Measurement Principles
    OnlineOn-streamAt-line

    X-ray fluorescence (XRF)

    X-ray fluorescence determines elemental content by exciting the sample with X-rays and measuring the element-specific fluorescence radiation emitted in the process — without digestion and without reagents.

    Installation types

    OnlineThe sample is routed through a bypass or measuring cell and measured cyclically, for example in electroplating baths or fuel streams.
    On-streamSeveral process streams are measured sequentially at one analyzer, typical for slurries in minerals processing.
    At-lineSamples taken from the process are measured right next to the plant, without going to a central laboratory.

    In process analytics, X-ray fluorescence is rarely a true inline measurement with a probe in the product stream; measuring cells, bypasses or sampling are the norm.

    Relevant industries

    Surface finishing & electroplating

    Metal concentrations in electrolytes and baths, such as zinc, nickel, gold, palladium and chromium.

    Chemicals & petrochemicals

    Sulfur and chlorine content in fuels, crude oil and pyrolysis oils.

    Mining & minerals processing

    Elemental content in slurries along ore feed, concentrate, flotation circuit and tailings.

    Standards & regulation

    • DIN EN ISO 20884 — Determination of sulfur content in petroleum products, wavelength-dispersive X-ray fluorescence spectrometry
    • EN ISO 3497 — Measurement of coating thickness of metallic coatings, X-ray spectrometric methods

    FAQ

    What is the difference between EDXRF and WDXRF?

    In the energy-dispersive method the detector separates the radiation by energy — the instrument is more compact and faster, but offers lower resolution. In the wavelength-dispersive method a crystal separates the radiation by wavelength, which allows higher resolution and lower detection limits but is more complex. Some process instruments combine both channels.

    Which elements can be measured?

    Depending on instrument and excitation, roughly from sodium to uranium. Light elements are difficult because their fluorescence radiation is low in energy and absorbed in air — vacuum, helium or dedicated optics are required.

    Is X-ray fluorescence an inline method?

    In process analytics, online and at-line installations with a measuring cell or bypass predominate. A probe directly in the product stream is uncommon.

    What limits accuracy in the process?

    Mainly matrix effects, the window material and its fouling, and, for slurries, solids content and particle size. Calibration is therefore carried out against the real matrix, and the measuring window needs defined maintenance or an automatic changer.

    Dusko Kadijevic | Publisher Analytic Journal | analyticjournal.com

    Written October 2026. All content formulated in our own words, created with AI assistance.