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NIST Standards!

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crystalgrower:
So here from the NIST archives is the certificate for the "bulk" form of glasses K-411 and K-412. 

Charles Taylor purchased these and chisel-cut/broke them up for resale. When John Rucklidge purchased these cuts at auction, he had some of them checked by XRF, more to assure that pieces were not mixed, rather than to verify NIST data. Interested parties should contact Astimex Standards directly to see if those WDS were archived. 

The EDS spectra archived at www.2spi.com were collected on the ETEC, low resolution and no Be window for low-energy peaks.  I collected better EDS in 2010 but those files were turned over to Astimex at the time of takeover. Again, asking Astimex  for the 2010 EDS plots directly would be the way to go. I had converted  them all to Excel files at the time. 

FYI the "30 glasses" mount was made only once in duplicate as a custom order and backup.  The second mount was in John's hands in 2010. 
There was no reason to suspect any contamination from polishing of other SPI special order mounts with K-411 and K-412.  The glasses were durable under the older type of petrographic polishing.  By this I mean the predecessor to the heavy-weight fast-acting polishing machines. 

Added later:  I found an old EDS for SiC that definitely had NO Al by XRF-WDS.  The Excel file is attached, and you can see what I guess is causing the false Al in other materials.  Looks like the remedy is a change of background setting.

Probeman:


--- Quote ---In the NIST K-411 and K-412 mineral glasses, one of them (K-411) is not certified for aluminum as it is apparently a zero concentration. I've never looked closely at trying to measure it myself, but I always see a few hundred PPM of Al in K-411 when measuring Al.

Has anyone made a more serious effort to characterize the NIST K-411 mineral glass for Al?
--- End quote ---


Yes, I can promise that the Al background is curved due to the tail of the Si Ka peak. Here is a figure from my traces in quartz paper that shows this very thing (data from USGS JEOL instrument):



Basically utilizing a linear fit with typical background offsets results in a decrease of about 60-70 PPM for Al ka in a quartz matrix. A link to the full paper is here:

https://epmalab.uoregon.edu/pdfs/3631Donovan.pdf

But this more recent paper is essentially a followup on EPMA trace methods (warning: a lot of statistics!) including using the MAN correction for point analyses and quantitative x-ray maps:

The amazing thing is that the MAN method (when combined with the blank correction for improved accuracy), is that it gives better sensitivity for trace elements (in half the time). 

https://epmalab.uoregon.edu/publ/A%20new%20EPMA%20method%20for%20fast%20trace%20element%20analysis%20in%20simple%20matrices.pdf

And one doesn't have to worry about curved backgrounds *or* off-peak interferences!   8)

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