Novel Ionic Liquids-based Monolithic Columns: Preparation And Its Properties For Chromatographic Separation

As the fourth-generation of high-performance liquid chromatography(HPLC)stationary phases,monolithic columns possess the advantages of low back pressure,fast analysis speed and high resolution.The development of new types of monolithic columns is vitally important to meet the increasing demands for the separation and analysis of complex samples.In this work,we focus on the preparation of new hybrid monolithic column by combination of polyhedral oligosilsesquioxane(POSS)and ionic liquid.By further anion exchange via amino acid,a variety of amino acid modified monolithic columns were further prepared.The separation performances of these columns were also investigated.The full text is divided into five chapters for discussion.In the first chapter,firstly,the monolithic column separation technology is reviewed.Then,the application of POSSs in monolithic column is summarized.The application status of ionic liquids in monolithic column is expounded.Finally,the necessity and significance of this research is pointed out.In the second chapter,with POSS methacryl substituted(POSS-MA)as the crosslinker,1-vinyl-3-dodecylimidazole bromide(VDI)as the monomer,the VDI-modified hybrid monolithic column(POSS-VDI)was prepared by one-pot method.Subsequently,the POSS-VDI monolithic column was characterized by scanning electron microscope(SEM),Fourier Transform infrared spectroscopy,nitrogen adsorption method,elemental analysis,and thermogravimetric analysis,respectively.The results can prove the POSS-VDI monolithic column was successfully prepared.The POSS-VDI column is of continuous and uniform micropore,mesopore and macropore structure.It is suitable for the separation and analysis of both small molecules and complex macromolecules.In the third chapter,the retention mechanisms of the POSS-VDI column were first discussed.The results show that the POSS-VDI column has typical retention characteristics of reversed phase/ion exchange.Then,the column was applied for the separation and analysisof alkylbenzenes,polycyclic aromatic hydrocarbons,anilines,halogenated benzenes,benzene derivatives as well as hydrophilic thioureas.The POSS-VDI column displays good separation performances for these compounds.Furthermore,the POSS-VDI column also shows high separation selectivity for phenols and dihydroxybenzene isomers as well as nitrophenol isomers.The maximum column efficiency is 137,000 N/m.The POSS-VDI column was also used for the analysis of extracted components of Chinese medicine stephania tetrandra,root of kudzu vine and the rhizome of Chinese goldthread.Efficient analysis of active ingredients in these Chinese medicines can also realizedIn the fourth chapter,L-proline(L-Pro),glycine(Gly),L-alanine(L-Ala)and DL-phenylalanine(DL-Phe)were used to modify the POSS-VDI column via ion exchange.Four new monolithic columns POSS-VDI-Pro,POSS-VDI-Gly,POSS-VDI-Ala and POSS-VDI-Phe were successfully fabricated.Their chromatographic performances of these columns were investigated via the separation of proteins extracted from egg whites.These amino acids post-modified monolithic columns shows good separation performances,outperforming that of the POSS-VDI monolithic column.In the last chapter,the full work was summarized.