The recently developed 3D micro X-ray fluorescence spectroscopy (3D Micro-XRF) enables three-dimensional resolved, nondestructive investigation of elemental distribution in samples in the micrometer regime. Establishing a reliable quantification procedure is the precondition to render this spectroscopic method into a true analytical tool. One prominent field of application is the investigation of stratified material. A procedure for the quantitative reconstruction of the composition of stratified material by means of 3D Micro-XRF is proposed and validated. With the procedure, it is now possible to determine nondestructively the chemical composition and the thickness of layers. As no adequate stratified reference samples were available for validation, stratified reference material has been developed that is appropriate for 3D Micro-XRF or other depth-sensitive X-ray techniques.

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Three-dimensional micro-XRF is a recently developed microprobe which facilitates three-dimensional resolved chemical analyses with a resolution of around 20 mum. Arbitrary sites or sections of samples can be investigated without the need to section specimens physically. In this paper we demonstrate the use of the microprobe in combination with a cold nitrogen gas stream for the cryogenic fixation of specimens. A 3D micro-XRF setup at the new microfocus beamline at BESSY II was equipped with a nitrogen cryogenic stream. The distribution of Ca, Fe, Zn and Cu across virtual cross sections of a water-rich sample, the root of common duckweed, could be investigated without further sample preparation. This paper demonstrates the capabilities of 3D micro-XRF under cryogenic conditions for investigations of biological specimens.