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Fri, 11 Jul 1997 08:19:01 EST |
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I could not agree more, Reed has a point there. We use in our
laboratory vacuum roasting but wonder what happen with carbonates
who decompose at relatively low temperatures. I propose that a
group of laboratories get together and analyze a common sample using
each one its own method. The 2nd Int. Symp. in Applied Isotope
Geochem. at Lake Louis could be a good opportunity to discuss the
results.
My best regards to all,
Adriano Parisi
Earth Sciences Depart.
INTEVEP S.A.
__________________________ Separador de respuesta ______________________________
Asunto: removal of organic material
Autor: Reed McEwan <[log in to unmask]> en internet
Fecha: 10/7/97 16:28
There appears to be some difference of opinion in the stable isotope community
regarding the preferred method for removal of organic material from carbonates
(calcite in bulk sediment, ostracodes, forams, etc) prior to extraction/analysis
for O and C isotopes. Soaking in bleach or hydrogen peroxide solutions are time
consuming and appear to introduce small shifts in the isotopic composition of
the carbonate. Vacuum roasting, while more time efficient, also introduces
errors from what I have heard and read. Plasma ashers appear efficient, but I
do not know what, if any, changes they effect.
I searched the ISOGEOCHEM archive and found that this issue was raised about a
year ago. Only one response to the initial question was tendered. At the risk
of being redundant I would like to open the topic for discussion again.
We have dealt with H2O2 and bleach solutions and are currently looking at
alternatives to these methods. With this is mind, what are the
advantages/disadvantages of using a plasma asher versus vacuum roasting for the
removal of organic material? Are there any references addressing the issue?
Reed McEwan
Stable Isotope Lab
Univeristy of Minnesota
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