Chromatography Forum

Hello,

I bought an old GCQ Plus and after I finished repairing it, I finally powered up the system. I changed new oil in vacuum pump, baked the column on 300 C for 5 hours, then let it rest at 100 C for 3 days. I have water/oxigen trap installed, and very good quality He gas. I set the EPC to 40cm/s. New liner, new septa. Set for splitless mode. Injector at 250 C. I mention the transfer line's vespel tip is nicked (chipped), can it be a problem ? Also I noticed the oil from the vacuum pump is translucent before powering it up, but not anymore after powering it up. It become like an grey emulsion. Can that be a problem ?

I get this air/water spectrum. I am newbie and I am not sure what is wrong.



What I do notice is the very high H30+ and 02 peaks, and the lack of the common N2 peak. The small bump before H30+ might be H20 at 18. Also thre are 3 little small bumps at 28, 29 and 30. If the one at 28 is the N2 then I have huge water leaking problems. Please notice the IonTime at 0.49 ms, where it should be at 25 ms. But maybe I am wrong, as I said, I am newbie.

Can it be something wrong with the settings ? Multiplier ?

Please help me with some hints.

Thank you
Vlad Popovici

Hello,

as an update, I isolated the MS with the transfer line cap, so I can confirm the water is not coming from GC. I changed the pump oil, and let it for 1 hour on ballast. I opened the MS and cleaned it on the inside. There were a lot of oil droplets (perhaps since I shut it off without shutdown due to problems I had at that time), I also found a little column fragment.

However nothing changed. My ghost water source remained and I actually contaminated it since I washed it with a not-so-pure ethanol.

Today I will bypass the internal water traps and I will completely disassemble and wash the ion volume. If nothing works, I don't know...

So I am back to start.

I don't know thos particular instrument, but as I look at it, H3O+? I would expect that in a soft ionization environment, but not EI. Could you be looking at m/z 18 and 28 with the mass calibration being way off? Have you done a mass calibration since completing repairs?

Hi,

yes I did a mass calibration. All OK there. Actually all the auto-tests are OK. The only weird thing is that huge H3O+ peak. And I presume the 32 is the recombined oxygen molecules ripped from H20. I checked for leaks with Ar. No leaks whatsoever. I separated the GC from the detector, and the water comes from the detector, not from the GC. I cleaned the vacuum room, same result. I didn't cleaned the ionization volume yet, since I don't have the tool to extract it. Hopefully tomorrow I will clean that too.

Regards

Hi,

actually it seem all is OK and this a good looking spectra for Thermo equipment. Didn't knew that...

My problem with low IonTime was because the geniuses from Spectralab that sold me the equipment filled the little bottle with the calibration compound and manually let the valve on ON. The liquid was draining in the vacuum chamber and heavily contaminated the detector with the calibration compound. It took one day to clean the most of it. Now everything is OK.

Regards,
Vlad