Chromatography Forum

Our Agilent GC 6890 /MS 5973N system was recently turned off without venting and small splashes of foreline pump fluid were visible when the analyser chamber was opened.
I tried to clean it out with IPA and kimwipes, but changed to the Agilent cloth (cotton?) wipes as the kimwipes were breaking up and leaving fragments.
I seemed to clean up most of the oil from the chamber except for the grooves on the bottom of the chamber near the source. I stuck the cloth in there and used a screw driver to move it around, but this left scratches were it slipped from the cloth so I changed to a plastic ruler. I was cleaning it out like this for about an hour but not much progress was made. I can still see the oily sheen in the bottom of the grooves. Is there any better ways of cleaning it?

I think MeCl2 works better than IPA. Also IPA can linger. I've rinsed inlets and liners with it and had it linger for the better part of a day. MeCl2 and lots of swabs and kim wipes.

If this is a diffusion pump system, that is likely diffusion pump oil - I have routinely seen this and never really had to clean it up. At worst case, I have seen a short term background of 406 ion.

I usually just run a dry kimwipe over the seal, more to ensure the oil has not allowed dust to adhere.

Remove the side door and wipe out the chamber with MeCL2 and some of the cloth in the tool kit ( the only solvent that seems to work with dif pump oil). Clean your source. I seem to remember hearing that you can rinse the quads on a 73/75 but I would suggest confirming this with Agilent first.

thanks for the help, I've managed to clean it.
but i've got a bigger problem now, after cleaning it won't pump down. I'll make a new thread on it

This sounds unpleasnet but I might be in the same situation. Like the original poster, FBProc, we have a Agilent GC 6890 /MS 5973N. While working on the injection port Friday I bumped the column and it snapped off a the MS interface (no, this isn't what I was posting about last week... this is a different instrument...). I immediately vented the system. (Feedback request: was that the right thing to do? Anything else I could have done?)

So, under the above circumstances would it be expected for pressure to be lost through the broken bit of column, and for oil to make its way up into the analyzer chamber? I can see quite a bit of oil in the grooves at the bottom of the chamber, but Yama001 mentioned that some amount of it might not be terrible. I can see places where it seems beaded up a little bit, so I'd guess that's more than normal. I guess I'll just clean it up as best I can and clean the source, but if anyone has suggestions for how to avoid this (other than not beign a klutz in the first place)...

our machine is fine now. however we just lost power in the lab for about 10-15 mins. the machine pumped down almost instantly when I turned it back on.
just wondering if this would have caused pump fluid to go back in the analyzing chamber? I hope I don't have to clean it again
before it wasn't that much of an issue, just had to clean the large visible droplets basically. it was more difficult to get it a good seal again then it was to clean up the oil.

Generally roughing pumps (the big one that pumps against atmospheric pressure) have a valve that prevents counter flow of air in case of shutdown, hence they remain sealtight and there should be no problem of oil backflow from the diffusion pump. However one can forget open the gas ballast valve, or in old pumps the valve can break or leak. In those cases the diffusion oil can splash!

Regarding the scenario where the column is snapped off at the interface - I would just put a GC septum over the column (or flush against the nut) and vent nomally. Allowing air into the manifold at high temperatures may oxidize the source and the analyzer.

Regarding the scenario where the column is snapped off at the interface - I would just put a GC septum over the column (or flush against the nut) and vent nomally. Allowing air into the manifold at high temperatures may oxidize the source and the analyzer.

Agreed. A broken column will cause more problems with oxidized source than with the diffusion pump, especially if the rough pump is still pumping. Just run through the vent cycle then repair the column and check the source to see if it is a goldish or blueish color, if so clean it, that is the sign it was oxidized.

If you have had a diffusion pump unit running for several months without venting you will normally see several large droplets of oil on the baffles when you open the analyzer, it is common. Unless you see the oil our away from the baffles(fins) in the bottom of the analyzer or on the radiator surrounding the quads, don't be too worried. If you see oil on the radiator then you have had serious backstreaming and it probably means the valve in the rough pump has gone bad and allowing the air to flow backwards from the rough pump once it has been turned off.

Not since the days when I used the old HP 5995 with the massive water cooled diffusion pumps they used have I encountered problems with oil backstreaming due to minor power outages and such.