Abstract
Nitrate is reduced to nitrite in the persence of NH4Cl with zinc powder at pH 3 with a recovery of 80%, and the nitrite produced is determined spectrophotometrically with GR reagent. To 25 ml of sample is added 0.3 g of NH4Cl, and pH is adjusted to 3.3 with a KCl-HCl buffer. With the addition of 0.2 g of zinc powder, the solution is kept at 020°C for 10 min. with occasional swirling. The solution is filtered and about 60 mg of GR reagent is added to an aliquot of the filtrate. The total-N(NO2+NO3) is determined by its absorbance, and nitrate-N is given by the difference between the total-N(NO2+NO3) and nitrite-N which is determined separately. The conditions in the procedure and the presence of salts are not critical.
