Negative Reagent Ions for Real Time Detection Using SIFT-MS

Resumen

Direct analysis techniques have greatly simplified analytical methods used to monitor analytes at trace levels in air samples. One of these methods, Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS), has proven to be particularly effective because of its speed and ease of use. The range of analytes accessible using the SIFT-MS technique has been extended by this work as it introduces five new negatively charged reagent ions (O^-, OH^-, O₂^-, NO₂^-, and NO₃^-) from the same microwave powered ion source of moist air used to generate the reagent ions traditionally used (H₃O⁺, NO⁺, and O₂⁺). Results are presented using a nitrogen carrier gas showing the linearity with concentration of a number of analytes not readily accessible to positive reagent ions (CO₂ from ppbv to 40,000 ppmv, sulfuryl fluoride and HCl). The range of analytes open to the SIFT-MS technique has been extended and selectivity enhanced using negative reagent ions to include CCl₃NO₂, SO₂F₂, HCN, CH₃Cl, PH₃, C₂H₄Br₂, HF, HCl, SO₂, SO₃, and NO₂.