Speciation Study of Nitrite/Nitrate through Diazo-Coupling Reaction Using Silica-Perchloric\nAcid as a Novel Catalyst at Trace Level: Application to Environmental Samples

Abstract

A simple, sensitive and rapid spectrophotometric method has been developed based on the diazo\ncoupling reaction in the quantification of nitrite/nitrate at trace level using silica perchloric acid (SPCA)\nas an acid catalyst. 5-Amino-2-mercapto benzimidazole has been used as a novel amine and coupled\nwith N-(1-naphthyl)ethylenediamine dihydrochloride (NEDA) to produce an intense coloured azo\ndye. The proposed method showed wide linearity in the concentration range 0.1-1000 ppm of nitrite.\nThe molar absorptivity and Sandell′s sensitivity were found to be 1.6 × 106 L mol–1 cm–1 and 0.0012 μg\ncm–2 respectively. Nitrate was measured after its reduction to nitrite using optimized copper-cadmium\nreductor column. The proposed method has been successfully applied to measure trace level\nnitrite/nitrate from a variety of sample matrices like water, soil, milk and radiator coolant.