| Mixed mode chromatography(mixed-mode chromatography,MMC)is a selective and adjustable chromatographic technique with high resolution and large sample loading.MMC uses various forms of interaction between stationary phase and solute to achieve multi-mode chromatographic retention mechanism,so one MMC column can replace two or more traditional single-mode columns.In recent years,the number of new mixed mode chromatographic separation materials is increasing rapidly,which greatly expands the application of chromatography in the analysis and separation of complex samples.According to the different MMC stationary phase substrates and functional monomers,the types of mixed mode chromatography can be divided into double separation mode or three separation mode.Compared with single-mode chromatography,mixed-mode chromatography has good practicability,so the study of MMC has a good value of commercial production.In this study,two new mixed mode chromatographic stationary phase materials were prepared by surface initiated radical polymerization,and the prepared stationary phases were characterized in many ways.the separation effect of the multi-mode and the stability of the chromatographic column were studied in detail.This paper mainly includes the following research contents:1.Preparation and performance evaluation of reversed-phase/hydrophilic mixed mode chromatographic stationary phase:2-methacryloyl amino-histidine(MAH),was prepared by modifying L-histidine.MAH and triallyl cyanate(TAC)were polymerized to silica gel after double-bond silanization by twice free radical polymerization,and then the reversed-phase/hydrophilic mixed mode chromatographic stationary phase(Sil@TAC@MAH)was obtained after column loading.The stationary phase was characterized by elemental analysis(EA),scanning electron microscope(SEM),thermogravimetric analysis(TGA)and Fourier transform infrared spectroscopy(FT-IR).It was proved that the functional monomer was grafted successfully on the stationary phase.The separation performance of the stationary phase was investigated by reversed-phase chromatography using phenols and sulfonamides as analytes,benzoic acid compounds and nucleoside bases as analytes in hydrophilic mode,and the separation law of Sil@TAC@MAH stationary phase was explored by changing the mobile phase conditions.The stability and reproducibility of the chromatographic column were verified by repeated experiments,and the separation mechanism of Sil@TAC@MAH stationary phase was summarized by analyzing all the experimental results.2.Preparation and performance evaluation of reversed phase/hydrophilic/ion exchange mixed mode chromatographic stationary phase:3-(2-dihydroxypropyl)-1-vinyl imidazolium chloride(DiOH-Cl)imidazole ionic liquid was prepared.A new type of stationary phase(Sil@TAC@.DiOH-Cl)was synthesized by free radical polymerization of TAC and DiOH-Cl onto the surface of silica gel microspheres layer by layer through free radical polymerization.It was proved by characterization that the stationary phase was successfully synthesized.The material was used for chromatographic separation in hydrophilic mode,reversed phase mode and ion exchange mode.The results show that typical strongly polar solutes such as nucleosides,bases and vitamins can be separated in hydrophilic interaction chromatography mode,non-polar solutes such as sulfonamides,p-hydroxybenzoates and halogenated anilines can be separated successfully in reversed-phase chromatography mode,and common inorganic anions can be separated in ion exchange chromatography mode.The stability of Sil@TAC@DiOH-Cl column was verified by repeated experiments.The results show that the stationary phase is a mixed mode chromatographic packing with good stability and excellent chromatographic performance.d... |
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