Hi Ben:

If I may ask, how close to -24 per mil C and to 6 per mil N was your 
keratin measurement?  Where did you purchase your keratin? 

Thanks,
Lesley

Benjamin Harlow wrote:
> Hi Ruben,
>
> One good running standard I found was keratin, available from most chemical
> suppliers.  The C% and N% are very similar to insects or protein, so the
> amount needed is often the same as your sample.  It is also very homogenous.
>
> Our keratin calibrated to international reference material was about -24 per
> mil for carbon and +6 per mil for nitrogen.  I also use acetanilide which
> has C:N close to proteins and delta values around -30 per mil for C and 0
> per mil for 15N.  Not quite the range you are looking for but it may still
> bracket your samples.
>
> Cheers, Ben
>
>  
> Benjamin Harlow
> Washington State University 
> School of Biological Sciences
> P.O. Box 644236
> Pullman, WA  99164-4236
>  
> Office:  509-335-6161
> Lab:     509-335-6154
> Fax:     509-335-3184
>  
> Laboratory for Biotechnology and Bioanalysis Stable Isotope Core
> http://www.isotopes.wsu.edu
>  
>
> -----Original Message-----
> From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
> Of Ruben G. Chavez
> Sent: Thursday, July 06, 2006 11:48 PM
> To: [log in to unmask]
> Subject: [ISOGEOCHEM] Reference Material
>
> I will be analyzing insects for delta15N and delta13C in CF-IRMS.
> Please advise what reference material to be use for delta 13 C values 
> around -30 to -20 parts per thousand.  And for delta 15 N values of -4 to 
> +6 parts per thousand .
>
> Thanks
> Ruben
>
>   


-- 
Lesley Chesson
Analytical Chemist

Department of Biology
University of Utah
257 South 1400 East
Salt Lake City, UT 84112-0840

801-581-8917
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