Using PANI|In2O3 Composite for Indirect Electrochemical Detection of Diclofenac Sodium via Polyaniline Oxidation Peak

The unusual electrochemical, catalytic, and electronic properties of conductive polymer composites with metal oxides, owing to their synergistic effects, have attracted continued interest in the past decade for diverse applications in electroanalysis and electrocatalysis. Herein, we present a novel method for indirect determination of diclofenac (DCF) sodium using a PANI|In2O3 composite. A glassy carbon electrode (GCE) modified with a thin PANI|In2O3 layer was synthesized by cyclic voltammetry (CV) from a 0.3 M H2SO4 solution. Electrochemical impedance spectroscopy (EIS) measurements demonstrated that the PANI|In2O3 composite has a significantly higher Rct value 624.0 Omega than the pure polyaniline film (14.0 Omega). CVs of bare GCE demonstrated the irreversible oxidation of diclofenac, characterized by an anodic peak at a potential of 0.6 V. Differential pulse voltammograms (DPVs) of DCF on a GCE|PANI electrode showed two pronounced anodic peaks (jpa), which were responsible for the electrochemical oxidation of polyaniline (I) and oxidation of DCF (II). Modification with In2O3 dramatically decreased the current density of peak II by inhibiting the oxidation of DCF, and on the contrary, it increased the intensity of peak I tens of times. The GC|PANI|In2O3 electrode can be used as an electrochemical sensor for the determination of diclofenac at low concentrations between 1 x 10-6 M to 1 x 10-4 M, and jpa - CDCF has a correlation coefficient of 0.95. The GC|PANI|In2O3 material exhibited a limit of detection of 181 nM and a linear range of 1-100 mu M for the DCF sensor.