Validated voltammetric determination of olmesartan medoxomil: Method development and electrochemical behaviors investigation

Abstract

In this study, a sensitive, simple and rapid voltammetric method was developed and validated for the determination of olmesartan medoxomil in pharmaceutical formulations. The experimental and instrumental parameters affecting the peak current of olmesartan medoxomil were investigated and optimized. For this purpose, square-wave voltammetry at a hanging mercury drop electrode in electrolytes of different pH and buffers was tried. Olmesartan medoxomil showed a reduction peak between the pH range 5.0 to 8.0, and phosphate buffer at pH 6.5 was selected as the optimum electrolyte condition for analysis, since well-defined peaks were obtained. The following instrumental parameters were employed for analytical application: frequency 50 Hz, scan increment 5 mV and pulse amplitude 25 mV. In these optimum conditions highly sensitive measurements of olmesartan medoxomil were achieved. Validation parameters such as linearity, sensitivity, selectivity, precision, accuracy, ruggedness and robustness for the developed method were evaluated. The square-wave voltammetric peak currents increased linearly with the corresponding olmesartan medoxomil concentration in the range of 1.00–14.56 μg mL⁻¹ (r = 0.9983) with a detection limit of 0.50 μg mL⁻¹ and limit of quantitation of 1.00 μg mL⁻¹. The developed method was successfully used for determination of olmesartan medoxomil in tablets and the data were compared with ones obtained from the capillary electrophoresis method given in the literature. Possible interferences by several substances usually present in the pharmaceutical formulations have been also evaluated. The percentage recoveries varied from 98.20 to 100.26%. It has been shown that olmesartan medoxomil could be directly determined in the presence of excipients from tablets by the developed method without the necessity for prior extraction or interaction with any reagent during the analysis.