Ion-exchange voltammetry of dopamine at Nafion-coated glassy carbon electrodes: Quantitative features of ion-exchange partition and reassessment on the oxidation mechanism of dopamine in the presence of excess ascorbic acid

abstract

The incorporation/exclusion features of dopamine (DA), ascorbic acid (AA) and uric acid (UA) are evaluated for Nafion (NA)-coated glassy carbon electrodes (GCE) of different thicknesses. The ion-exchange partition of DA(+) between the NA film and the sodium phosphate electrolyte is evaluated by determining the partition 2 - 1 coefficient (k(D)) and the apparent diffusion coefficient (D-app) in thick NA films which were 401 and 1.5 x 10(-9) cm(2) s(-1), respectively. The solution diffusion coefficient was found to be 6.0 x 10(-6) cm(2) s(-1). Also, the effect of NA loading and of the voltammetric timescale on DA voltammetry in the presence of excess AA is assessed, at physiologic like conditions. It is demonstrated that, although AA is excluded at the NA coating, a catalytic regeneration of DA, induced by AA, occurs at the interface NA film/electrolyte resulting from the diffusion of the o-quinone product of DA oxidation from the electrode surface to that interface. The interference of AA in the voltammetric signal of DA is eliminated using 18 mu g mm(-2) NA films and v >= 0.5 V s(-1). Therefore, fast, selective and sensitive voltammetric analysis of DA at concentrations < 100 mu M in the presence of excess AA, e.g., 1 mM is achieved. (c) 2006 Elsevier B.V. All rights reserved.

keywords

FLOW-INJECTION ANALYSIS; MICROVOLTAMMETRIC ELECTRODES; DIFFUSION-COEFFICIENTS; GOLD ELECTRODE; BRAIN; FILMS; ELECTROANALYSIS; PROSPECTS; SENSORS

subject category

Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Biophysics; Electrochemistry

authors

Rocha, LS; Carapuca, HM

Groups

Share this project:

Related Publications

We use cookies for marketing activities and to offer you a better experience. By clicking “Accept Cookies” you agree with our cookie policy. Read about how we use cookies by clicking "Privacy and Cookie Policy".