Simultaneous determination of olmesartan medoxomil and amlodipine besylate in pharmaceutical formulations by capillary zone electrophoresis

A simple, efficient and reliable capillary zone electrophoresis method with diode array detection was developed and validated for the simultaneous determination of olmesartan medoxomil and amlodipine besylate in their binary mixtures. The optimum separation for these compounds was achieved with a fused - silica capillary column (i.d. 75.0 µm, total length 48.5 cm and effective length 40.0 cm) and 40.0 mM citrate buffer at pH 6.0 as the running buffer. The samples were injected hydrodynamically for 3 s at 50 mbar and applied voltage was + 15 kV at 30 °C capillary temperature. Detection wavelength was set at 235 nm. Valsartan was used as internal standard. The method was validated with respect to stability, linearity, sensitivity, precision, accuracy, recovery and selectivity. The linear calibration range was found to be 2.00 - 30.00 µg/mL for olmesartan medoxomil and amlodipine besylate. The limits of detection (LOD) were 0.05 µg/mL for both compounds. The relative standard deviations (RSD) of the proposed method ranged between 1.51 and 2.49 % for intra-day precision and 1.51 and 3.73 % for inter-day precision. The developed and validated method successfully applied for the simultaneous determination of olmesartan medoxomil and amlodipine besylate in their pharmaceutical formulations. Colegio de Farmacéuticos de la Provincia de Buenos Aires