title: Production and fragmentation of multiply charged ions in 'electron-free' matrix-assisted laser desorption/ionization.
abstract: An unusually large fraction of multiply charged ions is observed in 'electron-free' matrix-assisted laser desorption/ionization (MALDI). Here we investigate how the yield of multiply charged ions depends on experimental parameters in MALDI. It is found to increase if measures are taken to limit the number of electrons in the plume, for example, by using non-metallic MALDI targets or low laser pulse energies. The ionization energy of the matrix is another important parameter that affects the yield of multiply charged ions: matrices with high ionization energies lead to greater intensities of multiply charged ions. It is furthermore proposed that some of the fragment ions observed in MALDI are due to reactions of analyte with electrons in the plume. The possibility of electron capture dissociation of multiply charged ions produced by MALDI is shown.
authors.affiliation: Department of Chemistry, Swiss Federal Institute of Technology, ETH Hönggerberg, CH-8093 Zürich, Switzerland.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Frankevich
authors.forename: Juan
authors.initials: J
authors.lastname: Zhang
authors.forename: Maxim
authors.initials: M
authors.lastname: Dashtiev
authors.forename: Renato
authors.initials: R
authors.lastname: Zenobi
mesh_terms: D000818:Animals; D001920:Bradykinin / Q000737:chemistry; D002417:Cattle; D004583:Electrons; D006801:Humans; D007259:Infrared Rays; D007328:Insulin / Q000737:chemistry; D007477:Ions / Q000737:chemistry*; D007834:Lasers; D008555:Melitten / Q000737:chemistry; D008956:Models, Chemical; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014466:Ultraviolet Rays
chemical_list: D007328:Insulin; D007477:Ions; D008555:Melitten; D001920:Bradykinin