Superficially porous particle

Packings for HPLC can be further described as either pellicular or porous. Pellicular particles are made from spherical glass beads, which are then coated with a thin layer of stationary phase. For example, a porous layer can be deposited onto the glass bead to produce a porous layer or a superficially porous particle. The porous layer can in turn be coated with liquid stationary phase or reacted to give a bonded stationary phase. Pellicular particles are generally less efficient than the porous layer of superficially porous particles. 

Figure 25-10 shows a rapid separation of proteins on superficially porous particles, which consist of a 0.25-p.m-thick porous silica layer on a 5-pm-diamctcr nonporous silica core. A stationary phase such as Clg is bonded to the thin, porous outer layer. Mass transfer of solute into a 0.25-p.m-thick layer is 10 times faster than mass transfer into fully porous particles with a radius of 2.5 pm. enabling high efficiency at high flow rate. Superficially porous particles are especially suitable for separation of macromolecules such as proteins, which diffuse more slowly than small molecules. 

Figure 7. Types of particles for modern liquid chromatography (6) (A) superficially porous particle (B) very small totally porous particle (C) totally porous...

A method of preparing superficially porous particles by depositing colloidal inorganic particles of a given size and ionic charge from aqueous dispersion onto the surface of a solid, a single monolayer of microparticles at a time, and by repeating the process, to coat the surface with any desired number of monolayers, is described in Canadian Patent No. 729,581. 

The drawing is a cross-sectional representation of a superficially porous particle made by the process of this invention. 

However, an alternative approach can be considered using superficially porous particles dp of 2.5 pm for simplicity) run at 2.5-fold higher u (or F) and the reasonable assumption that a similar efficiency increase as with changing to 1.7 pm totally porous particles occurs. As optimizing the analysis time is not the goal, the column length is increased to 250 mm by the same factor as the eluent velocity (this was practically impossible with the 1.7 pm material) was increased. The calculated result is shown as M4 and yields R = 2.5 (more than required) with the same analysis time as method Ml and still at a practically very feasible of 1000 bar. Moving on to M5 finally yields the perfect resolution R, = 2.0) combined with a 33% reduction in analysis time but still very much in the pressure comfort zone of modern UHPLC instruments (670 bar). These observations allow for three principal conclusions ... 

As superficially porous particles with diameters between 2.5 and 3 pm can provide similar efficiencies to fully porous sub-2 pm ones, they may offer best potential for kinetic resolution boost (provided the selectivity fits). 

Wang, X., Barber, W. E., and Long, W. J. 2012. Applications of superficially porous particles High speed, high efficiency or both J. Chromatogr. A 1228 72-88. 

UHPLC with sub-2 jjm particles but with a 2-3 times lower pressure [27], allowing the use of conventional HPLC systems, although to obtain good chromatographic efficiencies it is important to consider the fluidic energy of the LC system. This technology consists of columns packed with 2.6-2.7 pim superficially porous particles composed of a 1.7-1.9 jm solid inner core and a 0.35-0.5 pim porous outer core. Nowadays, this type of column technology is the main competitor of sub-2 pm columns [30]. 

Why does the superficially porous particle with a diameter of 2.7 xm in Figure 22-17 have a similar van Deemter curve to the microporous particle with a diameter of 1.8 p.m ... 

Among the bare silica materials recently introduced, the core-shell particles, also called superficially porous particles, of sub-3-pm diameter have generated a... 

E. 8 Schematic of a Poroshell superficially porous particle. Reprinted from J. J. Kirkland, F. A. Truszkowski, C. H. EMlks Jr., and G. S. Engel Superficially porous silica microspheres for fast high-performance liquid chromatography of macro-molecules, J. Chromatogr. A, 890 (2000) 3-13, Copyright 2000 with permission from Elsevier Science... 

In 2007, an unexpected turn came for the industry with the introduction of superficially porous particles (SPP), typically in the range of 2.7 pm. With these column packings, laboratories could achieve near-UHPLC separations without needing the capital investment of new instrumentation (17-21). The attractiveness of these... 

UHPLC to Superficially Porous Particle HPLC Columns... 

It is still unclear whether this is due to the particle size distribution (PSD) of shell particles, which is significantly narrower than that of fully porous particles (Figure 5.9). Some recent smdies, which focused on particles with a different design such as the superficially porous particles, have suggested that particles displaying a very narrow PSD can lead to unprecedented low minimal plate heights (60, 67). It is. 

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