Isolation of eucalyptus essential oil for GC-MS analysis by extraction with subcritical water

A method based on subcritical-water extraction (SWE) before detection and identification by GC-FID and GC-MS, respectively, has been developed for the isolation of eucalyptus essential oil. The proposed method has been compared with another based on, hydro-distillation a conventional extraction procedure. Fresh cucalyptus leaves (4g) were extracted with water at 50 bar, 150°C and 2 mL min−1 for 20 min. Hydro-distillation was performed on the same amount of leaves with 360 mL water for 3 h. After each extraction the compounds were removed from the aqueous extract by a single extraction with hexane (5 mL), detected by GC-FID, and identified by electron impact (EI) MS. The SWE-based method is clearly quicker and more efficient than the hydrodistillation-based method, because yields from the former for 11 of the 13 major compounds in the extract are higher after 20-min extraction than after hydrodistillation for 3h. This enables substantial cost savings of both energy and raw material.