Resending since it didn't seem to go out the first time.

From: Nicolich, Jeffrey
Sent: Thursday, October 08, 2015 6:30 PM
To: 'Julian Richard Tolchard'; rietveld_l@ill.fr
Subject: RE: Quantitative internal standards

Julian,

First, the best idea would be to use a NIST standard to qualify your secondary 
standard. With this in mind, you can use almost any secondary standard. Since 
you have a silica matrix you probably want to use corundum powder since the 
absorption is similar.

Have you considered using an external standard method? The advantages are:

1.       No mixing errors (inhomogeneity)

2.       The original sample is not diluted

3.       No peak overlap between standard and sample

4.       The mass absorption coefficient of the standard doesn't need to match 
the sample.

The method works very well for complicated mixtures with many phases. The 
disadvantage is that it may be more complicated to setup the method initially.

The original method is described here:
O'Connor and Raven, Application of the Rietveld refinement procedure in 
assaying powdered mixtures, Powder Diffraction Vol. 3/1, 2-6, 1988

A more practical solution by example of cement is given here:
Jansen et al, Does Ordinary Portland Cement contain amorphous phase? A 
quantitative study using an external standard method, Powder Diffraction Vol. 
26/1, 31-38, 2011

A comparison is given here. In my opinion, the choice of test samples is not 
favorable to the external standard method.
Madsen et al, Description and survey of methodologies for the determination of 
amorphous content via X-ray powder diffraction, Zeitschrift für 
Kristallographie Volume 226, Issue 12 (Dec 2011)


Best regards,
Jeff

Jeffrey Nicolich  | Principal Scientist
Grace, 62 Whittemore Ave, Cambridge, MA, 02140, USA  |  T +1 617.498.3816
jeffrey.nicol...@grace.com<mailto:rich.badming...@grace.com>
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From: rietveld_l-requ...@ill.fr<mailto:rietveld_l-requ...@ill.fr> 
[mailto:rietveld_l-requ...@ill.fr] On Behalf Of Julian Richard Tolchard
Sent: Thursday, October 08, 2015 1:28 PM
To: rietveld_l@ill.fr<mailto:rietveld_l@ill.fr>
Subject: Quantitative internal standards

Hi all,

I've been asked to do some quantification on some samples which are 
predominantly silica, which means a reasonable amorphous component is pretty 
much inevitable. I'm thus looking for a suitable internal standard for spiking, 
but as this could be quite a big project moving forwards i don't think the NIST 
standards are financially viable. Does anyone have any good sources for spikes 
to use with such light materials?

Regards,


jools

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