Sample concentration by sample stacking and sweeping using a microemulsionand a single-isomer sulfated beta-cyclodextrin as pseudostationary phases in electrokinetic chromatography

Two of the powerful on-line sample concentration techniques, sample stackin g and sweeping under pH-suppressed electroosmotic how, have been evaluated using a microemulsion and a single-isomer sulfated beta-cyclodextrin deriva tive in electrokinetic chromatography. Several clinically relevant steroids have been separated acid concentrated using a microemulsion consisting of 100 mM sodium dodecyl sulfate, 41 mM n-heptane and 700 mM 1-butanol in 50 m M phosphoric acid (pH 1.9). Three environmentally relevant phenoxy acid her bicides and their enantiomers have been separated and concentrated using a background electrolyte consisting of 20 mM hepta-6-sulfato-beta-cyclodextri n in 15 mM phosphoric acid (pH 1.9), Significant detector response improvem ents have been achieved and utilized for analysis of a relatively clean mat rix, lake water. (C) 1999 Elsevier Science B.V. All rights reserved.