Real-time Breath Analysis using QTOF-MS

The experimental set-up has been presented in detail previously [22] (link), [23] (link), [26] (link), [27] (link). Briefly, the entrance of a commercial quadrupole time-of-flight mass spectrometer (Synapt G2S, Waters, UK) was slightly modified to allow for the admission of breath samples through a heated Teflon tube. Exhaled breath was mixed with a nano-electrospray plume (water, 0.2% formic acid), whereby some compounds present in breath were readily detected in real time. The mass spectrometer was operated in the positive ion mode. The scans were recorded using the mass-lock option, using a common mass spectroscopy (MS) contaminant as lock mass (i.e., protonated phthalic anhydride, mass-to-charge-ratio (m/z) 149.0233 [28] (link)). The data analysis work-flow is given in Fig. 1.