NICKEL-CHROMIUM ALLOY ELECTRODE AS A CARBOHYDRATE DETECTOR FOR LIQUID-CHROMATOGRAPHY

A nickel-chromium alloy electrode was applied as an electrochemical detector for the analysis of carbohydrates by high performance anion-exchange liquid chromatography. This alloy electrode exhibited excellent sensitivity, reproducibility and stability. The carbohydrates are oxidatively detected by a surface catalyzed process, proposed to involve nickel(III) oxyhydroxides, which are formed in the range of ca. 0.45 to 0.5 V vs. a Ag/AgCl reference electrode. The cyclic voltammograms of the Ni-Cr electrode are compared to pure Ni in order to understand the basic mechanism of the oxidation. The effects of the temperature, the sodium hydroxide concentration, the mobile phase flow-rate, and the working potential on the electrode response were analyzed to optimize the detection conditions. The reproducibility of the electrode response to the injection of 100 pmol of glucose was studied continuously for a period of 21 days. A limit-of-detection (LOD) of approximately 500 fmol of glucose (signal-to-noise ratio of 3) makes this alloy electrode well suited for the high sensitive detection of carbohydrates