The use of a non-equilibrated solid phase microextraction method to quantitatively determine the off-notes in mint and other essential oils

The undesirable top notes or off-notes found in mint, clary sage, and cedarwood oils could be quantitatively determined using a non-equilibrated solid phase microextraction/gas chromatography/selected ion monitoring/mass spectrometry (SPME/GC/SIM-MS) technique. Using the low threshold components, dimethyl sulfide, 2-methylpropanal, 2-methylbutanal, and 3-methylbutanal, which are associated with the off-notes of these oils, their levels could be reproducibly quantitatively determined. The highest level of off-notes was found in a sample of Scotch spearmint oil where the levels of the four constituents were, dimethyl sulfide (238 mug g(-1)), 2-methylpropanal (286 gg g(-1)), 2-methylbutanal (1048mugg(-1)) and 3-methylbutanal (1489mugg-1). These quantitative results in combination with sensory evaluations could provide for a powerful overall assessment of essential oil quality. (C) 2004 Society of Chemical Industry.