Chemical Processes & Instrument Development: Instruments

Proton Transfer Reaction Mass Spectrometer (PTR-MS)

PTR-MS instrument
Proton Transfer Reaction apparatus

Principle of the Measurement

Chemical ionization of volatile organic compounds (VOCs) by proton transfer from hydronium ions (H3O+), mass selected by a quadrupole mass analyzer, detected as protonated parent ion of the analyte. Compounds with a proton affinity greater than water will be protonated.

Technical Specifications

Species Measured: VOCs containing at least one functional group (all VOCs except for alkanes)
Time Response: 50 ms - 5 s per mass selected
Detection Limit: 10 - 100 pptv for 1 s measurement of most VOCs
Accuracy: +/- 20% for directly calibrated compounds


Temperature dependent reaction rate coefficients, reaction product yields, heterogeneous chemistry/uptake measurements


Jim Burkholder