# Application of a Carbon Fiber Microelectrode as a Sensor for Apocynin Electroanalysis

## TL;DR

This study introduces a new method using a carbon fiber microelectrode to detect and measure the antioxidant apocynin in supplements and herbal extracts.

## Contribution

The first voltammetric method for apocynin determination using a carbon fiber microelectrode is developed.

## Key findings

- APO's anodic oxidation is diffusion-controlled with a two-electron and one proton exchange.
- The DPV method achieved a linear response for APO concentrations from 2.7 × 10−6 to 2.6 × 10−4 mol L−1.
- The method successfully detected APO in herbal extracts and dietary supplements.

## Abstract

In this study, a carbon fiber microelectrode (CF) was applied for the investigation of the electrochemical behavior of the natural antioxidant, apocynin (APO). Given the limited solubility of APO in water, a mixture of anhydrous acetic acid (AcH) with 20%, v/v acetonitrile (AN) and 0.1 mol L−1 sodium acetate (AcNa) was used. The electrochemical properties of APO were examined through linear sweep voltammetry (LSV), differential pulse voltammetry (DPV), and cyclic voltammetry (CV). The anodic oxidation of APO, which is the basis of the method used, proved to be diffusion-controlled and proceeded with a two-electron and one proton exchange. Both radicals and radical cations, arising from the first and second step of electrode reactions, respectively, underwent subsequent chemical transformations to yield more stable final products (EqCiEiCi mechanism). Using optimized DPV conditions, the anodic peak current of APO at a potential of 0.925 V vs. Ag/AgCl showed a good linear response within the concentration range of 2.7 × 10−6–2.6 × 10−4 mol L−1. The detection and quantification limits were determined as 8.9 × 10−7 and 2.7 × 10−6 mol L−1, respectively. The developed DPV method enabled the successful determination of APO in herbal extracts and in dietary supplements. It should be noted that this is the first method to be used for voltammetric determination of APO.