Ion kinetic energies in an inductively coupled plasma/mass spectrometer (ICP-MS) system have been measured with the use of a retarding potential on the analyzing quadrupole. The energies differ markedly from those previously reported in the literature. This is attributed to the elimination of any arcing of the ICP to the sampling orifice or skimmer of the ICP-MS system. In the absence of secondary discharge effects, the ion energies increase with the mass of the ion and are consistent with those expected from molecular beam sampling from a plasma with a temperature of ~5000 K and a potential of ~2 V. Ion energies are found to be virtually independent of aerosol gas flow, plasma power, and sample matrix composition, allowing independent optimization of plasma parameters and ion optics.
J. E. Fulford and D. J. Douglas, "Ion Kinetic Energies in Inductively Coupled Plasma/Mass Spectrometry (ICP-MS)," Appl. Spectrosc. 40, 971-974 (1986)