| Capillary electrophoresis (CE) is one of the fastest developing separation technologies in recent years, but it has its disadvantages due to its small inner diameter, such as poor detection sensitivity. CE incorporating online preconcentration methods has been developed for improving the detection sensitivity. The main content of this dissertation are as follows:1. The basic theory and recent progress of CE was introduced at first, then the reasons for poor detection sensitivity and their corresponding solution methods were discussed. One method was introducing online preconcentration; the other one was using detectors with high sensitivity such as eletrochemical detector. The separation mechanism, affecting factors and application progress of online preconcentration methods including field-amplified sample stacking, isotachophoresis etc. were investigated in details. Finally, multi-dimensional capillary electrophorsis was briefly introduced, which has much higher resolving power and peak capacity than the one-dimensional capillary electrophoresis alone.2. A novel preconcentration / separation approach, which online combined capillary zone electrophoresis (CZE) with cyclodextrin (CD) modified micellar electrokinetic capillary chromatography (MEKC), was developed for simultaneous enhancing resolving power and detection sensitivity. CZE with cation-selective exhaustive injection (CSEI) and transient isotachophoresis (tITP) preconcentration was used as the first dimension. From which the effluent fractions were further analyzed by CD modified MEKC acting as the second dimension. As the key to successful integration of CZE with MEKC, a new interface was designed and electroaccumulation strategy was employed to avoid analyte band diffusion at the interface. Up to 14 000~35 000 fold improvement in sensitivity was obtained comparing to conventional electrokinetic injection method. The limits of detection were in the range of 0.03~0.1μg/L while the numbers of theoretical plates were in the range of 103 000~184 000. This method has been successfully applied to the analysis of trace cationic cardiovascular drugs in wastewater.3. A novel method to detectβ-antagonists in rat blood was developed by combining heart-cutting two-dimensional (2D) capillary electrophoresis (CE) in a single capillary with on-column electrochemical (EC) detection. The blood sample was purified in first dimension by capillary zone electrophoresis (CZE). Then only a desirable fraction of the first dimension separation was transferred into the second dimension of the capillary by pressure. Finally, the purified sample was separated by micellar electrokinetic capillary chromatography (MEKC). After optimizing the analytical conditions, the relative standard deviations of peak height, peak area and migration time were 2.1~4.3%, 1.5~3.9% and 0.7~1.8% (n=10), respectively. This method has been successfully applied to determineβ-antagonists in postdosing rat blood sample. The pharmacokinetic study demonstrated that the proposed heart-cutting 2D-CE with on-column EC detection was convenient, sensitive and would become an attractively alternative method for on-line sample cleanup and separation in complex samples.4. A new electrochemical enzyme-linked immunoassay system of 2-aminopyridine-3-hydroxyl-H2O2-horseradish peroxidase has been developed. AHP was oxidized with H2O2 catalyzed by HRP, and the resulting electroactive product produced a sensitive electrochemical signal at potential of ?0.32 V (vs. SCE) in Britton-Robinson buffer solution. The process of the enzyme-catalyzed reaction and the electro-reduction of the product have been investigated by capillary eletrophorsis in details. The linear range for detection ofα-fetoprotein in human serum ranging from 0.5 to 90 ng/mL with a detection limit of 0.32 ng/mL, which was much lower than that of traditional spectrophotometric enzyme-linked immunosorbent assay (ELISA) method. AHP-H2O2-HRP enzyme-linked immunoassay showed a promising alternative approach in the detection of AFP in clinical diagnosis.
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