LCMS contamination

[ddetata]

Has anyone experienced contamination in their LCMS system-dominated by a 354 molecular ion?. I am using MEOH:Ammonium formate pH3 solvents and the problem has persisted for some weeks now. Higher grade MEOH doesnt alter the quantity of this ion either.
Any ideas????
CHeers

[Kostas Petritis]

Doesn't ring any bells and I haven't seen such an ion in all the ESI contamination lists I have. As you have excluded the possibility of MeOH the problem could come from your water system or from contaminated salt.

Use only water:MeOH with some acid to see if the problem persists (if not then it is maybe the salt). In order to check if it is your water, use bottle HPLC water.

[ddetata]

Thanks for the reply,

Tried running pure MEOH, ACN, and water-each time the 354ion is present. The contamination is throughout the system? any suggestions for cleaning the system-i have heard of using dilute HNO3??
CHeers,

[Kostas Petritis]

Before you try to clean anything try to infuse first the same solvents.

If you do not see the contamination then you can blame the LC and you can try to clean it. If you see the contamination then it can be only the MS or both the LC and the MS.

Start by cleaning first the MS and infuse again (you should be sure that the MS is clean). Then I would let the LC-MS run and see if I see the contamination. If you do not see contamination it is only the MS, if you see the contamination (and at this case you should stop immediatly because you do not want again to contaminate your MS) you should go on and clean your LC...

[ddetata]

Cheers,

A number of methanol solutions from various companies have proven to be the source of contamination of the whole system!
We have redistilled the HPLC grade methanol and the interfering ion has slowly disappeared.
Thanks all