Negative Reagent Ions for Real Time Detection Using SIFT-MS

摘要

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 ? , O 2 ? , NO 2 ? , and NO 3 ? ) from the same microwave powered ion source of moist air used to generate the reagent ions traditionally used (H 3 O + , NO + , and O 2 + ). 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 (CO 2 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 CCl 3 NO 2 , SO 2 F 2 , HCN, CH 3 Cl, PH 3 , C 2 H 4 Br 2 , HF, HCl, SO 2 , SO 3 , and NO 2 .