Dear All,

Thanks to those who sent me their ideas about the carbonate analyses 
problem we have. Some points:
1) The carbonates were pure calcites, the organic contamination of the 
samples is not likely, as calcite carbonatites showed the effect first, 
now the drift is worse.
2) There was no problem with pure CO2 (30 Labco vessels were filled with 
He-CO2 mixture normally used for H2O-CO2 analysis), no drift appeared. 
So the tank CO2 problem that Willi suggested is not likely (but we have 
to investigate this further).

I suspect the GC and the Nafion trap to be saturated during the 
analyses. Maybe the reaction T of 72 oC results in too much H2O 
evaporation that saturates the system. I’ll try a room T reaction set (5 
hours reaction).

Another thing is the organic contamination idea. If not the samples, it 
may come from the exetainers. These are made of pyrex, so I’ll heat them 
to about 400 oC then do an analysis set again.

Thanks for the responses. This is quite tricky…

Anyway, the system is fine, I just analysed successfully dD of fluid 
inclusion water in calcite crystals of 0.2 g!

Cheers,

Attila

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Dr. Attila Demeny
Geokemiai Kutatointezet - Institute for Geochemical Research
Magyar Tudomanyos Akademia - Hungarian Academy for Sciences
Budapest, Budaorsi ut 45, H-1112, Hungary
Tel: (361-)309-2600/ ext. 1223 (office), 1394 (lab)
Tel/fax: (361-)319-3137
e-mail: [log in to unmask]
Http://www.geochem.hu/
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