Fast Spectrophotometric Method for Determination of Nitrate and Nitrite Using Diphenylamine-4-sulfonic Acid

A new method for determination of nitrates was developed. It was based on reduction of nitrates to nitrites using 0.1 % diphenylamine-4-sulfonic acid solution in 95% (m/m) H 2 SO 4 . Nitrites obtained in this reaction were diazotized using sulfanilic acid and then coupled to N-( 1-naphtyl)-ethylenediamine to form a coloured azo complex, which was determined spectrophotometrically at the wavelength of 550 nm. Calibration plot was linear in nitrate concentration range 1―20 μg mL ―1 N with R 2 = 0.99.