DIC 13C extraction methodolgies were studies by

Hassan, A. A., Methodologies for extraction of dissolved inorganic carbon
for stable carbon isotope studies:  Evaluation and Alternatives,  U.S.
Geological Survey Water-Resources Investigations 82-6, 51 p., 1982.

>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
>