Instrumentation of Kinetic Energy-Resolved Surface-Induced Dissociation in Fourier Transform Mass Spectrometry

Abstract

A Bruker 7 T Fourier transform (FT) mass spectrometer fitted with electron impact (EI) and electrospray ionization (ESI) external ion sources has been modified for surface-induced dissociation (SID) studies utilizing a self-assembled monolayer (SAM) of CF3(CF2)9C2H4SH alkanethiolate chemisorbed on gold. Operational aspects of ion sources, intermediate hexapole ion storage, time-of-flight function of the ion optics and cell trapping mechanisms are discussed for both primary and secondary ions. Different methods of ion trapping in the FT ion cyclotron resonance cell were analyzed theoretically and dynamic voltage trapping (DVT) was chosen as the most suitable. Direct measurements of primary (short time scale) and secondary (delayed) SID fragmentation and kinetic energy distributions of the SID fragments illustrate the capabilities of the instrument as a research tool for investigating SID kinetics. SID of small molecules and model peptides was investigated over a moderate collision energy range and the ion population was sampled at various decomposition delay times. Kinetic energy distributions of SID fragment ions were measured and shown to be quite low over the range of energies investigated. Most of the primary ion kinetic energy is dissipated into surface excitation and internal energy of ions recoiled from the surface.