Ion Trap Cleaning

[Scimel]

To clean ion trap parts in methylene chloride or methanol? Dry in air or 200 degree Celsius heat, reassemling without total cooling? Got conflicting responses from Tech Support. One says always methylene chloride, other (alleged more experienced one) say no way, never. What to do? On HP-Agilent I always used methanol, but for Varian manual says to use methylene chloride. What to do?

We have a Varian Ion Trap MS that required cleaning due to an elevation in the baseline at high mass. I sonicated in methylene chloride and dried in air according to the manual instructions. After re-assembly, conditioning, and bake-out I had a loss in sensitivity. All but one peak (smallest one-hexachlorobenzene) identified in the Column Test Mix.

Some components (gate electrode and electron gate) are on order and will be replaced once received. I expect to enhance sensitivity there.

Despite the parts relacement I contacted tech support twice for advice. Once, for the methodical steps to increase the sensitivity and secondly to inquire if the silichrome coloring (purple or blue) makes a difference. Got distracted by the methanol/methylene chloride argument.

Any advice would be appreciated.

[WK]

Hi Schimel,
I have one too with Silchrom electrodes. Its 5-7years old now and the electrode with several holes is a little dirty even after sonicating in methylene chloride.
I have only used methylene chloride to clean Silchrom electrodes.
I understand that Restek can perform a re-coating of the Silchrom layer.
Have you cleaned them with any other solvents?
Should I replace my electrodes now?
Have you ever cleaned anything else in the trap other than electrodes and the quartz spacers?
WK

[Scimel]

I followed the manual directions for methylene chloride. I used the aluminum oxide slurry to polish the uncoated parts of the gate and the gate conductor. Since I didn't have replacements, I attempted to restore the shine by polishing them with extremely fine grit (0.5 micron)sandpaper. Worked fairly well but not great.

Problem is those parts are not supposed to be handled, rather they are simply replaced periodically. In this instrument those parts likely have not been cleaned or replaced since 2000 or 2001. Since fairly clean straight-forward ignitable liquid samples have been injected I didn't expect too much debris. Surprisingly to tech support, I managed to get 11 of the 12 peaks in the test mix. But, the last one is the critical one. I have also since cleaned the injector to maximize sample input on the front end of the analysis.

According to Tech Support if debris is apparent on the electrodes, a mild, neutral pH soap slurry and soft toothbrush can be gently used to scrub the electrodes with caution exercised to prevent scratching the silichrome coating. Wash each piece separately in the slurry to avoid contacting surfaces. The one person suggested "Isoderm" neutral pH face wash soap from the pharmacy. (Not sure if you have that in the UK.) Rinse well with DI-water, sonciate 10 minutes with DI-water, then sonicate 5 minutes in methanol or methylene chloride (despite the other person discouraging it's use).

[WK]

Thanks Scimel,
This is interesting information.
I have a lot of noise in the "hairy" baseline at the moment.
The engineer tweaked the circuit board which does the zeroing (first action when tuning EM automatically) and that eventually needs replacing.
Have you had this replaced? Its quite expensive.

Perhaps I'll try the brush and soap with a methanol rinse next time.
I would have thought the Silchrom would be inert to most solvents.
I guess the layer is like deactivation in an inlet liner such that if you keep cooling and heating it eventually loses deactivation.

Keep posting - especially when you get new electrodes - are they expensive?

WK

[Scimel]

Latest update...according to a reliable source, all the organic solvents will eventually evaporate off. To meticulously clean with methanol and reassemble and get back into the evacuated and heated manifold while still warm is a means to keep things (oils, moisture, etc) from condensing on the electrodes from the atmosphere. However, baking the system overnight will clear the methanol. The methylene chloride will be evident for longer, likely "disappearing" after 2-3 days. So, if the solvent clearing is critical to your analysis be more meticulous in the handling.

My source also said that if you see a lot of noise in the 500-600 range, then the trap needs to be cleaned of any debris (septa bits, etc). You may consider giving the electrodes a good scrub to eliminate some of the noise.

As for the replacements...go to varianinc.com, create a user account and all the prices will be available to you.

The prices are as follows:
Quartz spacer, silichrome-coated $550 each (need 2 of these)
RF electrode, silichrome-coated $809
Filament end cap, silichrome-coated $616
Exit end cap, silichrome-coated $704

Also, I learned that silichrome on quartz appears as shiny white metal, but silichrome on metal appears as blue. Originally, I thought my shiny spacers were metal, only to find that they are silichrome-coated quartz.

I came to this position just two months ago so I have limited information from the logbook as to what has occurred with these instruments. Consequently, I cannot comment further on your situation.

[WK]

Scimel,
I had the SAP-wave board replaced the other day and this has improved the "noise" in the mass spectra considerably. The newer boards contain a chip which can be replaced but ours was an old board so the chip was soldered in (hence new board required).
I had a "carpet" of all masses through the mass spectra and the integrator would not zero in the tune section (always high). File sizes were also high. Therefore the source of my noise was electronic and not chemical - instantly the ion time hit 25000.
I did notice when using wool in the injector that this created a lot of extra peaks and background so I have stopped using it for a while.

WK

[Scimel]

Glad you found the source of your angst. Good information to have, so thanks for posting it.

As for the wool...are you using glass wool or quartz wool? Glass wool will often give you extra, unwanted peaks.

[WK]

Hi Scimel,
I'm using silane treated glass wool.
Will try some quartz wool soon.
Is quartz = borosilicate?

Have you tried siltek wool or borosilicate wool from Restek?

WK