UC San Diego

Recent studies by Abraham et al have shown that quantitative structure-activity relationship (QSAR) can be used for prediction of odor detection thresholds. Using the vapor delivery device 8 (VDD8), an 8-station device designed to measure odor detection performance of humans, the concentration-response functions for odor detection of various fragrance materials of high potency were measured. Subjects with a normal sense of smell were tested in small groups until data were accumulated. Samples of odorant in the vapor phase were taken before and during testing to confirm that the delivered concentrations were stable. The method used was a three-alternative forced-choice procedure at each station, in ascending order of concentration. The functions generally conformed to fitted ogive curves. The chemical with the lowest odor detection threshold was Patchouli Alcohol at 0.44 ppt, and the highest was Herbane at 4.1 ppb. Using the solvation equation erected by Abraham et al, we compared and found that some of the observed values of ODTs were very close to the experimental value. While gathering data on detection, we also investigated the recognition threshold to understand any relationship between detection and recognition point. The recognition thresholds were found to be generally within a magnitude 2 to 4 times above the detection threshold