Micromass Autospec Ultima - setting Source Slit limits

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

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Having an issue with my source slit not closing completely, and I'm investigating the possibility that the Source Slit Setup has shifted. Closing the slider reduces the intensity of the peak as normal until a reading of about 13(/100) but from 13 to 0 the peak doesn't get any smaller.

I've seen a procedure for setting the Collector Slit limits before, but as the collector slit is right by the detector, it's a lot easier to see the effect you're having.

Anyone have any tips for setting/checking the Limits for the Source Slit Setup?

(Have also checked that the Instrument setup file hasn't been corrupted and it hasn't changed since the last time it was set).

Thanks for any help!
Theoretically if you set the lower limits for both the left and right slit to 0 in the slit setup and then set the main slider to zero they should shut light tight.

However my feeling here is that the slits are actually damaged, the ion beam eventually erodes the edge of the slits creating a small hole and therefore they can't close light tight.
give an email address and I'll send the slit setup procedure
Would appreciate that MHR311. My email is pblo2287@gmail.com.

It "feels" like the settings and the slit blades were ok at it's last PM (sealing light tight). Nothing on the instrument is too new though. We used to have an ex-Micromass Engineer servicing the instrument but he's retired and I'm not as competent!
The problem you describe is probably not the slit limits, it's the slit itself.
Carbon builds up between the blades where the beam passes through.
Once enough carbon builds up the blades no longer close.
You likely need your slit cleaned and re-aligned.
If you have never done this before, it is highly recommended that you leave this chore to someone who has experience is doing this.

'Crabs
A little late to the game, but I would agree with the slits being physically damaged. I had a Thermo DFS (not micromass) but the theory is the same. Over time and a lot of use at high RP (10,000 or >) the slits get worn from the ion beam. I have an old front slit from a MAT 90 or some previous generation that has clear signs of wear if you look real close with a magnifying lens. Thermo considers this pretty much a "consumable" item with a limited lifespan. However, usually at this point of slit degradation you would have trouble achieving 10,000 RP. At least this was the case on the Thermo system. I solve all of those problems and purchased a QExactive-GC system. :D 120,000 RP and 1 ppm mass error with the click of a button. Much different MS fundamentally though.
~Ty~
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