Simultaneous determination of cationic and nonionic surfactants in consumer products by use of mixed aggregate-based methodology

Mixed aggregate-based methodology was used for the simultaneous resolution of differently charged surfactants in binary mixtures. The new approach rel ies on the sequential formation of two types of surfactant aggregates in an aqueous medium, premicelles and micelles, and on measurement, in a single run, of two parameters related to the formation they provide. Premicelles c an be easily induced for ionic surfactants in the presence of oppositely ch arged dyes. In this work, the simultaneous resolution of cationic dialkyldi methylammonium (DDAS) and nonionic alkoxylated (NAS) surfactants in binary mixtures was undertaken. The anionic surfactant sodium dodecyl sulfate (SDS ) was used as titrant and the anionic dye Coomassie Brilliant Blue G (CBBG) to induce DDAS premicellar aggregates. Measurement of the total amount of CBBG-DDAS-SDS premicellar aggregates and the critical micelle concentration (c.m.c.) of DDAS-NAS-SDS micelles permitted us to determine the total conc entration of DDAS and NAS at the ng ml(-1) level in a single run with relat ive errors of less than 5% in most instances. The simultaneous determinatio n of cationic and nonionic surfactants in commercially available softeners was accomplished without the need for sample treatment. The results obtaine d indicate that this methodology possesses a high potential for quality con trol of surfactant formulated products.