Development and Validation of a Simple Spectrophotometric Method for Quantitative Determination of Sodium Diclofenac in Modified-Release Tablets

In this study, a rapid, simple, economical and accurate spectrophotometric process was developed for the determination of sodium diclofenac in modified release tablets using ethanol 96% as an available and non-toxic solvent. Sodium diclofenac standard solution was scanned under UV (200-400 nm) in a 1 cm quartz cell to determine the maximum absorption wavelength which was 285 nm. This method was validated in accordance with the requirements of the International Conference on Harmonization (ICH), where the calibration curve showed linearity in the studied concentration range (5-30 μg mL-1) with correlation coefficient R² = 0.9993. The relative standard deviation of the accuracy studies was within the acceptable range (<2%). This method also achieved an excellent recovery ratio (Mean recovery ± S.D. = 100.44% ± 0.81) with high sensitivity (limit of detection 1.10 μg mL-1 and quantitation limit of 3.34 μg mL-1). The developed process applied successfully to determine sodium diclofenac in four commercial pharmaceuticals products (A, B, C and D) marketed locally as modified-release tablets. The product C showed the highest assay value 106% and product B showed the lowest value 98%. Hence, we recommend using this method to quantitatively determine of sodium diclofenac in pharmaceutical dosage forms.