Application of Conventional and Microbeam Synchrotron Radiation X-Ray Fluorescence and Absorption for the Characterization of Human Nails

The synchrotron radiation based spectroscopies X-ray fluorescence and X-ray absorption fine structure are used to detect illness-related changes in the elemental distribution and bonding environment of metals in human nails. The effective atomic number of a collection of nails is determined using two methods, the X-ray transmittance and the scattering method, and is found equal to 7.5 +/- 0.5. X-ray fluorescence maps of the elemental distributions, recorded with a lateral resolution of 5 Am, reveal that S, Ca and Zn are distributed homogeneously while Fe tends to cluster. In the Fe-rich clusters, which have a diameter in the range 15-30 mu m, the Fe concentration is 10 times higher than in the matrix. The Zn K edge X-ray Absorption Fine Structure spectra reveal that Zn, in the nails from healthy donors and patients suffering from lung diseases, is four-fold coordinated with N and S and the Zn-N and Zn-S distances are equal to 2.03 angstrom and 2.25 angstrom, respectively. Finally the signature of various bonds in the C-, O- and N- K near edge X-ray absorption fine structure spectra is discussed.