Determination of Th and U in bone ash by ICP-ion source mass spectrometry

The feasibility of ICP-ion source mass spectrometry (ICP-MS) for the determination of²³²Th and²³⁸U in bone ash was studied. Bone ash samples were further decomposed with concentrated nitric acid under pressure in PTF crucibles. The resultant solution was diluted and subjected directly to the measurement with an ICP mass spectrometer. The effects of diluting and removing matrix elements on ICP-MS measurements of these nuclides were studied. The accuracy of the determinations was evaluated with the measurement of NBS Human Lung (SRM 4351) which was originally certified for alpha activities of²³²Th and²³⁸U.