Electrochemistry of White Wine Polyphenols Using PEDOT Modified Electrodes

Abstract

Abstract:The conducting polymer PEDOT (poly-3,4-ethylenedioxythiophene) has been polymerized onto 3 mm and 10 µm electrodes from a propylene carbonate solution. The electrodes have then been tested in a Chardonnay wine, including dilutions in a model wine solution, with comparisons made to scans with a glassy carbon electrode. A well-defined oxidation peak was obtained for the white wine at PEDOT in the 400 to 450 mV (Ag/AgCl) range, where peaks were also obtained for the representative phenolics caffeic acid and catechin. The voltammetry at PEDOT was typical of a surface-confined process. Significant preconcentration, leading to an increased current response, was noted over a period of 20 min of holding time. Extensive PEDOT growth was observed in the microelectrode case, leading to current densities for the oxidation of caffeic acid over 1000 times greater than those observed at the macroelectrode, matching the high surface area and fractal-type growth observed in SEM images.

Electrochemical Study of Gold Microelectrodes Modified with PEDOT to Quantify Uric Acid in Milk Samples

“…The overall diameter was c. 40 μm, made up of aggregated polymeric nanoparticles with many pores in between, resulting in a larger active electrochemical surface area (Figure 2c & 2d). This structure is consistent with a previous report on SEM images of the PEDOT growth on a gold microelectrode, which after eight polymerization cycles displayed a large irregular cauliflower shape extending at least 50 μm out from the microelectrode [31]. By contrast, images associated with the PEDOT polymerization in the aqueous acetonitrile solution showed less growth of the polymer after 4 cycles, seen as a very thin and rough surface with c. 20 μm diameter (Figure 2e & 2 f).…”

“…The current density of the PEDOT in propylene carbonate on the gold microelectrode at 1.2 V for the 4 th cycle was about 3694 mA/cm 2 , which is about 1500 times higher than the current density for PEDOT formation observed in propylene carbonate at a 3 mm glassy carbon macroelectrode (2.5 mA/cm 2 ) at the same potential [29]. This points to a very high surface area for the PEDOT formed on the gold microelectrode and is consistent with previous reports that it forms a hemispherical cauliflower-shaped structure at the microelectrode surface [31].…”

“…Synthesis of PEDOT by electropolymerization of EDOT was also undertaken in an aqueous electrolyte solution consisting of 1 mL of 0.01 M EDOT dissolved in acetonitrile (ACN) and 9 mL deionized water with 0.1 M LiClO 4 . This 10 % (v/v) acetonitrile/ water aqueous medium has been used in previous research on PEDOT electrochemical macrosensors [30,31], and also differs in having a 10-fold lower EDOT concentration than that used with propylene carbonate, due to the lower solubility of EDOT in the acetonitrile/ water mixture. However, the PEDOT structure preparation in propylene carbonate with a higher EDOT concentration and fewer polymerization cycles on a glassy carbon macroelectrode (1 mm dia.)…”

Electrochemical Sensors Coupled with Multivariate Statistical Analysis as Screening Tools for Wine Authentication Issues: A Review

“…Most often, electroanalytical techniques in wine analysis are used for: (1) the direct evaluation of antioxidant activity and total polyphenol content of wines [40][41][42][43]; (2) the detection and the quantification of individual polyphenols in wines [40,44,45]; and (3) the monitoring of alcoholic and malolactic fermentation [42], as well as monitoring grape ripening [46,47].…”

Phenolic Compounds in Fruit Beverages

“…paper from Zhang et al [5] studied the application of poly-3,4-ethylenedioxythiophene (PEDOT) electrodes for the characterization of polyphenols in white wines. In that case, a Chardonnay white wine was used.…”