Christine,

The value of NBS21 graphite standard is - 28.10 o/oo vs PDB (1).

Delta C-13 values should now be reported vs VPDB (2).

(1)Kyser, Jurtis T. (editor)et al. May 1987, Short Course Handbook, Volume 13,
        Saskatoon, Saskatchewan (Canada). Stable isotope geochemistry of low
        temperature processes. Mineralogical Association of Canada.
        p.449.

(2) IAEA-TECDOC-825, pp. 31-34. T.B. Coplen, Reporting of stable carbon,
        hydrogen, and oxygen isotopic abundances.
        Vienna, Austria, 1995.

Good luck.

Glen Martin

Water Sciences Laboratory
University of Nebraska
Lincoln, Nebraska, USA 68583-0844

At 03:38 PM 1/25/99 +0100, you wrote:
>Dear listmembers
>
>I am looking for the d13C value of NBS21, a graphite standard now
>replaced by USGS-24 in recent compilations of standard references. I
>would be grateful to anyone who can provide me some data or
>bibliographic references.
>
>Christine FLEHOC
>BRGM - SMN/ANA/ISO
>3 Ave C. Guillemin
>B.P. 6009
>45060 ORLEANS cedex 2 FRANCE
>fax 33 02 38 64 37 11
>e-mail [log in to unmask]
>
>