See Watanabe and Narukawa, 2000, Analyst, 125:1189-1191.
It uses a ton of acid, but no fusion:
0.25 g or less graphite, 5 mL each nitric and sulfuric acids heated for 20 min at 60% microwave power, followed by a period of standing (for 1 min) and the addition of 4 ml of nitric acid. The sample was re-heated for 10 min at 65% power, then left for 1 min, after which 4 ml of nitric acid were added. Five more cycles were carried out with 10 min heating at 65% power, 1 min standing and the addition of 4 ml of nitric acid.

R. Steven Pappas, Ph.D.
Team Lead, Tobacco Inorganics Group
Centers for Disease Control & Prevention
4770 Buford Highway, NE
M.S. F44, Building 110
Atlanta, GA 30341-3717, USA

-----Original Message-----
From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's). <[log in to unmask]> On Behalf Of Tomáš Magna
Sent: Friday, June 1, 2018 5:46 AM
To: [log in to unmask]
Subject: Graphitic material dissolution

Hi folks,

I have been approached recently by a colleague who would be interested in trace element concentrations in graphite-rich rocks, sometimes up to 15-20% graphite. I guess classical HNO3-HF-HCl decomposition may not work properly and due to instrumental issues, I want to avoid alkali fusion, although I am not sure if this would help either. Is there a way to dissolve the bulk material as is, or would it be easier to isolate graphite from the matrix and decompose the fractions separately? For silicate, the above HNO3-HF-HCl will likely work fine but can one convert graphite into solution in a non-complicated way?

Thanks for advice.

Best regards,
Tomas

--
___________________________________________
  
Dr.sc.nat. Tomáš Magna
  
Associate Editor - Chemie der Erde
Czech Geological Survey
Klárov 3
CZ-11821 Prague 1
Czech Republic
Tel.: +420-2-5108 5331
Fax: +420-2-5181 8748
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