Effect of carboxylate compounds on the electrochemical behavior of dopamine at a mercury electrode

Abstract

A oxidação eletroquímica da dopamina leva à deposição de filmes poliméricos sobre a superfície de eletrodos sólidos, diminuindo a atividade dos mesmos. No eletrodo de mercúrio o processo redox ocorre na região de potencial de oxidação do mercúrio. No entanto, na presença de compostos carboxílicos o voltamograma cíclico da dopamina, no eletrodo de mercúrio, é diferenciado e apresenta um novo produto eletroativo proveniente do processo de oxidação da dopamina. O presente trabalho descreve resultados preliminares sobre o comportamento eletroquímico da dopamina no eletrodo de mercúrio na presença de acetato, citrato e EDTA.The electrochemical oxidation of dopamine leads to deposition of polymeric films on the surfaces of solid state electrodes, decreasing the electrode activity. With a mercury electrode, the oxidation of dopamine occurs in the potential region of mercury oxidation. However, in the presence of carboxylic compounds the cyclic voltammogram of dopamine is different and presents a new electroactive product resulting from the oxidation of dopamine. This work describes preliminary results for the electrochemical behavior of dopamine at the Hg-electrode in the presence of acetate, citrate and EDTA. Keywords: dopamine, electrochemical behavior, carboxylate compounds, mercury electrode IntroductionOver the last 50 years a considerable number of reports about the electrochemical behavior of catecholamines and other biogenic amines has been described in the literature. [1][2][3] Interest in the redox behavior of catecholamines is related to the fact that some of these compounds are directly involved in neurotransmition processes. Several neurological disorders, in particular Parkinson's disease, are associated with improper catecholamine (dopamine) regulation. 4 New research on the pathology and treatment of these diseases requires the development of new analytical methods for dopamine (3,4-dihydroxyphenylethylamine) determination. Dopamine (DA) is an unstable phenolic compound, which undergoes oxidation in neutral or alkaline solutions in the presence of oxygen, with the formation of dopaminochrome and other polymeric compounds. [5][6][7] Several methods have been reported for the determination of dopamine, including spectrophotometry, 8 spectrofluorimetry, 9 radioimmunoassay 10 and high performance liquid chromatography with electrochemical detection. 11 In spite of the electrochemical activity of dopamine, electrochemical methods, due to their high sensitivity, are of special interest in the quantification of DA. 12 However, the electrochemical determination of phenolic compounds presents some problems due to the loss of electrode activity of some solid state electrodes, like platinum, glassy carbon and pyrolytic graphite, during the oxidation process. This electrode inactivation may be explained by the accumulation of reaction products, forming electro-polymerized films on the surface of the electrode. In order to reduce the phenomenon of electrode poisoning, modified electrodes for catecholamine determinat...

Enhanced electrochemical response in oxidative differential pulse voltammetry of dopamine in the presence of ascorbic acid at carboxyl-terminated boron-doped diamond electrodes

“…Otherwise, comparing the properties of the carboxylic groups of the 4PA-BDD surface with those of the carboxylic and hydroxyl groups that are probably present on the O-BDD surface, the electrostatic interactions of these groups with the analytes (DA and AA) should be significantly stronger for 4PA-BDD. These interactions would be expected to lead to sufficient resolution of the DA and AA peaks, with faster electron transfer for DA oxida- [41]. Such a complex is expected to be formed in the case of 4PA, because a PBS solution containing DA and 4PA remained colorless after storage for 3 days in ambient air, while a DA solution without 4PA turned brown within 30 min.…”

The selective electrochemical sensing of dopamine at a polypyrrole film doped with an anionic β−cyclodextrin

“…In this case, the solutions that contain carboxylate groups give rise to lower peak currents, while nearly identical currents are observed with the chloride and sulfateÀcontaining solutions. It is known that the electrochemistry of DA is influenced by the presence of carboxylate anions, and although this is poorly understood, it has been suggested that the carboxylic anions form a product with the DA oxidation species [37]. The MES buffer gives the lowest peak current and this is probably related to the low conductivity of this buffering system.…”

Manganese phthalocyanine as a biomimetic electrocatalyst for phenols in the development of an amperometric sensor

“…Ascorbic acid gave a negative interference (80% in equal molar ratio with dopamine) presumably due to the reaction with hydrogen peroxide, thus this is a serious interferent for direct analysis. To overcome this problem many different strategies have been proposed, such as: the use of a nafion membrane, that repels ascorbic acid and other negatively charged species, 59 the use of the multivariate calibration methods, 60 the addition of ethylenediaminetetraacetate in the supporting electrolyte 61,62 or addition of ascorbate oxidase enzyme. 63 An interference of 62% for molar ratios higher than 150 was observed for sodium bisulfite.…”