The multiphoton ionization and fragmentation pathway of furan at 450nm is analyzed on the basis of statistical theory and Ladder-Switching model. Our calculation indicates that fragmentation takes plase after furan mo...The multiphoton ionization and fragmentation pathway of furan at 450nm is analyzed on the basis of statistical theory and Ladder-Switching model. Our calculation indicates that fragmentation takes plase after furan molecules absorb six photons of 450nm, C+ begins to appear after absorption of nine photons, production of C2+ ions needs absorption of at least 15 photons. Our interesting result is that C+ ions is produced by dissociation of C3H+, CH2+ and C3+ ions, not of C2+ ions. Theoretically computed relative abundance of C+/C2+ after absorption 15 photons agrees well with our experimental results.展开更多
Protonation and alkali-metal cation adduction are the most important ionization processes in soft-ionization mass spectrometry.Studies on the fragmentation mechanism of protonated and alkali-metal-cationized compounds...Protonation and alkali-metal cation adduction are the most important ionization processes in soft-ionization mass spectrometry.Studies on the fragmentation mechanism of protonated and alkali-metal-cationized compounds in tandem mass spectrometry are essential and helpful for structural analysis.In some cases,it was often observed that a compound attached by different alkali-metal cations(or proton)exhibits similar fragmentation patterns but the relative abundances of product ions are different.This difference was considered to derive from the different electrostatic interactions of alkali-metal cations(or the bonded effect of proton)with the analyte.The alkali-metal cation with a smaller ionic radius shows stronger electrostatic interaction with the molecule because of its higher charge density.In addition,the bonded effect of the proton is stronger than the electrostatic interaction of the alkali-metal cation.In the present study,which used McLafferty-type rearrangements of even-electron ions([M+Cat]+,Cat=H,Li,Na,K)as model reactions,the effect of cation size in mass spectrometric fragmentation reactions is highlighted.These considerations were also successfully applied to interpret the similar but distinct fragmentation behavior of proton and alkali-metal cation adducts of a synthetic compound(2-(acetamido(phenyl)methyl)-3-oxobutanoate)and a drug(entecavir).展开更多
文摘The multiphoton ionization and fragmentation pathway of furan at 450nm is analyzed on the basis of statistical theory and Ladder-Switching model. Our calculation indicates that fragmentation takes plase after furan molecules absorb six photons of 450nm, C+ begins to appear after absorption of nine photons, production of C2+ ions needs absorption of at least 15 photons. Our interesting result is that C+ ions is produced by dissociation of C3H+, CH2+ and C3+ ions, not of C2+ ions. Theoretically computed relative abundance of C+/C2+ after absorption 15 photons agrees well with our experimental results.
基金financially supported by the National Natural Science Foundation of China(21025207,21372199)
文摘Protonation and alkali-metal cation adduction are the most important ionization processes in soft-ionization mass spectrometry.Studies on the fragmentation mechanism of protonated and alkali-metal-cationized compounds in tandem mass spectrometry are essential and helpful for structural analysis.In some cases,it was often observed that a compound attached by different alkali-metal cations(or proton)exhibits similar fragmentation patterns but the relative abundances of product ions are different.This difference was considered to derive from the different electrostatic interactions of alkali-metal cations(or the bonded effect of proton)with the analyte.The alkali-metal cation with a smaller ionic radius shows stronger electrostatic interaction with the molecule because of its higher charge density.In addition,the bonded effect of the proton is stronger than the electrostatic interaction of the alkali-metal cation.In the present study,which used McLafferty-type rearrangements of even-electron ions([M+Cat]+,Cat=H,Li,Na,K)as model reactions,the effect of cation size in mass spectrometric fragmentation reactions is highlighted.These considerations were also successfully applied to interpret the similar but distinct fragmentation behavior of proton and alkali-metal cation adducts of a synthetic compound(2-(acetamido(phenyl)methyl)-3-oxobutanoate)and a drug(entecavir).
