Determination of trace elements in human nails by an energy-dispersive XRF spectrometer equipped with 3-D polarized optics and its application for elemental monitoring

The study investigated a technique for analyzing trace elements in human nails using an energy-dispersive X-ray fluorescence spectrometer with three-dimensional polarized optics. Nails were frozen and ground using 5 mm diameter zirconia balls to obtain a fine powder. This powder was pressed into a tablet and subjected to XRF analysis. Eight elements (P, S, Cl, K, Ca, Fe, Cu, Zn) were detected in the fingernails and toenails within about 10 minutes by using secondary target materials (titanium and germanium). The concentrations of these elements were monitored for three individuals for approximately 18 months. The concentration ranges for each element were: P; 50-150 mg/kg, S; 20,000-40,000 mg/kg, Cl; 250-2,500 mg/kg, K; 100-2,500 mg/kg, Ca; 100-1,000 mg/kg, Fe; 1-3 mg/kg, Cu; 2-8 mg/kg, and Zn; 50-250 mg/kg. The concentration variation of Ca in fingernails was less than that in toenails. Similar variations in concentrations were observed for Cl and K. Thus, we demonstrated that it is possible to monitor trace elements in nails over time using a small amount of sample (approximately 10 mg). In addition, the stable isotope ratios δ¹³C, δ¹⁵N, and δ³⁴S were measured in the fingernails and toenails of five individuals. The results showed that the isotope ratios of the fingernails and toenails of the same person were approximately similar, and there were individual-dependent variances in their analytical values. (author)