

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L:

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M:

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I:

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J:

J-acidJuice powder

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Chapter VI: Index

209

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� � � � � � � � � � � � � � � � � � 148,149� � � � � � � � � � � � � � � � � � � � � � 148

� � � � � � � � � � � � � � 181� � � � � � � � � � � � � � � � 124

� � � � � � � � � � � � � � � � � � � � � 121,122,123,133,134� � � � � 106

� � � � � � � � � � � � � � � � � � � � 121� � � � � � � � � � � � � 168

� � � � � � � � � � 93� � � � � � � � � � � � � � � � � 118

� � � � � � � � � � � � � � � � � � � � � � 121� � � � � � � � � � � � � � 126

� � � � � � � � � � � � � � � � � � � � � � 127

Chapter VI: Index

211

Potassium oxalatePotassium permanganatePotassium persulfatePotassium sorbatePotassium xanthogenatePotato chipPower cable rubberPress board paperPrinted circuit boardPropane(1,2-) Propane diamine(1,2-) Propanediol(1,3-) Propanediol(i-) Propanol(n-) PropanolPropargyl alcoholPropionaldehydePropionanilidePropionic acidPropionic anhydridePropionyl chloridePropylamine(n-) Propylamine(i-) PropylaminePropylenePropylene glycolPropylene oxidePrussian bluePyridine(2-) Pyridyl ethanol(4-) Pyridyl ethanolPyrogallolPyromellitic acidPyrrolePyrrolidine

Q:

QuartzQuinalizarinQuinoline(p-) Quinone

R:

RaffinoseRapeseed oilRed iron oxideRed phosphorusRefrigerating machine oil

� � � � � � � � � � � � � � � � � � � � � � � 93� � � � � � � � � � � 127

� � � � � � � � � � � � � � � � � � � 40� � � � � � � � 168,169,170

� � � � � � � � � � � � � 183� � � � � � � � � � � � � � � � � � � � � � � � � � 175

� � � � � � � � � � � � � � � � � � � 150� � � � � � � � � � � � � � � � � � � 152� � � � � � � � � � � � � � � � � � � 166

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� � � � � � � � � � � � � � � � � � 105� � � � � � � � � � � � � � � � � � � � 105

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� � � � � � � � � � � � � � � � � � � � � � � � � � � � 187,188� � � � � � � � � � � � � � � � � � � � � � � � � � � � 83

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� � � � � � � � � � � � � � � � � � � 120,155� � � � � � � � � � � � � � � � � � � � � � 114

Resorcinol(L-) Rhamnose(Small) Rice crackerRicinoleic acidRinseRockRolling oilRootsRosinRotary pump oilRubberRust preventive oilRutin

S:

SaccharinSalad oilSalicylaldehydeSalicylamideSalicylic acidSandSarcosineSealerSebacic acidSebaconitrileSemicarbazide hydrochlorideSesame oilShampooSilicaSilicon rubberSilicon oilSilicon oxideSilicon waferSilver (I) oxideSnackSoapSodium acetateSodium adipicateSodium arseniteSodium aspartateSodium benzoateSodium bicarbonateSodium carbonateSodium chlorideSodium chondroitin sulfateSodium citrateSodium glutamate

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 143,144,146� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 81

� � � � � � � � � � � � � � � � � � � � � � � � � � 94� � � � � � � � � � � � � � � � � � 175

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� � � � � � � � � � � � � � � � � � � � � � � � � � 186,187,188� � � � � � � � � � � � � � � � � � � � � � � � � � 144,146

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� � � � � � � � � � � � � � � � � � � � � 93,94� � � � � � � � � � � � � � � � � � � � � � � 93� � � � � � � � � � � � � � � � � � � � � 127� � � � � � � � � � � � � � � � � 94,183

� � � � � � � 93,168,169,170� � � � � � � � � � � � � 123,124

� � � � � � � � � � � � � � � � � � � � � 124� � � � � � � � � � � � � � � � � � � � � � � 121

� � � � � 168,170� � � � � � � � � � � � 93,94,168,169

� � � � � � � � � � � � � � � 168,170

Index

212

Sodium 5'-guanylateSodium hydroxideSodium 5'-inosinateSodium formateSodium hydrosulfiteSodium iodideSodium L-aspartateSodium metaarseniteSodium metabisulfiteSodium metasilicateSodium naphthionateSodium nitrateSodium nitriteSodium peroxideSodium phthalateSodium polyphosphateSodium pyrosulfiteSodium succinateSodium sulfateSodium sulfiteSodium tartrateSodium tetraborateSodium thiosulfateSodium tripolyphosphateSoilSorbic acidSorbit(D-) SorbitolSoupSoy bean oilSoy flourSoy milkSoy sauceSpiceSprayStarchStearamideStearic acidStearoyl chlorideStearyl alcohlStrontium chlorideStyrol foamStyreneStyrene-butadiene rubberSuccinic acidSuccinic anhydrideSugarSugar syrup

� � � � � � � � � � � � � � � � � � 170� � � � � � � � � � � � � � � � � � � � 118

� � � � � � � � 168,169,170� � � � � � � � � � � � � � � � � � � � � � � � 93

� � � � � � � � � � � � � � � � � � 126� � � � � � � � � � � � � � � � � � � 122,123

� � � � � � � � � � � � � � � 94,183� � � � � � � � � � � � � � � � � � 41

� � � � � � � � � � � � � � � � � 126� � � � � � � � � � � � � � � � � 128� � � � 93,94,154,155

� � � � � � � � � � � � � � 127,128,134� � � � � � � � � � � � � � � � � � � � � � � � � � 127

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� � � � � � � � � � � � � � � � � � � � � � � � � � 93� � � � � � � � � � � � � � � � � � � 127

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� � � � � � � � � � � � � � � � � � � � � � 105� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 76

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� � � � � � � � � � � � � � � � � � � � � � � � 173,174,180� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 173

Sulfanilic acidSulfurSulfur dioxideSulfur hexafluorideSulfuric acidSurfactantSweetenerSynthetic paper

T:

TalcTeaTartaric acidTerpinenolTetrabromoethane(1,1,2,2-) Tetrachloroethane(1-) TetradeceneTetrahydrofuranTetramethylene oxideTerephthalic acidThiamine hydrochlorideThinnerThioacetic acidThiobenzamideThioglycollic acid(2-) ThionaphtholThiopheneThiophenolThioureaTin (II) chlorideTin (IV) chlorideTire rubberTitaniumTitanium oxideTolueneToluene 2,4-disulfonyl chlorideToluenesulfonic acid(o-) Toluenesulfonamide(p-) Toluene sulfonyl chlorideToluidineTonerToothpasteTransformer oilTriacetone peroxideTriazineTriazoleTri-n-butylamineTrichloroacetic acid

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 90� � � � � � � � � � � � � � � � � � � � � � � 114,135,151

� � � � � � � � � � � � � � � � � � � � � � � � � � � 140� � � � � � � � � � � � � � � � � � � � 122

� � � � � � � � � � � � � � � � � � � � � � � 115,116� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 162� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 168

� � � � � � � � � � � � � � � � � � � � � � � � � 153

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 187,188� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 178

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 90� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 76

� � � � � � � � � � � � � � � � � � � � � � � 75� � � � � � � � � � � 75

� � � � � � � � � � � � � � � � � � � � � � � � 73� � � � � � � � � � � � � � � � � � � � � 78,79

� � � � � � � � � � � � � � � � � � 78� � � � � � � � � � � � � � � � � � � � � � � 90

� � � � � � � � � � � � � � 168� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 157

� � � � � � � � � � � � � � � � � � � 108,111� � � � � � � � � � � � � � � � � � � � � � � � 111

� � � � � � � � � � � � � � � � � � � � � 110� � � � � � � � � � � � � � � � � � � � � � � 110

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 108� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 110

� � � � � � � � � � � � � � � � � � � � � � � 108,110,111� � � � � � � � � � � � � � � � � � � � � � � � � 121� � � � � � � � � � � � � � � � � � � � � � � � 121

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 150� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 114

� � � � � � � � � � � � � � � 120,155,156� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 72,73

� � � � � � 106� � � � � � � � � � � � � � � � � � � 90

� � � � � � � � � � � � � � � 154� � � � � � � � 106

� � � � � � � � � � � � � � � � � � � � � � � � 97,99,154� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 158

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 185� � � � � � � � � � � � � � � � � � � � 143,144

� � � � � � � � � � � � � � � � � � � 107� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 97� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 97

� � � � � � � � � � � � � � � � � � � � � 98,99� � � � � � � � � � � � � � � � � � � � � 89

Chapter VI: Index

213

(1,1,1-) Trichloroethane(1,1,2-) TrichloroethaneTriethanolamineTriethylamineTrifluoroacetic acidTrimethylacetic acidTrimethylamine(2,2,4-) Trimethyl pentaneTri-isopropanolamineTri-n-propylamineTris (hydroxymethyl) aminomethaneTri-sodium phosphate8TungstenTurbine oil

U:

UndecanolUranyl acetateUreaUrea resinUrethane

V:

(n-) Valeric anhydrideValeryl chlorideValineVanadium chlorideVarnishVegetable oilVinyl acetateVinyl chlorideVinyl ether(N-) Vinyl pyrrolidoneVitamin B12

Vitamin B1 hydrochlorideVitamin CVulcanization accelerator

W:

WafersWasabiWaxWheatWheat flourWool

� � � � � � � � � � � � � � � � 75� � � � � � � � � � � � � � � � 75

� � � � � � � � � � � � � � � � � � � � � � 97,99� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 97

� � � � � � � � � � � � � � � � � � � � � 89� � � � � � � � � � � � � � � � � � � � 89

� � � � � � � � � � � � � � � � � � � � � � � � � 97� � � � � � � � � � � � � 72

� � � � � � � � � � � � � � � � � � 97� � � � � � � � � � � � � � � � � � � � � � 99

� � 97� � � � � � � � � � � � � � � � 128

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 114� � � � � � � � � � � � � � � � � � � � � � � � � 144,146

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 77� � � � � � � � � � � � � � � � � � � � � � � � � � � 93

� � � � � � � � � � � � � � � � � � � � � � � 100,133,134� � � � � � � � � � � � � � � � � � � 147,148,149

� � � � � � � � � � � � � � � � � � � � � � � � � 148,149

� � � � � � � � � � � � � � � � 105� � � � � � � � � � � � � � � � � � � � � � � 105

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 90� � � � � � � � � � � � � � � � � � � � 122

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 156� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 176� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 149

� � � � � � � � � � � � � � 74,75,140,149� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 78,79

� � � � � � � � � � � � � � � � 104� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 181

� � � � � � � � � � � � � 181� � � � � � � � � � � � � � � � � � � � � � � � � 180,181

� � � � � � � 150,151

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 175� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 173,174� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 144,146

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 172� � � � � � � � � � � � � � � � � � � � � � � � � � � 172

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 153

X:

XyleneXylenesulfonic acid(2,6-) Xylenol

Y:

Yeast extract

Z:

Zinc acetateZinc fluorideZinc oxideZinc (Powdered metal)Zinc stearateZinc sulfate

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 72,73� � � � � � � � � � � � � � � � � � � � � 90

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 81

� � � � � � � � � � � � � � � � 168,170,181

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 93� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 123

� � � � � � � � � � � � � � � � � � � 119,120,151� � � � � � � � � � � � � � � 114

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 93� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 125

215

Afterword

Nine years have passed since I first thought of the production of this KarlFischer Reagent Manual and the work was suspended for a considerableperiod. Now that the project is finally complete, it feels as if a heavy load hasbeen lifted from my shoulders. I hope that this book will assist you with theuse of the various Karl Fischer reagent products.

At the completion of the project, I should like to acknowledge thecontribution of Mr. Shin'ichi Kuwata (formerly leader of this group) whocreated the basic framework for the book, Professor Kaname Muroi who hasspent many years researching the Karl Fischer moisture measurementmethod and Mr. Mitsumasa Ono (currently with Daia Instruments Co., Ltd. )who carried out the actual Karl Fischer moisture measurements used asexamples in this book. I should like also to thank Mr. Akiyoshi Nozawa (currently of Nippon Rensui Co., Ltd.), Ms. Hiroko Fujino, Ms. Akiyo Sekino(retired), Ms. Yuka Nitta (nee Fujimoto, retired) and Ms. Naoko Katayama. Thanks are due also to Mr. Kazuo Kikuchi, Director, Business Department,Deputy General Manager Masaki Hayashi, Acting Department ManagerTakazumi Kanekiyo, Acting Department Manager ToshiyukiNarikiyo,Mr.Toshihiko Yamashita,Mr. Takashi Kowada ,Mr.Mitsunari Morishitaand Kengo Itou of Mitsubishi Chemical Corporation's Functional ChemicalCompany, and to Mr. Yasuo Koike and Kazuo Kumamoto, Directors andGroup Leader Toshio Kaneko of the Analytical Sciences Laboratory at theYokohama Research Center. Without their assistance this project would nothave been possible.

Hiromasa Kato (responsible for the text)Analytical Sciences Laboratory Yokohama Research Center

July 1999

217

API CorporationA subsidiary of Mitsubishi Chemical Corporation

Mitsubishi ChemicalGroup

Head Office2-4-9, Hiranomachi, Chuo-ku, Osaka 541-0046, JAPAN

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Agent:

Printed in JapanRev. 3

introduction · 1. unlike standard volumetric analysis, it is not possible with karl fischer...

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