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Tue, 24 Jan 2006 15:53:10 -0500 |
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HI Toti--
I've swapped teflon out for PEEK (partially) since it's pretty inert,
much less permeable than Teflon (in general), however it is more
permeable than stainless and doesn't like to get too hot (not much above
100oC) in our EA setup running sulfur. From Upchurch scientific,
http://www.upchurch.com/TechInfo/matPeek.asp, O2 permeability is 14cc /
100in^2 * 24h * atm / mil @ 25° C--a lot better than Teflon, but not as
good as stainless. Tubing runs around 30 mil wall thickness (or more),
and air ~20% O2 (keep math easy), so 14*0.2/30=1 (round off). So
something like 1 mL of O2 will leak in over a day if you have 100in2
surface area. Basically, you'll see a (small) increase in your
background gas levels. If the blank runs are ok, it should be fine. I
doesn't seem to leach anything--just don't take a heat gun to it.
McMaster-Carr and Small Parts have capillary stainless tubing (clean
before use) if you need some flexibility with the stainless should you
end up swapping out the PEEK.
take care
gerry
p.s. all I can find on CO2 permeability is "low". If I recall correctly,
CO2 permeability is lower than O2--but I can't find the gas permeability
charts for peek, only the chemical resistance ones (and they don't list
PEEK).
[log in to unmask] wrote:
> Folks,
>
> Has any one replaced stainless steel tubing with PEEK tubing to carry
> He+ sample gas to either a Multiflow or Gasbench? Has anyone noticed
> any reaction with PEEK tubing and different gases?
> Right now I have a stretch of PEEK tubing supplying Helium to the
> flush end of a two-holed needle and 1/16th inch stainless steel tubing
> to carry Helium + sample gas (either CO2 or N2O in my case) to a GV
> multiflow/Tracegas. There is no SO2, H2S, H3PO4 involved in this
> method. I'm more comfortable with stainless steel, but maybe PEEK
> tubing is inert to CO2 and N2O?
>
> Thanks
> Toti.
>
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