Pharmacognosy - medicinal plants (herbs)

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Theme V: Drug analysis methods

Drugs analysis methods

Determination of volatile oils

Essential oils are volatile constituents present in various plants and are characterized by being constituted by mixtures of terpenes, sesquiterpenes and their oxygenated derivatives and sometimes by aromatic compounds, which are volatile at room temperature and have oily appearance.

Essential oils usually contain active substances. The determination of volatile oils in the drug is performed by distillation with water, collecting the distillate in a graduated tube with a structure such as allows that the aqueous phase get separated from the oil phase and is returned to the distillation flask.


When the essential oil has a density near to the density of water or when the separation phase is difficult, it is added into the graduated tube a premeasured amount of low density solvent with appropriate boiling point (for example xylene), which allows dissolve the essential oil and facilitate the separation.

The Pharmacopoeia specifies the instrumentation required for these determinations.

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