Chronocoulometry of wine on multi-walled carbon nanotube modified electrode: Antioxidant capacity assay

Abstract

© 2015 Elsevier Ltd. All rights reserved. Phenolic antioxidants of wine were electrochemically oxidized on multi-walled carbon nanotubes modified glassy carbon electrode (MWNT/GCE) in phosphate buffer solution. Three oxidation peaks were observed at 0.39, 0.61 and 0.83 V for red dry wine and 0.39, 0.80 and 1.18 V for white dry wine, respectively, using differential pulse voltammetry at pH 4.0. The oxidation potentials for individual phenolic antioxidants confirmed the integral nature of the analytical signals for the wines examined. A one-step chronocoulometric method at 0.83 and 1.18 V for red and white wines, respectively, has been developed for the evaluation of wine antioxidant capacity (AOC). The AOC is expressed in gallic acid equivalents per 1 L of wine. The AOC of white wine was significantly less than red wine (386 ± 112 vs. 1224 ± 184, p < 0.0001), as might be expected. Positive correlations were observed between gallic acid equivalent AOC of wine and total antioxidant capacity, based on coulometric titration with electrogenerated bromine (r = 0.8957 at n = 5 and r = 0.8986 at n = 4 for red and white wines, respectively).