Many of our readers use XRF instruments in their daily work with Cement, Coal, and Minerals. XRF (X-ray fluorescence) is a non-destructive analytical technique used to determine the elemental composition of materials.
Our XRF Glossary offers a handy solution when you need a quick refresher of XRF terms. Here we provide definitions of some common analysis modes used in mining and an example of when they should be used. For more terms, visit the XRF Glossary.
- Compton Normalization: An XRF technique that provides the best results for a wide range of environmental testing and some mining applications, particularly when it is necessary to measure sub-percent concentrations of heavy elements in samples composed mainly of light elements. In environmental testing projects, it is often highly desirable to be able to quickly measure low concentration levels of all of the eight Resource Conservation and Recovery Act (RCRA) heavy metals (Ag, As, Ba, Cd, Cr, Hg, Pb, Se) on site and in real time.
- Fundamental Parameters (FP): For measuring samples of unknown chemical composition in which concentrations of light and heavy elements may vary from ppm to high percent levels, FP analysis is used to simultaneously compensate for a wide variety of geometric effects (including small and odd-shaped samples), plus x-ray absorption, and secondary and tertiary fluorescence effects. FP is the preferred analysis tool for mining, precious metals and all metal alloy testing applications.
- Empirical Calibration: In empirical mode, the user must first analyze known samples to obtain the count intensity, which is then plotted using off-line software to generate the calibration curve. This curve data is then put back onto the analyzer which can then be run to give immediate results. Empirical testing modes are only suited for measuring samples for which chemical compositions will fall within the narrow calibration range, and interferences (spectral and matrix) must be taken into consideration within the calibration.
An example of FP and empirical mode in action
After being identified and extracted, ore minerals are often concentrated by a variety of techniques (from mechanical separation such as screening to chemical separation including floatation and acid leaching) utilizing their physical and chemical properties. The product of such processing is a uniform and homogeneous mineral concentrate with relatively simple composition/mineralogy. Empirical Mode, also known as the UserMethod, is the most useful portable XRF method for analyzing concentrate samples considering their homogeneous composition. It is notable that the FP factory modes are general purpose modes that work well for a wide variety of sample types. The FP mode is also “standardless” and does not require known samples to obtain quantitative results. In the high concentration processed samples, the concentration of metal of interest is usually reported less than the true value if regular FP method is used. For such samples, in order to obtain accurate quantitative results, it is recommended to use the UserMethod.
Read Using Thermo Scientific Portable XRF instruments for analyzing ore concentrates and grade control, a case study demonstrating how a portable XRF analyzer using the UserMethod can often provide reliable and accurate data on concentrated mineral samples.