Study On The Determination Of Bioactive Constituents And Electrochemical Fingerprints Of TCMs By CE-ED

Capillary electrophoresis with electrochemical detection(CE-ED) and the related techniques have been employed and developed for the determination of bioactive constituents in Ricinus communis Linn.leaves,Folium Eriobotryae and Cortex Fraxini,as well as their electrochemical fingerprints,respectively.In Chapter One,the background and recent development of capillary electrophoresis, as well as techniques for extraction and separation of bioactive constituents in traditional Chinese medicines(TCMs) were briefly reviewed.Recent studies on the determination of bioactive constituents and electrochemical fingerprints of TCMs by CE-ED were mainly discussed.In Chapter Two,a CE-ED system was established for TCMs study.Details about the system,such as its configuration,apparatus parameters,installation,working conditions,and operation procedures,were introduced.In Chapter Three,the CE-ED system was employed for the separation and determination of disaccharide glycoside rutin,gentistic acid,quercetin,and gallic acid in the leaves of Ricinus communis Linn.for the first time.The effects of the acidity and the concentration of the running buffer,separation voltage,injection time,and detection potential were investigated to acquire the optimum conditions for the determination of the four analytes.The detection electrode was a 300 um diameter carbon disc electrode at a detection potential of +0.90 V(vs.SCE).The four analytes could be well separated within 10 min in a 40 cm length fused silica capillary at a separation voltage of 15 kV in a 50 mM borate buffer(pH 9.0).The relation between peak current and analyte concentration was linear over about 3 orders of magnitude with detection limits(S/N=3) ranging from 0.8 to 2.9 uM for all the analytes.The proposed method has been successfully applied to monitor flavones and phenolic acids in the real plant samples with satisfactory assay results.In Chapter Four,a method based on CE-ED with the aid of microwave-assisted solvent extraction was developed for the determination of catechin,rutin,kaempferol, gentistic acid,and quercetin in Folium Eriobotryae.The effects of the acidity and the concentration of the running buffer,separation voltage,injection time,detection potential,and irradiation time were investigated to acquire the optimum analysis conditions.The detection electrode was a 300-um-diameter carbon disc electrode at a detection potential of +0.90 V.The five analytes could be well separated within 12 rain in a 40-cm-length fused silica capillary at a separation voltage of 12 kV in a 50 mM borate buffer(pH 9.0).The relation between peak current and analyte concentration was linear over about three orders of magnitude with detection limits ranging from 2.1 to 4.5 uM for all the analytes(S/N=3).In Chapter Five,a novel CNT/EVA composite electrode was developed for the elctrochemical detection in capillary electrophoresis.The composite electrode was fabricated by packing a mixture of CNTs and melted EVA in a piece of fused silica capillary under heat.It was coupled with CE for the separation and detection of esculin and esculetin in Cortex Fraxini to demonstrate its feasibility and performance. Esculin and esculetin have been well separated within 9 min in a 40-cm-long capillary at a separation voltage of 12 kV using a 50 mM borate buffer(pH 9.2).The new CNT-based CE detector offered significantly lower detection potentials,yielded enhanced signal-to-noise characteristics,and exhibited high resistance to surface fouling and enhanced stability.It showed long-term stability and reproducibility with relative standard deviations of less than 5%for the peak current(n=15).