Quantitative Spectrophotometric Analysis of Etoricoxib in Pharmaceutical Tablets Employing a Charge-Transfer Reaction

A facile, selective, and extraction-free spectrophotometric procedure has been established for the quantitative analysis of etoricoxib (ETO) in pharmaceutical tablet formulations. The method relies on the formation of a charge-transfer complex through the reaction between ETO, functioning as an n-donor, and chloranilic acid (CAA), acting as a π-acceptor, in acetonitrile solvent. An orange-red color with an absorbance maximum at 520 nm is produced when the formed complex dissociates into a chloranilic acid radical anion. The method obeys Beer’s law over the concentration range from 5 to 175 µg/mL for ETO. A molar absorptivity value was determined to be 1.71 × 10³ L/(mol.cm) and a Sandell’s sensitivity value was calculated as 0.2103 µg/cm². In addition, the calculations revealed that the limits of quantification and detection were 5.82 and 1.92 µg/mL, respectively. Job’s method of continuous variation was employed to test the reaction stoichiometry, which was established to be 1:1 (drug: reagent). When the findings were statistically compared using the student’s t-test and F-ratio at a 95% confidence level, accuracy and precision did not significantly differ between the developed method and the reference method. The proposed method was effectively used to estimate the amount of ETO drug present in both pure form and in commercial tablets. Quality control laboratories can routinely analyze this drug using the described method.