Determination of Trace Nitrite by Spectrophotometry Based on the Coupled Reaction with Resorcinol

A new spectrophotometric method for the determination of trace amounts of nitrite was developed. In acidic solution, nitrite was first diazotized with sulfanilic acid, followed by coupling with resorcinol to produce an azo - compound in NH3 - NH4Cl buffer and the azo - compound has a maximum absorption at 430nm, the Beer' s law of which is obeyed for nitrite in the range of 0 to 2.0 mg/L. The apparent molar absorptivity is 3.6×104 L. mol-1 .cm-1. The method has good selectivity and has been applied to the determination of trace amounts of nitrite in environmental water and vegetable samples with satisfactory results.