The electrochemical behavior of neurotransmitters at a poly(pyrrole-β-cyclodextrin) modified glassy carbon electrode

A glassy carbon electrode surface was modified with an electropolymerized film made of pyrrole and beta-cyclodextrin 11, in a 0.1 M LiClO4 solution using cyclic voltammetry. The resulting modified electrode (Ppy/beta-CD) exhibits interesting electrocatalytic activity toward the electrochemical oxidation of neurotransmitters such as dopamine (DA) and norepinephrine (NE). Well-resolved and reversible cyclic voltammograms (CVs) were obtained for these organic compounds in a 0.1 M H2SO4 solution. The effect of the pH on the voltammetric response of DA and NE was also investigated inside the range of pH 2.8-8.4. The oxidation current of norepinephrine increase linearly with the concentration inside the range of 4x10(-7) M-2x10(-6) M. The oxidation current of dopamine also followed the same trend range of 2x10(-6) M-10(-5) M. The detection limit was 6x10(-6) M for (DA) and 8x10(-7) M for (NE). As an example, the relative standard deviation for 1x10(-5) M of DA was 2.056%. The diffusion coefficients D for the molecules studied were determined by means of the measurement of the effect of the scan rate on the CVs of the neurotransmitters. All the results showed that the electron transfer was predominantly diffusion controlled at the conducting polymer/solution interface. Interference phenomenon due to ascorbic acid (AA) toward the neurotransmitters was also investigated. The novel modified electrodes presented capability to resolve perfectly the AA and neurotransmitters oxidation peaks. This performance could be achieved even at a concentration 20 times higher than the neurotransmitters. Finally, the newly fabricated Ppy/beta-CD film exhibits interesting analytical performances compared with other systems in the literature, such as higher sensitivity, rapid response, good mechanical stability and reproducibility.