Atmospheric Measurement Techniques (Oct 2019)

Characterisation of the transfer of cluster ions through an atmospheric pressure interface time-of-flight mass spectrometer with hexapole ion guides

  • M. Leiminger,
  • M. Leiminger,
  • S. Feil,
  • P. Mutschlechner,
  • A. Ylisirniö,
  • D. Gunsch,
  • L. Fischer,
  • A. Jordan,
  • S. Schobesberger,
  • A. Hansel,
  • A. Hansel,
  • G. Steiner,
  • G. Steiner

DOI
https://doi.org/10.5194/amt-12-5231-2019
Journal volume & issue
Vol. 12
pp. 5231 – 5246

Abstract

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Here we present an alternative approach of an atmospheric pressure interface (APi) time-of-flight mass spectrometer for the study of atmospheric ions and cluster ions, the so-called ioniAPi-TOF. The novelty is the use of two hexapoles as ion guides within the APi. In our case, hexapoles can accept and transmit a broad mass range enabling the study of small precursor ions and heavy cluster ions at the same time. Weakly bound cluster ions can easily de-cluster during ion transfer depending on the voltages applied to the ion transfer optics. With the example system of H3O+(H2O)n=0-3, we estimate that cluster ions with higher binding energies than 17 kcal mol−1 can be transferred through the APi without significant fragmentation, which is considerably lower than about 25 kcal mol−1 estimated from the literature for APi-TOFs with quadrupole ion guides. In contrast to the low-fragmenting ion transfer, the hexapoles can be set to a high-fragmenting declustering mode for collision-induced dissociation (CID) experiments as well. The ion transmission efficiency over a broad mass range was determined to be on the order of 1 %, which is comparable to existing instrumentation. From measurements under well-controlled conditions during the CLOUD experiment, we demonstrate the instrument's performance and present results from an inter-comparison with a quadrupole-based APi-TOF.