Dear all,
        I need to analyze 15N enriched samples from a N-uptake experiment
(phytoplankton on GF/C filters) with a VG SIRA II mass spec. The samples
were incubated with 99% 15-N in form of NH4Cl and KNO3. Tracer addition was
about 10% of ambient dissolved N concentration (i.e, 0.3ug/L 15NO3-N and
3ug/L 15NH4-N).
As I have no experience with analyzing enriched samples and my SIRA manual
is essentially useless in this regard, I would appreciate warnings/hints
from SIRA (or similar intrument) users. In particular, is there anything I
need to modify in the N2 parameter file or tuning of the instrument? I
assume (or hope...) that the instrument should be able to handle such
samples without hardware modifications.
In order to avoid memory problems with our EA-CF setup the samples will be
combusted in Vycor tubes following the procedure of Kendall and Grim (1990)
and cracked on the manifold.

Thanks for your help!

Cheers,
Andrea


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|    Dr. Andrea Lini           |  Stable Isotope Laboratory     |
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