Dear Anita,

Another option is to take an amino acid and add the calculated amount of d15N labelled version of the same amino acid 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.

Doug

On Sep 17, 2013, at 7:44 AM, Anita Aerts-Bijma wrote:

> Thank you all for your suggestions, both on the list as directly to me. It is a good idea to calibrate our organic working standard (labstandard) against organic reference standards like USGS 40 and USGS 41, instead of the inorganic ones from the IAEA (N1 and N2).
> So the easiest thing to try is to buy phenylalanine in a large quantity and to order the USGS 40 and 41.
> I couldn't find the natural range in nitrogen 15 of all the amino acids. If someone knows if there is a better choice then phenylalanine, please let me know.
> Thanks again, it was very helpful,
> -- 
> 
> 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 
> http://www.rug.nl/cio

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Douglas G. Burrows
NOAA
National Marine Fisheries Service
Northwest Fisheries Science Center
2725 Montlake Blvd. E.
Seattle, WA, USA 98112
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Telephone: (206) 860-6790
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