Study On The Determination Of Bioactive Constituents In Traditional Chinese Medicines By Capillary Electrophoresis With Electrochemical Detection

Capillary electrophoresis with electrochemical detection (CE-ED) and the related techniques have been employed and developed for the determination of bioactive constituents in Folium Lysium Chinensis, leaves of Rhododendron mucronulatum Turcz and Radix Isatidis respectively.In Chapter One, the technology and recent development of capillary electrophoresis, as well as technical methods for extraction, separation and detection of bioactive constituents in traditional Chinese medicines (TCMs) were briefly reviewed. Recent studies on the applications of CE-ECD in determination of bioactive constituents of TCMs.In Chapter Two, a CE-ED system with far IR-assisted extraction was established for the separation and determination of mannitol, sucrose, glucose and fructose in Folium Lysium Chinensis for the first time. The effects of the the voltage applied to the IR generator and irradiation time were investigated to acquire the optimum conditions for the determination of the four analytes. The detection electrode was a300-μm-diameter copper disc electrode at a detection potential of+0.65V. The four carbohydrates could be well separated within18min in a50cm length fused silica capillary at a separation voltage of9kV in a50mM NaOH aqueous solution. The relation between peak current and analyte concentration was linear over about3orders of magnitude with detection limits (SIN=3) ranging from0.66to1.15μM. for all analytes. The results indicated that far; infrared significantly enhanced the extraction efficiency of the carbohydrates in Folium Lysium Chinensis. The extraction time was significantly reduced to7min compared to several hours for conventional hot solvent extraction.In Chapter Three, a method based on micellar electrokinetic chromatography (MEKC or MECC) with amperometric detection and far infrared-assisted extraction has been developed for the simultaneous determination of two flavones (rutin and farrerol) and three phenolic acids (syringic acid, vanillic acid, and4-hydroxybenzoic acid) in the dried leaves of Rhododendron mucronulatum Turcz., a commonly used traditional Chinese medicine. The effects of some important factors such as the voltage applied on the infrared generator, irradiation time, the concentration of borate and sodium dodecylsulfate (SDS), separation voltage, and detection potential were investigated to acquire the optimum conditions. The detection electrode was a300μm diameter carbon disc electrode. The five analytes could be well separated within8min in a40cm length capillary at a separation voltage of12kV in a50mM borate buffer (pH9.2) containing50mM SDS. The relation between peak current and analyte concentration was linear over about3orders of magnitude with the detection limits (S/N=3) ranging from0.20to0.46μM. The results indicated that far infrared irradiations significantly enhanced the extraction efficiency. The extraction time was substantially reduced to6min compared to3hours for conventional hot solvent extraction.In Chapter Four, Carbon nanotube (CNT)-copper nanoparticle (CuNP) hybrid was prepared by the chemical reduction of a mixture containing cupric sulfate and CNT. The structure of the material was investigated by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The results indicated that CuNP with an average diameter of about15nm were deposited on CNT to form a well interconnected hybrid network. The material was mixed with paraffin oil and packed into the ends of fused capillaries to fabricate microdisc electrodes for sensing carbohydrates. Its analytical performance was demonstrated by sensing four carbohydrates in combination with capillary electrophoresis. The relation between peak current and analyte concentration was linear over about3orders of magnitude with detection limits ranging from0.18to0.62μM for all analytes.