Energetics and efficiencies of collision-induced dissociation achieved during the mass acquisition scan in a quadrupole ion trap

Using n-butylbenzene as a test molecule, evidence is provided that fast, efficient or highly energetic collision-induced dissociation (CID) can be achieved during the mass acquisition ramp of a commercially available quadrupole ion trap (QIT) mass spectrometer. The method of excitation is very similar to axial modulation for mass range extension except that lower amplitude waveforms are used to excite the precursor ions within the trap instead of ejecting them from the trap. ITSIM simulations verify that fast kinetic excitation followed by kinetic-to-internal energy transfer occurs on the rapid time-scale required for the recapture and mass analysis of product ions during the mass acquisition ramp. CID efficiencies larger than 50% can be obtained using this new approach and ratios of Th 91/92 of n-butylbenzene fragment ions as large as 9 are possible, albeit at significantly reduced efficiencies. These very large ratios indicate an internal energy above 7eV for the precursor ions indicating that fragmentation of larger ions could also be possible using this new approach. The main benefits of the new method are that no extra time is required for fragmentation or cooling and that on-resonance conditions are guaranteed because the ions’ secular frequencies are swept through the fixed frequency of excitation. Also presented are the effects of experimental variables such as excitation frequency, excitation amplitude and scan rate on the CID efficiencies