Kinetic Spectrophotometric Determination of Betaxolol, Clopidogrel and Imidapril in Pharmaceutical Preparations

A simple, accurate and sensitive kinetic method has been developed for the determination of three cardiovascular drugs: Betaxolol, Clopidogrel, and Imidapril in pharmaceutical formulations. The method is based on the alkaline oxidation of the selected drugs with potassium manganate(VII) at room temperature (25°C) to produce a bluish-green colored product. The reaction is followed spectrophotometrically by measuring the rate of change of absorbance at 610 nm as a function of time. The fixed-time (ΔA) method is adopted for constructing the calibration curves, which were found to be linear over the concentration ranges of 0.40-2.0 μg ml-1 Betaxolol, 1.0-10.0 μg ml-1 Clopidogrel, and 6.0-16.0 μg ml-1 Imidapril. The implemented fixed times were 15 min for Betaxolol and Clopidogrel and 10 min for Imidapril. The proposed method has been successfully applied to pharmaceutical formulations of each drug. The percentage relative error and the coefficient of variation were less than 0.6 and 1.2 respectively. The lower limits of quantitation (LOQ) were 9.75x10-7 M Betaxolol, 3.62x10-6 M Clopidogrel, and 4.22x10-6 M Imidapril. The determination of the investigated drugs by the fixed-concentration and the rate-constant methods is feasible with the regression equations obtained, but the fixed-time method proves to be more applicable.