Robert,

Why don't you just define a method that uses the
left volume as standard (with NBS19) and the right volume as sample (with
WS) ? If you enter NBS19 in the standard editor, the delta of the working
standard will be reported vs. PDB directly without any need to
calculate.

Regards-

Manfred

*Manfred Jaklitsch**International Atomic Energy Agency*
*Department of Nuclear Sciences and Applications* *Isotope
Hydrology Laboratory* *P.O. Box 100* *A-1400 Vienna,
Austria*

( *Tel.:
+43 1 2600 21768*

6 *Fax: +43
1 26007 21768*

-----Original Message-----

From: Stable Isotope
Geochemistry [mailto:[log in to unmask]] On
Behalf Of [log in to unmask]

Sent: Friday, 09 July 2010 08:38

To:
[log in to unmask]

Subject: Calculating the delta of the working
gas

Greetings,

I assume this is an easy question but it seems my last
math class was a long time ago.

Usually I don't care about the exact value of
my CO2 ref gas on our gasbench system since everything is normalizied to
reference materials with known values (and working gas cancels out). I just type
in a value for the working gas in the isodat standard editor which will give a
delta value close to the correct value.

I need to calculate the CO2 value
of the working gas now and my idea was just to caluclate the things backwards.
Assuming that my reference material (e.g. NBS19) will produce a CO2 with a known
value it should be possible the calculate the delta value of the working gas
etiher from the raw delta values or the ratios given in Isodat by treating the
ref gas as the sample and the NBS 19 as the standard gas. However, sitting in
front of Isodat and the equations it is not so obvious anymore...can anyone
point me in the right direction?

regards,

Robert

--

Dr.
Robert van Geldern

GeoZentrum Nordbayern / Applied Geosciences University of
Erlangen-Nuremberg Schlossgarten 5

91054 Erlangen, Germany

mailto:[log in to unmask]

www.gzn.uni-erlangen.de

fon:
+49(0)9131-85-24780 (office)

fax: +49(0)9131-85-29294

Room: O 0.106
(office)

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