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
Robert Van Hale