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. Analysis of the modified surfaces was performed in situ by Cs+ secondary ion mass spectrometry (SIMS) using the same RIT mass analyzer to characterize the sputtered ions as was used to mass select the primary ions for SL. Soft landing times as short as 30 seconds provided surfaces which yielded good quality SIMS spectra. Chemical reactions of the surfaces modified by SL were effected in an attached reaction chamber to and from which the surface was transferred under vacuum. For example, a surface on which protonated triethanolamine had been soft landed was silylated using vapor phase chlorotrimethylsilane, before being returned still under vacuum to the preparation chamber where SIMS analysis revealed the silyloxy functionalization. SL and vapor-phase reactions are complementary methods of surface modification and in situ surface analysis by SIMS is a simple way of characterizing the products produced by either technique.