Proton-transfer reaction mass spectrometry (PTR-MS) is an emerging technique that has already found a wide range of applications in analytical science. It allows real-time measurements of volatile organic compounds (VOCs) in air with a high sensitivity (limit of detection several tens of ppt).
A recently developed Proton-Transfer Reaction-Time of Flight instrument with a mass-resolving power of 4000 - 5000 and a mass accuracy of 5 ppm allows for the unambiguous sum-formula identification of e.g. hydrocarbons or oxygenated VOCs (Graus et al. 2010). The co-addition of a series of stored PTR-TOF mass spectra (e.g. over a period of 10 to 30 minutes) allows us to reach a limit of detection in the ppqv range by post-experimental data processing.