Excretion of low-molecular weight volatile substances in human breath: focus on endogenous ethanol.

This paper describes a gas chromatographic method suitable for the analysis of low-molecular endogenous volatiles in human breath. The use of an on-column gas sampling device allowed serial determinations at 10-min intervals. With a flame ionization detector and Porapak Q as stationary phase, the four major endogenous breath volatiles were methanol, ethanol, acetone, and isoprene (2-methyl-1,3-butadiene). These same compounds were present in the breath of healthy individuals and abstinent alcoholics. In 10 healthy men, the breath concentration of endogenous ethanol, methanol, and acetone ranged from 0.07 to 0.39 microgram/L, 0.21 to 0.07 microgram/L, and 0.57 to 4.01 micrograms/L, respectively. When a man drank 5 g of exogenous ethanol, the blood concentration increased 200 times above the endogenous level. This small dose of ethanol was eliminated with a half-life of 16 min.