Electrocatalytic oxidation and selective detection of dopamine at a 5,5-ditetradecyl-2-(2-trimethyl-ammonioethyl)-1,3-dioxane bromide self-assembled bilayer membrane modified glassy carbon electrode

An easily constructed, highly sensitive, rapidly responding, stable, and reproducible self-assembled lipid bilayer membrane (BLM) modified glassy carbon electrode (DTDB-BLM/GCE) was developed by using a newly synthesized compound containing dioxane, 5,5-ditetradecyl-2(2-trimethyl-ammonioethyl)-1,3-dioxane bromide (DTDB). The fabrication and characterization of this modified electrode and its primary application for dopamine (DA) determination are described in detail. The DTDB-BLM/GCE showed a strong electrocatalytic activity toward the oxidation of dopamine (DA) at E-p = 0.20V versus SCE. It also showed electrocatalytic activity toward the oxidation of ascorbic acid (AA), however, with a strong electric repelling effect toward AA, which leads to AA oxidation at E-p of about 0.1 V with a small current response. Hence, the determination of DA could be achieved even in the presence of 1000-times higher concentration of AA. Differential pulse voltammetry (DPV) gave a linear current response for DA from 10(-8) to 10(-4) M. A wide linear response range of 5 x 10(-10) to 5 x 10(-4) M DA was achieved by using flow injection in combination with electrochemical detection (FIA-ECD) in a thin-layer cell equipped with this electrode. It was shown that the DA oxidation was affected by adsorption process, and the AA oxidation was controlled by diffusion through the pinholes on the BLM. Comparative experiments were performed at the electrodes modified with either dimethyldioctadecylammonium bromide (DMDOB) or didodecylmethylammonium bromide (DDAB), which showed that the 1,3-dioxane group in the lipid molecule played a dominant role in the electrode performance. (C) 2003 Elsevier B.V. All rights reserved.