The Surprising Advancements of ED-XRF Technology Compared to WD-XRF

Ask industry experts to compare the technological advancements of ED-XRF spectrometers against the more expensive WD-XRF devices, and their findings may surprise many. Traditionally, WD-XRF was long presumed to outperform ED-XRF in various aspects. But today, that assumption is no longer valid. The latest ED-XRF analyzers offer significant advantages in sensitivity, precision, cycle time, throughput, ease of use, compactness, and cost-effectiveness.

Most modern WD-XRF instruments employ sequential technology. While a few high-end models feature a tuned crystal/detector set for each element and can analyze multiple elements simultaneously, they are still limited to the preselected elements for which they have channels. Sequential units can analyze elements ranging from beryllium to uranium, albeit one at a time. WD-XRF spectrometers are complex and expensive devices that necessitate extensive cooling when operating at power of 3-4 kW. They rely on a supply of compressed gas for one of the detectors and sometimes require compressed air for sample movement. Moreover, the hardware is intricate, comprising numerous moving parts.

On the other hand, top-tier ED-XRF analyzers provide a multi-elemental analysis of major, minor, and trace element concentrations with exceptional resolution, even in samples of unknown composition—be it liquid, powder, or solid. They do not require external chilling equipment. Only low-volume helium purging for the analysis of light elements in liquids and powders and a vacuum system for solid samples are used. The most advanced ED-XRF spectrometer costs half the price of a top-tier WD-XRF and is significantly less expensive in ongoing operation and maintenance.

A Shift in the Balance

Despite their high cost and greater complexity, WD-XRF analyzers previously held an edge over ED-XRF units in various performance aspects. However, the balance has now decisively tipped in favor of today's leading ED-XRF models over sequential WD-XRF instruments.

According to Mario Van Driessche, owner of X-Ray Services BV and a consultant on spectroscopic analysis, "For most applications, top-of-the-line ED-XRF technology has absolutely reached parity with WD-XRF. The limits of detection are better, and the repeatability is at least the same."

Furthermore, WD-XRF technology has hit a dead end. Dr. Joachim Heckel, a senior consultant and former director of research and development for SPECTRO, notes that "a WD-XRF maker cannot increase the power of their tube and reduce the optical path because they already produce a lot of heat at the sample. Any more, and they burn or cook their sample. And there's not much improvement to be made in their detectors or electronics."

Enhanced Sensitivity, Precision, and LODs

The latest SPECTRO XEPOS ED-XRF analyzer offers significantly improved sensitivity compared to earlier ED models, often surpassing them by over tenfold and up to three times better precision. It can achieve remarkably low detection limits (usually less than 1 ppm) for critical trace amounts, including heavy elements like cadmium (Cd). Additionally, the analyzer's long-term stability now rivals that of WD-XRF models.

Increased Sample Throughput, Reduced Measurement Time

The speed of ED-XRF analyzers has witnessed substantial improvement over time. "In the beginning," says Dr. Heckel, "we might require 1 hour measurement time per sample. For many applications, we are now at round about 3 minutes."

Alexander Seyfarth, Global XRF Technology Manager for SGS North America Natural Resources Geochemistry Group, explains, "WD-XRF is faster for a single element. But the moment I have a complex multielement sample and many elements to report to the client — the more elements I run, the better it's going to be for a good ED-XRF in comparison. It's throughput and cost of ownership that count."

Ease of Use and Software

An advanced ED-XRF model is also user-friendly, providing efficient procedures for achieving accurate results in minimal time, enabling high productivity. TurboQuant II, SPECTRO's universal screening tool, for instance, simplifies the screening process, allowing users to obtain meaningful data "more along the lines of 'press button get results' than the traditional standardless programs used on WD instruments," Seyfarth notes.

Compactness and Simplicity

Lab space is often limited. "A small footprint is important," says Van Driessche. "An ED-XRF like SPECTRO XEPOS is relatively compact. And it has related advantages. You need no extra water-cooling unit, and only if your instrument is equipped with a vacuum will you have to make space under the bench for the pump. And you have a limited gas consumption. Plus, you need only one gas — with WD-XRF, you need two gases."

The Bottom Line

Even top-of-the-line ED-XRF models offer significantly lower initial investment and ownership costs while delivering superior performance — often at half the price due to fewer moving parts, the absence of a chiller and compressed gases, lower component replacement costs, and simplified installation processes.

Experts anticipate further advancements in ED-XRF throughput and measurement speed offer promising avenues for improvement before the technology reaches its physical limits. But today, ED-XRF is a leading solution for a wide range of analysis requirements, surpassing WD-XRF in sensitivity, precision, throughput, ease of use, compactness, and affordability.

Download the 16-page white paper "Surprising New Capabilities of ED-XRF Technology" for a deeper comparison of ED-XRF and WD-XRF technologies.