A versatile proton transfer reaction-mass spectrometry platform for online monitoring of VOCs.

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Proton-transfer-reaction mass spectrometry (PTR-MS) is a specialized branch of mass spectrometry that is used for online monitoring of volatile organic compounds (VOCs). Commercially available PTR-MS instruments have a response time of about 100 ms and reach a detection limit in the single digit pptv region. It uses gas phase hydronium ions as ion source reagents. This makes PTR-MS spectrometers ideally suited for rapid and sensitive analysis of VOCs in a wide range of bioscience research programmes enabled by the online, simultaneous real-time detection, monitoring and quantification of VOCs. PTR-MS uses the 'soft' ionisation technique of proton transfer from protonated water (H3O+), which is produced as an ion beam by an ion source. During this interaction a proton transfers from the hydronium to the trace gas molecule of interest that leads to a protonated and hence ionised molecule. This reaction is energetically possible for all VOCs with a proton affinity higher than that of water and is thus amenable to alkanes, alkenes, alkynes, aromatics and other organic molecules; PTR-MS therefore provides good coverage of the volatilome. This coverage can be further enhanced with the use of different reagent gases; this is available via fast switching and includes O2+, NO+, Kr+ and Xe+. Furthermore, combining the unique PTR ionisation with Time-of-Flight MS permits for high-sensitivity and high-resolution detection. PTR-MS thus offers major advantages over current analysis methods and it meets many of the demands of contemporary bioscience programmes such as rapid continuous monitoring.The ability to monitor chemical diversity of the volatilome in situ and in real-time provided by the requested PTR-MS platform will provide major new insights towards our understanding of the underpinning mechanisms of biological systems. This aligns with BBSRC strategic priorities by underpinning research programmes that tackle major challenges in synthetic biology, bioenergy, food nutrition and health, integrative microbiome research and strategic approaches to industrial biotechnology (IB).