Abstract. 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.
Coupling of a High-Resolution Ambient Pressure Drift Tube Ion Mobility Spectrometer to a Commercial Time-of-flight Mass Spectrometer
