Cannot find the transition in GC/QQQ at a known Ret.time

[Joana Pico]

Hello everyone,

I would like to know if someone has experienced the same problem I have working in MS/MS (product ions mode) using GC/QQQ. I am working with an Agilent GC 7890A/MS triple Quad 7000A, with the collision cell at 45 eV mode to get the product ions of a selected parent ion (m/z 173 of a BSTFA derivatized compound). I can perfectly see the m/z 173, but when I work in MS/MS mode, the peak in the chromatogram corresponding to the transition 173 -> ** disappears at the retention time where I see the peak in MS mode (thus, I cannot click on it to obtain the product ions spectra). I am using Mass Hunter version 10.

I know it is not a problem with the equipment because I can see the peak in the chromatogram corresponding to other transitions, and I can indeed see peaks of the transition 173 -> ** at other retention times. There is noise in the baseline, so the MS is physically working at that retention time.

I thought that maybe the collision energy is not enough, and I increased it to 60 eV (the maximum), but I still cannot see the transition. If I cannot see it at 60 eV, I assume that increasing the pressure of the collision gas won't help. I have never had this problem so far and I am not sure what else I can do.

Has someone experienced the same problem? Any tip would be highly appreciated.

Thank you very much!

Best regards,
Joana Pico

[James_Ball]

Possibly try a lower collision energy. The fragment may be to fragile to remain even at 45eV

[mathieu_stability]

alternatively, take the data file and process on an independent PC/MH setup.
Over the years, I have noted MassHunter can be problematic esp. with GCMS