Determination of nitrite ion using the reaction with 4-aminobenzotrifluoride and 1-naphthol

Abstract

A rapid, sensitive and selective method for the determination of nitrite ion is described. It depends on the reaction of the intended ion with 4-aminobenzotrifluoride in acidic medium to form a diazonium ion, which couples with 1-naphthol in alkaline media to give a pinkish red azo dye that shows maximum absorption at 510 nm. Beer's law is obeyed over the concentration range 0.03–0.8 p.p.m. of nitrite with a molar absorptivity of 3.91 × 10⁴ l mol^–1 cm^–1. The sensitivity of the method (expressed as the amount of nitrite corresponding to an absorbance of 0.001 at 510 nm in a 1-cm cell) is 0.0012 µg cm^–2. The optimum reaction conditions for diazotisation and full colour development, the effects of variables and the effects of common interfering ions have been studied.