Three-Dimensional Trace Element Analysis by Confocal X-ray Microfluorescence Imaging

• Published in: Analytical chemistry (Washington) 2004-11, Vol.76 (22), p.6786-6791
• Main Authors: Vincze, Laszlo, Vekemans, Bart, Brenker, Frank E, Falkenberg, Gerald, Rickers, Karen, Somogyi, Andrea, Kersten, Michael, Adams, Freddy
• Format: Article
• Language: English
• Subjects: Analysis; Analytical chemistry; Chemistry; Exact sciences and technology; Fluorescence; Scientific imaging; Spectrometric and optical methods; Trace elements; X-rays
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac049274l

A three-dimensional (3D) variant of scanning micro X-ray fluorescence (XRF) is described and evaluated at the ID18F instrument of the European Synchrotron Radiation Facility (ESRF). The method is based on confocal excitation/detection using a polycapillary half-lens in front of the energy-dispersive detector. The experimental arrangement represents a significant generalization of regular two-dimensional (2D) scanning micro-XRF and employs a detector half-lens whose focus coincides with that of the focused incoming beam. The detection volume defined by the intersection of the exciting beam and the energy-dependent acceptance of the polycapillary optics is 100−350 μm3. Minimum detection limits are sub-ppm, and sensitivities are comparable with regular scanning XRF. Next to the reduction of in-sample single/multiple scattering, the setup provides the possibility of sample depth scans with an energy-dependent resolution of 10−35 μm in the energy range of 3−23 keV and the possibility of performing 3D-XRF analysis by simple XYZ linear scanning. This provides a suitable alternative to X-ray fluorescence tomography. The method is illustrated with results of the analysis of solid inclusions in diamond and fluid inclusions in quartz.