| Capillary electrophoresis(CE)is an effective tool for separation and analysis due to its high resolution,short analytical time,easy cleaning and environmental friendliness.Recently,capillary electrochromatography(CEC)has been widely recognized as a powerful separation technique combining high separation efficiency of CE with high selectivity of high performance liquid chromatography(HPLC).This chapter mainly introduces the principles and devices of CE and CEC,the applications of chiral selectors in chiral resolution,and new research advances in microextraction based on hollow-fiber membrane.Combining the nanomaterials and CE technology,this thesis focused on the exploration of the construction and optimization of novel electrophoretic separation systems and extraction systems based on laser-induced fluorescence(LIF)and amperometric detection(AD)technology,respectively.And then the developed methods were tried to apply for biomedical analysis,especially for analyses of the homologues,isomers and chiral compounds.In the first work,a novel CE-LIF method has been developed for the simultaneous analysis of ten potential lipid peroxidation metabolism biomarkers,low molecular weight aldehyde homologs(LMWAs),in exhaled breath condensate(EBC)with fluorescein 5-thiosemicarbazide as a derivatization reagent.In a simple capillary zone electrophoresis mode,ten LMWAs could be well separated within 30 min.The reaction efficiency was doubled by increasing the pH value of derivative system and magnetic stirring,and the LODs reached 0.16-3.4 nM(S/N=3).Acceptable recoveries(82.1-115 %)were obtained for EBC samples,and the RSD were within 7.9 %.This developed method has been applied for the analyses of EBC samples and evaluation of the correlation between smoking and the contents of aldehyde metabolites in EBC.Due to no need of buffer additives and sample preconcentration,this proposed method may provide an appealing alternative for the trace analyses of LMWAs in noninvasive biofluids.In the second work,a novel method has been developed for selective and sensitive determination of chiral amino acids in noninvasive fluids using D-His-ZIF-8-HF-LPME coupled with CE-LIF system.Under the optimal enrichment conditions,the concentration of D-His-ZIF-8 was 0.025 mg/mL,the supporting liquid membrane was tributyl phosphate,the volume of the donor phase was 8 mL(pH = 3.00),and the volume of the acceptor phase was 50 mM NaOH,the extraction temperature was 25 ℃,the stirring rate was 600 rpm,and the extraction time was 60 min.The enrichment of chiral amino acids could reach 640 times,and this developed D-His-ZIF-8-HF-LPME method could provide higher enrichment for D-type amino acids than that of L-type ones.The obtained extraction solution could be directly analyzed by CE-LIF.This method has been successfully applied to the determination of chiral amino acids in noninvasive fluids,including EBC and saliva samples.The extraction process did not require the operation of desorption,which effectively simplifies the pretreatment procedure.It provides a simple and sensitive method for the separation and detection of chiral amino acids in complex sample matrices.In the third work,the composite quantum dots(QDs)based on β-CD and its derivatives were prepared and added to the running buffer as pseudo-stationary phase for enantioseparation of six groups of model chiral analytes based on CE-LIF.The effects of composite QDs concentration,the pH value and concentration of the running buffer on resolution were investigated,respectively.The RSDs of interday and intraday repeatability were in the range of 2.7-8.1 %,0.7-3.9 %,and 1.5-3.8 % for the peak area,migration time and resolution,respectively.The theoretical calculation results of the binding energies and binding constant further validated the interaction mechanism of composite QDs and target analytes.Furthermore,this developed method was successfully applied to the analysis of the active components(catechin and epicatechin)in Chinese herb Catechu,and the recoveries were in the range of 92.2-108 %.The preparation strategy of the composite β-CD@QDs could be appropriate for the enantioseparation of more enantiomers by adjusting the modifiers on the surface of QDs,which is particularly promising for electrophoretic enantioseparation based on fluorescence detection,especially for those analytes lacking proper derivative functional groups.In the fourth work,a novel chiral BSA@ZIF-8 OT column was established for separation of nine groups of model isomers based on mini-CEC-AD,including homologues,structural isomers,positional isomers and enantiomers.Firstly,the morphology and structural characterization of ZIF-8 nanoparticles of different sizes and BSA@ZIF-8 modified OT columns were performed.Then,the effects of ZIF-8 concentration,BSA concentration,pH value and concentration of the running buffer were investigated,respectively.Based on the evaluation of separation performance and stability,this method has been successfully applied to the determination of ephedrine and pseudoephedrine in traditional Chinese medicine ephedra.When hydrochloric acid was used as the sample diluent,the LODs reached 1.5-2.0 ng/mL(S/N=3),and the recoveries were 85.1-106 %.The prepared OT columns possess the characteristics of simple preparation,high efficiency,environmental friendliness,and have good reproducibility and stability.It provides a simple analytical method for the enantioseparation of chiral drugs,especially the analyses of active components in traditional Chinese medicines.In the fifth work,a novel kind of chiral OT column was established with chiral ZIF-8 nanomaterials using L-histidine as chiral carbon center(L-His-ZIF-8).Seven groups of chiral model compounds,including two groups of amino acids,two groups of drug enantiomers and three groups of neurotransmitter enantiomers were enantioseparated based on mini-CEC-AD system.The morphology of L-His-ZIF-8 nanoparticles was characterized.The effects of L-His-ZIF-8 concentration,pH value and concentration of running buffer on the resolution of chiral compounds were investigated,respectively.The separation performance of these prepared chiral OT columns was explored by using amino acids and drugs as chiral model compounds.Under the optimal conditions,the RSDs of run-to-run,day-to-day and column-to-column reproducibility were less than 6.7 % using salbutamol as chiral model molecule,indicating that the prepared chiral OT columns have good reproducibility and stability.This method has been successfully applied to the analysis of chiral purity of actual drugs,and it might provide a potential novel method for the rapid separation of chiral compounds. |
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