SPECTRAL AND NON-SPECTRAL INTERFERENCES IN INDUCTIVELY-COUPLED PLASMAMASS-SPECTROMETRY

Inductively coupled plasma mass spectrometry of environmental and biol ogical samples is often hampered by spectral and non-spectral interfer ences. 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 fl owrate is useful. Anion exchange allows the removal of most S and Cl c ontaining compounds, which are at the origin of the majority of spectr al interferences. Matrix modification, for example the addition of eth anol and subsequent optimization of the gas flow rates in a number of cases enables the reduction of the interferences to insignificant valu es. Often a mathematical correction based on isotopic signal ratios ca n be applied. Non-spectral interferences can be divided in reversible, that is occurring while the sample is being measured, and irreversibl e matrix effects, that is clogging of the nebulizer and sampling orifi ces or deposition on the torch or in the ion lens stack. The errors as sociated with non-spectral interferences can be eliminated by appropri ate calibration procedures, adapted sample preparation or limitation o f the amount of sample delivered to nebulizer, plasma and sampling dev ices, for example by the application of flow injection. Applications o f all the elimination procedures are described for the analysis of sea -water, estuarine water, soil and sewage extracts, percolate water, ur ine, serum and wine.