Polychromatic and Microfocused X-ray Radiation for Traceable Quantitative X-ray Fluorescence Analysis

X-ray fluorescence (XRF) analysis is used in environmental, geological, and biomedical applications for the elemental speciation of samples. Chemical or physical traceability chains are used for the quantification of the absolute elemental content within a sample; they also assess, in a reliable manner, the chemical composition of a sample to possibly meet regulatory requirements. The physical traceability chain relies on absolute knowledge of the X-ray spectral distribution used for the excitation of the XRF instrument and is currently used at synchrotron radiation facilities. We discuss the transfer of the physical traceability chain to laboratory-based X-ray sources, which are often polychromatic, with the view to generate wider application of quantitative X-ray fluorescence analysis. Furthermore, the combination with micro-focusing optics enables the extension of these capabilities to spatially resolved measurements such that samples can be investigated in more detail in cases where localized measurements are required of individual structures or of cells stemming from organic tissue.