Jay:

NIST 1547, peach leaves, has a C/N ratio of about 16, and a delta 13C
of about -26 per mil and delta 15N of about 2.2 per mil.  This
material is still being evaluated by several labs as part of a ring
test conducted by the University of Waterloo, but I already use it as
an in-house standard for d13C measurements during CF-IRMS analyses.
Although I generally discourage people using reference standards from
NIST as in-house standards, the 50 gram aliquot that cost me $235.00
in May 1999 is enough to last at least 500,000 analyses, which, if
you ran the standard 5 times a day every day of the year, would take
you 273 years to exhaust it!

Steve


>Dear All;
>     We measure 15N and 13C on particulate samples using a standard Finnigan
>Mat delta +/ Carlo Erba EA system. As a standard practice we intersperse our
>samples with a laboratory standard (as well as the occasional outside
>calibrated std to keep things honest), in our case powdered chitin.  So far
>this has worked well but we would like to have available another solid,
>powdered organic material with a higher C/N (chitin is about 8).  Ideally we
>are looking for something with a C/N of about 12-15.  Does anyone have any
>suggestions? The material should be available as a non-hygroscopic, fine
>powder of uniform isotopic value. Any suggestions?
>Thanks;
>--
>Dr. Jay A. Brandes
>Assistant Professor
>Marine Sciences Institute
>The University of Texas at Austin
>750 Channel View Drive
>Port Aransas, TX 78373
>(361) 749 6756 (office)
>(361) 749 6777 (fax)
>(361) 442 3217 (Cellular)

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Stephen S. Howe                         Office:  (518) 442-5053
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