Synthesis and modification of monodisperse silica microspheres for UPLC separation of C60 and C70

Monodisperse silica microspheres with average diameters from 1 μm to 2 μm were synthesized by a modified Stöber method, in which an ethanolic solution of tetraethyl orthosilicate (TEOS) was continuously supplied to the reaction mixture containing KCl electrolyte, water, ethanol and ammonia. The effects of reactant amounts, supply rate, and reaction temperature on the microsphere morphology were investigated. After surface modification with octadecyl trichlorosilane, the obtained monodisperse C18-silica microspheres with an average diameter of 1.5 μm were applied to ultra performance liquid chromatography (UPLC) separation of fullerenes. Because of having a smaller size, the 1.5 μm monodisperse C18-silica UPLC stationary phase shows ultra high efficiency compared with the commercial C18-silica HPLC stationary phase with average diameters from 5 to 50 μm.