John:
In a typical oxidation-reduction furnace tube arrangement for NC analyses
using a CE NA 1500, it's been my experience that sulfur, in addition to
halogens, rapidly degrades the efficiency of the silvered
cobaltous-cobaltic oxide in the oxidiation tube, significantly reducing the
number of samples that can be run before having to change the chemicals.
I would suggest you chemically or mechanically remove the sulfides from
your material. Although pyrite and other iron sulfides are likely to be
the dominant sulfides present, other base-metal sulfides such as sphalerite
(zinc sulfide), galena (lead sulfide), etc., are likely to be present too.
You will have to tailor any separation method to the particular sulfides in
your material. One useful reference is the following:
Chao, T. T., and Sanzolone, R. F., 1977, Chemical dissolution of sulfide
minerals: Journal of Research of the U.S. Geological Survey, v. 5, no. 4,
p. 409-412.
Hope this helps.
Steve
>We're planning to carry out 15N analyses by conventional CF-IRMS
>(Carlo Erba and MAT252) of gold and uranium mine tailings. The
>material ranges from fresh slimes to old oxidised tailings. We are
>concerned about the high levels of sulphur, iron, lead and other
>metals that are present, particularly in the form of pyrite, and what
>effect this will have on the combustion/reduction chemicals and
>isotope measurements.
>
>Any advice would be most welcome.
>
>Thanks
>John
>
>
>
>
>******************
>John Lanham - Stable Light Isotope Laboratory
>Archaeology, University of Cape Town, South Africa
>Tel: +27 21 650 3847
>Fax: +27 21 650 2352
>http://www.uct.ac.za/depts/age/aru/isotope/
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