Fused Core / Core-Shell

The special thing about fused core particle technology is that the silica-based packaging material is neither non-porous nor fully porous. Instead, the particles consist of a solid core and an overlying porous shell, which acts as the actual separating layer. This shortens the diffusion paths of the analytes in the stationary phase and reduces the dead volume of the entire column. This has a positive effect on the A, B and C terms of the Van Deemter equation, which reduces the overall band broadening and increases the possible separation performance.

With the available 2.7µm core-shell phases, separation efficiencies in the range of sub-2µm particles are possible, whereby the resulting back pressure is in the range of the fully porous material of the same size. These solid-core materials are therefore equally suitable for HPLC and UHPLC systems. Further advantages are the very small particle size distribution of the packing materials and the high peak capacities that can be achieved. The disadvantage of these phases is their lower loadability compared to fully porous materials.

Due to the narrow porous shell on the non-porous core, the distances that an analyte can travel within the pores by diffusion are considerably shorter. This results in faster mass transfer, which reduces the peak width. This has a positive effect on the so-called B term of the van Deemter equation, which allows faster flow rates with high efficiency.

Due to the special production process for fused core particles, the size distribution of the fused core particles is significantly narrower compared to conventional particles. This narrower distribution ensures a lower back pressure on the one hand and a more even flow of the mobile phase around the particles on the other. This in turn means that the A term of the van Deemter equation decreases.

Due to the above-mentioned improvements in the B term through faster mass transfer and the A term through more uniform particles, the base height for fused core particles is lower. This directly results in higher bottom numbers. As the bottom height does not increase noticeably even with higher flow rates for fused core particles, these particles can also have high bottom numbers at high flow rates. Another advantage of high flow rates is the lower back pressure, which allows the use of fused core particles with high flow rates on a conventional HPLC system.