More Recent Trends in X‐Ray Fluorescence Instrumentation

Abstract

Over the past 30 years or so, the X-ray fluorescence method has become one of the most valuable methods for the qualitative and quantitative analysis of materials. Many methods of instrumental elemental analysis are available today, and among the factors that will generally be taken into consideration in the selection of one of these methods are accuracy, range of application, speed, cost, sensitivity, and reliability. While it is certainly true is that no one technique can ever be expected to offer all of the features that a given analyst might desire, the X-ray method has good overall performance characteristics. In particular, the speed, accuracy, and versatility of X-ray fluorescence are the most important features among the many that have made it the method of choice in laboratories all over the world. Both the simultaneous wavelength dispersive spectrometer and the energy dispersive spectrometers lend themselves admirably to the qualitative and quantitative analysis of solid materials and solutions. Because the characteristic X-ray spectra are so simple, the actual process of allocating atomic numbers to the emission lines is relatively simple, and the chance of making a gross error is rather small. The relationship between characteristic line intensity and elemental composition is also now well understood, and if intensities can be obtained that are free from instrumental artifacts, excellent quantitative data can be obtained. Today, conventional X-ray fluorescence spectrometers allow the rapid quantification of all elements in the periodic table from fluorine (Z = 9) and upwards. Recent advances in wavelength dispersive spectrometers have extended this element range down to carbon (Z = 6). Over most of the measurable range, accuracies of a few tenths of one percent are possible, with detection limits down to the low ppm level. SCOPE OF THE X-RAY FLUORESCENCE METHODAs was indicated in the previous section, the basis of the X-ray fluorescence technique lies in the relationship between the wavelength (or energy) of the 123 X-Ray Fluorescence Spectrometry, Second Edition