The Influence of Isolation Conditions on the Composition of Essential Oils Containing Linalool and Linalyl Acetate

Abstract

The essential oils of lavender and clary sage isolated by different techniques such as hydrodistillation or extraction with an organic solvent mixture, show significant differences. Systematic investigations on the stability of the major oil components, linalool and linalyl acetate, in a model system with buffered distillation water of different pH values enabled us to correlate the artifacts found in the hydrodistill ate with linalyl acetate. Whereas linalool did not decompose in the pH range 5.0–8.0, an allylic rearrangement of linalyl acetate could not be prevented even at pH 7.0.

Since it was not possible to obtain by hydrodistillation an essential oil that represented the genuine composition, the volatiles of lavender and clary sage were primarily extracted with an organic solvent mixture. The non-volatile components of the extracts (fats, waxy materials and plant pigments) may render the GC analyses difficult. We applied therefore a gas phase stripping for the isolation of the volatiles. The combination of solvent extraction and gas phase stripping yielded an essential oil, the composition of which was qualitatively and quantitatively comparable to the genuine one, since artifact formation was prevented.