Dear Paul,
What is your d2H of reference gas in a tank?

I had similar problem in Texas with a tank delivered by BOC with 
extremely low d2H. Something  close to -800 permil, if I remember 
correctly. The slope was <0.7 on Delta Xp Plus. I did a few tests runing 
SMOW/GISP/SLAP and results were quite consistent. However, finally I 
decided to change hydrogen tank. New tank had about -150 and slope was 
as expected around 0.95.



Greg

-------------------------------------------------------------
Dr Grzegorz Skrzypek, Research Assistant Professor

West Australian Biogeochemistry Centre
John de Laeter Centre of Mass Spectrometry
School of Plant Biology, The University of Western Australia
35 Stirling Highway (MO90), Crawley WA 6009, Australia

Phone +61 8 6488 4584, Fax +61 8 64887925
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Paul Eby wrote:
> Listmembers,
>
> Has anyone ever seen a calibration slope (known and measured values of 
> two standards) deviate significantly from the expected 0.95 to 1.05? 
> We are consistently seeing 0.67.
>
> This is a new Delta Advantage. d13C and d18O on a pair of OzTech CO2 
> standards by dual inlet both have a slope of approximately 1, so the 
> instrument is otherwise working fine (similar results by GasBench).
>
> Hydrogen is a different story: a pair of OzTech standards by dual 
> inlet has a consistent slope of 0.67, and SMOW/GISP/SLAP by H/Device 
> shows similar results. H3 is consistently around 0.6, and the 
> calibration performed on the H/Device seems stable enough that I could 
> probably ignore the issue and run.
>
> Any suggestions out there on how this could be?
>
> Paul Eby
>
>
> [log in to unmask]
> Alberta Research Council
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>
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