Optimized and Validated Spectrophotometric Methods for the Determination of Verapamil Hydrochloride in Drug Formulations

Two spectrophotometric methods have been described for the assay of verapamil hydrochloride in drug formulations. Method A is based on the oxidation of the drug with potassium metaperiodate in sulfuric acid medium to give colored product, which absorbs maximally at 425 nm. Method B involves the formation of colored chloroform extractable ion-pair complex of the drug with tropaeolin 000 No.1 at pH 4.0 showing absorption peak at 400 nm. Under the optimized experimental conditions, Beer’s law is obeyed in the concentration ranges of 12.5-187.5 and 2.0-30.0 μg mL for methods A and B, respectively. Results of analyses were validated statistically and through recovery studies. Statistical comparison of the results with the reference method shows excellent agreement and indicates no significant difference in accuracy and precision. Both methods have been successfully applied to the determination of verapamil hydrochloride in drug formulations.