| Capillary Electrophoresis(CE) is one of the most important and rapidly growing separation techniques in recent twenty years,It absorbed the virtues of both the conventional electrophoresis and modem High Performance Liquid Chromatography (HPLC).However,the theoretical plate number is great developed to tens of thousands and even millions and the volume Of sample injection reaches nano milliliter level in CE analysi.In recent years,capillary electrophoresis(CE) has been extensively studied and applied as a highly effective analytical method in modern analysis.And excellent prospects of CE have been shown in the fields of pharmaceutical analysis,biochemical analysis,food analysis,and environmental analysis.It has many advantages such as much lower sampling volume,cheaper instrumentation and higher separation efficiency.However,the small sample injection volume and very thin capillary bring about difficulties to detections.The common used detection methods are Ultra-violet(UV),Laser Induced Fluorescence(LIF), Luminescence Detection,Mass Spectra(MS).Because amperometric detector(AD) is more sensitive than UV-visible detector and much cheaper than LIF detector,it is preferred to couple with CE in many analysis areas.Recently,with more attention paid to the quality of life,the analysis in environment and medicine field has become a hotspot of the analytical chemistry research.The goal of this dissertation is to explore some applications in environmental analysis,pharmaceutical analysis and food analysis etc.by CE-ED. The contents of this dissertation include six chapters:Chapter 1.PrefaceThe characteristics of CE,the separation models,the basic theories of CE,the detectors,the studies and applications of CE-AD are introduced briefly.The goal and significance of this dissertation are also introduced.Chapter 2.Separation and determination of nitroaniline isomers by capillary zone electrophoresis with amperometric detectionCapillary zone electrophoresis with amperometric detection(CZE-AD) was firstly applied to the simultaneous separation and determination of nitroaniline positional isomers.The three analytes could be perfectly analyzed by using the buffer of extreme pH.The effects of several important factors were investigated to find optimum conditions.A carbon-disk electrode was used as working electrode.The optimal conditions were 40 mmol/L tartaric acid-sodium tartrate(pH 1.2) as running buffer, 17 kV as separation voltage and 1.10 V(versus saturated calomel reference electrode, SCE) as detection potential.Under the optimum conditions,o-,m- and p-nitroaniline were separated successfully and good linearity,reproducibility and recovery results were obtained.The detection limit for m-nitroaniline was as low as at 9.06×10-9 mol/L. This proposed method demonstrated long-term stability and reproducibility with relative standard deviations of less than 1.8%for migration time and 1.1%for peak areas.The utility of this method was demonstrated by monitoring dyestuff wastewater and the assay results were satisfactory.Chapter 3.Separation and determination of nitrophenol isomers by capillary electrophoresis with amperometric detectionIn this paper,capillary zone electrophoresis with amperometric detection(CZE-AD) was applied to determine the nitrophenol isomers in dyestuff wastewater.The analytes could be perfectly separated by only adjusting the run buffer with little organic modifier.The effect of certain percentage of organic solvents present in the electrophoretic buffer on the separation of three phenols was investigated.10%(V/V) methanol and the same level of 1:1(V/V) methanol-acetonitrile mixture were found equally effective for sensitivity enhancement in detection and efficiency,but 10%methanol solvent may offer better baseline and peak shapes. The detection limit was as low as 7.50×10-8 mol/L,which was much lower than that in CZE-UV method.Analyzing wastewater by this method has some merits of speed,simple instrumentation and operation,high sensitivity and high reproducibility.The experimental results showed that this CZE-AD method was very practical to determine analogous substances in Environmental Monitoring.Chapter 4.Simultaneous determination of active ingredients in Herba Euphorbiae Humifusae by capillary zone eleetrophoresis with amperometric detectionIn this chapter,the determination of active ingredients(rutin,quercatin,gallic acid and chlorogenic acid) of Euphorbia Humifusa Willd by capillary electrophoresis with amperometric detection were studied.CE-AD was successfully used to separate and detect the five active ingrediences for the first time,and the experiment conditions were optimized.Under the optimum conditions,the analytes could be separated in a 20 mmol/L borate buffer(pH=8.8) within 20 min.A 300μm diameter carbon disk electrode has a good response at +0.95 V(vs.SCE) for all analytes.The response was linear over three orders of magnitude with detection limits(S/N=3).The method could be used in the rapid determination of practical samples.Chapter 5.Determination of bioactive components in Polygonum perfoliatum L.by Capillary Electrophoresis with Electrochemical DetectionThe major bioactive components in a Chinese herb named Polygonum perfoliatum L.including ferulic acid,vanillic acid,quercetin,caffeic acid and protocatechuic acid were simultaneously determined by capillary electrophoresis with electrochemical detection(CE-ED) in this paper.The effects of working electrode potential,pH and concentration of running buffer,separation voltage,and injection time on CE-ED were investigated.Under the optimum conditions,the five analytes could be separated within 17 min at a separation voltage of 18 kV in 10 mmol/L phosphate buffer(pH 9.2).A 300μm diameter carbon disk electrode generated good responses at +0.95V (vs.SCE) for the five analytes.The response was linear over three orders of magnitude with detection limits(S/N=3) ranging from 7.1×10-8 to 9.3×10-8g/mL for the analytes.This proposed method could be successfully applied to the analysis of the real samples with relatively simple extraction procedures,and the assay results were satisfactory.Chapter 6.Separation and Determination ofβ-Agonists in Animal Tissue by Capillary Electrophoresis with Electrochemical Detection.A high-performance capillary electrophoresis with electrochemical detection (CE-ED) method had been applied for the determination ofβ-agonists,Clenbuterol hydrochloride,Terbutaline sulfate,Ractopamine hydrochloride and Salbutamol sulfate,in meat produces.The effects of several factors such as the acidity and concentration of running buffer,the separation voltage,the applied potential and the injection time on CE-ED were investigated.Under the optimum conditions,these four components could be separated successfully at the separation voltage of 17 kV in a 60 mmol/L borax running buffer(pH 8.7).A 300μm diameter carbon disk electrode was used as the working electrode positioned carefully opposite the outlet of the capillary in a wall-jet configuration at potential of +0.95V(vs.SCE).The method had been successfully applied to analyzeβ-agonists in real-life samples,and the assay results were satisfactory.
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