How does it work ?
The system is built over a quadrupole mass spectrometer, but differs from an ordinary (GC-) MS system by not using EI but components from the surrounding air.
Theese are H2O, O2, NO, NO2 and NO3, which are ionized to form up till 8 precursor ions: H3O+, OH–, 02+, O–, O2–, NO+, NO2– and NO3–.
The system may therefore easily analyze components in humid air, without bias.
These are selected for passage, one at a time, through the first quadrupole, and ionize the reactants which are added in a flow tube.