Determination of 3, 4-dihydroxybenzoic acid by electrocatalytic oxidation at an ionic liquid modified electrode

An electrode modified with an ionic liquid was used for the electrochemical determination of 3,4-dihydroxybenzoic acid (DHBA). Cyclic voltammetry indicated a pair of well-defined quasi-reversible redox peaks with a formal peak potential located at 586 mV (vs. the SCE). The voltammetric response to DHBA is largely improved compared to a traditional carbon paste electrode. This is attributed to a larger interface (due to the presence of an ionic liquid) with higher conductivity and inherent catalytic capability. The charge transfer coefficient, the standard rate constant and the apparent diffusion coefficient were calculated. The oxidation peak current was linearly related to the concentration of DHBA in the range 0.8-1.5 mM, and the detection limit was 0.62 A mu M (at 3 sigma). The effect of potential interferents was investigated, and the method was successfully applied to the determination of DHBA in different samples.