Silica microparticles

Similar structures using a silica-in-carbon core-shell structure have also been synthesized [76], which afford new possibilities for nanoencapsulation. Carbon can be removed by calcination, leaving silica, and (if the positions of silica and carbon are reversed) a carbon shell can be created using NH4OH solution to dissolve the silica. The formation of silica microparticles using silanol-functionalized polystyrene latexes proceeds along similar lines (Scheme 5.16) [77]. 

Figure 2.7 Sol-gel silica microparticles biodegrade faster than commercial silica. (Reproduced from DelsiTech.com, with permission.)...

Another factor that remarkably affects the enantioresolution of given enantiomeric pairs has been shown to be the binding chemistry used for the silica immobilization of glycopeptides (see Section 2.2). This was illustrated in the case of ristocetin A, which was covalently bonded to silica microparticles by immobilization onto epoxy-activated silica under mild conditions [22], and compared with the corresponding commercially available CSP, where the macrocycle was immobilized as previously reported for vancomycin, rifamycin B, thiostrepton [7], and teicoplanin [30]. The comparison proved that immobilization of ristocetin A onto epoxy-activated silica could significantly improve the enantioselectivity and the resolution of the corresponding CSP in the separation of a-amino acids under RP conditions [22]. 

Chromatographic System Use a liquid chromatograph equipped with a 254-nm detector and a 25-cm x 4.6-mm (id) column that contains 5- to 10- xm porous silica microparticles (pPorasil, or equivalent). Set the flow rate to about 1 mL/ min. Chromatograph replicate injections of the Standard Preparation, and record the peak responses as directed under Procedure. The relative standard deviation is not more than 2.0%, and the resolution, R, between (Z)-phytonadione and ( )-phytonadione is not less than 1.5 (see System Suitability in High-Performance Liquid Chromatography under Chromatography, Appendix IIA). 

RPLC was coined). Later, Majors [5] introduced porous silica microparticles modified with alkylsilanes, a packing material that is almost exclusively used in reversed-phase HPLC today. 

Modification of pHIPE-g-PGMA with silica microparticles... 

The increase in surface area of the pHIPE is important to open up new application areas. One approach is to attach spherical particles to the surface of the monolithic material. This has been, for example achieved by electrostatic interaction between charged latex nanoparticles and a monolithic surface (62). In preliminary experiments we investigated if fimctional silica microparticles could be covalently adsorbed to the p(HIPE-g-GMA) surface so as to produce stable, functional pHIPE with an increased surface area. 

In our study (6), porcine pancreas lipase (PPL) immobilized on silica particles (narrow distributed micron particles) was employed for ring-opening polymerization of TMC. No evidence of decarboxylation occurring during the polymerization. The results showed that silica microparticles improved immobilization efficiency much more. The most preferable polymerization temperature of TMC was 100 °C during 24h polymerization. The M of the resulting polymers was significantly increased compared with that catalyzed by... 

Granular or irregular porous silica microparticles are prepared by the conventional sol-gel process, as outhned in Figure 4.2 [4,6-10]. A silica sol is initially prepared by... 

Zhang, M. and El Rassi, Z., Capillary electrochromatography with novel stationary phases II. Studies of the retention behavior of nucleosides and bases on capillaries packed with octadecyl-sulfonated-silica microparticles, Electrophoresis, 20, 31, 1999. 

Kirkland (Kirkland, J.J., Gas Chromatography 1964, A. Goldup, editor, The Institute of Petroleum, London, pp. 285-300, 1965) has described the preparation of a chromatographic support by bonding successive layers of silica microparticles to glass beads by means of very thin hbrillar boehmite films. These coated cores may be employed as chromatographic or catalysts or catalyst supports. 

SCH EME 18.1 (See color insert.) Once entrapped in hydrophilic silica microparticles, hydrophobic organic... 

FIGURE 18.2 Adsorption isotherms and pore size distribution for silica microparticles synthesized from W/0 emulsions at acid and basic pH. (a) after isotherms and (b) after distribution. (Reproduced from Barbe, C.J. et al., /. Sol-Gel Sci. TechnoL, 46, 393, 2008. With kind permission.)... 

FIGURE 18.7 Biocides are microencapsulated in silica microparticles and the particles incorporated into the coating. When water diffuses toward the metal surface to be protected, the biocide chemicals are released, providing protection for sustained periods of time. (Image courtesy of Ceramisphere, kindly reproduced from www.ceramisphere.com.)... 

The company then recently built a 1000 L pilot plant (Figure 18.9) not only to enable the production and testing of large-scale samples of doped silica microparticles, but also to generate production cost data. Commenting on sol-gel market innovation, Abraham in 2006 was writing thaH ... 

Montes, A., Gordillo, M.D., Pereyra, C., de la Rosa-Fox, N., and Martmez de la Ossa, E.J. Silica microparticles precipitation by two processes using supercritical fluids. The Journal of Supercritical Fluids 75 (2013) 88-93. 

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