Trace element study of human bone by X-ray emission analysis using an external proton beam

Abstract

A simple proton beam (PIXE) arrangement developed for a low energy accelerator was used for the determination of absolute concentrations of nine trace elements in human bone samples. The 2.4 MeV proton beam was externalized through a thin (2 μm) aluminiummylar foil. Using an air cooling system, the foil withstood a high current (0.5–1 μA) for a long time. The samples were cooled to prevent damage and volatilization of elements. The induced X-rays were detected with a Si(Li) detector and the external beam was monitored with a second detector, measuring K X-rays induced in atmospheric argon. The mean (SD) trace element levels (ppm) measured in dense bone by comparison with hydroxyapatite/standard mixtures were: Cr<2.0, Mn<2.3, Fe 7.58 (1.55), Ni<2.4, Cu 3.58 (2.16), Zn 144 (27), Pb 12.2 (2.5), Br 12.4 (5.5) and Sr 47.7 (14.3). The detection limits for these elements achieved in this work were about 1 ppm when rather short measuring times (∼10 min) were used. The coefficient of variation of a single measurement, e.g. for Zn, was 3–4%. Because of the slow turnover of dense bone, such measurements provide a means of monitoring long term trace element exposure.