Copper nanoparticles-modified carbon paste transducer as a biosensor for determination of acetylcholine

The electrocatalytic oxidation of acetylcholine (Ach) on two different copper-based transducers, copper microparticles-modified carbon paste electrode (m-CPE) and copper nanoparticles-modified carbon paste electrode (n-CPE), was investigated. In the voltammograms recorded using m-CPE, a single anodic oxidation peak related to the oxidation of ACh was appeared which was related to the electrocatalytic oxidation of ACh via the electrogenerated Cu(III) species in an EC' mechanism. Using n-CPE, however, two overlapped anodic peaks appeared which were related to two fine tunable steps of oxidation. ACh oxidized on n-CPE with higher rates at low potentials with respect to m-CPE. The kinetic of the reaction was formulated and the charge-transfer resistance of the system was obtained both theoretically and experimentally. The catalytic rate constant, the transfer coefficient for the electrocatalytic oxidation and the diffusion coefficients for ACh were reported using chronoamperometry, pseudo-steady-state polarization measurement and electrochemical impedance spectroscopy. Sensitive and time-saving sensing procedures in both batch and flow systems were developed for the analysis of ACh, and the corresponding analytical parameters were reported.