EVALUATION OF LIQUID-CHROMATOGRAPHY METHODS FOR THE SEPARATION OF AMPICILLIN AND ITS RELATED SUBSTANCES

Two laboratories collaborated to examine the selectivity of four isocr atic liquid chromatography (LC) methods for the separation of ampicill in and its related substances. The United States Pharmacopeia (USP) as say method gave the best selectivity. Similar selectivity was obtained on C18 columns as well as on C8 and poly(styrene-divinylbenzene) copo lymer columns. A resolution test using cefradine was proposed to repla ce the test with caffeine prescribed by the USP. Based on the USP meth od, a gradient LC method was developed for the analysis of related sub stances in ampicillin. This LC method has been proposed for assay and purity control in the ampicillin monographs of the European Pharmacope ia.