Electroanalytical Oxidation of p‐Coumaric Acid

Abstract

The mechanism of the electrochemical oxidation of p‐coumaric acid on a glassy carbon electrode was investigated using cyclic, differential pulse, and square wave voltammetry at different pHs. The oxidation of p‐coumaric acid is irreversible over the whole pH range. After successive scans, the p‐coumaric acid oxidation product deposits on the electrode surface, forming a polymeric film that undergoes reversible oxidation at a lower potential than p‐coumaric acid. This polymeric film increases in thickness with the number of scans, covering the electrode surface, and impeding the diffusion of the p‐coumaric acid and its oxidation on the electrode. The oxidation of p‐coumaric acid is pH dependent up until values close to the pK_a. For pHs higher than pK_a, the p‐coumaric acid oxidation process is pH independent. An electroanalytical determination procedure of p‐coumaric in pH 8.7 0.2 M ammonium buffer was developed, and a detection limit, LOD=83 nM, and the limit of quantification, LOQ=250 nM, were obtained.

Keywords:

• p‐Coumaric acid
• oxidation
• radical scavenging activity
• hydroxycinnamic acids
• free radicals

Acknowledgments

Financial support from fundação para a Ciência e Tecnologia (FCT), Ph.D. Grant SFRH/BD/28333/2006 (P. Janeiro), POCI 2010 (co‐financed by the European Community Fund FEDER), ICEMS (Research Unit 103), and Ph.D. Grant (I. Novak) from National Foundation for Science, Education and Technological Development of the Republic of Croatia, is gratefully acknowledged.