Development And Application Of Novel Open Tubular Capillary Electrochromatographic Columns

Capillary electrochromatography(CEC),as an attractive separation technique,has received extensive attention from analytical scientists due to the advantages like high separation efficiency,high selectivity and high resolution.Specifically,open-tubular capillary electrochromatographic(OT-CEC)column,as one type of separation column in CEC,has gained great attention because of the advantages like ease of column preparation,good permeability,easy for surface modification.However,it suffers from low sample capacity and phase ratio.By introducing new materials with porous layers,large surface area and good chromatographic property as stationary phase,OT-CEC columns with excellent separation performance,improved sample capacity and phase ratio can be prepared,which will be conducive to the application of CEC in the analysis of complex samples.In this work,layered double hydroxides(LDHs)and porous organic polymer layer based open-tubular capillary columns were prepared respectively and applied to the separation of various analytes.In the first part,we developed a LDHs modified OT-CEC column.LDHs is a class of clay material which possesses the advantages like high anion exchange capacity,large specific surface area,tunable mechanical structure and chemical composition,and economy.However,difficult to be immobilized in the capillary column restricts its application as the stationary phase in CEC column.In this work,based on the specific coordination interaction between metal ions in LDHs and catechol groups in polydopamine layer,bio-inspired polydopamine modification method was used for the in situ immobilization of LDHs crystal onto the inner surface of silica capillary as stationary phase.The prepared OT capillary(Co Al-LDHs@PD@capillary)column exhibited good separation performance towards several classes of neutral and phenolic compounds with high column efficiency of 1.2×10~5N/m for methylbenzene and favorable stability and repeatability.The successful preparation of Co Al-LDHs@PD@capillary column demonstrated that the LDHs can be used as stationary phase in CEC,which broadens the application of LDHs.In the second part,an itaconic acid-styrene monolithic porous layer open tubular capillary electrochromatography(PLOT-CEC)column was developed by thermal initiation of free radical polymerization method.Through utilizing the confinement effects,adjusting of the radio of reagents,choosing suitable solvents and controlling reaction time,a porous organic polymer layer with thickness of approximately 350nm and uniform structure was prepared.The prepared monolithic PLOT column exhibited excellent chromatographic separation performance towards a variety of analytes including benzenes,phenols anilines,parabens,food additives and sulfonamides,and showed high column efficiency of 1.6×10~5 N/m for phloroglucinol.In addition,the column showed good stability and reproducibility,which guaranteed its application in the analysis of various analytes.