Preparation And Chromatographic Evaluation Of Monolithic Capillary Columns Based On Thiol-Ene Click Chemistry

Due to its key role in the separation process,the chromatographic column is rightfully considered as the heart of the separation system.However,an ideal stationary phase should have good chemical stability,selectivity and separation efficiency.Monolithic columns possess a unique structure and exhibit some exceptional characteristics,which are regarded as new generation of stationary phases.Although the family of columns has continuously enlarged,researchers continue to pursue new columns to broaden their applications.As a novel copper-free click chemistry reaction,thiol-ene click reaction is a relative new field in the preparation of monolithic column.It has been attracting great interest since it possesses several advantages such as simplicity,high efficiency,high chemoselectivity and high conversion under mild conditions.And in the preparation of monolithic column,the introduction of various functional groups is extremely important.Therefore,the thiol-ene click is opening a new way for preparation of various functionalized monolithic columns.However,the reports about the preparation of the monolithic column based on the thiol-ene click reaction are still less.Therefore,we make use of the thiol-ene reaction to prepare three novel monoliths and evaluate their chromatographic performances.In addition,the possible retention mechanisms were also disscussed in detail.Details are followed as:1.A facile organic-silica hybrid monolith was prepared by a thiol-ene click reaction of polyhedral oligomeric silsesquioxane methacryl substituted(POSS-MA)with 1,4-bis(mercaptoacetoxy)butane(BMAB)using toluene and dodecanol as a porogenic system.The effects of the ratio of POSS-MA-BMAB and porogenic solvents and click reaction temperature on the morphology,permeability and column performance of the resulting POSS-BMAB hybrid monoliths were studied in detail.A series of test compounds,including alkylbenzenes(ABs),polycyclic aromatic hydrocarbons(PAHs),phenols and,anilines were used to evaluate the retention behaviors of the POSS-BMAB hybrid monolith in capillary liquid chromatography.The prepared POSS-BMAB hybrid monolith exhibited typical reversed-phase chromatographic behavior toward neutral solutes.The minimum plate height of this hybrid monolith was determined as 12.6 and 13.7μm for thiourea and benzene,respectively.These results demonstrate that thiol-ene click chemistry can provide a facile and robust approach for the preparation of a POSS-based hybrid monolith.2.A sulfo-functionalized POSS-based hybrid monolith was prepared by a thiol-ene click reaction.A series of test compounds,including ABs,PAHs,phenols and,anilines were used to compare and evaluate the retention behaviors of the POSS-based hybrid monolith in capillary liquid chromatography(cLC)and capillary electrochromatography(CEC),respectively.The prepared hybrid monolith exhibited both typical reversed-phase and ion exchange interactions chromatographic behavior.Compared with cLC separation mode,the CEC separation mode can effectively shorten the reaction time and improve column efficiency,but won’t change the elution order of analytes.3.A multipe-mercapto compound was selected as the crosslinking agent to prepare a carboxyl functionalized organic polymer monolith.The polymer monolith with high permeability and column efficiency was prepared.And the minimum plate height of this hybrid monolith was determined as 8.76 μm(132100 plates/m).In CEC mode,the test compounds including ABs,PAHs,phenols and anilines were used to evaluate the retention behaviors of the polymer monolith.The abtained results showed that the polymer monoliths exhibit both typical reversed-phase and ion-exchange interaction mechanism.