Inductively coupled plasma-mass spectrometry: An emerging method for analysis of long-lived radionuclides

Inductively coupled plasma-mass spectrometry (ICP-MS) is a relatively new technique that can analyze for most of the elements in the periodic table at parts per billion (ng/mL) to parts per trillion (pg/mL). Already in use several years for trace analysis of stable isotopes, ICP-MS is becoming a powerful, complementary method to the counting of decay radiations for the analysis of radionuclides. Most radionuclides with half-lives longer than approximately 1x103 years can be quantitatively detected on ICP-MS instruments that have an electrothermal vaporization unit for the injection of sample aliquants. Radionuclides with half-lives greater than approximately 1x104 years can be measured routinely with greater sensitivity and more quickly by ICP-MS than by radiation counting. Examples from the literature of applying ICP-MS to radionuclides are the bioassay of uranium in urine, measurement of 237Np in soil and silt, and analysis for 99Tc in sea water, seaweed, and marine sediment. This paper discusses the instrumentation, advantages and limitations, and present and potential applications of ICP-MS for radionuclide measurements