An inductively coupled plasma/selected-ion flow tube mass spectrometric study of the chemical resolution of isobaric interferences

An inductively coupled plasma/selected-ion flow tube (ICP/SIFT) mass spectrometer has been constructed to permit the study of the kinetics and product distributions of reactions of ICP ions with neutral reagents. This has been achieved by modifying the SIFT mass spectrometer in the Ion-Chemistry Laboratory at York University to accept ions from a commercial ICP torch assembly and atmosphere/vacuum interface (Elan Series, Perkin-Elmer SCIEX). The operation of the combined ICP-SIFT instrument is illustrated for the determination of reaction rates and product distributions for the isobaric pairs ArO+/Fe+, Ar-2(+)/Se+ and ClO+/V+ reacting with a range of neutral modifiers. The results of these measurements permit the formulation of strategies for the use of ion-molecule reactions to move/remove isobaric interferences (termed chemical resolution) and so are useful in the selection of reagent gases used in ICP-MS reaction cells implemented to improve quantitative detection limits.