Preparation of Glycine Covalently Modified GCE adsorbed with Ni(Ⅱ) and Its Application to Determination of Glucose by Non-enzymatic Oxidation

The pretreated GCE was placed in a solution of 0.01 mol·L-1 glycine in ionic liquid ［Bmin］PF6, and scanned cyclic-voltammetrically at the rate of 50 mV·s-1, in the potential range of 0 to 2.0 V for 10 cycles to prepare the glycine modified GCE (Gly/GCE) through covalent bonding between C and N. The Gly/GCE was then soaked in 0.1 mol·L-1 NiCl2 solution for 6 h to adsorb Ni(Ⅱ) onto the surface of the Gly layer to give the modified electrode of Ni(Ⅱ)-Gly/GCE. In 0.1 mol·L-1 NaOH solution, non-enzymatic oxidation of glucose was observed at this modified electrode due to the mediatory action of the redox half-reaction of Ni2+/Ni3+, leading to significant increase of oxidation peak current at the potential of +0.55 V (vs.SCE). Linear relationship between values of current response and concentration of glucose was obtained in the range of 1×10-6-2×10-3mol·L-1 with the detection limit (3S/N) of 3×10-7mol·L-1. Based on these facts, a chronoamperometric determination of glucose was proposed and applied to the analysis of blood serum samples, giving results in consistency with the results found by the Dimension RXL-MAX automatic biochemical analyzer.