GC/MS is flooded with mass 11.6 ???

[thohry]

Hello,

Anyone ever have the problem of GC/MS having large peak at 11.6 amu ?
I still can see peaks 69, 219 and 502, but the peakwidth is more than 10 times and normal.

Thanks for any suggestion.

[JMB]

Are you scanning down to m/z 10?
You will burn out the multiplier with the m/ 18, 28 and 32 signals. People generally set scan range at m/z 40-540 or similar in EI mode.
Are the m/z 69, 219 and 512 ions ALL at 10x normal peak width?
Tuning lenses may need cleaning, and/ or resolution potentiometers may need resetting.
Regards,
JMB

[thohry]

Are you scanning down to m/z 10?
You will burn out the multiplier with the m/ 18, 28 and 32 signals. People generally set scan range at m/z 40-540 or similar in EI mode.
Are the m/z 69, 219 and 512 ions ALL at 10x normal peak width?
Tuning lenses may need cleaning, and/ or resolution potentiometers may need resetting.
Regards,
JMB

Thanks for your input.
The peaks 69, 219 and 502 have quite normal shape, only too large !.
We cleaned the source already.

[James_Ball]

Are you scanning down to m/z 10?
You will burn out the multiplier with the m/ 18, 28 and 32 signals. People generally set scan range at m/z 40-540 or similar in EI mode.
Are the m/z 69, 219 and 512 ions ALL at 10x normal peak width?
Tuning lenses may need cleaning, and/ or resolution potentiometers may need resetting.
Regards,
JMB

Thanks for your input.
The peaks 69, 219 and 502 have quite normal shape, only too large !.
We cleaned the source already.

Have you ran a peak width calibration in the tune menu? That should fix the wide peak widths, if not then either there is a problem in the quad electronics or you have a really bad leak. The low mass peak you are seeing could be 18m/z from water.

Another thought, make sure you did not get a tank of Nitrogen instead of Helium installed, they have the same fitting so they can be installed by mistake, that would give a massive 28 and possibly 14 mass that could be the 12 that you are seeing.