H3O+ is ideal for many applications as our customers have proven for more than a decade. In some cases however it can be useful to use more than one reagent ion in your PTR-MS.
By using SRI several isomeric VOC compounds can be separated and instantaneously quantified (the differentiation of isobaric compounds is already possible by using IONICON PTR-TOFMS series).
NO+ is like H3O+ a soft ionizer, ionization occurs mainly through charge transfer, whereas O2+ is found to be a less soft chemical ionization agent and can be used where proton transfer from H3O+ does not work.
NH4+ reagent ions are particularly beneficial in complex mass spectra because of higher sensitivity (less fragmentation) and higher selectivity (higher proton affinity). We developed a unique method for fast switching to/from NH4+ reagent ions without adding ammonia (patent pending).
|Another revolutionary development is the implementation of Kr+ and Xe+ as reagent ions, made available as the optional SRI+ feature for IONICON PTR-MS instruments (US Pat. 9,188,564, EP 2606505 A1).|
These reagent ions (Kr+ in particular) possess even higher ionization energies than O2+ and therefore also very important (inorganic) substances such as CH4, CO, CO2, NO2, SO2, etc. can be detected and quantified using a single IONICON instrument.
Learn more about Selective Reagent Ionization - Mass Spectrometry (SRI/SRI+) and download the new brochure:
Selective Reagent Ionization - Mass Spectrometry (SRI-MS) technology incl. SRI/SRI+ feature (0.2 MB .pdf)