Abstract: Clean sources of reagent ions H₃O⁺, NH₄⁺, NO⁺ and O₂⁺ were obtained in conventional proton transfer reaction mass spectrometry(PTR-MS) without any radioactive substance and any mass pre-selection. The intensity of these reagents is at 10⁵cps. Three kinds of new reagents, NH₄⁺, NO⁺ and O₂⁺ tested with some volatile organic compounds(VOCs) show different ionization characters. The isomers propanal and acetone were detected with reagent ions H₃O⁺, NH₄⁺, NO⁺ and O₂⁺. The results show that NO⁺ and O₂⁺ can discriminate propanal from acetone. New multi-reagent ions PTR-MS can detect more compounds, whose proton affinities(PA) are not always higher than that of H₂O(691.0 kJ/mol). And it is shown to be a more versatile technique than conventional PTR-MS with the potential for analysis of isocompounds.

Key words: Multi-reagent ion, Ion source, Ion-molecule reaction, Proton transfer reaction mass spectrometry(PTR-MS), Isocompound