Sensitive electrochemical detection of enzymatically generated thiocholine at carbon nanotube modified glassy carbon electrode

A carbon nanotube modified glassy carbon (CNT/GC) electrode was used for enhancing the sensitivity of electrochemical measurements of enzymatically generated thiocholine. Cyclic voltammetric and amperometric characteristics of thiocholine at CNT/GC, glassy carbon, carbon paste and gold electrodes were compared. The CNT layer leads to a greatly improved anodic detection of enzymatically generated thiocholine product including lower oxidation overpotential (0.15 V) and higher sensitivity because of electrocatalytic activity of edge-plane-like graphite site at the CNT ends, fast electron transfer and big working surface area. The sensor performance was optimized with respect to the operating conditions. Under the optimal batch conditions, a detection limit of 5 x 10(-6) mol/L was obtained with a good precision (RSD = 5.2%, n = 10). Furthermore, the attractive response of thiocholine on CNT/GC electrode has allowed it to be used for constant-potential flow injection analysis. The detection limit was greatly improved to 3 x 10(-7) mol/L. The high sensitive electrochemical detection of enzymatically generated thiocholine with CNT sensing platform holds great promise to prepare acetylcholinesterase biosensor for monitoring organophosphate pesticides and nerve agents. (c) 2005 Elsevier B.V. All rights reserved.