MDGC-MS - A POWERFUL TOOL FOR ENANTIOSELECTIVE FLAVOR ANALYSIS

This paper reports the differentiation between the enantiomers of thea spiranes and theaspirones, potent flavor compounds widely used in the flavor industry. Optically pure reference compounds of isomeric theasp iranes were obtained by enantioselective synthesis. Enantiomerically p ure reference theaspirones were isolated from quince fruit; their abso lute stereochemistry was assigned by CD spectroscopy. For both types o f compounds the order of elution was elucidated by using authentic ref erence compounds. These data enabled the determination of the enantiom eric distribution of both types of compounds in a variety of plant tis sues. Because of the complexity of the natural flavor isolates, compou nds were identified by mass spectrometry after multidimensional gas ch romatography employing a Sichromat 2 double oven chromatograph. After separation of the target compounds on the first, achiral, column (DB-5 ), they were transferred to a chiral column (C-Dex B) for determinatio n of the enantiomeric distribution. Multiple ion detection (MID) enabl ed the determination of the enantiomeric distribution even for complex mixtures containing the target compounds at extremely low levels.