Mercaptopropyl Functionalized Polymethylsilsesquioxane Microspheres Prepared by Co-Condensation Method as Organosilica-Based Chromatographic Packings

Imidazole-octyl mixed-mode stationary phase based on macroporous silica for the purification of ovomucoid and ovotransferrin

A process-simplified hard template approach was established to synthesize the monodisperse macroporous silica microspheres with homogeneous structures by twice alkali-thermal treatment and calcination routes. Porous vinyl-functionalized polysesquioxane microspheres (V-PMSQ) were synthesized through a hydrolyzation-polycondensation method and used as templates. The template particles with large aperture and high pore volume were obtained by adjusting the pH value and reaction time of the twice alkali-thermal reaction. After calcination, monodisperse silica microspheres with an average pore size of 30 nm, homogeneous pore structures, and narrow particle size distribution were fabricated, which can be directly used as chromatographic matrices without classification. After that, a new reversed-phase/strong anion-exchange (RP/SAX) mixed-mode stationary phase Sil-S-VOIM was prepared by bonding the 1-vinyl-3-octyl-imidazole ligands to the above silica microspheres through a "thiol-ene" click reaction. The performance of the Sil-S-VOIM column was evaluated by one acidic protein (transferrin) and two basic proteins (lysozyme, α-chymotrypsin) and compared to a single imidazole-modified Sil-S-VIM column and an octyl-modified Sil-C8 column, respectively. Due to the synergistic effect of electrostatic repulsion and hydrophobic interactions, baseline separations of the above proteins were observed only on the Sil-S-VOIM column, with resolutions of 2.55 and 2.01 between lysozyme and transferrin, and between transferrin and α-chymotrypsin, respectively, indicating good selectivity and separation ability compared with single-mode stationary phases. It was applied to the isolation of egg white samples with peaks identified by SDS-PAGE and MALDI-TOF-MS. The results showed that the selective retention and isolation of ovomucoid and ovotransferrin were successfully achieved, with yields of 78.8% and 67.2%, respectively. The protocol described in this work is simpler, faster, and has higher protein recovery. Overall, this new mixed-mode stationary phase provided a promising potential for the separation and determination of intact proteins.

High stability amino-derived reversed-phase/anion-exchange mixed-mode phase based on polysilsesquioxane microspheres for simultaneous separation of compound drugs

A series of amino-derived mixed-mode chromatographic stationary phases were synthesized based on porous mercaptopropyl-functionalized polysilsesquioxane mesoporous microspheres synthesized by a co-condensation of methyltrimethoxysilane (MTMS) and mercaptopropyltrimethoxysilane (MPTMS). Through controlling the ratio of MTMS and MPTMS, the modified stationary phases with different amino densities were prepared by a "thiol-ene" click chemistry reaction. The morphology, pore structure, and functional groups of the microspheres were characterized by scanning electron microscope (SEM), nitrogen adsorption-desorption test, Fourier transform infrared spectroscopy (FT-IR), elemental analysis, and zeta potential, respectively. The chromatographic behavior of the stationary phases was evaluated by using alkylbenzene homologs and inorganic anions as probes. The mixed-mode retention behavior and separation mechanisms for neutral, alkaline, and acidic drugs on the prepared column had been systematically studied by changing the value of pH, ionic, and solvent strength of the mobile phase. Compared with the silica-based amino-bonded column (S-NH₂), the synthesized organosilica phase exhibited higher hydrothermal stability and longer service life under high alkaline conditions. The newly synthesized phase was successfully applied to the simultaneous separation of the multiple substances in compound drugs.

Energy-efficient and environment-friendly method to prepare monodispersed silica stationary phases for simultaneous separation of compound drugs

An energy-efficient and environment-friendly approach to prepare porous monodispersed micro-sized silica particles with methyltrimethoxysilane (MTMS) as the precursor is described. The particles were synthesized by a two-step hydrolysis/condensation procedure, with post-synthetic aging and calcination for methyl group removal. They show uniform spherical morphology, narrow particle size distribution (D₉₀/₁₀, 1.2-1.6), tailored particle size (3, 5, 7 μm) and mesopore structure (10, 13 nm), which can be directly used as packing materials for HPLC without size classification. C₁₈, sulfonate, and C₁₈/sulfonate mixed-mode stationary phases were produced by a green vapor deposition method based on the synthesized silica particles. The newly synthesized C₁₈ phase exhibits mechanical stability, kinetic behavior and separation performance expected from the commercial C₁₈ column. The C₁₈/sulfonate phase exhibits prominent mixed-mode retention behavior which can be applied to the simultaneous separation of multiple substances in the compound drugs.