Rapid Electrochemical Determination of Antioxidant Capacity Using Glassy Carbon Electrodes Modified with Copper and Polyaniline. Application to Ascorbic and Gallic Acids

Abstract

This paper proposes an electrochemical technique for determining antioxidant capacity, AOC, based on the interaction of antioxidants with electrogenerated Cu(II) ions. Cyclic voltammetry is used to detect the electrode surfaces characterized with SEM and EDX. When the electrode is covered by polyaniline, the copper particles are more stable, and the performance of the electrode increases. The interaction in the reaction layer between electrogenerated Cu(II) ions and the antioxidants is fast, with the very low concentration of Cu(II) ions preventing the precipitation of ions with the basic components of the buffer. Consequently, physiological conditions can be used to determine pH close to 7 and the absence of non-aqueous solvents, contrary to what happens in the classic CUPRAC method. The decrease in the peak current corresponding to the reduction of Cu(II) to Cu(I) is used for the AOC determination. The method is tested with well-known antioxidants such as ascorbic and gallic acids.