Adsorption effects during the analysis of caffeic acid at PEDOT electrodes

Polyphenol compounds, such as caffeic acid, are important substrates of oxidation in beverages such as wine, and more rapid and sensitive methods of analysis are being sought. The conducting polymer poly-3,4-ethylenedioxythiophene (PEDOT) provides good separation of caffeic acid from antioxidant additives in wines, and produces a clear anodic peak that can be used to quantify caffeic acid and related hydroxycinnamic acids. Various adsorption effects are examined in this report, as shown through electrochemical tests such as sweep rate dependence of the anodic peak current and voltammetric shape. The importance of a controlled holding time prior to measurement is seen, owing to the gradual increase in anodic peak current over a period of 10–20 min, with implications for the design of a measurement system involving PEDOT electrodes.