Spectrophotometric determination of ampicillin and amoxycillin with Ce(IV)and arsenazo III

A simple and sensitive spectrophotometric method for the determination of a mpicillin and amoxycillin in a system: Ce(IV), reductant, arsenate III was carried out. Colorimetric method for the determination of the analyte is ba sed on reduction of cerium(IV) ions with ampicillin and amoxycillin. The ce rium(III) ions formed were complexed with arsenate III and spectrophotometr ically determined. Beer's law is obeyed in the concentration range from 2.5 to 25 mug and from 2 to 10 mug in 25ml for ampicillin and amoxycillin, res pectively. The absorbance was measured at lambda (max) = 655 nm at pH 3.2-3 .6 in 1 cm cuvettes. The molar absorptivity of the colour system was found to be 2.7 x 10(5) 1 mol(-1) cm(-1) for ampicillin and 5.2 x 10(5) 1 mol(-1) cm(-1) for amoxycillin. The method has been successfully applied for the d etermination of ampicillin and amoxycillin in pharmaceuticals.