Facile synthesis of zirconia-coated mesoporous silica particles by hydrothermal strategy under low potential of hydrogen conditions and functionalization with dodecylphosphonic acid for high-performance liquid chromatography

In this work, multilayer zirconia-coated silica (ZrO 2 /SiO 2 -n) microspheres were successfully produced by a straightforward hydrothermal procedure with a low concentration of Zr 4+ (5 mM) under low potential of hydrogen (pH) conditions (pH = =2). The obtained ZrO 2 /SiO 2 -n materials exhibited favorable characteristics for high-performance liquid chromatography (HPLC) separation, including high surface area and pore volume, good pore structure, narrow particle size, and pore size distribution. In addition, the zirconia coverage in the mesopores was confirmed by soaking the material in 1 M NaOH solution, with the particles showing strong resistance to the basic solution. The obtained ZrO 2 /SiO 2 -n stationary phases were packed into a fused-silica capillary tubing for the separation of alkaloids in hydrophilic interaction chromatography (HILIC) mode, and a column efficiency of 47,800 plates/m was obtained for berberine on a ZrO 2 /SiO 2 -6 micro column. The ZrO 2 /SiO 2 -6 microspheres were further modified by dodecylphosphonic acid (C 12 P-2-ZrO 2 /SiO 2 -6); the C 12 P-2-ZrO 2 /SiO 2 -6 material showed great potential for application in reversed-phase liquid chromatography (RPLC) mode. The C 12 P-2-ZrO 2 /SiO 2 -6 micro column showed a column efficiency of 55,000 plates/m for naphthalene and 51,300 plates/m for benzene.