E. Borrego et al., Simultaneous determination of cationic and nonionic surfactants in consumer products by use of mixed aggregate-based methodology, ANALYST, 125(8), 2000, pp. 1507-1512
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.