Tom and interested colleagues--

Although this posting is premature, Tom Guilderson's query concerning the
status of CO2 isotopic reference materials to replace NBS16 and NBS17 has
probably raised the conscienceness of the community.  I responded directly
to him earlier but now think that I should share my response.
>
>There are three CO2 reference materials that are being prepared by the
Atmospheric Chemistry Group at NIST: RM 8562 (Heavy), RM 8563 (Light) and RM
8564 (Biogenic) in the method described in my report published in
IAEA-TECDOC-825.  The first two will be similar to NBS17 and NBS16, and the
third will have a d13 value of about -10 permil (vs. VPDB), d18 near +30
permil (vs. VSMOW) and modern levels of C14.  The Standard Reference
Materials Program Office database will not have a record of this until all
three batches are transferred to them, which will occur later this year
(about September).  The gases are in 25 cm x 9 mm diameter borosilicate
tubular breakseals and so will require a 9 mm or 3/8" tubecracker.  These
RMs will probably be featured in a future intercomparison through the IAEA,
but we plan to initially provide the d13 and d18 values and uncertainties
based on our measurements using strict protocols.
>
As always, I invite feedback concerning the needs of critical programs
within the isotope measurement community for standards.

Mike
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Dr. R. Michael Verkouteren
Atmospheric Chemistry Group
B364, Chemistry Building (222)
National Institute of Standards & Technology
Gaithersburg, Maryland   20899   USA
301-975-3933 (telephone)                                      
301-216-1134 (facsimile)                                       
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