Disposable and Sensitive Electrochemical Determination of Isoliquiritigenin in Licorice Using Screen-Printed Carbon Electrode Modified With Multi-Walled Carbon Nanotubes

Herein, a high-sensitive electrochemical sensor based upon a multi-walled carbon nanotubes modified screen-printed carbon electrode (MWCNTs-SPCE) was constructed for the determination of isoliquiritigenin (ISL). The electrochemical properties of ISL on the MWCNTs-SPCE were investigated systematically and a fast and cost-effective method for the determination of ISL was successfully established. A clear irreversible oxidation peak of the ISL was observed at 0.3 V (versus Ag/AgCl) on the MWCNTs-SPCE. The oxidation of ISL on MWCNTs-SPCE was an adsorption reaction accompanied by diffusion. Using differential pulse voltammetry (DPV), we observed that the oxidation peak current of the ISL in phosphate buffer (pH 7) showed a linear relationship from 0.50 to 100 µg/mL and a detection limit of 0.10 µg/mL. This method displayed good repeatability and stability, as well as exhibited excellent selectivity for ISL. Also, we successfully applied the method to determine ISL in Chinese herbal medicine licorice. Validation of the analyses via spike assays showed a recovery rate ranging from 95.39 to 101.00%, which was consistent with high performance liquid chromatography (HPLC).