Although we are running with a different brand of equipment, we reliably detect N down to 40ug all the time. The only reason that our C target is 10x higher is that we typically run with a helium dilution. If you only need 13C, can you use a method such as without a dilution or different open split position? We run C without dilution if we need to analyze something precious or limited like and ancient sample or NBS19 via EA.
From: Stable Isotope Geochemistry <[log in to unmask]>
On Behalf Of Matthew Von Tersch
Sent: Tuesday, July 31, 2018 4:04 AM
To: [log in to unmask]
Subject: [ISOGEOCHEM] Low %C soil bulk isotope analysis - how much is too much?
We have been asked to run some soil samples taken from a salt marsh in Australia, the majority of which are from the surface, but there are also some from a core. The samples have been dried and ground and analysed for TOC.
Based on a requirement of 400 ug carbon per sample for our system (Sercon 20-22), some of the samples will require between 5 and 15 mg of soil per capsule. I spend the majority of my time working with collagen in the 1 mg range, so this venturing into the unknown.
For those of you working with soils, is there anything I need to be aware of when running this type of material for delta 13C, and how much material per capsule is too much?
Many thanks for any assistance.
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