Spectrophotometric determination of cationic surfactants in frozen and fresh squid by ion-pair formation with Methyl Orange

Abstract

A spectrophotometric method for the determination of cationic surfactants, such as hexadecylpyridinium chloride, cetyltrimethylammonium bromide, tetrabutylammonium nitrate and hyamine 1622, is proposed, which is based on their extraction into chloroform as ion pairs with Methyl Orange. The method is simple, rapid and sensitive, giving a molar absorptivity of 2.7 × 104 l mol–1 cm–1 and a limit of determination of 1.0 p.p.m. In determinations of total cationic surfactant content in samples of frozen and fresh squid, an average molecular mass of 400 was assumed, which is close to the mean molecular mass of the surfactants determined.