An efficient ZrO2/Co3O4/reduced graphene oxide nanocomposite electrochemical sensor for simultaneous determination of gallic acid, caffeic acid and protocatechuic acid natural antioxidants

A novel efficient ZrO2/Co3O4/reduced graphene oxide (rGO) nanocomposite catalyst was prepared by a reflux method. Then, the nanocomposite was positively characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). Afterward, the nanocomposite was fabricated into an electrochemical sensor by casting it onto the surface of a fluorine doped tin oxide (FTO) electrode. The ZrO2/Co3O4/rGO nanocomposite/FTO exhibited a synergistic catalytic effect toward oxidation of gallic acid (GA), caffeic acid (CA) and protocatechuic acid (PA) with the oxidation peak currents increasing linearly with concentrations in the range of 6.24-477.68 nmol L-1, 2.48-524.90 nmol L-1 and 5.40-424.96 nmol L-1 and the limits of detection (S/N = 3) of 1.56 nmol L-1 for GA, 0.62 nmol L-1 for CA and 1.35 nmol L-1 for PA. The proposed electrode was then successfully used for simultaneous determination of the three species in fruit juice, rice and tea samples with satisfactory recoveries, showing the feasibility of its use for electrochemical sensing application. (C) 2016 Elsevier Ltd. All rights reserved.