Spectrophotometric determination of 1-naphthylamine in urine with pentacyanonitrosylmanganate (II)

Abstract

A new Spectrophotometric method is proposed for the determination of 1-naphthylamine (R), based on its reaction with Mn(CN)₅NO²⁻ to form Mn(CN)₅NH₂R³⁻ and measurement of the absorbance at 472 nm. In aqueous medium the molar absorptivity of the manganese complex is maximum (ɛ = 8.0 × 10³1 · mole⁻¹ ·cm⁻¹) in the pH range 5.0–10.0, the colour develops more rapidly at pH 10.0. The absorptivity is increased by a factor of 3.5 if the complex is extracted as an ion-associate into chloroform. The extraction efficiency is 99.2% for a single-step extraction, and a concentration factor of 5 can also be achieved. Linearity of response extends over the range 0.04–1.4 gmg/ml 1-naphthylamine, the coefficient of variation being 1.4% at the 0.29 μg/ml level (n = 6). The detection and determination limits are 0.005 and 0.018 μg/ml, respectively. The method is selective enough to allow the determination of 1-naphthylamine in the presence of considerable amounts of other amines, such as aminophenols and phenylenediamines. Results obtained in the determination of 1-naphthylamine in human urine were very satisfactory.