Analysis of exhaled breath samples reveals the presence of many volatile compounds (VOCs). The VOC composition of the breath, the so-called profile, contains a variety of information including the health status condition of the organism that produced the sample. Therefore, breath can be used in diagnosing and monitoring disease and other organism, such as phenotype, diet, and exercise. Among various available for breath analysis, GC-MS provides the most extensive regard to the qualitative and quantitative presence of VOCs in breath.
Dallinga, J. W., Smolinska, A. M., & van Schooten, F. J. (2014). Analysis of volatile organic compounds in exhaled breath by gas chromatography-mass spectrometry combined with chemometric analysis. In Mass Spectometry in Metabolomics (pp. 251-263). Springer Verlag. Methods in Molecular Biology, No. 1198 https://doi.org/10.1007/978-1-4939-1258-2_16