Separation of some cephalosporin derivatives by ion-pair reversed-phase high-performance liquid chromatography

Cephapirin, its major metabolite desacetylcephapirin, 7-aminocephalosporanic acid and some other cephalosporin derivatives are separated on a chemically bonded octadecylsilane reversed-phase column. The selectivity between cephapirin and desacetylcephapirin on the reversed-phase column is too high, resulting in a poor separation. The effect of several variations of the chromatographic conditions on the selectivity has been examined. The in situ ion-pair formation of the cephalosporins with several counter ions and the influence of the ion-pair formation on the capacity factor and on the selectivity have been investigated. Other factors, such as the temperature, combination of counter ions and nature of the organic modifier and their influence on the selectivity have also been studied.