Separation of alkylbenzyl quaternary ammonium compounds by capillary zone electrophoresis with sample stacking injection

A systematic investigation of operational buffer systems, sample preparatio n and instrument parameters for achieving the best possible performance for determining an homologous series of N-benzyl-N-alkyl-N,N-dimethylammonium chloride compounds by capillary zone electrophoresis with direct UV detecti on. The most effective separation was achieved within 3.5 min with the addi tion of acetonitrile (40%) in a phosphate buffer (20 mM pH 5.2) using a 40 cm fused-silica capillary operating at 25 KV and 20 degrees C. Degassing of all electrolyte solutions and samples was very important. The linearity an d repeatability for each compound were satisfactory. To improve detection l imits, on-column sample preconcentration, sample stacking, was investigated achieving a tenfold enrichment factor and quantitation limits about 10(-7) M.