Determination of nitrite in meat products and water using dapsone with combined spot test/diffuse reflectance on filter paper

This paper describes a simple, portable and environmentally friendly procedure for the determination of nitrite by combined spot test/diffuse reflectance spectroscopy on filter-paper. The method is based on the diazotization reaction of dapsone (4,4′-diamino-diphenyl sulphone, DAP) and (naphthyl)ethylenediamine hydrochloride (NED) with nitrite in acidic medium, yielding a coloured compound on the surface of a filter paper. Experimental design methodologies were used to optimise the measurement conditions. The reflectometric measurements were carried out at 545 nm and the linear range obtained was 0.29–5.0 mg L−1 of nitrite (R = 0.997), with detection and quantification limits of 0.09 and 0.29 mg L−1, respectively. The proposed method was applied successfully to the analysis of nitrite in meat products and well water samples.