Spectroelectrochemical and electrochemical behavior of epinephrine at a gold electrode

Spectroelectrochemical and electrochemical behavior of epinephrine, adrenaline, at a gold electrode was studied with cyclic voltammetric and spectroelectrochemical techniques. Based on the analysis of a series of spectra obtained by in-situ spectroscopic measurements absorption bands of possible intermediates generated in the electrochemical oxidation of adrenaline could be assigned. Also, assignments of various peaks in the cyclicvoltammograms obtained in different pH conditions are not always in agreement with the past findings, especially the formation of dehydrated form of leucoadrenochrome is not likely to occur under acidic conditions. From the analysis of current voltage curves and simultaneously obtained absorption UV-Vis. spectra, it was able to assign the absorption characteristics of species generated. Adrenalinequinone (lambda = 380 nm) is Formed in the first step of oxidation of adrenaline (lambda = 290 nm) followed by cyclization of the quinone product to produce leucoadrenochrome (lambda = 310 nm). The leucoadrenochrome is finally converted into adrenochrome (lambda = 470 similar to 525 nm) chemically or electrochemically. Especially, derivative cyclic voltabsorptograms (DCVA) of a species obtained by measuring absorbance change with potential scans at a selected wavelength provide a new information on the oxidation of adrenaline. (C) 2000 Elsevier Science Ltd. All rights reserved.