I would like to fin out more information about which type of material (ideally pharmaceutical compounds) could be suitable to perform both qualitative and quantitative Powder X-ray diffraction proficiency testing.
Many thanks,
Antonio
With many pharmaceutical materials we see typical effects/problems like missing particle statistics or strong preferred orientation. What worked very well for us is Tetracycline. The pattern has many peaks over the whole angular range, it is highly crystalline and it shows not too much preferred orientation
We used that compound as crystalline model substance in mixtures to test phase quantification methods for crystalline/amorphous phase mixtures:
Conference Paper Rietveld amorphous quantification, now even more painless
Hi Thomas,
Many thanks for your reply.
Did you use pure Tetracycline? Also, is the compound suitable both for quantitative and qualitative tests?
Also, do you think mannitol could be used as well?
Thanks again,
Antonio
Hello Antonio,
Yes, it was pure Tetracycline from Sigma-Aldrich, We have lots of different pharmaceutical/organic substances in the cabinet,.We tried them all, the tetracycline gives the "nicest" unbiased pattern without too much/complex sample preparation. Since it was good for Quantitative experiments I would guess its good for qualitative tests too.
Hi Thomas,
Do you anything about the potential use of mannitol for proficiency testing?
Thanks,
Antonio
Hi Antonio,
no, I personally didn't try to X-ray mannitol yet, so I have no experience with it .
As concerns the Tetracycline method, I have got a couple of questions:
1) what format/matrix (if any?) did you use for determining the amorphous quantification of your samples?
2) Is the K-factor the only measured/reported parameter?
Thanks again,
Antonio
This article contains all information about that experiment:
Conference Paper Rietveld amorphous quantification, now even more painless
Basically it was a 3 phase mixture (2 amorphous phases, 1 crystalline phase, all organic !) and we tried 2 methods for quantification, the k-factor method and the PONKCS method
So in your case the "matrixes" are those 10 mixtures you made right?
Yes, you can see it like that, I would have liked to try PLSR too, to compare more methods, but that would have required even more "knowns" and the preparation, precise weighing etc, is a job on its own.
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