Dear Listmembers,
I am attempting to get N isotope ratios of rock powders by CF. These samples are only 0.01 to 0.02 % nitrogen so I am preparing 30 mg samples for combustion. Would anyone have any account of successfully analysing of this sort of material by continuous-flow?
 
I have a couple of more specific questions: I wish to combust these rock samples at a higher temperature than the standard 1060 degrees - how hot can a quartz combustion tube go?
Should it be possible to pack a ceramic (alumina) tube as an oxidation column and then run at say 1300 degrees? This latter I have actually tried once, with the result that the tube split soon after getting up to heat. The tube was packed with chromium oxide; the tubing was degraded in the zone filled by the catalyst. Perhaps another grade of ceramic can withstand this treatment?
Any comments on rock stuff would be welcome.
Thanks,
Robert Van Hale
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