Construction and Analytical Applications of a Si-Gold Strip Enzyme Electrode Using Constant - Current Potentiometry

Abstract

The development and the evaluation of a new Si-gold strip enzyme electrode (SGSEE) with immobilized glucose oxidase (GO) is described. The construction comprised the immobilization of GO in the presence of glutaraldehyde, on a home-made Si-gold strip electrode (SGSE) modified with a self-assembled monolayer (SAM) of 2-aminoethanethiol. A constant-current potentiometric technique was applied for the SGSEE evaluation and the analytical determination of glucose. A constant current of 0.2 μA at 35 V DC was produced across a 270 KΩ resistor and a 184 MΩ resistor, from a simple home-designed electronic circuit. The current was applied between the SGSEE working as cathode and a Pt-anode, in the presence of a SCE. A standard concentration of diphenylamine sulfonic acid (DPASA) in the measured samples was used as potential poiser. The decrease of the Pt-anode potential vs. SCE, due to H2O2 formation, is monitored by a Corning pH/mV meter and displayed on a PC-monitor via a Data Acquisition Card. The slope of the initial part of the analytical signal (E, mV vs. time, sec) is related to the glucose concentration. Different factors concerning the response of the electrochemical system, such as current, reaction volume and DPASA concentration were studied. The effect of pH, temperature, storage time, etc. on the behaviour of the SGSEE was also examined. The designed SGSEE showed good characteristics in a working range of 5.0x10−4 M to 5.00x103 M glucose concentration and usefulness for over one month. The technique was applied successfully for the glucose estimation in samples of serum, foodstuffs and drugs.