Do collisions inside the collision cell play a relevant role in CID-LIFT experiments?

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Physical Chemistry

Background:

• Collision-induced dissociation is crucial for characterizing ions from matrix-assisted laser desorption ionization (MALDI).
• Time-of-flight (TOF) mass analyzers offer Postsource Decay (PSD), LIFT, and MALDI-TOF/TOF for collision experiments.
• LIFT and MALDI-TOF/TOF overcome PSD mass calibration issues for product ion spectra.

Purpose of the Study:

• To investigate the internal energy uptake of ions generated by MALDI.
• To compare fragmentation patterns from LIFT experiments with other collision methods.
• To elucidate the mechanism of internal energy acquisition in the MALDI plume.

Main Methods:

• Performed LIFT (Laser-Induced Fragmentation Transfer) experiments on peptides.
• Varied collision gas presence and plume density during LIFT experiments.
• Compared LIFT data with "in-source" collision-induced dissociation of ESI-generated ions and triple-quadrupole experiments.

Main Results:

• LIFT spectra were nearly identical with or without collision gas, indicating high intrinsic internal energy.
• Fragmentation primarily occurred due to energy acquired in the expanding MALDI plume via multiple collisions.
• MALDI ion energy uptake was comparable to 40-eV argon collisions in a triple-quadrupole instrument.

Conclusions:

• MALDI ions possess substantial internal energy before targeted fragmentation.
• The expanding MALDI plume is the primary site for energy uptake through multiple collisions.
• LIFT and other collision methods provide comparable insights into ion fragmentation dynamics.