Electroanalytical properties of a novel PPY/γcyclodextrin coated electrode

A film of polypyrrole/gamma cyclodextrin (PPY/gamma CD) was synthesized at a gold electrode by the simple electropolymerization of a 1 : 1 mixture of gamma CD and pyrrole monomer in aqueous solutions. Different voltammetric behaviors were obtained between PPY/gamma CD and PPY during the electrosynthesis process. Electrochemical impedance spectroscopy ( EIS) was used to characterize the electrical properties of the electropolymerized films. The PPY/gamma CD films exhibit interesting properties such as a wider potential range for electroanalytical exploration that yields to easier and improved electrochemical detection of neurotransmitters such as dopamine, L-dopa, epinephrine, norepinephrine, and isoproterenol. Well resolved and reversible cyclic voltammograms (CVs) of these organic compounds could be obtained easily at the modified electrode with a negative shift of their oxidation potentials as compared with the response at bare gold electrodes. The plot of the neurotransmitters' catalytic currents vs. their concentrations gave good linear relationship inside the range of 2.10(-6) - 2.10(-5) M with R-2 = 0.998. Detection limits between 6.10(-7) M and 6.10(-6) M were obtained for the molecules studied. According to the CV's scan rate evolution, the electron transfer for the neurotransmitters was mainly diffusion controlled at the polymer-gamma CD/solution interface. Attempts to use the PPY/gamma CD sensor on real human serum for L-dopa exploration yield encouraging data. The preliminary results show that the obtained modified electrode is mechanically stable and features good permselectivity toward interferences such as ascorbic acid at a concentration of more than 500-fold for some neurotransmitters.