X-Ray Fluorescence (XRF)
Definition
A technique in which a sample is irradiated with a primary X-ray beam, causing its constituent elements to emit characteristic secondary (fluorescent) X-rays that are measured to determine elemental composition.
- Signal measured
- Characteristic secondary X-rays emitted by excited atoms
- Sample handling
- Non-destructive, usually no preparation needed
- Detects
- Elemental composition, not molecular structure
- Common variants
- Energy-dispersive (EDXRF) and wavelength-dispersive (WDXRF)
- Typical use
- Screening glass, paint, soil and metal for elemental profile
Common questions
What can XRF not tell an examiner?+
XRF identifies which elements are present and roughly how much of each, but it gives no information about how those elements are chemically bonded, so it cannot distinguish two compounds built from the same elements arranged differently.
How does XRF differ from XRD in trace evidence work?+
XRF measures elemental composition from emitted X-rays, while XRD measures the crystal lattice spacing of mineral phases from diffracted X-rays; the two are often run together because elemental data alone cannot confirm which mineral an element belongs to.
Is XRF sensitive enough to detect trace contaminants?+
Bench and portable XRF units typically detect elements down to tens or hundreds of parts per million, adequate for bulk comparison work such as glass or soil sourcing but well above the sub-part-per-billion sensitivity ICP-MS offers.
Related terms
- Energy-Dispersive XRF (ED-XRF)
- An XRF configuration using a solid-state detector that registers all emitted photon energies simultaneously. Faster and more compact than WD-XRF, enabling portable...
- Fused Bead
- A preparation method where soil is dissolved in molten lithium tetraborate or metaborate flux at around 1100 degrees Celsius to form a...
- Matrix Effect
- The absorption or enhancement of characteristic X-rays by other elements in the same sample, causing apparent concentrations to deviate from true values...
- Pressed Pellet
- A sample preparation form in which finely ground, dried soil is mixed with a binder and compressed under several tonnes of pressure...
- Wavelength-Dispersive XRF (WD-XRF)
- An XRF configuration that uses an analysing crystal to separate emitted X-rays by wavelength before detection, giving high spectral resolution and low...