Carbon Isotopic Ratios and enantiomeric distribution of selected volatiles as parameters for quality assessment of citrus liqueurs determined by HS-SPME coupled to GC-C-IRMS and ES-GC

Enantiomeric ratios of chiral volatile components represent a useful parameter for the assessment of authenticity of essential oils and natural flavors. However seasonal variations and geographical origin generate quite wide ranges, not yet well assessed, thus rendering this tool not completely reliable by itself. Assessment of genuineness is thus often carried out by multiple analytical techniques (physico-chemical analyses, GC, es-GC, HPLC) in order to evaluate sufficient parameters to express a secure judgment. More over extraction procedures and distillation processes can drastically affect the enantiomeric ratios, due to the possible reactions, with consequent tendency to racemization of some chiral volatiles. The carbon isotope ratio on the other hand is strictly dependent on the plant biochemistry. It is not subject to seasonal variation nor to the extraction procedure used. This study has been carried out on numerous samples of different Citrus essential oils by Es-MDGC, Es-GC and GC-C-IRMS, to determine if the combination of enantiomeric ratios with the carbon isotope ratios can be effective to determine the genuineness of the samples studied. The isotope ratios of the oils extracted by distillation from the leaves were also compared with those determined from the fruit peel of the same plant, in order to determine possible similarities. In addition some food flavours were extracted by headspace SPME and analyzed by the same techniques, then the results were compared to commercially available flavoured food. In conclusion the synergy of the two analytical approaches results extremely useful for the quality assurance of the matrices investigated, drastically reducing the number of components to be investigated.