Retention indices for naturally-occurring chiral and achiral compounds on common gas chromatography chiral stationary phases

Abstract

Chiral gas chromatography columns were initially developed for enantiomeric separations, however, they are increasingly being used for routine analyses of natural samples which also include many achiral compounds. Retention index (RI) data have been essential in the identification of natural compounds using standard columns when authentic standards are not available, but scarce RI information exists for chiral columns. In this work, we present linear RI data for 81 compounds (chiral and achiral) commonly found in biological samples for the two most common chiral stationary phases, Cyclodex-B and CycloSil-B, calculated with an alkane hydrocarbon series. In addition, we compared the resolution of various isomer pairs between the two chiral stationary phases and found better overall performance with CycloSil-B. Finally, we tested the applicability of our data set by calculating RI values for numerous compounds in leaf extracts of two Monarda fistulosa chemotypes on both columns and found good agreement. We discuss the relevance of chiral chromatographic retention data in a chemical ecology framework and call for the development of a comprehensive chiral RI database.