Sample mass determination using Compton- and total scattered excitation radiation for energy-dispersive x-ray...

Compton profiles and total scattered intensities have been measured to determine the total sample mass, analyzed by an x-ray probe energy-dispersive analyzer. Under photon excitation, fluorescent x rays are emitted from the trace elements in a biological matrix. From incident radiation, the number of photons which are Commpton and elastically scattered by low-atomic-number elements is directly proportional to the total specimen mass. Tissue specimen masses have been measured from Compton intensities using Zr Kalpha and Ma Kalpha excitation x rays and mass calibration standards based upon carbon scattering. This procedure has been extended to include lower-energy excitation radiation, such as Cu, where the resolution of an energy-dispersion system requires that the total scattered intensity be used to determine the sample mass. Trace element weight-fraction concentrations are determined from this scheme with precisions of 1% in 2%, relying only upon information contained in the energy-dispersive x-ray spectrum. By adjusting for the difference between tissue and corbon scattering the accuracy of the elemental weight-fraction concentrations is brought to within 10% of elemental concentrations measured by atomic absorption spectroscopy, for samples weighing up to 25 mg. In the case of heavier samples, absorption corrections are necessary to achieve this accuracy.