Hi Weifu,
I remember there were many discussions on this issue on this forum a while
ago. Our lab uses Silver Phosphate (ortho) (Ag3PO4) to fix this problem
(purchased from Alfa Aesar, Stk# 11415, Lot# H23F15, CAS# 7784-09-0). We
freeze the annoying CO2 into Ag3PO4 after finishing water separation, then
warm the Ag3PO4 up to release the CO2 and transfer this purified CO2 to
collection vessel for MS analysis.

Zheng-Hua



>===== Original Message From Stable Isotope Geochemistry
<[log in to unmask]> =====
>Hi, Everyone
>
> We are currently working on some carbonate samples containing a
relatively high S content. Thus the CO2 we extracted through phosporic acid
digestion ends up with a very annoying S contamination, which was confirmed by
the mass scan of the sample. At this moment, the exact nature of the
contaminant hasn't been identified, presumably H2S or SO2. We have already
tried several purification methods, including cryogenic separation, reacting
with silver wire, GC separation etc. So far, the results are not satisfactory.
 I wonder whether anyone can give me some more hints on this problem. (The
sample size we are dealing with is usually around 60 micromoles.)
>
> Any suggestions and comments from you will be highly appreciated.
>
>Regards
>Weifu