| Capillary electrophoresis (CE), one of the most important separation techniques, has been greatly developed and improved in past two decades. The history, current situation and future trend of capillary electrophoresis are reviewed in this thesis. Capillary electrophoresis is becoming increasingly recognized as an important analytical separation technique due to its speed, efficiency, reproducibility, ultra-small sample volume and ease of clearing up the contaminants. Now it has been widely applied in analytical chemistry, biological chemistry, environmental chemistry, and so on. In combination with electrochemical detection (ED), it offers high sensitivity and good selectivity for electroactive species. In an effort to explore the application of CE-ED, the present dissertation described the studies of capillary electrophoresis with electrochemical detection in the analyses of biological samples, foods and physicalchemistry constant. The major contents are described as follows:1. Study on creatinine and uric acid during aerobic exercises in saliva and urine by capillary electrophoresis with electrochemical detectionA simple and reliable method based on capillary electrophoresis with electrochemical detection (CE-ED) was applied to study the effect of aerobic exercises on creatinine and uric acid concentration in both saliva and urine. The pH value, the running buffer concentration, the SDS concentration, the separation voltage, the injection time and the potential applied to the working electrode were investigated to find the optimum conditions for the determination of creatinine and uric acid in saliva and urine. With a 57cm length of 25μm diameter fused-silica capillary, well-defined separation of creatinine and uric acid from background was achieved in 20 mmol/L borax (pH 9.24) including 70 mmol/L SDS (sodium dodecyl sulfate) within 22 min. The detection limits (S/N=3) for creatinine and uric acid were 3.6μmol/L and 0.86μmol/L, respectively. This method was successfully used in the rapid analysis of creatinine and uric acid in saliva samples for the first time. Notably, after aerobic exercises, creatinine concentration was decreased, and uric acid concentration was increased in saliva. While in urine, the concentrations of creatinine and uric acid were all increased after aerobic exercises.2. Determination of diethylene glycol in toothpaste by capillary electrophoresis with electrochemical detectionA capillary electrophoresis technique with electrochemical detection (CE-ED) for the determination of diethylene glycol (DEG) in toothpaste was described. Effects of several factors, such as the pH value and the concentration of the running buffer, the separation voltage, the injection time and the potential applied to the working electrode, were investigated to find the optimum conditions. With a 75cm length of 25μm diameter fused-silica capillary, well-defined separation of diethylene glycol from propylene glycol and glycerol was achieved in the running buffer. While operated in a wall-jet configuration, a 300μm copper disc electrode used as the working electrode, the applied potential was +0.65V (vs. SCE), the separation voltage was 16 kV, the above three analytes could be well separated in an 80 mmol/1 borate buffer (pH =9.2). The linear range of DEG was from 8.4×10-4 g/mL to 4.2×10-6 ml/mL. Notably, the DEG detection limit (S/N=3) of 1.5×10-6 g/mL could meet the safety criterion of this compound. This method was successfully used in the rapid analysis of DEG in several toothpaste samples. The average recoveries of 96.9%-102.9% indicated that the experimental results were satisfactory.3. Determination of 3-chloro-l,2-propanediol in soy sauces by capillary electrophoresis with electrochemical detectionA capillary electrophoresis technique with electrochemical detection (CE-ED) for determination of 3-chloro-1, 2-propanediol (3-MCPD) in soy sauces was described. Effects of several factors, such as the pH value and the concentration of the running buffer, the separation voltage, the injection time and the potential applied to the working electrode, were investigated to find the optimum conditions. With a 25μm diameter fused-silica capillary, well-defined separation of 3-chloro-l, 2-propanediol from propanediol and glycerol was achieved in 30 mmol/L borax (pH 9.24) within 13 min. Operated in a wall-jet configuration, a 450 urn copper-disk electrode used as the working electrode exhibits good response at +0.65 V (vs. SCE) for the analyte in 0.05 mol/1 sodium hydroxide solution. The linear range of 3-MCPD was from 2×10-4 g/mL to 6.6×10-6 g/mL. Notably, the 3-MCPD detection limit (S/N=3) of 1.3×10-7 g/mL could meet the criterion of food safety. This method was successfully used in the rapid analysis of 3-MCPD in soy samples. The average recoveries of 93.8%-107.7% indicated that the experimental results were satisfactory.4. Determination ofβ-adenergic agonist in pig urine and pig fodder by small-sized capillary electrophoresis with electrochemical detectionA method of small-sized capillary electrophoresis with electrochemical detection has been developed for the determination ofβ-adenergic agonists in pig urine and pig fodder. Several important factors including the running buffer acidity, the separation voltage, the working electrode potential and etc, were evaluated to acquire optimum analysis conditions. Under the selected optimum conditions, these analytes can be well separated in 7 minute. Good linear relationship was established between the peak current and the concentration of each analyte over 3 orders of magnitude. And the analytes detection limit (S/N=3) were 2.06×10-7 g/mL, 1.20×10-7 g/mL and 1.50×10-7 g/mL, respectively. The proposed method has been successfully applied for the determination ofβ-adenergic agonist in pig urine and pig fodder with satisfactory results, providing a useful monitoring method for food safety.5. Determination of active components in bamboo leaves and bamboo-leaf products by capillary electrophoresis with electrochemical detectionA simultaneous determination of vanillin, trans-ferulic acid, p-hydroxybenzaldehyde, p-coumaric acid, vanillic acid, 4-hydroxybenzoic acid and caffeic acid in five different kinds of bamboo leaves and bamboo-leaf products such as bamboo-leaf tea and bamboo-leaf liquor by capillary zone electrophoresis with electrochemical detection (CE—ED) was reported. The effects of several important factors were investigated to acquire the optimum analysis conditions. A 300μm diameter carbon disc electrode was used as the working electrode positioned carefully opposite the outlet of capillary at potential of +0.95 V (vs. SCE). The analytes could be well separated within 22 min at a separation voltage of 16 kV in a 60 mmol/L borate buffer (pH=8.7). There is excellent linearity between peak current and concentration of seven analytes over two or three orders of magnitude with the detection limits (S/N=3) ranging from 1.9×10-8g/mL to 9.8×10-8 g/mL. The proposed method has been successfully applied to the analysis of real samples with satisfactory results.6. Determination of pKa values of salicyl alcohol and phenol by capillary electrophoresis with amperometric detectionA simple and rapid method based on capillary electrophoresis with amperometric detection (CE-ED) to calculate the dissociation constant of salicyl alcohol and phenol is described. The effects of several factors, such as the potential applied to the working electrode, the injection time, and the separation voltage, were investigated to find the optimum conditions for pKa determination. Operating in a wall-jet configuration, a 300μm carbon disk electrode used as the working electrode exhibited good response at +0.86 V (vs. SCE) for salicyl alcohol and phenol. The effective mobilities of salicyl alcohol at different temperatures were determined by monitoring the migration time changes of salicyl alcohol and phenol. The dissociation constants of salicyl alcohol and phenol were calculated to be 9.94 and 9.96, respectively, which are in good agreement with the literature.
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