Quantification routines for full 3D elemental distributions of homogeneous and layered samples obtained with laboratory confocal micro XRF spectrometers

Abstract

Confocal micro-X-ray fluorescence spectroscopy can be performed with laboratory spectrometers for elemental imaging with 3D resolution. Due to self-absorption inside a specimen and energy effects induced by the used polycapillary optics, interpretation of data can be challenging. Thus, quantification techniques to reconstruct sample composition and geometry are mandatory to widen the applicability of the technique to further fields of analytical chemistry. We present an analytical routine which facilitates the quantitative investigation of 3D data sets obtained with laboratory spectrometers. By fully calibrating the spectrometer parameters the procedure is generalized to be suitable for all spectrometers with known excitation spectra and polycapillary optics. Calibration and validation measurements on homogeneous and stratified samples are presented with a discussion on uncertainties and challenges. Finally, the localization of a goethite needle in a quartz matrix is presented as an example of a possible routine application.