Biomedical applications of photon-induced X-ray fluorescence.

An X-ray fluorescence method for in vitro analysis of trace elements is presented. The method is characterized by the use of an X-ray tube with secondary targets as a quasimonoenergetic radiation source, and by "infinitely thin" specimens.Different aspects have been examined in order to optimize the sensitivity of the method. It is extremely important to use secondary targets as pure as possible and collimators internally covered by the same element as the secondary target. It is also important to reduce the contribution at the XRF spectrum of photons scattered by the sample, by the sample support, and by the air.Preconcentration techniques can conveniently also be used to this purpose. In this work, biological samples are preconcentrated by reducing them to ash.Typical sensitivities obtained are in the order of 1-5 ng/cm(2) in a counting time of 10(3) s for elements with atomic number ranging from 24 (chromium) to 40 (zirconium).