Proton transfer reaction–mass spectrometry: online and rapid determination of volatile organic compounds of microbial origin
A proton-transfer reaction mass spectrometer based on time-of-flight mass spectrometry is described. This instrument couples a radioactive ion source and drift tube with a reflectron time-of-flight mass spectrometer. Volatile organic compounds in the gas phase with concentrations at the parts per billion by volume level can be detected in a matter of seconds, and crucially, the multichannel data acquisition in TOF-MS means that this detection sensitivity is available in all mass channels simultaneously. The typical mass resolution (m/Deltam) is in excess of 1000. The performance of the instrument is demonstrated using urban air measurements and a linear response/calibration test.