PENTANE AND ISOPRENE IN EXPIRED AIR FROM HUMANS - GAS-CHROMATOGRAPHICANALYSIS OF SINGLE-BREATH

Both pentane and isoprene are excreted in human breath. Although penta ne is considered an index of lipid peroxidation, the significance of i soprene is unknown. Having a similar boiling point, these two hydrocar bons are difficult to separate by gas chromatography. We separated pen tane from isoprene on both a Poraplot Q and a Poraplot U column, injec ting single-breath samples directly into a gas chromatograph. The brea th samples were pressurized to 800 mmHg to increase the amount of samp le 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 significan t linear correlation (r = 0.57, P < 0.0001) between age and pentane co ncentration in expired air; isoprene showed no correlation with age or pentane concentrations. The age-related increase in pentane productio n suggests that oxidative stress may play a role in the aging process in humans. The method described should allow for rapid, inexpensive, s erial measurement of expired pentane and isoprene.