An Electrode Based on Electropolymerized Sunset Yellow for the Simultaneous Voltammetric Determination of Chlorogenic and Ferulic Acids

Abstract

Abstract: We developed an electrode based on multi-walled carbon nanotubes and electropolymerized Sunset Yellow FCF for the simultaneous voltammetric determination of chlorogenic and ferulic acids. Poly(Sunset Yellow) was obtained potentiostatically under chronoamperometric conditions. Variation of the pH of the supporting electrolyte, monomer concentration, and electrolysis conditions showed that the maximum difference between the oxidation potentials of phenolic acids (190 mV) and high currents were achieved for a coating obtained in an alkaline medium from 50 μM monomer solution at a potential of 1.1 V for 30 s. Poly(Sunset Yellow) consists of spherical particles and their aggregates with a diameter of 26–75 nm, which leads to an increase in the effective surface area of the electrode (44.0 ± 0.6 mm2 compared to 26.1 ± 0.6 mm2 for a glassy carbon electrode modified with carbon nanotubes). The data of electrochemical impedance spectroscopy indicate an increase in the rate of electron transfer on modified electrodes. The data of cyclic voltammetry proved that the electrooxidation of phenolic acids on the polymer-modified electrode is controlled by diffusion and proceeds with the participation of two electrons and two protons with the formation of corresponding o-quinones. The linear dynamic range is 0.10–4.0 µM for chlorogenic acid and 0.5–4.0 µM for ferulic acid with the limits of detection 0.076 and 0.098 µM, respectively. The proposed method was applied to determine these acids in coffee.