Hi Weihong,
barium carbonate can be analyzed for 13C using a CirmMS system. We have
checked the combustion method against the phosphoric acid method some
years ago (Böttcher & Dietzel; abstracts: GASIR and Beih. Eur.J. Mineral)
and it works. By means of C-irmMS you are just loosing the 18O signal.
Regards, Michael
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Michael Böttcher
IOW, D-18119 Rostock, FRG