DEVELOPMENT OF ELECTROCHEMICAL DETECTION OF ANTIOXIDANT IN HERBAL PLANTS

Abstract

In this work, graphene/poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) modified screen-printed carbon electrode (G/PEDOT:PSS/SPCE) was developed for the determination of total antioxidant capacity (TAC) via 2,2-diphenyl-1-pycrilhydrazil (DPPH) assay. Initially, the parameters of electrospraying used for electrode fabrication (e.g. amount of PEDOT:PSS loading, amount of G loading, ratio of PEDOT:PSS/G and electrospraying time) were optimized. Then, G/PEDOT:PSS/SPCE was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Cyclic voltammetry (CV) was performed for electrochemical characterization of G/PEDOT:PSS/SPCE using a standard ferricyanide solution. G/PEDOT:PSS/SPCE showed approximately 3 folds higher current response compared to an unmodified SPCE, verifying that this proposed electrode can increase the electrochemical sensitivity of the system. Moreover, the peak potential difference between anodic and cathodic peaks (∆Ep) of G/PEDOT:PSS/SPCE substantially decreased, indicating that the G/PEDOT:PSS nanostructure can accelerate the electron transfer kinetics of the system. For the evaluation of TAC in real samples, chronoamperometry was carried out at a detection potential of 0.20 V. The linearity between Trolox concentration and cathodic current response in a range of 5-30 µM was obtained. Limit of detection (LOD) and limit of quantitation (LOQ) using signal-to-noise ratios of three (S/N=3) and ten (S/N=10) were found to be 0.59 µM and 1.97 µM, respectively. Finally, this system was successfully applied for the determination of TAC in herb and herbal beverages and the results correspond well with a conventional UV-Visible spectroscopic method.