X-ray Fluorescence: Energy Dispersive v. Wavelength Dispersive

As organizations research analytical equipment to solve particular material analysis needs, they will contact Eastern Applied Research regarding x-ray fluorescence technology. From time to time, contacts will ask about two difference styles of x-ray technologies - Wavelength Dispersive (WD-XRF) and Energy Dispersive (ED-XRF).

As specialists in ED-XRF analyzers, Eastern Applied has seen improvements in the technology that have resulted in expanded application fields and make it a consideration for applications that used to be solved by WD-XRF. This article provides a brief comparison of the two technologies. Contact Eastern Applied to discuss further and see if ED-XRF is a fit for your applications.

Both technologies are based around the principle of using an x-ray source to excite a sample, a detection system to collect fluoresced x-rays, and a software program to process the measurement data. The difference in a wavelength system is that a crystal between the tubes diffracts x-rays of a specific wavelength into the detector tube. This added step (and components) results in varying performance capabilities and costs between the technologies. 

Two main differences that affect performance: 

Energy Resolution - depending on the instrument specifics, WD-XRF analyzers will provide resolutions of 5eV to 20eV while ED-XRF systems typically offer a range of 120eV to 220eV. The lower resolutions of WD-XRF will reduce spectral overlaps and provide more efficient characterization of complex samples. While this difference may benefit wavelength technology for a specific element of interest or application, the optical components required to achieve those resolutions result in a more expensive system - both in the initial cost of acquisition and over the course of its lifespan. Advancements in ED-XRF detection systems have improved those resolutions greatly and we have seen an increased range of applications solved by ED-XRF due, in part, to those advancements. 

Spectral Acquisition - this is a factor that limits wavelength dispersive technology as a spectrum is either made in a point-by-point fashion (very time consuming) or has additional detectors (very costly approach). Energy dispersive, on the other hand, will acquire an entire spectrum almost simultaneously. While a user may see a slight reduction in accuracy for one element, the range of elements seen are achieved in a faster, more efficient, approach and result in a broader range of material analysis capabilities.

At Eastern Applied Research, we specialize in the energy dispersive x-ray fluorescence technology. We have been part of ED-XRF's evolution over the last twenty years and appreciate the benefits it offers over wavelength, benefits of ED-XRF include: 

• lower cost of acquisition
• broader, more diverse, analytical scope
• lower cost of maintenance
• greater reliability due to less complicated design
• less electrical power consumption

In addition to those benefits, energy dispersive x-ray fluorescence has seen great improvements over recent years, including the addition of poly-capillary optics (seen in the micro-XRF Hitachi FT-150) and extremely versatile systems like the Hitachi EA6000VX.

If you are considering x-ray fluorescence and would like to learn more about ED-XRF options or the difference between technologies, we encourage you to request a conversation from an Eastern Applied Research XRF specialist.