Study on the Adsorptive Catalytic Voltammetry of Emodin at a Carbon Paste Electrode

Abstract

An extremely sensitive catalytic voltammetric peak of Emodin at −0.59 V (vs. SCE) was obtained in 0.40 M NH₄Cl–NH₃ · H₂ O buffer (pH 8.2) in the presence of dissolved oxygen at a carbon paste electrode (CPE). The experimental results showed that Emodin was efficiently accumulated at a CPE by adsorption. In the following potential scan, Emodin was reduced to homologous anthrahydroquinone compound, then the compound was immediately oxidized to Emodin by the dissolved oxygen in the solution, and the Emodin was again reduced at the CPE. As a result, a cyclic catalytic reaction was established. At the optimal conditions, the peak current is linearly proportional to the Emodin concentration in the range of 3.0×10⁻¹⁰ M∼4.0×10⁻⁹ M (accumulation 70 s) and 4.0×10⁻⁹ M∼4.0×10⁻⁸ M (accumulation 30 s). The detection limit is 1.0×10⁻¹⁰ M for a 90 s accumulation. The proposed method was successfully applied to determine Emodin in Polygonum multiflorum Thunb. The results are consistent with results obtained by HPLC.

Keywords:

• Emodin
• adsorptive catalytic voltammetry
• carbon paste electrode

This research work was supported by a grant from the Scientific Research Funds of State Key Laboratory of Electroanalytical Chemistry of Changchun Institute of Applied Chemistry, Chinese Academy of Sciences.