| 1. PrefaceCapillary electrophoresis (CE) is a new and rapidly developing separation technology which is in buffer-filled, narrow-bore capillaries, with a high-voltage power supply providing electric field; separation by electrophoresis relies on differences of characteristics of charged species. It has the characteristics of high efficiency, high speed, ultra-small sample volume, and high degree of automation. Nowadays, CE has been used to separate protein, ammo acid, inorganic ions, organic compounds, separation and determination of pharmaceutical compounds. It has been widely applied in food chemistry, medicine chemistry, analytical chemistry, clinical chemistry, environmental chemistry, and so on. In this part, the history of CE development has been retrieved, and the principle, the separation modes, the instrumental system, the technological characteristics of CE, in particular the method of capillary chromatography with amperometric detection (CE-AD) and capillary chromatography with capacitively coupled contactless conductivity detection (CE-C4D) have been introduced. According to the research area of this thesis, the application of CE in food and traditional Chinese medicine analysis has been reviewed. In this thesis,CE-AD and CE-C D has been used separately in the determination of biogenic amines in water matrix. CE has also been applied for the study on the valeriana medicinal plants. This method would find wide application in the fields of food and traditional Chinese medicine analysis.2. Study on electrochemical profiles of valeriana medicinal plants by capillary electrophoresisA method based on amperometric detection with capillary electrophoresis has been employed for the separation and determination of pharmacologically active ingredients in extracts of Valeriana medicinal plants, including acacetin, diosmetin, chlorogenic acid, kaempferol, apigenin, luteolin, p-hydroxybenzoic and caffeic acids. The method was validated for linearity, repeatability, limits of detection (LOD) and limits of quantification (LOQ), etc. The LODs and LOQs of eight compounds were found to be in the range from1.0×10-8to1.2×10-7and3.3×10-8to4.0×10-7g/mL,respectively. The proposed method was successfully applied for the analyses and comparison of bioactive components in Valerian samples after a relatively simple extraction procedure, and the resultant "electrochemical profiles" can intuitively demonstrate the content diversity of each electrochemically active ingredient in Valerian samples from different places and plant parts. It was found the content of bioactive ingredients may vary by an order of magnitude depending on natural conditions, e.g. soil, climate, humidity etc. This method has been successfully used in the analysis of pharmacologically active ingredients of Valeriana medicinal plants, which provided an alternative for the analysis of traditional Chinese medicine.3. Determination of biogenic amines in water matrix by zone electrophoresis with amperometric detectionA high-performance18-crown-6modified capillary zone electrophoresis with amperometric detection (CZE-AD)method is developed for the fast determination of seven biogenic amines (BAs), including spermine (Spm), spermidine (Spd), histamine (His), cadaverine (Cad), β-phenylethylamine (Phe), tyramine (Tyr) and tryptamine (Try). The effects of several important factors such as the acidity and concentration of running buffer, separation voltage, injection time and detection potential were investigated to acquire the optimum conditions. A copper disc electrode was used as the working electrode positioned carefully opposite the outlet of capillary at potential of+650mV (vs SCE). Under the optimum conditions, seven BAs could be well separated within29min at the separation voltage of14kV in a180mmol/L18-crown-6/20mmol/L acetate buffer solution (pH3.6). Extrapolated limits of detection for seven BAs were low to10ng/mL for the standard mixture. Repeatability of the peak current (<4.8%) and migration time (≤2.4%) of analytes for the method were achieved. The main advantages of the proposed CZE-AD method are no preconcentration and derivatization procedure, which provides an alternative method for the quantitative multi-analysis of BAs in real water matrix.4. Determination of biogenic amines in water matrix and wines by zone electrophoresis with capacitively coupled contactless conductivity detectionA high performance capillary zone electrophoresis with capacitively coupled contactless conductivity detection (CZE-C4D) method has been developed for the separation and sensitive determination of the eight biogenic amines, including Spermine (Spm), spermidine (Spd), histamine (His), putrescine(Put), cadaver (Cad), β-phenylethylamine (Phe), tyramine (Tyr) and tryptamine (Try).The effects of several important factors such as excitation voltage and frequency, the acidity and concentration of running buffer, separation voltage, and injection time were investigated to acquire the optimum conditions. Under the optimum conditions, BAs can be well separated within24min at the separation voltage of16kV in a150mmol/L18-crown-6/500mmol/L acetic acid solution and excitation voltage and frequency of60V and550KHz. Good linear relationships were established between the concentration and peak area of analytes over3-4orders of magnitude, the detection limits ranged from4.43×10-8～1.49×10-7g/mL. This proposed procedure has been successfully used for the analysis of water and wine samples. |
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