EXTENDING THE SCOPE OF ENANTIOMER SEPARATION BY CAPILLARY SUPERCRITICAL-FLUID CHROMATOGRAPHY ON IMMOBILIZED POLYSILOXANE-ANCHORED PERMETHYL-BETA-CYCLODEXTRIN (CHIRASIL-DEX)

Immobilized polysiloxane-anchored permethyl-beta-cyclodextrin (Chirasi l-Dex) with a cyclodextrin content of approximately 30 % by weight, pr eviously employed as a versatile chiral stationary phase for the separ ation of enantiomers by GC, has been used for the separation of enanti omers by capillary supercritical fluid chromatography (SFC). A conside rable number of racemates could be resolved, e.g. aromatic alcohols, a mino alcohols (TFA derivatives), and underivatized acids. Many pharmac eutical compounds were among those analyzed, including several NSAIDs (e.g. ibuprofen and ketoprofen), a steroidal drug (norgestrel), a barb iturate (hexobarbital), and others. Among the racemates resolved were many which cannot be analyzed by GC owing to low volatility or decompo sition at elevated temperatures. For two racemates, analysis temperatu re and mobile phase density were systematically varied to give constan t analysis times or capacity factors k. Low temperatures (ca 60-degree s-C) yielded the best separation in term of separation factor, a, or r esolution, R(s), even though higher densities had to be used. In compa rison with GC, capillary SFC was able to furnish higher separation fac tors and similar resolution. The applicability of capillary SFC for th e analysis of mixtures of cyclodextrin derivatives, e.g. those used in the synthesis of Chirasil-Dex, was, furthermore, demonstrated.