Chromatography Forum

Greetings All,

I operate a Bruker 300 MS attached to a Varian 450 GC. The MS has been giving strange responses.

Here is an example of what the GC trace looks like: http://i.imgur.com/jNsQOgx.png
And here is a pic that is zoomed in: http://i.imgur.com/oPZZxnE.png
The noise seems to be periodic.

The MS was working fine, but then we had to change the filament and the turbo pump controller. The weird signal started after that.

We have tried cleaning the new filament connector as well as the ion volume. I don't believe the issue is with the GC because I see the same noisy response when running the calibration gas.

Any ideas or insight as to what is causing this issue would be very helpful.

Thank you!
Andrew

The MS was working fine, but then we had to change the filament and the turbo pump controller. The weird signal started after that.

Any ideas or insight as to what is causing this issue would be very helpful.

It looks like an electrical issue (ground loop etc.).

We had something similar with our Agilent 5975, although the peaks were a little bit more sporadic. The spectra of the strange peaks looked like a comb with every ion showing a response. After changing the high energy diode the problem was gone.

It looks like an electrical issue (ground loop etc.).

Do you know if there a relatively easy way to determine what is causing the electrical issue? Or is this something that an electrician would have to look at?

We had something similar with our Agilent 5975, although the peaks were a little bit more sporadic. The spectra of the strange peaks looked like a comb with every ion showing a response. After changing the high energy diode the problem was gone.

How were you able to determine the diode was the issue?

Do you know if there a relatively easy way to determine what is causing the electrical issue?

No. Usually at start point engineers check control points on PCB. Your issue appeared after replacment filament and controller of turbo, so, you need to carefully check these points at first (errors of assembly and installation, malfunction of turbo controller etc.).

We had something similar with our Agilent 5975, although the peaks were a little bit more sporadic. The spectra of the strange peaks looked like a comb with every ion showing a response. After changing the high energy diode the problem was gone.

How were you able to determine the diode was the issue?

After cleaning the source and the diode itself we still had the problem. All connections appeared good and all advice indicated that it was either the multiplier or, more likely, the diode. Since you cannot order an HED without a multiplier from agilent and we did not have a spare multiplier to check out, we just ordered the whole assembly and after installation the problem went away.

If one has a spare multiplier that would be the thing to test prior to ordering the whole assembly if all advice is indicative of either a multiplier or HED problem.

I had a possibly related problem last year. I had just cleaned the source and replaced the filiments on my 5973inert. All I got for signal was random noise on every mass with no peaks. I swapped the side board, detector finally sent it in for troubleshooting. It turned out to be defective filament assemblies that sagged when hot and shorted out just enough against the source body to give a random signal that the instrument interpreted as random noise of all masses across the entire spectrum.

So, I suggest you try a different filiment assembly and see if the problem persists.