title: Determination of dialkyldimethylammonium surfactants in sewage based on the formation of premicellar aggregates.
abstract: A method is described for the determination of dialkyldimethylammonium surfactants (DDAS) in sewage, based on the formation of premicellar aggregates with sodium dodecyl sulfate and using the dye Coomassie Brilliant Blue G (CBBG) as a photometric probe. The mixed aggregates are selectively obtained at DDAS concentrations three orders of magnitude below the critical micelle concentration. As a result, DDAS can be determined at the microg l(-1) level without interference from other quaternary ammonium/pyridinium or anionic/non-ionic surfactants. Because of the selectivity of the method, the clean-up of sewage influents and effluents only involves extraction with chloroform, after formation of the DDAS-sodium dodecane sulfonic acid ion pair, evaporation of the extracts to dryness and dissolution of DDAS in 4 M hydrochloric acid. The recovery of DDAS ranged from 82 to 93% and from 100 to 105% in sewage influents and effluents, respectively.
authors.affiliation: Department of Analytical Chemistry, Facultad de Ciencias, Córdoba, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Merino
authors.forename: S
authors.initials: S
authors.lastname: Rubio
authors.forename: D
authors.initials: D
authors.lastname: Pérez-Bendito