Hi Susan,
Have you tried replacing the rubber o-ring just under the valve. These rings
are fairly cheap and I have found in the past that they tend to be the
weakest link in the valve system. 

Brian Jones
Stable Isotope Ecology Lab
Texas A&M University
College Station, Tx. 77843-3146
979-845-8916
 
-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
Of Susan Ziegler
Sent: Wednesday, May 10, 2006 11:26 AM
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] GC-C-IRMS issues (split/splitless valve leak)

Thanks to everyone for their suggestions on our fractionation issue.
It was much appreciated.

It turns out that I have a leaking split/splitless on/off valve in
the injector system. I have removed the valve in question and purged
it with compressed air, taken it apart and cleaned it.  After that
the leak was diminished but subsequently returned within 6 hours. In
the past toggling the valve between split and splitless would fix the
leak found in splitless mode and to prevent such leaking toggling
every few days did the trick.  So this valve leaves much to be desired!

I am using an HP6890 (about 6 years old) and have just found out that
I cannot purchase a new s/sl onoff valve through Agilent Technologies
(the company that now makes the HP instruments) and instead have to
purchase an entire manifold that the valve is mounted onto at a cost
of $2300 USD.  Does anyone know where I might be able to find a new s/
sl on/off valve (PN G1544-60710) for the 6890 split/splitless
injector?  This is apparently an inherent problem with these
injectors so I would really like to find out if there is an
alternative to buying the very expensive manifold every time the
valve fails.

Thanks again for the input.

All the best,
Sue


Susan Ziegler
Associate Professor
Department of Biological Sciences
University of Arkansas
Fayetteville, AR  72701
479.575.6944 (lab 6342)
479.575.4010 (fax)
http://www.uark.edu/~susanz/