Spectrophotometric determination of nitrite using new coupling agents

Abstract

A method is described for the spectrophotometric determination of nitrite. It is based on the reaction of nitrite with p-nitroaniline (PNA) in acid medium to form diazonium ion, which is coupled with frusemide (FRU) or 5-methyl-4-{[(1E)-phenylmethylene]amino}-2,4-dihydro-3H-1,2,4-triazole-3-thione (MPAT) in basic medium to form azo dyes, showing absorption maxima at 680 or 395 nm respectively. The range of linearity for PNA-MPAT and PNA-FRU system are 0.4-2.0 μg/mL, 0.02-0.6 μg/mL of nitrite respectively. Molar absorptivity, Sandell sensitivity, Detection limit, Quantitation limit for PNA-MPAT and PNA-FRU system were found to be 3.314 × 10³ Lmol⁻¹cm⁻¹, 0.014 μg cm⁻², 0.559 μg mL⁻¹, 1.695 μg mL-1and 1.46 × 10³ Lmol⁻¹cm⁻¹, 0.032 μg cm⁻², 0.485 μg mL⁻¹, 1.470 μg mL⁻¹ respectively. The method has been applied to various water samples, soil samples and tablets.