Applications of a copper-modified gold electrode for amperometric detection of polar aliphatic compounds by anion-exchange chromatography

An Au/Cu bimetallic electrode is investigated as a sensor in amperometric flow-through detection in alkaline solutions. Experimental conditions such as detection mode, pH. copper loading and flow-rate on sensitivity and stability are evaluated. Constant-potential detection at 0.550 V or 0.350 V and pulsed detection modes are tested after anion-exchange chromatography of alditols, carbohydrates and amino acids. The detection limits (S/N = 3) of carbohydrates at 0.550 V and 0.350 V ranged between 4.6-9.0 pmol and 1.0-4.0 pmol, respectively. Those of amino acids were 9.0-39 pmol. in pulsed amperometric detection mode, molar sensitivities and detection limits were higher than those obtained in DC mode. Linear dynamic ranges spanned over four (alditols and carbohydrates) and three (amino acids) orders of magnitude. The Au/Cu CME retained 94-96% of its response after several hours operations in flowing streams. As an application, some alditols, carbohydrates and amino acids were determined in soluble coffee and red wine. (C) 1998 Elsevier Science B.V. All rights reserved.