WROXI Certified Reference Materials

Hello, my name is Mark Ingham and I’m an expert on XRF. In my first blog, I’ll describe the history of WROXI reference materials and the benefits stemming from the new ISO 17034 accreditation.

Let’s take a look at why the WROXI reference materials for XRF have proved so popular over the last 15 years, and the benefits stemming from the new ISO 17034 certification.

The beginnings of WROXI

Do you ever find that inspiration only strikes when you’re faced with the same problem, day-in, day-out? It was certainly true for me when I came up with the idea for WROXI – our ready-to-use kits for making XRF calibration standards.

At the time – the early 1990s – I was working in the Analytical Geochemistry Group at the British Geological Survey (BGS) in Keyworth, near Nottingham, UK. We mostly used single-oxide standards for calibration, which was very time-consuming, and also difficult because the powders did not always fuse very easily.

As XRF is fundamentally  a comparative technique, it relies heavily on the accuracy of the sampling, preparation, calibration and measurement processes

A wide range of oxides

As a result of these difficulties, I began to think – why not mix the oxides of the commonest rock-forming elements together into a single set of standards? That would reduce the number of calibration samples needed, and also make it easier to fuse the powders to get clear, high-quality beads.

So that’s exactly what I did, and the ‘WROXI’ product (short for Wide-Range OXIdes) was born.

These WROXI standards were designed for our clients PANalytical. As time went by, the focus of BGS shifted away from analytical work, and in 2011 BGS decided to sell the facility to PANalytical, which I joined as a staff member.

For a while, BGS leased the laboratories to PANalytical, but when that arrangement came to an end, I moved (literally) just a mile or so down the road, from Keyworth to Tollerton. There, I helped set up a laboratory in The Coach House, which remains the ‘headquarters’ of our WROXI and other standards products today.

Our laboratories in The Coach House in Tollerton are where we make all our WROXI standards… and they’re the first in the world to produce synthetic CRMs for XRF certified to ISO 17034.

Why is WROXI so popular?

Through all these business changes, our WROXI standards have remained pretty much the same. (The only significant change was the introduction of a ‘Base’ set with ‘Cement’ and ‘Pro’ extensions in 2020, so customers in certain industries don’t have to measure more elements than necessary.)

So what’s the reason for WROXI’s enduring appeal? I think it comes down to four key points:

  • Using WROXI standards is quick and cost-effective. Just imagine having to set up an application for (let’s say) the 11 common oxides. Buying the reference materials, working out the fusion parameters, building the application, calibration, and would take months of effort. But with WROXI most of this work is already done, meaning your Epsilon 4 or Zetium spectrometer can be ready to run your samples within a week.
  • WROXI standards are totally synthetic. Unlike conventional reference materials made from stocks of geological samples, soils, fly ash or cement clinker, WROXI standards are made from high-purity, commercially available chemicals, so they’ll never run out.
  • Because WROXI standards are synthetic, we can avoid measurement uncertainties caused by peak overlap between different elements (such as titanium and vanadium), by not including them in the same standard. And of course, mineralogical effects and particle-size effects are eliminated during the fusion process, giving an order-of-magnitude increase in accuracy over pressed powder pellets.
  • The two extension sets make WROXI standards flexible – and we are always happy to develop custom standards containing uncommon elements or different concentration ranges. I recall an industrial recycling company a few years ago who needed to measure tungsten in their samples… as well as 20 other elements! At the time, there were only three reference materials available, none of which supported quantitation of tungsten, so we created a set of custom standards for them containing the entire suite of elements. This then allowed them to use the existing reference materials for validation.
The ‘Base’ WROXI kit contains pre-mixed powders containing the oxides of the 11 common rock-forming elements, ready for fusion into beads using your own equipment. The ‘Cement’ and ‘Pro’ extension kits offer additional elements that are useful in certain industries.

Certification of XRF reference materials: A ‘world first’

There’s also another advantage resulting from the synthetic nature of WROXI standards – we’re able to make them gravimetrically. This opens up the possibility of certifying them to the international standard for reference materials (ISO 17034), which is what we’ve now done with the launch of our WROXI Certified Reference Materials (CRMs).

It’s not been a quick job though – it’s taken two years to go through the ISO 17034 certification process. This is partly because we were the first laboratory in the world to request this for synthetic XRF Certified Reference Materials.

What does this mean for our customers? Essentially an additional confidence boost in the WROXI product. Our laboratories at Tollerton were already accredited by UKAS to ISO/IEC 17025 (the general laboratory standard for testing), but we’ve now had to go much further, by demonstrating that all the processes we use to make our WROXI CRMs meet strict requirements, that all our measurements are traceable, and that every single bottle of the finished product has a certificate and documentation trail associated with it.

The powders now come with the major endorsement of ISO 17034 certification. After 40 years in the XRF business, achieving this is a great milestone for me personally… and of course it further strengthens the ‘analytical chain’ of XRF instrumentation, supplies and expertise from Malvern Panalytical!