GC-MS Combined with Chemometric Analysis Allows to Assess Provenance and Quality of Lavender Essential Oils

Reviewed: Beale DJ, Morrison PD, Karpe AV, Dunn MS. Chemometric analysis of lavender essential oils using targeted and untargeted GC-MS acquired data for the rapid identification and characterization of oil quality. Molecules. 2017;22(8):E1339. doi: 10.3390/molecules22081339.

Keywords: Adulteration, chemometrics, essential oil, GC-MS, HPLC-UV/Vis, Lavandula angustifolia, lavender

Essential oils have been a prime target for adulteration due to the relatively high cost of many of these oils and the ease with which essential oils can be diluted with lower-cost ingredients. A prime example for such adulteration is the essential oil of lavender (Lavandula angustifolia, Lamiaceae), which is known to be diluted or substituted with lavandin (Lavandula x intermedia) oil, or adulterated with synthetic linalool and linalyl acetate.¹ Another issue in the lavender oil trade is the sale of ingredients from Asian countries made from L. angustifolia with a less desirable odor profile, considered as material of lower quality and lesser value. The procurement of low quality oil sold as high quality lavender oil can have a substantial financial impact on manufacturers of goods containing lavender oil.

In this study 30 lavender oil samples originating from France or Bulgaria (samples from these two countries are perceived as high quality), 24 lavender oils originating from Indonesia or Cambodia (perceived as low quality), and nine additional oils of unknown origin were analyzed by gas chromatography-mass spectrometry (GC-MS). The chromatograms obtained were evaluated statistically using soft partial least squares-discriminate analysis (PLS-DA). Using principal components 1 and 2, a model was created that allowed the separation of the samples from France/Bulgaria from the Asian lavender oils, and assignment of the quality of the nine unknown materials (six being from Europe, and three from Asia).

Using statistical tools, 15 lavender oil compounds were found to be relevant for the distinction among the oils according to geographical origin. Interestingly, none of these 15 compounds could be identified using the available spectral library; therefore, additional work will need to be carried out to characterize these molecules. 

Comment: The adulteration of lavender oil seems to be quite common, and methods to detect adulteration with lavandin oil or synthetic linalool and linalyl acetate have been discussed by various authors previously.^2,3 Admixture of lavandin oil can be detected using GC by the presence of higher amounts of 1,8-cineol and camphor.² The presence of synthetic linalool and linalyl acetate can be established using chiral GC. While lavender contains (R)-linalool and (R)-linalyl acetate of high enantiomeric purity, the synthetic compounds are partially racemic. Therefore, the presence of substantial amounts of the (S)-enantiomers allows the detection of the addition of synthetic linalool and linalyl acetate.^2,3 The addition of a chemometric evaluation to a GC-MS method, described in the present paper, adds another layer of sophistication to the quality control of lavender oils, and allows for the distinguishing of these oils according to geographical origin, establishing the perceived quality (and thereby the economic value) of these oils.

References

1.     Do TKT, Hadji-Minaglou F, Antoniotti S, Fernandez X. Authenticity of essential oils. TrAC Trends in Analytical Chemistry. 2015;66:146-157.

2.     Bilke S, Mosandl A. Authenticity assessment of lavender oils using GC-P-IRMS: ²H/¹H isotope ratios of linalool and linalyl acetate. Eur Food Res Technol. 2002;214:532–535.

3.     Lis-Balchin M. Lavender essential oil: Standardisation, ISO; adulteration and its detection using GC, enantiomeric columns, and bioactivity. In: Lavender: The Genus Lavandula. Lis-Balchin M., ed. London, UK: Taylor & Francis; 2002:117-123.