Synthesis and chromatographic evaluating of the core-shell SiO2 with tunable shell thickness and application for separation of Traditional Chinese Medicine oligosaccharides

The development of core-shell materials for achieving more efficient and rapid chromatographic separations has remained a key objective in separation science. In this study, monodisperse SiO₂ particles (2–4 µm in diameter) were utilized to fabricate core-shell spheres through a combined approach involving a modified sol-gel process and a biphasic system. The synthesis employed 1,6-bis(triethoxysilyl) hexane (BTMSH), 1,2-bis(triethoxysilyl) ethane (BTEE) as a bridging agent with cetyltrimethylammonium bromide (CTAB) acting as a co-template. Notably, the shell thickness could be precisely tailored within the range of 70∼300 nm through systematic optimization of stirring rate, solvent selection, and silica precursor type. The separation of aromatics analytes was evaluated and that baseline separation was achieved for both molecules on all the columns packed n-octadecyltrichlorosilane modified core-shell silica particles with tunable shell thickness. Column efficiencies up to ∼168, 325 plates m^-1 were achieved for pyrene on the CS_X-E-C18 column (n-octadecyltrichlorosilane modified core-shell silica). In addition, a hydrophilic interaction liquid chromatography (HILIC) core-shell stationary phase that amide modified core shell silica was prepared (named as CS_X-E-AM) via an improved polymerization coating approach and applied for oligosaccharides separation. The results demonstrated that the core-shell spheres were prepared with tailored shell structure and exhibited that the column was stable and could meet the requirement for HPLC separation.