Electrochemical oxidation of dopamine and ascorbic acid at a palladium electrode modified with in situ fabricated iodine-adlayer in alkaline solution

The self-assembled iodine-adlayer was fabricated at the palladium (Pd) electrode surface throughout a spontaneous oxidative chemisorption of iodide ions contained in an alkaline supporting electrolyte. It enhances the electron transfer kinetics for the oxidation of dopamine (DA) and ascorbic acid (AA) and was important to separate the peak current of both species with a practical potential difference compared with that occurred at the unmodified electrode. The anodic peak currents of both species were linearly increased with their respective concentrations using linear square stripping voltammetry. The activity of the electrode system was further investigated applying chronoamperometry method. The steady-state amperometric signal for the oxidation of DA in the presence of iodide ions was five times greater than that in its absence. The current-time response was also used to evaluate the diffusion coefficient of DA based on Cottrell plot that results with a value of 4.19 × 10^-8 m² s^-1. The proposed method was successfully applied to detect DA and AA in human serum.