Herb,
the thin reference transfer capillary between the open split and the 
mass spec is rather sensitive to temperature fluctuations. This is due 
to the small size and the fact that the flux through the capillary is 
governed by Hagen-Poisseuille's law which states that the (laminar) flow 
through such a capillary is directly proportional to the pressure 
difference and inversely related to the 4th power (!) of the radius (a 
change in radius by a factor of 2 increases the flux by a factor of 16). 
Hence, small diameter changes due to air draft can affect the intensity. 
We maintain our ConFlo lid closed and lead the capillary through a 1/16" 
guide hose (made from Peek to have the capillary glide through easily). 
This should reduce fluctuations on the peak top. However, as you 
correctly mention, this is only a cosmetic issue, isotope ratio results 
should not be affected at all.
Regrads   Willi

Herbert Tobias wrote:
> Hello all,
>
> I would like to ask a question about reference CO2 gas pulse shapes using
> the Conflo III device on a MAT 253.  Has anyone seen the following issue
> and "solved" it:
>
> The problem I have is that the gas pulses when equilibrated is a bit
> noisy.  So when you see the CO2 gas pulses generated, they look a bit
> jumpy. In other words, they are not smooth on the top.  It isn't an issue
> as far as reproducibility, they still give good zero enrichment numbers. 
> I guess this is more of an "aesthetic" issue.
>
>  I tried changing head pressures of the He gas and CO2 gas, plus distances
> of the capillaries in the "open split" tube to no avail.  Any hard
> experience with this issue will be greatly appreciated.
>
> sincerely your disgruntled,
> -Herb
> Cornell University
>
>
>   

-- 
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Willi A. Brand, Stable Isotope Laboratory      [log in to unmask]
Max-Planck-Institute for Biogeochemistry (Beutenberg Campus)
Hans-Knoell-Str. 10, 07745 Jena, Germany      Tel: +49-3641-576400
P.O.Box 100164,      07701 Jena, Germany      Fax: +49-3641-577400
http://www.bgc-jena.mpg.de/
http://www.bgc-jena.mpg.de/service/iso_gas_lab/
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