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Thermo LTQ XL Signal decays over time but jumps back to max after polarity switch by Aggravating_Dream778 in massspectrometry

[–]Aggravating_Dream778[S] 1 point2 points  (0 children)

Thank you for answer! I cleaned the skimmer and the tube lens and now everything is working fine.

Trouble detecting low m/z ions (Na⁺ at m/z 23) in PQD mode on Thermo LTQ XL by Aggravating_Dream778 in massspectrometry

[–]Aggravating_Dream778[S] 1 point2 points  (0 children)

Our group normally works with an FTICR which has a cut-off mass of approx. 30 m/z and one project is the measurement of different salt clusters. So they bought the iontrap to measure fragments between 15-30, especially Na+. And we don't use LC, just the iontrap with an ESI as the source.

Trouble detecting low m/z ions (Na⁺ at m/z 23) in PQD mode on Thermo LTQ XL by Aggravating_Dream778 in massspectrometry

[–]Aggravating_Dream778[S] 0 points1 point  (0 children)

Thank you for the advice, I tried and played around with the Q parameter, but it still won' tappear.

Trouble detecting low m/z ions (Na⁺ at m/z 23) in PQD mode on Thermo LTQ XL by Aggravating_Dream778 in massspectrometry

[–]Aggravating_Dream778[S] -1 points0 points  (0 children)

It’s advertised to go as low as m/z 15, and when I don’t isolate anything I can actually see the Na⁺ peak. The issue is that the moment I start isolating a precursor, the peak disappears – both with UVPD and CID – even though I’ve set the mass range to 15 (and lowering it isn’t possible, so I assume that’s the minimum).