Gesine:

The water trap in the MultiPrep device is very effective in removing
any water vapor generated during carbonate dissolution by phosphoric
acid, but it is important to make sure your acid is anhydrous to
start with.  We have analyzed nearly 25,000 carbonate samples with
our Micromass Optima-MultiPrep combination and the effectiveness of
the water trap is one reason we have had to bake out the source so
few times in the past six years.

I would be much more concerned with removal of organic matter from
your carbonate-poor samples using a method that oxidizes the organic
matter, such as soaking in dilute sodium hypochlorite, hydrogen
peroxide, etc.  Check the Isogeochem archives for extensive
discussions of favorite methods.  Alternatively, some workers roast
their samples at about 350°C, which would remove organic matter as
well as likely drive off any water, but I would favor a mild sodium
hypochlorite soak.

Hope this helps!

Steve


>Dear Listmembers,
>
>I would like to messure bulk samples with low carbonate content using an
>IRMS-Multiprep systhem.
>Does anyone have experience concerning the contain of cristalline water.
>
>Is the efficiency of the water trap between the Multiprep systhem and the
>IRMS sufficient enough or could it spoil the messurement??
>
>Would it be possible to release the cristalline water by previous heating
>about 400 degree celcius or could it influence the del 13C/18O values?
>
>Many thanks
>Gesine Preuss
>
>
>
>
>
>****************************************************************************
>*******
>Gesine Preuss
>Stable Isotope Laboratory
>Institute of Mineralogy and Geochemistry
>University Karlsruhe
>Kaiserstreet 12
>76128 Karlsruhe
>
>Germany
>
>Tel: ++49-(0)721-608-6520(Office), -6520 (Isotope Lab). Fax: -7247
>****************************************************************************
>*******

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