Fe distribution and speciation in human nails

Micro-X-ray Fluorescence (μ-XRF) and Fe–K edge micro-X-ray Absorption Near Edge Structure (μ-XANES) spectroscopies are applied for the study of the distribution and the spatially-resolved bonding environment of Fe in human nails. The μ-XRF maps reveal that Fe forms islands where its concentration is up to six times higher than in the rest of the sample. Comparison of the map characteristics of two nails that belong to healthy and ill donors (affected by lung cancer), reveals that there is no significant variation in the size distribution of the Fe-rich inclusions contrary to their spatial density which is found higher in the nail of the ill donor. However, a relation between the variations of the spatial density and the illness can not be established due to the small number of the studied samples. The analysis of the Fe–K μ-XANES spectra reveals that the bonding environment of Fe varies between the samples and between different spots of the same sample with different Fe concentration. The characteristics of the pre-edge peak in the Fe–K XANES spectra indicate the presence of both Fe+3 and Fe+2 that participate in the formation of distorted octahedra. Finally, the area under the pre-edge peak depends linearly on the position of the absorption edge indicating variation of the Fe ligation between the samples and/or between different spots in the same sample.