Frank Pawellek wrote:
>Subject: delta 13 C in cellulose
>Date: Friday, November 08, 1996 8:59AM
>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.
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,
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
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
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
Isotope Hydrology Section
Department of Research and Isotopes
International Atomic Energy Agency
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