Electrochemical studies and differential pulse polarographic analysis of lansoprazole in pharmaceuticalsThis study was taken partly from the MSc thesis of Ceren Yardımcı and presented at the 6th International Symposium on Pharmaceutical Sciences, 27–29th June 2000, Ankara, Turkey.

Abstract

The electrochemical reduction of lansoprazole was investigated by cyclic voltammetry and direct current and differential pulse polarography. The reduction potential was −1.32 V vs. Ag/AgCl with a dropping mercury electrode in a supporting electrolyte consisting of phosphate buffer (pH 9.0)–tetramethylammonium iodide (4 + 1). The reversibility of the electrode reaction and the type of limiting current were studied. The temperature coefficient and the diffusion constant were determined. A mechanism for the electrode reaction was proposed. A new simple and sensitive differential pulse polarographic method was also developed for the quantification of lansoprazole. A linear calibration graph was obtained in the range 0.04–11.35 μg ml⁻¹. The limit of detection was 0.03 μg ml⁻¹ and the intra- and inter-day precisions were 0.84–2.32 and 0.72–3.09%, respectively. The developed method was applied to six different commercial pharmaceutical capsule preparations containing enteric-coated granules. The relative standard deviations ranged from 1.36 to 2.85%. Recovery studies for the accuracy of the method were performed by adding a synthetic mixture to known amounts of lansoprazole and the mean recovery was 100.45%. The data obtained from commercial preparations were compared with those from a published spectrophotometric method. No difference was found statistically.