| Techniques based on capillary electrophoresis with electrochemical detection(CE-ECD) has been employed for the determination of bioactive constituents in Lonicera confusa DC., Herba Artemisiae Scopariae,Radix Cynanchi Paniculati and Cortex Magnoliae OfficinalisIn Chapter One,we briefly reviewed current developments of TCM Industry in China and main chemical methodologies in TCM qualification,including techniques on extraction, separation and detection of the analytes.Importantly,we introduced some background knowledge about the CE-ECD technology,such as its separation and detection methods,its formation,as well as its applications on analyzing bioactive constituents in TCM crude drugs and their compound preparations and on identification of TCMs.In Chapter Two,a CE-ECD system for the analysis of bioactive constituents in TCMs was established.We provided a detailed description about the CE-ECD system,such as conformation of the system,configuration,parameters,installation and conditions of the apparatus,operation procedures,etc.In Chapter Three,a method based on capillary electrophoresis with amperometric detection has been developed for the determination of luteolin,chlorogenic acid, 3,5-dicaffeoylquinic acid and caffeic acid in the dried flower buds,leaves and stems(three medicinal parts) of Lonicera confusa DC.,respectively.The effects of several important factors such as detection potential,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 carbon disc electrode at a working potential of + 0.90 V(vs.SCE).The four analytes can be well separated within 10 min in a 40 cm-long fused silica capillary at a separation voltage of 12 kV in a 50 mM borate- 25 mM phosphate buffer(pH 8.0).The relationship between peak current and analyte concentration was linear over about 3 orders of magnitude with detection limits(S/N = 3) ranging from 0.35 to 0.52μM for all analytes.The precision was examined from a series of seven repetitive injections of a sample mixture containing 0.5 mM luteolin,chlorogenic acid,3, 5-dicaffeoylquinic acid and caffeic acid.Reproducible signals were obtained with RSD of 3.4%,2.3%,2.5%and 2.7%for the peak currents,respectively.The proposed method has been successfully applied to the monitoring of bioactive constituents in the real plant samples with satisfactory assay results.In Chapter Four,capillary electrophoresis with electrochemical detection has been employed for the determination of p-hydroxyacetophenone,chlorogenic acid,and caffeic acid in Herba Artemisiae Scopariae.The effects of several important factors,such as the concentration and the acidity of the running buffer,separation voltage,injection time,and detection potential,were investigated to acquire the optimum conditions.The detection electrode was a 300-μm-diameter carbon disc electrode at a working potential of +0.90 V (vs.SCE).The three analytes can be well separated within 11 min in a 40-cm-long fused-silica capillary at a separation voltage of 15 kV in 50 mM borate buffer(pH 9.2).The relation between peak current and analyte concentration was linear over about 3 orders of magnitude,with detection limits(signal-to-noise ratio of 3) of 0.31,0.39,and 0.50μM for p-hydroxyacetophenone,chlorogenic acid,and caffeic acid,respectively.The precision of the peak current was examined from a series of seven repetitive injections of a sample mixture containing 0.5 mM p-hydroxyacetophenone,chlorogenic acid,and caffeic acid under the optimum conditions.Reproducible signals were obtained with relative standard deviations(RSDs) of 2.7%,3.1%,and 3.8%for the peak currents,respectively.The proposed method has been successfully applied to monitor the three bioactive constituents in real plant samples and to differentiate between different herbal drugs with satisfactory assay results.In Chapter Five,capillary electrophresis with electrochemical detection has been employed for the determination of three phenolic acetpophenones(including paeonol, p-hydroxyacetophenone and 2,4-hydroxyacephenone) in Radix Cynanchi Paniculati for the first time.Effects of several important factors such as the concentration and the acidity of the running buffer,separating voltage,injection time and detection potential were investigated to acquire the optimum conditions.The detection electrode was a 300 um diameter carbon disc electrode at a working potential of +0.90V(vs.SCE).The three analytes can be well separated within 0 min in a 50 cm length fused silica capillary at a separation voltage of 15 kV in a 50 mM borate buffer(pH 9.2).The relationship between peak current and analyte concentration was linear over about 3 orders of magnitude with detection limits(S/N = 3) ranging from 0.20 to 0.36μM for all analytes.The precision was examined from a series of seven repetitive injections of a sample mixture containing 0.25 mM PN,PHA and DHA.Reproducible signals were obtained with RSD of 3.4%,2.3%, 2.5%and 2.7%for the peak currents,respectively.The proposed method has been successfully applied to the determination of bioactive constituents in the real plant samples with satisfactory assay results.In Chapter Six,a novel carbon nanotube/poly(methyl methacrylate)(CNT/PMMA) composite electrode was developed and applied in the sensitive amperometri detection of CE.The performance of this unique system has been demonstrated by separating and detecting honokiol and magnolol in traditional Chinese medicine,Cortex Magnoliae Officinalis.Factors influencing their separation and detection processes were examined and optimized.Honokiol and magnolol were well separated within 7 min in a 40 cm long capillary at a separation voltage of 15 kV using a 50 mM borate buffer(pH 9.2).The new CNT-based CE detector offered significantly lower operating potentials,yielded substantially enhanced S/N characteristics,and exhibited resistance to surface fouling and hence enhanced stability.It demonstrated long-term stability and reproducibility with RSDs of less than 5%for the peak current(n=9).
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