Nonporous silica column

The nonporous spherical gels for PCHdC are often specially prepared for research purposes. However, nonporous polystyrene/divinylbenzene beads. Solid Bead, can be obtained in various particle sizes from Jordi Associates, Inc. (Bellingham, MA). Columns packed with these gels can be used for HdC of the polymers that are currently analyzed using polystyrene/divinylbenzene SEC columns. Fumed silica nanospheres are offered by Cabot (Tuscola, IL) (17), and nonporous silica (NPS) microspheres are offered by Micra Scientific, Inc. (Northbrook, IL). These nonporous silica gels may also be used for HdC. 

Oostervink, R., Kraak, J.C., and Poppe, H., Hydrodynamic chromatography of soluble macromolecules of columns packed with submicron nonporous silica particles, Am. Lab., 30(6), 24C, 1998. 

In contrast to IEX, RPLC protein separations show good efficiency using either nonporous (Wall et al., 2000) or porous (Liu et al., 2002 Millea et al., 2005) silica columns, with peak capacities of approximately 100. Although not equivalent to small molecule separations, including peptides, this performance is not the main... 

Leroy, F., Presle, B., Verillon, F. and Verette, E. Fast generic-gradient reversed-phase high-performance liquid chromatography using short narrow-bore columns packed with small nonporous silica particles for the analysis of combinatorial libraries. ]. Chromatogr. Sci. 39 487-490, 2001. 

A new analytical method, pressurized capillary electrochromatography (pCEC) with AD using 1.5 mm reversed phase nonporous silica packed columns has been developed for the rapid separation and determination of four Sudan dyes in hot chili [36]. The influence of several experimental parameters on the retention behavior has been investigated. The electrochemical oxidation of Sudans I-FV separated by pCEC can be reliably monitored with a carbon electrode at 0.95 V (vs. Ag/AgCl). Fast and efficient separation of the analytes was achieved within 7 min by pCEC under the optimum conditions. To evaluate the feasibility and reliability of this method, the proposed pCEC-AD method was further demonstrated with hot chili samples spiked with Sudan dyes. 

The main disadvantage of smaller particles is the increased back-pressure during the operation of HPLC systems. The pressure can be calculated according to Darcy s law and is inversely proportional to the square of the particle size. For example, a 33 X 4.5mm column packed with 1.5pm nonporous silica particles needed a pressure of approximately 500 bar (the Umit for most commercial pumps in HPLC units) at a flow rate of 2ml min with acetonitrile and water. A general relation between particle size, pressure drop, plate number, and analysis time is provided in Fig. 7. The assumed specific conditions for viscosity, analyte diffusivity, retention factor, and other parameters are given in the legend. Fast analysis times combined with a limited flow rate also necessitates the need for fast detector systems, small volume detection cells (small volume injection loops, yet, all these challenges have been successfully resolved. 

Packing materials for the HPLC separation of biomolecules that have not only 500-1500 A pores but also a network of 6000-8000 A transecting tunnels have been developed by Regnier. These highly porous materials, when packed into columns, permit mobile phase velocities 2-5 times higher than those for conventional wide pore silica columns. For the rapid reversed-phase separation of peptides and proteins, both small 2-yrm porous wide pore (200 A) silica and l-jxm pellicular silica microspheres packed in 3-cm columns have been developed. For a five component mixture of proteins, separation times of less than a minute were possible. Nonporous monodisperse 1.5-yj.m silica beads developed by Unger have been shown... 

FIG U RE 1.13 Gradient separation of polypeptides on silica rod column and particle-packed columns. Mobile phase velocity 4mm/s, gradient 5%-60% ACN in the presence of TFA, gradient time 5min, columns (a) silica rod column, (b) Capcellpak SG (5 pm), (c) LiChrospher WP 300 RP-18e (5 pm), (d) nonporous NPS-ODS-1 HPLC column (1.5pm) (e) polymer-based TSKgel Octadecyl-NPR (2.5pm). (Reprinted from Minakuchi, H. et al., J. Chromatogr. A, 828, 83, 1998. Copyright 1998, with permission from Elsevier.)... 

The use of column with superficially porous packing materials based on silica particles with nonporous cores is the most recently reported strategy for improving chromatographic performance. This technology, originally developed by Kirkland in the 1990s to limit diffusion of macromolecules into the pores [85], became commercially available in 2007 [86], In comparison with totally porous particles of similar diameters, the both A and C term of the Van Deemter curve are reduced [87, 88],... 

The power of fluorescence detection was illustrated on the separation of PAH s by Yan et al. [64]. The 16 U.S. EPA priority PAHs were separated in isocratic mode in less then 10 min using 100 pm I.D. columns packed with 1.5 pm nonporous octadecyl silica particles. Separation efficiencies of 750,000 plates/m were obtained when the PAHs were detected by ICFD while 300,000-400,000 plates/m were found for OCFD. 

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