Determination of thorium by ICP-MS and ICP-OES

Natural thorium (232-Th) has traditionally been measured by radiometric techniques such as alpha and gamma spectrometry. However. with both ICP-OES and ICP-MS instruments becoming relatively common in many analytical laboratories. these techniques have become more acceptable in thorium analysis. This paper will briefly describe an overview of the instrumentation currently available and the techniques themselves applied to thorium analysis. Both techniques have low detection limits and require little sample treatment after the sample digestion. Routine sample analysis time is short and spectra easy to interpret. usually giving results with low uncertainties, Whereas ICP-OES measures total thorium only, ICP-MS also offers the potential to measure other long-lived thorium isotopes (t 1/2 > 10(4) years), such as 232Th. However, other important isotopes, such as 228Th. are still out of reach for routine analysis. The main disadvantage of the techniques is the requirement for a sample digestion stage.