Analysis of linear alkylbenzenesulfonates by capillary zone electrophoresis with large-volume sample stacking

A systematic investigation of optimal conditions for determining the homolo gues of linear alkylbenzenesulfonates (LAS) by capillary zone electrophores is (CZE) using the large-volume sample stacking technique was presented. Th e most effective sample stacking and separation conditions was 20 mM borate buffer with 30% acetonitrile at pH 9.0, and the sample hydrodynamic inject ion of up to 90 s at 4 p.s.i. (1 p.s.i.= 6892.86 Pa) (around 711 nl). Under such conditions, approximately a 100-fold enrichment factor was achieved b ased on peak heights. The reproducibility of migration time and quantitativ e results of stacking CZE can be improved by using internal standards. Quan titation limits of the homologues of LAS were 0.002-0.01 mg/l under these e nrichment conditions. The analysis of real samples of laundry and dishwashi ng detergents was performed. The established high-performance liquid chroma tography method was applied to evaluate the stacking CZE method, and compat ible results were obtained. (C) 2001 Elsevier Science BY All rights reserve d.