| Capillary electrophoresis(CE)is a newly rapid developed technique in the area of separation and detection in the late 1980s.In the capillary(separation channel),the analyte according to the difference of the partition coefficient or the mobility between various components to achieve enrichment and rapid separation under the electric field force.With the advantages of high separation efficiency,low cost,little consumption of reagents etc.,capillary electrophoresis is gotten more and more attention and favor of scientific research workers in the separation and analysis field in these years.Different detectors successfully combined with CE bring more possibilities in the scope of application field.Through the unremitting efforts of the research workers,capillary electrophoresis has rapid development and wide applications in food analysis,drug testing,environmental monitoring,biological science and so on.However,due to small sample volume and limit of detector,CE cannot reach the sensitivity requirement for the analysis of trace components in biological system,so researchers are dedicated to the study on online enrichment technology combined with CE in addition to improving and perfecting various detectors,and look forward to improve the sensitivity and better separation of complex samples.In this paper,we focus on different online pre-concentration technique combined with CE-C4D or CE-LIF to improve sensitivity,and which are applied to the complex samples.The detailed profile in this dissertation is shown as follows:In charpter one,we summarize the CE development history,separation principle and mode,sampling technique,detection methodologies,on-line enrichment technology and application,and finally introduce the purpose and significance of this research.In charpter two,a simple,rapid,and sensitive method based on capillary electrophoresis(CE)combined with capacitively coupled contactless conductivity detection(C4D)using an on-line pre-concentration method of field-enhanced sample injection(FESI)was developed for the simultaneous determination of artificial additives(nitrite,erythorbate,sorbate,nitrate,sulfate)in food.The optimized results were obtained using a background electrolyte(BGE)composed of MES/His(20 mM/20 mM),with Hydroxylpropyl-beta-cyclodextrin HP-p-CD(0.0025%)and hexadecyltrimethylammonium bromide CTAB(1 mM)as additives.The detection limit(defined as S/N=3)for the optimal procedure ranged from 0.05 to 1 mg L",.In order to evaluate the application potential of the proposed method,simultaneous separation and quantitative determination of nitrite,erythorbate,and sorbate were implemented for the case of real ham sausage samples with recoveries of 91.9%-106.2%.In charpter three,a new method of capillary electrophoresis(CE)combined laser induced fluorescence(LIF)detection via online pre-concentration techniques including transient trapping combined with the dynamic pH junction mode was developed for the sensitive determination of glutathione in biological samples.The important parameters governing the pre-concentration and separation were investigated in order to obtain maximum resolution and sensitivity.The analytes were compressed into a narrow zone due to the effect of the dynamic pH junction mode,and then transiently trapped by SDS micelles at the interface of the sample and micellar areas.The limits of detection for reduced glutathione,glycine,oxidation glutathione,cysteine,and glutamic acid were 0.01,0.01,0.5,0.7,and 0.1 nM(S/N = 3),respectively,under the optimal condition.The enhancement factors obtained when using the transient trapping combined with the dynamic pH junction mode as pre-concentration process enhanced from 87 to 430 when compared to the results obtained by the classical CZE mode.Moreover,this optimized method was successfully applied to bacteria(Escherichia coli,Salmonella typhimurium,and Staphylococcus aureus)and HaCaT cells samples for the determination of reduced glutathione with satisfactory recoveries.In charpter four,a sensitive and simple method of capillary electrophoresis(CE)-laser induced fluorescence(LIF)with two on-line enrichment technologies including sweeping and dynamic pH junction was developed for separation and detection of eight amino acids in biological fluids.After exploration of some parameters in regard to the separation and enrichment,under the optimal conditions,the limits of detection for arginine,lysine,tryptophan,histidine,valine,tyrosine,serine,alanine were 0.07,0.35,0.15,0.20,0.20,0.15,0.33,0.10 nM(S/N = 3),respectively,and the enrichment ratio were between 44-67.In addition,this method was successfully applied for the detection of amino acids in human saliva with satisfactory recoveries. |
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