Complex Multistep Reactions Neurotransmitter Oxidation

Neurotransmitters, such as dopamine (DA) and epinephrine (EP), are catecholamines that undergo complex multistep oxidation processes in aqueous solution via coupled ET, proton transfer (2e , 2H at physiological pH), but with the complication of side reactions to form melanin-like compounds that can block electrode surfaces [193]. Such processes are expected to follow a classical scheme of squares [194], and are of considerable interest for the practical detection of neurotransmitters, as carbon electrodes have become the electroanalytical platform of choice [5, 60, 195]. This is due to a desirable range of properties including biocompatibihty, chemical inertness, and low background current that are responsible for lower detection hmits, wide potential windows, and low 

Recent reappraisals of the electrochemical oxidation of DA and EP on HOPG using macroscale CV, SECCM, and SECM have demonstrated that the longstanding view that graphite edges are solely responsible for catalyzing the 

Ascorbic acid (AA) is an antioxidant, which often coexists with DA under physiological conditions at levels ranging from 200 to 400 pM [199, 200]. The oxidation of AA is irreversible and occurs at potentials close to that of DA and norepinephrine on conventional electrodes, such as Au, Pt, and GC [200-202]. Thus, the development of electrodes that allow the simple and rapid determination of DA with high selectivity and sensitivity is highly desirable for biological diagnostic applications. 

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