Isotope Geochemists,

I am wondering how well CF-IRMS systems can handle running natural
abundance and enriched samples on the same system.  We run alot of natural
abundance N-15 samples on our Delta + EA system, and now want to run some
very enriched N-15 plant samples that are enriched in N-15 to the magnitude
of several wt %.

Is it enough to have quartz inserts in the combustion column to catch the
tin boats, and just change out the insert after running the labeled
samples, or do you have to change out other components such as the
oxidation and/or reduction columns in the EA after running labeled samples.
 Does it affect the IRMS source or other components, such as the flight
tube or collectors.  Do you have to have one system dedicated to enrich
samples and one system for natural abundance, or is it possible to run both
on the same instrument.  I have run enriched and natural abundance samples
in a MAT 251, and letting the system pump down over night or over a weekend
seems to be the trick.  But this is a static system, not a dynamic system
like the CF-IRMS.

Any comments would be appreciated, perhaps this has been discussed before
by this group?

Bill


----------------------------------------------------------
William J. Showers
Associate Professor
Dept. of Marine, Earth, & Atm Sciences
North Carolina State University

(919) 515-7143 - voice
(919) 515-7802 - fax
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"Never be afraid to try something new. Remember: Amateurs built the
ark.  Professionals built the Titanic."