Pentane and isoprene in expired air from humans: gas-chromatographic analysis of single breath

Abstract

Abstract Both pentane and isoprene are excreted in human breath. Although pentane is considered an index of lipid peroxidation, the significance of isoprene is unknown. Having a similar boiling point, these two hydrocarbons are difficult to separate by gas chromatography. We separated pentane from isoprene on both a Poraplot Q and a Poraplot U column, injecting single-breath samples directly into a gas chromatograph. The breath samples were pressurized to 800 mmHg to increase the amount of sample volume delivered to the column. In a group of 43 healthy volunteers, the concentrations of end-expiratory pentane and isoprene were 0.57 +/- 0.3 and 7.05 +/- 3.53 nmol/L, respectively. There was a significant linear correlation (r = 0.57, P < 0.0001) between age and pentane concentration in expired air; isoprene showed no correlation with age or pentane concentrations. The age-related increase in pentane production suggests that oxidative stress may play a role in the aging process in humans. The method described should allow for rapid, inexpensive, serial measurement of expired pentane and isoprene.