Preparation And Evaluation Of Silica Gel Matrix Stationary Phase

Silica gel has the advantages of stable chemical properties,high mechanical strength,easy control of pore structure and surface area,and easy surface modification.It is currently the most widely used chromatographic stationary phase matrix.However,the secondary effects produced by the free silanols can cause problems such as peak tailing,reduced sample loading,and dead adsorption.In this thesis,several kinds of new chromatographic stationary phases have been developed by polar copolymerization or click chemistry way.Details are as follows:A new positive charged reversed phase stationary phase was described.It was prepared by grafting silica gel with octadecyl and epoxy groups,followed by ring-opening reaction of epoxy with tertiary amine.It is aimed to solve unwanted electrostatic interaction of basic analytes due to shielding role in their separation and also enhances the ability to bear high fraction of water phase.The phase shows retention mechansims of reversed phase,hydrophilic interaction and ion exchange,illustrating high running stability.A temperature-responsive chromatographic stationary phase has been described via"thiol-ene" click chemistry.It was obtained by clicking N-isopropylacrylamide(IPAAm)and N,N-methylenebisacrylamide(MBAM)onto mercapto-functionalized silica gel.Using sole pure water as mobile phase,steroid hormones were used as probes to investigate the retention factor curve and Van’t Hoff curve at different temperatures,which proved the temperature-sensitive retention mechanism of the stationary phase.By sole pure water as mobile phase,the utility of the column has been demonstrated to determine parabens in cosmetics.The spiked recoveries under three spiked levels were in the range of 95.99%-108.35%,and their RSDs ranged from 0.08%to 2.81%(n=3).Using N-isopropylacrylamide and acrylic acid as monomers,a temperature/pH binary responsive polymer was prepared,which expanded the application range of temperature-sensitive materials.Chromatographic analysis results show that there are temperature and pH response mechanisms,which realizes the separation of steroids,parabens,small molecular bases and nucleoside bases,and provides a new idea for the separation of alkaline samples.