Abstract

A simple spectrophotometric method for the quantification of nitrite/nitrate has been proposed based on diazo coupling reaction
using novel amine, that is, 5-(4-aminophenyl)-1,3,4-oxadiazole-2-thiolandN-(1-Naphthyl) ethylenediamine as a coupling agent
under acidic condition. The azo dye formed in this diazo-coupling reaction has been characterized by Fourier Transform Infrared
study. The proposed method has exhibited wide linearity in the concentration range 0–200 ppm with a limit of detection 0.05
ppm. The utility of the proposed method has been successfully applied to measure trace level nitrite/nitrate in organic and non-
organic farmed vegetables such as spinach, cabbage, beetroot, carrot, and cucumber. The nitrite/nitrate levels in organic farmed
vegetables are lower in comparison with non-organic farmed vegetables. The nitrate levels were monitored after its reduction
to nitrite using copperized-cadmium reductor column under optimized conditions. The results obtained by the proposed method
are in good agreement with the results of the standard protocol.