The Limits of EPMA Accuracy

[Probeman]

Using the new plot option of relative percent variance (i.e., accuracy) in Probe for EPMA from the Output | Plot Standard and Unknown XY plots menu dialog:

https://smf.probesoftware.com/index.php?topic=40.msg14388#msg14388

we can quickly evaluate our secondary standard accuracy. Here for Mg Ka in MgAl2O4 using MgO as a primary standard in the FIGMAS mount from Will Nachlas:



All within 1% relative accuracy. But since we're plotting relative percent accuracy, we can plot more than a single compound, here Ti Ka in SrTiO3 and RbTiOPO4 using TiO2 as a primary standard:



And here for Fe ka in a multitude of compounds using Fe metal as the primary standard for the sulfides, and magnetite as a primary standard for the oxides, silicates and glasses:



Note that only the natural chromite is significantly outside the 1% variance accuracy limits.

[John Donovan]

In order to utilize the accuracy checks shown in the above plots, one must run their secondary standards as standard samples. Therefore, some of you have asked: how do I run my standards more than once?

Well first, to re-run ones standard samples a second time, just check the "Acquire Standard samples (again)" checkbox.  Even if you don't have an unknown sample selected, the standards will run a second time.

To run your standard even more replicates, just create an unknown sample and check the Re-Standardization Interval checkbox and enter a short interval (in hours) as seen here:



Say every hour or so. That's easy, right?