Massive cluster impact ionization on a four sector tandem mass spectrometer

Abstract

High energy glycerol cluster ions from an electrohydrodynamic ion gun have been used as a primary ion beam to generate secondary ions of proteins with molecular weights up to 29 kDa and oligonucleotides. The technique not only demonstrated good performance in the picomole/nanomole range for the desorbtion of highly polar and fragile molecules such as proteins and deoxyoligonucleotide, but it also allowed the observation of a non-covalent complex in the form of a deoxyoligonucleotide duplex. We have also shown that it is feasible to carry out 5tructural analysis of oligonucleotides by collisional activation in a four sector tandem instrument.

Fundamental aspects of electrospray droplet impact/SIMS

“…The ionic components of the selvedge are considered to be derived mostly from precharged species, as it has been calculated that the energy per nucleon is too low to account for both desorption and ionization. 18,25 Interestingly, however, positive ions for polyaromatic hydrocarbons (e.g. coronene, chrysene, etc.)…”

“…After the shock wave retreats from the interface, the newly ionized ions desorb from the interface with the aid of phonon excitation at the interface region. Since only a few monolayers of the solid samples are desorbed by such collisional phenomena, 18,25 enormous high energy density is localized at the colliding interface. Since the coherent phonon excitation is an irreversible instant energy accumulation process, which followed by the ionization and desorption, EDI may be regarded as a new type of matrix-free SIMS.…”

Impact desolvation of electrosprayed microdroplets – a new ionization method for mass spectrometry of large biomolecules

“…In contrast to the peptides, molecular ion signals from oligonucleotide analytes were very weak or undetectable in MCI mass spectra in this device, although an MCI mass spectrum of small oligonucleotides has been reported earlier on a magnetic sector instrument. 6 Possibly, oligonucleotide species in glycerol solution are excluded from the liquid surface due to the presence of small amounts of surfactant impurities in the solution.…”

“…Different impact targets could be introduced through a vacuum interlock that was included in the design to allow sample introduction for analysis by massive cluster impact (MCI). 3,5,6 The target used here was made from stainless steel; its surface was flat and polished, but no special effort was made to make this surface very smooth. For IDEM experiments, the surface of the target was rinsed with methanol before insertion into the target chamber.…”

“…The desorption mechanism of MCI is believed to involve shock-heating events which vaporize both the clusters and a small volume of the target surface to produce desolvated gas-phase molecular ions of analytes. 4 For vacuum compatibility, MCI requires either dried targets 5 or samples dissolved in involatile solvents such as liquid glycerol, 3,6 and so cannot sample ions directly from the aqueous solutions most often encountered in biochemical analysis. In contrast, IDEM allows direct sampling of biomolecular analytes from aqueous solutions.…”