Differential pulse voltammetric assay of H1-antihistamine fexofenadine in pharmaceutical formulations using a bare glassy carbon electrode

A simple differential pulse voltammetric procedure was developed for the determination of the H₁-antihistamine fexofenadine in commercial pharmaceutical formulations using a bare glassy carbon electrode. The electrochemical behavior of fexofenadine was investigated by cyclic voltammetry in phosphate buffer solutions. The analyte provided an irreversible anodic signal at approximately +0.75 V versus an Ag/AgCl/3 mol·L⁻¹ KCl reference electrode in phosphate buffer at pH 10, where the highest current response was obtained. The influence of scan rate indicated that the oxidation process was predominantly diffusion-controlled. Differential pulse voltammetry was optimized and then used for quantitative analysis. Under the optimized conditions, the method provided a linear concentration range from 9.5 to 67.9 μmol·L⁻¹, a detection limit of 2.7 μmol·L⁻¹, and repeatability expressed as a relative standard deviation of 4.8 % for twelve replicate measurements. The influence of selected tablet excipients, including glucose, sucrose, starch, and cellulose, was evaluated, with changes in the integrated fexofenadine response remaining below 5 % at all tested mass ratios. The proposed procedure was applied to the assay of two commercial fexofenadine tablet products, Allegra^® 120 mg and Ewofex^® 120 mg, using the standard addition method, providing recoveries of 99.4 % and 98.7 %, respectively. The method offers a simple option for the differential pulse voltammetric assay of fexofenadine in tablet formulations.