| Summary: | Two simple and sensitive spectrophotometric methods have been developed for the determination of simvastatin (SMT) in pure form and in tablets using insitu generated bromine, and p-phenylenediamine (PPDA) or o-dianisidine (ODA) as reagents. The methods are based on the bromination of SMT by a measured excess of in situ bromine in acid medium followed by the determination of unreacted bromine by reacting with PPDA and measuring the resulting red colour at 510 nm (method A) or reacting with ODA and measuring the absorbance at 470 nm (method B). The conditions for the assay have been optimized. Beer’s law is obeyed over the concentration ranges 20-120 and 2- -12 μg/ml for method A and method B, respectively. The calculated molar absorbtivities are 2.24×103 and 1.91×104 dm3 mol-1 cm-1 for the method A and the method B, respectively; 0.1868 and 0.0115 μg/cm2 being the corresponding Sandell sensitivities. The LOD and LOQ for method A are found to be 2.96 and 8.97 μg/ml, and the respective values for method B are 0.14 and 0.42 μg/ml. The intra-day and inter-day precision and accuracies were checked. The assay precision was less than 5 % CV and the accuracy was 97.38-103.4 %. The methods were used for the determination of SMT in tablets. No interference from the excipients added to tablets was found. The accuracy and validity of the methods were further ascertained by recovery studies via the standard addition technique.
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