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Table 5.3 Some commonly occurring spectroscopic interferences caused by molecular ions
derived from plasma gases, air and water and the sample matrix.
Molecular ion Analyte ion Nominal
interference interfered with m/z

O 2+ S + 32

N + Si + 28
NO + Si + 30
NOH + P + 31

Ar + Ca + 40
ArH + K + 41

CIO + V + 51
CaO + Fe + 56
ArO+ Fe + 56

+
ArN + Cr , Fe + 54
NaAr + Cu + 63

Ar Se + 80
2+

positive analyte ions are repelled from the ion beam by the high positive charge of the matrix ions, with
low-mass ions being relatively more affected than high-mass ions. Such interferences are usually
compensated for by using an internal standard or by separating the matrix from the analyte before
analysis. Because ICP-MS has such low detection limits it is also possible to dilute the sample to such
an extent that the interference becomes negligible.

Q. What are the two main types of interferences encountered in ICP-MS and how do they differ?

Q. Which common method could you use to eliminate both non-spectroscopic and many spectroscopic
interferences?

5.7 Applications

The applications for ICP-MS are broadly similar to those for ICP-AES, although the better sensitivity of
the former has resulted in applications such as the determination of ultra-low levels of impurities in
semiconductors and long-lived radionuclides in the environment. Also, ICP-MS is better suited to the
determination of the lanthanide series of elements in many geological applications because the mass
spectrum is much simpler than the equivalent optical spectrum.