The spectrophotometric determination of ampicillin and cloxacillin in combined injections
A method is described for the determination of ampicillin and cloxacillin in injections. Ampicillin is determined by an absorbance difference technique based on the higher absorbance of ampicillin at 268 nm in a solution at pH 5 than in one at pH 9. Cloxacillin is determined by measurement of the absorbance at 275 nm and the application of a small correction for the absorbance of ampicillin. The accuracy, precision and specificity of the method are discussed. The analytical results obtained for commercial samples of ampicillin-cloxacillin (1 + 1 and 2 + 1) mixtures are compared with those obtained by microbiological assay.