Proton transfer reaction-mass spectrometry

Breath analysis was among the earliest applications explored for proton transfer reaction-mass spectrometry (PTR-MS) when it was first developed just over a quarter of a century ago. PTR-MS retains a strong presence in breath research due to its high sensitivity, online detection capabilities, and broad dynamic range, allowing for direct real-time breath-by-breath analysis of multiple analytes simultaneously. Technological developments, particularly the introduction of a time-of-flight (TOF) mass analyzer (PTR-TOF-MS), as well as greatly improved sensitivity and ultratrace level detection limits, have pushed the boundaries of real-time breath analysis applications. This chapter introduces PTR-MS and reviews key applications and discoveries in breath and related topics, with technical highlights and prospective future developments.