Dear Giovanni,


I'm afraid I beg to differ with Bruno's suggestion.

Since you wish to calibrate your lab's CO2 cylinder you have will to
enlist the help of either a professional service or a friendly
colleague with a dual-inlet machine (unless you've got one yourself).

If you wish to report your results against PDB or V-PDB, your CO2
has to be calibrated directly against an international standard on a
dual-inlet machine and not via a secondary standard using two
different instruments.

Bruno is right in saying there can be an off-set. The difference in
d13C values for e.g. a given FAME between EA-IRMS and GC-
IRMS measurements using the same reference gas cylinder, is a
result of the external isotopic calibration technique in  GC-IRMS
when used in conjunction with a software that does not
compensate for the isotopic fraction of the CO2 peak from the on-
line combusted FAME ("time-shift correction").

There are ways around this problem but that's a different story.


Cheers,

Wolfram


> Dear Jovanni,
>
> your can buy a FAME, measure it with EA-IRMS (calibrated against NIST
> or IAEA certified standards) and then you can adjust you GCC-IRMS CO2
> (which will be different from the EA-IRMS value) by measuring the same
> FAME with GCC-IRMS Hope this helps
>
> Kind regards
>
> Bruno
>
> (Dr. Bruno Glaser)
> Institute of Soil Science and Soil Geography
> Bayreuth
> >
>  Hi all,
> >
> > It's the first time I need to calibrate the CO2 (delta13C) of our
> > GCC-IRMS apparatus: has anybody some suggestion on how to do that?
> >
> > Thank you,
> > Giovanni Calderone
> >
> >
> > **************************************************************
> > EC - Joint Research Centre
> > e-mail: [log in to unmask]