The present research works aims to develop a simple, sensitive, accurate and reproducible Q-absorbance ratio method for the simultaneous estimation of cilnidipine (CILN) and metoprolol succinate (METO) in their combined dosage form. Q-absorbance ratio method uses the ratio of absorbance at two selected wavelengths, one which is an Isobestic point at 230 nm in methanol. The second wavelength is used 240 nm, which is λmax of CILN in methanol. The regression analysis data for the calibration plot showedgood linear relationship in the concentration range of 4-8 μg/ml for CILN and 20-40 μg/ml for METO with R2 value greater than 0.998. Accuracy of this method was determined by recovery studies and showed % recovery between 99 to 103%. Intraday and interday precision was checked for all methods and mean %RSD was found to be less than 2. This method was successfully applied for estimation of cilnidipine and metoprolol succinate in marketed formulation. The results were found to be within acceptance criteria according to ICH Q2 R1 guidelines.
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