Fast chiral separations using packed capillary columns and near-critical fluid carbon dioxide mobile phase

Abstract

In this study, fast chiral separations were demonstrated using near-critical carbon dioxide as mobile phase. Most separations were carried out in less than 1 min at 30°C using 12–15 cm capillary columns packed with 5 μm porous (300 Å) silica particles deactivated with 3-cyanopropyldimethylchlorosilane and encapsulated with cyclodextrin-substituted polymethylsiloxane. The fastest separation was accomplished in 36 s. Effects of surface deactivation, temperature, pressure, and restrictor internal diameter on performance were investigated. Results show that 3-cyanopropyldimethylchlorosilane was a better deactivation reagent than polymethylhydrosiloxane. Near-critical fluid chromatography, which is classified along with supercritical fluid chromatography (SFC) in this paper, is more suitable for fast separation of enantiomers than open tubular column gas chromatography (GC). SFC can be performed under low temperatures and high pressures, which allow high selectivity and high speed. Temperature had a significant effect on retention factor, selectivity, resolution, and resolution per unit time. Pressure had little effect on selectivity but had a considerable effect on retention factor and resolution. Finally, dimensions of the linear restrictor (in other words, the pressure at the end of the column) had a significant influence on speed and resolution. © 2000 John Wiley & Sons, Inc. J Micro Sep 12: 454–461, 2000