Development and validation of an UV spectrophotometric method for simultaneous determination of cilnidipine and chlorthalidone

A simple, accurate and precise dual wavelength spectrophotometric method was developed for simultaneous determination of Cilnidipine and Chlorthalidone in combined pharmaceutical dosage form. The principle for dual wavelength method is the absorbance difference between two points on the mixture spectra is directly proportional to the concentration of the component of interest. The wavelengths selected for determination of Cilnidipine are 271.83 nm and 278.34 nm, whereas, the wavelengths selected for determination of Chlorthalidone are 233.83 nm and 250.0 nm. Methanol is used as a solvent. Regression analysis of Beer’s plots showed good correlation in concentration range of 2-10 ìg/ml for Cilnidipine and 2.5-12.5 ìg/ml for Chlorthalidone. The method was validated according to ICH guidelines for various parameters like accuracy, precision, specificity, linearity, robustness, LOD and LOQ. The linearity of the proposed method was investigated in the range of 2-10 mg/mL (r2=0.9990) for Cilnidipine and 2.5 -12.5mg/mL (r2 = 0.9986) for Chlorthalidone. The limits of detection (LOD) were 0.4174 ìg/mL and 0.068 ìg/mL, and the limits of quantitation (LOQ) were 1.264 ìg/ml and 0.206 ìg/ml, for Cilinidipine and Chlorthalidone respectively The proposed method was successfully applied to determination of these drugs in commercial tablets.