Experimental testing of a modified Fundamental Parameter equation.

X-ray fluorescence (XRF) is a nondestructive analytical technique able to detect chemical elements with atomic numbers larger than that of Na in concentrations of a few µg/g or lower. Biological XRF investigations of thin tissue samples using small X-ray beams can probe their 2D microscopic distribution of chemical elements. Conversion of experimentally-acquired signals into elemental concentrations (ECs) can enhance the scientific value of such studies and facilitates quantitative comparisons among different investigations. In our study, five resin samples of various thicknesses in the 3.7 to 6.3 mm were doped with equal ECs of Fe, Cu, Zn, As, and Se: 0.0, 9.96, 18.77, 26.7, 33.9, and 40.9 µg/g. A modified Fundamental Parameter equation was applied to the spectrometric XRF-to-scatter ratio data to compute ECs and compare them with the known values. X-ray beam photon fluence rate and detailed geometry of the excitation-detection experimental setup are not required in this approach. Computed ECs matched their known values within experimental uncertainties. Future work will focus on finding the limitations of this method, and on practical implementations to biological tissues for which bulk elemental composition is not accurately known.