Study of organic interferences in the spectrophotometric determination of nitrite using composite diazotisation-coupling reagents

Abstract

A study was made of organic interferences in the spectrophotometric determination of nitrite by the diazotisation-coupling technique using three composite reagents [sulphanilamide and N-(1-naphthyl)ethylenediamine (NED); sulphanilic acid and NED; and 4-nitroaniline and NED]. Many organic substances interfere, usually causing low results. The interference is usually less with the 4-nitroaniline-NED and sulphanilamide-NED methods than with the sulphanilic acid-NED method. The interferents tested included aliphatic amines (primary, secondary and tertiary), aromatic amines (primary, secondary and tertiary), various phenolic compounds and miscellaneous organic compounds (sucrose, dextrose, lactic acid, succinic acid, acetamide, acetanilide, ethylenediamine tetraacetate, cholesterol, rennin, dodecyl sodium sulphate, acetophenone, urea, citric acid, caffeine, saccharin, morpholine, L-asparagine, gelatin, benzoic acid, formaldehyde, cinchonine, nicotinic acid, trypsin, creatine, starch, albumin, gum tragacanth, casein, formic acid, sorbic acid, ascorbic acid and acetaldehyde). The effect of detergents and soap was also examined. Large amounts of water-miscible solvents (methanol, ethanol, acetone and glycerin) can be tolerated. Water-immiscible solvents do not affect the colour.