We have a huge contaminant at 100.0757 m/z that we think is methylpyrrolidone [M+H]+.
We're using a gradient of MP A: H2O (0.1% Formic acid) and MP B: ACN (0.1%formic acid) on a C18 column.
Switching from ACN to MeOH did not help. Switching formic acid brands did not help.
Highest abundance seems to be at high organic concentrations. Does anyone know the source(s) of this contaminant or how to get rid of it?
Dear Lauren, You will find the "Interferences and contaminants encountered in modern
mass spectrometry" in Analytica Chimica Acta by Randy Whittal an extremely useful reference.
Has someone thoroughly washed the HPLC solvent bottles before refilling with ultra clean solvents?
It is a floor stripper, they write. If you have floor renovation taking place somewhere, contamination might be coming from there.
Did you check if the contamination is in the LC or in the source part of the MS? Is the nitrogen supply still ok (carbon filter)? Since I test the solvents in my lab I always have trouble with contaminations. Usually 8-10% formic acid in water and a mixture of methanol/acetonitrile/2-propanol (1/1/1) remove most the compounds. You should flush all solvent channels with these 2 mixtures for a longer time at higher flow rates. Especially the degasser is sometimes like a sponge. Before you start remove the column. 8% formic acid is a very strong acid and will damage the stationary phase.
If you are lucky then cleaning the source (including ion transfer) or exchanging the N2 filter may remove the problem.
Are you analyzing urethanes? polyurethane dipersions generally contain NMP.
Thank you all for your suggestions. In the end we were able to clean it out by pumping IPA:H2O with a bit of MeOH through the system overnight.
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