Supramolecular interaction of dopamine with β-cyclodextrin: An experimental and theoretical electrochemical study

This work presents the construction of a supramolecular system formed by the surface modification of carbon paste electrodes (CPE) with a novel conducting polymer produced by electrochemical polymerization of β-cyclodextrin, β-CD, (CPE/poly-β-CD). With the bare CPE and the modified-CPE, an electrochemical study was performed to understand the effect of such surface modification on the dopamine’s (DA) electrochemical response. From this study it is shown that on the modified-CPE, the DA was surface-immobilized through formation of an inclusion complex with β-CD, which provokes the adsorption of DA, within the outermost molecular layer of the CPE/poly-β-CD, in such a way that this stage becomes the limiting step for the DA electrochemical oxidation. It is shown that the DA’s oxidation heterogeneous rate constant, k0, is highly increased in the presence of poly-β-CD. From the analysis of the experimental voltammetric plots recorded during DA oxidation and reduction on the CPE/poly-β-CD electrode surfaces, the Gibbs’ standard free energy change of the inclusion complex formed by the oxidation product of DA, dopamine semiquinone, and β-CD has been determined for the first time, Δ G inclus . 0 = −26.1 kJ mol−1. Furthermore, this modified electrode was used as working electrode during the electrochemical determination of DA, in the presence of ascorbic acid at pH 3.0. The ability of this new sensor electrode towards DA detection in real samples was tested with satisfactory results showing a 99% recovery.