Chromatography Forum

On one of our purge and trap GC-MS systems we are seeing random noise peaks appear. By 'noise peak' I mean non-Gaussian TIC peaks made up of mass fragments of varying abundance (although all within 1000 counts of each other in any particular scan). They are non-centroidal so appear as e.g. 101.1, 101.8, 102.5, 102.7, etc. and there are peaks across the full scan range (e.g. between 30 and 250 m/z there are 220 peaks). The peaks affect a cluster of chromatograms in the sequence and appear approximately every 2 weeks. The peaks do not appear at any particular retention time, they are randomly dispersed throughout the TIC. I'll post a pic if I can find somewhere to host it.

This first happened after ion source maintenance. We assumed the EM or HED had been disturbed so we checked the connection and blew away any dust with an air spray. we didn't see the noise until a few weeks later and it has periodically appeared since then. I assume the detector is recording a signal intermittently within a run, but I don't know if it is an electronics issue, or if something is physically creating a signal.

Has anyone else had similar issues?

System is an Agilent 6890/5973 MSD.

Thanks

Hello

Run autotune...and see result. Perhaps dynode needs good cleaning.

Regards

Tomasz Kubowicz

Sometimes this will happen if you run the EM voltage too high.

I had that show up on a 6890/5973, although it wasn't intermittent. The high voltage lead (looks like the coil wire for a car) was arcing on one end. Trying to run a tune was futile.

The tune is fine. Can't see anything unusual, but the emvolts are up there - 2500 at the moment.

We see this when our EM is starting to die; sounds like a good time to replace it.

This sounds very similar to a problem I am currently having and just posted about. Did you find the solution, was it the EM as mckrause suggested?