Hello all,
We have been running intact MS on some mAb samples and we always use a standard mAb in our runs. we are using an Agilent 6230 LC/TOF. Mobile phases are 0.1 % Formic acid in ACN/ 0.1% formic acid in water, flow 0.3 mL/min, PLRP reverse phase column. Every time we run changing different parameters on the TOF-MS, the standard mAb is always present in the mass spectrum, but the sample mAb doesn't show up in the mass spectrum (even though the UV trace from the LC portion shows the elution of the sample and standard mAbs).Please find the attached MS profiles. When we ran the same standard and sample mAbs on Thermo Q-exactive, we were able to see the presence of sample mAb in the mass spectrum.
If anyone is familiar with this kind of problem, please let me know how to resolve the issue. I would highly appreciate your help.
Thanks!
It is clearly a case of ion suppression. Your compound of interest does not ionize because there are other interfering ions in the sample that block its ionization process.
The re are two possible explanation for the observed difference between the 6230 LC/TOF and the Q-exactive:
1) is the chromatographic run exactly the same in the 6230 LC/TOF and the Q-exactive? Consider that even small difference in RT may elute at different RTs different molecules and so allowing (or not) the ionization of your antibody.
2) If the RT is exactly the same in both instruments, the difference in the ionization efficiency between the two instruments is in the geometry of the ion source...
In any case, the solution is to try to clean up more your sample and to change the chromatographic conditions and the parameters of the ion source of the 6230 LC/TOF.
regards
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