Study on the Spectral Characteristic of the Diazotization-Coupling with Sulfanilic Acid and Its Analytical Application

Nitrite was diazotized with sulfanilic acid and followed by coupling with N-(1-naphthyl) ethylenedia mine dihydrochloride to produce a red azo-compound in dilute hydrochloric acid medium. The azo-compound has a maximum absorption at 500 nm in alkaline medium and the apparent molar absorptivity is 2.6×10~4 L·mol~(-1)·cm~(-1). Based on the spectral characteristic of the azo-compound in various medium, a new method for the determination of trace amounts of nitrite was developed in alkaline medium. The Beer's law is obeyed for nitrite in the range of 0 to 2.8 mg/L and the detection limit is 2.6 μg/L. The method has good selectivity and has been applied to the determination of nitrite in environmental water, vegetable samples, sausage and synthetic samples with satisfactory results and the recovery for nitrite is 94.0%-105.0%.