Enantiomeric separation of alcohols by gas chromatography using cyclodextrin derivatives as stationary phases

Abstract

Enantiomeric separations of 70 alcohols were studied by means of capillary gas chromatography using heptakis(2,3-di-O-¬methyl-6-O-tert-butyldimethylsilyl)cyclomaltoheptasose (or BSiMe) and octakis(2,3-di-O-¬methyl-6-O-tert-butyldimethylsilyl)cyclomaltooctaose (or GSiMe) as chiral stationary phases. The influence of analyte structure, e.g. the type and position of substituent, alcohol chain length, the position of chiral center, and main-structure of alcohols, on retention and enantioselectivity was systematically investigated. Thermodynamic data were also calculated to clarify the strength of analyte-stationary phase interaction and enantioselectivity towards the selected group of alcohols. All of alcohols studied, except for 35F and 2oct, were successfully separated with either BSiMe or GSiMe, or both of them. Generally, BSiMe phase exhibited grater enantioseparation towards most analytes than GSiMe phase. On both columns, the structure of alcohol analytes plays an important role on separation. Changing the position of substituent or chiral center causes changes in the interaction and enantioselectivity. The type and size of substituent also significantly affect enantioselectivity. In addition to the analyte structure, the size of cyclodextrin molecules greatly affects enantioselectivity