DETECTION OF ISOPRENE IN EXPIRED AIR FROM HUMAN-SUBJECTS USING PROTON-TRANSFER-REACTION MASS-SPECTROMETRY

A new analytical method using proton-transfer-reaction mass spectromet ry (PTRMS) is described for the determination of trace constituents in human breath, PTRMS is sufficiently sensitive and specific that it do es not require preconcentration or separation, At its present stage of development it is capable of detecting trace constituents present in air at the part-per-billion level, These capabilities are illustrated for Isoprene, one of the most abundant endogenous hydrocarbons. Our re sults confirm recent observations of a diurnal level variation associa ted with sleep or wakefulness; a new finding is that young children ha ve mud lower levels of isoprene in breath than adults, To address the metabolic origin of human isoprene, we used PTRMS to analyze expired a ir for allylic C5 alcohols that have been proposed to be non-enzymatic precursors of isoprene, The lack of correlation between peak breath i soprene and these alcohols suggests that the hydrocarbon is formed by some other mechanism. (C) 1997 by John Wiley & Sons, Ltd.