| High performance liquid chromatography is one of the most widely used separation and analysis techniques,and the stationary phase is also an important factor that determines its separation effect.Therefore,the development and research of new stationary phases are very important for the development of high performance liquid chromatography.However,due to the increasing complexity of the separation samples faced in the separation analysis work,traditional single-mode chromatography is difficult to meet its separation requirements.As a supplement to single-mode chromatography,mixed-mode chromatography can achieve multiple retention mechanisms on a single column.It also has the advantages of good selectivity,large adsorption capacity,wider application range,and lower analysis cost.It has great potential in the separation and analysis of complex samples,so research and development of mixed-mode stationary phases has become one of the important topics in the field of chromatography today.Because of their excellent physicochemical properties,ionic liquids can be introduced into the stationary phase as functional groups to provide a variety of interactions for chromatographic separation.At present,they have attracted extensive attention in the field of stationary phase research.In this paper,using imidazole ionic liquid as ligand and silica gel as matrix,three hydrophilic/reverse phase/ion exchange interaction mixed-mode stationary phases were prepared by thiol-ene chemistry,and their corresponding chromatographic evaluations were carried out.（1）An ionic liquid functionalized silane reagent and a carboxyl-functionalized silane reagent were prepared by photoinitiated thiol-ene chemistry,respectively.Then the two silane reagents were simultaneously grafted onto the surface of silica by one-step bonding method.The stationary phase with ionic liquid as ligand was evaluated by chromatography.Firstly,the effects of mobile phase（water content,pH,and salt concentration）on chromatographic retention were investigated with different analytes.The results showed that the stationary phase had multiple retentions mechanism:hydrophilic,hydrophobic and ion exchange interactions.The prepared column was compared with commercial C18 column and hydrophilic amino column by linear solvation energy equation.The various interactions within the chromatographic system have been quantitatively analyzed,such as hydrogen bonding interaction,π-πinteraction,dipole-dipole interaction,electrostatic interaction,etc.Thermodynamic studies were carried out using the Van’t Hoff equation,and the effect of temperature on chromatographic retention was investigated.The results showed that the retention mechanisms between the compounds with different properties and the stationary phase may have large differences.Finally,the prepared column achieved baseline separation of compounds with different properties（sulfonamides,nucleoside bases and inorganic anions）under three modes of reversed-phase/hydrophilic/ion-exchange chromatography,showing good separation performance.（2）Ionic liquids and carboxyl functionalized ligands were bonded to the surface of silica by polymerization modification.Two ionic liquid stationary phases with alkyl chains of different lengths were prepared and compared and evaluated.Firstly,the effects of chromatographic conditions（water content,pH,and salt concentration of mobile phase）on the retention behavior of the two stationary phases were investigated.The results showed that the two stationary phases exhibited the properties of hydrophilic/hydrophobic/ion exchange interactions mixed-mode chromatography.The column efficiency(35000-70000m-1)and reproducibility（RSD<0.7%）of the two stationary phases were investigated,and they all showed satisfactory results.In the mechanism section,a thermodynamic investigation was carried out by using the Van’t Hoff plot,and the influence of temperature on the chromatographic retention behavior was discussed.The results showed that there were some differences in the retention mechanism between different solutes and stationary phases.At the same time,the two stationary phases prepared were compared with a commercial C18 column and an amino column,and their retention differences in different chromatographic systems were investigated by using varying analytes with different properties.Finally,the two stationary phases prepared were compared with a commercial mixed-mode column,and three mixtures（sulfonamide,nucleoside bases and inorganic anions）were separated under the three modes of reversed-phase/hydrophilic/ion exchange chromatography,showed better separation performance than commercial columns. |
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