Contamination Peak

[AA]

I have been having a consistant contamination peak with a mass (M+H) of 311. Anyone have any ideas?
AA

[Kostas Petritis]

Any additional information would be useful, i.e. LC-MS or GC-MS?, Under which conditions do you notice the pollution (i.e. mobile phase etc...)?

[AA]

LC/MS ESI+ 0.1% Formic in water vs 0.1% formic in CH3CN gradient. Although I called it contamination, it is probably better described as a ghost peak (ie a true chromatographic peak) with a mass of 311 coming off at fairly high organic percentage.. It never used to be there untill recently.

[Richard]

Hello,

Firstly I would try running a couple of different blank injections - say MeOH and then MeCN from fresh vials/ plates - to rule out solvent/ plate / vial contamination.

If that does not resolve the issue have you ruled out mobile phase contamination?

If you have contamination in your aqueous mobile phase it may build up on the column under highly aqueous conditions and then elute once the gradient runs through - hence you see a chromatographic peak at a constant retention time. To test this, leave your system running for 30 mins at the HPLC start conditions (ie high % aqueous) and then run a solvent blank, then run a second blank injection immediately afterwards. If there is a decrease in peak area in the second injection (compared to the first) this almost certainly indicates that you have a solvent contamination issue.

I have experienced many supplier issues when using pre spiked solvent for LCMS... currently I make my own.

[Newman768]

We encounterd big problems when using plastic pipettes to transfer solvents/sample solutions/acids and then analysing with a ms detector.
The softening agents from the plastic pipettes were solved and give wonderfull signals with ms.
Especially the organic acids are very good solvents for the softening agents. Just one time taking of acid from a 1 liter bottle makes this bottle unusable for further ms analytics.
Normally the softening agents gives typical signals of different masses with same delta m/z.

[Kostas Petritis]

I agree that it sounds like mobile phase contamination.

It souldn't be a polymer as Andreas suggested as you see only one peak and not a distribution...

I would go on and use clean solvents (new bottle of water and ACN) as well as new bottle of formic acid and see if that doesn't solve your problem.

I personally prepare my mobile phase inside the bottles that the solvents comes. If you make your HPLC water, change to a commercial bottle HPLC water to make sure that it is not your water cartidges...

[AA]

First of all, thanks for the replies. When I had first posted the message (and still) I was interested if anyone had seen this mass before and, hopefully, had identified it. This is not my first run in with this mass but I have not seen it for 8 or 9 years. I didn't identifiy the cause (or the compound) that time either. Unfortunatly, this contamination (ghost) peak does not seem to come from the usual sources.

And just as another note, a previous poster mentioned the use of bottled water. In my opinion bottled water is, by far, the greatest source of contamination, both LC and MS. A high quality, well maintained water system will always be better that bottled "HPLC Grade" water.

AA

[AA]

I personally prepare my mobile phase inside the bottles that the solvents comes. If you make your HPLC water, change to a commercial bottle HPLC water to make sure that it is not your water cartidges...

You will stop making mobile phase in the bottles the solvent comes in after the first time you leach silicate from the poor quality glass and tear up your pump seals (I've seen it happen).

AA

[Kostas Petritis]

Actually we do not use bottle HPLC water but Millipore type water. I order and use bottle water only in the case we have somekind of contamination, in order to eliminate our water system as the source of the contamination...

Sorry for not being more clear about this...

Kostas

[Newman768]

Kostas wrote:

It souldn't be a polymer as Andreas suggested as you see only one peak and not a distribution...

I think you are right with the contamination.
But at high % of organic the polymer is more likely to eluate as one peak than as distribution. Nevertheless MS spectra shows a very typical m/z distribution.

To add another possible source of contamination: the flask
We had trouble with contamination peaks coming from the flasks.
The "joke" was: nearly all the flasks from one washing were contaminated.

[Newman768]

Kostas wrote:

It souldn't be a polymer as Andreas suggested as you see only one peak and not a distribution...

I think you are right with the contamination.
But at high % of organic the polymer is more likely to eluate as one peak than as distribution. Nevertheless MS spectra shows a very typical m/z distribution.

To add another possible source of contamination: the flask
We had trouble with contamination peaks coming from the flasks.
The "joke" was: nearly all the flasks from one washing were contaminated.

[Ericz]

I saw three (309, 310, 311) when I infused sample (even blank, especially with ACN) using syringe pump. I have no idea about them. However they went away after changing syringe and tube (PEEK).