Early papers about using Cr as a reducing agent include

Rolle, W and Huebner, H, Fresenius Z. anal. Chem. 232, (1967) 328

Runge A, Isotopenpraxis 16 (1980) 2

There is also a Patent by

Gehre, M, Hoefling, R and Kowski, P., DE 44 37 120.9, Berlin (1994)

Together with other methods we have discussed the Cr technique in

Brand WA, Avak H, Seedorf R, Hofmann D, Conradi T,
New methods for fully automated isotope ratio determination from
hydrogen at the natural abundance level
Isot Environ Healt S 32: (2-3) 263-273 1996

Best regards    Willi
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Willi A. Brand, Stable Isotope Laboratory       [log in to unmask]
Max-Planck-Institute for Biogeochemistry
Carl-Zeiss-Promenade 10, 07745 Jena, Germany    Tel   +49-3641-643718
P.O.Box 100164, 07701 Jena, Germany             Fax:  +49-3641-643710
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