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Hi Sarah,

I’d advise against this. We’ve analyzed a lot of rocks that are much less than 0.1% C—with considerably less material. I suggest measuring the C isotopes first on a much smaller sample. Start with 20 mg and run with zero dilution.

Typically, we would like to have 10 micrograms of N, but we’ve found 5 microgram of N gives good reproducible results. I would suggest, after measuring C on a much smaller amount, analyze 25 then 50 mg samples first. Calculate how much you’ll need for 5 or 10 micrograms. We’ve analyzed 100 mg samples with a blank in between. Use a fresh insert. You might be able to run 10 or so at this level.

Run blanks of your tin boats, of course.

Marilyn Fogel


Check out my new blog at https://isotopequeen.blogspot.com/

Dr. Marilyn L. Fogel, 
Distinguished Professor and Wilbur W. Mayhew Professor of Geo-Ecology
Director of the Environmental Dynamics and Geo-Ecology Institute (http://edge.ucr.edu/)
Dept. of Earth and Planetary Sciences
University of California Riverside
900 University Ave.
Riverside, CA 92521
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Phone: 209-205-6743


From: Stable Isotope Geochemistry <[log in to unmask]> on behalf of Sarah Grosshuesch <[log in to unmask]>
Reply-To: Stable Isotope Geochemistry <[log in to unmask]>
Date: Monday, September 9, 2019 at 11:28 AM
To: <[log in to unmask]>
Subject: [ISOGEOCHEM] 300mg sediment EA-IRMS

Anybody ever run a 300mg sed sample w/ very low (<0.5%) carbon and nitrogen by EA-IRMS ?
I am wondering if a Costech 4010 ECS semi-micro loop for oxygen will be adequate for 
combustion.

Thanks -  Sarah
--
Sarah Grosshuesch
Researcher | Large Lakes Observatory | [log in to unmask]

2205 E. 5th St., Duluth, MN 55812
University of Minnesota Duluth
[log in to unmask] | 218-726-7206