Two simple, rapid and selective spectrophotometric procedures were developed for the determination of amoxicillin and cefadroxil. The methods are based on the selective oxidation of the drugs with N-bromosuccinimide or N-chlorosuccinimide in an alkaline medium to give an intense yellow product (λmax= 395 nm). The reaction conditions were studied and optimized. The reactions obey Beer's law over the range 1–20 µg ml–1 for the two drugs with the two reagents. Interferences from other antibiotics, additives and common degradation products were investigated. The proposed methods were applied to the analysis of pharmaceutical formulations containing amoxicillin, either alone or in combination with potassium clavulanate or flucloxacillin. They were also applied to the analysis of some cefadroxil dosage forms. The results obtained compared favourably with those obtained with other reported methods.
