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- Posts: 8
- Joined: Mon Sep 14, 2020 2:35 pm
we are currently working on a Agilent 5973N GC-MS, and has for a couple of weeks been dealing with excess amounts of background noice. We have put a block on the interface to the MS to verify that the background is not coming from the columns. When running a standard injection, the noice is still the same. We also get a temperature dependence on the MS, something we have never seen before when connected to the columns. The peaks in the noice are found at almost all au's. The most dominant peaks are at 207 and 281, strongly indicating polysiloxane contaminats from the column or elsewhere (we are running with a Gerstel Septumless Head Inlet) - which is strange, since no column material is attached to the MS-chamber in this case.
https://postimg.cc/XGygQSCs
https://postimg.cc/ykBFhDXG
We have cleaned the Ion source twice with no results, the turbo-pump line looks clean, the ion chamber itself has been thoroughly examined, the ion chamber is well-sealed (10%> abundance of N2-peak relative to the 69-peak of PFTBA). The only option we can imagine is that some column material is stuck in the interface, but since the interface is at a constant temperature we cannot see the temperature dependence of this explanation.
We wonder if anybody has encountered a problem like this before, and what the solution might be.
Sorry for the long read, and we wish you a pleasant day.