Ruthenium-impregnated zeolite carbon paste electrode as a sensor for diclofenac analysis

Diclofenac is one of the most widely used anti-inflammatory drugs, making its accurate and reliable determination important for both pharmaceutical analysis and environmental monitoring. This study presents the development and characterization of a ruthenium(III)-impregnated zeolite-modified carbon paste electrode (Ru(III)-Zeo/CPE) for the electrochemical determination of diclofenac (DIC) in pharmaceutical formulations. The modified electrode was thoroughly characterized using energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The EDX results confirmed the presence of Si, Al, and Ru elements, while XRD patterns indicated that ruthenium was successfully incorporated into the zeolite framework without disrupting its amorphous structure. SEM images revealed morphological changes after modification, confirming the impregnation of Ru into the zeolite matrix. Electrochemical studies demonstrated that the Ru(III)-Zeo/CPE exhibited superior catalytic performance toward DIC oxidation compared with bare and zeolite-modified electrodes. Cyclic and square wave voltammetry analyses revealed a well-defined oxidation peak at approximately +0.4 V, with diffusion-controlled kinetics and partial adsorption contribution. The method displayed a linear response for DIC concentrations between 0.05 and 0.55 mM (R 2 = 0.9943), with detection and quantification limits of 6.72 μM and 20.2 μM, respectively. The proposed sensor showed excellent selectivity, stability, and reproducibility, with recovery values ranging from 96% to 102% when applied to real pharmaceutical samples (tablets, capsules, and ampoules). Comparative analysis with HPLC confirmed the accuracy of the results. Overall, the Ru(III)-Zeo/CPE sensor provides a simple, sensitive, and cost-effective alternative for routine DIC analysis in pharmaceutical quality control.