Analysis of Mixtures Which Are Difficult to Separate Chemically

Abstract

One of the major areas of application of the x-ray fluorescence method is the analysis of mixtures which are difficult to separate chemically, particularly when determinations of concentrations in the range of 0.1 to 100% are required. Chemical separation is often unnecessary because spectra of the individual elements can clearly be differentiated. Coster and Hevesy (1923) were the first to detect the element hafnium in zircon on the basis of its emission spectrum. Today, it is easily possible to determine by x-ray fluorescence analysis the presence and the ratios of zirconium to hafnium in minerals, ores, refining products, and industrial materials. Powders and solid materials may be analyzed directly, or solutions and borax decompositions may be used. Internal standards are often applied to compensate for the effects of varying amounts of associated components. Owing to improved spectrometers with high-resolution crystals, proportional or scintillation counters, and pulse-height discriminators, it is now possible to resolve the undesirable overlap of the hafnium L lines by second-order zirconium K lines. Likewise, the elements niobium and tantalum can easily be determined in ores, minerals, refining products, industrial materials, and ultrapure metals.