Electrocatalytic Discrimination between Dopamine and Norepinephrine at Graphite and Basal Plane HOPG Electrodes

Understanding the regulatory mechanisms of neurotransmission is impossible without invivo monitoring of neurotransmitters' (NTs) transformation in the brain, and that can be performed by a variety of electrochemical methods. Close redox potentials of such NTs as catecholamines, however, impede their specific analysis in systems where they do co-exist. Here, we studied the kinetics of dopamine and norepinephrine redox transformations on glassy carbon, micro-structured spectroscopic graphite, and basal plane HOPG electrodes. We showed that in contrast to the positive electrocatalysis on porous microstructured graphite electrodes, negative electrocatalysis at the HOPG electrodes, displayed through slowing down of the reaction rate, allowed a ca. 0.1V separation between dopamine and norepinephrine oxidations and individual detection of dopamine in the artificial cerebrospinal fluid. Dopamine could be detected within the 50nM to 4M range with no interference from excesses of norepinephrine and ascorbic acid. The results suggest a new approach for design of the electrodes for specific analysis of dopamine in mixtures of structurally related NTs.