information for users of titration and ph systems, density ... · and ph systems, density meters...

$: Information for users of Titration and pH Systems, Density ... · and pH Systems, Density Meters and Refractometers Contents Basics • Coulometric titration 2 FAQ • Tips and tricks$
7Information for users of Titration and pH Systems, Density Meters and Refractometers

Contents

Basics• Coulometric titration 2

FAQ• Tips and tricks for everyday titration 5

Expert tips• 21 CFR part 11 8• Titration – fully networked 11

Applications• Efficient quality control of liquids with density and refractive index determination 12• Gas-phase extraction and coulometric determination of water 14• Efficient analysis of drinking water 18

New products 21 - Rondolino - LabX - DL39/32 - Stromboli - DR45 - SC1 and SC30 - CoverUp™ - DH100

A. De Agostini

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Coulometric titrationThe technique of coulometric titration was originally developed by Sze-belledy and Somogy [1] in 1938. The method differs from volumetric titration in that the titrant is generated in situ by electrolysis and then reacts stoichiometrically with the substance being determined. The amount of substance reacted is calculated from the total electrical charge passed, Q, in coulombs, and not, as in volumetric titration, from the volume of the titrant consumed.

According to Faraday’s Law, the amount of substance converted, m [g], is given by the equation

where M is the molar mass [g/mol], F is Faraday‘s constant (96485 C/mol) and z is the ionic valence.

The initial ideas behind coulomet-ric titration can be traced back to the beginnings of electroanalytical chemistry. As early as 1917, Grower [2] described a method for deter-mining the thickness of tin plate on iron by electrolysis. Coulometric analyses [3] can in fact be carried out according to two different tech-niques: controlled-current coulom-etry (galvanostatic coulometry), in which the electrolysis is performed while the current is held constant, or controlled-potential coulometry (po-tentiostatic coulometry), in which the potential is kept constant. In practice, relatively few titrations are used in which both the reagent and the analyte (e.g. acids) react at the electrodes of the electrolysis cell. A fundamental and essential requirement for a coulometric titra-tion is 100 percent current efficiency at the electrodes of the electrolysis cell. The reagent generated (titrant) must react stoichiometrically and preferably rapidly and irreversibly with the substance being determined (analyte). The reagent can be gener-

ated in situ, i.e. in the analysis so-lution, or in an external vessel with continuous flow. In practice, most commonly used coulometric titra-tions allow the direct determination of substances that are not reduced or oxidized at the generator electrodes. This has the advantage that the gen-eration of titrant takes place with 100 percent current efficiency. With elec-trolytically generated reagents, neu-tralization titrations, redox titrations, precipitation titrations and complexo-metric titrations can be performed. An overview of possible titrations is given in table 1 [4].

The equivalence point or end point of a coulometric titration can be deter-mined as in any other titration, for example by color indication, poten-tiometry, amperometry or with polar-ized electrodes [5].

Advantages of coulometric titration• Coulometric titration has the

advantage that constant cur-rent sources for the generation of titrants are relatively easy to make.

• The electrochemical generation of a titrant is much more sensitive and can be much more accurate-ly controlled than the mechanical addition of titrant using a burette drive. For example, a constant current flow of 10 µA for 100ms is easily generated and corresponds

to about 10-8 mol or just a few micrograms of titrant.

• The preparation of standard solu-tions and titer determination is of course no longer necessary.

• Chemical substances that are unstable or difficult to handle because of their high volatility or reactivity in solution can also very easily be used as titrants. Exam-ples are bromine, chlorine, Ti3+, Sn2+, Cr2+ and Karl Fischer rea-gents (iodine).

• Coulometric titrations are easier to automate because a source of current is appreciably easier to control than a burette drive.

• Coulometric titrations can also be performed under inert atmosphere or be remotely controlled, e.g. with radioactive substances.

• Dilution effects due to the addi-tion of the titrant are of no im-portance, which makes it easier to determine the end point.

Experimental requirementsSeveral important experimental fac-tors have to be taken into consid-eration in order to benefit from the advantages of coulometric titration. As mentioned before, 100 percent conversion or current efficiency at the generator electrodes is a fundamen-tal requirement. But, how can 100 percent efficiency be ensured? The main condition is that the potential of the generator electrode (anode or cathode) toward its surroundings (the electrolyte) is in a range in which no other reactions can take place. This is achieved by controlling the applied voltage or through a suitable choice of the electrolyte. The electrolyte solution must be inert and have a sufficiently high concentration so that changes in potential due to undesired reactions are of no importance. Most coulomet-ric titrations therefore use buffer solu-tions as electrolytes. Besides this, the geometry of the measuring cell and the stirrer speed (rapid homogeneity

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of the analysis solution) also play a very important role. The reagent gen-erated must be dispersed as rapidly as possible throughout the measuring cell. Efficient and rapid mixing of the analysis solution with the titrant leads to steady state conditions at the electrodes (sensors) being attained more quickly. This in turn allows the titration to be more easily controlled and improves the evaluation.

Another important factor is the elec-trode substrate (material) of the generator electrodes and their ar-rangement in the measuring cell. The hydrogen overvoltage is also an important quantity to consider when choosing the electrode substrate. Typi-cal electrode substrates with high hy-drogen overvoltages are mercury and platinum. The polarization range at these metals is by far the greatest. Sometimes, gold and synthetic mate-rials such as glassy carbon are used. Platinum is also suitable as an elec-trode substrate because it is chemi-cally stable and corrosion-resistant in most electrolyte solutions.

Electrolysis cells with and without diaphragmsUsually the anode and cathode of an electrolysis cell are physically sepa-rated. The ion transport necessary for current flow is maintained by a membrane or diaphragm. Separa-tion of cathode and anode is usu-ally necessary to avoid undesired side reactions such as the oxidation or reduction of the substance being de-termined. Coulometric titration cells with non-isolated generator electrodes are however possible and are being in-creasingly used [6]. Such electrolysis cells are above all used in the Karl Fischer titration technique and are referred to as “diaphragm-less cells”. What has to be taken into account when using such cells? Since 100 percent current efficiency is the prime target in all these cells, the geomet-

ric design is important. The simplest rule is to separate anode and cathode as far as possible from each other in order to avoid side reactions at the cathode (assuming the titrant is gen-erated at the anode e.g. in Karl Fischer titrations). This is, however, only pos-sible if the conductivity of the solution is sufficiently high and the capacity of the voltage source adequate, or with very small measuring cells. In commercially available Karl Fischer coulometers, this is achieved by op-timizing the ratio of surface areas of the electrodes (anode to cathode). The cathode surface area is made as small as possible. This results in high cur-rent densities at the cathode so that only hydrogen ions can be reduced.

The cathode should be positioned so that a homogeneous current density distribution is obtained at the anode. This ensures a current efficiency of almost 100 percent. If these condi-tions are satisfied, coulometric titra-tions with non-isolated electrolysis cells can be performed without any difficulty.

The advantages of non-isolated (dia-phragmless) electrolysis cells are:• Only one electrolyte solution

is required. This simplifies the cleaning and maintenance of the analysis cell.

• The electrolysis current is not re-duced or interrupted by blocked membranes (diaphragms).

Electrogenerated titrant

Generator electrode and electrolyte

Typical substances determined

Oxidants

Bromine Pt/NaBr As(III), U(IV), NH3, olefines, phenols, SO2, H2S, Fe(II)

Iodine Pt/KI H2S, SO2, As(III), water (Karl Fischer) Sb(III)

Chlorine Pt/NaCl As(III), Fe(II), various organic substances

Cerium (IV) Pt/Ce2(SO4)3 U(IV), Fe(II), Ti(III), I-

Manganese (III) Pt/MnSO4 Fe(II), H2O2, Sb(III)

Silver (II) Pt/AgNO3 Ce(III), V(IV), H2C2O4

Reductants

Iron (II) Pt/Fe2(SO4)3 Mn(III), Cr(VI), V(V), Ce(IV), U(VI, Mo(VI)

Titanium (III) Pt/TiCl4 Fe(III), V(V,VI), U(VI), Re(VIII), Ru(IV), Mo(VI)

Tin (II) Au/SnBr4(NaBr) I2, Br2, Pt(IV), Se(IV)

Copper (I) Pt/Cu(II)(HCl) Fe(III), Ir(IV), Au(III), Cr(VI), IO3

Uranium (V),(IV) Pt/UO2SO4 Cr(VI), Fe(III)

Chromium (II) Hg/CrCl3(CaCl2) O2, Cu(II)

Complexing agents

Silver(I) Ag/HClO4 Halide ions, S2-, mercaptans

Mercury (I) Hg/NaClO4 Halide ions

EDTA Hg/HgNH3EDTA2- Metal ions

Cyanide Pt/Ag(CN) Ni(II), Au(II,I), Ag(I)

Acids and bases

Hydroxide ions Pt(-)/Na2SO4 Acids, CO2

Hydrogen ions Pt(+)/Na2SO4 Bases, CO3, NH3

Table 1: Overview of possible titrations [4]

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• The conductivity of the analysis solution remains constant over a longer period of time, depending on the sample.

• Diaphragmless cells are therefore suitable for oily and poorly con-ducting substances.

Coulometric Karl Fischer titration with the METTLER TOLEDO DL32 and DL39 coulometersBy far the most widely used coulo-metric titration is the Karl Fischer titration (KF titration) for the deter-mination of water content. In the Karl Fischer reaction, iodine is generated in situ from iodide ions. The iodine then reacts stoichiometrically with water in the presence of chemically bound sulfur dioxide according to the following reaction scheme [7]:

ROH + SO2 + RN → (RNH)SO3R

2 RN + (RNH)SO3R + I2 + H2O → (RNH)SO4R + 2 (RNH)I

The coulometric Karl Fischer titration can be used to measure a large variety of samples. They are prepared in different ways depending on the type of sample involved. Liquid and solu-ble samples are simply injected into the titration cell. With solid samples, the water content can be determined either by (external) extraction or by heating the samples in an oven and passing the moisture evolved into the titration cell using a carrier gas and a transfer tube.

Due to its extremely high sensitivity, the coulometric Karl Fischer titra-tion is an excellent method for the determination of very low quantities of water (a few ppm). It can however also be used to measure samples with water contents of up to five percent. In this respect, it is therefore an alter-native to the volumetric Karl Fischer titration.

At the beginning of the year 2002, METTLER TOLEDO announced two new instruments for coulometric Karl Fischer titration, the DL32 and DL39 coulometers. Both coulom-eters can be used with cells with or without diaphragm. In comparison with the DL32 instrument, which is ideal for routine determinations, the DL39 coulometer offers a number of additional features. These include the Autostart function, a method for performing external extractions (METTLER method 913) and en-hanced possibilities for the evalua-tion of results (statistical functions, calculations). Besides the Karl Fischer standard methods, the DL39 cou-lometer provides four additional

METTLER methods that can be used as templates to prepare and store fifty user methods.

Methods are also supplied with the DL39 coulometer for another special application, the Bromine Index de-termination (METTLER methods No. 914, 915). These methods are used for the determination of double bonds in organic compounds, for example in gasoline. The Bromine Index indi-cates the amount of bromine that reacts with an olefinic substance [mg/100g], and is therefore a meas-ure of the double bond content, or degree of saturation.

In the development of both the DL32 and DL39 coulometers, particular at-tention was of course paid to customer requirements such as GLP-conform-ing printouts, user-friendliness, etc. All in all, the new DL32 and DL39 coulometers are excellent additions to the already comprehensive range of METTLER TOLEDO titration in-struments.

References:[1] L. Szebelledy and Z. Somogyi, Z. anal.

Chem., 112, 313, 323, 332, 385, 391, 395, 400 (1938)

[2] G. G. Grower, Am. Soc. Testing Materials, Proc., II, 17, 129 (1917)[3] James J. Lingane, Electroanalytical

Chemistry, Second Edition, Interscience Publishers (1958)

[4] A. J. Bard, L. R. Faulkner, Electro- chemical Methods, Second Edition, Wiley (2001)[5] Paul Delahay, New Instrumental Methods in Electrochemistry, Interscience Publishers (1954), p.304[6] E. Eisner et.al., Analytica Chimica Acta

359 (1998), 115-123[7] E. Scholz, Karl Fischer Titration,

Springer-Verlag Berlin (1984)

DL39 coulometer

V V

dE/dV

S

S

dE/dV

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Tips and tricks for everyday titrationEvery day of the week, METTLER TOLEDO titration specialists receive calls from customers using titrators for their daily work in the labo-ratory. The questions they ask concern particular technical points or application problems through to the optimization of methods. Quite often there is not a straightforward answer to some of the questions. The situation in which the equivalence point is not detected is a good example because the reasons for this are not always clear.

not be evaluated (Table 1).

User: What do I have to do?

MT: Make the predispensing volume smaller; instead of using a fixed vol-ume, adapt the predispensing to the sample weight, or increase the sam-ple weight.

Reason B: The threshold is too high.If the highest value of the first de-rivative (dE/dV) is less than the set threshold, the equivalence point is not evaluated (Fig. 1)

User: “My titrator has not evalu-ated the titration curve (properly), although a clear jump can be seen. What could be the reason for this?”

MT: There are several possible reasons:A) The equivalence point is in the

predispensing step.B) The threshold is too high. C) The initial potential is higher than

the predispensing to potential.D) The minimum increment (Vmin)

is too small.E) The value set for the (constant)

potential difference per volume increment, dE(set) is too large.

F) Wrong tendency.

Reason A: The equivalence point is in the predispensing step. If the four measurement values needed for the evaluation overlap the predispensing step, the equivalence point is not evaluated.

User: How do I check this?

MT: To evaluate a peak maximum correctly, the titrator needs four measurement values of the first deriv-ative of the titration curve, with two before the maximum and one after. In the following measurement value table shown as an example, it is clear that one of the four measurement val-ues overlaps the predispensing step, the end of which is shown by ET2. The equivalence point can therefore


MT: You compare the value of the peak maximum of the first deriva-tive of the titration curve from the measured value table with the value of the threshold set in the EQP titra-tion method function. It is then clear that the value of 5 pH/mL is greater than the value of 4.595 pH/mL for the peak maximum of the first derivative. The equivalence point is therefore not evaluated (Table 2).


Table 1: Reason A; measurement value for evaluation is in the predispensing step

VolumemL

IncrementmL

SignalmV

Change mV

1st derivativemV/mL

Timemin:s

ET1 0.0000 667.6 0:301.9060 1.9060 653.2 -14.5 -7.6 1:002.8590 0.9530 658.5 5.3 5.6 1:30

ET2 3.3360 0.4770 697.5 39.0 81.7 2:003.3860 0.0500 714.3 16.8 336.0 2:303.4860 0.0500 910.0 195.7 3182.1 3:003.4860 0.0500 1069.1 159.1 3182.1 3:303.5360 0.0500 1118.8 49.7 994.0 4:003.5860 0.0500 1149.4 30.6 611.8 4:303.6360 0.0500 1165.9 16.5 330.4 5:00

Fig. 1: Threshold is set correctly: evaluation Threshold too high: no evaluation

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MT: Set the threshold lower or change the sensor measurement unit. The threshold value is always defined in the measurement unit used. If you measure in pH, the threshold is in pH/mL; and in mV, it is mV/mL. The numerical value of the threshold in pH/mL is much smaller than in mV/mL. The threshold must therefore be adapted according to the measurement unit used.

Reason C: The initial potential is higher than the predispensing to potential.


MT: You compare the set potential value of 150 mV in the predispensing

step of the EQP titration with the ini-tial potential of the titration, which can be read off in the measured val-ue table. This is higher than the set value, so that an equivalence point cannot be evaluated (Table 3).

Explanation:The titrator remains in the predis-pensing step until it has reached the potential of 150 mV. Since the initial potential of 150 mV is already exceeded, the titrator remains in the predispensing step even with increas-ing potential.


MT: Set the potential for the predis-pensing to a lower value.

Reason D: The minimum vol-ume increment (dVmin) is too small.The minimum increment, dVmin, is defined under “Dynamic” in the “Titrant Addition” submenu of the EQP titration. Figures 2a and 2b illustrate the influence of dVmin on the first derivative curve.If the minimum increment, dVmin, is chosen too small, the titration curve is noisy, above all in the region around the equivalence point. This influences the determination of the equivalence point: it is possible that several are evaluated or even none at all; and even if only one is detected, the results show a large variation.

As an example, the variation of the minimum increment in the titra-tion of NH4Cl with NaOH is shown (Table 4).

Table 2: Reason B; maximum of the 1st derivative is below the threshold of 5 pH/mL

VolumemL

IncrementmL

SignalmV

Change mV

1st derivativemV/mL

Timemin:s

ET10.00000.02000.04000.08000.16000.35000.50400.64300.8430

0.02000.02000.04000.08000.19000.15400.13900.2000

159.7160.8162.6165.6171.9189.3205.2217.5230.1

1.11.83.06.3

17.415.912.312.6

54.990.574.379.291.5

103.288.863.0

0:050:100:210:270:320:380:440:490:55

Table 3: Reason C; initial potential is higher than the predispensing potential of 150 mV

VolumemL

IncrementmL

SignalmV

Change mV

1st derivativemV/mL

Timemin:s

ET1

ET2

0.00000.57100.85601.0000

0.57100.28500.1440

2.1002.2482.3482.408

0.1480.1010.060

0.2590.3530.414

0:030:130:220:30

1.28701.50301.64401.74801.82501.88001.93001.9800

0.28700.21600.14100.10400.07700.05500.05000.0500

2.5582.7202.8643.0093.1573.3003.4723.671

0.1500.1610.1450.1450.1480.1430.1720.199

0.5230.7471.0261.3911.9222.5913.4463.977

0:400:501:001:101:191:291:401:50

2.0300 0.0500 3.900 0.230 4.595 2:012.0800 0.0500 4.124 0.223 4.463 2:122.1300 0.0500 4.329 0.205 4.109 2:222.1800 0.0500 4.500 0.171 3.424 2:32

Fig 2a: Titration curve dVmin = 0.005 mL

Fig. 2b: Titration curve with dVmin = 0.05 mL

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In this example the titration with dVmin 0.1 mL also gave the best reproducibility.


MT: Increase the minimum volume increment, dV(min), until a clear equivalence point is obtained. The value of dV(min) must not be too large, otherwise the potential jump disappears, especially if it is small.

Reason E: The value set for the (constant) potential difference per volume increment, dE(set), is too large.The value of dE(set) is defined un-der “Dynamic” in the “Titrant Addi-tion” submenu of the EQP titration. For most applications, the default set-ting of 8 mV for dE(set) can be used. However, if the titration curve is flat with only a very small jump at the equivalence point, it leads to large volume increments, which can cause the potential jump to disappear.


MT: Decrease dE(set) or dVmax until the equivalence point is detected.

Reason F: Wrong tendency. In the equivalence point detection, you can also define a tendency. For example the tendency is positive in a titration with NaOH if you measure in pH. However, if you change to mV,

you must also change the tendency. Table 5 shows the measured value ta-ble of the titration of HCl with NaOH. In the method, the tendency was set to “positive”. The values were measured in mV. This means that the titration curve shows a negative tendency, i.e. the values change from positive to nega-tive. However, since a positive tenden-cy was set in the EQP titration method

function, the potential jump is not in-terpreted as an equivalence point.


MT: Define the tendency as “Nega-tive”, use pH as the measurement unit or select “No Tendency”. The latter is recommended with titration curves that proceed in a clear direction, such as in this case.

dVmin Evaluation Comments

0.005 mL 9 equivalence points Several maxima that were detected as equivalence points

0.02 mL 4 equivalence points Several maxima that were detected as equivalence points

0.05 mL1 or 0 equivalence points

Two maxima of the same height at the equivalence point leads to no evaluation

0.1 mL 1 equivalence point A clear maximum at the equivalence point

Table 4: Variation of the minimum increment in the titration of NH4Cl with NaOH

Table 5: Reason F; wrong tendency (positive instead of negative)

VolumemL

IncrementmL

SignalmV

Change mV

1st derivativemV/mL

Timemin:s

ET1

ET2

0.00000.57100.85601.0000

0.57100.28500.1440

241.9231.2221.3214.0

-10.7-9.9-7.4

-18.7-34.7-51.2

0:030:090:150:21

1.11801.19901.25001.28601.31601.34601.37501.40601.43601.46601.4960

0.11800.08100.05100.03600.03000.03000.03000.03000.03000.03000.0300

205.2195.9187.3178.9168.2149.092.3

-91.6-160.9-179.5-190.0

-8.8-9.3-8.5-8.4

-10.7-19.3-56.7

-183.9-69.3-18.6-10.5

-74.5-114.9-167.3-233.4-357.6-641.9

-1889.1-6130.3-2309.1-620.4-351.1

0:270:330:390:440:510:591:171:482:052:142:28

C. Gordon

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21 CFR part 11 – overviewIn laboratories these days, everyone is talking about 21 CFR part 11. This article shows what this regulation of the American Food and Drug Administration means in practice.

What is 21 CFR part 11?This term is nothing new for those in-strument users in the pharmaceutical industry. It is a regulation passed by the American Food and Drug Admin-istration (FDA) providing the criteria under which the FDA will consider electronic records to be equivalent to paper records, and electronic signa-tures equivalent to traditional hand-written signatures. It applies to any US pharmaceutical or healthcare company or any pharmaceutical or healthcare company exporting or wishing to export to the USA.The purpose of the regulation is to prevent accidental alterations to records, to deter deliberate falsifi-cation of records, and to help detect such alterations when they do occur. No features in any system can guar-antee prevention of deliberate manip-ulation. As stated in the preamble to the regulation:“... people determined to falsify records may find a way to do so de-spite whatever technology or prevent-ative measures are in place.”

Can an analytical instrument system be 21 CFR 11 compliant?In order for a company to comply with the regulation, it is a require-ment that the organization using electronic records and signatures has Standard Operating Procedures (SOPs) in place that support and complement those features within the analytical system. In addition it is imperative that all users of such

systems are trained on their use and the overall implications of 21 CFR part 11. Instrumental analysis sys-tems themselves can therefore not be compliant but can have features that support compliance. The final responsibility for com-pliance lies with the users of such systems.

DefinitionsBefore examining the regulation in any detail it is necessary to define some terms used:

Closed system Means an environment in which sys-tem access is controlled by persons who are responsible for the content of the electronic records that are on the system.

Electronic record Is any combination of text, graphics, data, audio, pictorial, or other infor-mation representation in digital form that is created, modified, maintained, archived, retrieved, or distributed by a computer system.

Electronic signature Means a computer data compilation of any symbol or series of symbols ex-ecuted, adopted, or authorized by an individual to be the legally binding equivalent of the individuals hand-written signature.

The regulation in detailA titration system comprising one or several instruments attached to a

computer running a dedicated soft-ware package falls into the category of a closed system as defined above. An open system on the other hand is one that can be accessed from out-side the company and is not entirely under the control of those responsible for the data. For such systems there are other controls to consider such as encryption of data. Here, we will only cover those topics relevant to closed systems.

21 CFR part 11 essentially covers two topics. The first is that of electronic records and the second concerns elec-tronic signatures.

Electronic recordsSubpart B of the regulation deals with electronic records. Under this section there are items that refer to controls outside the responsibilities of the ven-dor. These include:• Ensuring that any systems used

are validated to ensure accuracy, reliability, consistent intended performance, and the ability to discern invalid or altered records. Naturally it is expected that the vendor support this validation procedure with all required docu-mentation.

• Ensuring that persons using the system have the necessary edu-cation, training and experience to perform the assigned tasks. Again, the vendor can offer assist-ance with training of personnel.

• Establishing written policies holding individuals accountable for their actions initiated under their electronic signature.

Where the vendor can provide support within their products is to provide a system that can:• Generate accurate and complete

copies of records in both human readable and electronic form suit-able for inspection, review, and copying by the agency (FDA).

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• Ensure protection of records to enable their accurate and ready retrieval throughout the records retention period.

To ensure compliance with both of the above points, the METTLER TOLEEDO LabX titration software employs a protected SQL database to store all raw data, methods, calcu-lated results and statistics.

shall be available for agency review and copying.

In the LabX software the audit trail is retained as part of the database. It can be filtered for viewing and print-ing and can be exported as a read-only HTML document. Naturally, only a system administrator has the necessary permission to do any of the above.

Electronic signatureSubpart C covers the requirements for electronic signatures. The main points here are that:• electronic signatures shall be

unique to one individual• they shall employ at least two dis-

tinct components such as identifi-cation code and password controls must be in place to cover attempt-ed misuse.

Points 11.50 and 11.70 cover the sign-ing of electronic records and state

LabX: Selectable user rights

LabX: Complete audit trail

LabX: Electronic signature entry

The LabX software also allows the system administrator to configure access rights and permissions for four user groups and then to assign each user to one of the groups. Each user is required to log on to the system us-ing a unique user ID and password, and after doing so, will only be able to access those areas determined by the administrator.

Perhaps one of the most important points in Subpart B of 21 CFR part 11 is that systems have a secure, computer-generated, time-stamped audit trail to record any operator ac-tions that result in a change in the database. This audit trail must be re-tained with the electronic records and

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that these records shall clearly indi-cate the printed name of the signer, the date and time when the signing was executed as well as the meaning of the signature. With the LabX system, any changes, additions or deletions from the da-tabase require a signature togeth-er with the reason the changes were made. This signature data is stored in the database together with the records.

An additional requirement in 11.200 is that when an individual executes a series of signings, the first sign-ing shall be executed with both components (ID and password). Any subsequent signings in the same ses-sion must employ at least one component. This is the case with LabX where subsequent signings re-quire only the input of the password.

Prevention of unauthorized accessSubpart C also covers controls for identification codes and passwords. The main points covered here are:• the combination of identification

code and password must be unique for each individual,

• passwords must be periodically revised

• it must be possible for the ad-ministrator to take actions when a password is lost (forgotten) or stolen, and

• attempted misuse of passwords must be reported.

LabX allows only unique combi-nations of user ID and password. When logging on to the system, the user must enter both. If an incorrect entry is made such as a wrong pass-word is entered, an entry is made in the audit log and the user is notified of the error. If three incorrect entries are made the user account is disabled and can only be reactivated by the administrator.LabX employs the above plus ad-ditional possibilities for password controls. In addition to those listed in the regulation, LabX allows the specifying of a time controlled au-

tomatic logout of the user, an enforced password his-tory, a minimum password length and an additional password complexity re-quirement to enforce the use of alphanumeric char-acters and symbols.

Although an analytical system itself cannot be 21 CFR part 11 compliant, the LabX titration system from METTLER TOLEDO provides all the necessary features to support any or-ganization where 21 CFR part 11 is the buzzword and compliance is a way of life.

LabX: Definition password policy

LabX: Invalid Login

Ch. Bircher

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Titration - fully networkedIf several titrators are in use at one location, linking the instruments together in a client/server network offers many advantages – better data security, more efficient maintenance and faster control.

Let us assume you have three titra-tors; two are in the laboratory and one in production. All the instru-ments routinely perform the same analyses. If the instruments are not linked in a network, you continu-ally have to make sure that the same versions of the methods are being used. For example, when methods are modified, all three instruments have to be updated. If you use PCs to control the titrators, you can at least transfer methods from instrument to instrument via disks or similar me-dia – simple operations certainly, but time-consuming and prone to errors. The backup and checking of data is also a laborious task: instrument for instrument, everything has to be done manually.The whole procedure is so much eas-ier, more efficient and of course done more reliably if the titrators are linked in a network by means of client/server titration software such as LabX profes-sional. Each titrator is then connected to a PC (the client). Instruments that are close to each other can be con-nected to the same PC. So, in our example, the two lab titrators need only one PC. Any existing company network can be used as the network. The titration server is defined on one of the PCs or on a central file server. This server is from then onward the (invisible) control center for all titra-tions: it automatically manages all the methods, results and settings. If a method is modified on one system, it is immediately available to all the others! Furthermore, the task of back-

ing up of all the titration data is really easy. Simply back up all the data on the server.Full client/server networking however offers even more: all the authorized users on the network have access to the titration results. Rapid evalua-tion of results in the office becomes a reality! And if an operator needs help because a titration for once does not run as planned, the titrations current-ly being performed can be examined in real time on every PC – including the online titration curve. This func-tion can of course also be used for monitoring purposes: you can, for example, start a series of 20 samples and then continue working on an HPLC instrument at another place in the laboratory. Via the network, you can check at any time whether the

samples are running properly with-out going across to look at the titra-tion system.What is needed to set up a titration network? In general, the basic system needs a normal company network based on Windows NT, 2000 or XP. It can also be used as a server that performs other tasks in the network. Client PCs can control all the DL5x and DL7x series titrators as well as the DL38/31 models. Support for the DL39/32 instruments is in prepara-tion. Basically, a LabX professional license must be installed on every PC that is used to control titrators or edit data. An additional server license is however not required. Configuration of the network is easy: when a client is installed, the name of the server used is simply entered.

Fig. 1: Example of networked titration. Assuming the user has appropriate authorization, he can access every titrator and all the data from any PC via the network. A network server serves as a central data storage device.

LabX

LabX

LabX

LabX

Production

Quality Manager

Lab

Data evaluation

Methoddevelopment

Titration/data acquisitionCentralLabX Server

PC withLabX

PC withLabX

PC withLabX

DL58

DL70ES

DL58 withRondo 60

DL77 with Quanto

P. Wyss

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A p p l i c a t i o n s

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Efficient quality control of liquids with density or refractive index determination

Quality control of liquid samples without the measurement of density and refractive index is difficult to imagine today. Digital instruments have helped to make the determination of these two quantities be-come much more important. Density and refractive index are often determined at the same time. The measurement of both values makes the result more meaningful and can also be used to determine the concentration of multi-component mixtures. This article describes a number of examples of such applications.

These days, an optical Abbé refrac-tometer or a modern digital re-fractometer is part of the standard equipment of practically all labora-tories. The reason for this is obvious: refractive index determination is usu-ally the simplest and fastest method to characterize liquid samples.Density measurement has also long been used for the quality control of liquids. Refractometry is, however, appreciably more popular than den-sity measurement in quality control because the accurate determination of density with a pycnometer and analytical balance takes appreciably more time than the determination of refractive index. Even the introduc-tion of modern digital density meters has hardly changed the situation – high resolution digital refractom-eters are usually less expensive and easier to operate than digital density meters.

Concentration determination in two-component mixtures with density and refractive indexBoth refractometry and density meas-urement are used to determine con-centration. A classic example is the determination of the alcohol content in pure alcohol/water mixtures. This

determination is usually done by density measurement. One reason for this is that up until now hydrometers have normally been used that allow the alcohol concentration to be read off directly. In contrast, refractometry is normally used for the determina-tion of the water content of glycerol or the sugar content in syrup. Both these products are relatively viscous, so that the determination of the refractive in-dex is appreciably easier to perform than a density measurement.

Concentration determinations us-ing density and refractive index with high resolution digital instruments are generally very accurate. For ex-ample, the determination of the water content of pure 1-propanol or metha-nol with density and refractive index yields results with an absolute accu-racy of at least 0.1 weight percent. In addition, these methods have the fol-lowing important advantages:1. Water content determination with

density and/or refractive index takes less than two minutes.

2. No chemicals are required, in con-trast to other methods for water content determination (e.g. Karl Fischer titrations). The density/refractive index method is there-fore more ecological and economi-

cal than most other methods.3. The determination is non-destruc-

tive. The same sample can also be used for other analyses.

The principle of the method is sim-ple: modern digital density meters and refractometers are able to use concentration tables (see Table 1). If a density or refractive index concen-tration table is entered in the instru-ment, the calculation of the water content is done automatically using first- to third-order polynomials and the water content displayed directly in percent. Tables for concentration determinations with density and re-fractive index can be obtained from the literature or downloaded from the Internet (www.density.com and www.refractometry.com).

Quality control by means of the simultaneous determination of density and refractive indexIn the goods receiving of organic solvents, samples are checked to en-sure that quality is maintained, i.e. that the composition of the samples is always the same. In the quality control of industrial-quality alcohol denatured with isopropanol, it is not just the water content of the product that is of interest. It is rather to check that the product does not contain any other substances apart from ethanol, isopropanol and traces of water. One possible method for the quality con-trol of solvents is a Karl Fischer water content determination and an analy-sis of the same sample with gas chro-matography. For economic reasons, however, such a time-consuming method can hardly be justified for the in-goods control of organic solvents. If, namely, the den-sity and refractive index of a solvent are determined with a resolution of 4 to 5 places, and if both quantities are within the specifications for the product, then it can be confidently

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assumed that the composition of the sample corresponds to that expected for the solvent. In many industries, quality control of liquid samples with density and refractive index measure-ment is already a standard method. Manufacturers of perfumes and fra-grances, for example, specify these two quantities in their technical data sheets. The end user only needs to de-termine the density and the refractive index of the products to ensure that quality is maintained.

The availability of high resolution digital instruments has resulted in density and refractive index deter-mination being used more and more frequently for the quality control of homogeneous liquids of clearly defined composition. This has led

METTLER TOLEDO to introduce the DR45 combined meter, an instru-ment that determines both quanti-ties simultaneously.

Concentration determinations in multi-component mixtures with density and refractive index measurementIn many cases, density and refrac-tive index measurement is used to determine the concentration of particular constituents of multi-component mixtures. This assumes that the density and refractive index of the samples is only influenced by the constituents whose concentrations are to be determined. In such cases, the calculation of the concentrations is performed with empirical formu-las that are usually determined with

multiple regression analysis: the den-sity and refractive index of samples of known composition of particular con-stituents are measured and the calcu-lation formula for the concentration of the corresponding constituents is determined using regression analysis with the unknowns. The formulas ob-tained are, of course, only valid for a certain composition of the samples.

An example of such an application is the determination of the alcohol, extract and wort content in beer analysis. Previously the density and refractive index of the beer was deter-mined with pycnometers and Abbé re-fractometers. The alcohol and extract content were then determined using nomograms (graphical displays of the three concentrations as a function of density and refractive index).The availability of digital instruments for the simultaneous measurement of density and refractive index has made these determinations much easier:• a measurement takes less than 2

minutes.• the instrument can calculate and

display the desired results (alco-hol, extract or wort content) di-rectly. The relevant calculation formulas can be found in the lit-erature.

Table 1: Concentration table for 1-propanol and methanol. The results were calculated with a third order polynomial. The accuracy of both determinations is very apparent.

Water content[% w/w]

Density (20°C)[g/cm3]

Error[% w/w]

Refractiveindex n 20 D

Error[% w/w]

18.00 0.8416 -0.03505 1.3379 0.02077

16.00 0.8365 0.01215 1.3372 -0.05200

14.00 0.8312 0.01147 1.3365 0.03102

12.00 0.8259 0.04003 1.3357 0.01508

10.00 0.8204 0.02512 1.3348 -0.05185

8.00 0.8148 0.00593 1.3339 0.06884

6.00 0.8089 -0.08612 1.3328 -0.01140

4.00 0.8034 -0.00369 1.3316 -0.06230

2.00 0.7976 0.00826 1.3304 0.05477

0.00 0.7917 0.02189 1.3290 -0.01291

Water content[% w/w]

Density (20°C)[g/cm3]

Error[% w/w]

Refractiveindex n 20 D

Error[% w/w]

16.00 0.8390 0.00728 1.3825 -0.00459

12.00 0.8306 0.00162 1.3835 0.02905

8.00 0.8218 -0.04643 1.3843 -0.07926

4.00 0.8130 0.05739 1.3848 0.08589

0.00 0.8034 -0.01986 1.3852 -0.03108

1-Propanol

Methanol

Figure 1: The DR45 combined density/refractometer

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Gas-phase extraction and coulometric determination of water with the new Stromboli/DL39 automation system

The new Stromboli/DL39 KF automation system is both easy to use and an (in)valuable aid for efficient sample processing. Invaluable as far as applications and simplicity of operation are concerned, but affordable as an investment that quickly more than pays for itself. How does it work? Read all about it below!

IntroductionThe selective and accurate determi-nation of water content is absolutely essential for the quality control of food and plastic products, for infor-mation on the shelf life of pharma-ceutical products or for monitoring the properties of transformer oils, switching oils and hydraulic liquids. The relatively low quantities of water present in the large variety of differ-ent samples are usually determined by coulometric Karl Fischer (KF) titration in combination with a dry-ing oven. The oven allows the water to be se-lectively separated from the sample matrix and transferred to the titra-tion vessel via the gas phase. The technique eliminates the influence of the sample matrix on the KF titra-tion and allows a clean and quan-titative determination of the water content. This elegant method can be used for a large variety of applica-tions and is particularly well suited for automation.

The principle of gas-phase extraction Let us make the following compari-son: If you want to extract water from a solid matrix, you use an anhydrous solvent in which the water dissolves

easily, but in which the solid itself is insoluble. Shaking and stirring accel-erates the extraction. With gas-phase extraction, a dry carrier gas replaces the anhydrous solvent, and heating and carrier gas flow replace shak-ing and stirring. The water passes from the heated sample into the gas phase and is then transferred by the flow of carrier gas into the titration cell connected to it. The concentra-tion gradient formed leads to further extraction and vaporization of water, which is continuously removed until the sample is completely dry. The drying temperature and the choice of carrier gas (air or inert gas) depends on sample properties such as temperature or sensitivity toward oxidation, or how the water is actu-ally bound (e.g. as adsorbed water or water of crystallization). The carrier gas used must of course be dried over silica gel and molecular sieves. The water absorption capacity of the gas is then very high and ensures that the extraction process is efficient.

Gas-phase extraction automated with StromboliTo increase reproducibility and effi-ciency and reduce costs, one would of course like to automate the analysis process as much as possible. How can

this be done with a KF drying oven without introducing too much tech-nical complexity and in such a way that the user can still easily operate the system? Let us have a look at the Stromboli automated system in more detail:

How are the samples prepared?With Stromboli, the samples are weighed into sample vials that have a working volume of up to 20 mL; if necessary, the vials can be sealed with adhesive aluminum foil and closed with a rubber cap. This does not require any special tools or par-ticular skill. The aluminum foil seals the vials very tightly and allows a number of samples to be prepared beforehand and then measured later in a series. Besides this, the rubber caps and sample vials are reusable, and all three parts can be disposed of separately afterward. In summa-ry, sample preparation is completely reliable, straightforward and user-friendly.

How are Drift and Blank value corrections performed? Accurate determination of the water content from different samples ma-trices requires that the residual mois-ture content of the dry carrier gas and the amount of moisture adsorbed in the empty sample vials are known. These two factors, i.e. the drift mul-tiplied by the duration of the titra-tion and the blank value contribute to the total amount of water titrated and have to be subtracted for the calcula-tion of the result. Stromboli has spe-cial Drift and Blank positions for vials on the sample rack that allow these two values to be determined au-tomatically before the water content of the up to 13 samples is determined. You can decide whether you want to integrate the drift or the blank deter-minations into each sample series or

H.-J. Muhr

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determine them separately by select-ing the appropriate method param-eters in the DL39 coulometer.

How is the sample, i.e. the sample vial, transferred into the oven, how is carrier gas flow supplied to the sample, and how does the system change to the next sample? Important questions – a simple and straightforward answer: Stromboli does it all for you. The upper part of the oven has a carrier gas supply sys-tem that consists of a delivery tube, a narrow glass tube with a sharp tip and an outlet, a small hole bored im-

mediately next to the glass capillary. This leads to a second glass tube that is connected to the titration vessel via the transfer tube (Fig. 5b). The cir-cular drive plate on the rack moves the sample vial to the lift directly below the oven (Fig. 5a, step 1). The lift then transports the vial into the oven, the tip of the glass tube pierces the aluminum cap, and the vial with the rubber cap is pressed against the upper part of the oven (Fig. 5a, step 2 and 3). The rubber cap seals the sample vial/carrier gas flow system completely and ensures that the wa-ter evolved is transferred without loss into the titration cell (Fig. 5b, step 4).

After the titration is completed, the lift returns the sample to the starting position and the next sample vial is moved into position.

What about instrument opera-tion? Do you have to specially program the sequence of automated operations with Stromboli?Stromboli is controlled exclusively via the oven method in the DL39 titrator. All the factors such as drift and blank value determination, set temperature and titration parameters as well as calculations are defined in a method template and stored as a user method.

Fig. 2: Detailed viewof the Stromboli-sample vial

Fig. 1: The Stromboli/DL39 KF automated system

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components from the sample that could simulate a water content are eliminated. This means that reli-able results are obtained and no time-consuming optimization ex-periments have to be performed.

• Since only desorbed water is de-termined, the titration cell and its electrodes are not contami-nated by the sample. Carry-over and memory effects of previous samples are therefore excluded and the cell remains clean for a long time. This in turn means that the reagent does not have to be changed so frequently, thereby reducing costs.

• The simple and reliable sample preparation and its automated processing in series with Strom-boli results in a significant saving of time, increased efficiency and in addition leads to a marked im-provement in the reproducibility of the results.

• The simplicity and user-friendly operation of the Stromboli/DL39 system, the fact that everything is controlled via a method as well as the easy handling mean that the technique can be readily adapted to routine use. Optimization ex-periments to prepare standard operating procedures as well as validations can be carried out rapidly and reliably.

And by the way: wait until you see how compact the system is!

You simply select the method, enter the number of samples and sample weights, e.g. via a balance, press the start key and off it goes! When the analysis is completed, the drift and blank values are automatically tak-en into account in the calculation of the result. It could not be easier, more comfortable or more reliable.

What about the results and reproducibility?Stromboli allows water to be ex-tracted from the most varied types of sample in an oven temperature range of 50 to 300 °C. The sample weight used depends on the water content of the sample, and the analysis time on the rate at which the bound water is released. The following table dem-onstrates the power of the technique with regard to different types of appli-cations that can be easily automated with Stromboli. The shorter analysis and preparation times per sample and the reproducibility of the results are immediately apparent.

SummaryThe automated gas-phase extraction followed by the coulometric analysis of water is a technique that can be almost universally employed. It of-fers a number of important advan-tages and uses:• The desorption of the water from

the sample matrix means that the sample matrix has no influ-ence on the titration, i.e. possible interfering side reactions due to

Fig. 3. Schematic diagram of sample preparation

Fig. 4. The special Drift (blue) and Blank (red) positions on the Stromboli sample rack

1 2 3 4

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Table 1: Results of water content determinations with Stromboli

Sample Weight [mg]

Result [ppm] n srel

[%]Temp. [°C]

Titration time [min]

PP film 500 2743 4 1.20 170 10

PE granule 800 1858 3 3.10 200 20

Motor oi 1200 316 5 4.50 170 12

Al2O3 450 6072 6 0.80 250 10

BaCl2 •2H20 30 14.77% 7 1.90 220 11

Washing powder 50 13.80% 5 1.10 150 10

Pentaerythritol 80 3.14% 3 0.97 110 12

Fig. 5a: Operation of the Stromboli sample changer

Fig. 5b:Detail view of the Stromboli mechanism

H.-J. Muhr

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Efficient analysis of potable water with QUANTO aliquot

A typical example of an automated system installed in a potable water laboratory in Canton St. Gallen, Switzerland, consisting of QUANTO aliquot and a DL70ES titrator – the ideal solution for fully automating complex titration applications with high sample throughput.

IntroductionIn the quality control of potable wa-ter, a number of different character-istic values have to be determined at regular intervals. Besides the bacte-riological quality, these include the determination of chemical compo-sition. This is done by measuring values such as the electrical con-ductivity, pH, acid and base capacity, total hardness as well as the concen-tration of various ions. Reliable measurement data and results are needed that will satisfy the strict official requirements and standards. This necessitates the use of a robust and flexible analytical technique such as titration, which, when suitably automated, can cope efficiently with the large number of samples typically received for analysis in water laboratories.

Requirements for analysis and automationThe customer wanted to determine the following values in differ-ent samples of drinking water:• electrical conductivity in µS/cm• pH value • carbonate hardness in mg/L and

French hardness degree (F)• calcium concentration in mg/L

and French hardness degree (F)• magnesium concentration in

mg/L and French hardness de-gree (F)

• total hardness calculated in French hardness degree (F)

The system should be able to per-form the measurements fully auto-matically with a sample volume of 50 mL and a throughput of up to 60 samples. The total analysis time including sampling, taking aliquots, titration, disposal and rinsing should not exceed 15 minutes per sample. The system should be able to cope flexibly with varying concentrations of the individual constituents, and also be so easy to use that a semi-skilled person can operate it.The only instrument combination that can in fact really satisfy these requirements is the DL70ES-QUANTO aliquot system – the DL70ES titrator automates the titrations and meas-urements while the QUANTO aliquot sample changer takes care of the en-tire sample handling from the initial sampling through to the disposal of the up to 60 samples (Fig. 3) The analysisThe analysis process consists of two measurements and two titrations, one of which requiring the dosing of an auxiliary reagent for setting the pH value. The conductivity is measured with the InLab 730 conductivity probe, which is connected via the combined MPC227 pH/conductivity meter to the DL70ES titrator. A DG111-SC electrode is used to measure the pH value and for the following endpoint titration to pH 4.3 with 0.05 mol/L hydrochloric acid, which is used to

determine the carbonate hardness. Calcium and magnesium are deter-mined by equivalence point titration with 0.05 moL/L EDTA after setting the pH to 8.5 with tris buffer (0.1 moL/L acetylacetone and 0.2 moL/L tris(hydroxymethyl) aminomethane [THAM]) using the DX240 calcium ion-selective electrode and DX200 reference electrode.

Automated volume measurement and cleaning with QUANTO aliquotIn QUANTO aliquot, a volume ad-justment unit is used for the rapid and precise measurement of large sample volumes in the range 20 to 60 mL (Fig. 1)

The unit is, in principle, an overflow system consisting of a titration beak-er, a valve unit and a bi-directional peristaltic pump that connects a nee-dle, movable in the xyz-direction, to the valve unit. The overflow system has to be calibrated beforehand in order to accurately determine the sample volume. The easiest way to do this is to titrate a primary standard substance in solution with a titrant adjusted beforehand to the primary standard.

The volume measurement process proceeds as follows: An excess of sample solution is pumped into the titration beaker via the needle dipping into the sample so that the sample inlet at the titration head dips into the solution. Afterward the needle is moved to the waste bot-tle, the pumping direction reversed and the excess solution sucked out to the level of the sample inlet. When the titration is completed, the sample solution is drained out under suction through the sample outlet of the titra-tion beaker and the unit thoroughly cleaned by repeating the process for volume measurement with rinsing water from the container.

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the ionic strength of the sample solu-tion. This is done by means of a flow cell integrated in the volume adjust-ment unit during sample transfer, hich is interrupted for the actual measurement. Since the measuring cell is part of the volume adjustment unit, the next rinsing sequence en-sures that the cell is thoroughly rinsed (Fig. 2).

Fully automated analysis sequenceMeasurements and determinations are processed according to the fol-lowing sequence:

The volume measurement and cleaning sequences of QUANTO al-iquot are permanently programmed. The DL70ES titrator communicates via input and output signals with QUANTO aliquot. The fixed auto-mation sequences are synchronized with the titrator method by position-ing these signals appropriately in the method sequence.

Separate conductivity measurementThe electrical conductivity is meas-ured separately in order to eliminate factors that might possibly influence

1. Rinsing of the volume adjustment unit of QUANTO aliquot

2. Sampling3. Measurement of conductivity4. Taking sample aliquots of 50 mL 5. pH measurement6. Titration with 0.05 moL/L HCl7. Dosing tris buffer 8. Titration with 0.05 moL/L EDTA9. Removal off the waste (titrated)

sample under suction10. Back to step 1

First the method is started at the titrator with the desired number of samples and then the rinsing and subsequent sampling sequence of QUANTO aliquot after entering the position of the first sample and the number of samples. When all the samples have been processed and the final rinsing is completed, rinsing solution is pumped into the titration beaker. This prevents the electrodes from otherwise drying out if the sam-ples are processed in unattended op-eration, e.g. overnight.

ResultsTable 1 very impressively demon-strates the performance of this highly automated system. In particular, one should note the excellent reproduc-ibility, which is, in part, due to the very precise volume measurement.

Fig. 1: Schematic diagram of the volume adjustment unit

Fig. 2: Flow cell with integrated conductivity sensor

Valve unit

SP250Peristaltic pump

Y piece

Sample outlet

Glass titrationbeaker

Sample inletlevel adjustment

Stainlesssteel needle

Valve 2

Valve 1

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N e w p r o d u c t s

ble water samples from the region St. Gallen were entirely fulfilled with the DL70ES-QUANTO aliquot auto-mated system. The system offers the following features, which are of great benefit to the customer:• Robust and simple operation,• Flexibility due to the expandabil-

ity of the DL70ES titrator: by using

In addition, an analysis time of 15 minutes per sample including sam-pling and rinsing was achieved by optimizing the titration parameters (Table 1).

SummaryThe specific requirements of the customer for the analysis of pota-

an additional burette to dispense a different concentration of EDTA and with the aid of conditional functions, the right concentration of titrant could be automatically used for higher or lower degrees of hardness.

• The speed and precision of QUANTO aliquot volume meas-urement, which results in excel-lent reproducibility and valuable saving of time.

• Enormous increase in efficiency through collecting a series of samples and processing them in one operation.

All in all, the system is an excel-lent investment that will soon pay for itself!

Result Description Mean value of 9 samples Units srel [%]

1 Conductivity 323.100 µS/cm 0.539

2 pH value 8.127 pH 0.716

3 Carbonate hardness 75.550 mg/L 0.679

4 Carbonate hardness 12.601 F 0.679

5 Ca concentration 49.975 mg/L 0.788

6 Mg concentration 7.646 mg/L 0.977

7 Ca content 12.474 F 0.788

8 Mg content 3.149 F 0.975

9 Total hardness 15.623 F 0.689

Table 1: Results of a series of nine potable water samples

Fig. 3: DL70ES with QUANTO aliquot

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New productsMETTLER TOLEDO is delighted to present a number of interesting new products.

Rondolino – the practical automatic titration standWith Rondolino, titration becomes faster, easier and more accurate – with the minimum of

expense. The installation could not be easier – simply connect Rondolino to a titrator of the DL5x series. There is no need to configure anything. Rondolino can independently process up to nine samples. But it even pays to use Rondolino for individual samples: the electrodes are always automatically cleaned (especially thoroughly with the op-tional PowerShower™ rinsing system) and returned to the conditioning beaker after completion of the titration. This ensures accurate results and protects the electrodes.

Rondolino saves laboratory space – it requires hardly any more space than a conven-tional titration stand.

The DL50 Rondolino is an especially attractive package consisting of Rondolino together with the METTLER TOLEDO DL50 entry-level titrator.

Rondolino and the DL50 Rondolino were introduced in October 2001.

LabX – the new standard for titration software The first time you start LabX you will be surprised by the simplicity and design of the program. When you begin to use the software, you will be amazed at the power hidden below the elegant and straightforward user interface: titrator control, method editor, sample series editor, hi-erarchical results database, statistical functions, control charts, possibilities for post-evaluation/post-calculation and a lot more are already included in the light version of LabX supplied with every METTLER TOLEDO titrator since January 2002.With the LabX professional version, you obtain additional functions that were not available before in any titration software on the market: full 21 CFR part 11 support (user-manager, electronic signature, audit trail, etc. see also page 8 on this subject), client/server network capability (see page 11 on this subject) and much more. And as an option to LabX professional, a comprehensive validation package can also be supplied that saves a lot of time and expense for the obligatory on-site validation. LabX is also available as LabX multi, a version that includes three licenses.

All LabX software versions have been available since January 2002.

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Coulometry has never been easier – the DL39/DL32 CoulometersThe two brand new DL32 and DL39 coulometers are based on the very successful design of the DL31

and DL38 Karl Fischer volumetric titrators. The two instruments offer the same, intuitive operator guidance including the well-proven Hello menu and context sensitive help functions.Both instruments can be supplied with the classical titration cell with diaphragm and with the newly designed METTLER TOLEDO cell without diaphragm. Besides ease of maintenance, the cell without diaphragm provides exceptionally high accuracy and offers a wide range of application possibilities. Even the measurement of oils – up until now extremely difficult with

diaphragmless cells – is no problem at all. METTLER TOLEDO therefore recommends the cell without diaphragm for universal use.

The DL39 and DL32 coulometers have been available since January 2002.

Coulometry simply fully automatic – the Stromboli oven sample changer Up until now, there have been few successful approaches toward automating coulometry. The systems on the market are complicated to use and are also large and expensive.The new Stromboli oven sample changer is easy to use, small and no more expensive than the titrator that goes with it. The operation of the instrument system is amazingly simple: Stromboli itself has no operating controls other than the on/off switch. You connect it to the DL39 titrator, load up to 15 sample vials (including blank value and drift determination), select a predefined Stromboli method on the titrator and start it ... the samples are then automatically processed. The sample vials can be sealed without the use of special tools and can be re-used after the measurement.

Stromboli has been available since March 2002.

DR45 – Density meter and refractometer in oneIn quality control it is often desirable to measure not only the density or

the refractive index, but to measure both at the same time. The new METTLER TOLEDO DR45 provides a really elegant solution. What from the outside looks just like a normal METTLER TOLEDO density meter, on closer inspection turns out to be a combined density meter and refractometer.

The DR45 will be available from June 2002 onward.

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SC1 und SC30 – determine density, refractive index or both values efficiently The new SC1 and SC30 sample delivery and cleaning units make the determination and of density, refractive index or of both values even easier, faster and more reliable with the METTLER TOLEDO DE den-sity meters, RE refractometers and DR45 combined meter. The SC1 single-sample and the SC30 multi-sample automation units not only reduce the manual work involved in performing measurements by up to 90%, they also help to detect measurement errors and to save clean-ing solution.Our new “Quality control of liquid products” brochure shows you how you can reduce the work involved in performing your density and refractive in-dex.

SC1 and SC30 will be available from July 2002 onward.

CoverUp™ – elegant cover system for Rondo 60Some titrations have to be done in a fume hood. Fume hood space is however often restricted and expensive. For the Rondo 60 sample changer there is now an elegant solution – the CoverUp™ System: An arm fixed to the Rondo 60 automatically covers and uncovers the titration beakers in the sample rack. Thanks to a unique magnet mechanism, the CoverUp™ system oper-ates extremely reliably and almost maintenance free. Any Rondo 60 with a 20-place sample rack can be upgraded with the CoverUp™ system.

CoverUp™ has been available since January 2002.

DH100 – precise titration at higher temperatureTitration at higher temperature is not without its problems because it is often difficult to main-

tain the contents of the titration beakers at a constant, predefined temperature. The DH100 heating system is the answer. It consists of a heating element made of chemically resistant Hasteloy C, a sensor and a control unit. Depending on the titrator connected, it allows a sample to be heated fully automatically and precisely to a predefined temperature of up to 100 °C before the titration and then held at this temperature. The heating element is immersed directly in the sample, allowing efficient and rapid temperature control.

The DH100 heating system has been available since March 2002.

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P u b l i c a t i o n s

Layout and productionPromotion & Documentation, Peter Ackermann© 05/2002 METTLER TOLEDO GmbH

ME-51710185

Printed in Switzerland

Printed on 100% chlorine-free paper.For the sake of our environment.

Editorial officeMETTLER TOLEDO GmbH, AnalyticalSonnenbergstrasse 74CH-8603 Schwerzenbach, SwitzerlandTel. ++41 1 806 7711Fax ++41 1 806 7240E-Mail: [email protected]: http://www.titration.net

Authors: Dr. A. De Agostini, Dr. Ch. Bircher, A. Aichert, C. Gordon, Dr. H.-J. Muhr, P. Wyss

The application chemists of the Analytical Chemistry market support group have prepared several publications and a series of applica-tion brochures to support customers in their routine work in the laboratory. Each brochure is dedicated either to a particular branch of industry (such as paper, petroleum and beverages), a particular titrator or a specific analysis technique. The following list shows all the publications together with their order numbers. They are available from your local METTLER TOLEDO marketing organization.

Publications, reprints and applications German English

Titration in routine and process investigations 51724658 51724659Basics of Titration 51725007 51725008Fundamentals of Titration 704152 704153

Applications Brochure 1 Customer Methods 724491 724492Applications Brochure DL70 Gold and Silver 724613Applications Brochure 2 Various Methods 724556 724557Applications Brochure 3 TAN/TBN 724558 724559Applications Brochure 5 Determination in Water 51724633 51724634Applications Brochure 6 Direct measurement with ISE 51724645 51724646Applications Brochure 7 Incremental Techniques with ISEs 51724647 51724648Applications Brochure 8 Standardization of titrants I 51724649 51724650Applications Brochure 9 Standardization of titrants II 51724651 51724652Applications Brochure 11 Gran evaluation DL7x 51724676 51724677Applications Brochure 12 Selected Applications DL50 51724764 51724765Applications Brochure 13 Nitrogen Determination by Kjeldahl 51724768 51724769Applications Brochure 14 GLP in the Titration Lab 51724907 51724908Applications Brochure 15 Guidelines for Result Check 51724909 51724910Applications Brochure 16 Validation of Titration Methods 51724911 51724912Applications Brochure 17 Memory card “Pulp and paper” 51724915Applications Brochure 18 Memory card “Standardization of titrants” 51724916 51724917Applications Brochure 19 Memory card “Determination in Beverages” 51725012 51725013Applications Brochure 20 Petroleum 51725020Applications Brochure 22 Surfactant Titration 51725014 51725015Applications Brochure 23 KF Titration with DL5x 51725023Applications Brochure 24 Edible oil and fat 51725054Applications Brochure 25 Pharmaceutical Industry 51710070 51710071Applications Brochure 26 METTLER TOLEDO Titrators DL31/38 * 51709854 51709855Applications Brochure 27 KF Titration with Homogenizer 51725053Applications Brochure 29 Applications with the METTLER TOLEDO Rondo 60 51710082Applications Brochure KF Chemical 724353 724354Applications Brochure KF Food, Beverage, Cosmetics 724477 724478Applications Brochure KF 10 DL35 Applications 724325 724326Applications Brochure DL18 724589 724590Applications Brochure DL12 724521Applications Brochure DL25 724105 724106Applications Brochure DL25 Food 51724624 51724625Applications Brochure DL25 Petro / Galva 51724626 51724627Applications Brochure DL25 Chemical 51724628 51724629

* Also available in French (51709856), Spanish (51709857) and Italian (51709858)

information for users of titration and ph systems, density ... · and ph systems, density meters...

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