We have used 1/8" valco valves under vacuum and pressure and had no problems as
long as you have the appropriate ferrules. Also, we recommmend type M rotor
material (the material inside the valve responsible for sealing among ports) as
the type P valve greatly influences 13C and 18O in CO2 samples.

andy

--- Michael Bock <[log in to unmask]> wrote:

> Dear all,
> 
> I go about building a preconcentration system for methane in small air 
> samples.
> Did anyone use Valco switching valves (6port, 1/8 or 1/4'', type 6UWE or 
> 6MWE2) under vacuum conditions?
> What leak rate did you observe at which pressures? Any recommendations 
> concerning the switching between vacuum conditions in one postion and 
> non-vacuum in the other?
> 
> Any infomation will be very much appreciated...
> 
> Regards
> Michael
> 
> -- 
> Michael Bock
> Alfred Wegener Institute for Polar and Marine Research
> Am Alten Hafen 26
> 27568 Bremerhaven
> Germany
> tel: +49-471-4831-1967
> lab: +49-471-4831-1026 
> fax: +49-471-4831-1926
> email: [log in to unmask]
> 


Andrew Schauer
Stable Isotope Ratio Facility for Environmental Research
Department of Biology
University of Utah
257 S. 1400 E.
Salt Lake City,UT 84112 USA

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801.581.8917