ENANTIOMER SEPARATION BY COMPLEXATION GAS AND SUPERCRITICAL-FLUID CHROMATOGRAPHY ON IMMOBILIZED POLYSILOXANE-BONDED NICKEL(II) HEPTAFLUOROBUTANOYL)-10-METHYLENE-(1R)-CAMPHORATE] (CHIRASIL-NICKEL)

The synthesis of a polysiloxane containing chemically bonded chiral me tal complex derived from nickel(II) heptafluorobutanoyl)-10-methylene- (1R)-camphorate] (Chirasil-nickel) and its effective immobilization on the inner surface of fused-silica capillaries by thermal treatment is described. As expected, the immobilization properties were found to b e dependent on the content of residual reactive Si-R groups in the pol ymer backbone (R = OCH3, H). The immobilized Chirasil-nickel stationar y phase was employed for the analytical enantiomer separation of coord inating solutes by high-resolution capillary gas and supercritical flu id chromatography. The increase in the relative retention monitored fo r racemic test solutes after rinsing the columns indicates a slight in crease in the effective complex concentration which does not affect th e chiral separation factor alpha. The temperature limit of analysis wa s raised to 170-180-degrees-C for temperature-programmed runs and to 1 40-150-degrees-C under isothermal conditions, thus extending the scope of complexation gas chromatography considerably, as demonstrated by v arious enantiomer separations performed at elevated temperatures. When Chirasil-nickel is immobilized on the inner surface of short, narrow- bore capillaries (50 mum I.D.), it can be employed in complexation sup ercritical fluid chromatography, combining the high solvation strength of supercritical carbon dioxide with the benefit of low operating tem peratures, enhancing enantioselectivity.