Chromatography Forum

Hopefully the autotune picture will post. Power outage a few days ago. Pump stopped for a few minutes.
Believe this is rough pump oil contamination. Any thoughts? Thank you.

The tune post is very light so I can't read it on my device. Do you have a diff pump or turbo pump? It's definitely hydrocarbons, but if mass 446 is there, it's diff pump oil.

Effectively, the post is very light.
If the peak are space by 14amu apart...Foreline pump oil
If 77, 94, 115, 141, 168, 170, 262, 354, 446......Diffusion pump oil

Thanks. Appears to be a hydrocarbon signature to me too.

I'll check on the mass spacing.

I thought perhaps electronic noise but I believe that would be more of a grass look. Alot of lines, peaks close together, like grass.

Posting a new autotune. Hopefully it will post better than the previous one.

Have cleaned the MS manifold and analyzer. Replaced the ion source. Not sure what else may be contaminated. The ceramics?

Thank you.

You can suspect the column bleed too.....
For isolate this possibility, disconnect your column from interface and plug interface with ferrule with no hole...if you don't have it, you can install a short column piece (12inch) plug with a septum.

After that, pump the MS and reverify.

Thanks for the new tune post. Looks like rough pump oil to me. If it was column bleed you'd see mass 207. You may need new ceramics, but I'd clean or replace the vacuum hose going from the rough pump to the turbo or diff pump. It looks like you probably have a turbo pump and it is probably contaminated due to the back streaming so I would also clean it and replace the oil. Please let us know what you find.

This instrument has a diffusion pump. I did cap off the column from the GC and had the same pattern.

Thank you for the response. I'll replace the foreline hose and give it another look. Ceramics may need replacing if a new hose doesn't work.

Thank you.

Ok..now, your ms is isolate.
You have clean the source..have you clean the Quad?...and have you clean the Mass spec chamber?...if yes, what solvant have you use?

You can try it:
- Verify the diffusion pump fan is operating
- Heat the source to 260c and the quad to 200c for 6hours (bake-out)
- Try with a new mechanical pump..sometimes, if you have a small leak, valve have leak and produce a mist oil
- Change ou clean the electron multiplier (isopropanol for cleaning and dry it before reinstall)

Thank you. I have rinsed the Quad and associated metal parts with Methylene Chloride. Replaced the Ion Source. Replace the Multiplier. Wiped the Analyzer housing with Methylene Chloride. The autotune looks exactly as the one previously posted.

Perhaps the ceramics and the items you suggested, fan, heating etc.

I would clean the diff pump and change the oil. You can check the fan and clean or replace if needed. Clean the transfer line tip, also.

Back some years ago, we had a rough pump fail in a HP5972. We lifted the analyzer section off the top of the mass spec, removed the source and detector, and poured methylene chloride across the whole unit -- rinsing quads, mounting hardware, the plate holding everything, and all. We rinsed out the chamber as well. I think we discarded the detector and replaced it. And, we did clean the source. The diffusion pump oil had to be changed out because it was contaminated.

On pumping down we had a huge background of methylene chloride for about a week - but after that, we had a clean mass spec that we put back into service.

Agree with Don.

Thank you for all the suggestions. I'll go through and flush all that I can with Methylene Chloride.

Also will change the diffusion pump oil. Makes sense that it could be contaminated; wouldn't be surprised.

Cleaning probably won't take place until next week.

Thank you again.

I would also check your rough pump to make sure it's anti siphon ( prevents back streaming ) is working. You don't want to do all this work and the same happens again!