CONTINUOUSLY RENEWED COPPER ELECTRODE FOR AMPEROMETRIC MEASUREMENT OF CARBOHYDRATES

Abstract

Currently the benchmark method for carbohydrate analysis in a variety of application areas involves anion exchange chromatography followed by electrochemical detection at a gold electrode. The gold electrode surfaces foul from deposition of oxidation products over time; pulsed waveforms with oxidative cleaning and surface reduction are used to improve electrode longevity. After fouling, the electrode needs polishing, or, if using disposable gold electrodes, replacement; both remedies require subsequent recalibration. I describe here a novel electrochemical amperometric detector using a copper electrode that is consumed during the measurement process and a new surface is continuously generated without a change in the electrode distance/placement geometry. A copper wire acts as the working electrode; a stainless-steel tube acts as the counter electrode and also the cell inlet. At the working potential, a thin layer of copper oxide exists at equilibrium on the electrode surface. As carbohydrates contact the working electrode, they are oxidized, and the oxidation products remove the copper oxide by complexation. The oxide layer reforms. The net result is oxidation of the carbohydrate and consumption of the copper electrode. The latter is in the form of a wire and is pushed by a constant pneumatic pressure against the face of the sample inlet tube, the terminus of which is an thin inert insulating polymer ring, separating the working electrode from the counter electrode.