A strategy for the determination of dopamine at a bare glassy carbon electrode: p-Phenylenediamine as a nucleophile

Electrochemical oxidation of dopamine (DA) in the presence of p-phenylenediamine (PPD) as a nucleophile in aqueous buffered solutions was studied. The results indicate that the o-dopaminoquinone (o-DQ) electrochemically derived from DA participates in 1,4-Michael addition with PPD to form the corresponding new derivative (P2), which is present as the oxidized state (Q2) at the electrolysis applied potential. This reaction pathway inhibits the cyclization of o-DQ and thus, the formation of polymerized films on the electrode surface. The reduction current for Q2 to P2 can be used to determine DA concentration. A selective sensing and quantitative determination of DA by adding PPD and using a bare glassy carbon electrode in the presence of a high concentration of ascorbic acid was verified.