I have an unopened, 50 gram, bottle of 99% normalized 18-O water.  I would
like to find a lab that has a need for a large volume of this highly refined
standard.  If anyone could point me in the right direction I'd appreciate
it.

Best Regards,

Clay

Clay Herzog
Herzog Design Engineering
109 E Chapline St.
Sharpsburg, MD 21782

301-432-5682 (home)
717-977-1043 (mobile)
[log in to unmask]

-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]]On Behalf
Of Rob Kreulen
Sent: Friday, January 19, 2007 3:08 AM
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] 18O CO2 Natural Gas

Jorge,

For d18O of CO2, both the oxidation and the reduction furnaces should be at
low temperature. We found that results are better when you by-pass both
furnaces using a piece of desactivated fused silica + press-fits. I suspect
that CuO in the furnaces acts as an active surface. Small concentrations of
CO2 are difficult to analyze, probably because they are very sensitive to
isotope exchange with water vapour or adsorbed water.

Talking about isotope exchange with water: a convenient way to calibrate
d18O is by equilibration of your natural gas mixure with water of known
d18O. This way you can calibrate on mixtures that are similar to the samples
that you will analyze.

Best regards,

Rob Kreulen
ISOLAB


-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
Of Jorge Teixeira da Silva
Sent: Thursday, January 18, 2007 8:09 PM
To: [log in to unmask]
Subject: 18O CO2 Natural Gas

Hi all,

We need to know the 18O from the CO2 of reference material NGS2 NIST Gas.
We need to set a procedure to measure the 18O from CO2 of natural gas
samples by GC/C IRMS (GCCIII & MAT252). We need to establish the 18O of our
CO2 LabTank reference gas under GC conditions for natural gas. I hope not
to face interferences under mass 46. I would be glad to hear your opinion.

Regards

Jorge Teixeira
PETROBRAS/CENPES/Organic Geochemistry Lab


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