MS Bakeout

[Gugu]

Hi

Would like to know. Is there a difference between a column and detector bake-out? Is there even such a thing? I am having trouble with high Nitrogen on my GC-MS and was told to bake-out the MS but was not told how to since I was never trained (learned most things all by myself).

Please help

GG

[Steve Reimer]

Other than letting it pump down overnight at operating temperature, no there isn't an MS bakeout. High nitrogen is more likely from a leak before your scrubber or from your helium. Usually, water is the one that is the most persistent on the metal surfaces.

[Peter Apps]

What system do you have ?

The Varian Bruker 320 ms has a system bakeout which helps to clean things up, but it will not do anything about high nitrogen levels.

Peter

[Bigbear]

Agilent chem station software starting with E02.02 has a bake out macro. We use it after source cleaning.
As Peter said, it will do nothing for the nitrogen if you have a leak. I monitor M/Z 28 with the calibration valve closed, if it is <25000 counts, I feel there is no leak.

[James_Ball]

Agilent chem station software starting with E02.02 has a bake out macro. We use it after source cleaning.
As Peter said, it will do nothing for the nitrogen if you have a leak. I monitor M/Z 28 with the calibration valve closed, if it is <25000 counts, I feel there is no leak.

I use this on our Agilent systems and it will help lower N2 a little more quickly if you are putting in new insulators or something like that which has never been under vacuum before, but pumping down over a weekend will also have the same effect. Heating it up just helps it desorb faster. It helps most with water contamination and can remove some buildup of sample residues to give you a little more run time between source cleanings.

In the N2 is constantly high, they you have a leak. If N2, O2 and CO2 are high it could be a leak at the analyzer or column fitting, if the O2 and CO2 are low, but N2 high then could be in gas line before any gas traps, which should remove everything but N2. Also if your helium tank is down to the last 500psi you can see N2 begin to increase as it settles to the bottom of gas cylinders and becomes more concentrated in the mix as you remove Helium especially down at the very last of the tank.

[Gugu]

Hi

Sorry for replying so late. When I started working with the machine, I was warned of two loose screws on the ion source housing and I believe that those were causing the housing not to create enough vacuum. So I created a support pad as an experiment to see if helping to hold down the source housing would help and it actually did. The housing was re-threaded then and is now held down properly by screws, the N2 levels remained low for a couple of days and then shot up again. It has been fluctuating for two weeks now and I am also suspecting the foreline pump since it has a leak.