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- Posts: 30
- Joined: Sat Jun 11, 2016 12:04 am
- Location: Scottsdale, AZ, USA
Thank you!
Ivo H
Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.
Steve Reimer wrote:
In what way do they fail?
adoghaim wrote:
From my experience, when the agilent engineer finishes the PM, they tune the instrument too quickly, like a soon as it says ready. Normally you should allow the instrument to pump down over night. Now if that's what they done, try doing another autotune, or at least a checktune. I am thinking your instrument is just out of tune.
James_Ball wrote:
I can't get the images to open on my computer, but if the discoloration is blue to gold in color then it could be from an air leak. Even shooting clean extracts will give a bluish or gold color to the lenses if air is present. Normally you will see it on half of the repeller, but often it will appear worse on the drawout plate just to the side of the hole and on the ion focus lens inside the cup beside the hole.
James_Ball wrote:
Check in the settings for MS2, there is a mass cutoff for TTL mode which allows you to reject ions below a certain mass from reaching the detector when running in single quad mode using MS1. If that is set to something above 18, then you may have more air and water than it appears, but the MS2 is filtering it out.
James_Ball wrote:
It comes with a default setting but I don't remember exactly what it is. MS2 tab should show a check in the TTL button and the Cutoff will be the lowest mass that will pass through the quad, it rejects everything below that. It isn't exact as you will get a small response below what you set the cutoff to, but it does a good job of cleaning up that low portion of the mass range. When doing volatiles analysis I set it to 35, which is the lowest mass of the scan range and it helps with filtering out the methanol peak that comes through from the desorb of the trap. The down side is it will mask any air leak you might have. When working on tunes and looking for air leaks I set it to 18, so the air and water will pass through better.
James_Ball wrote:
That at least rules out an air leak causing the problem.
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