Electrochemical determination of gallic acid in the presence of p-coumaric acid using an rGO/ZIF-8 modified carbon paste electrode: Application to fruit juice analysis

Abstract

A reduced graphene oxide/zeolitic imidazolate framework-8 modified carbon paste electrode (rGO/ZIF-8/CPE) was fabricated for the electrochemical determination of gallic acid (GA). The morphology and structure of rGO/ ZIF-8 were confirmed by field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analyses, indicating the successful formation of the composite. Electrochemical studies using electrochemical impedance spectroscopy EIS, chronoamperometry spectroscopy, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) demonstrated enhanced electron transfer and catalytic activity toward GA in 0.01 M PBS (pH 2.0), and two linear response range, limit of detection (LOD) and sensitivity toward GA, of 0.03–1.0 μM and 3.0–100.0 μM, and 9.0 nM, respectively. Also, the diffusion coefficient (D) and charge transfer coefficient (α) for GA are determined as 4.78 × 10–5 cm2.s-1 and 0.606, respectively. The fabricated sensor was successfully applied to the determination of GA in fruit juice samples (lemon, orange and sour orange) with recoveries ranging from 90 to 109%.