Chromatography Forum

Has anybody an idea concerning what kind of polymer resulted in spectra, depicted below:
(ESI "minus", LCQ Advantage MAX ion trap, C18, a source of pollution is unknown, exist in any sample, maybe, came from the injector wash solution?)

RP gradient from 20 per cent of MeCN in 0,1% HCOOH in water, to 90% MeCN. Sample load- partial loop filling (10uL).

Looks like PVFD: repetitive unit is 64 Da, the smaller peaks are the larger peak mass - 19 (= F).
Are there any PVFD membranes or seals in your sample prep pathway?
Jörg

I just remembered that acetonitrile was filtered through a 0.45 um membrane (usually not) due to some particles in it. I'll check if that membrane was made of PVDF. It was a big mistake....
Oh, my God... Thank you for a good idea.

Strewth, do you know what these peaks actually are, molecular formula? This looks like a superb mid-range calibration standard for a ToF!

Strewth, do you know what these peaks actually are, molecular formula? This looks like a superb mid-range calibration standard for a ToF!

Could be something like
[CH3(C2H2F2)nCH=CH2 - H]-
with n=10 for the first Peak (681) plus 64 for each (C2H2F2) unit.
Jörg

with n=10 for the first Peak (681) plus 64 for each (C2H2F2) unit.
Jörg

Very possible. Due to the strong electron withdrawing effect of fluorine, proton is lost easily, forming relatively stable carbanions. Therefore, relatively small amount of the polymer impurity generates a high signal.
Finally, its hydrophobicity explains long retention in a C18 column.