Simultaneous stereoselective analysis of tramadol and its main phase I metabolites by on-line capillary zone electrophoresis-electrospray ionization mass spectrometry

On-line combination of partial filling capillary electrophoresis and electr ospray ionization mass spectrometry was demonstrated for the simultaneous e nantioseparation of tramadol and its main phase I metabolites. The partial filling technique was efficient at avoiding MS contamination by the chiral selector. Different experimental factors were investigated, including the c hiral selector nature and concentration, plug length as well as the separat ion temperature. The best enantioseparation of the investigated compounds w as achieved with a coated polyvinyl alcohol capillary and a 40 mM ammonium acetate buffer, pH 4.0, adding sulfobutyl ether beta-cyclodextrin (2.5 mg/m l) as the chiral selector. The charged cyclodextrin not only allowed enanti oseparation of tramadol and its metabolites, but also improved the selectiv ity of compounds with the same molecular mass. Finally, CE-electrospray ion isation-MS was successfully applied to the stereoselective analysis of tram adol and its main metabolites in plasma after a simple liquid-liquid extrac tion. (C) 2000 Elsevier Science B.V. All rights reserved.