Thank you Wolfgang. This information will be helpful.
CFE coupled to K2SO4 extraction (best at lower concentrations such as 50 mM) and EA-IRMS is a standard protocol though not very sensitive.
If you want to become more sensitive and get rid of the salt load, and if you have access to a purge-and-trap IRMS (e.g. Gasbench II with liquid N2 trap coupled to IRMS)
you can alternatively use alkaline persulfate oxidation of the extracts to nitrate and then convert nitrate to N2O chemically (see attached paper) or using the denitrifier method.
On 12/11/2018 11:26 PM, Hill, Brett (AAFC/AAC) wrote:
I have recently been sent dried K2SO4 salts from soil microbial biomass sample extractions. I am getting too little response for nitrogen in particular to get robust results. It will be a while before I am able to communicate with the preparer of these samples to determine the particulars of their method. In the meantime, I would like to be more educated on what may have worked for others in terms of extraction ratios, salt weights, etc. Does anyone have experience with CFE that can give pointers or cautions that might help increase the amount of nitrogen in the samples?
Stable Isotope Lab
Agriculture and Agrifood Canada
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Assoc. Prof. Dr. Wolfgang Wanek
Division of Terrestrial Ecosystem Research
Department of Microbiology and Ecosystem Science
Research Network "Chemistry Meets Microbiology"
University of Vienna
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