Hi, 

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
------------------------(;->