Characterisation of essential oil plants from Turkey by IR and Raman spectroscopy

The essential oils obtained from various plant species (genera: Origanum, Satureja, Salvia, Sideritis, Thymus, Calamintha, Lavandula, Ziziphora and Thymbra) collected in Turkey were studied by two complementary methods, ATR/FT-IR and NIR-FT-Raman spectroscopy. The vibrational spectra of both techniques obtained from the hydro-distilled essential oils of the air-dried plant material present characteristic key bands of the individual main volatile components (e.g. carvacrol, thymol, p-cymene, γ-terpinene, camphor, 1,8-cineole, α- and β-pinene). Applying principal component analysis (PCA) to these spectral data, a clear discrimination of the different species can be frequently achieved. Hierarchical cluster analysis provides a fast, easy and reliable approach for chemotaxonomy characterisation. Both vibrational techniques described in this study have the potential to replace existing standard methods used for quality control purposes and continuous evaluation of distillation processes.