Which background ions should you expect to see?

[cene]

Hi all

I have just moved our GCMS to a new lab and am running some blanks to see if there are any contaminants in the system. I know we need to see a clean baseline with no peaks and only a low level of bleed, but I am interested to know which ions are "typically" seen in the background of a blank sample and in what ratios. For example, in a blank run I typically see m/z 36, 40 and 44 with insignificant amounts of other ions. I'm not scanning below 30 m/z so I might be missing anything lower than that. I'm using helium as carrier.

So, what ions should normally be seen in the background and is this consistent across all systems?

[Rndirk]

A lot of contaminants are indeed common across different systems.

I can't link the document since it's a pdf, but if you google "gcms common contaminants", first link is an Agilent document (from Researchgate) with a nice table listing m/z and sources.

For example, you'll find argon (40) and CO2 (44) on most systems.

[cene]

A lot of contaminants are indeed common across different systems.

I can't link the document since it's a pdf, but if you google "gcms common contaminants", first link is an Agilent document (from Researchgate) with a nice table listing m/z and sources.

For example, you'll find argon (40) and CO2 (44) on most systems.

Yes, I have looked at that document before and it's a useful guide. It doesn't list anything with m/z 36 - any ideas what this could be on my system?