Application of promethazine hydrochloride as a chromogenic reagent for the spectrophotometric determination of aniline and its substituents

Abstract

The oxidative coupling reaction of promethazine · HCl with primary aromatic amines was applied to the determination of aniline and four of its substituents. A mixture of an acidic solution (3.5% acetic acid or acetate buffer of pH 4.8) of the aromatic amine and the chromogenic reagent was treated with hypochlorite ion. The wavelengths of maximum absorption are at 590 nm for aniline, p-aminobenzoic acid, sulfanilic acid, and p-aminoacetophenone and at 520 nm for p-nitroaniline and the molar absorptivities range from 1.00 × 104 to 1.86 × 104 liter mol-1 cm-1. A linear correlation was found between absorbance at λmax and concentrations. The results obtained are both precise (RSD was better than 2.1%) and accurate (relative percentage error was better than ±2.5%). © 1990.