EXPLORING UV-SPECTROPHOTOMETRIC TECHNIQUES FOR ANALYSIS OF MULTICOMPONENT DRUG FORMULATIONS

The objective of the current research work includes development and validation of novel, precise and accurate UV-visible spectrophotometric techniques for the analysis of Cilnidipine and Chlorthalidone without the need of prior separation by employing mathematical spectrophotometric manipulations, which utilize absorbance relationships to resolve overlapping spectral components. Two methods, namely Ratio Subtraction Coupled with Spectrum Subtraction (RS-SS) and Absorption Factor Method (AFM) were developed for the simultaneous estimation of Cilnidipine (CIL) and Chlorthalidone (CHLOR). In the RS-SS method, CIL and CHLOR were quantified at 365 nm and 275 nm, respectively, using a divisor concentration of 8 µg/mL of CIL. In the AFM method, CHLOR concentration was quantified directly by recording the absorbance at 275 nm. For the estimation of CIL, an absorption factor was calculated from the absorbance values at two selected wavelengths, 275 nm and 365 nm. These values were applied in the AFM equation to compute the absorbance attributable to CIL in the mixture. The developed methods were validated in accordance with ICH Q2 (R2) guidelines. Linearity was established over the concentration ranges of 4–12 µg/mL for CIL and 5–15 µg/mL for CHLOR, with good correlation coefficients. Precision was confirmed through intraday and interday studies, with % RSD values below 2%. Robustness was evaluated by small deliberate variations in wavelength, solvent composition, divisor concentration and absorption factor with %RSD <2%. Accuracy was demonstrated by recovery studies conducted at three concentration levels (80%, 100%, and 120%), with recovery results ranging between 98% and 102%, confirming the reliability and robustness of the methods. Greenness was evaluated using Complex GAPI and AGREE software.