Estudo do comportamento eletroquimico de aminas biogenicas na presença de carboxilatos utilizando eletrodo de gota pendente de mercurio

AUTOR(ES)

Eduardo Winter

DATA DE PUBLICAÇÃO

2003

RESUMO

The interest in the redox chemistry of biogenic amines, particularly dopamine (DA), is based on the fact that many of these compounds are directly involved in neurotransmission processes and, consequently, related to neurological disorders, like Parkinson and Alzheimer s diseases. The electrochemical determination of phenolic compounds using solid electrodes presents problems due to the lost of electrode activity during the oxidation processo However, it was verified that EDTA inhibits electrode passivation of the platinum electrode during the oxidation of phenolic compounds, and the DA undergoes oxidation at lower potentials in the presence of the EDTA. The aim of this work was to evaluate the electrochemical behavior of biogenic amines, like dopamine, L-dopa and serotonine in the presence of carboxylic compounds by cyclic voltammetry, using the hanging mercury drop electrode (HMDE), and to establish a possible reaction mechanism. The carboxylic compounds evaluated were citrate, acetate and EDTA. The voltammetric studies comprise the dependence of the anodic and cathodic currents and peak potentials as functions of the pH, concentration of the carboxylic compound and the biogenic amine, scan rate and initial potential of the cathodic scan. The results obtained for the HMDE were compared against the electrochemical behavior of the biogenic amines on the pyrolytic graphite electrode. At potentials above 250 mV, the DA and the Hg are oxidized, in citrate medium, to dopaminoquinone (DQ) and Hg(II). The latter reacts with DA forming DQ, leucodopaminochrome (LDC) and dopaminochrome (DC). The DQ undergoes reduction at 200 mV. The citrate (Cit) stabilizes the DC, which subsequently undergoes reduction at -250 mV and inhibits the formation of polymeric films on the electrode surfaces. This behavior is observed only for the biogenic amines containing a catechol group in their structure.

ASSUNTO(S)

voltametria ciclica doenças neurodegenerativas dopamina

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