The Preparation And Evaluation Of The Bonded Ionic Liquid Capillary Column

Ionic liquids?ILs?,formerly known as molten salts,are a class of non-molecular ionic solvents,which are completely consisted of cations and anions.And they are liquid at or close to room temperature.ILs have many particular physicochemical properties,such as excellent solubility,good thermal stability,non-flammability,negligible vapor pressure,designability et al,therefore,they are ideal materials used as stationary phase for capillary column in gas chromatography.However,the ILs were just coated onto the inner wall via dynamic or static methods,which would cause the decomposition of ILs under high temperature and then shorten the service life of capillary column.Hence,in our research,the ILs would be modified onto the inner wall via chemical reaction,forming chemical bond between ILs and inner wall.The chemical bond was very strong and not easy to be broke,which would make the stationary phase stable under high temperature and prolong the service life of capillary column to some extent.In this paper,1-methyl-3-[?3-trimethoxysilyl?-propyl] imidazolium chloride?MPIC?and 1-butyl-3-[?3-trimethoxysilyl?-propyl] imidazolium chloride?BPIC?were successfully synthesized and chemically modified onto the inner wall of capillary columns.Besides,another two capillary columns,column MPI-BF₄ and BPI-BF₄,were prepared via internal anion exchange.And then,the bonded ILs capillary columns were further evaluated through chromatographic separations of substances,thermal stability test and the determination of thermodynamic and solvation parameters,from which we can understand the interaction mechanism between the stationary phase and substances during the chromatographic separation.The experimental results indicated that all the capillary columns?column MPIC/BPIC/MPI-BF₄/BPI-BF₄?have good separation efficiency for both polar and non-polar molecules and exhibit excellent thermal stability.The results of thermodynamic parameters denoted that the interaction between the probe molecules and the ILs stationary phase was invariable over the studied temperature range.And the chromatographic retention of each probe was an enthalpy-driven process.Additionally,the interaction mechanism was different depend on the kind of probes.The LSER showed that the interaction forces between probe and the ILs stationary phase are mainly the dispersion interaction and the hydrogen bonding interaction.What's more,extending the carbon chain of substituent group on the imidazolium cation or internal anion exchange can enhance the non-polarity of ILs,which can weaken the retention of polar substances and improve the symmetry of chromatographic peak.Especially,between the two methods,the latter was better.