A deflection system to reduce the interference from post-source decay product ions in photodissociation tandem time-of-flight mass spectrometry.

A deflection system consisting of four deflectors was designed and used to reduce the interference from post-source decay (PSD) product ions in photodissociation (PD) tandem time-of-flight (TOF) mass spectrometry. For simple protonated peptides generated by matrix-assisted laser desorption/ionization, the presence of PSD product ions at the laser irradiation spot was found to noticeably alter the minor peaks in the PD spectra even though the major ones were hardly affected. Other benefits from the use of the deflection system such as the improvement in the resolving power in PSD tandem mass spectra are discussed.