Hi All,

I've been running mass specs for over 7 years now, and I have to admit 
(somewhat embarrassingly) that I still cannot explain to students what 
exactly causes carry-over inside my EA-IRMS system when running 
15N-enriched samples.  If the samples are 100% combusted, how can there be 
any 15N leftover from the previous sample?  I know that, after running 
enriched samples, when I replace the reactors with fresh ones and start 
analyzing natural abundance samples again, all is ok.  So I'm guessing that 
the carry-over problem has to do with either the oxidation or reduction 
reactor.

Any insight on this would be very much appreciated.

Cheers,
Rick

Richard (Rick) Doucett, Ph.D., Associate Director
Colorado Plateau Analytical Laboratory
Northern Arizona University
Tel: 928.523.0967 (lab)
Tel: 928.523.7265 (office)
Fax: 928.523.7500

Stable Isotope Lab Website: http://www.isotope.nau.edu

Mailing address for packages:
Dept. Biological Sciences
Northern Arizona University
Building 21, South Beaver Street
Flagstaff, AZ, 86011-5640