Application of the isopycnic kinetic plot method for elucidating the potential of sub-2 µm and core–shell particles in SFC

In this work the isopycnic method to construct kinetic plots for SFC was used to investigate the performance limits of an SFC system when using sub-2 µm fully porous particles and sub-3 µm superficially porous (core–shell) particles. This isopycnic kinetic plot method for SFC was developed and tested earlier for SFC separations on native silica with pure CO2 as mobile phase. In the current work, octadecyl based reversed phase columns were used in combination with a mobile phase that contains 10% methanol as modifier in order to study the applicability of the described methodology to assess the kinetic performance limits of experimental setups in which SFC is used and will, according to all probability, be evolving. SFC and HPLC van Deemter and kinetic plots are constructed for columns packed with fully porous particles with various diameters and for a column packed with core–shell particles. The influence of the experimental kinetic performance limits of the particle diameter and morphology in SFC is shown to be the same as in HPLC. Additionally, kinetic plot predictions were constructed for separations on 1 µm and 0.5 µm particles using the data measured on the 5 µm, 3.5 µm and 1.8 µm fully porous particles. By doing this the potential applicability of 1 µm particles on the contemporary SFC and HPLC systems was demonstrated together with the irrelevance of the use of 0.5 µm particles in SFC.