Constant-potential amperometric detector for carbohydrates at a nickel(III) oxide electrode for micro-scale flow-injection analysis and high-performance liquid chromatography.

Abstract A constant-potential amperometric detector for carbohydrates based on oxidation at an active nickel(III) oxide electorde for micro flow-injection analysis (micro-FIA) and micro high-performance liquid chromatography (micro-HPLC) was developed. The active nickel(III) oxide is formed situ on the electrode surface at potentials near ca. 0.5 V vs. Ag/AgCl. The nickel(III) surface acts as a strong oxidant and reacts with the carbohydrate by hydrogen atom abstraction to yield a radical. A tubular-type electrolytic cell was constructed by inserting nickel wire of diameter 25 or 50 μm and length ca. 5 mm into the fused-silica tube (50 or 100 μm I.D.). The effective cell volume was less than ca. 30 nl. The cell was successfully applied to the detection of various sugars such as aldopentoses, aldohexoses, ketohexoses, sugar alcohols, disaccharides and trisaccharides. The detection limit of micro-FIA was 0.1 ng (signal-to-noise ratio = 3) for glucose.