Preparation And Evaluation Of Zirconia-base Stationary Phase For Reversed-phase High Performance Liquid Chromatography

Mono-disperse and porous zirconia microspheres were synthesized by the improved process of polymerization-induced colloid aggregation (PICA). In this process, ZrOCl2?8H2O was used as the precursor to prepare zirconia hydrosol which had a narrow particle size distribution and high stability.The optimum process parameters were determined through our experiments. The result showed that the amount of reagents,pH,the temperature and the time affected the particle size. The dehydrating and sintering conditions of zirconia gel ball were studied critically. The concentration of zirconium oxychloride salt:1mol/L, the temperature of gel polymerization is 15oC,pH=1.5, vacuum drying under 160oC and 200oC for 12h and 24h,then calcined 3h under 700 oC. The surface morphology of the micropheres were observed by scanning electron microscopy (SEM) and field emission scanning electron microscopy (FE-SEM). The results showed that the diameter of the final zirconia spheres is from 2 to 3μm, and they have good sphericity and integrity. Nitrogen adsorption (BET) analysis showed that the specific surface area is 11.66m²/g, pore volume is in the 1.97².85cc/mg, pore size is 2¹7nm which belonges to meso-pore range. Phase compositions were mainly tetragonal and monoclinic zirconia by X-ray diffraction (XRD) analysis. Porous zirconia microspheres are satisfied as chromatographic packing materials.To further improve the preparation process and the size control of microspheres, hydrothermal method was used to make sol particles further grew up on the basis of the prepared high-quality zirconia hydrosol, then zirconia spheres were synthesized by PICA. The effects of hydrothermal conditions ( pH, temperature, time and filling ratio) on the sphericity of the zirconia spheres were discussed in details. And the particle size can be controlled by this complex process successfully. The size of zirconia microspheres could achieve 4⁶μm observed by SEM. BET analysis showed that the surface area is 11.8m² / g, pore volume is in the 1.04¹.95cc/mg, pore size is 2¹6nm which belonges to meso-pore range. The pore volume of microspheres were decreased significantly compared to those prepared by PICA directly.Carbon-18 bonded zirconia stationary phases were prepared by modifying porous zirconia particles with octadecyl dimethyl chlorosilane. Infrared spectroscopy (IR) analysis showed that octadecyl dimethyl chlorosilane and zirconia particles were connected by chemical bonding. Chemical stability of C₁₈-ZrO₂ packed column was evaluated using the strong acid, strong base mobile phase and buffer systems under different pH values. The results showed that C₁₈-ZrO₂ filler has good chemical stability and chromatographic behavior with Reversed Phase (RP) characteristics. The reversed phase chromatography separation performances of C₁₈-ZrO₂ packed column were evaluated using neutral benzene and polycyclic aromatic system and the basic compound system. And it was proved that the neutral,basic system can be separated effectively by C₁₈-ZrO₂ phase. So the separation of biological macromolecules and the alkaline substances can be explored on the foundation of this phase.