Simple Spectrophotometric Determination of Long-Chain Quaternary Ammonium Salts with o -Hydroxy-hydroquinonephthalein and Manganese(II)

Abstract

A simple spectrophotometric method, without solvent extraction, has been established for the determination of long-chain quaternary ammonium salts by ternary complex formation with o-hydroxyhydroquinonephthalein and manganese(II). The absorption maxima of the ternary complexes lay at about 575nm against water in borax media. In the case of hexadecylpyridinium chloride(HPC), Beer′s law held from 10 to 120μg/10ml, the apparent molar absorptivity and the coefficient of variation being 3.8×104l mol-1 cm-1 and 0.59% (n=10) for 51μg of HPC.In the determination of HPC, the coexistence of short-chain amines, such as triethanolamine and tetramethylammonium, and several basic drugs, such as thiamine and pyridoxine, interfered very little. This method was applied to the determination of long-chain quaternary ammonium salts in gargle and hair-rinse.