Hi,
Has anyone seen the tune mass spectrum changing after new installation of the GC column into the MS? Intensitties change for the single masses in the spectrum.
Can anyone help?
Best,
Julia
Dear Julia
Additionally to the suggestion of the previous reply, can you please specify the instrument brand? For example, in Agilent this problem can be caused by too deep installation of the column into the MS, as it can touch filament.
Many reasons, but a common observed difference is due to the older column being "used", fouled, dirty with poor performance (abs compounds = less signal).
Hello and many thanks for all your answers. We tried several things. We installed a new column and tried on two different Agilent GC/MS systems. On both systems the problem occurs. We checked especially how deep the column is installed into the MS.
As far as I know the tune progress should put the different mass signals of the PFTBA spectra in their predetermined ratios. But once the relative signal intensity at m/z 219 is at ~100% and once at ~200%. How is this possible?
Thank you and with regards,
Julia
Dear Julia
Is it happening (switch from 100 to 200%) every other time? Or it’s random pattern?
When 219 is 200% is 69 is 100%?
Are all other tune parameters look the same as previously? Like vacuum, EM, gain etc?
I do agree that the most disturbing thing is that two different MS show similarly bad tune. Can it be the software/communication problem? Did you try to turn MS off?
not sure but I guess You have troubles with leaks resulting in different pressures and air concentrations in the ion source.
Leaks could be at the transferline were the capillary needs to be sealed with ambient pressure on the one side and 10-4-10-5 vacuum on the other side.
The relative abundance among major ions formed from PFTBA should be constant while tuning MS though absolute counts of those ions could vary depending on many conditions within the mass spectrometer. So are you getting different ratios among ions every time?
One of the reason of this problem may be the new installed column - bleed or leaks. Repeat the MS tuning after installing the other column.
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