constant contaminant at m/z 118.123. Any advice / same prob?

[Arne]

Hi All,

we are experiencing quite intense interference from a contaminant at m/z 188.123 (See attached picture!). I was able to assign an elemental composition and I think it is diethylethanolamine. I changed the mobile phases and purged the HPLC system (using bottled HPLC water this time instead of MilliQ). That did not help at all.

What would you try cleaning next and has anyone experience this problem? I will changed the solvent lines next.Could it come from the air? The room where this MS is located does not have the greatest ventilation. We have always seen this ion but formerly at about 1% of what we see now.

Solvents are A: H2O (HPLC grade) and 0.1% formic acid from ampule. B: methanol (HPLC grade) and 0.1% formic acid from ampule.

Link to figure at higher resolution: http://i.imgur.com/jscZyPv.png

Thank you so much for your input.

Arne

[AA]

I have seen in the past amine contamination of methanol. I cant remember if we ever identified as diethylethanolamine, but is was definitely some simple amine. At this point my advice would be to go to a better grade of methanol and seem if the problem dissipates.

AA

[Arne]

AA,

thank you for your reply. We already use "Optima" grade Methanol.

I will do a few runs with a H2O/ACN based solvent system and see if the problem persists. I also noticed the same contaminant on one of our proteomics set-ups in the same room that is using ACN/water, so I am not super hopeful. It is vexing that the intensity got 100x worse in a short amount of time.

[leadazide]

Arne: Did you ever "recover" from this contaminant issue? And if so, what solved it?

[Aviator]

Hi Arne. Have you recently tuned your MS? If I remember correctly the 118 ion is one of the dominant ions in our tuning solution (sourced from Agilent) and it can remain for a fair bit of time in the detector until it goes completely.

[Arne]

Hallo,

thank you very much for your replies and suggestions. We did not recover from the issue. We are able to live with it but it is still vexing. We will replace the inner tubing (after the degasser) of the LC system next. Mass 118 is not present in our tuning solution.

Aviator: Good thought on the betaine in the Agilent tuning solution. My contaminant is a different exact mass.

Best,

Arne