Electrode Modified with Carboxylated Multi-Walled Carbon Nanotubes and Electropolymerized Pyrogallol Red for the Determination of Eugenol

Abstract

Eugenol is the major component of cloves and clove-based products, which are widely used in food, the pharmaceutical industry, and medicine. Its content can be considered a marker of the sample quality. Therefore, simple, sensitive, and reliable methods for eugenol quantification are required. Glassy carbon electrodes (GCEs) modified with carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) and electropolymerized pyrogallol red were developed for the determination of eugenol in essential oils. The working conditions (supporting electrolyte, pH, monomer concentration, and electrolysis parameters) of pyrogallol red were found using voltammetric characteristics of eugenol. The electrodes developed were studied using scanning electron microscopy, voltammetry, and electrochemical impedance spectroscopy. The effectivity of the electrode surface modification was demonstrated. Eugenol determination was performed in differential pulse mode, whose parameters have been optimized. The linear response of the electrodes towards eugenol was obtained in the range of 0.75–100 µM with a detection limit of 0.73 µM. The high selectivity of eugenol determination was observed in the presence of typical inorganic and organic compounds, including essential oils components. The approach developed was tested on commercial clove, cinnamon, and nutmeg essential oils. Validation with the independent method showed similar accuracy and the absence of systematic errors in eugenol determination.

Keywords

• eugenol
• modified electrodes
• electropolymerization
• pyrogallol red
• voltammetry
• essential oils