CI Gas Plumbing-Stainless vs. PTFE

[benhutcherson]

I'm getting ready to install a(second hand) GC-QQQ-MS with CI.

My plan is to run stainless from the three reagent gas cylinders(methane, isobutane, ammonia) into an ammonia-rated stainless manifold/selector valve. My problem comes in that I'm planning on mounting this on the wall behind the instrument, and need to get the CI reagent gas out of the manifold and into the MS.

I have a very strong dislike of working with stainless tubing, and only do it if there's no realistic alternative.

For obvious reasons, I like for my plumbing going directly into the instrument to be flexible.

For that reason, I'm wondering if it's even possible/safe to have my final connection from the manifold to the instrument be flexible PTFE.

Does anyone have any experience with this?

Of course, if it IS unsafe, I may ditch using ammonia completely and just run copper for methane/isobutane.

[Consumer Products Guy]

Make the stainless steel tubing into a coil and run to the unit; this way you could pull the unit away from the wall without disconnecting it.

[James_Ball]

Make the stainless steel tubing into a coil and run to the unit; this way you could pull the unit away from the wall without disconnecting it.

This is what we do with either stainless or copper, wrap a couple loops around a 1L bottle or something that size and you have a flexible coil. 1/8" stainless is fairly flexible, 1/4" though is quite stiff.

[benhutcherson]

Thanks guys.

1l bottle diameter is a little tighter than the 1/8" packed columns I use for some applications, and those aren't too difficult to handle.

Regardless, unless I can be convinced otherwise, I think I'm going to be ditching ammonia from the plumbing plan for this particular instrument. Airgas is leaning on me pretty heavily to fit a small storage hood to keep the ammonia cylinder in, which seems a great idea but I can't make it happen where the instrument is going. It just seems a nightmare for safe handling and also for instrument corrosion(even though the instrument IS designed for it) and I don't necessarily see it offering me any options available by selecting between methane and isobutane.

If anyone who has experience doing a lot of CI can make a good argument for running ammonia to this instrument, I'll do it, but I'm just not seeing it now.

Varian-in the site setup guide-still specs stainless for the methane and isobutane lines, so I'll probably still go with that. A stainless coil should give room to access the instrument, though. I do have a general dislike of plumbing SS vs. copper, but can deal with it, especially since my runs won't be as short on this as on my copper lines for helium and argon.

[James_Ball]

Agilent also specs stainless for the CO2 line for the LVI inlets, but copper will work just a well. The only gas I know that has problems with copper is hydrogen, but we have used copper for that for years, in fact our main lines in the building are copper from the outside tanks into the lab.

Ammonia would probably be corrosive to copper especially if any moisture got into the line so I can see stainless for that.