Comparative study of three modified numerical spectrophotometric methods: an application on pharmaceutical ternary mixture of aspirin, atorvastatin and clopedogrel.

Three novel numerical methods were developed for the spectrophotometric multi-component analysis of capsules and synthetic mixtures of aspirin, atorvastatin and clopedogrel without any chemical separation. The subtraction method is based on the relationship between the difference in absorbance at four wavelengths and corresponding concentration of analyte. In this method, the linear determination ranges were 0.8-40 μg mL(-1) aspirin, 0.8-30 μg mL(-1) atorvastatin and 0.5-30 μg mL(-1) clopedogrel. In the quotient method, 0.8-40 μg mL(-1) aspirin, 0.8-30 μg mL(-1) atorvastatin and 1.0-30 μg mL(-1) clopedogrel were determine from spectral data at the wavelength pairs that show the same ratio of absorbance for other two species. Standard addition method was used for resolving ternary mixture of 1.0-40 μg mL(-1) aspirin, 0.8-30 μg mL(-1) atorvastatin and 2.0-30 μg mL(-1) clopedogrel. The proposed methods were validated. The reproducibility and repeatability were found satisfactory which evidence was by low values of relative standard deviation (<2%). Recovery was found to be in the range (99.6-100.8%). By adopting these methods, the time taken for analysis was reduced as these methods involve very limited steps. The developed methods were applied for simultaneous analysis of aspirin, atorvastatin and clopedogrel in capsule dosage forms and results were in good concordance with alternative liquid chromatography.