Abstract: 
In this study, new, rapid UV spectrophotometry (UV) and first-order derivative spectrophotometry (¹D) methods were developed for the determination of diclofenac in pure and tablets. The solvent system and wavelength of detection were optimized in order to maximize the sensitivity of the proposed methods. Parameters such as linearity, precision, accuracy, specificity, stability, limit of detection and limit of quantification were studied according to the International Conference on Harmonization Guidelines. Calibration curve was linear between the concentration range of 2-14 μg ml^-1. Within- and between-day precision values for diclofenac were less than 4.27%, and accuracy (relative error) was better than 2.71%. The mean recovery value of diclofenac was 100.1% for pharmaceutical preparations. The developed method was successfully applied to tablet formulations and the results were compared statistically with each other.

Keywords: Diclofenac, UV Spectrophotometry, First-Order Derivative Spectrophotometry, Validation.