Colorimetric determination of simvastatin and lovastatin in pure form and in pharmaceutical formulations

Simple, accurate and precise colorimetric method for the determination of simvastatin and lovastatin in tablets is described. The method is based on the reaction of simvastatin or lovastatin with hydroxylamine in alkaline medium to form the corresponding hydroxamic acid derivatives which, on treatment with ferric ion in acid medium, yield highly colored ferric-chelate complex with maximum absorption at 513 nm. Beer's law is obeyed in the concentration ranges 0.04–0.4 mg ml−1 for both simvastatin and lovastatin, respectively. Molar absorptivity values, as calculated from Beer's law data, were found to be 1.15 × 103 and 1.09 × 103 l mol−1 cm−1 for simvastatin and lovastatin, respectively. Optimal experimental parameters for the reaction have been studied. The validity of the described procedures was assessed. Statistical analysis of the results reflects that the proposed procedures are precise, accurate and easily applicable for the determination of simvastatin and lovastatin in pure form and in pharmaceutical preparation.