please have a look in
Qi HP, *Coplen TB*, Geilmann H, et al. Two new organic reference
materials for delta C-13 and delta N-15 measurements and a new value for
the delta C-13 of NBS 22 oil
<http://wos.consortium.ch/CIW.cgi?885394_E9D4B075_885394-0&Func=Abstract&doc=1/1>
RAPID COMMUN MASS SP 17 (22): 2483-2487 2003
Best regards
Roland
Bernie Genna wrote:
> Hello,
>
> I trying to obtain a heavy N15 isotopic standard (>20 per mil)
> to use as
> an upper end calibration standard when analyzing N15 on our EA. We
> used to
> use RM8548 ammonium sulfate (20.3 per mil), but it is no longer being
> produced at NIST. Does anyone know of any other isotopic standard that
> has
> heavy N15? Would anyone be willing to give up some RM8548 so that we can
> calibrate an internal lab standard? We have a silver nitrate that runs
> about 16 per mil, but it is not calibrated.
>
> Thanks,
>
> Bernie Genna