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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