INTERLABORATORY STUDY OF ANALYSIS OF PHENOXYMETHYLPENICILLIN BY LIQUID-CHROMATOGRAPHY

A liquid chromatography method for analysis of phenoxymethylpenicillin has been examined in a collaborative study involving 6 laboratories. The method comprised an isocratic part, which is used in the assay, Wh en the isocratic part is combined with gradient elution, the method is suitable for purity control. Five samples of phenoxymethylpenicillin (potassium salts and acid) were analysed. The main component, the most important side product 4-hydroxyphenoxymethylpenicillin and other imp urities were determined. An analysis of variance proved the absence of consistent laboratory bias. Laboratory-sample interaction was not sig nificant. Estimates of the repeatability and reproducibility of the me thod, expressed as standard deviations (SD) of the result of the deter mination of phenoxymethylpenicillin, were 0.50 and 0.63 respectively.