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 amperomet ric flow-through detection in alkaline solutions. Experimental conditi ons such as detection mode, pH. copper loading and flow-rate on sensit ivity and stability are evaluated. Constant-potential detection at 0.5 50 V or 0.350 V and pulsed detection modes are tested after anion-exch ange chromatography of alditols, carbohydrates and amino acids. The de tection limits (S/N = 3) of carbohydrates at 0.550 V and 0.350 V range d 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 s ensitivities and detection limits were higher than those obtained in D C mode. Linear dynamic ranges spanned over four (alditols and carbohyd rates) and three (amino acids) orders of magnitude. The Au/Cu CME reta ined 94-96% of its response after several hours operations in flowing streams. As an application, some alditols, carbohydrates and amino aci ds were determined in soluble coffee and red wine. (C) 1998 Elsevier S cience B.V. All rights reserved.