Dissolving Graphite to Measure by ICP

Cathy questioned Paul about whether he knew of an easy way to dissolve graphite powder to measure Al, Si, Ti, Fe, Co, Ni, Mg, Ca, and total Cr by ICP. She wondered whether there are any known interferences from the graphite that may cause problems.

	RE: Dissolving Graphite to Measure by ICP Dear Cathy, Graphite is a tough one to dissolve. I believe it can be dissolved/digested using perchloric acid with vanadium added as a catalyst (addition of vanadium is very important). The method I am most familiar with uses 1 gram of sample + 18 mL sulfuric + 15 mL conc. perchloric acid in a glass digestion flask with condenser (do not use perchloric acid in a microwave furnace under any circumstances). The condenser is needed to contain any volatiles. In addition, 10 mg of V is added as either the pentoxide or in solution form as V+5 to act as a catalyst (I use 1 mL of the Inorganic Ventures' 10,000 ug/mL Vanadium standard, which is very pure and the V is in the +5 oxidation state). I have been able to decompose even charcoal and coke using the V+5 catalyst and I suspect this method would work for graphite carbon. Finally, graphite carbon would present no spectral interferences to an ICP-OES measurement. Please consult the Acid Digestions of Organic Samples section of our Reliable Measurements guide. The text goes into further detail on the digestion of organic matrices. Thank you for your question and best of luck.     Paul R. Gaines, Ph.D. Serving you in chemistry