One-Pot Preparation And Chromatographic Evaluation Of Capillary Monolithic Columns By Thiol-Ene Click Chemistry

The column is the heart of the chromatographical system,which plays a key role in the separation process.An ideal stationary phase should have good selectivity,chemical stability,and separation efficiency.Monolith as a new generation of stationary phase has the good permeability,fast mass transfer characteristics,which can realize rapid and high efficiency separation,and has aroused wide attention in recent years.With the development of monolith,however,the researchers are still searching for novel monoliths to broad the application of monolith stationary phase.As a novel copper-free click reaction,thiol-ene click chemistry is a new strategy for preparation of monoliths.Because of its simple reaction,high efficiency,mild reaction conditions,and good chemical selectivity,thiol-ene click chemistry has been widely concerned.In the process of the preparation of monolith,the introduction of various functional groups is very important,therefore,thiol-ene click chemistry for the preparation of monoliths with different functional groups provide an effective way.At present,the preparation of monolithic column are reported via thiol-ene click reaction,but mostly using two-step or multistep method,which would resulted in relatively complicated and time-consuming.However,the one-pot method for the preparation of monolith is simple and time-saving,therefore,three different monoliths were prepared based on thiol-ene click reaction in this thesis.What is more,the chromatographic performances were studied and the possible retention mechanisms were detailedly discussed.The details are as follows:1.A novel chiral cyclodextrin(CD)monolith was easily prepared via a one-pot process based on the thiol-ene click reaction of allyl-?-CD with pentaerythritol tetra-(3-mercaptopropionate)(PETMP)in a fused-silica capillary.The effects of both the composition of prepolymerization solution and reaction temperature on the morphology,permeability,and selectivity of the P-CD chiral monolith were investigated in detail.The conditions were optimized to fabricate a homogeneous and permeable chiral monolith.In this study,the(3-CD monolith was used as the stationary phase of capillary liquid chromatography(cLC)for the chiral separation of several pharmaceutical enantiomers,all the tested racemates could be enantioseparated well within 13min.Compared to the previously reported two-step method,this one-pot method for the preparation of a ?-CD chiral monolith is simple and time-saving.These results indicate that the thiol-ene click chemistry provides a simple and robust method for the preparation of a chiral ?-CD monolith.2.In this work,a novel imidazolium-based monolith was fabricated through a simple route.With 1-vinyl-3-octadecylimidazolium bromide([VC18Im]Br)and ethylene dimethacrylate as monomers(EDMA),pentaerythritol tetra-(3-mercaptopropionate)(PETMP)as crosslinker,the monolith was facilely fabricated by one-pot thiol-ene click chemistry.The influences of both the content of monomer/crosslinker and porogenic systems on themorphology,and permeability of the monolith were studied.The optimal reaction conditions were used to prepare a homogeneous and permeable monolith.High efficiency and quick separation of alkylbenzenes,styrene and ethylbenzene,polycyclic aromatichydrocarbon,phenols,anilines,and aromatic acids were achieved in cLC mode.Multiple interactions such as hydrophobic interaction,?-? interaction,and anion-exchange interaction were discussed.The minimum plate height of this monolith were determined as 11.42?m for thiourea and 13.26 ?m for benzene.All results indicated that thiol-ene click chemistry provides a quick way for the fabrication of imidazolium-based monolith.3.In this study,we developed a facile process based on mild thiol-ene click reaction of allyl-p-cyclodextrin(allyl-?-CD)with 1,4-benzenedithiol for preparing structurally well-defined?-CD monolith.The conditions such as the qualities of monomer/crosslinker,porogenic systems and reaction temperature were optimized to prepare a porous and stable monolith.In cLC mode,the P-CD monolith had good separation ability for organic micropollutants such as aromatic model compounds and plastic components,and some chiral pharmaceuticals.Multiple interactions such as hydrophobic interaction,chiral resolution,host-guest interaction were discussed.The highest column efficiency was 63200 plates/m.These results demonstrate the great promising of thiol-ene click chemistry for preparing ?-CD monolith.