Quality control of commercially available essential oils by means of Raman spectroscopy.

The essential oils of different spices and aroma plants were investigated fast and nondestructively by means of Raman spectroscopy. The main ingredients of these oils, mostly monoterpenes and phenylpropane derivatives, were identified. A hierarchical cluster analysis shows that the oils of the investigated plants cluster chemotaxonomically, which means according to their chemical composition and not according to their botanical degree of relationship. In addition, cross-sections of anise seeds were analyzed applying the Raman mapping technique to localize and investigate the distribution of the oil in situ.