Optimization and Validation of Spectrophotometric and Potentiometric Methods for Determination of Lansoprazole and Omeprazole in Pure and Capsules

Abstract

Two fairly sensitive, simple and accurate methods have been developed and validated for the assay of omeprazole and lansoprazole in pure and dosage forms. The proposed spectrophotometric method was based on the oxidation of the title drugs with acidic potassium iodate solution resulted in liberation of iodine, which was then extracted and measured at λ 520 nm under the optimized experimental conditions. The method was proved to be accurate and precise and the linearity was found to be in the concentration range of 5-200 and 15-200 µg/ml, for omeprazole and lansoprazole, respectively, with apparent molar absorptivities of 2.42×10-4 and 2.01×10-4 lmol-1cm-1, and with the corresponding Sandell sensitivity value of 0.0281 and 0.0473 mgcm-2 for the afore mentioned drugs, respectively. Moreover, the kinetics of these reactions was investigated. On the other hand, the potentiometric method was based on the direct titration of the drugs with acidic N-bromosuccinimide solution with determination of the end point potentiometrically using a platinum indicator electrode under the optimum conditions. The concentration ranges were found to be 25-100 and 15-100 µg/ml with standard deviation of 0.007-0.042 and 0.005-0.034, and with relative standard deviation of 0.79-2.4 and 1.4-2.9 for omeprazole and lansoprazole, respectively. Additionally, the proposed methods could successfully be applied for the determination of the cited drugs in pharmaceutical dosage forms. The relative standard deviations for the results did not exceed 1%, confirming the high precision of the method and reproducibility of the results.