ELECTROCHEMICAL-BEHAVIOR OF NI-TI ALLOY ELECTRODE AND ITS APPLICATIONTO THE AMPEROMETRIC DETECTION OF SUGARS

The electrochemical behavior of a Ni-Ti alloy electrode and its applic ation to the amperometric detection of sugars in liquid chromatography are described. In strong basic media, the redox waves of Ni(III)/Ni(I I) were observed at a Ni-Ti alloy electrode near to + 0.5 and + 0.45 V vs. Ag/AgCl, which is very similar to that on a Ni metal electrode. H owever, from the results of the time dependence in voltammetric measur ements, the interconversion of oxide phase (from the alpha-Ni(OH)(2) t o beta-Ni(OH)(2)) was found to be difficult on the Ni-Ti surface. An o xide film on the Ni-Ti electrode surface shows a high catalytic activi ty for the electrochemical oxidation of sugars. It is thus suggested t hat Ti in a Ni-Ti alley stabilized the oxide structure while allowing the electrode to retain the catalytic activity of Ni. Ni-Ti electrode was applied as an electrochemical detector in liquid chromatography fo r the analysis of sugars. At an applied potential of + 0.55 V vs. Ag/A gCl, the linear responses of sugars on the Ni-Ti electrode were found in the range from 0.5 to similar to 500 mu M. For a 10.2 mu 1 sample l oop, the detect:ion limits (S/N greater than or equal to 3) were 0.18 ng (0.1 mu M), 0.36 ng (0.2 mu M), 2.1 ng (0.6 mu M), 2.6 ng (0.7 mu M ) and 2.2 ng (0.6 mu M) for glucose, fructose sucrose, lactose and mal tose, respectively. Since the Ni-Ti alloy electrode exhibited the exce llent long-term stability as compared with other metallic electrodes, it has been confirmed to be a good electrode material for the electroc hemical detection of sugars.