LIBS and XRF Blog and references
...
Our thoughts and findings - all things LIBS and XRF
A damaged XRF is fairly useless in the field... or the lab. And you can't replace it quickly.
19 August 2025
How do you best look after your sensitive LIBS or XRF spectrometer?
I asked this question as I prepared to rent our XRF for a few months to a small exploration crew doing a remote soil and drilling programme. I have heard horror stories of exploration teams needing two XRFs because they always had one unit being sent back to the manufacturer for repairs… Bloody Hillbillies.
My perspective is biased… that of a few of us that paid for our spectrometers out of our own pockets. It’s like driving a Company car versus using your own Personal car.
In my favour was that I had a few days to work with the users. Time to impart how how carefully these precision instruments need to be looked after... without being an overbearing goat.
We did radiation safety, XRF familiarisation, took soils, shot core, saving data, data management, incorporated blanks and standards, used a workstation, replaced XRF films, learned about dreaded dust, used a radiation meter, etc. I pelletised some of their soil samples to make matrix matched reference materials for their soil standards.
What I thought was interesting was switching on a radiation meter on my four hour flight to Darwin. Cosmic radiation hovered around 0.75-1.0 micro Sieverts/hr, higher radiation exposure than properly using an XRF for a week let alone a day. This may explain why some pilots are the way they are...
My thoughts on keeping an XRF pristine:
How do you best look after your sensitive LIBS or XRF spectrometer?
I asked this question as I prepared to rent our XRF for a few months to a small exploration crew doing a remote soil and drilling programme. I have heard horror stories of exploration teams needing two XRFs because they always had one unit being sent back to the manufacturer for repairs… Bloody Hillbillies.
My perspective is biased… that of a few of us that paid for our spectrometers out of our own pockets. It’s like driving a Company car versus using your own Personal car.
In my favour was that I had a few days to work with the users. Time to impart how how carefully these precision instruments need to be looked after... without being an overbearing goat.
We did radiation safety, XRF familiarisation, took soils, shot core, saving data, data management, incorporated blanks and standards, used a workstation, replaced XRF films, learned about dreaded dust, used a radiation meter, etc. I pelletised some of their soil samples to make matrix matched reference materials for their soil standards.
What I thought was interesting was switching on a radiation meter on my four hour flight to Darwin. Cosmic radiation hovered around 0.75-1.0 micro Sieverts/hr, higher radiation exposure than properly using an XRF for a week let alone a day. This may explain why some pilots are the way they are...
My thoughts on keeping an XRF pristine:
- Check the XRF film before, during and after use. Replace the film if in any doubt about its condition. Don’t use a brush to clean the XRF window as you risk forcing dust and particles into the nose of the XRF if the film is split.
- Use an XRF foot/tripod. Not only does it minimise potential radiation exposure, it keeps the XRF stable for the duration of the shot, minimising the user's accidental but inevitable movement, rocking the underlying rock sample or soil sample bag into/through the XRF window.
- Keep the XRF over the sample, not underneath it. Dust, sand and grit don’t fall up. If you’re using a workstation where the XRF is inverted under the sample chamber, then make doubly sure the XRF film is pristine and wipe every soil bag free of dust before placing it in the workstation chamber.
- When not using the XRF, power it down, wipe it free of dust and place it in its Pelican case. When the XRF is out of its case, keep the Pelican case lid closed. Simples. Always transport the XRF in its case.
- Don’t use the XRF on a wobbly table. Don’t use an XRF near the edge of a table. If you are between shots, lay the XRF on its side, on a cloth.
- Work in a clean area, preferably an airconditioned space. Establish an assaying workflow. If you’re doing soil grids, bring the samples back to the camp
- Know your instrument. Be cool and don’t panic. If you accidentally press the trigger, press it again to stop it, whist ensuring that it's not pointed towards anyone. Negative points to the wombat that drops the XRF and runs, screaming for mum.
08 August 25
How to get different assays of the same sample from your XRF...
I recently reviewed a remote antimony prospect. Dry conditions. Very little soil over basement so soil sampling for this ground was fast and furious: brush off the leaf litter, sieve 1kg of material to get 200g of <0.3mm, place into a very thin ziplock bag, Shoot. We used a soil foot for hands-free stability to XRF for 90 seconds on the rear tray of a Toyota. Geochemistry results were a textbook example of elevated Antimony and Arsenic aligned over mineralised veins.
Back home, out of curiosity, I took four of these thin-bagged soils and put them into our flash new workstation. Frustratingly, light element readings were significantly different (Mg, Si, Al, K) as was Cr. Heavier elements were fine but at low levels when approaching detection limits, the workstation samples registered zero more than the soil foot tripod samples.
We are talking the same sample bags here, which are for all intents and purposes homogeneous. My suspicion was density differences. With the soil foot sample I can roll the bag up a little to better compress the sample before placing the full weight of the XRF nose on the bag. With the workstation I can only place the soil sample bag over the XRF window, close the lid and shoot.
XRF cups and pressed pellets of each sample were then made to compare and validate density. My XRF cups take about as much time to make as a pressed pellet... assemble the cup and then press in a few grammes at a time with a drift to get as dense a sample as possible. And don't scrimp on the sample - try to get >12mm thickness. Pop in a pre-punched cardboard disc, cotton wool and finally the cap. My preference is to make a pressed pellet any day... these XRF cups are a lot of finicky steps and you are still shooting through a film.
No surprises with the results… pressed pellets win for light element sensitivity, XRF cups are good, but thin sample bags do the job just as well for As, Sb. The table below shows how each of the five sample methods report light and heavy elements.
So there you go, there is a density effect at work from loose powder in a bag through to pressed pellets… but there is also an XRF film effect: I used one of our film-less XRF cups to shoot each sample: you thumb-press the sample into an open top capsule with a rim. Wipe clean and the capsule provides a flat sample that the XRF nose can settle on without ingesting soil/dust. You have to be careful but it works beautifully, taking a minute per sample to prepare and is almost as accurate as a pressed pellet. You shoot with the XRF gun over the sample, so there is less chance of dusting your precious XRF.
Taking away the XRF film helps but unless you press your own pellets, do you really want to increase the risk of dusting your pXRF innards for a more accurate light element result? And does it matter? I don’t think so… as long as you are consistent with your sample preparation and sample reading methods. Consistency is crucial to extracting the most value out of your XRF. And don't forget to insert regular blanks/standards/repeats. This legitimises your data.
I’m all for thin ziplocks: fast and appropriate for heavier elements. The Ziplock bagged sample protects the underlying XRF nose from dust and soil. Workstations are safer, don’t leak X-rays and are perfect for large batches of samples. Do your orientation study… figure out what works for your requirements... then be fast…
Not as fast ‘n furious as Vin Diesel, but fast and fit-for-purpose enough for quality real-time soil programmes. I'm keen to hear
If LIBS and XRF are of potential interest for your exploration programmes, please contact us at Realtime to discuss. You can contact us through LinkedIn, our website libsxrf.com, or [email protected].
How to get different assays of the same sample from your XRF...
I recently reviewed a remote antimony prospect. Dry conditions. Very little soil over basement so soil sampling for this ground was fast and furious: brush off the leaf litter, sieve 1kg of material to get 200g of <0.3mm, place into a very thin ziplock bag, Shoot. We used a soil foot for hands-free stability to XRF for 90 seconds on the rear tray of a Toyota. Geochemistry results were a textbook example of elevated Antimony and Arsenic aligned over mineralised veins.
Back home, out of curiosity, I took four of these thin-bagged soils and put them into our flash new workstation. Frustratingly, light element readings were significantly different (Mg, Si, Al, K) as was Cr. Heavier elements were fine but at low levels when approaching detection limits, the workstation samples registered zero more than the soil foot tripod samples.
We are talking the same sample bags here, which are for all intents and purposes homogeneous. My suspicion was density differences. With the soil foot sample I can roll the bag up a little to better compress the sample before placing the full weight of the XRF nose on the bag. With the workstation I can only place the soil sample bag over the XRF window, close the lid and shoot.
XRF cups and pressed pellets of each sample were then made to compare and validate density. My XRF cups take about as much time to make as a pressed pellet... assemble the cup and then press in a few grammes at a time with a drift to get as dense a sample as possible. And don't scrimp on the sample - try to get >12mm thickness. Pop in a pre-punched cardboard disc, cotton wool and finally the cap. My preference is to make a pressed pellet any day... these XRF cups are a lot of finicky steps and you are still shooting through a film.
No surprises with the results… pressed pellets win for light element sensitivity, XRF cups are good, but thin sample bags do the job just as well for As, Sb. The table below shows how each of the five sample methods report light and heavy elements.
So there you go, there is a density effect at work from loose powder in a bag through to pressed pellets… but there is also an XRF film effect: I used one of our film-less XRF cups to shoot each sample: you thumb-press the sample into an open top capsule with a rim. Wipe clean and the capsule provides a flat sample that the XRF nose can settle on without ingesting soil/dust. You have to be careful but it works beautifully, taking a minute per sample to prepare and is almost as accurate as a pressed pellet. You shoot with the XRF gun over the sample, so there is less chance of dusting your precious XRF.
Taking away the XRF film helps but unless you press your own pellets, do you really want to increase the risk of dusting your pXRF innards for a more accurate light element result? And does it matter? I don’t think so… as long as you are consistent with your sample preparation and sample reading methods. Consistency is crucial to extracting the most value out of your XRF. And don't forget to insert regular blanks/standards/repeats. This legitimises your data.
I’m all for thin ziplocks: fast and appropriate for heavier elements. The Ziplock bagged sample protects the underlying XRF nose from dust and soil. Workstations are safer, don’t leak X-rays and are perfect for large batches of samples. Do your orientation study… figure out what works for your requirements... then be fast…
Not as fast ‘n furious as Vin Diesel, but fast and fit-for-purpose enough for quality real-time soil programmes. I'm keen to hear
If LIBS and XRF are of potential interest for your exploration programmes, please contact us at Realtime to discuss. You can contact us through LinkedIn, our website libsxrf.com, or [email protected].
Getting five different assays from the same sample... from five sampling methods. Your most accurate readings are with a pressed pellet.
Photo of XRF cup, open cup and pressed pellet.
Photo of XRF cup, open cup and pressed pellet.
50mm x 50mm channel cut into massive outcrop with a demolition saw, Dryden Ontario. This sampler was an artisan!
30july25
What's a representative sample?
It's more than just not picking out the shiny bits.
I thought I had sampling sorted until we had a massive trenching programme in Tanzania. We did our best but I could see we needed help, which came by the way of Paul Howe, a surveyor by training but a superb teacher and a sampling Master. Our meandering trenches magically straightened, sampling protocols/improved documentation introduced and all of a sudden we had uniform sample channels and each of our sample bags weighed the same. Paul cheerfully trained the Mahenge locals into sampling gurus and we massively benefitted from these best practices as we advanced a discovery into a world class graphite JORC Resource.
Anyway, fast forward to Canada some years later, standing in front of a massive wall of coarse pegmatite, clutching a LIBS and wondering how to sample 20cm mineral crystals with a 100micron beam instrument. It could have been hundreds of readings per metre and we wouldn't be sure. How could this be properly sampled? What would Paul do?
We saw some amazing diamond demolition saw sampling of outcrop at a nearby gold prospect and this got me thinking...
A 50mm x 50mm channel demolition saw channel sample is great. 2,500cm3/m. In my opinion, as good as a core sample.
But what about a 1cm deep x 1cm wide channel sample? 100cm3/m of sample. Taking this further, what about a 5mm wide by 1cm deep channel sample? 50cm3/m. Is this just as representative? Assume that there is no surface oxidation veneer.
I ask this because we modified a portable diamond blade grinder to cut a 5mm wide by 1cm deep channel sample, captured with a battery powered vacuum sampler. This uses a pair of cyclones that capture pretty much all of the sample sawn out of the rock and its big advantage is that the material is typically sized <0.2mm all the way down to fine dust.
The best part of this method is that it's virtually dust free. Dry diamond sawing a rock with almost no dust emission is remarkable to see and a lot healthier for the saw operator.
We have sawn up to 1m per minute to capture >120g per metre. Saw a metre, stop, 1 minute to empty the cyclones of that 1m interval, resume sampling. Your only limitation is carrying sufficient batteries. If you can bring a genset that can take mains powered saws and vacuums - even better, as then you can do this all day long. There are compromises: it is a small sample volume and it only cuts 10mm into the rock face. I can cut deeper/wider but let's leave this for now. The Advantage is its fast and delivers a homogeneous sample that can easily be XRF or LIBS assayed.
My point here is that this fine sample is pre-homogenised and with a 100 micron sieve, can be slide mounted (or pelletised) and LIBS sampled there and then with <1g of sample. Then take the remaining 120g sample and send it to a lab. Would you trust this channel method as a representative sampling technique? Is it homogeneous?
I'm keen to hear your thoughts.
What's a representative sample?
It's more than just not picking out the shiny bits.
I thought I had sampling sorted until we had a massive trenching programme in Tanzania. We did our best but I could see we needed help, which came by the way of Paul Howe, a surveyor by training but a superb teacher and a sampling Master. Our meandering trenches magically straightened, sampling protocols/improved documentation introduced and all of a sudden we had uniform sample channels and each of our sample bags weighed the same. Paul cheerfully trained the Mahenge locals into sampling gurus and we massively benefitted from these best practices as we advanced a discovery into a world class graphite JORC Resource.
Anyway, fast forward to Canada some years later, standing in front of a massive wall of coarse pegmatite, clutching a LIBS and wondering how to sample 20cm mineral crystals with a 100micron beam instrument. It could have been hundreds of readings per metre and we wouldn't be sure. How could this be properly sampled? What would Paul do?
We saw some amazing diamond demolition saw sampling of outcrop at a nearby gold prospect and this got me thinking...
A 50mm x 50mm channel demolition saw channel sample is great. 2,500cm3/m. In my opinion, as good as a core sample.
But what about a 1cm deep x 1cm wide channel sample? 100cm3/m of sample. Taking this further, what about a 5mm wide by 1cm deep channel sample? 50cm3/m. Is this just as representative? Assume that there is no surface oxidation veneer.
I ask this because we modified a portable diamond blade grinder to cut a 5mm wide by 1cm deep channel sample, captured with a battery powered vacuum sampler. This uses a pair of cyclones that capture pretty much all of the sample sawn out of the rock and its big advantage is that the material is typically sized <0.2mm all the way down to fine dust.
The best part of this method is that it's virtually dust free. Dry diamond sawing a rock with almost no dust emission is remarkable to see and a lot healthier for the saw operator.
We have sawn up to 1m per minute to capture >120g per metre. Saw a metre, stop, 1 minute to empty the cyclones of that 1m interval, resume sampling. Your only limitation is carrying sufficient batteries. If you can bring a genset that can take mains powered saws and vacuums - even better, as then you can do this all day long. There are compromises: it is a small sample volume and it only cuts 10mm into the rock face. I can cut deeper/wider but let's leave this for now. The Advantage is its fast and delivers a homogeneous sample that can easily be XRF or LIBS assayed.
My point here is that this fine sample is pre-homogenised and with a 100 micron sieve, can be slide mounted (or pelletised) and LIBS sampled there and then with <1g of sample. Then take the remaining 120g sample and send it to a lab. Would you trust this channel method as a representative sampling technique? Is it homogeneous?
I'm keen to hear your thoughts.
29 July 2025
XRF calibration blanks
At Realtime we are big fans of well calibrated LIBS and XRF instruments… possibly to the point of obsession. Why use a spectrometer that’s out of tune?
Having lost our Quartz blank to another XRF for a drill programme, we searched for a source of high purity quartz glass - it offers the most consistent assays with pXRFs. We ordered samples from a bunch of vendors then began testing…
We learned that there is Quartz glass and there is quartz glass. One source stood out for its quality so we bought a large enough batch to last for years. Our XRF likes this blank, showing lots of silica and very, very few minor elements. We are in the process of getting a few of the quartz slugs laboratory assayed to validate their purity but at this point tend to believe the manufacturer’s claim of <100ppm total impurities.
Silica Relative Standard Deviations (RSDs) of 0.06%-0.17% are the best results we have shot from our handheld XRF. This is plain impressive.
Like all of our pressed pellet products, we have shoehorned this 25mm tall blank into a screw top capsule. This minimises the potential for contamination and protects the glass slug from damage.
Anyway, these quartz blanks are great to warn of XRF contamination of the film or detector… for all elements except of course silicon. For silicon measurement, Our Zero blank is made from a mineral-free polymer which in theory contains only H, C, O, but we see a small amount of reported Al, Fe, +/-Si, etc. Lab ICP assays show nothing of consequence in the Zero matrix apart from 125ppm Al, so I think its spectral line interference and software more so than actual contaminants.
I have been told that every XRF will show slightly different numbers based upon its tube, power, time settings, machine age, software, calibration settings, XRF film etc. This is not an issue. What’s important is to have standards with which you can baseline your XRF and monitor ongoing assays over time. We use a quartz glass blank, a Zero polymer and also an array of pressed pellets similar in matrix to what we are XRF'ing at the time. If you’re exploring for gold and using Arsenic as an indicator, then a CRM or two in the Arsenic range you are looking at may be useful.
When you are doing XRF soils/drill samples/rock chips, consider how to incorporate sampling QAQC. If you were putting these samples into a lab, you would be doing 1 in 20 repeats/blanks/standards? Do something similar with your XRF... its no big effort and it does give you more confidence in your spectrometer.
Feel free to contact us for more information.
Having lost our Quartz blank to another XRF for a drill programme, we searched for a source of high purity quartz glass - it offers the most consistent assays with pXRFs. We ordered samples from a bunch of vendors then began testing…
We learned that there is Quartz glass and there is quartz glass. One source stood out for its quality so we bought a large enough batch to last for years. Our XRF likes this blank, showing lots of silica and very, very few minor elements. We are in the process of getting a few of the quartz slugs laboratory assayed to validate their purity but at this point tend to believe the manufacturer’s claim of <100ppm total impurities.
Silica Relative Standard Deviations (RSDs) of 0.06%-0.17% are the best results we have shot from our handheld XRF. This is plain impressive.
Like all of our pressed pellet products, we have shoehorned this 25mm tall blank into a screw top capsule. This minimises the potential for contamination and protects the glass slug from damage.
Anyway, these quartz blanks are great to warn of XRF contamination of the film or detector… for all elements except of course silicon. For silicon measurement, Our Zero blank is made from a mineral-free polymer which in theory contains only H, C, O, but we see a small amount of reported Al, Fe, +/-Si, etc. Lab ICP assays show nothing of consequence in the Zero matrix apart from 125ppm Al, so I think its spectral line interference and software more so than actual contaminants.
I have been told that every XRF will show slightly different numbers based upon its tube, power, time settings, machine age, software, calibration settings, XRF film etc. This is not an issue. What’s important is to have standards with which you can baseline your XRF and monitor ongoing assays over time. We use a quartz glass blank, a Zero polymer and also an array of pressed pellets similar in matrix to what we are XRF'ing at the time. If you’re exploring for gold and using Arsenic as an indicator, then a CRM or two in the Arsenic range you are looking at may be useful.
When you are doing XRF soils/drill samples/rock chips, consider how to incorporate sampling QAQC. If you were putting these samples into a lab, you would be doing 1 in 20 repeats/blanks/standards? Do something similar with your XRF... its no big effort and it does give you more confidence in your spectrometer.
Feel free to contact us for more information.
One of many prototype slides trialled in the process. This one is veneered with Mt Cattlin spodumene. Rectangular LIBS raster marks are visible.
23 July 25 Pressed pellet free LIBS
When we purchased our LIBS we were less than happy to learn, after the fact, that we needed to mill and pelletise samples. Refresher courses in sampling theory, sample sizing and statistics confirmed this, but not as clearly as firing up the LIBS to see how it performed assaying known and unknown lithium bearing rocks… with a multitude of preparation methods.
We grimly acknowledged that milling rocks in the field was necessary and purchased a portable rock pulveriser. We also developed an alternative to this with a portable diamond saw that both milled and vacuum collected the sample. Good for rocks and good for core.
We were not too keen to lug a 50kg pellet press around paddocks, nor the benchtop of paraphernalia that goes with it. Frankly, making pressed pellets is painful. They work wonderfully and are the benchmark LIBS method, but we wanted something faster.
How? It all comes down to how to present a competent sample to a 50-100micron diameter laser beam… You want to present the LIBS with a flat, homogeneous sample, competent enough to withstand at least one laser ablation shot. Could we do this with a veneer of pulverised sample mounted onto a substrate?
We trialled dozens of emulsions, polymers, films, tapes, glues and materials… in many permutations and combinations. Cryo, room temperature, oven and kiln fired. Most failed, some sort-of-worked and encouragingly, a couple of methods showed wonderful promise. Along the way we learned that lithium is in lot of materials…
We settled on one method that is fast and highly repeatable. It generates low Relative Standard Deviations, at times lower than comparative pressed pellets, so we knew we were onto something tangible and backed with statistics. The slide method does not rely on pressure, so density variation problems can be tossed out the window.
One issue is that slides often report assays at different levels to pressed pellets, so a custom calibration is required that is designed for your slide samples and matrix… that’s fine. Thanks Sciaps for patiently showing us the ins and outs of calibration. We then made our own custom Reference Material and CRM slides, they work a treat.
The takeaway is that you can prepare LIBS samples in the field with quantitative assay capability: We can do lithium in soils down to 10-15ppm… in the paddock.
Quickly, Accurately, Repeatable and Safely is Our vision.
For soils and RC drilling, this is a dream process. For diamond drilling and rock samples, sorry but you have to do some more sample prep. Again, we are not setting out to compete with assay laboratories, we want quantitative assay methods to make informed decisions.
We still think you need good geologists and exploration teams to go into the field, kick rocks, map, sample, think and determine whether you should keep spending, spend more or run away. Assays help make these decisions. A lab in the back of the Toyota is our vision to help make better informed decisions, in real time.
So if you want your LIBS to do more than act as a binary “YES there is lithium or NO there is not”, talk to us. If LIBS and XRF are of potential interest for your exploration programmes, please contact us to discuss: through LinkedIn, our website #Libsxrf.com, or [email protected]
When we purchased our LIBS we were less than happy to learn, after the fact, that we needed to mill and pelletise samples. Refresher courses in sampling theory, sample sizing and statistics confirmed this, but not as clearly as firing up the LIBS to see how it performed assaying known and unknown lithium bearing rocks… with a multitude of preparation methods.
We grimly acknowledged that milling rocks in the field was necessary and purchased a portable rock pulveriser. We also developed an alternative to this with a portable diamond saw that both milled and vacuum collected the sample. Good for rocks and good for core.
We were not too keen to lug a 50kg pellet press around paddocks, nor the benchtop of paraphernalia that goes with it. Frankly, making pressed pellets is painful. They work wonderfully and are the benchmark LIBS method, but we wanted something faster.
How? It all comes down to how to present a competent sample to a 50-100micron diameter laser beam… You want to present the LIBS with a flat, homogeneous sample, competent enough to withstand at least one laser ablation shot. Could we do this with a veneer of pulverised sample mounted onto a substrate?
We trialled dozens of emulsions, polymers, films, tapes, glues and materials… in many permutations and combinations. Cryo, room temperature, oven and kiln fired. Most failed, some sort-of-worked and encouragingly, a couple of methods showed wonderful promise. Along the way we learned that lithium is in lot of materials…
We settled on one method that is fast and highly repeatable. It generates low Relative Standard Deviations, at times lower than comparative pressed pellets, so we knew we were onto something tangible and backed with statistics. The slide method does not rely on pressure, so density variation problems can be tossed out the window.
One issue is that slides often report assays at different levels to pressed pellets, so a custom calibration is required that is designed for your slide samples and matrix… that’s fine. Thanks Sciaps for patiently showing us the ins and outs of calibration. We then made our own custom Reference Material and CRM slides, they work a treat.
The takeaway is that you can prepare LIBS samples in the field with quantitative assay capability: We can do lithium in soils down to 10-15ppm… in the paddock.
Quickly, Accurately, Repeatable and Safely is Our vision.
For soils and RC drilling, this is a dream process. For diamond drilling and rock samples, sorry but you have to do some more sample prep. Again, we are not setting out to compete with assay laboratories, we want quantitative assay methods to make informed decisions.
We still think you need good geologists and exploration teams to go into the field, kick rocks, map, sample, think and determine whether you should keep spending, spend more or run away. Assays help make these decisions. A lab in the back of the Toyota is our vision to help make better informed decisions, in real time.
So if you want your LIBS to do more than act as a binary “YES there is lithium or NO there is not”, talk to us. If LIBS and XRF are of potential interest for your exploration programmes, please contact us to discuss: through LinkedIn, our website #Libsxrf.com, or [email protected]
Our first custom-made, high purity quartz glass pellets... before bonding into capsules
Element repeatability of Oreas 45f, expressed as % Relative Standard Deviation.
10 July 25
XRF and LIBS pellet repeatability
We are pretty happy with the quality of our binder-free pressed pellet CRMs and Reference Materials for XRF and LIBS. Pleasingly, our customers and end users are too. But its one thing to say you have a good product and its another thing to prove it. Saying so doesn’t cut it.
I made 24 CRM pellets for a recent series of tests. Four OREAS CRMs: a soil, a tungsten ore, a zinc ore and barren granodiorite. Pressed pellets ranged from 3g-10g of sample and for good measure, an XRF cup of each material. That test was to measure potential infinite thickness effects and to measure elements approaching XRF detection limits. We sectioned additional pellets to measure sample density. I’ll publish the tests results once we get a few more rock types included.
Our pressed pellets performed better than expected. I shot the same CRM pellet six times, then one shot of different weight pellets to see how repeatable they were on our trusty XRF. The single pellet test was turned 30-40 degrees between each shot. I then made six identical weight pellets and shot each of them once for comparison.
Major element repeatability was excellent and minor elements approaching detection limits were more variable (as expected). These XRF pellets are more than fit for purpose. Relative Standard Deviation (RSD) is my proxy for repeatability and homogeneity - the lower, the better. Silicon assays are close to laboratory, so if you use pXRF data to determine underlying lithology, this is pretty useful. Arsenic RSDs were high but that’s because As at 9.67ppm was very low to start with… approaching detection limits. Nevertheless, the XRF shot an impressive 9-13ppm range but this meant the RSD was a high 15.3%.
XRF cups were also tested for repeatability. Testing returned larger variation due to lower sample densities and shooting through an XRF film. At least XRF cups are consistently inaccurate for light elements… and you may not detect some low level elements because of shooting through an XRF film. Nevertheless, XRF cups are convenient to make in the field and are better than shooting samples through plastic bags.
Its horses for courses – what elements do you want for your field work? pXRF soil programmes should start with an orientation survey to see how samples perform in the lab and in the field. Shooting thru RC bags may work, as may shooting thru super thin sample bags, XRF cups or having to press pellets. You want your XRF calibrated to the local matrix.
So chat to OREAS if you want to use their pressed pellet CRMs. We know they are good… not just because we pelletise them… our pXRF data clearly verifies their performance.
Chat to us at Realtime if you want your own project’s rocks and soils characterised and pelletised as reference materials.
XRF and LIBS pellet repeatability
We are pretty happy with the quality of our binder-free pressed pellet CRMs and Reference Materials for XRF and LIBS. Pleasingly, our customers and end users are too. But its one thing to say you have a good product and its another thing to prove it. Saying so doesn’t cut it.
I made 24 CRM pellets for a recent series of tests. Four OREAS CRMs: a soil, a tungsten ore, a zinc ore and barren granodiorite. Pressed pellets ranged from 3g-10g of sample and for good measure, an XRF cup of each material. That test was to measure potential infinite thickness effects and to measure elements approaching XRF detection limits. We sectioned additional pellets to measure sample density. I’ll publish the tests results once we get a few more rock types included.
Our pressed pellets performed better than expected. I shot the same CRM pellet six times, then one shot of different weight pellets to see how repeatable they were on our trusty XRF. The single pellet test was turned 30-40 degrees between each shot. I then made six identical weight pellets and shot each of them once for comparison.
Major element repeatability was excellent and minor elements approaching detection limits were more variable (as expected). These XRF pellets are more than fit for purpose. Relative Standard Deviation (RSD) is my proxy for repeatability and homogeneity - the lower, the better. Silicon assays are close to laboratory, so if you use pXRF data to determine underlying lithology, this is pretty useful. Arsenic RSDs were high but that’s because As at 9.67ppm was very low to start with… approaching detection limits. Nevertheless, the XRF shot an impressive 9-13ppm range but this meant the RSD was a high 15.3%.
XRF cups were also tested for repeatability. Testing returned larger variation due to lower sample densities and shooting through an XRF film. At least XRF cups are consistently inaccurate for light elements… and you may not detect some low level elements because of shooting through an XRF film. Nevertheless, XRF cups are convenient to make in the field and are better than shooting samples through plastic bags.
Its horses for courses – what elements do you want for your field work? pXRF soil programmes should start with an orientation survey to see how samples perform in the lab and in the field. Shooting thru RC bags may work, as may shooting thru super thin sample bags, XRF cups or having to press pellets. You want your XRF calibrated to the local matrix.
So chat to OREAS if you want to use their pressed pellet CRMs. We know they are good… not just because we pelletise them… our pXRF data clearly verifies their performance.
Chat to us at Realtime if you want your own project’s rocks and soils characterised and pelletised as reference materials.
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