Determination of linear alkylbenzenesulfonates in industrial and environmental samples by capillary electrophoresis

Abstract

Linear alkylbenzenesulfonates (LAS) are applied extensively as surfactants in consumer formulations, e.g., laundry detergents, as complex mixtures of homologues and isomers. For product control and environmental analysis it is important to know the total content of LAS in addition to the homologous and isomeric distribution. Capillary electrophoresis (CE) was used for the determination of the sum, homologues and isomers of LAS in household products and waste-water samples. A technical LAS mixture was used for method development. In buffers without organic solvent, all homologues and isomers produce only one peak; these conditions were applied to the analysis of waste water after preconcentration. A recovery of 101.8%, a limit of detection of 1 mg l^–1 and a reproducibility of 3.5% (RSD) were achieved. The determination of homologous distribution was carried out by adding acetonitrile to a borate or phosphate buffer. An application of this method is the analysis of sewage sludge for LAS after methanolic extraction, with an average recovery of 75.5% and a limit of detection of 4 mg l^–1. Isomeric separation was achieved using electrolytes with high contents of sodium dodecyl sulfate (SDS) and acetonitrile as organic modifier. The identification of components in household products was possible by the standard additions method.