Highly stable high performance liquid chromatography stationary phase based on direct chemical modification of organic bridges in hybrid silica

Abstract

Highly monodisperse 1,4-dimethoxybenzene-bridged organic/inorganic hybrid mesoporous spheres were synthesized by condensation of 1,4-dimethoxy-2,5-bis(triethoxysilyl)benzene using dodecylamine (DDA) and cetyltrimethylammonium bromide (CTAB) as co-templates. The spherical hybrid particles, which have specific surface area of 509 m²/g, pore volume of 0.8 cm³/g and average pore size of 63 Å, were characterized by elemental analysis, SEM, TEM, small angel X-ray scattering, Raman, FT-IR and nitrogen adsorption-desorption analysis. The hybrid material was further chemically modified with C12 chain group via formation of C-O-R bond, which is believed to be far more stable than traditional Si-O-Si bonding type at low pH condition. At the same time, the hybrid silica substrate has been proved to possess the improved chemical stability at high pH. In this way, combination of the hybrid silica substrate and this advanced modification method enable the stationary phase to be used in extended pH range. The chemical stability of this surface modified 1,4-dimethoxybenzene-bridged hybrid stationary phase was evaluated both at low pH (pH=0.95) and high pH (pH=11.0). Some acidic and alkaline pH chromatographic evaluations were performed to illustrate the advantages of the improved chemical stability of this packing material.