Hi, I'm researching about MoO2Cl2 and its molybdenum impurity such as MoO2, MoO3, MoOCl4.
While I'm searching about analysis tool, I find XANES and study about it.
And, I have a question about XANES.
Can XANES analyze ppm level of metal and oxidation state?
For example, In my case, detect extremely low concentration of MoO2, MoO3, MoOCl4 in high concentration of MoO2Cl2.
Thanks.
Dear Sungbin Park ,
in addition to the answer of Artur Braun ,
in your case of low extremely low concentration of MoO2, MoO3, MoOCl4 combined with in high concentration of MoO2Cl2 you cannot differentiate between these two groups. The XANES (and the Mo edge profile) of MoO2Cl2 will dominate the XANES (and the Mo edge profiles) of MoO2, MoO3, MoOCl4.
Sorry, there is no chance to 'address' MoO2Cl2, MoO2, MoO3, MoOCl4 separately.
Nevertheless oxidation state evaluation is possible via XANES/edge profile analysis in the ppm regime using fluorescence mode as Arthur mentioned above.
For example please have a look at:
Article An X-ray Absorption Near-Edge Structure (XANES) Study on the...
Here we had Mn concentrations in the range of about 30ppm to 1200ppm (see table 1 therein).
Artur Braun
Resonant excitation with respect to EXAFS, XANES, NEXAFS is not known to me.
However oxidation state approaches via resonant x-ray emission at K-edges are known.
But I think also here the Mo signal of MoO2Cl2 will dominate that of MoO2, MoO3, MoOCl4.
For example in
Article Probing Physical Oxidation State by Resonant X‐ray Emission ...
the oxidation state is analyzed via resonant x-ray emission.
The basic tool here is the the K-beta profile of the K-beta fluorescence taken at specific excitation energies around the K-edge.
So also here when having different concentrations of the specific atom species, the output here (i.e. the K-beta profile) will be dominated by the K-beta of the main component (here the Mo K-beta of MoO2Cl2). To my opinion one is not able to separate the Mo K-beta profile(s) of MoO2, MoO3, MoOCl4 from the Mo K-beta profile of MoO2Cl2 when simultaneously present in the sample.
Resolving ppm level concentrations of different oxidation states seems very unrealistic if the element of the edge you are looking at is present in vastly higher concentrations. While they have a different spectrum, you would have to disentangle the signals afterwards. Extracting a shifted spectrum from an oxidation state that is 1000x weaker than your main signal would be an amazing feat indeed.
The story would be very different if you where looking for an element that is not within your base compound, in which case you could address that specific absorption edge and learn its main oxidation states rather easily.
Resonant Inelastic X-ray Scattering would likely deliver the information you want, as the additional oxidation state might pop up as an additional peak instead of on a background of the main compound. But this is a very photon hungry technique in the first place so a ppm-level sample concentration might just not give enough signal even when you are measuring at a bright synchrotron.
I am not an expert on this, but have you looked into optical (raman) spectroscopy?
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