Aston Labs

Mass-selected polyatomic cations and anions, produced by electrosonic spray ionization (ESSI), were deposited onto polycrystalline Au and fluorinated self-assembled monolayer (FSAM) surfaces by soft landing (SL) using a rectilinear ion trap (RIT) mass spectrometer. Protonated and deprotonated molecules, as well as intact cations and anions generated from various categories of molecules such as peptides, inorganic catalysts, and fluorescent dyes, were soft-landed onto the surfaces.

A waveform isolation method for transmitting ion of arbitrarily selected mass-to-charge ratios through quadrupole mass filters is described. Waveforms of appropriate frequencies are applied to cause mass-selective instability of ions of particular mass-to-charge ratios.

A new ion soft landing instrument has been built for the controlled deposition of mass selected polyatomic ions. The instrument has been operated with an electrospray ionization source; its major components are an electrodynamic ion funnel to reduce ion loss, a 90-degree bent square quadrupole that prevents deposition of fast neutral molecules onto the landing surface, and a novel rectilinear ion trap (RIT) mass analyzer. The ion trap is elongated (inner dimensions: 8 mm × 10 mm × 10 cm). Three methods of mass analysis have been implemented.

Soft-landing of singly and doubly protonated peptide ions onto three self-assembled monolayer surfaces (SAMs) was performed using a novel ion deposition instrument constructed in our laboratory and a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) specially designed for studying collisions of large ions with surfaces. Modified surfaces were analyzed using in situ 2 keV Cs⁺ secondary ion mass spectrometry or ex situ 15 keV Ga⁺ time-of-flight-secondary ion mass spectrometry (ToF-SIMS).