Effect of pore size on speed of chiral separations using packed capillary column SFC

Abstract

β-Cyclodextrin polysiloxane-encapsulated 10-μm silica particles with pore sizes of 80, 300, and 1400 Å were prepared for evaluation in packed capillary column supercritical fluid chromatography with neat carbon dioxide as the mobile phase. The effects of pore size on linear velocity, retention, selectivity, efficiency, resolution, and resolution per unit time were investigated. It was found that at constant pressure, the highest linear velocity was obtained for columns containing particles of 80 Å pores, followed by particles with 1400 Å and then 300 Å pores. The highest column efficiency was achieved using 1400 Å pore particles, indicating that convective mass transfer was generated by a very small portion of mobile phase flowing through the larger pores. The chiral selectivity generally increased as the pore size increased. There was no significant difference between 80 and 1400 Å pore particles in terms of resolution per unit time. Both can be used to achieve rapid separations of small enantiomers, such as (±)-1-phenylalcohol in 3 min. © 2000 John Wiley & Sons, Inc. J Micro Sep 12: 475–481, 2000