Preparation And Evaluation Of Hydrophilic Hybrid Monolithic Columns

Hydrophilic capillary electrochromatography(HI-CEC)is a new type of capillary electrochromatography that combines polar stationary phases with a more hydrophobic water-containing polar mobile phase,which have attracted extensive attentions in the separation of polar substances.The organic-silica hybrid monolithic column,combinig the advantages of silica monolithic column and organic monolithic column,have the advantages of easy preparation,strong mechanical stability,high permeability and column efficiency,wide pH range,etc,which is the focus of the current research.The preparation of new hydrophilic hybrid monolithic column has important scientific significance for develping and perfecting the hydrophilic capillary electrochromatography.This paper is divided into four parts,and the specific research content is as follows:In chapter 1,introduction.The basic principle of hydrophilic capillary electrochromatography is introduced in detail.The basic types of capillary column and the preparation technology of hybrid monolithic column are introduced systematically.The contents and significance of this paper are introduced.In chapter 2,a newly boronic acid affinity hybrid monolithic column was prepared through click chemistry,by using hexadecene and tetraethylene benzene boronic acid(VPBA)as functional monomers.The preparation conditions of the column were optimized,including the temperature,the content of urea,monomer and the choice of solvent.The prepared monolithic column had good permeability,mechanical stability and reproducibility.And the chromatographic retention behavior of the monolithic column was investigated.The results show that the monolith has hydrophilic interactions,reversed-phase chromatographic behavior,anion-exchange interactions and affinity interactions by separating neutral,acidic and alkaline compounds.In chapter 3,an ionic liquid type hydrophilic hybrid monolithic column was prepared by using "one-pot",by using 1-allyl-3-methylimidazolium chloride as functional monomer,tetramethoxysilane and mercaptopropyltrimethoxysilane(MPTMS)as silylation reagent.The preparation conditions of the column were optimized,including the temperature,the content of urea and monomer.The microstructures and structures of the monolithic columns were characterized by scanning electron microscopy(SEM).The effects of pH value,acetonitrile content and salt concentration on the electroosmotic flow of the hybrid monolithic column were investigated.And the mechanical stability of the hybrid monolithic column was investigated under the condition of different viscosity mobile phase.The experimental results show that the prepared hybrid monolithic column has good mechanical stability.On the basis of this,the separation effect of neutral small molecule,benzoic acid and polycyclic aromatic hydrocarbons(PAHs)on the hybrid column have good performance.In chapter 4,a new type of neutral and hydrophilic organic-silica hybrid capillary monolithic column was successfully prepared by improving the "one-pot"technology with the water-soluble initiator azobisisobutylamidine(AIBA)as the initiator.The addition of AIBA allows the silane reagent TMOS,MPTMS and functional monomer hydroxyethyl methacrylate(HEMA)to be homogeneously mixed.The preparation conditions,the mechanical stability and electroosmotic characteristics of the hybrid monolithic column were investigated.Due to the presence of polar hydroxyl groups on the stationary phase,the electroosmotic can be generated with the ions in the mobile phase.The hydrophilicity of the hybrid column was investigated,and the separation of phenol and benzoic acid was achieved in HI-CEC mode.