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Abstract
High performance liquid chromatography (HPLC) stationary phases of gamma cyclodextrin, ion exchange ethylvinylbenzene/divinylbenzene (EVB/DVB) copolymer and poly (Styrene-divinylbenzene) (PRP-1) copolymer were investigated for the separation of beta lactam antibiotic epimers of cephalexin, moxalactam, ticarcillin, and carbenicillin. A combination of ion pair chromatography and inclusion complex formation improved the selectivity of moxalactam epimers on gamma cyclodextrin but had no effect on cephalexin epimers. A 10% increase in resolution was obtained for the moxalactam epimers on gamma cyclodextrin when 3mM tetrapropylammonium bromide was present in the mobile phase. Ion-exchange and reverse phase properties of the ion-exchange EVB/DVB phase coupled with perchlorate or sodium pentane sulfonate ion pair chromatography were also successful in separating some of the epimers. Retention and separation behavior of the analytes could not be easily predicted using this multiphase system. The PRP-1 phase was capable of easily resolving the epimers studied with minor adjustments in the mobile phase pH and organic modifier concentration. The PRP-1 phase would be highly recommended for the separation of antibiotic epimers based on the model compounds studied.