I have some information on our setup on our lab webpage. It needs to be 
updated and I had wanted to transfer some of it to the isogeochem wiki page 
if time would allow it. It does hopefully give some useful information. I 
had the same problem as Reinhard with the melting septa and switched to the 
thermogreen ones from Supelco (rated up to 350C).

A couple of other points for anyone who looks at the page:

We now use an SGE 0.5uL syringe with a wide diameter (23 gauge I think) and 
conical tip and find that this syringe works better than the Hamilton one. 
In addition it is less expensive and has a syringe needle/plunger 
replacement kit that can be purchased for about $28. Only catch is that you 
need to replace septa a little more frequently due to the larger diameter 
needle.

All of the information I listed about memory effects were observed with the 
Hamilton syringe and may no longer be applicable with the SGE one. I just 
need time to reinvestigate this...

We now use a postinjection delay of 15 seconds instead of the 8 seconds 
mentioned in the page.

Our glassy carbon tube does not have a narrow diameter hole on top so we 
cut a piece of graphite tubing that did have a narrow diameter hole and 
just set it on top of the glassy carbon tube.

We wrap the bottom fitting with about two layers of teflon tape to get the 
seal (just need to feel that it is snug in the glassy carbon tube).

We now have a 7mm id glassy carbon tube and the peak shapes are a little 
more narrow. I need to throw a screen shot of a data file up there eventually.


Here's the link:

http://kfleb.asu.edu/Analytical/gIRMS/Instrumentandanalysis/Analytical/Methods/WatersbyTC-EA.html


As always, if anyone sees something crazy in the webpage please let me know.

Prosit.

Anthony



At 01:57 PM 12/1/2006, you wrote:
>Dear all,
>
>setting up our reverse-flow TC/EA water setup we were also suffering from 
>different kinds of bad peak shapes. Playing around lead us to the 
>following, apparently working setup:
>injector heated to 80°C (120°C destroyed septum)
>injection speed 100µl/sec, injection volume 1µl, no post injection delay, 
>open glassy carbon tube, normal spacing , He flow 100ml/min
>This setup works fine for H/D while we have not yet checked oxygen.
>
>Best regards
>
>Reinhard Langel
>Forest Ecosystems Research Center
>Competence Center Stable Isotopes
>Büsgenweg 2
>D-37077 Göttingen
>Fon: 049 551/398104
>Fax: 049 551/398110
>http://wwwuser.gwdg.de/~fzw/kosi/Index.htm

------------------------------------------------------
Anthony L. Michaud
W. M. Keck Foundation Laboratory for Environmental Biogeochemistry
School of Earth and Space Exploration
Arizona State University
Tempe, AZ 85287-1404

Web: <http://kfleb.asu.edu>http://kfleb.asu.edu
Tel: 480-727-8033
Fax: 480-965-8102

Mailing address:
Anthony Michaud
PSF-686
Arizona State University
Tempe, AZ 85287-1404

***Windsurf Everywhere***
------------------------------------------------------