Determination of thorium and uranium in biological samples by inductively coupled plasma mass spectrometry using internal standardisation

Abstract

The Th and U contents of six typical biological samples (for example US NIST SRMs and Japan NIES CRMs) were determined by inductively coupled plasma mass spectrometry (ICP-MS). The internal standardisation method was adopted to compensate for non-spectroscopic interferences arising from matrix elements in the sample solution. Bismuth and TI were chosen as the internal standards, and the effect of the matrix on the behaviour of their signals was monitored by adding several elements to the NIST human lung sample. It would appear that elements of similar mass give similar signal responses, thus In is unsuitable as the internal standard in this instance. After correction by either Bi or TI internal standardisation, the results for the Th and U concentrations agreed well with literature values, showing that both are applicable for the determination of Th and U in biological samples.