On-line sample concentration in micellar electrokinetic chromatography using cationic surfactants

Two on-line sample concentration techniques, sample stacking and sweeping, were evaluated using cationic surfactants as pseudostationary phases in mic ellar electrokinetic chromatography. As. cationic surfactant micelles, tetr adecyltrimethyl-ammonium bromide and cetyltrimethylammonium chloride were e mployed. About 10-fold and 1000-fold increases in detection sensitivity in terms of peak heights were observed by sample stacking and sweeping, respec tively, without suppression of the electroosmotic flow. In particular, the concentration limits of detection (S/N=3) for test naphthalene-sulfonic aci ds obtained with sweeping were from 0.96 to 0.47 ppb with UV detection with out any preconcentration procedure. (C) 2001 Elsevier Science B.V. All righ ts reserved.