Preparation of high-selective HPLC packing materials based on alternating copolymer-grafted silica.

Three alternating copolymer-grafted silica stationary phases for use in high-selective RP-HPLC were prepared from two vinyl monomers selected from styrene, N-methylmaleimide, N-octadecylmaleimide, and octadecyl acrylate; they were characterized by elemental analyses, thermogravimetric analysis, diffuse reflectance infrared Fourier transform spectroscopy, and (13)C cross-polarization magic-angle spinning NMR spectroscopy. Aspects of molecular-shape selectivity were evaluated for three different columns using Standard Reference Material 869b, Column Selectivity Test Mixture for Liquid Chromatography. The best selectivity for isomer separations was obtained for the stationary phase prepared with a copolymer of octadecyl acrylate and N-octadecylmaleimide, which was able to separate 16 polycyclic aromatic hydrocarbons (Standard Reference Material 1647e) in an isocratic elution. In this paper, the effectiveness of this phase is also demonstrated by separation of tocopherol isomers.