Stable Isotope Geochemistry


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FRANK PAWELLEK <[log in to unmask]>
Fri, 8 Nov 1996 08:59:28 GMT0BST
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I am currently measuring delta 13 C in organic matter, mostly 
cellulose, some sediments. As an internal standard, I use IAEA 
pure cellulose standard, originally distributed for the standardization 
of radiocarbon dating labs. 

These labs measure the 13 C routinely as well, but 
usually with poor precision (they need the information as background 
for age determination, but 1/2 ppm difference in 13 C doesn't make 
much of a difference for the age anyway). So the methodology is often 
a bit "sloppy", producing large standard deviations.

I have a published list with delta 13 C values for the IAEA cellulose, 
measured by radiocarbon labs,  but it shows a wide spread of values
- as I expected. In contrast, my own measurements all produce very 
nearly the same d 13 C - the material is in fact very homogeneous.

My question: Has any stable isotope lab measured the material for 
13 C specifically, so that I can compare my results with theirs? If 
not, would anybody be willing to do some measurements for establishing 
a more exact d 13 C value? I could provide the standard.

And: Is there another suitable standard material for organic carbon, 
preferably in the form of cellulose? I think some people use some 
organic acid (or so) for that purpose, but I'd prefer something that is 
processed exactly as my samples.

Frank Pawellek

Frank Pawellek
Stable Isotope Laboratory
Department of Geography
University of Wales, Swansea
Singleton Park
Swansea SA2 8PP
Wales / GB

Tel. +44 1792 295148
Fax. +44 1792 205556