Authenticity control on lemon essential oils employing Gas Chromatography–Combustion-Isotope Ratio Mass Spectrometry (GC–C-IRMS)

Gas Chromatography–Combustion-Isotope Ratio Mass Spectrometry (GC–C-IRMS) can provide information useful to discriminate among essential oils of different geographical origin and to reveal frauds on essential oils by addition of synthetic or natural compounds from different botanical origin. The present work reports the combination of information obtained by GC–C-IRMS, Enantioselective Gas Chromatography (Es-GC), high resolution Gas Chromatography (GC-FID) and spectrophotometry (CD values). All these techniques represent useful tools to evaluate the authenticity control on lemon essential oils. The GC–C-IRMS was applied to determine the authenticity range of carbon stable isotope ratios in genuine Italian lemon essential oils industrially cold-pressed. Several commercial samples were evaluated to assess their genuineness. The IRMS results are discussed in function of the values also obtained by GC-FID, es-GC and CD values. Stable isotope ratio analysis, by GC–C-IRMS, proved to be useful to detect the presence of sophistications in lemon essential oils, even when other techniques of analysis fail. However for subtle sophistications (e.g. addition of distilled lemon oil) quality assessment must be performed by the auxiliary of more than one technique.