Capillary electrophoresis with constant potential amperometric detection using a nickel microelectrode for detection of carbohydrates

Carbohydrates were separated by capillary electrophoresis (CE) and detected electrochemically using a nickel microelectrode which was operated at a constant applied potential (similar to 0.6 V vs. Ag/AgCl). A simple capillary electrode holder design facilitated alignment between the separation capillary and the working microelectrode without the use of micro-positioning equipment. The separations were performed under alkaline conditions (pH > 11), matching the high pH requirements for amperometric detection at the nickel electrode. The analytical procedure developed showed detection limits for the carbohydrates studied in the micromolar range, showing a linear response in the range tested (micromolar to millimolar). The procedure was used to identify sugars in two real samples (i.e., urine and in a common beverage). The potential use of the system for the determination of amino acids was also demonstrated.