Fast Enantioselective Gas Chromatographic analysis with conventional inner diameter and narrow bore columns using asymmetrical persubstituted cyclodextrins(6I-VII-O-TBDMS- 3I-VII-O-ethyl-2I-VII-O-methyl-b-cyclodextrin)

One of the approaches used to meet the increasing demand for routine chiral recognition of real-world samples is to speed up enantioselective gas chromatography (Es-GC), thus increasing sample throughput, laboratory productivity and, as a consequence, reducing analysis costs. Cyclodextrin derivatives (CDs) are the most widely-used chiral selectors in Es-GC in the flavour and fragrance field [1, 2] where the enantiomeric excess and/or ratio determination is a very important task not only to define the biosynthetic pathway or the origin of a compound, but also to evaluate the authenticity of a sample or to detect frauds. Recent studies [3, 4] introduced short and narrow bore columns to speed-up Es-GC analyses with CD as chiral selectors for routine application while keeping a resolution of at least 1.5 for the investigated enantiomers to enable a correct enentiomeric excess and ratio determination. New “asymmetric” methyl/ethyl CD derivatives (6I-VII-O-TBDMS-3I-VII-O-ethyl-2I-VII-O-methyl (EtMe) / 3I-VII-O-methyl-2I-VII-O-ethyl (MeEt) b-CD) were synthesized [5] to obtain further speeding-up of Es-GC analysis. They show better enantioselectivity in terms of both enantiomer resolution and number of separated chiral compounds proving to be very useful in routine analysis of samples containing several chiral markers in a single run. In particular, a possible approach to speed-up Es-GC analyses is to seek the best trade-off between separation of the most critical peak pairs and total efficiency of the chromatographic system while optimizing analysis time with a conventional inner diameter (dc) column and then to transfer the optimised method to a shorter narrow bore column [4]. In this study this approach was applied to the analyses on the EtMe-CD of bergamot and lavender essential oils that are characterized by a large number of chiral markers and whose enantiomeric composition in a genuine oil are described in the literature [6, 7]. For both matrices analysis conditions were first optimized for a conventional 25m x 0.25 mm dc column starting from routine analysis and the resulting methods were then transferred to a shorter narrow bore column (10m x 0.10 mm). In both cases the results show a reduction in analysis time from the routine method of about 30% on the conventional dc column and of more than 65% on the narrow bore column, while keeping or increasing enantiomer separation and efficiency.