Depth Elemental Imaging of Forensic Samples by Confocal micro-XRF Method

摘要

Micro-XRF is a significant tool for the analysis ofnsmall regions. A micro-X-ray beam can be created in thenlaboratory by various focusing X-ray optics. Previously, nondestructiven3D-XRF analysis had not been easy because of thenhigh penetration of fluorescent X-rays emitted into the sample.nA recently developed confocal micro-XRF technique combinednwith polycapillary X-ray lenses enables depth-selective analysis.nIn this paper, we applied a new tabletop confocal micro-XRFnsystem to analyze several forensic samples, that is, multilayerednautomotive paint fragments and leather samples, for use in thencriminaliztics. Elemental depth profiles and mapping images ofnforensic samples were successfully obtained by the confocalnmicro-XRF technique. Multilayered structures can be distinguishednin forensic samples by their elemental depth profiles.nHowever, it was found that some leather sheets exhibited heterogeneous distribution. To confirm the validity, the result of anconventional micro-XRF of the cross section was compared with that of the confocal micro-XRF. The results obtained by thenconfocal micro-XRF system were in approximate agreement with those obtained by the conventional micro-XRF. Elemental depthnimaging was performed on the paint fragments and leather sheets to confirm the homogeneity of the respective layers of the sample.nThe depth images of the paint fragment showed homogeneous distribution in each layer expect for Fe and Zn. In contrast, severalncomponents in the leather sheets were predominantly localized.