Dear Isogeochemers,
I was wondering if I could obtain a survey of the relative merits of sampling
ground water for the del-13C of inorganic carbon with either of these two

methods:
1.  Collecting water poisoned by HgCl2 and then acidified by phosphoric acid in
the lab.
2.  Collecting water with BaCl2 or SrCl2 allowing BaCO3 or SrCO3 to form.
Filtering the precipitate and then acidifying with phosphoric acid in the lab.

Are there any publications that compare the accuracies of each approach?  
Any advice would be greatly appreciated.  Thanks, T.C. Onstott