[en] An XRF method for the determination of the relative efficiency of Si(Li) detectors in an annular-source geometry using ¹⁰⁹Cd is presented. Thick specimens of pure metals and stable compounds are used and the usual computational problems associated with such efficiency determination are circumvented by employing a Monte Carlo technique. The results obtained are compared with the theoretical calculation of a model based efficiency. The deviations at lower and higher energies in the energy range between 4.5 and 17.5 keV are observed and explained. (orig.)

[en] The relative efficiencies of four Si(Li) detectors from three different manufacturers were studied. The results show that such efficiencies depend not only on the shape and size of the detector's sensitive volume but also on the collimator assembly and centralized or off-centre mounting of the crystal within the cryostat. It is therefore necessary to calibrate the XRF spectrometer in the same geometric configuration which will be used for the intended application in elemental analysis; calculated model-dependent efficiencies can be very different from experimental efficiencies. (author)

[en] The energy dispersive X-ray Fluorescence (EDXRF) technique is applied to the analysis and quantification of tin in geological samples. The Mo-target X-ray tube with La secondary target is used for excitation and the quantification of tin is done using the scattered radiation characteristic of the secondary target. This method is shown to give satisfactory accuracy of the between 2% and 5% for the analysis of tin in standard reference rock samples and between 3% and 8% for the analysis of rock samples from Karagwe tin field in Kagera region West Tanzania and Lupa gold field in Mbeya region South of Tanzania. (author)