Characterization of White Wines by Electrochemical Indexes Obtained Using Carbon Nanotube-modified Electrodes

In this study, the development of a fast electroanalytical method for the characterization of wines through the evaluation of their phenolic content has been reported. A critical analysis of the influence of some experimental conditions on the efficient dispersion of carbon nanotubes (CNT) in water was carried out. The selected procedure consisted of: 1) 2.0mg CNT were dispersed in 4.0mL of 0.25% (w/v) PEI solution by ultrasonic treatment of 2000-J energy; 2) dispersions were centrifuged at 2500rpm for 20min and sedimented CNT were subsequently washed with pure water; and 3) recovered CNT were re-dispersed in 4.0mL of water by ultrasonic treatment of 2000-J energy. Glassy carbon electrodes modified with CNT films produced from these dispersions showed excellent electrochemical performance for the detection of different polyphenols usually found in wine using flow injection analysis, with good sensitivity, wide linear range and excellent stability. This behaviour allowed the estimation of total polyphenol content in white wines with a remarkable long-term stability in the measurements. In addition, different polyphenols fractions, expressed as electrochemical indexes (EI), can be obtained just by tuning the detection potential. These EI might be employed as characteristic markers of wines related to grape varietal, with potential application for classification purposes as suggested after the analysis of white wines produced using verdejo and airen grapes.