X-ray fluorescence analysis in total reflection geometry developments and applications

Energy-dispersive x-ray fluorescence analysis in total reflection geometry is nowadays an established technique for ultra-trace elements detection. The primary beam and the reflector serving as a sample substrate are aligned almost parallelly to fulfill the conditions for X-ray total reflection. Due to that geometry, optimized conditions for excitation of the sample and emission of fluorescent radiation with an extremely low background are achieved. With the thin-film technique this very efficient method leads to detection limits of picogram in absolute amounts or concentration levels of 10-9 g/g for medium-Z-elements in aqueous solutions. Some possible suggestions for the experimental setup to perform experiments as well as a simple total reflection module which can be attached to standard X-ray tube housings are presented. Different types of collimators acting in both ways as a collimator and a high energy filter are described. The spectral distribution of the exciting beam after passing through the collimation system is measured. Spectra of various samples and typical detection limits achieved in practical applications are given. (author)