Gas Chromatography-Mass Spectrometry in Odorant Analysis

Precise odorant analysis by gas chromatography (GC) with olfactometry (O) methods, especially for complex sample mixtures, relies firstly upon achieving the best possible chemical separation of the volatile components. Odorants are often sampled from the headspace into the GC, since this is where our perception of the product is usually conducted, but the total sample or a liquid extract (e.g., from a wine sample) may also be introduced into the GC. Multidimensional GC (MDGC) methods achieve higher resolution than single column GC. For complex mixtures heart-cut MDGC, where discrete subsamples of eluate are transferred from the first column separation for analysis on a second column, significantly improve resolution of the components in the heart-cut fraction. Alternatively, comprehensive two-dimensional GC (GC x GC) improves resolution for all components in the injected material, but here the second column must complete analysis of each fraction very quickly e.g., within 5 s. Both approaches have been widely studied for aroma extracts and essential oils. Integrating simultaneous olfactometry –providing sensory assessment of a compound –and mass spectrometry (MS) – providing identification of the compound – in the MDGC experiment is important. At the end of the second column, split flow of effluent to O and MS allows effective dual detection of the resolved components. This is best conducted by the heart-cut MDGC approach. Novel methods usually based on MDGC can also be used to re-combine different odor-eliciting compounds, to study synergistic effects.