The paper outlines the advantages of the use of Inductively Coupled Plasma
Mass Spectrometry (ICP-MS) over radiometric techniques to measure natural t
horium, Th-232. Experimental parameters that must be taken into account in
the sample digestion, preparation and ICP-MS analysis of environmental (soi
ls, rocks, sediments) or workplace (thorium oxide, reference solutions) mat
erials are described. The methods presented are applied to various referenc
e materials, with the aim of providing suitable procedures to be useful for
other important thorium containing materials (such as monazite sands or we
lding electrodes). The participation in a European Commission intercomparis
on exercise is detailed and a comparison with alpha spectrometry is made. (
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