Charge transfer in collisions between gaseous protein ions and inert gases

Charge transfer has been found to occur during collisions (at keV laboratory energies) between certain inert gases and certain gaseous protein and peptide ions, Protein and peptide ions were generated by matrix-assisted laser desorption/ionisation. Following collision, ions were analysed by time-of-flight mass spectrometry either directly or after transmission through an electric-sector energy filter, Charge transfer tended to occur when the centre-of-mass (COM) collision energy E(COM) Of the collision gas/analyte ion clearly exceeded the lowest ionisation energy of the collision gas, but not to occur if the collision energy were lower, With regard to high energy collisions in the context of tandem mass spectrometry, the conclusion drawn is that the heavier inert gases such as xenon and argon are more likely to neutralise a parent protein ion than is a light gas such as helium.