Spectrophotometric determination of zidovudine with 4-N-methyl aminophenol(metol) and chloramine-T

A simple spectrophotometric method is proposed for the determination of zidovudine(ZDV) in bulk drug and in pharmaceutical preparations using chloramine-T (CAT) as an oxidimetric agent. The method is based on the oxidation of zidovudine by a known excess of oxidant (CAT) in acid medium followed by the estimation of unreacted amount of oxidant via a charge-transfer complexation reaction involving metol and sulphanilic acid. The reacted oxidant corresponds to the drug. The purple-red product absorbs maximally at 530 nm and Beer's law is obeyed over a range 5 - 87.5 mu g ml(-1). The apparent molar absorptivity is calculated to be 2.7 x 10(3) l mol(-1) cm-land the corresponding Sandell sensitivity value is 0.099 mu g cm(-2). The limit of detection and quantification are found to be 1.44 and 4.35 mu g ml(-1), respectively. Intra-day and inter-day precision and accuracy of the method have been evaluated as per the current ICH guidelines. The method was successfully applied to the assay of ZDV in tablet/capsule preparations and the results were statistically compared with those of the reference method by applying the Student's t-test and F-test. No interference was observed from the common tablet/capsule excipients. The accuracy of the method was further ascertained by performing recovery studies via standard-addition method.