LTQ mass spectrometry - Zoom scan and SIM mode to analyze sample help

[aming]

a new member here, want to find some help from experts in this forum.
It is about the resolution issue of LTQ mass spectrometry, I use Zoom scan, SIM mode to analyze my sample, usually we can observe isotopic peaks for a protein, but these days, these peaks disappear, the resolution seemed to have a severe drop. what is the most likely problem I have met, sample problem or equipment problem?
Thanks in advance!

[TFSTrapMarketeer]

You could check your helium tank – sounds like it may be out. Other causes of your problem could include electronic failure (although I would expect an “all or nothing” response in this scenario) or perhaps loss of calibration. Hope this helps!

[aming]

Thanks a lot, it do helps.
Regarding the electronic failure, I observed that all the components and parameters are fine, within the torlance of setting value, so I think it might be ok.
I will check the helium tank first.

Originally Posted by TFSTrapMarketeer

You could check your helium tank – sounds like it may be out. Other causes of your problem could include electronic failure (although I would expect an “all or nothing” response in this scenario) or perhaps loss of calibration. Hope this helps!