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Sample Preparation - Graphite digestion using HClO4 / H2SO4 with vanadium catalyst

 
I'm dissolving samples of 5-6 gram of graphite for ICP-OES analysis. I use your method of boiling perchloric/sulfuric acid mixture with Vanadium (V2O5) as catalyst, in a round bottom flask with condensor. While the first two samples dissolved in 10-20 days, some others take 50-150 days to dissolve, but I have no clue why the dissolution rate varies strongly from one sample to the next. Are the details of your method published somewhere. If not, what is the most decisive factor in the dissolution rate. Is it the perchloric/sulfuric ratio or amount of vanadium?
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admin Total posts: 529

Many of the digestion techniques referenced are described in: Decomposition Methods in Analytical Chemistry (1979), Rudolf Bock, Halsted Press, New York. This book is a very good resource and summarizes many digestion techniques, while providing an extensive reference list for more detailed information. It’s unclear as to why the digestion time scales vary so widely, though the usual suspects would include relative particle size, corresponding surface areas, is the sample periodically agitated gently, etc. The Bock book also lists other decomposition methods for graphite that might be more suitable, particularly with respect to digestion times.

Posted: 09/07/18 02:48:31

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