An Electrochemical Reductive Approach for Selective Determination of Dopamine Based on Its Reverse Voltammetric Preoxidation and Intramolecular Cyclization

In this paper, the cyclic voltammetric behavior of dopamine (DA) was investigated systematically at different potential windows on electrochemical reduce graphene oxide modified glassy carbon electrode, and we found that the electrochemical redox mechanism of DA is a multi-step ECE process and the redox peak appearing at low potentials (--0.30 V) was dependent on the oxidation of DA at high potentials (-0.20 V). The electrolyte enriched with the DA preoxidation product was then analyzed by LC-MS/MS and its structure was identified as dopaminochrome (DC). So, we proposed a new insight for the non-oxidative electrochemical analysis of DA by reverse voltammetry preoxidation and intramolecular cyclization. Compared with the traditional forward scaning mode, the approach could minimize the interference of ascorbic acid (AA) and enable the dual quantitative analysis of DA in the presence of high concentration of AA with the linear range of 2.0 to 80 mu M and 60 to 200 mu M, respectively, and a detection limit of 1.0 mu M. Furthermore, the voltammetric properties of norepinephrine (NE), epinephrine (EP), 3,4-dihydroxy-L-phenylalanine (L-DOPA), 4-O-methyldopamine (HMP) were also investigated. The similar voltammetric properties to DA of NE, EP, L-DOPA and HMP suggested that the proposed reverse voltammetric preoxidation method is generalizable and equally applicable to monoamine neurotransmitters with a catechol structure.