Simultaneous voltammetric determination of gallic and ellagic acids in cognac and brandy using electrode modified with functionalized SWNT and poly(pyrocatechol violet)

Abstract

© 2019, Springer Science+Business Media, LLC, part of Springer Nature. Voltammetric approach for the simultaneous determination of gallic and ellagic acids using glassy carbon electrode modified with polyaminobenzene sulfonic acid functionalized single-walled carbon nanotubes (f-SWNT) and poly(pyrocatechol violet) (polyPCV/f-SWNT/GCE) has been developed. The electrochemical PCV polymerization has been performed in potentiodynamic mode. The optimization of electrolysis conditions (supporting electrolyte, PCV concentration, polarization window, number of cycles, and potential scan rate) has been performed. The best voltammetric characteristics of gallic and ellagic acids oxidation have been registered on the poly(PCV)-modified electrode obtained by tenfold potential scanning from − 0.2 to 1.1 V at 50 mV s−1 using 50 μmol L−1 PCV in 0.1 mol L−1 H2SO4. The electrode is characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The statistically significant changes in the effective surface area of modified electrodes (38.9 ± 0.6 mm2 for f-SWNT/GCE and 49.0 ± 0.2 mm2 for polyPCV/f-SWNT/GCE vs. 8.2 ± 0.3 mm2 for GCE) have been confirmed. EIS data have shown 2.6-fold decrease of the charge transfer resistance in comparison to GCE. Under conditions of differential pulse voltammetry (DPV), the analytical ranges of 0.75–10 and 10–100 μmol L−1 for gallic acid and 0.75–7.5 and 7.5–100 μmol L−1 for ellagic acid have been obtained. The limits of detection (LOD) and quantification (LOQ) of 0.12 and 0.41 μmol L−1 for gallic acid and 0.11 and 0.37 μmol L−1 for ellagic acid have been achieved. The approach developed has been applied for the simultaneous determination of the gallic and ellagic acids in cognac and brandy. The results obtained agree well to chromatography data.