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Improved profitability, greater efficiency, optimum quality – it all starts with reliable data.

Low grade deposits and the increasing cost of processing are dampening profitability across minerals industries. But could you be making more of your mineral deposits? Representative sampling and accurate analysis provides the data you need to optimise all aspects of your exploration and mining processes. What you get:Greater control over the life of your mine

  • Greater control over the life of your mine
  • A sound basis for making process decisions
  • A better-quality product – and the proof to back it up
  • Improved profitability and process efficiency

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The 5 most common ways to prepare samples for XRF analysis

Sample Preparation for XRF Analysis

XRF (X-ray Fluorescence Spectrometry) is a comparative chemical analysis technique that is capable of analyzing a wide range of materials in different forms for a large part of the periodic table. This versatility makes it applicable to a wide range of applications from quality control for metal alloys, to the analysis of sulfur in gasoline to heavy metals in plastics and electronics. XRF can analyze almost any material you can present to the spectrometer, but the better you prepare a sample the more accurate your analytical results. Your choice of sample preparation will always be a balance of the quality of results your require, the effort your are willing to expend (labor, complexity) and the cost (sample preparation equipment, labor, time to analysis). Your choice may be different for different materials depending on your analysis requirements.

How do you choose what sample preparation method is best for your application?

Here we review the 5 most common ways to prepare samples for XRF analysis and what you need to consider with each method.


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Solid Samples

Solid samples can be anything from unprepared pieces of metal or electronics or plastics to cut and polished metal samples. The ideal sample for XRF analysis will have a perfectly flat surface. Irregular sample surfaces change the distance from the sample to the x-ray source and introduce error. All XRF systems are calibrated based on a fixed sample to source distance. Changing the distance can increase or decrease the intensity coming from any element contained in the sample.

Solid samples such as metal alloys, can be analyzed with no sample preparation or they can be cut and polished for a more quantitative analysis.

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Even for largely flat samples, surface finish can affect your analysis, particularly for lighter elements. Rough surfaces can cause scattering and re-absorption of longer wavelength elements. This effect is energy dependent so while the Ni signal may not be affected, the signal from C or S could be dramatically reduced. Quantitative analysis of solid samples often requires finishing the surface with a lathe or grinding paper. The finer the finish the better the results will be for the lightest elements.

testing. It is also important to note that the sample preparation you choose should be applied to your calibration standards as well as any unknown samples.

Loose Powders

The analysis of loose powdered material usually requires that the sample be placed into a plastic sample cup with a plastic support film.  This insures a flat surface to the X-ray analyzer and the sample to be supported over the X-ray beam. The more finely ground the sample the more likely it is to be homogeneous and have limited void spaces providing for a better analysis.  Sufficient powder should be used to insure infinite thickness is obtained for all of the elements of interest. This requirement can be met by using 15g of sample for most materials. Special care should be taken for the analysis of metal powders in high power (2-4Kw) WDXRF instruments. The sample can heat up during analysis and melt through the support film resulting in abrasive powder being spilled directly into your instrument.

Pressed Pellets

Pressing powder into pellets is a more rigorous sample preparation than pouring loose powders into a sample cup.  The process includes grinding a sample into a fine powder, ideally to a grain size of <75um, mixing  it with a binding /grinding aid and then pressing the mixture in a die at between 20 and 30T to produce a homogeneous sample pellet. The binding /grinding aid is usually a cellulose wax mixture and combines with the sample in a proportion of 20%-30% binder to sample.

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This sample preparation approach provides better analytical results than loose powders because the grinding and compression creates a more homogeneous representation of the sample with no void spaces and little sample dilution. This leads to higher intensities for most elements than loose powders.  Pressed pellets are still susceptible to particle size effects if not ground fine enough, but the biggest limitation to this approach is the mineralogical effects which most predominantly affect the analysis of major elements. Pressed pellets are excellent for the analysis of elements in the ppm range. Pressed pellets are also relatively simple and inexpensive to prepare only requiring a pulverizing mill and sample press.

Fused Beads

Sample prepared as fused beads provide a near perfectly homogeneous representation of the sample to the XRF and is considered by many to be the ideal sample preparation method for solids.  Fused beads are created by mixing a finely powdered (<75um) sample with a flux in a flux/sample ratio of 5:1 to 10:1 and then heated to 900C-1000C in a platinum crucible. The sample is dissolved in the flux(usually a lithium tetraborate or tetraborate/metaborate mixture )and cast into a mold  with a flat bottom. The resultant glass disc or fused bead is a

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homogeneous representation of the sample free of mineral structures. The benefits of this approach are the reduction of mineralogical or matrix effects leading to more accurate analyses and the ability to combine several different matrix types into the same calibration curve.  Downsides include the relatively high sample dilution which has a negative effect on the analysis of trace elements and the higher cost associated with this type of sample preparation (fusion equipment, platinum crucibles and consumables) Typical fused beads are also only approximately 3mm thick and thus are susceptible to infinite thickness issues for heavier elements. Fused beads usually require higher initial costs between platinumware and a fusion device, but then have similar cost/sample to prepare as pressed pellets.


Liquids are prepared by pouring them into a plastic sample cup in the same way as loose powdered samples. There are limited options for analyzing liquid samples and the main trick is to choose the correct support film that provides a balance of strength and transmission capabilities and contamination.  Mylar is a good general purpose film often used for the analysis of sulfur in fuels or lubricating oils. Polypropylene has better transmission than Mylar but has a lower tensile strength.  Kapton is the “bomb proof” film but dramatically attenuates your signal for lighter elements and is susceptible to strongly basic solutions.  If you are going to analyze liquids you will need to do a little research into selecting the best support film for your analysis goals. If you are using your XRF to analyze sulfur in fuels.


There are many ways to prepare samples for XRF analysis and the method you choose will be a balance of the sample type, the amount of effort you are willing to expend and the quality of results you require.


Written by: David Coler Posted by LGC ARMI | MBH  (

Know “Why” & “How” ICP-OES Wavelength Calibration is needed and done

ICP-OES is one of the the analyzing technique across a number of industries, and when configured correctly, today’s instruments yield detection limits of 1 to 10 ppb for the majority of elements. Although a powerful elemental analysis technique, it is in fact a simple comparator, incapable of making absolute measurements.

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Fundamentally, qualitative identification of each element is determined by the presence or absence of emission lines and quantification is determined using the emission intensity. Unfortunately, optical spectra are very complex and variations in optical configurations mean that every ICP-OES instrument has a unique correlation between emission wavelengths and where they are positioned on the instrument’s detection system. Accurate indexing of each wavelength is critical for obtaining accurate data.

Wavelength calibration is the process used to “teach” the instrument exactly which position of its detection system corresponds to each emission wavelength. Wavelength calibration in ICP-OES is typically achieved by aspirating a multi-element solution which will produce elemental emission for each element contained in the solution.  This multi-element solution should be run regularly to adjust for daily variations which inevitably can occur in the optical chamber of the ICP. The specific elements contained in the solutions are chosen to produce relatively simple spectra while also covering the relevant wavelength range of the instrument. All modern ICP-OES instruments incorporate an automated wavelength calibration routine. The instrument operator simply loads the wavelength calibration solution designed for use with their model instrument and the software does the rest.

Wavelength calibration impacts virtually every aspect of your ICP’s performance, including its sensitivity (detection limits), stability (RSDs), and susceptibility to interferences. Accuracy of the preparation of the wavelength calibration solution is directly tied to the integrity of all of the analysis performed on the calibrated instrument.


As we explored in a previous blog, Three Common Pitfalls to Avoid When Preparing Aqueous Multi-element Standards for AA, ICP, or ICP-MS, there are many opportunities to introduce inaccuracies while preparing multi-element standards. To mitigate that risk, regulations increasingly require that instrument calibrations carry international validity, particularly in industries producing legally defensible data. As a result, labs must use commercially available CRMs prepared by appropriately accredited manufacturers for all wavelength calibration. If you need help tuning your spectrometer, or selecting the appropriate wavelength calibration solution, one of our industry experts can help.

Ask an Expert 

Or if you want to know more about our Aqueous CRMs,

Visit our Aqueous Page

Written by: Courtney Dillon Posten on : ARMI MBH (

Metal Processing Optical Emission Spectrometry (OES)

In Metal Industry, checks during all the production processes are extremely necessary, starting from raw material control and primary material fusion, up to quality verification before shipping the final product.

During all manufacturing phases, forming, molding, die-casting, extrusion, mechanical manufacturing, it is necessary evaluate different chemical-physical parameters in order to give the essential information for production cycle.

Our partner GNR offers advanced solutions to perform different and wide analytical tasks in the metal industry. 

For Metal Processing Optical Emission Spectrometry (OES) using Arc/Spark excitation is the traditional reference technique for fast and accurate  elemental analysis of solid metallic samples.

It is a well proven technology nowadays used in all the metal  industry  sector from production control to R&D, from incoming material inspection to scrap sorting.

GNR offers PMT-based or CMOS-based spectrometers, Bench Top, Floor Stand and Portable systems to provide high uptime and stable performance for enhanced productivity.

To know more about the GNR OES please CLICK HERE


Posted by GNR – Analytical Instrument Groups (