High resolution studies of the origins of polyatomic ions in inductively coupled plasma-mass spectrometry, Part I. Identification methods and effects of neutral gas density assumptions, extraction voltage, and cone material

Common polyatomic ions (ArO+, NO+, H2O+, H3O+, Ar2+, ArN+, OH+, ArH+, O2+) in inductively coupled plasma-mass spectrometry (ICP-MS) are identified using high mass resolution and studied using kinetic gas temperatures (Tgas) determined from a dissociation reaction approach. Methods for making accurate mass measurements, confirming ion identifications, and correcting for mass bias are discussed. The effects of sampler and skimmer cone composition and extraction voltage on polyatomic ion formation are also explored. Neutral species densities at several locations in the extraction interface are estimated and the corresponding effects of the Tgas value are calculated. The results provide information about the origins of background ions and indicate possible locations for their formation or removal.