title: Minimum proton affinity for efficient ionization with atmospheric pressure desorption/ionization on silicon mass spectrometry.
abstract: We performed a systematic study using a set of compounds with different proton affinities (PAs) on the ionization in atmospheric pressure desorption/ionization on silicon mass spectrometry (AP-DIOS-MS). The compounds studied included various aromatic molecules of different sizes. The PAs of these compounds were calculated using ab initio and hybrid density functional theory calculations at the B3LYP/6-31G(d) level of theory. We observed that only compounds with relatively high PAs above a threshold value of 920-950 kJ/mol were efficiently ionized as protonated molecules under AP-DIOS conditions and produced very clean mass spectra.
authors.affiliation: Division of Pharmaceutical Chemistry, Department of Pharmacy, PO Box 56, FIN-00014 University of Helsinki, Helsinki, Finland.
authors.forename: Pekka
authors.initials: P
authors.lastname: Ostman
authors.forename: Jaana M H
authors.initials: JM
authors.lastname: Pakarinen
authors.forename: Pirjo
authors.initials: P
authors.lastname: Vainiotalo
authors.forename: Sami
authors.initials: S
authors.lastname: Franssila
authors.forename: Risto
authors.initials: R
authors.lastname: Kostiainen
authors.forename: Tapio
authors.initials: T
authors.lastname: Kotiaho
mesh_terms: D000327:Adsorption; D001274:Atmospheric Pressure; D003198:Computer Simulation; D007477:Ions; D008956:Models, Chemical; D008958:Models, Molecular; D011522:Protons; D012825:Silicon / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D007477:Ions; D011522:Protons; D012825:Silicon