X-ray fluorescence analysis (XRF) is an analytical method which has been adapted with considerable success to on-line industrial process analysis with various degrees of sophistication. Process analysis XRF systems range from relatively simple units utilizing radioisotope sources with non-dispersive analyzers to complex wavelength dispersive systems in a central location receiving samples from a number of process streams. The advantages of on-line process analytical instrumentation for quality control, regulatory 2 compliance and safety considerations are well documented. ' Advances in the development of low maintenance thermoelectrically cooled Si(Li) detectors have made energy dispersive X-ray fluorescence analysis (EDXRF) even more amendable to on-line process analysis. EDXRF is an important method of on-line instrumentation because of its ability to simultaneously detect many elements.