Enantiomer separation of amino acids by capillary gas chromatography using cyclodextrin derivatives as chiral stationary phases

Abstract

Amino acids were derivatized to N(O)-trifluoroacetyl methyl and isopropyl esters and studied with respect to the gas chromatographic separation of their enantiomers by using capillary columns coated with four types of cyclodextrin derivatives of 6-O- tert.-butyldimethylsilyl-2,3-di-O-acetyl or n-butyryl-β- and -γ-cyclodextrin. All amino acids could be separated into enantiomeric pairs except Trp. Methyl ester derivative showed the best separation on octakis(2,3-di-O- n-butyryl-6-O- tert-butyldimethylsilyl)-γ-cyclodextrin and isopropyl esters on heptakis(2,3-di-O-acetyl-6-O- tert.-butyldimethylsilyl)-β-cyclodextrin. Pro showed complete separation as its N(O)-trifluoroacetyl isopropyl ester derivative, and the same derivative of Ala showed a very high separation factor of 1.808 at 100°C.