Contamination m/z 118.1230 on a LC-QTOF

Were you or anyone else ever able to resolve this issue? We are also observing the same 118.12 contaminant, and we also have a Peak N2 generator, and I am wondering if the contaminant is coming from the generator itself or if it is an ambient air issue.

No real progress here. We are using it now as a reference mass. There was a post on chromforum.org that had strong evidence the compound is diethanolamine. 

In our case it is higher signal intensity than the 118.09 reference ion, and it's causing the system to tune incorrectly at the lower mass range.

Ahh ok. This is what we've done: Purchase and prepare fresh ESI-L, flush your CDS with fresh and clean ACN -> water -> ACN and then put on your fresh ESI-L. 

ACN->water->ACN did remove that ion quite well, but my brand new tuning mix (prepared with ACN/water from the same bottles as the wash) still shows the 118.12 peak. Could this be coming directly from the ESI-L?

Alternatively what are the chances it actually is the 118.08 calibrant, and the contaminant is actually a lower mw 118.05 species? (In either case though, it seems to be coming directly from Agilent's ESI-L)

ACN->water->ACN did remove that ion quite well, but my brand new tuning mix (prepared with ACN/water from the same bottles as the wash) still shows the 118.12 peak. Could this be coming directly from the ESI-L?

Alternatively what are the chances it actually is the 118.08 calibrant, and the contaminant is actually a lower mw 118.05 species? (In either case though, it seems to be coming directly from Agilent's ESI-L)

Yes, those are all things we considered as well, but given that this contaminant is not observed in other labs (we have colleagues using the ESI-L mix in other labs that do not observe this ion) and that it builds up over time I don't think it comes from the bottle itself.

And this researcher makes a very convincing case at what the ion is:

www.chromforum.org/viewtopic.php