Carbon Nanotubes Modified Electrode And It's Applications In Capillary Electrophoresis

Carbon nanotubes (CNTs) have led to many new technical developments and applications such as being used for the modified electrodes due to their high chemical stability, high surface area, unique electronic properties, and relatively high mechanical strength. Such properties of carbon nanotubes make them also extremely attractive for the task of electrochemical detection. CNTs-modified electrodes have been shown useful for improving the electrochemical behavior of important analytes. Higher sensitivity and stability have thus been demonstrated in voltammetric analysis. Capillary electrophoresis (CE) with electrochemical detection (ECD) has already been applied to analyse many substances owing to its inherent high sensitivity, simplicity of instrumention needed, short analysis time, efficient separation capabilities, and minute consumption of sample. When CNTs-modified microelectrodes are used as detector of CE, the kinds of substance determined will increase greatly and the sensitivity and selectivity will enhance laargely.In this thesis, we develop a method to make a novel glucose biosensor, the concentration of glucose in human serum successfully. A simple and convenient method of H2O2 determination was developed by CE- ECD.In the first chapter, The carbon nanotubes modified electrode and its applications in the food chemistry, biologic chemistry, medicine chemistry, environmental chemistry test and capillary electrophoresis are reviewed. We mainly summarized the analytical applications and progresses of carbon nanotubes in chemical modified electrodes and electrochemical biosensors.In the second chapter, a new amperometric biosensor for the quantitative measurement of glucose was reported. The biosensor was based on the immobilization of single walled carbon nanotubes(SWNTs)–glucose oxidase–chitosan biocomposite at platinized Au electrode. The effect of Pt deposit time, the content of SWNTs and GOx, pH of the buffer and the operating potential was studied. The production mechanism was discussed. The experimental result illustrated that the biosensor has the properties of good reproducibility and stability, high sensitivity and rapid response to the determination of glucose. The experiment also showed that there was no interference from the electro-active interfering species such as ascorbic acid and uric acid when they are at endogenous level in serum. The biosensor was successfully used to detect the glucose in serum rapidly and accurately. The existence of SWNTs increased the number of glucose oxidase and the speed of electron delivery in biomembrane.In the third chapter, we made a kind of Au microelectrode and developed a novel method for the determination of glucose in human serum based on capillary electrophoresis coupled with novel glucose biosensor which was homemade and based on the immobilization of SWNTs–glucose oxidase–chitosan biocomposite at platinized Au electrode by one-step electrodeposition according to the method reported in the second chapter. Factors influencing the performance, including separation voltage, detection potential, pH value and the concentration of the buffer were studied. The biosensor exhibited good stability and durability in the analytical procedures. Finally, glucose in human serum from two healthy individuals and two diabetics was successfully determined. It proved that the method can be applied to the determination of glucose in human blood using CE-ECD. The reason of its good reproducibility and durability is probably that the immobilized enzyme was firmly retained on the biosensor surface as a result of the presense of chitosan and Nafion.In the fourth chapter, a method using capillary electrophoresis with amperometric detection was developed for the determination of hydrogen peroxide. Gold microelectrode and ionic liquid modified-SWNTs paste microelectrode made by ourselves were used as the detector of capillary zone electrophoresis with electrochemical end-column amperometric detection to determine hydrogen peroxide. Gold microelectrode showed higher sensitivity to H2O2 was used as the detector of capillary electrophoresis. Factors influencing the performance, including separation voltage, detection potential and pH value of the buffer were studied. Because of the higher sensitivity of this method, it was hopeful to determinate the concentration of H2O2 in single cell.