Determination of Total Nitrogen in River Water Based on Diazotization Coupling Reaction in the Presence of Vanadium Chloride after Oxidative Pretreatment with Peroxodisulfate

Abstract

A convenient method was proposed for the spectrophotometric determination of total nitrogen in sewage and river-water samples. Each water sample was taken into glass bottles with screw caps and then heated at 120°C for 30 min after the addition of potassium peroxodisulfate, by which nitrogen-containing compounds were quantitatively oxidized into nitrate. The determination of the resulting nitrate was performed by measuring the absorbance at 540 nm after a diazotization coupling reaction of N -naphthylethylenediamine and sulfanylamide in the presence of nitrite generated from the reduction of nitrate with vanadium chloride. The proposed method could be applied to the determination of total nitrogen in sewage and river-water samples. Analytical data obtained by the proposed method were highly correlated to those determined by the UV method (JIS method). The sensitivity of the proposed method is superior to those of spectrophotometric methods reported so far.