| High performance capillary electrophoresis(CE)is a liquid phase separation technology which uses capillary as the separation channel and high voltage DC(HVDC)field as the driving force.This technology has flexible separation mode,fast analysis time and,a small amount of reagents and samples required for the analysis,and currently,it has been rapidly developed as one of the separation techniques.However,CE analys is is usually limited by the used detectors.Common UV detectors have a relatively low sensitivity due to the small detection path,and meanwhile,these detectors are not beinific ial for detecting the target analytes with weak or without optical absorption.In addition,UV detectors also limit the use of certain additives with optical absorption properties.The laser-induced fluorescence detector is sensitive,but is limited by the excitation wavelength and then cannot be widely used.Mass spectrometry is an extremely efficient detection method,but the high analytical requirements,expensive instrument and required ancillary services are not beneficial for their popularization and wide applications.The capacitively coupled contactless conductivity detection(C~4D)technique has increased considerably in miniaturized systems,in which the response arises from the difference in conductivity between the analytes and background running solutions.As a novel detection technology,C~4D device has a simple construction and high sensitivity,and also,the arrangement can prevent the electrode fouling from other electrochemical detectors.Therefore,CE-C~4D has been widely used in many fields such as drug analysis,food analysis,and environmental analysis.The purpose of this paper is to construct a C~4D-based capillary electrophoresis system and expand its application ranges.Based on previous studies,a complete CE-C~4D device was firstly constructed and relevant parameters were optimized,and then the developed device was applied for the analysis of several target analytes with weak or without optical absorption,including taurine and quaternary nitrogen alkaloids in foods,as well as selectfluor about its purity analysis and fluorination reaction monitoring.This dissertation can be divided into four chapters:Chapter one:As a novel detection technology,C~4D has been rapidly developed in recent years,and its principle,construction and progress were firstly briefly summarized,and further,its applications were reviewed for the analysis of metal cations,inorganic anions and organic small molecules.Chapter two:The CE-C~4D system was constructed,and on this basis,a simple and sensitive analytical method for taurine,hypotaurine and high taur ine was developed.After a systematic optimization,the separation buffer was consisted of 10 mM Tris,2 m M EDTA disodium(p H 8.8),0.05 mM CTAB as an electroosmotic inversion reagent,and excitation frequency of 341 kHz.Under these conditions,the four analytes taurine,hypotaurine,and taurine were separated within 8min with respective linear range of 10-200,5-200,and 5-200?M(R~2>0.997),and limits of detection(LODs,S/N=3)of 0.32,0.15,and 0.13?M.The intra-day and inter-day relative standard deviations(RSD)were less than 0.8%and 1.5%for migration time,and less than 4.2%and 7.8%for peak area,indicating good precision of the developed detection system.Finally,this method was successfully applied for the detection of taurine in functional beverages and infant formula milk powder with satisfactory results.Chapter three:Based on a self-built CE-C~4D device,four analytes including choline,acetylcholine,carnitine and acetylcarnitine were separated within 3 min,using 10 m M acetic acid as the background buffer solution.The intra-day and inter-day RSD were less than 0.82%and 1.3%for migration time and less than 4.4%and 7.7%for peak area,respectively.Under optimal conditions,the linear ranges were determined to be 1-200,1-200,2-200,and 3-200?M(R~2>0.997),while the LODs(S/N=3)were 21,24,24 and 34 ng/m L for choline,acetylcholine,carnitine,and acetylcarnitine,respectively.Finally,this method was successfully applied for the detection of choline,acetylcholine,carnitine and acetylcarnitine in four different brands of yogurt.Chapter four:Based on a self-built CE-C~4D device,a simple and sensitive analytical method was developed for the detection of selectfluor method.Using 10 mM acetic acid as the background buffer solution,the separation of selectfluor,its precursor TEDA and the intermediate TEDA-Cl was achieved within a very short time(120 s).The linear ranges were calculated to be5-200,1-200,and 0.5-200?M(R~2>0.997),and the LODs(S/N=3)were determined to be 50.3,56.5,and 54.4 nM,respectively.Furthermore,this method was successfully applied for monitoring the fluorination reaction in which selectfluor participated in. |
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