Nitrate testing in water giving below three methods.
Sources of impurities in water
• Fertilizers and manures
• Decayed vegetable and
• Animal feedlots
• Municipal wastewater and sludge disposal to lands
• For Industrial discharges
• Leachates from refuse dumps
• Septic systems
• N-fixation from the atmosphere by bacteria and lightning.
Determination of nitrate in water by the ultraviolet spectrophotometry.
• Useful for uncontaminated natural waters and potable water supplies that have low organic contents
• Follows the Beer’s law up to 11 mg/L as N
• Interferences
Dissolved Organic Matter
Surfactants
Nitrite and Hexavalent Chromium
Procedure
Filter the sample
Add 1 ml of 1N HCl per 50 ml of sample
Read absorbance or transmittance at 220 nm and 275 nm
Set 0 absorbance or 100% transmittance with distilled water
Determination of nitrate in water by Electrode Method
• Useful for a Nitrate concentration range of 0.14 to 1400 mg/L NO3-N
• Interferences
Chloride and bicarbonate with weight ratios to NO3-N >10 or >5 respectively
NO2, CN, Sulphide, Br, I, Chlorite, and Chlorate
Phenoldisulphonic Acid (PDA) Method
• Nitrate reacts with Phenoldisulphonic acid to produce nitro derivatives that in alkaline solution rearranges its structure to form a yellow-colored compound with characteristics that follows
• Chloride interferes seriously which can be overcome by precipitation of chloride with Ag+ as AgCl
Determination of chloride in water by titration
Methodology: Argentometric Method
Principle
Chloride determined in a natural or slightly alkaline solution by titration with standard silver nitrate, using potassium chromate as an indicator. Silver chloride are quantitatively precipitated before red silver chromate is formed.
Chloride mg/L = (A-B) x N x 35.45 x 1000/ml sample
Where A = ml AgNO3 is required for sample
B = ml AgNO3 required for blank
N = Normality of AgNO3 used
Standard analytical procedure for water analysis