EVALUATION OF LC METHODS FOR THE SEPARATION OF PHENOXYMETHYLPENICILLIN AND ITS RELATED SUBSTANCES

Five isocratic reversed-phase liquid chromatography (LC) methods have been examined for the separation of phenoxymethylpenicillin and its re lated substances. A method previously selected for the analysis of ben zylpenicillin gave the best selectivity. The mobile phase of this meth od is composed of 0.5 M phosphate buffer (pH 3.5)-water-methanol (10:5 0:40), the amount of organic modifier was slightly adapted when it was used with different columns. Similar selectivity is obtained not only on different C18 materials but also on C8 packings. The selectivity o n poly(styrenedivinylbenzene) is less good. As method performance test a resolution test with benzylpenicillin was used. The robustness of t his method was examined by applying a full factorial design to test th e influence of the content of organic modifier in the mobile phase, th e pH of the mobile phase, the concentration of buffer in the mobile ph ase and the temperature of the column. The results show that the metho d is robust. (C) 1998 Elsevier Science B.V.