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 spectr ometer has been constructed to permit the study of the kinetics and product distributions of reactions of ICP ions with neutral reagents. This has bee n achieved by modifying the SIFT mass spectrometer in the Ion-Chemistry Lab oratory at York University to accept ions from a commercial ICP torch assem bly and atmosphere/vacuum interface (Elan Series, Perkin-Elmer SCIEX). The operation of the combined ICP-SIFT instrument is illustrated for the determ ination of reaction rates and product distributions for the isobaric pairs ArO+/Fe+, Ar-2(+)/Se+ and ClO+/V+ reacting with a range of neutral modifier s. The results of these measurements permit the formulation of strategies f or 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 det ection limits.