On-line coupling of partial filling-capillary zone electrophoresis with mass spectrometry for the separation of clenbuterol enantiomers

The on-line coupling of capillary zone electrophoresis with mass spectromet ry (CZE-MS) for the separation of enantiomers is hampered by the presence o f nonvolatile chiral selectors such as cyclodextrins in the separation buff er. This problem can be overcome by use of the partial filling technique wh ere only a part of the capillary is filled with the separation buffer conta ining chiral selectors. Since the electroosmotic flow is almost completely suppressed at acidic pH, that dimethyl-beta -cyclodextrin is neutral, no fr ee cyclodextrin would reach the MS detector when using a partially filled c apillary. By this method, clenbuterol enantiomers were successfully resolve d and separated from salbutamol (internal standard) in aqueous solution and in plasma samples. A solid-phase extraction (SPE) was used for the prepara tion of plasma samples before analysis.