Study on the volatilization characteristic maps of essential oils in the Aromatherapy Proficiency Examination

Abstract

We attempted to generate a volatilization characteristics map for 17 essential oils in the Aromatherapy Proficiency Examination. The essential oils examined were Juniperus communis, Boswellia carterii, Rosmarinus officinalis, Eucalyptus globulus, Citrus limon, Citrus sinensis, Citrus paradisi, Melaleuca alternifolia, Origanum majorana, Anthemis nobilis, Pelargonium graveolens, Citrus bergamia, Lavandula angustifolia, Cymbopogon flexuosus, Salvia sclarea, Mentha piperita, and Cananga odorata. The volatilization characteristics were measured using a previously developed measuring system with the two gas sensors. The first and second gas sensors were placed at distances of 15 and 30 mm, respectively, from the essential oil reservoir in a measuring tube. Measurements were conducted for 3600 s for five samples of each of the 17 essential oils. Volatilization characteristics maps were plotted using three feature indicators: the maximum value of the first sensor signal, which is equivalent to the first scent (“First”); the gradient ratio of the first and second sensor signals, which is equivalent to the delayed scent (“Delay”); and the residual rate of the first sensor signal, which is equivalent to the lasting scent (“Lasting”). The following observations were made from two volatilization characteristics maps obtained with First–Delay and First–Lasting: In the First–Delay map, the high and low vapor pressures corresponded to the top and bottom of the map, respectively. In addition, a lower vapor pressure or a larger content of the delay scent resulted in a more right-side in the First–Delay map. Moreover, we reconfirmed the close similarity between the scents of Rosmarinus officinalis and Eucalyptus globulus based on measured data from the gas sensors and their relative positions in the First–Delay map. To summarize, the volatilization characteristics for the 17 essential oils in the Aromatherapy Proficiency Examination can be inferred from the First–Delay and First–Lasting maps.