How do you all clean tubing prior to use?

Discussions about GC and other "gas phase" separation techniques.

12 posts Page 1 of 1
I'm getting ready to do some plumbing work, and have two 50ft coils of refrigerant grade 1/8" copper from McMaster-Carr. I bought this thinking it was "good enough", but have since read that this grade of tubing really should be solvent rinsed before using.

This will potentially be carrying hydrogen for GC-MS use, which I know can be extra picky about picking up contaminants.

I also need to carry helium(planning on a valve to switch between the two, plus the MS needs it to flush the source region during the solvent delay), argon for the collision cell in the MS, and methane or isobutane for CI.

I'm thinking of first of all rigging a solvent reservoir to force solvent-maybe pentane followed by methanol-through with nitrogen. I also see advice to dry by heating while purging with nitrogen. I don't know that i can do that easily. With that said, I have a 5890 sitting around mostly unused and currently with an injector not in use, and am thinking I can install the tubing in it as if it's a packed column(not connected to the detector) while flowing helium through. Does that sound viable? Is there anything you all would do differently?
We used tubing obtained from a chromatography company, and used that as received.
Back when we cleaned our own, before you could easily find precleaned tubing, we would solvent rinse with methylene chloride then hexane to remove any of the oil left over from manufacturing the tubing then bake it in a drying oven with a flow of nitrogen going through it. We would place a cylinder beside the oven and attach it to a regulator and needle valve then place most of the coil in the oven, heat to about 120C and let it flow overnight to remove the solvent residue. The only portion not baked is the short piece from the flow controller to the oven.
The past is there to guide us into the future, not to dwell in.
For hydrogen you should use stainless steel, not copper. That is according to all the guides I've seen for switching over. My speculation, is that copper may be more prone to corrosion in a hydrogen environment in the presence of trace oxygen or water.
Hydrogen will scavenge any contamination that exists in the tubing.
I bought mine pre-cleaned from RESTEK.
Make sure you also get a hydrogen flow snubber between regulator and line as a safety precaution if a line or valve breaks.
RE: Stainless steel versus copper tubing. Try reading this link...
viewtopic.php?t=25053
At this point, I don't - like Consumer Products Guy, I just use 'chromatography grade' copper tubing from the various GC supplies vendors that's ready to go. Been doing this too long and have too many GCs to be washing tubing. :)

Previously when I did clean tubing, I'd do basically what James recommends.

Stainless steel is preferred for use with hydrogen, but I've never used it for such, opting to use copper instead. Stainless steel is too difficult to work with and too expensive. YMMV. Copper will become brittle over time, especially with hydrogen, so we change the lines every 5-6 years. We've never had an issue. We are using hydrogen generators though. If we were using hydrogen tanks we would use stainless steel lines.
Thanks for the responses everyone.

Unfortunately, I already had a fair bit of new refrigerant grade copper tubing that I couldn't return, so since my time is cheap(relatively speaking) I thought it was worth washing rather than explaining another $100 on chromatography grade tubing.

I went in last night and pulled a few hundred mL of hexane followed by DCM through the tubing with vacuum.

I plumbed N2 to another 5890 that was sitting around, put a 1/4"-1/8" Swagelok adapter on the inlet, swaged a 1/8" swagelock nut and ferrule on, and let that go overnight at 110º at a lowish head pressure.

I then came in today and ran the line. I'm still seeing some ugly background, but hopefully that will clean up in a few days.

I know I've seen the advice to not run H2 through copper, but at the same time for a really, really long time it was standard for things like FID tubing. I've seen 30+ year old installations on the same tubing.
I had good luck cleaning the tubing with 70-80 khz sonication in hot methanol (chose it mostly because it's cheap for ultrapure grade).
benhutcherson wrote:
Thanks for the responses everyone.

Unfortunately, I already had a fair bit of new refrigerant grade copper tubing that I couldn't return, so since my time is cheap(relatively speaking) I thought it was worth washing rather than explaining another $100 on chromatography grade tubing.

I went in last night and pulled a few hundred mL of hexane followed by DCM through the tubing with vacuum.

I plumbed N2 to another 5890 that was sitting around, put a 1/4"-1/8" Swagelok adapter on the inlet, swaged a 1/8" swagelock nut and ferrule on, and let that go overnight at 110º at a lowish head pressure.

I then came in today and ran the line. I'm still seeing some ugly background, but hopefully that will clean up in a few days.

I know I've seen the advice to not run H2 through copper, but at the same time for a really, really long time it was standard for things like FID tubing. I've seen 30+ year old installations on the same tubing.


I have seen a lot of things in other old installations, just don't do as one I saw where when they didn't have any tubing they ran rubber air brake tubing between the hydrogen cylinder and the GC/ECD and couldn't figure out why they had no sensitivity. First thing I noticed when I came to trouble shoot it was the chart recorder was drawing the line on the wrong side of the paper because the signal was maxed :)
The past is there to guide us into the future, not to dwell in.
We would stand on stairs in a turret to pack columns for GC in the old days.
I rinse with acetone and that should be fine. Acetone will evaporate off fairly quickly. you can heat it in a drying oven.

I agree use stainless steel for hydrogen and definitely not refrigerator grade copper tubing. That stuff is very thin. I use it for my cheapo nitrogen drying station and definitely not for GC gas plumbing.
YES - WASH IT. I worked in a lab that had to buy 40 or 50 EPCs because someone hooked up a new carrier gas line and decided the tubing was "Clean Enough". I squirt acetone through it and then blow it out. The real problem can be dust and dirt. The flow channels in modern EPC modules are very small.
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