The effect of acidity, hydrogen bond catalysis and auxiliary electrode reaction on the oxidation peak current for dopamine, uric acid and tryptophan

Abstract

A pre-anodized inlaying ultra-thin carbon paste electrode on a 316L stainless steel matrix (316L-PAIUCPE) was prepared and used for simultaneous determination of dopamine (DA), uric acid (UA) and tryptophan (Trp). The mechanism by which the acidity affects the size of the oxidation peak currents (i_p) for DA, UA and Trp was discussed with respect to the strength of the hydrogen bonding or electrostatic interactions between DA, UA, Trp and the negatively charged functional groups at the surface of 316L-PAIUCPE, and the reduction reaction at the auxiliary electrode. Under optimized experimental conditions, the oxidation peak currents increased linearly with the concentrations of DA, UA and Trp in the range of 0.4–200, 0.5–150 and 0.1–200 μmol L⁻¹, respectively. The detection limits for DA, UA and Trp were 6.8 × 10⁻⁸, 4.5 × 10⁻⁸, and 5.3 × 10⁻⁸ mol L⁻¹ in PBS buffer solution (pH = 5.00), respectively. This method was successfully used to determine the concentrations of DA, UA, and Trp in different samples.