The diagnostic purpose of odorant patterns for clinical applications using GC×GC

The advances in hardware components and software tools which characterized the youth of comprehensive two-dimensional gas chromatography (GC × GC) are, as a natural evolution of a novel technique, more and more associated with application-oriented studies covering a wide range of fields. In addition, the high-selectivity and separation power of GC × GC have made the technique one of the most powerful tool for untargeted analysis, especially when coupled with mass spectrometry (MS). It is in this context that this chapter is placed, and specifically in the use of odorant patterns in clinical applications, with these intended as the subset of small volatile metabolites which characterize biological samples. During the last decade, the significance of testing of volatile organic compounds (VOCs) in clinical samples has become high, holding a great potential in offering perspectives of non-invasiveness, availability, and time-effectiveness. Depending on the application, the VOCs emitted from clinical matrices can represent (I) metabolites from the altered physiological status (e.g. cancer), (II) metabolites of the infecting pathogen, (III) reflect the pathogen-induced host responses, or (IV) a combination of both. An initial examination of the analytical challenges which characterize the complexity of the samples will be described. Dedicated sample preparation techniques, as well as multidimensional chromatographic configurations hyphenated to MS will be reported. A collection on milestone papers, sorted by biomedical sample type, will also be discussed, showing the potential of the GC × GC technique in unravelling the complexity of the odorant patterns in clinical application.