In vivo studies on the long-term persistence of volatiles in the breath

The long-term persistence of five volatiles in the breath was studied to determine the effects of respiration and the physical properties of each of the volatiles. The long-term persistence of each of the volatiles in the breath was modelled successfully and used to show that the breath volatile concentration 1 min after consuming the solution was greater when panelists exhaled at a slower rate. The air-water partition coefficient (K-aw) was influential in controlling the initial stages of persistence; compounds with a higher K-aw were found to decay at a much faster rate than compounds with a low K-aw. The decay rate during the later stages was constant for all the volatiles, which indicates that the rate-limiting factor during the later stages of persistence does not depend on the individual properties of the volatiles. Copyright (C) 2004 John Wiley Sons, Ltd.