Application of PIXE, NAA and ICP techniques to the determination of trace elements in food and diet samples

The particle induced X ray emission (PIXE) technique was applied to the measurement of trace elements in total diet samples collected in Japan for estimation of their daily dietary intake. The results of PIXE were compared with instrumental neutron activation analysis (INAA) results. Concentrations of Cl, Mn and Zn by PIXE analysis agreed well with the results from INAA, but Ca, Fe and Cu concentrations varied between these two techniques. PIXE data were preliminarily compared with INAA and inductively coupled plasma-atomic emission spectrometry (ICP-AES) results 'using a type of tea sample. A little higher concentration of Cu than that by PIXE and a much lower value than that by INAA were indicated. For Zn, concentrations by PIXE and ICP-AES agreed well with each other, while INAA gave a much lower value. From those results, PIXE was demonstrated to be recommendable for the determination of Ca, Mn, Fe, Cu and Zn in the dried and homogenized diet sample, while INAA was found to be better for determining Na, Al, Cl and I, both being convenient non-destructive analytical methods. Furthermore, internal radiation doses by 137Cs and 90Sr in the average Japanese were estimated to be 2.30 μSv/a and 1.27 μSv/a, respectively, as the effective dose equivalents, using the literature data and the daily intake for K and Ca currently obtained. Moreover, ICP-mass spectrometry (MS), known for high sensitivity and selectivity, was used to determine Th and U in diet samples. (author)