Abstract

In order to control the pollution by nitrite, a direct spectrophotometric flow injection method for the determination of nitrite in tannery effluents has been developed. The method is based on the diazotized intramolecular coupling of a 4-Amino-5-hydroxynaphthalene-2,7-disulfonic acid monosodium salt hydrate (AHNDMS) by the addition of nitrite in a phosphate buffer solution of pH7.5 and the increase in absorbance of the purple complex is monitored at 550nm. Chemical factors and FIA variables affecting the system are also discussed. Under the optimal conditions, the linear range of this method was 20-1500μg l-1; the detection limit was 0.15μg l-1; the relative standard deviation was 0.67% (n=11, 450μg l-1). This method was suitable for automatic and continuous analysis, and successfully applied to determine the content of nitrite in tannery effluent.