X-ray fluorescence (XRF) is an analytical method that utilizes X-rays to determine the elemental composition of rocks, minerals, cement, ceramics, metals, and petroleum. The analysis determines the types of elements in the sample based on the characteristic wavelengths of the X-rays emitted by the atoms.
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What are XRF analyses used for?
XRF is a non-destructive test method most typically used for chemical analyses of rocks, minerals, sediments, and liquids in geology, mining, and the petroleum industry.
How does X-ray fluorescence work?
In XRF analysis, the sample is irradiated with a high-energy X-ray beam. While some of the x-rays scatter from the sample (see a comparison between XRF and XRD below), some are absorbed by the atoms in the sample and the atoms start emitting fluorescent light.
Atoms of different elements emit fluorescent light in their own characteristic wavelengths. The XRF spectrometer measures a spectrum consisting of the different wavelengths emitted by the sample.
If the sample contains more than one element, a wavelength dispersive spectrometer (WDS) can be used to separate the complex X-ray spectrum into characteristic wavelengths of the individual elements. By comparing the obtained spectrum to a reference data library, the elements in the sample can be identified.
Difference between XRF and XRD
When the sample is irradiated with the x-rays, some of them are absorbed in the atoms, and some scatter. X-ray fluorescence utilizes the absorbed x-rays and the fluorescent light that the absorption creates, while x-ray diffraction analyses the diffraction patterns produced by the scattered x-rays.
XRF is often used in environmental studies of rocks and minerals or for quality control in metallurgy and fossil fuels. XRD can be used for analyzing crystalline minerals, but it is also used on polymers, pharmaceuticals, and food products. See the x-ray diffraction method page for further information.
Sample requirements and preparation
XRF analyses require relatively large sample amounts, and the sample must contain big amounts of the analyzed elements. Even though XRF can theoretically detect the emission of X-rays from any element, in practice XRF spectrometers have limited ability to accurately measure elements with an atomic number less than 11.
Both solid and liquid samples are suitable for the analysis. Solid samples have to be crushed to a fine powder before the analysis. If the powder has a wide range of different elements and grain sizes, the powdered sample needs to be further mixed with a chemical flux and melted with a furnace or a gas burner to get accurate results. Melting produces a homogenous and glass-like material from which the elements and their amounts are easier to determine.
Need an XRF analysis?
Measurlabs offers quality XRF testing services with fast results and affordable prices. If you have any questions about your sample or its suitability for the method, our experts are always happy to help. Please contact us through the form below or by emailing us at email@example.com to tell us more about your testing needs.
Suitable sample matrices
- Soil and slurry
- Crude oils
- Petroleum products
Ideal uses of XRF analyses
- Compositional analyses of earth samples in geology and environmental studies
- Soil surveys in geophysics
- Research of rocks (petrology)
- Examination of ores in mining
- Product development and quality control in metallurgy and the manufacturing of cement, ceramics and glass
- Analyses of the content of fossil fuels in petroleum industry
Frequently asked questions
XRF is commonly used for identifying both major and trace elements as well as determining their concentrations.
The most commonly used applications of XRF are the compositional analyses of geological and petrological samples such as different kinds of rocks and sediments. XRF can be used in geophysical soil surveys, mining, and environmental studies. Additionally, industries like metallurgy and the petroleum industry along with the manufacturing of cement, ceramics, and glass can utilize XRF in their product development and quality control.
Small spots of the sample cannot be analyzed with XRF and thus the sample has to be relatively large. Samples typically have to weigh more than one gram and contain relatively large amounts of elements whose absorption and fluorescence effects are reasonably well understood. In order to perform a proper identification of the elements, compositionally similar standards for the sample material have to be available.
XRF can determine concentrations from 100 wt% (weight percentage) even to sub-ppm levels. However, the limit of detection for trace elements is typically on the order of a few ppm.
Theoretically, XRF can detect the emission of X-rays from an atom of virtually any element. However, in practice, most XRF spectrometers have limited ability to accurately measure elements with an atomic number less than 11.
XRF cannot detect the differences between different isotopes of the same element. Instead, isotope analysis is possible to perform with secondary ion mass spectrometry (SIMS) or thermal ionization mass spectrometry (TIMS). XRF cannot also distinguish ions of the same element with different valence states. Information about the ion composition can be obtained for example from wet chemical analysis or Mossbauer spectroscopy.
XRF is suitable for the analysis of relatively large samples weighing more than one gram. Geological and petrological samples, such as rocks, ores, minerals, and soil are especially well-suited for the analysis, but also industrial products like ceramics and glass as well as petroleum products are suitable.
Sample materials have to contain big amounts of elements with reasonably well-understood absorption and fluorescence effects. They also have to have compositionally similar standards. When analyzing major elements, usually Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K, and P can be determined. In the case of trace elements, usually Ba, Ce, Co, Cr, Cu, Ga, La, Nb, Ni, Rb, Sc, Sr, Rh, U, V, Y, Zr, and Zn are well-detected by XRF.
Especially, when studying rocks, ores, sediments, and minerals, the material should be ground down to a fine powder and homogenized. Sometimes, especially when analyzing trace elements, the analysis can be performed directly from the powder, but commonly the powdered sample has to be homogenized by melting it down with a chemical flux.
Measurlabs offers a variety of laboratory analyses for product developers and quality managers. We perform some of the analyses in our own lab, but mostly we outsource them to carefully selected partner laboratories. This way we can send each sample to the lab that is best suited for the purpose, and offer high-quality analyses with more than a thousand different methods to our clients.
When you contact us through our contact form or by email, one of our specialists will take ownership of your case and answer your query. You get an offer with all the necessary details about the analysis, and can send your samples to the indicated address. We will then take care of sending your samples to the correct laboratories and write a clear report on the results for you.
Samples are usually delivered to our laboratory via courier. Contact us for further details before sending samples.