| Capillary electrophoresis is one of the new type and important liquid separation technology which is developing rapidly in nearly 30 years. It has been widely used in different fields, such as natural products, food, clinical medicine and the environment. Compared with performance liquid chromatography, It has showed powerful capability for the analysis of complex samples due to its simple pretreatment, high separation efficiency and speed, low consumption of reagents and sample, the diverse separation mode and the high degree of automation. The aim of this dissertation is to apply the CE technique to resolve some actual analytical problems in natural product and food analysis. The contents of the dissertation include five chapters.In Chapter 1,I introduced the principle, the separation modes, the coupling technique and applications of capillary electrophoresis. The applications of capillary electrophoresis in natural product and food analysis were highlighted.In Chapter 2, a method of capillary electrophoresis with amperometric detection was achieved for the analysis of saponins PD in Fructus Akebiae. The effects of some important factors such as detection potential, buffer system, concentration and p H, separation voltage were investigated. The analyte could be separated within 6 min at the separation voltage of 18 k V in a 20 mmol/L borate buffer(p H8.8) respectively. The detection potential was set at 0.9V(Vs.SCE). Calibration curve was linear over the range of 0.5~50μg/ml for saponins PD(r=0.9976). The detection limits was 0.05μg/ml. The recoveries of saponins PD was 101.4%(RSD<4.3%). The proposed method was successfully applied to the analysis of active ingredients in Fructus Akebiae with satisfactory assay results.In Chapter 3, a sensitive and simple method based on capillary electrophoresis(CE) with electrochemiluminescence(ECL) detection has been developed for the separation and determination of Rhodamine B in Chilli power. The effects of detection potential, the concentration of,the acidity and the concentration of the running buffer, separation voltage and injection time were investigated to acquire the optimum conditions. The detection electrode was a 300μm diameter platinum microelectrode at a detection potential of +1.14 V(versus Ag/Ag Cl). Rhodamine B could be well separated within 6 min in a 50 cm length fused-silica capillary at a separation voltage of 15 k V in a 20 mmol/L PBS buffer(p H=8.0). The response range of Rhodamine B was from 5×10-7 to 5.0×10-5 mol/L with a detection limit of 1×10-7mol/L(S/N=3). This proposed method demonstrated long-term stability and reproducibility with relative standard deviations(R.S.D.) of less than 3.5% for both migration times and electrophoretic peak area(n=5). The proposed method was successfully applied to the analysis of active ingredients in Chilli power with satisfactory assay results.In Chapter 4, A method was developed for determination of gigantol,erianin and moscatilin in dendrobium candidum by capillary electrophoresis with amperometric detection. The effects of some important factors such as detection potential, buffer system, concentration and p H, separation voltage were investigated. The analytes could be separated within 13 min at the separation voltage of 15 k V in a 10 mmol/L borate buffer(p H=9.6) respectively. The detection potential was set at 1.0V(Vs.SCE). The relationship between peak area and analyte concentrations was linear over about three orders of magnitude with detection limits(S/N= 3) ranging from 0.1~0.5μg/m L for all analytes. The recoveries of all analytes were between 97.5 % and 103.3%(RSD<4.5%). This proposed method demonstrated long-term stability and reproducibility with relative standard deviations of less than 4% for both migration time and peak area(n=5).The proposed method was successfully applied to the analysis of bihenzyls in dendrobium candidum with satisfactory assay results.In Chapter 5, A methord based on capillary electrophoresis with amperometric detection was established for the separation and determination of rutin in toosendan fruit. Detection potential, buffer concentration and p H, separation voltage and injection time were investigated to acquire the optimum condition. Uncoated silica capillary column(50 μm i.d.×50 cm i.d.)was used as the separation channel, the two analytes could be well separated within 10 minutes by using 30 mmol/L sodium borate buffer(p H=9.4) and 15 k V as the separation voltage.The detection electrode was platinum disk electrode(0.3mm i.d.) and the detection potential was 1.00V(vs.Ag/Ag Cl). Under the optimized experimental conditions above, there was a good linear relation for rutin ranging from 8.2×10-6 mol/L to 5.2×10-4 mol/L. The detection limit for rutin was 9.0×10-7mol/L(S/N=3). The method has been successfully used for the assay of bioactive compounds of toosendan fruit extracts. |
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