Dear Listmembers,

We recently experienced a problem when carbonates analyses are run on 
our Multiprep-Optima :
the 46/44 ratio traces are v-shaped instead of flat,
the 18O precision is bad (around 0.020 instead of lower than 0.008),
and  delta18O values of NBS19 can differ from 1 per mil in the same batch.

I've checked all the valves of the Dual-Inlet and the Multiprep for air 
leaks and cross seat leakage, all the valves are OK.
When I run stabilities and linearities (with the same CO2 gaz in all the 
DI), traces are flat and values are close to zero, so the DI seems to be OK.
I've checked the water trap and the 2 cold fingers for finding 
contamination, and there is none.
The bath is equilibrated at 90°C, the needle is brand new.
I've tested 2 different acids, and the result is always the same.

Have you ever encountered this kind of problem, and found an explanation 
? because I'm running out of ideas now...

Regards,

Karine

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Karine CHARLIER
Environnements et Paleoenvironnements OCeaniques
UMR CNRS 5805 EPOC
Universite Bordeaux I
Avenue des Facultes
33405 TALENCE Cedex
FRANCE

Tel : 0 (33) 5 40 00 83 62
Fax : 0 (33) 5 56 84 08 48
E-mail : [log in to unmask]
Web : http://www.epoc.u-bordeaux.fr/

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