“Negative electrocatalysis”-based specific analysis of dopamine at basal plane HOPG in the presence of structurally related catecholamines

Abstract

Oxidations of dopamine and structurally related catecholamines were shown to proceed with the essentially different overpotentials at basal plane HOPG electrodes as compared to glassy carbon electrodes, consistent with the concept of "negative electrocatalysis". Electrode reactions of norepinephrine, epinephrine, and catechol slowed down on HOPG to a higher extent than oxidation of dopamine. Larger overpotentials for norepinephrine, epinephrine, and catechol oxidations allowed analytical discrimination and specific 0.05 to 4 µM detection of dopamine in an artificial cerebrospinal fluid in the presence of 0.5 M ascorbic acid and excessive amounts of norepinephrine, epinephrine and catechol. The results offer a new simple and powerful strategy for designing electrodes for specific analysis of dopamine in biological systems.

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

“…Therewith, the reversibility of NTs oxidation at the HOPG electrode increased, and a redox couple associated with NT oxidation/reduction, not a single oxidation wave, then could be seen in CVs (Figure G, Figure S3). For dopamine, the CV waveform implied two possible processes proceeding at the heterogeneous surface with different reactivity , consistent with earlier observations . It was clear that such differences in electrochemical transformation of NTs should be connected with different electrode surface‐NT interactions and, very likely, with mechanistic aspects of the redox processes.…”

“…We hypothesized that electrochemistry of structurally related catecholamines could also vary on carbon electrodes, and vary in a way different from that of dopamine. Recently shown slowing down of electrode reactions at basal plane HOPG allowed electrochemical discrimination of dopamine from other catecholamines indeed .…”

Surface Heterogeneities Matter in Fast Scan Cyclic Voltammetry Investigations of Catecholamines in Brain with Carbon Microelectrodes of High-Aspect Ratio: Dopamine Oxidation at Conical Carbon Microelectrodes

“…This is rather consistent with the fact that adsorption of catecholamines onto carbon materials is generally assumed to involve supramolecular binding to oxidized carbons moieties, viz., is facilitated at the edges or defects of basal planes, i.e., at areas where electron transfers seem also to be facilitated. 21,[29][30][31][32] The time course required to reach the current peak during one voltammogram is approximately θ ∼ RT /Fv. 63 Thus, during this time duration θ the depletion of the initial DA el ads molecules may be compensated by the progressive migration and subsequent oxidation of a quantity q(θ) = γ * A * × f (θ) of DA non−el ads molecules ( f (θ) is an appropriate kinetic term characteristic of the kinetically-controlled migration process taking place between the randomly dispersed nanodomains structures).…”

“…20 However, this does not seem to be easily generalizable to other types of carbon microelectrodes achieved by different procedures. 21,22 In particular, it is noted that in many recent investigations aimed to monitor quantitatively catecholamine dynamic concentrations by FSCV in living brains, one relies more frequently onto cylindrical [23][24][25][26] or pseudo-cylindrical/conical 27 carbon fibers electrodes whose exposed shafts lengths greatly exceed their diameters (e.g., typically from 50 μm to one -or, possibly, a few -hundred micrometers unsealed shafts vs. 5-7 μm radii). Such high-aspect ratios are generally favored since they allow overcoming the micrometric-scale heterogeneity of synapses distributions in brain areas of interest.…”

Intercalation Lithium Cobalt Oxide for the Facile Fabrication of a Sensitive Dopamine Sensor

“…Various materials have been developed and immobilized on the surface of electrodes, including metal oxides or metal oxide-based nanoparticles and nanocomposites, [9,13,14] carbonbased nanomaterials (i. e. carbon nanotubes, [15,16] graphenes, [17][18][19][20] carbon fibers, [21,22] and HOPG [23,24] et al), polymeric materials [25,26] and ionic liquids [27,28] et al, exploring new materials which may have the adsorptive or catalytic behavior for the electrochemical detection of dopamine is still a trend. In addition, the controlled integration of some nanoparticles creates a class of multifunctional nanomaterials that are powerful for various applications, including in the fields of electrocatalysis and sensing.…”