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

In this study, fast chiral separations were demonstrated using near-critica l carbon dioxide as mobile phase. Most separations were carried out in less than 1 min at 30 degreesC using 12-15 cm capillary columns packed with 5 m um porous (300 Angstrom) silica particles deactivated with 3-cyanopropyldim ethylchlorosilane and encapsulated with cyclodextrin-substituted polymethyl siloxane. The fastest separation was accomplished in 36 s. Effects of surfa ce deactivation, temperature, pressure, and restrictor internal diameter on performance were investigated. Results show that 3-cyanopropyldimethylchlo rosilane was a better deactivation reagent than polymethylhydrosiloxane. Ne ar-critical fluid chromatography, which is classified along with supercriti cal fluid chromatography (SFC) in this paper, is more suitable for fast sep aration of enantiomers than open tubular column gas chromatography (GC). SF C can be performed under low temperatures and high pressures, which allow h igh selectivity and high speed. Temperature had a significant effect on ret ention factor, selectivity, resolution, and resolution per unit time. press ure had little effect on selectivity but had a considerable effect on reten tion factor and resolution. Finally, dimensions of the linear restrictor (i n other words, the pressure at the end of the column) had a significant inf luence on speed and resolution, (C) 2000 John Wiley & Sons, Inc.