ED-XRF Screening

Radiation Physics

The operation of the instrument involves directing a beam of X-rays at the surface of the specimen, which knocks electrons out of the inner shells of the atoms. As electrons from higher energy outer shells drop down to fill these gaps, they release energy in the form of secondary X-ray fluorescence. Every element in the periodic table emits a unique energy spectrum that the detector captures and converts into a digital signal.

The intensity of the peaks in this spectrum corresponds to the concentration of the element on the surface of the material. This process occurs in seconds and does not require any chemical preparation of the sample. Technicians can use portable handheld devices to scan materials directly on the warehouse floor or in the factory.

The depth of the analysis is limited to the top few millimetres of the material, which makes it ideal for testing coatings and surface prints. Because the sample is not destroyed, it can be returned to the production line or sent for further confirmatory testing if a failure is detected.

Screening Value

Companies use this technology as a first line of defense to prevent hazardous materials from entering the supply chain. ED-XRF screening allows for the rapid testing of a high volume of items, which is much faster than traditional wet chemistry methods. It provides an immediate pass or fail result based on the regulatory limits programmed into the software.

This speed is particularly useful when checking large shipments of metal trim where individual items might vary in their alloy composition. If a scan shows an elevated level of a restricted element, the item is flagged for a more precise analysis using inductively coupled plasma. This two step approach balances the need for speed with the requirement for absolute accuracy.

The data collected from these scans also help to build a profile of supplier reliability over time. By maintaining a record of these tests, a mill can demonstrate its commitment to chemical safety and regulatory compliance.

Analytical Depth

The accuracy of the result is influenced by the thickness of the sample and the smoothness of the surface being scanned. ED-XRF screening can produce false negatives if the restricted element is buried deep within a thick textile or if the sample is not large enough to cover the detector window. It is also less sensitive to light elements like boron or carbon, which limits its use for organic chemical screening.

The instrument must be calibrated regularly using certified reference materials to ensure that the readings remain consistent. Results are reported as a concentration in parts per million, but these figures are considered semi-quantitative estimates rather than absolute values. The method is a tool for identification and screening rather than a final legal determination of total content.

Proper training for the operator is required to interpret the spectra and avoid errors caused by overlapping elemental peaks.