| Micro-column liquid chromatography has the advantages of low consumption of solvent and sample,fast heat dissipation,high separation efficiency,and high sensitivity,which is widely used in biological,pharmaceutical,food,and environmental fields recently.The reduction of column inner diameter is the typical feature of micro-column liquid chromatography,even though it would complicate the preparation process.Compared with packed columns,polymer monolithic columns have the advantages of simple preparation,low back pressure,high permeability and easy modification,which have gained more attention in the field of micro-column liquid chromatography.However,it is difficult for polymeric monolithic columns to obtain good separation efficiency and resolution when separating small molecule compounds.In view of this,developing new polymeric monolithic columns,simplifying synthetic routes,improving the separation efficiency and expanding applications are still the research focus in the field of micro-column chromatography.In this thesis,based on a micro-liquid chromatography installation built by ourselves in the laboratory,the following three works were carried out in combination with the capillary monolithic columns: a reversed-phase monolithic column was prepared using lauryl methacrylate(LMA)as the functional monomer for the analysis of parabens preservatives in cosmetics;a hydrophilic monolithic column was prepared using [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide(MEDSA)as the functional monomer and the effect of different crosslinker on the separation of the monolithic column was compared;a chiral monolithic column was prepared using allyl-β-cyclodextrin(allyl-β-CD)as the functional monomer and its separation performance was evaluated.The full thesis is divided into five chapters:Chapter 1: The basic theory of micro-column liquid chromatography is briefly introduced and the advantages and disadvantages of packed columns,open-tube columns and monolithic columns are summarised.On this basis,the classification of monolithic columns and the factors affecting the morphology,permeability and separation performance of polymeric monolithic columns are introduced,and the separation mechanism and applications of monolithic columns are briefly outlined.Chapter 2: A reversed-phase polymer monolithic column was prepared using LMA as the functional monomer and dipentaerythritol amyl/hexyl acrylate(DPEPA)as the crosslinker,and a microcolumn liquid chromatography system was constructed inhouse as the core.The effect of monomer ratio and porogen ratio on the separation performance of the monolithic column was further investigated using alkylbenzene as a model compound.On this basis,a separation method for parabens using this microcolumn liquid chromatography system was developed and applied to the analysis of parabens in various cosmetic products.The method has a short analysis time and good precision and sensitivity.Chapter 3: A hydrophilic interaction liquid chromatography(HILIC)monolithic column was prepared using MEDSA as the functional monomer,based on the microcolumn liquid chromatography system above.And the effects of DPEPA and other two crosslinker EDMA and BIGDMA on the morphology and separation performance of the column were compared,and it was found that the monolithic column crosslinked by DPEPA suggested a lower eddy diffusivity.Based on this,the monolithic columns were successfully used for the separation of nucleotides,neonicotinoids and phenolic acids with column efficienciy up to 98,000 N/m,demonstrating the potential of the synthesised hydrophilic polymer monolithic columns for the separation of polar small molecule compounds.Chapter 4: Based on the micro-column liquid chromatography system,a chiral monolithic column was prepared by thiol-ene click chemistry using allyl-β-cyclodextrin(allyl-β-CD)and pentaerythritol tetrakis(3-mercaptopropionate)(PETMP)as functional monomer and crosslinker.The separation performance of the monolithic column was evaluated by using alkylbenzenes and estrogens as the model compounds,and it’s adhibition for the chiral resolution of the drugs flurbiprofen and flavanones was attempted.Compared with some chiral columns reported previously,the allyl-β-CD monolithic column expressed high column efficiency,small tailing factor and stable mechanical properties,as well as excellent enantioselectivity and chemoselectivity.Chapter 5: A summary and an outlook of the above work. |
PDF Full Text Request