Influence of the HClO4 concentration on the β-CD electropolimerization over a carbon paste electrode and on dopamine's electrochemical response

The present work shows the influence of HClO4 concentration, in the 0.1-2 M range, and of the cycles number applied, namely 5, 10, 15 and 30, during formation of a beta-cyclodextrin, beta-CD, membrane, poly-beta-CD, over a carbon paste electrode, CPE. Also, each of the membranes was assessed in terms of their electrochemical response toward the dopamine, DA, with each modified CPE. In particular it is shown that as the [HClO4] was raised, the anodic and cathodic charges recorded during the poly-beta-CD formation increased, which is a typical response observed during electrochemical formation of a conducting polymer. Furthermore, the greatest poly-beta-CD deposit's amount was obtained for the first cycles from 1 to 5. The analysis of the dopamine's electrochemical response over electrodes that underwent 5 and 15 cycles electropolymerization, as well as with different HClO4 concentrations, revealed that at concentrations below 1 M the overall DA redox process was diffusion-controlled, whereas for a 2 M concentration it changed to be adsorption-controlled, which reflected too an increase of the reactions' heterogeneous velocity constants from 2.16 x 10(-4) cm s(-1) using the bare CPE to 1.4 cm s(-1) obtained when the CPE/poly-beta-CD formed by 15 cycles and in the presence of 2 M HClO4. (C) 2012 Elsevier Ltd. All rights reserved.