Odor detection of single chemicals and binary mixtures

Abstract

The investigation explored the olfactory detectability of two chemically and structurally similar esters, ethyl propanoate and ethyl heptanoate, presented singly and in mixtures. Initially, we measured concentration-detection (i.e., psychometric) functions for the odor of ethyl propanoate and ethyl heptanoate presented singly. Using this information, we prepared binary mixtures of the two chemicals in varying complementary proportions and, also, selected concentrations of the single compounds, such that, if a rule of response-addition (i.e., independence of detection) were to hold, the stimuli (mixed and single) should approximate equal detection. Next, we measured the actual detectability of these stimuli within the same experiment. The results were analyzed in terms of response-addition (or -additivity) and of dose-addition (oradditivity). The outcome revealed that at low levels of detectability the mixtures approximate response-addition, that is, independence of detection, whereas at high levels of detectability they approximate dose-addition. In the light of previous findings for the olfactory detection of the more dissimilar chemical pairs 1-butanol/2-heptanone and butyl acetate/toluene, we conclude that the described outcome generalizes across a variety of chemical pairs.

Revisiting psychophysical work on the quantitative and qualitative odour properties of simple odour mixtures: a flavour chemistry view. Part 1: intensity and detectability. A review.

“…On the contrary, at a detectability of 0. [51] At high detectability levels there is again a clear hypoaddition with respect to the response addition model, while at lower detectability levels, the experimental detectability of the mixture fits exactly the response-addition model Whisky lactone/isomyl acetate; whisky lactone/ethyl butyrate; guaiacol/ethyl butyrate 2005 [63] In all cases the presence of woody odorants caused a significant difference. The degree of the difference increases with the concentration.…”

“…As shown in the table, there are very early reports about mixtures of odour chemicals at threshold or sub-threshold levels. The most extensive [ 51,60,61] Intensity and detectability of odor mixtures [34] and part of it was even published in the journal Nature. [35] These authors demonstrated that the odour activity values (OAVs), or concentration/threshold ratios of mixtures of odorants at sub-threshold values are approximately additive.…”

“…[62] In the figure, the odorant with highest D is ethyl heptanote [51] and the one with the smallest D is butyric acid. [61] As shown in the figure, the former requires nearly five orders of magnitude of concentration change to become fully detectable, while the latter reaches complete detection in just one order of magnitude.…”

Processing of Odor Mixtures in theDrosophilaAntennal Lobe Reveals both Global Inhibition and Glomerulus-Specific Interactions

“…There is a long tradition in studying behavioral responses to odor mixtures both in vertebrates (Laing and Francis, 1989;Kay et al, 2003Kay et al, , 2005Wiltrout et al, 2003;Cometto-Muniz et al, 2005) and invertebrates (Derby et al, 1996;Smith, 1998;Deisig et al, 2003), and technical advances have recently allowed a physiological approach. Studies in vertebrates analyzed the peripheral level (Duchamp-Viret et al, 2003;Oka et al, 2004), the olfactory bulb (Giraudet et al, 2002;Tabor et al, 2004;Lin et al, 2005) and the olfactory cortex (Lei et al, 2006;Zou and Buck, 2006).…”

An assessment of air quality reflecting the chemosensory irritation impact of mixtures of volatile organic compounds

“…Several studies of sensory irritation thresholds (NPTs and EITs) from mixtures of VOCs have shown various levels of additivity that, to a first approximation, are not-too-far from complete additivity (Nielsen et al, 1988;Cometto-Muñiz et al, 1997;1999;2001a;2004a;2004b). So are results from studies on ODTs 2005b;Wise et al, 2007;Miyazawa et al, 2009). To extend occupational exposure limits to mixtures of VOCs, additivity of effects has been suggested (Alarie et al, 1996).…”