[Preparation and evaluation of hydrophilic interaction/reversed-phase mixed-mode chromatographic packing based on polylsilsesquioxane microspheres]

Hydrophilic interaction (HILIC)/reversed-phase (RPLC) mixed-mode chromatography is widely used in separating both hydrophobic and hydrophilic compounds, but its pH range is limited which is harmful to the separation of alkaline drugs. Monodispersed and porous cysteine-modified vinyl functionalized polymethylsilsesquioxane (C-V-PMSQ) microspheres were prepared by thiol-ene click chemistry. Elemental analysis revealed that cysteine was successfully bonded to the surface of microspheres. C-V-PMSQ microspheres had excellent monodispersity, favorable chemical stability and simple preparation process. The chromatographic behavior of C-V-PMSQ stationary phase was investigated by employing several nucleosides and nucleic acids under HILIC mode and RPLC mode. Retention factors versus volume percentage of aqueous solution exhibited a U-curve, which can be evaluated as an indication for HILIC/RPLC mixed-mode behavior of the stationary phase. This new stationary phase presented stronger retention behavior when employing alkylbenzenes as evaluation system. In addition, a series of hydrophilic and hydrophobic compounds were separated at the same time using this new stationary phase. Furthermore, baseline separation for the major three active components of Chinese herbal medicine Radix Sophorae flavescentis was achieved under HILIC and RPLC modes with highly alkaline mobile phase. The excellent chemical stability and base deactivated nature make the organosilicas ideal stationary phases for the separation of basic compounds. What's more, it even can achieve two-dimensional liquid chromatography separation on an HPLC column.