Novel spectrophotometric determinations of some cephalosporins following azo dye formation with p-dimethylaminobenzaldehyde

A new simple, accurate and cost-effective spectrophotometric method has been developed for the analysis of some cephalosporins (ceftriaxone, ceftazidime, cefixime, cefotaxime and cefuroxime) in bulk samples and pharmaceutical dosage forms. The reaction involves a two-step process of diazotization of the cephalosporins with acidified NaNO2 at 0–5 °C and coupling with acidified p-dimethylaminobenzaldehyde (DMAB). Optimal temperature and time for coupling were established at 50 and 60 °C with coupling time ranging from 15 to 20 min. All the cephalosporins gave azo adducts with DMAB that absorbed light optimally at 400–430 nm. The reaction with DMAB occurred at a stoichiometric ratio of 1:1. Optimization of DMAB concentration revealed the superiority of using 0.3% DMAB in 0.0625 M H2SO4 with the best diluting solvent being methanol. Beer’s law was obeyed at concentrations ranging from 5 to 60 μg/mL with correlation coefficients >0.9980 in all cases. Overall recoveries were of the order of 95–103% with errors generally less than 6%. The method was successfully applied to the determination of the cephalosporins in dosage forms and it was found to be equivalent accuracy to the official (USP and BP) HPLC assay procedures for these drugs. There was no interference from commonly adopted excipients. The method could find application as a rapid and cost-effective alternative for the quality control of these cephalosporins, especially in preliminary studies