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Frank Pawellek wrote:

>Subject: delta 13 C in cellulose
>Date: Friday, November 08, 1996 8:59AM

>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

Dear Frank,
you are right, IAEA provides the cellulose material IAEA-C3 as 
intercomparison material for radiocarbon dating. This cellulose was 
originally produced in 1989 from one years' harvest of about 40 year old 
trees, which were chopped and bleached to cellulose. A paper factory in the 
Netherlands supplied sheets of this material. The bulk of material is kept 
in the Groningen Centre for Isotope Research, whereas IAEA distributes this 
material for radiocarbon labs.
Delta 13 C data for IAEA-C3 have been published in Radiocarbon (Rozanski et 
al (1992): The IAEA 14C intercomparison exercise 1990. Radiocarbon 34(3), 
506-519) and initially in an IAEA internal report (K. Rozanski: Consultants' 
Group Meeting on C-14 reference materials for radiocarbon laboratories, 
IAEA, 18-20 February 1991. Report to the Director General, IAEA, Vienna, 
54pp).
Buhay et al. have published some preliminary data on delta 18 O of this 
material in the IAEA-TECDOC-825 "Reference and intercomparison materials for 
stable isotopes of light elements" (Proceedings of a consultants meeting 
held in Vienna, 1-3 Dec. 1993), IAEA, Vienna 1995, ISSN 1011-4289. Both 
report and TECDOC are still available from IAEA, please contact me for 
requests.

I would encourage further studies of the isotopic homogeneity of this 
cellulose. However, in order to ensure greatest benefit for the 13 C 
community, such a study should not be limited to a single batch of 50 g of 
this material which you obtained from IAEA. Those results could not be 
regarded as representative for the remaining stock of this material. 
Therefore investigating homogeneity of only this batch would be a waste of 
time and efforts for the involved labs and will not help to establish a 
cellulose reference material which should be easily available for all 
interested scientists.

Instead IAEA could homogenize a sufficiant amount of this material  and 
provide it in amounts most suitable for delta 13 C analysis. In first 
instance, few experienced labs should perform homogeneity tests on randomly 
chosen portions of this cellulose in order to establish best values for 
isotopic composition of carbon and oxygen. If tested and proven to be 
isotopically homogenious, this cellulose could serve in future as an 
additional organic reference material for 13 C.

As you may know, some other organic reference materials for 13 C are already 
available from IAEA and NIST:
IAEA-CH-6 (Sucr.Anu), sucrose
IAEA-CH-7 (PEF1), polyethylene foil
NBS22, oil
USGS24, graphite

Manfred Groening

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Manfred Groening
Isotope Hydrology Section
Department of Research and Isotopes
International Atomic Energy Agency
P.O.Box 100
A-1400 Vienna
Phone: ++43-1-206021740
Fax: ++43-1-20607
e-mail: [log in to unmask]
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