Thank you Wolfgang.  This information will be helpful.




From: Stable Isotope Geochemistry <[log in to unmask]> On Behalf Of Wolfgang Wanek
Sent: Wednesday, December 12, 2018 1:03 AM
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] 15N of microbial biomass sample extractions


Dear Brett,

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.

Kind regards,


On 12/11/2018 11:26 PM, Hill, Brett (AAFC/AAC) wrote:

Hello all,


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?







Brett Hill

Stable Isotope Lab

Agriculture and Agrifood Canada

Lethbridge Research and Development Centre

5403 1st Av. S.

Lethbridge, AB.

T1J 4B1




Assoc. Prof. Dr. Wolfgang Wanek
Division of Terrestrial Ecosystem Research
Department of Microbiology and Ecosystem Science
Research Network "Chemistry Meets Microbiology"
University of Vienna
A-1090 Vienna, Althanstrasse 14
Phone: +43 1 4277 76662
Fax: +43 1 4277 9542
Email: [log in to unmask]