Electrochemical Characterization of Epigallocatechin Gallate Using Square‐Wave Voltammetry

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Abstract
Electrochemical oxidation of (−)‐epigallocatechin gallate (EGCG), the main monomer flavanol found in green tea, has been investigated over a wide pH range at a glassy‐carbon electrode using square‐wave voltammetry (SWV). Square‐wave voltammograms of (−)‐epigallocatechin (EGC) and gallic acid have been studied as well. The I–E profile of EGCG, i.e. the oxidation potentials and the current responses of the first and the second peak, is pH dependent. The oxidation of EGCG is a quasireversible process over the studied pH range, which was also confirmed by the non‐linear relationship between the peak currents and squre root of frequency. The best SWV responses for EGCG were obtained at pH 2.0, frequency of 100 Hz, step of 2 mV and amplitude of 50 mV. Under these conditions, linear responses for EGCG were obtained for concentrations from 1×10−7 M to 1×10−6 M, and calculated LOD and LOQ for the first oxidation peak were 6.59×10−8 M and 2.19×10−7 M, respectively. The proposed electroanalytical procedure was applied for the determination of EGCG content in green tea. Developed SWV methodology represents a potential analytical tool in determination of catechins in tea samples.

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