High-performance liquid chromatographic method for potency determination of cephalexin in commercial preparations and for stability studies

A reversed-phase column liquid chromatographic method was developed for the assay of cephalexin in bulk drugs and pharmaceutical preparations. An equation was derived showing a linear relationship between peak-area ratio of cephalexin to acetaminophen (internal standard) and the cephalexin concentration over a range of 0.2~1.75 mg/ ml (r = 0.9999). Standard addition recoveries were generally greater than 99.5%. The relative standard deviations were between 0.38 and 0.63% in the within-day assay, and 1.05% in the between-day assay. The column liquid chromatographic assay results were compared with those obtained from a microbio logical assay, which indicated that the proposed method is a suitable substitute for the microbiological method for potency assays and stability studies of cephalexin preparations.