Re: Analysis of Oxygen

[BenjaminWade]

I had a question about Oxygen direct measurement for Cameca users. More specifically, do people use PC0 or PC2 crystal, and the pros and cons of either? This application would be attempting to measure/detect oxygen in lab altered chalcopyrite (CuFeS2)

Cheers

[Probeman]

I had a question about Oxygen direct measurement for Cameca users. More specifically, do people use PC0 or PC2 crystal, and the pros and cons of either? This application would be attempting to measure/detect oxygen in lab altered chalcopyrite (CuFeS2)

Hi Ben,
I don't have a PC0 (45 angstrom 2d), but the PC1 (W/Si 60 angstrom 2d) works fine for oxygen and we use it all the time even for trace oxygen. The PC2 (95 angstrom 2d) could be used, but the low side background is inaccessible and the count rate is much lower for oxygen. The PC2 is actually optimized for N ka.

Compare this plot on MgO:

[Probeman]

For calculation of oxygen in halogen bearing materials, while we're on the topic of oxygen analysis, you might want to check this thread:

http://smf.probesoftware.com/index.php?topic=8.msg1127#msg1127

and also the following attachments.
john

[Probeman]

Two more notes regarding measuring oxygen in mineral glasses:

[BenjaminWade]

Awesome. Looks like I will be going with the PC0 then, as unfortunately we don't have the PC1 crystal. I trawled the search of the forum I swear! Found a lot about processing C,O and halogen data, but couldn't find which crystal people generally tend to usually use.

While I am here... what standard/s to people tend to use for O? Would you use a synthetic standards like pyrope, or should you be trying to matrix match as best as you can? Also, have people noticed any systematic peak shift in the Oxygen peak from mineral to mineral, or is the peak maxima too broad to say anything conclusive?

Cheers

[Probeman]

Awesome. Looks like I will be going with the PC0 then, as unfortunately we don't have the PC1 crystal. I trawled the search of the forum I swear! Found a lot about processing C,O and halogen data, but couldn't find which crystal people generally tend to usually use.

While I am here... what standard/s to people tend to use for O? Would you use a synthetic standards like pyrope, or should you be trying to matrix match as best as you can? Also, have people noticed any systematic peak shift in the Oxygen peak from mineral to mineral, or is the peak maxima too broad to say anything conclusive?

It depends on the concentrations you are measuring. Since you are trying to determine trace oxygen in a sulfide, I think you could use almost any standard containing oxygen, since the concentration accuracy will be dominated by the background calibration.

However, if you need to get accurate oxygen in an oxide or silicate matrix you most definitely need to correct for peak shape and shift effects. This is what my APF correction is all about.

For this APF correction one should pick a reference standard that will always be used, though the APF factors can be re-normalized to any other oxygen standard assuming you have measured its peak shape with a careful scan.

But because the APF for Fe2O3 and MgO are both 1.000 relative to each other, I suggest using MgO or Fe2O3 because that is what the APF tables in my software utilize for oxygen (based on Bastin). For more information on this topic, check the PFE Reference manual:

http://www.probesoftware.com/download/PROBEWIN.pdf#page=325

[BenjaminWade]

Many thanks John, the PC2 crystal was fine using MgO.