Thanks for your reply Edmund. I agree with you that I might have not chosen the right standards for my sample. In fact, XRD analysis have confirmed that Ferrite is the main form of Fe in my sample but I did not have any ferrite standards during XANES analysis. Was wondering if you happen to have any Ferrite XANES spectra by any chance?
Thanks and kind regards. Teck Kwang On 9 August 2013 16:53, Edmund Welter <edmund.wel...@desy.de> wrote: > Dear Teck Kwang Choo, > > it is the ratio of the number of (in your case) iron atoms. This ratio has > no unit. You will therefore get the same number if you calculate molar % > ratio or weight % (Except you consider the weight of the missing electron > in Fe3+... :-). Now, if you weigh your standards and want to calculate the > "number of Fe atoms" you have to consider the weight of the oxygen. That > means, the ratio you get from LCF fitting of your XAS spectra is NOT the > ratio between mol of FeO and Fe2O3, but mol FeII+ to mol FeIII+! However, > if necessary or usefull you can always calculate the latter from the > FeII/FeIII ratio using the molar weights. > > So, as a chemist I would say, stay consequently with the molar ratio and > you are on the safe side. You can always multiply the number of mol with > the molar weight, but you would only make things more complicated and end > up with the same ratio or, after multiplying with 100, percentage. > > Concerning the deviation between your result and your expectation: I would > be more nervous about the choice of reference substances. If you only use > FeO and Fe2O3 your result is only "correct" if your sample contains no > other Fe component than these two. If it contains significant amounts of > any other Fe component (even other oxides) you would better not draw any > important conclusions from the result of your analysis. > > Best regards > Edmund Welter > > > > > On 09.08.2013 05:37, Teck Kwang Choo wrote: > > Hello, > > I have been using ATHENA to perform Linear Combination Fitting (LCF) on my > XANES spectrum to quantify the amounts of Fe (II) and Fe (III) in my > samples using only FeO and Fe2O3 as standards. The results showed a > majority of Fe (II), which is contrary to what was expected. > > This made me wonder if the LCF results from XANES is a molar percentage > (mol %) or weight percentage (wt%). > > Could anyone enlighten me on this matter? > > Thanks! > > -- > Teck Kwang Choo > PhD Student > Department of Chemical Engineering > Room 225, Building 36 > Monash University > Mobile No.: 04-11489904 > > > _______________________________________________ > Ifeffit mailing > listifef...@millenia.cars.aps.anl.govhttp://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > > > > _______________________________________________ > Ifeffit mailing list > Ifeffit@millenia.cars.aps.anl.gov > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > > -- Teck Kwang Choo PhD Student Department of Chemical Engineering Room 225, Building 36 Monash University Mobile No.: 04-11489904
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