Simultaneous/selective detection of dopamine and ascorbic acid at synthetic zeolite-modified/graphite-epoxy composite macro/quasi-microelectrodes

The present paper aims to miniaturize a graphite-epoxy and synthetic
zeolite-modified graphite-epoxy composite macroelectrode as a quasi-microelectrode
aiming in vitro and also, envisaging in vivo simultaneous electrochemical detection of
dopamine (DA) and ascorbic acid (AA) neurotransmitters, or DA detection in the presence
of AA. The electrochemical behavior and the response of the designed materials to the
presence of dopamine and ascorbic acid without any protective membranes were studied by
cyclic voltammetry and constant-potential amperometry techniques. The catalytic effect
towards dopamine detection was proved for the synthetic zeolite-modified graphite-epoxy
composite quasi-microelectrode, allowing increasing the sensitivity and selectivity for this
analyte detection, besides a possible electrostatic attraction between dopamine cation and
the negative surface of the synthetic zeolite and electrostatic repulsion with ascorbic acid
anion. Also, the synthetic zeolite-modified graphite-epoxy composite quasi-microelectrode
gave the best electroanalytical parameters for dopamine detection using constant-potential
amperometry, the most useful technique for practical applications.