2013 pittcon presentation
TRANSCRIPT
Reagent Strips for the Detection of High Range Total Alkalinity
and Phosphate in Various Water Samples and
Coolants using Handheld Photometers
By Balaji Tatineni
Abstract 2370 – 2 Thursday March 21, 8:20 am
STRIPS VISUAL STRIPS Test strip: Aperture strip - REAGENT STRIP:
Total Alkalinity !• Alkalinity is a measure of the “acid neutralizing capacity”
• Important compounds for Alkalinity are:
H+ Hydrogen ion (acid) OH- Hydroxide ion (base)
H2CO3 Carbonic acid
HCO3- Bicarbonate ion
CO32- Carbonate ion
CaCO3 Calcium Carbonate (Calcite)
CaMg(CO3)2
Dolomite lime
Continuation…. Low alkalinity can result in rapid pH changes, if acid or base
enters the water
Most streams and lakes of western Oregon and Washington have low alkalinity due to the volcanic geology of the Cascade Mountain Range --- less time to interact with the geology
Wastewater have higher alkalinity – due to higher concentrations of nutrients and ions
Alkalinity in streams - influenced by rocks and soils, salts, certain plant activities, and certain industrial wastewater discharges
Measured in mg/l or ppm
Typical Alkalinity ranges
Sample Value, mg/L CaCO3
Rain Water <10
Typical Surface Water 20-200
Surface water in regions with alkaline soils
100-500
Ground water 50-1000
Sea water 100-500
Total Alkalinity Testing • Important compounds that determine alkalinity – Carbonate and Bicarbonate ions
• Types of Alkalinity: o Phenolphthalein Alkalinity: called as Bicarbonate alkalinity
and present for solutions above pH 8.3.
Phenolphthalein indicator color changes from pink to colorless with the addition of acid
Many water samples have little or no phenolphthalein alkalinity
o Total alkalinity - the final endpoint for alkalinity titration. At pH 4.5 all carbonate and bicarbonate ions are converted to carbonic acid
Continuation----- Double endpoint titration using a pH meter (or pH "pocket pal")
and a digital titrator or buret is generally used. Titration method uses the addition of small, precise quantities of
sulfuric acid (the reagent) to the sample until the sample reaches a certain pH (known as an endpoint). The amount of acid used corresponds to the total alkalinity of the sample.
Sulfuric acid converts the three main forms of alkalinity (bicarbonate, carbonate, and hydroxide) to carbonic acid in these reactions.
This method is tedious and not user friendly for field sample analysis
Total Alkalinity – Reagent strips
• Our current reagent strip detects Total Alkalinity from 1 to 320 ppm
• We developed chemistry using
various pH sensitive dyes and acids to extend the above Total Alkalinity range.
Total Alkalinity Reagent Test Overview
• New formulation has increased the Total Alkalinity range from 1-320 to 1-800 ppm
• The limit of detection is (3SD) is 8.58 ppm
• Accuracy of the method is ± 6%
• No Interferences
• Performance of the strips were validated for drinking, pool, coolant, boiler and sea water
Total Alkalinity – Spectras
Reaction of Alizarin red S with various concentrations of Total Alkalinity
0
0.2
0.4
0.6
0.8
1
400 450 500 550 600 650 700
Total Alkalinity, ppm
Abs
orba
nce 0 ppm
50 ppm100 ppm200 ppm300 ppm400 ppm500 ppm600 ppm700 ppm800 ppm
Calibration plot - Alizarin red S with various concentrations of Total Alkalinity
y = 0.0008x + 0.0424R2 = 0.9833
00.10.20.30.40.50.60.70.8
0 100 200 300 400 500 600 700 800Total Alkalinity, ppm
Abso
rban
ce
Phosphate
• Phosphorus present 0.12% in the earth’s crust"• Human bones and teeth contain calcium phosphate"• Muscle, nerves and brains of animals contain complex organic
compounds of phosphorus"• Red phosphorus is used to manufacture of safety matches and
fertilizers"• Majority of phosphate water contamination problems occur in the
pool and in the ground"
Phosphate - Water
• Lawn runoff "• Rain water "• Leaves and
debris (soil and rock)"• Swimming pool bathers
(sweat and urine)"• Pool treatment chemicals"
Algae and Phosphate
• If algae is observed phosphate is present
• Chlorine levels control algae growth
• Sewage (waste) water contains high levels of algae if not treated properly
Phosphate Testing Laboratory Instruments: Spectroscopic, Chromatographic, etc
• Costly to operate
• Not user friendly
• Time consuming
• Increased sample prep time
• Most approved by various Governments
Phosphate Testing Portable Instruments: Hand Held Photometers
• Cost effective
• User friendly
• Fast results
• Used in field and real time monitoring
• Most approved by various Governments
• New formulation has increased the Phosphate range from 0-4 ppm to 0-6 ppm
• The limit of detection is (3SD) is 0.18 ppm • No interferences • Accuracy ± 3% • Performance of the strips were validated for drinking,
pool, coolant, boiler and sea water
Phosphate Reagent Test Overview
Phosphate – Spectras
Reaction of Molybdenum with various concentrations of Phosphate
00.10.20.30.40.50.60.70.8
425 450 475 500 525 550 575 600 625 650 675 700 725 750 775 800Phosphate, ppm
Abs
orba
nce
0 ppm0-5 ppm1 ppm2 ppm3 ppm4 ppm5 ppm6 ppm
Calibration plot - Phosphate with Molybdenum
y = 0.1131x + 0.0832R2 = 0.9768
00.10.20.30.40.50.60.70.80.9
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5Concentration of Phosphate, ppm
Abs
orba
nce
Photometric Test Method
Rinse sample cell three times with water to be tested and fill cell to capacity
Press ZERO to blank meter.
Press READ to start the count down timer and dip an eXact® Strip Micro PO4 Phosphate for 20
seconds then remove and discard strip.
The meter automatically starts the count up timing for 120 seconds and reads the
sample for Phosphate
Testing cap is not necessary for accurate readings, the meter design overcomes ambient light interference.
eXact® Micro Photometers Benefits • Safe to use with no glass, powders or tablets to break • Lab quality results at 0.01 ppm (mg/L) precision • Affordable and uses safe chemistry • Quick Non-Technical Procedure • Accurate results with fewer steps than competitive kits
eXact® Micro Photometers Benefits
• Uses patented reagent delivery system
• Reagent strip provides smooth and precise sample dispersion
• No suspended solids are left in the sample vial to adversely
affect results especially in cold water
• We developed reagent strips for the detection of High Range Total Alkalinity and Phosphate
• We applied the strip technology and testing method for our eXact Micro photometers
• The reproducibility, precision and accuracy were very good • Applied to various water samples • We have also developed High Range Total Hardness and
Magnesium Hardness strips
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Thank you for your attention!