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 fo r the assay of cephalexin in bulk drugs and pharmaceutical preparation s. 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). St andard addition recoveries were generally greater than 99.5%. The rela tive 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 chromato graphic assay results were compared with those obtained from a microbi ological assay, which indicated that the proposed method is a suitable substitute for the microbiological method for potency assays and stab ility studies of cephalexin preparations.