Vanadophosphoric acid as a modified reagent for the spectrophotometric determination of certain cephalosporins and their dosage forms

Vanadophosphoric acid in acidic medium is proposed as a modified reagent fo r the spectrophotometric determination of cephalexin, cephaprine sodium, ce fazolin sodium, and cefotaxime in pure samples and in pharmaceutical prepar ations. The method is based on acid hydrolysis of cephalosporins and subseq uent oxidation with vanadophosphoric acid. The resulting solution exhibits maximum absorption at about 516 nm. The effects of reaction conditions were investigated. Lambert-Beer's law was obeyed over a concentration range of about 0.4-45 mu g.cm(-3). For more accurate results, Ringbom optimum concen tration ranges were obtained, and the molar absorptivities and Sandell sens itivities were derived. The proposed method was applied to the determinatio n of the drugs in pharmaceutical formulations; the results demonstrated tha t the proposed method is as accurate, pecise, and reproducible as the offic ial methods.