Determination of soap in anionic surfactant mixtures and amine and quaternary ammonium salts in cationic surfactant mixtures by using an automated photometric titrator (Automatic photometric titration of surfactants based on two-phase titration; IV)

Abstract

The determination of soap in anionic surfactant mixtures and amine and quaternary ammonium salts in cationic surfactant mixtures was carried out by using an automated photometric titrator equipped with porous PTFE (Teflon) membrane separator (previous publications) based on two-phasetitration. In the case of soap in anionic surfactant mixtures, it is necessary to determine surfactant mixtures under both acidic and alkaline conditions, and the difference between the two determinations indicates the content of soap. However, the analytical values of some anionic surfactants(sodium alkanesulfonate and α-olefinesulfonate) under acidic and alkaline conditions by the previously proposed method were found not to be identical. The difference was considered to be caused bythe presence of polysulfonate. Therefore, 7% of 1-hexanol was added to chloroform to improve the recovery of polysulfonate. Under these conditions, the determination of soap in anionic surfactant mixtures was successfully carried out. Furthermore, sulfate-type anionic surfactants in anionic surfactant mixtures were determined by the acid hydrolysis method. By the same way as anionic surfactants, the determination of cationic surfactant mixtures (amine and quaternary ammonium salts) could be also effected by using Disulphine Blue as an indicator, which could be used under both acidic and alkaline conditions. © 1988, The Japan Society for Analytical Chemistry. All rights reserved.