Dear Anita,

Another option is to take a lab chemical and add the calculated amount of d15N labelled chemical to adjust the d15N value to whatever value is desired. We made a large batch of histidine dissolved in water and added enough d15N labelled histidine to make a standard with the value of 25. It is necessary to completely evaporate the solution to dryness and completely grind it all together to make a very fine powder. Be sure to do multiple measurements to determine both the actual d15N value and insure that the standard is homogeneous before you use it.


On Sep 16, 2013, at 4:23 AM, Anita Aerts-Bijma wrote:

> Dear colleagues,
> in order to preserve the IAEA standards N1 and N2 we like to have  labstandards with  delta 15 values of 0  and around 20 . The zero value doesn't appear to be a problem, but a material with the higher value we can't find until now.
> Does anyone of you find a readily available material with a d15N of approx 20?
> Thanks,
> -- 
> Anita Aerts-Bijma 
> Centre for Isotope Research, University of Groningen. 
> Centrum voor IsotopenOnderzoek (CIO), Rijksuniversiteit Groningen 
> Nijenborgh 4, 9747 AG Groningen, Netherlands 
> tel +31-50-3634716 fax +31-50-3634738 

Douglas G. Burrows
National Marine Fisheries Service
Northwest Fisheries Science Center
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