Interaction between Amorphous Zirconia Nanoparticles and Graphite: Electrochemical Applications for Gallic Acid Sensing Using Carbon Paste Electrodes in Wine

Abstract

Amorphous zirconium oxide nanoparticles (ZrO2) have been used for the first time, to modify carbon paste electrode (CPE) and used as a sensor for the electrochemical determination of gallic acid (GA). The voltammetric results of the ZrO2 nanoparticles-modified CPE showed efficient electrochemical oxidation of gallic acid, with a significantly enhanced peak current from 261 µA ± 3 to about 451 µA ± 1. The modified surface of the electrode and the synthesised zirconia nanoparticles were characterised by scanning electrode microscopy (SEM), Energy-dispersive x-ray spectroscopy (EDXA), X-ray powdered diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). Meanwhile, the electrochemical behaviour of GA on the surface of the modified electrode was studied using differential pulse voltammetry (DPV), showing a sensitivity of the electrode for GA determination, within a concentration range of 1 × 10−6 mol L−1 to 1 × 10−3 mol L−1 with a correlation coefficient of R2 of 0.9945 and a limit of detection of 1.24 × 10−7 mol L−1 (S/N = 3). The proposed ZrO2 nanoparticles modified CPE was successfully used for the determination of GA in red and white wine, with concentrations of 0.103 mmol L−1 and 0.049 mmol L−1 respectively.

Electrochemical Sensor for Determination of Various Phenolic Compounds in Wine Samples Using Fe3O4 Nanoparticles Modified Carbon Paste Electrode

“…As the peak current is higher in MCPE than CPE, the shoulders of the peaks observed from MCPE are also broader than the CPE. This behavior can be suggested to be a result of increased electroactive surface area by incorporating the Fe 3 O 4 nanoparticles [ 23 ], which is similar to the results obtained from the determination of the electroactive surface area of the electrodes ( Figure 4 and Figure S2 ). If the modified electrode functioned as an electrocatalyst or the reaction was electro-catalyzed, there would have been a reduction in the peak potential, which suggests a reaction that is faster with a less overpotential [ 23 ].…”

“…The phenolic compounds show visible peak currents higher in MCPE and lower in CPE [ 21 , 22 , 28 ]. These electrochemical behaviors of the analytes observed from the peak currents, visibly shifting, could be suggested to be a result of the nanoparticles at the electrode surface increasing the current signal as a result of the catalytic effect of the nanoparticles, thus making the current signals to increase in the modified electrodes more than the unmodified electrodes [ 23 ].…”

“…The carbon paste mixture, as the control (CPE), was prepared by hand, mixing 60 mg of carbon powder with 40 mg of paraffin oil to obtain a homogeneous mixture of 60 vs. 40 mg. The carbon paste mixture prepared with Fe 3 O 4 nanoparticles (MCPE) contained 60.0 mg carbon powder, 30.0 mg of paraffin oil, and 10.0 mg of Fe 3 O 4 powder in a ratio of 60:30:10 (wt/wt/wt%) [ 23 ]. The homogenous pastes were packed to fill two different 4 mm diameter cavity of Teflon tubes, one for the CPE and the other for the MCPE.…”

“…After which, they were stirred for two minutes with a magnetic stirrer. Measurements from the DPV analysis were recorded from each beaker that contains the wine and aliquots of the standard phenolic compounds [ 23 ].…”

“…However, MCPE with nanomaterials has recently shown a substantial increase in the electrochemical properties of the analyzed compounds. The main advantages of using MCPE with nanoparticles over macro electrodes or unmodified CPE are effective surface area, increased sensitivity and selectivity, and effective mass transport by mediating electron-transfer between electroactive species during reactions in solution [ 23 ].…”