Spectral and non-spectral interferences in inductively coupled plasma mass-spectrometry

Abstract

Inductively coupled plasma mass spectrometry of environmental and biological samples is often hampered by spectral and non-spectral interferences. Spectral interferences, caused by the limited resolution of the quadrupole mass spectrometer, can be eliminated in a variety of ways. For their identification inspection of a signal versus carrier gas flowrate is useful. Anion exchange allows the removal of most S and Cl containing compounds, which are at the origin of the majority of spectral interferences. Matrix modification, for example the addition of ethanol and subsequent optimization of the gas flow rates in a number of cases enables the reduction of the interferences to insignificant values. Often a mathematical correction based on isotopic signal ratios can be applied. Non-spectral interferences can be divided in reversible, that is occurring while the sample is being measured, and irreversible matrix effects, that is clogging of the nebulizer and sampling orifices or deposition on the torch or in the ion lens stack. The errors associated with non-spectral interferences can be eliminated by appropriate calibration procedures, adapted sample preparation or limitation of the amount of sample delivered to nebulizer, plasma and sampling devices, for example by the application of flow injection. Applications of all the elimination procedures are described for the analysis of sea-water, estuarine water, soil and sewage extracts, percolate water, urine, serum and wine.