INTERLABORATORY STUDY OF THE ANALYSIS OF AMOXICILLIN BY LIQUID-CHROMATOGRAPHY

A liquid chromatography method for analysis of amoxicillin was examine d in a collaborative study involving 11 laboratories. The method compr ised an isocratic part, which is used in the assay. The isocratic part is similar to the assay method for amoxicillin of the United States P harmacopeia 23. When the isocratic part is combined with gradient elut ion, the method is suitable for purity control. Five samples of amoxic illin (trihydrate and sodium salt) with varying purity were analysed. The main component and the impurities were determined. An analysis of variance proved absence of consistent laboratory bias. The laboratory- sample interaction was not significant. Estimates for the repeatabilit y and reproducibility of the method, expressed as standard deviations (SD) of the result of the determination of amoxicillin, were calculate d to be 1.1 and 1.3 respectively.