Preparation And Performance Evaluation Of Mixed-Mode Stationary Phase In Capillary Liquid Chromatography

With the development of biological science and other fields,more and more complex mixtures need to be analyzed.However,traditional single-mode columns could not meet analytical demands.Mixed mode chromatography(MMC),in which multiple interactions are existed between the stationary phase and analytes,possesses good separation efficiency and broader analyte coverage,the same column can be used either in a single mode(such as reversed-phase,ion-exchange),or in a combination of modes.In this paper,mixed mode capillary columns were prepared by chemical modification,and chromatographic performance was evaluated by a series of experiments in different separation modes.In the preface section,basic concepts of capillary liquid chromatography、three types of capillary column(including Packed capillary column,Monolithic capillary column,Open-tube capillary column)and MMC are briefly summarized.Finally,the research purpose and significance of this paper were introduced.Chapter 2: Green preparation and performance evaluation of γ-aminobutyric acid bonded silica stationary phase in Capillary liquid chromatography.A γ-aminobutyric acid(GABA)bonded silica stationary phase for capillary liquid chromatography was prepared via chemical modification method in this study,named as Sil-GABA.Whole reaction was achieved in green medium with water as solvent.The prepared Sil-GABA stationary phase was characterized by Fourier transform infrared spectroscopy and elemental analysis.The Sil-GABA was used as packing materials for capillary column and its chromatographic performance was evaluated by a series of experiments in different separation modes.The results showed that three nitrochlorobenzene positional isomers and seven sulfonamides were separated effectively on Sil-GABA with ammonium acetate as the mobile phase in per aqueous liquid chromatography(PALC),respectively.Four benzoic acid compounds were separated via ion exchange interaction in hydrophilic interaction chromatography(HILIC)with a high content of organic solvents as the mobile phase.Additionally,three nitroaniline positional isomers could also be separated on in reversed phase liquid chromatography(RPLC).Under the optimal conditions,the relative standard deviations(RSD)of the retention times for the sulfonamides were within 3.2%,indicating good reproducibility of Sil-GABA column.Based on the multiple retention mechanisms,it is expected that Sil-GABA could be valuable for the chromatographic separation in capillary liquid chromatography.Chapter 3: Glycol diglycidyl ether and γ-aminobutyric acid functionalized silica as a mixed mode stationary phase for capillary liquid chromatography.In this study,a mixed mode stationary phase for capillary liquid chromatography was prepared by chemical modification of glycol diglycidyl ether(EGDE)and GABA bonded to the silica,named as Sil-EGDE-GABA.The Sil-EGDE-GABA was characterized by Fourier transform infrared spectroscopy and elemental analysis.The retention of nucleotide bases at different acetonitrile levels in the mobile phase indicated that the stationary phase possessed both HILIC and RPLC characteristics.Positional isomers,aniline compounds and a mixture of polar-nonpolar analytes were separated in RPLC mode.The stationary phase exhibited different separation mechanisms in the separation of positional isomers,compared with a commercial ODS column.Sulfonamides and biogenic amines were able to be separated in HILIC mode.Owing to the existence of multi-functionalized groups for Sil-EGDE-GABA,it is foreseeable that this material can not only be used as a versatile stationary phase in capillary liquid chromatography,but also as a solid extraction adsorbent in other chemical fields.Chapter 4: Preparation of a stationary phase with poly(ethyleneimine)embedded and its performance evaluation in Capillary liquid chromatography.A mixed mode chromatographic stationary phase with polyethyleneimine(PEI)embedded was synthesized by grafting L-phenylalanine onto the branched chains of hyperbranched polyethyleneimine(PEI)via amidization.The prepared stationary phase was characterized by Fourier transform infrared spectroscopy and packed into a capillary column.Its chromatographic performance was evaluated by a series of experiments.Three nucleosides are separated in HILIC mode.Four polycyclic aromatic hydrocarbons(PAHs)were separated in RPLC mode.Four organic acids were separated in ion exchange chromatography(IEC)mode.In addition,the retention mechanism under different modes was discussed by the investigations about effects of acetonitrile concentration or pH of mobile phase on the retention of analyte.