Study of the Effect of Type and Ratio of Active material on the Nernstian Response of a Modified Carbon Paste Electrode for Diclofenac Sodium Using the Potentiometric method

Abstract

This research studied the effect of the type and ratio of active material in the modified carbon paste on the Nernstian slope for sodium diclofenac (NaDCF), and evaluated the suitability of the prepared pastes as surfaces for selective electrodes to determine the diclofenac ion in aqueous solutions. Various electroactive materials were investigated, and their effects on the Nernstian slope were observed within the concentration range of the studied compound [10⁻⁵–10⁻²] mol·L⁻¹. Silver–diclofenac complex (Ag–DCF), diclofenac with 1,10-phenanthroline, and silver oxide compound were used as electroactive materials. It was observed that the response of the diclofenac–1,10-phenanthroline complex to the studied substance was very weak across different ratios. The study demonstrated that the electrode composed of 7% silver–diclofenac complex, 46.5% dibutyl phthalate (DBP), and 46.5% graphite (GP) powder was the most effective, although the electrode with 9% silver oxide, 45.5% dibutyl phthalate, and 45.5% graphite powder showed better results in terms of slope value and correlation coefficient. However, it lacked repeatability, which is considered the main criterion for adopting an electrode as an effective tool in electrochemical measurements. The effect of medium pH and response time was also studied on the electrode modified with the silver–diclofenac complex, and the results indicated that pH = 8 was the optimal value, with a Nernstian slope of 49.63 mV/decade at a response time ranging between 10–30 seconds.