Clay samples are heated at 950 degree centigrade (LOI method) before XRF analysis. Due to which Fe percentage increases in the XRF results. It is due to the oxidation of samples during fusion. Is there any procedure to correct the Fe value within the results?
Dear Ashok
If I understand your message correctly, you are saying that the apparent Fe content of your clay increases following heat treatment of the clay at 950 deg. C, and you attribute this to oxidation of the iron. If this is what you are saying, then I suggest an alternative explanation. When you carry out the 950degC treatment of the clay, essentially all of the physical and chemical water, any carbonates, and any organic materials, will be burned off along with any other volatiles, leaving a decreased mass of material. You would then measure an "increased" amount of the remaining constituents - in fact, these have not changed, it's just that 100% of the material by mass now was less than 100% before the 950 deg. C treatment. In fact, XRF measure Fe content, not Fe oxide content - it simply calculates the oxygen content by stochiometry. So I suspect the effect you are seeing is simply the loss of other components, not the "gain" of Fe.
Kindest Regards
Paul.
Hi Jorge
I agree it's certainly possible. However, since XRF only detects the Fe content not the O content, the meaured Fe content will not change as a result of its oxidation state: this was the point I was aiming to make.
Kindest Regards
Paul.
Paul, you're right. But I think Ashok means that because of oxidation FeO becomes Fe2O3 and, thus, sample mass inceases.
Thanks a lot Paul and Jorge for your kind reply. The clay samples (attached images and XRF results) are modern fluvial sediments, collected between 15-20 m depth below surface (through drilling). The avg. Fe2O3 (T) vlaues are usually in the range of 2-5 % from the other parts of the basin. I am thereby in doubt whether the higher Fe2O3 (T) values obtained due to LOI treatment or not. Kindly suggest me whether these values can be used in interpretation.
Looking forward.
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