Advantages of using NO+, O2+ and NH4+ as precursor ions
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).