Adjust pH of water sample to 6.7 using Acetic acid solution.

Pipette 10 ml of samples into Test tubes.

One tube should contain only distilled water. This will be the control.

Place tubes in cold water bath.

Add Sulfuric acid solution into the tube. Wait until tubes are cool again.

Add small amount of Brucine reagent to all tubes except the control.

Place all samples and control in boiling water bath. Allow them to boil for about 25 minutes.

Transfer all tubes to cold water bath. Allow them to cool to 20-25 deg C.

Read absorbances of samples and blank on a Spectrophotometer at 410 nm wavelength using 1 cm cuvette.

Read also the absorbances of atleast 3 the standard solutions.

Prepare calibration curve from absorbance readings of standard solutions against their corresponding concentrations.

Calculate the Nitrate content using Linear regression.

Standard Solutions :

Prepare Nitrate Standard Solutions by dissolving Potassium Nitrate in distilled water. Make several dilution to be able to prepare desired concentrations.

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EN 71 Part 3 ( Testing Procedure )
IEC 62321 – Hexavalent Chromium Testing Method & Procedure
US EPA 3060A – Hexavalent Chromium Testing Method & Procedure
ASTM F963 -96a / ASTM F963 -07 (Testing Procedure)