Chromatographic Performance of Core Shell Particles

Chromatographic Performance of Core Shell Particles

Background of the project

In the recent development of particle technology targeted for liquid chromatography, the use of shell particles has received considerable attention. The development of core-shell particles is pivotal to modern liquid chromatography (LC) column technology. The launch of the Fused-Core® particles (Halo™) in 2006 by Advanced Material Technology (AMT) marked the beginning of a new dawn in chromatography column. The Halo is a 2.7 µm silica particle, consisting of 1.7 µm non-porous particles and 0.5 µm porous shell The Halo column generates an efficiency of 250,000 N/m equivalent to reduce plate height minimum (hmin) of 1.5 for small molecules when packed in a 4.6 mm I.D. columns. The overall particle size larger than 2 µm provides the Halo column with an advantage over the sub-2 µm particles to operate satisfactorily on conventional LC systems because of their larger inherent permeability. This advantage also allows column coupling leading to significant gain in efficiency, particularly for the separations of complex mixtures. In 2009, Phenomenex® has begun to offer silica core-shell particles of 2.6 and 1.7 µm particle diameters. The 2.6 µm consists of a 1.9 µm nonporous particles coated with a 0.35 µm porous layer of aggregated colloidal silica. Similarly, the 1.7 µm consists of a 1.3 µm solid-core covered with a 0.25 µm porous layers of silica. These columns are currently commercialized as Kinetex™. The 2.6 µm is capable of producing an efficiency of 320,000 N/m, equivalent to hmin = 1.2 when packed in a 4.6 mm I.D. column. It produces up to 200,000 N/m, equivalent to hmin ~1.9 when packed in a narrow bore column, i.e., a 2.1 mm I.D. column.

Chromatographic and mass transfer kinetic properties of three narrow bore columns (2.1 × 50 mm) packed with new core-shell 1.7 µm EIROSHELL™-C18 (EiS-C18) particles have been studied. The particles in each column varied in the solid-core to shell particle size ratio (?), of 0.59, 0.71 and 0.82, with a porous silica shell thickness of 350, 250 and 150 nm respectively. Scanning and transmission electron microscopy (SEM and TEM), Coulter counter analysis, gas pycnometry, nitrogen sorption analysis and inverse size exclusion chromatography (ISEC) elucidated the physical properties of these materials. The porosity measurement of the packed HILIC and C18 modified phases provided the means to estimate the phase ratios of the three different shell columns (EiS-150-C18, EiS-250-C18 and EiS-350-C18). The dependence of the chromatographic ...