>Dear Listmembers,
>
>On a related note to Juske's post, is it necessary to freeze-dry samples before
>putting them into a plasma asher or can they go in as wet sediment in the case
>of lake core samples?
>
>Reed McEwan
>Univ of Minnesota
>Stable Isotope Lab


Dear Listmembers,

It is possible to put samples into a plasma asher wet but you won't be able
to get the pressure to pump low enough (0.1 - 1 mm Hg required) to strike
the Oxygen plasma discharge until they evaporate dry in the vacuum. This
may take a very long time since most ashers are not equiped with water
traps and have low conductance pumping systems.

Freeze drying is unnecessary since you are going to oxidise the organic
carbon out of the sample anyway.   Low temperature oven drying is adequate
before ashing  providing it does not cause other problems specific to your
samples.

Regards
Joe Cali


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Joseph A. Cali                    |                               |
Environmental Geochemistry Group  |                               |
Research School of Earth Sciences | Phone :  61-6-2493246         |
Australian National University    |   Fax :  61-6-2493246         |
Canberra, Australia,  0200        | Email :  [log in to unmask]  |
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