Collisional dissociation in plasma source mass spectrometry: A potential alternative to chemical reactions for isobar removal

Abstract

There has been a great deal of interest over the last half-dozen years in the use of selective chemical reactions to remove problematic species from ion beams extracted from analytical plasma sources. While these chemistries are well founded in principle, they require a priori knowledge of spectral contributors and all concomitant sample species. Different chemistries are required on both the analyte and matrix-specific bases. This approach has led to the generation of instrument/analysis cookbooks very much akin to those developed for graphite furnace atomization atomic absorption spectrophotometry (GFA-AAS). In addition to chemical reactions, the organic mass spectrometry community has employed kinematic (collisional) methods to dissociate molecular ions where the production of stable fragments is achieved to yield structurally significant product spectra. In this same way, collision-induced dissociation (CID) has been employed to remove molecular isobars in inductively-coupled plasma (ICP) and glow discharge (GD) mass spectrometries. Discussed here are the results of those studies, dating back over a dozen years ago, and how they compare in practical terms with the current commercial implementation of chemical reactions. Interestingly, there have been no publications that have actually compared the use of chemical and kinematic methods on the same instrumentation to achieve selective and universal analysis schemes. This “perspectives” paper seeks to present those previous CID works to a plasma source mass spectrometry community, wherein multi-quadrupole systems are becoming commonplace, in hopes of evoking substantial experimental work and scientific debate that may pay off practical benefits to the general user.