Determination of thorium in environmental and workplace materials by ICP-MS

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. ( C) 2000 Elsevier Science Ltd. All rights reserved.