SIMULTANEOUS ESTIMATION OF MOXONIDINE AND AMLODIPINE BESYLATE IN THEIR PHARMACEUTICAL DOSAGE FORM BY STABILITY-INDICATING LC METHOD

A sensitive, selective and precise liquid chromatographic method has been developed and validated for simultaneous determination of moxonidine and amlodipine besylate both as bulk drug and in formulation. Phenomenex Luna c18 column (250 x 4.6 mm id, 5μm particle size) chromatographic column equilibrated with mobile phase methanol: acetonitrile: 0.02M Kh2PO4 buffer (50:10:40, V/V/V) was used. Mobile phase flow rate was maintained at 1 mL/min and effluents were monitored at 237 nm. The sample was injected using a 20 μL fixed loop, and the total run time was 10 min. The retention times of moxonidine and amlodipine besylate were observed to be 2.9 and 6.9, respectively. The linear regression analysis data for the calibration plots showed a good linear relationship for moxonidine and amlodipine besylate over a concentration range of 0.05-20 μg/mL and 0.05-20 μg/mL, respectively. The method was validated for precision, robustness and recovery. The limit of detection and limit of quantification for moxonidine and amlodipine besylate were found to be 0.0030 μg/mL and 0.0036 μg/mL, 0.015μg/mL and 0.020 μg/mL, respectively. Moxonidine and amlodipine besylate stock solutions were subjected to acid and alkali hydrolysis, chemical oxidation, dry heat degradation and photo degradation. The degraded product peaks were well resolved from the pure drug peak with significant difference in their Rt values. Stressed samples were assayed using developed hPLc method. Statistical analysis showed that the method is repeatable, selective, and precise. Degradation products produced as a result of stress studies did not interfere with the detection of moxonidine and amlodipine besylate and the assay can thus be considered stability-indicating.