Fused-core silica particles

It should be mentioned that there is another type of relatively new column that is made from the 2.7-pm fused-core silica particles, bonded with C18 alkyl chains, by fusing a 0.5-pm porous silica layer onto 1.7-pm non-porous silica cores. The selectivity of the fused-core particle columns is very similar to that of certain <2-pm C18 columns and has the advantage of a substantially lower back-pressure at much higher flow rates, which allows rapid separations to be performed even routinely on a conventional LC system without significant loss in efficiency or resolution. The fused-core columns are new to antibiotic analysis and may serve as good alternatives to <2-pm columns in the field. 

Abrahim A, Al-Sayah M, Skrdla P, Bereznitski Y, Chen Y, Wu N, Practical comparison of 2.7 p.m fused-core silica particles and porous sub-2 p.m particles for fast separations in pharmaceutical process development, J. Pharmaceut. Biomed.Anal. 2010 51(1) 131-137. 

Schuster SA, Boyes BE, Wagner BM, Kirkland JJ. Fast high performance liquid chromatography separations for proteomic applications using Fused-Core silica particles. J Chromatogr A 2012 1228 232-41. 

FIG. 10 SEM micrographs of (a) sUica nanoparticle/polymer [Si02/PDADMAC)3]-coated PS lat-ices and (b) hollow silica capsules. The hollow sUica capsules were obtained by calcining coated particles as shown in (a). The calcination process removes the PS core and the polymer bridging the silica nanoparticles, while at the same time fusing the silica nanoparticles together. Some of the silica capsules were deliberately broken to demonstrate that they were hollow (b). (From Ref. 106.)... 

As an alternative to wholly porous sub-2-pm particles, 1.7-pm fused-core particles surrounded by a 0.5-pm porous silica layer with 90 A pores, have emerged. In a comparative study, substantially lower back pressure was reported when the fused-core particles were used. This allowed for columns to be coupled in series, which increased the peak efficiency up to 92,750 plates (164). Wider-pore fused-core particles have an average pore diameter of 160 A. The wider-pore particles are particularly useful for increased sample loading and the rapid separation of peptides using volatile mobile phases (165). 

Figure 22-17 van Deemter curves Plate height as a function of linear flow rate (mtn/s) for microporous (Hgure 22-18) stationary phase particle diameters of 5A 3-5, and 1.8 icm. as well as superficially porous (or fused-core) particles (Rgure 22-19) with a diameter of 2.7 p.m and a 0.5- i,m porous layer thickness. Measurements for naphthalene eluted from Cu-silica (50 mm long x 4.6 mm diameter) with 60 vol% acetonitrile/40 vol% H,0 at 24 C. (Courtesy MAC-MOO Analytical, Chadds Ford, RA.]... 

Figure 22-19 shows rapid separation of proteins on superficially porous particles (also called fused-core particles), which consist of a 0.25-p.m-thick porous silica layer on a 5-p,m-diameter nonporous silica core. A stationary phase such as C]g is bonded throughout the thin, porous outer layer. Diffusion of solute into a... 

Core-shell silica or fused-core particle (depending on manufacturer) 2.7 pm (1.7-pm solid core, 0.5-pm porous shell) (1.7-pm particles also available) Achieves UHPLC conditions with an HPLC (2.7-pm particles) Smaller 1.7-pm type used for UHPLC ... 

An elegant example of SPE method based on ion-exchange retention was used for inline preconcentration of inorganic anions. A single capillary containing a preconcentration zone (adsorbed layer of cationic latex particles) and a separation zone (fused-silica modified by adsorption of a cationic polymer) was used. Analytes were retained in the preconcentration zone and eluted isota-chophoretically into the separation zone by means of an eluotropic gradient. This approach was used to determine nitrate in Antarctic ice cores at the 2.2-11.6 p,g L" level. 

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