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> ________________________________ THIS E-MAIL AND ANY ATTACHED FILES ARE CONFIDENTIAL AND MAY BE LEGALLY PRIVILEGED. If you are not the addressee, any disclosure, reproduction, copying, distribution, or use of this communication is strictly prohibited. If you have received this transmission in error please notify the sender immediately and then delete this e-mail. 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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