CE Resolution of Neutral and Anionic Racemates with Glycopeptide Antibiotics and Micelles

Abstract

The glycopeptide antibiotics vancomycin, ristocetin A and teicoplanin have been shown to be effective chiral selectors in capillary electrophoresis (CE). However, most of the resolved enantiomers were anionic or acidic compounds that contained carboxylic acid, phosphate, or sulfonate groups. Conversely, a large number of neutral racemates are resolved using these same chiral selectors attached to the stationary phase in HPLC. The problem in resolving neutral analytes in CE is outlined and discussed. Addition of sodium dodecyl sulfate (SDS) micelles to the run buffer greatly increases the available elution window, thereby facilitating the separation of neutral racemates. Neutral analytes resolved in this CE system include bromacil, bendroflumethiazide and 5-(4-hydroxyphenyl)-5-phenylhydantion. The separations of coumachlor and warfarin are also demonstrated. In addition, the effect of surfactant concentration and organic cosolvents on elution time and enantioresolution are discussed.