Imprinted polymers for chiral resolution of (±)-ephedrine, 4: packed column supercritical fluid chromatography using molecularly imprinted chiral stationary phases

Abstract

(-)-Ephedrine-molecularly imprinted polymers (MIPs) have been successfully used as stationary phases in supercritical fluid chromatography for the separation of (±)-ephedrine enantiomers. This approach combines the simple preparation and predictable elution order of MIP stationary phases with the superior mobile phase diffusivity and low viscosity of supercritical fluid mobile phases. The optimised mobile phase comprised supercritical carbon dioxide with a modifier consisting of MeOH/isopropylamine/H(2)O 93:5:2 (v/v/v). In many cases, better resolution separations were observed compared to when liquid mobile phases were used, and better separations achieved at high sample loads, although interestingly the MIPs which work best in SFC are different from the MIPs that work best in HPLC with an amine modifier. The MIP stationary phases were stable under the conditions employed and the chromatography was reproducible. This work opens the door to exploiting MIP stationary phases in preparative SFC.