Three Spectrophotometric Methods for Simultaneous Determination of Ampicillin and Dicloxacillin in Presence of Their Major Impurity 6-Aminopenicillanic Acid

Three simple, selective, accurate, precise and economic spectrophotometric methods were developed for simultaneous determination of ampicillin (AMP) and dicloxacillin (DX) in presence of their major impurity namely; 6-aminopenicillanic acid (APA). Method A is derivative spectrophotometry, where DX was determined by first derivative D? spectrophotometric method at 207.4 nm, while AMP was determined by second derivative D2 spectrophotometric method at 229.6 nm. Method B is first derivative of ratio spectra spectrophotometry which allows determination of both AMP at 265.4 nm and DX at 244.2 nm without interference of each other and in presence of 6-amino penicillanic acid (APA). Method C is the mean centering of ratio spectra spectrophotometric (MCR) method, which depends on measuring the mean centered values of ratio spectra of AMP, DX and APA at 223, 237 and 209 nm respectively. The accuracy and precision of the developed methods were determined while their selectivity was tested by their application for determination of the studied component in different synthetic prepared mixtures. Additionally, the developed methods were successfully used for determination of the studied drugs in their dosage form. Statistical comparison of the suggested methods with the reported HPLC one using F and student’s t- tests showed no significant difference regarding both accuracy and precision. The specificity of the developed methods was investigated by analyzing different laboratory prepared mixtures of the AMP and DX.