Hello,
I need to analyze for Xe. To that end I have gone through the process of setting up a virtual standard. Everything is OK so far. Now I need to indicate that some elements interfere with Xe but don't see a straight-forward way of doing so since Xe doesn't populate under "standard assignments". I tried to add these interferences by going to another standard (e.g. U), going down the list of elements until I find Xe, and then adding in U as an interference. Then when I press "analyze", I get the following messege: "No interference counts on interference standard 832 for Xe for sample 832 Uranium". How do add in elements that interfere with a virtual standard?
Karen
Hi Karen,
Yes, Philipp Poeml has made the same point. PFE doesn't yet support interference standards for virtual standards yet. It's on the "to do" list however... :)
Karen,
I just thought of something... please send me a small test file with the standards acquired (normal and virtual), just without the interference assignments.
Hi, I had some kind of workaround for that, but can't remember now. If interested, I will look it up.
Yes, I was correcting for some La overlap on Xe. I built myself a new software Xe standard that was not virtual and had the PfE correction thing do the rest.
What is your solution, John?
I would be interested in know what your work around is. I have been given 120 hours to figure out everything one needs to know about analyzing irradiated fuel and don't have a lot of time to consider work arounds. I can envision how one would handle one element that overlaps, but when there is more than one, it gets complicated.
Karen
For my workaround: It is not easy to explain. It involves in messing with the access database file (mdb) and so on. To put it simple: You make a Xe standard. Then you measure it. Then you open the raw data file and you change the intensity of the fake Xe standard to whatever your virtual intensity is. Then you can use it as a "normal" standard and the interference correction works.
I think I might be able to implement interference standards for a virtual standard in Probe for EPMA. I'm working at Probe Software today, so if one of you can send me a small test file with a normal La std and a Xe virtual standard, I would like to test that implementation today if that works for you two...
Hi John, My lab is already closed for today. I might try and prepare something for you tomorrow.
Ok, no worries, Karen sent me a very nice test file with Xe and La! From this I was able to find the problem and fix it!
If you download the latest PFE update you both will now be able to specify interference corrections on elements that are utilizing the virtual standard intensity feature!
john
Everything is fine.
Thanks for implementing this overlap correction thing. For us this will be very helpful in the future!
I just updated and will hopefully give it a try tomorrow. Thanks so much for doing this!
Karen
Here is an updated screen shot of the virtual standard intensity dialog showing Philipp Poeml's virtual standard calculation for Am Ma using Pu and Cm actual standard intensities as calibration points:
(https://smf.probesoftware.com/gallery/1_17_02_18_3_07_18.png)
I guess this means that he has plutonium and curium standards, but no americium standard!
By the way, I'm reading the new book "The Disappearing Spoon: And Other True Tales of Madness, Love, and the History of the World from the Periodic Table of the Elements". It's a good read, lots of element trivia. Some I already knew of, but a lot I didn't.
https://www.amazon.com/Disappearing-Spoon-Madness-Periodic-Elements/dp/0316051640
Here's a tip for using the virtual standard feature in PFE:
After peaking up on your two measured elements, note the actual spectrometer position "offsets" from the theoretical positions as shown in in log window:
On and Off Peak Positions:
ELEM: sr la rb la si ka al ka
ONPEAK 78416.0 28465.0 81309.0 32482.0
OFFSET 27.2891 23.2559 145.617 -16.029
HIPEAK 83343.8 29779.5 82225.8 34493.1
LOPEAK 74070.1 24666.4 80342.0 30718.9
HI-OFF 4927.80 1314.50 916.797 2011.08
LO-OFF -4345.9 -3798.6 -967.00 -1763.1
Clearly these offsets are for a Cameca instrument!
Then apply the average of the offsets for the two measured elements utilized for the virtual measurements, and then apply that offset value to the virtual element spectrometer position. The idea being that if the two measured elements on that spectrometer are offset by say 10 units, then the spectrometer position of the virtual element (in between those two elements) will also probably be offset by the same amount.
Hi All
One of the grad students here who is studying the mantle wants to see if he can stuff noble gases into basaltic glasses at high pressure and then measure them on the microprobe. I am dubious of the results of the experiments even holding onto the gas long enough to get the sample carbon coated and into the probe without it losing its entire reservoir of gas (if it ever had any), but that is part of the challenge.
1) Has anyone ever measured noble gases in anything (glass or mineral) by microprobe before? If yes, anything special to look out for?
2) Does anyone have any idea what I may use as a standard? I can just get net counts on the unknown, but is there any way to quantify them? The student is going to try argon first. I wasn't sure if there might be an amphibole out there that contains argon.
Thanks
Joe
You'll want to use the "virtual standards" feature in Probe for EPMA to create a virtual noble gas standard using two other element emission lines on either side of the noble gas emission line on that spectrometer. See the beginning of this topic.
You get about 10% or better accuracy using the virtual standard method if you are careful.
John
Very cool you can generate a virtual standard for a noble gas. I read the help section of PfE. I am just starting with PfE, so forgive my idiot questions. I understand that you use the two adjacent elements peaks (K and Cl) to best determine the Ar peak position. I assume the virtual "standard" is considered 100% pure Ar, correct? The virtual intensity for the Ar is simply an estimated peak intensity based on the Cl and K standard peak heights, correct? Thus, your 10% error estimate.
Thanks
Joe
As seen in this screen shot, one actually needs three standards for this virtual standard calculation:
https://smf.probesoftware.com/index.php?topic=179.msg6743#msg6743
The first standard is the virtual standard itself which does not actually exist except as a composition in the standard database. It could be a pure element, or any other composition, so long as the virtual element in question is present in the virtual standard composition.
The other two standards are standards that you actually have in your instrument. For example, for measuring Ar Ka you would want a Cl (or S) standard and a K standard, both measured on a PET spectrometer.
You tune your spectrometer to the Cl (or S) Ka peak (Cl ka on PET = ~151.3) and measure the Cl intensity on your actual Cl standard. Note the offset from the ideal position in PFE for the Cl Ka peak.
Then tune the same spectrometer to the K Ka peak (K ka on PET = ~119.7) and measure the K intensity on your actual K standard. Again, note the offset from the ideal position in PFE for the K Ka peak position.
The reason for noting these offsets, is to improve accuracy in the interpolation of the Ar intensity, by averaging the two peak offsets and applying that to your "predicted" Ar Ka spectrometer position which you will use in the Ar measurements on your unknowns as discussed here:
https://smf.probesoftware.com/index.php?topic=179.msg10578#msg10578
With the offsets from your Cl and K peaking applied to your Ar peak position, you might do better than 10% accuracy.
Hopefully your user has done some background reading and alerted you to this study https://www.nature.com/articles/nature04583, which lacks much detail but basically uses a synthetic glass that was characterised by different methods (noble gas mass spectrometry).
Note of course that He does not have any X-ray emission lines (and in any case diffuses rapidly out of high pressure glasses).
Quote from: aburnham on December 20, 2024, 06:48:17 PMHopefully your user has done some background reading and alerted you to this study https://www.nature.com/articles/nature04583, which lacks much detail but basically uses a synthetic glass that was characterised by different methods (noble gas mass spectrometry).
Note of course that He does not have any X-ray emission lines (and in any case diffuses rapidly out of high pressure glasses).
The cool thing about the virtual standard method in Probe for EPMA is that it doesn't require an actual noble gas standard! :)
Also it is worth mentioning that using a minor/trace element standard as a primary standard is problematic from a statistical point of view as explained in this presentation:
https://www.youtube.com/watch?v=mOca7-G4FvQ&ab_channel=ProbeSoftwareInc
So the virtual standard method solves both problems... :)