CONICET | Buscador de Institutos y Recursos Humanos

Conventional x-ray fluorescence analysis (XRF) is a powerful instrumental technique for elemental quantificationof samples with a wide range of matrices coming from industry, medicine, biology, environmental andarchaeometry. The scattering of the x-ray tube excitation beam from the matrix is mainly responsible of thestrong background in XRF spectra which restricts the detection limit (DL) to a few ppm (w/w). One possiblestrategy to reduce the DL is the monochromatization of the excitation beam with a crystal monochromator. Inthis case, the optimization of the system components is strongly required to obtain the highest excitation countrate over the sample, since it is considerable reduced by the short energy band pass of the monochromator.In the present work an optical device composed by a Si(100) crystal monochromator and two parallel platesbeam guides (PPBG) was characterized and including in a conventional XRF spectrometer to improve the DLs.The PPBGs are composed by several thin glass plate reflectors placed together and separated by spacers. Insidethe gap, x-rays are transmitted by total reflection contributing to the photon flux at the output of the opticaldevice. The first PPBG reduces the divergence of the beam striking the crystal, and the second one collects themonochromatic beam that emerges from the crystal. In this way, the design of the optical device is quite compactkeeping a high photon flux at the output thanks to the wide acceptance solid angle of the PPBGs. The new XRFspectrometer was applied to the analysis of biological tissues. The first results obtained in this field are shown inthe present work where the performance of the spectrometer can be evaluated.