Analysis of volatile organic compounds: possible applications in metabolic disorders and cancer screening

The human breath contains a variety of endogenous volatile organic compounds (VOCs). The origin and pathophysiological importance of these VOCs is poorly investigated. Little is known about the interaction of VOCs from ambient air, such as those produced by plants and exhaust fumes, with the human organism. Gas chromatographic determination of VOC concentrations is tedious. Proton-transfer-mass spectroscopy (PTR-MS), a new technology for the online detection of VOC patterns, is a valuable alternative. We present two interesting molecular species, isoprene and ortho (o)-toluidine, as examples of endogenously produced VOCs. In a case study, breath isoprene reductions during lipid-lowering therapy (36%) were shown to correlate with cholesterol (32%) and LDL concentrations (35%) in blood (p < 0.001) over a period of 15 days. Therefore, isoprene concentrations in human breath (measured by PTR-MS) might serve as an additional parameter to complement invasive tests for controlling lipid-lowering therapy. Furthermore, it may be a useful parameter for lipid disorder screening. Mass-108, which presumably represents o-toluidine in our breath samples, was found in significantly higher concentrations in the breath of patients with different tumors (1.5 +/- 0.8 ppbv) than in age-matched controls (0.24 +/- 0.1 ppbv, p < 0.001). Inflammatory reactions do not seem to alter the pattern of mass-108. Therefore, it appears to be a currently underestimated carcinoma marker that deserves further investigation.