Abstract
BackgroundComprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOF MS) has been proposed as a powerful new tool for multidimensional analysis of complex chemical mixtures. We investigated GCxGC-TOF MS as a new method for identifying volatile organic compounds (VOCs) in normal human breath.MethodsSamples of alveolar breath VOCs and ambient room air VOC were collected with a breath collection apparatus (BCA) onto separate sorbent traps from 34 normal healthy volunteers (mean age = 40 yr, SD = 17 yr, male/female = 19/15). VOCs were separated on two serial capillary columns separated by a cryogenic modulator, and detected with TOF MS. The first and second dimension columns were non-polar and polar respectively.ResultsBCA collection combined with GC×GC-TOF MS analysis identified approximately 2000 different VOCs in samples of human breath, many of which have not been previously reported. The 50 VOCs with the highest alveolar gradients (abundance in breath minus abundance in ambient room air) mostly comprised benzene derivatives, acetone, methylated derivatives of alkanes, and isoprene.ConclusionsCollection and analysis of breath VOCs with the BCA-GC×GC-TOF MS system extended the size of the detectable human volatile metabolome, the volatome, by an order of magnitude compared to previous reports employing one-dimensional GC-MS. The size of the human volatome has been under-estimated in the past due to coelution of VOCs in one-dimensional GC analytical systems.
Highlights
In 1971, Linus Pauling reported a new technique for microanalysis of breath that revealed an unexpected finding: normal humans exhale a large number of volatile organic compounds (VOCs) in low concentrations [1]
The main new finding of this study was that GCxGC-TOF MS analysis of samples of normal human breath detected many more VOCs than have been previously reported using MS without separation [6] or one-dimensional gas chromatography (GC) MS [6,16] [25,26]
The extended size of the detectable human volatome may have resulted from improved separation of VOCs with 2dimensional GC compared to one-dimensional GC, and the greater sensitivity of TOF-MS compared to quadrupole MS
Summary
In 1971, Linus Pauling reported a new technique for microanalysis of breath that revealed an unexpected finding: normal humans exhale a large number of volatile organic compounds (VOCs) in low concentrations [1]. We investigated GCxGC-TOF MS as a new method for identifying volatile organic compounds (VOCs) in normal human breath. Results: BCA collection combined with GC×GC-TOF MS analysis identified approximately 2000 different VOCs in samples of human breath, many of which have not been previously reported. Conclusions: Collection and analysis of breath VOCs with the BCA-GC×GC-TOF MS system extended the size of the detectable human volatile metabolome, the volatome, by an order of magnitude compared to previous reports employing one-dimensional GC-MS. The size of the human volatome has been under-estimated in the past due to coelution of VOCs in one-dimensional GC analytical systems
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