SPECTRO XEPOS

Q&A: The Rise of ED-XRF

What consumables are usually required when using ED-XRF?

Consumables depend on the application and the sample preparation. For the analysis of liquids and powders, sample cups and sample support film are required. If samples are analyzed as pressed pellets these are typically prepared with a binder. For the sample preparation as fused beads a flux is required. In addition helium is required if light elements are of interest and a measurement under vacuum is not possible. The helium consumption is very low, typically not more the 4.5 liters per sample analysis.

Is it possible to calibrate this instrument for a standard user?

Yes, with proper training, the calibration is possible by the user. The training can be provided during the installation of the analyzer or at one of our training classes that we offer at various locations around the world.

What would be a typical measurement time for the relevant elements in a typical lube oil sample?

A typical lube oil sample can be analyzed within 10 minutes or less.

Is there a quantitative benefit for lighter elements Na, Mg?

The benefit of using the HAPG (Highly Annealed Pyrolithic Graphite) polarizer for the determination of those elements depends a bit on the sample matrix. Compared to a direct excitation 3 to 10 times higher sensitivity can be obtained.

What is the material of the band-pass filter and how does it work?

The bandpass filter consists of Highly Annealed Pyrolithic Graphite (HAPG). For this use as a bandpass filter the angle of the beam to the crystal is set such that only Co K-alpha radiation fulfills Bragg’s law and can be reflected.

Can you comment on the sample matrix effect? Petroleum crude oils contain both inorganic and organic chloride compound. Can this XRF analyzer be used for total Cl measurements?

The analyzer indeed can determine the total Cl in such samples. For more information about the matrix effects please see our TurboQuant video.

For our application we are concerned with NI, FE, CO and TI alloys in the recycling industry.

For this kind of application the instrument is calibrated with a so-called Fundamental Parameters (FP) method. This will automatically correct for matrix effects and can handle a large range of alloy matrices.

How is the instrument calibrated and how often is recalibration needed?

A correction is done for peak drifts (weekly-monthly), a standardization for changing sensitivity might be required on a yearly basis. Running QC samples to validate the performance of the analyzer frequently is highly recommended.

Could you expand upon the capability of detecting flame retardants (P and/or Cl) in foamed polymers?

This should be verified with real samples. As the fluorescence for P and Cl is only detected from a thin layer of the sample, the sample surface and the density of the foam are very much influencing the results. If the surface and density of the foam are always consistent, a calibration and analysis is possible. If that cannot be guaranteed for all samples, we also should look into possible sample preparation.

With trace elements such as As, Ag, Au, B, Bi, Cd, Pb, Sb, Se, Sn, Te, Tl, Y at the ppm lower level, can the new technology analyze any of these samples if prepared in a pellet? What is material used to form the pellet?

The analysis of those trace elements is possible with the exception of B. Samples can be analyzed as powders. If samples will be analyzed as pressed pellets we generally use 5 grams of the sample with 1 gram of wax binder. The mixture is then blended and pressed into a stee ring with outer diameter 40 mm nd inner diameter of 32 mm. Alternatively a pellet with a 32 mm outer diameter is produced. Typically a 15 to 25 ton press, with a suitable sample die, is used.

Can we analyze arsenic 3 and arsenic 5 in soil samples?

We cannot do the separate analysis of species like arsenic 3 and arsenic 5. With XRF you would analyze the total As concentration.

How significant are matrix effects, i.e. do you have to calibrate using matrix matched standards?

Matrix effects can be significant. A matrix matching calibration is required for the highest accuracy. Analysis methods like the TurboQuant from SPECTRO automatically correct for matrix effects and will achieve high levels of accuracy for a wide range of elements in broad concentration ranges. For more information about the matrix effects please see our TurboQuant video.

If the weight and volume ratio of different elements in a sample is too high, then how good is this method to measure them?

For special calibrations with matrix matching standards, the sample weight and thickness should be kept as constant as possible. For general analysis methods like TurboQuant the user must enter the sample diameter, weight and thickness or density in order to get the best possible accuracy.

Have you looked at chlorine analysis in oil matrix samples – specifically as an indicator of total PCB concentration?

Yes, Cl is one of the standard elements in oil analysis as well as in the TurboQuant screening method. It can be used as an indicator for PCB but the results will always show the total Cl concentration.

Is ED-XRF technology suitable for estimation of high purity products, e.g., Mg% in MgO pure sample and to what extent?

For high purity analysis, typically the relevant trace elements are analyzed. Therefore, the accuracy of analyzing the content of MgO in a high purity sample would depend on the accuracy of the analysis of the trace elements.

Can you repeat what the detection limit for Magnesium is?

The detection limit for Mg depends on the sample matrix. For a pure oil sample, a detection limit of 7 ppm is possible using a standard measurement time.

What is the mechanism by which polarization improves excitation?

The angle of the beam to the crystal is set such that only the Pd L-alpha radiation fulfills Bragg’s law and can be reflected. With the reflection we create a monochromatic and polarized radiation. As the sample and detector are placed in a Cartesian geometry, the excitation radiation can barely be scattered by the sample. With this the background is reduced. In addition, as can be seen from the schematics, a larger portion of the tube radiation is collected by the curved crystal polarizer and reflected to the sample and the intensity on the sample is enhanced. So we decrease the background and enhance the sensitivity.

Can I use this method to determine complete elemental analysis and what is the degree of accuracy compared to ICP-MS or ICP-OES?

The analysis of elements in the range Na-U is possible. The accuracy depends on the calibration but also on the concentration levels. ICP-OES and ICP-MS are certainly preferred when analyzing elements at very low concentrations but the dilution, by using a sample digestion, has to be considered as well when comparing analyses at low concentration levels. The strength of XRF is the accurate analysis of trace, minor and major elements without having the need for extensive sample preparation and without the running costs of an ICP.

How do we compare the performance of this ED-XRF with WD-XRF for cement applications?

An application brief for this application will be available soon.

Did you consider development of applications for use in pharmaceutical industry?

For this application, please take a look at our white paper about the analysis of pharmaceutical samples.

I am looking at low levels Zn in Pb concentrates and Pb in Zn concentrates. What are the benefits of the new technology?

For the analysis of the higher concentration elements the precision of the results is now better compared to before (at the same measurement time). Also the LODs for the trace elements have been improved, I expect a factor of ~ 3 improvement.

So what is the LOD comparison of ED with WD XRF, currently?

The LODs always depend on the sample matrix. For some elements ED-XRF and WD-XRF can achieve comparable LODs. For some WD-XRF and for others ED-XRF will allow for lower LODs.

Can a figure be provided for LOD improvement for Particulate Matter (PM2.5, PM10 Sample Analyses)?

Please take a look at the application brief for this application. Comparing the sensitivity of the new instrument generation to the predecessor, a factor of 3 for many elements is easily possible and for some elements the factor goes up to ~ 30.

Please address analysis of platinum group metals in solution dissolved from ores.

Platinum group metals in solution dissolved from ores can be analyzed directly in prepared sample cups. The LOD in liquid depends on the other elements present and can be lower than 1 ppm in a pure solution.

The 60 kV excitation is driven through the inner channel using appropriate filters for Z=40-52 elements?

Yes, this is correct. The radiation used for the high-energy excitation passes through the direct excitation channel. We are using a sandwich filter of two metals to reduce the background and remove, for example, the Pd-line from the excitation.

Can you compare ED-XRF to ICP-OES and ICP-MS?

When comparing the three techniques the major aspects to be considered are the elements of interest, the required detection limits, the required accuracy, the necessary sample preparation, the sample throughput, investment, and operating costs. There is no general answer to that question.

Are there risks when you measure solutions?

When analyzing solutions the right sample support film should be selected. Additionally, each sample cup should be checked for leakage before the analysis. In the new XEPOS there is a sample spillage collection area to collect sample spillage if a sample cup breaks after the analysis is done.

For what applications do we need helium?

Helium as a purge gas is required when analyzing “light” elements in liquid or powder samples. The helium consumption is very low, typically not more the 4.5 liters per sample analysis.

Is there any difference in limits of detection between pressed pellets and fusion.

Due to the dilution resulting from the sample preparation, LODs in fused beads are worse compared to those achievable when analyzing a powder or pressed pellet.

Why is helium used instead of another gas?

Helium is used as this will show minimal absorption of low energy fluorescence radiation. Other gases like N2 or Ar show a much higher absorption.

On-Demand Webinar

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Look closely at what is possible today for some typical applications.

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Download the new SPECTRO XEPOS brochure to learn more.

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