Spectrophotometric microdetermination of ampicillin and cloxacillin in pure form, mixtures and in pharmaceutical preparations using bromothymol blue

ABSTRACT

A simple, accurate and highly-sensitive spectrophotometric method for the rapid determination of ampicillin trihydrate and cloxacillin sodium in the pure state, their mixtures and pharmaceutical preparations was described. The method is based on the formation of deep color complexes by the reaction of ampicillin trihydrate [amp.] or cloxacillin sodium [clox.] with bromothymol blue [BTB] at 25 and 50C +/- 2C, respectively, in basic solution containing 30% [v/v] acetone. The effect of pH, time, temperatures, solvent and amount of BTB have also been studied. Beer's law is obeyed within the concentration range 0.4-18 and 0.4-20 mug/ml of amp. and clox., respectively, whereas the optimum concentration ranges as evaluated by Ringbom's method are 1-16 and 1-17 mug/ml, respectively. The specific absorptivity, molar absorptivity, Sandell sensitivity, standard deviation and recovery% are evaluated. The method has been used to determine each of amp. and clox. in pure form, synthetic binary mixtures and pharmaceutical preparations [capsules, vials, syrup and drops] containing both of them