js9b00095_si_001.pdf (177.14 kB)
A Novel Ion Pseudo-trapping Phenomenon within Traveling Wave Ion Guides
journal contribution
posted on 2020-03-05, 16:33 authored by Sugyan
M. Dixit, Keith Richardson, David Langridge, Kevin Giles, Brandon T. RuotoloThe
widespread use of traveling wave ion mobility (TWIM) technology
in fields such as omics and structural biology motivates efforts to
deepen our understanding of ion transport within such devices. Here,
we describe a new advancement in TWIM theory, where pseudo-trapping
within TW ion guides is characterized in detail. During pseudo-trapping,
ions with different mobilities can travel with the same mean velocity,
leaving others within the same TWIM experiment to separate as normal.
Furthermore, pseudo-trapping limits typical band broadening experienced
by ions during TWIM, manifesting as peaks with apparently improved
IM resolving power, but all ions that undergo pseudo trapping are
unable to separate by IM. SIMION simulations show that ions become
locked into a repeated pattern of motion with respect to the TW reference
frame during pseudo-trapping. We developed a simplified model capable
of reproducing TW pseudo-trapping and reproducing trends observed
in experimental data. Our model and simulations suggest that pseudo-trapping
occurs only during experiments performed under static TWIM conditions,
to an extent that depends on the detailed shape of the traveling wave.
We show that pseudo-trapping alters the ion transit times and can
adversely affect calibrated CCS measurements. Finally, we provide
recommendations for avoiding unintentional pseudo-trapping in TWIM
in order to obtain optimal separations and CCS determinations.