How XRF Works

Thank you to Thermo Fisher Niton Analyzers LLC for the following information

Whether you're looking to identify "Chinese" drywall or perform CPSIA XRF compliance testing, searching for a lead paint detector for RRP compliance, interested in precious metal testing, or just curious to learn more about an x-ray fluorescence spectrometer, we've provided you with an explanation of the physics, technology, and the algorithms that make XRF a robust, versatile, and easy-to-use elemental analysis tool.


XRF Technology Benefits


  • Sample Analysis Via Energy Dispersive X-Ray Fluorescence (EDXRF)

    Handheld Thermo Scientific Niton energy-dispersive x-ray fluorescence (EDXRF) analyzers, commonly known as XRF analyzers, are able to quickly and nondestructively determine the elemental composition of:

    ● Metal and precious metal samples
    ● Rocks and soil
    ● Slurries and liquid samples
    ● Painted surfaces, including wood, concrete, plaster, drywall and other building materials
    ● Dust collected on wipe samples
    ● Airborne heavy elements collected on filters

    Thirty or more elements may be analyzed simultaneously by measuring the characteristic fluorescence x-rays emitted by a sample. Thermo Scientific Niton XRF analyzers can quantify elements ranging from magnesium (element 12) through uranium (element 92), measuring x-ray energies from 1.25 keV up to 85 keV in the case of Pb k-shell fluorescent x-rays excited with a 109Cd isotope. These instruments also measure the elastic (Raleigh) and inelastic (Compton) scatter x-rays emitted by the sample during each measurement to determine, among other things, the approximate density and percentage of the light elements in the sample.

    XRF Excitation Model
    XRF Excitation Model

    How does EDXRF work? Each of the elements present in a sample produces a unique set of characteristic x-rays that is a "fingerprint" for that specific element. EDXRF analyzers determine the chemistry of a sample by measuring the spectrum of the characteristic x-rays emitted by the different elements in the sample when it is illuminated by x-rays. These x-rays are emitted either from a miniaturized x-ray tube, or from a small, sealed capsule of radioactive material.

    A fluorescent x-ray is created when an x-ray of sufficient energy strikes an atom in the sample, dislodging an electron from one of the atom's inner orbital shells. The atom regains stability, filling the vacancy left in the inner orbital shell with an electron from one of the atom's higher energy orbital shells. The electron drops to the lower energy state by releasing a fluorescent x-ray, and the energy of this x-ray is equal to the specific difference in energy between two quantum states of the electron.

    When a sample is measured using XRF, each element present in the sample emits its own unique fluorescent x-ray energy spectrum. By simultaneously measuring the fluorescent x-rays emitted by the different elements in the sample, handheld Thermo Scientific Niton XRF analyzers rapidly determine those elements present in the sample and their relative concentrations – in other words, the elemental chemistry of the sample. For samples with known ranges of chemical composition, such as common grades of metal alloys, these XRF guns also identify most sample types by name, typically in seconds.

    Light Element Analysis

    Metal Sample Fluorescence
    Metal Sample Fluorescence
    Recent advancements in GOLDD™ technology/a> have improved the performance of handheld XRF analyzers in general, but most especially the performance on elements below atomic #17 (Mg, Al, Si, P, S, Cl). The Niton® XL2 and the Niton XL3t with GOLDD technology can now detect elements as low as Mg (#12) without the use of Helium purging or vacuum pumps. However, a few applications require the very best in light element sensitivity. Light element XRF analysis is best performed either with a helium gas purge or in a vacuum chamber in a laboratory environment. As the use of a vacuum with portable XRF is highly impractical (even minor punctures to the thin window used to seal the instrument from the environment will draw dust, debris and metal filings into the instrument), then a He purge unit is the most appropriate solution for the very best performance on light element analysis (Mg, Al, Si, P, S, Cl).