Recognition of Mass Spectral Interferences in Inductively Coupled Plasma-Mass Spectrometry

Abstract

Spectral-interference problems in inductively coupled plasma-mass spectrometry (ICP-MS) can be recognized by making analytical determinations at more than one mass for elements that have more than one naturally occurring isotope. If the results for the isotopes do not agree, then a spectral-interference problem is often indicated. A powerful tool that can be used to pinpoint the source of spectral interference is to compare results (even for mono-isotopic elements) and result discrepancies, sample-by-sample, with the sample composition of the suspected sources of the spectral interferent. This can be effectively carried out with the use of computer-generated bar graphs. The major elements in a sample are frequently the source of species that cause spectral-interference problems. The concentrations of the major elements in a sample may, in some cases, be more readily determined by ICP-atomic emission spectrometry (ICP-AES). When ICP-AES results for major components in a set of samples are compared to ICP-MS results of the minor components in the same set of samples, spectral interferences may be revealed. The application of this approach to the identification of spectral interferences is illustrated for the determination of Ba, Zn, Cu, and Ni in a set of ground-water samples.