A novel use of oxidative coupling reactions for determination of some statins (cholesterol-lowering drugs) in pharmaceutical formulations

New, accurate and reliable spectrophotometric methods for the assay of three statin drugs, atorvastatin calcium (AVS), fluvastatin sodium (FVS) and pravastatin sodium (PVS) in pure form and pharmaceutical formulations have been described. All methods involve the oxidative coupling reaction of AVS, FVS and PVS with 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate (MBTH) in the presence of Ce(IV) in an acidic medium to form colored products with λmax at 566, 615 and 664 nm, respectively. Beer's law was obeyed in the ranges of 2.0–20.0, 4.9–35.4 and 7.0–30.0 μg mL−1 for AVS–MBTH, FVS–MBTH and PVS–MBTH, respectively. Molar absorptivities for the above three methods were found to be 3.24 × 104, 1.05 × 104 and 0.68 × 104 L mol−1 cm−1, respectively. Statistical treatment of the experimental results indicates that the methods are precise and accurate. The proposed methods have been applied to the determination of the components in commercial forms with no interference from the excipients. A comparative study between the suggested procedures and the official methods for these compounds in the commercial forms showed no significant difference between the two methods.