Development of a Modular, Open-Source, Reduced-Pressure, Drift Tube Ion Mobility Spectrometer

Toward the goal of minimizing construction costs while
maintaining
high performance, a new, reduced-pressure, drift tube ion mobility
system is coupled with an ion trap mass analyzer through a custom
ion shuttle. The availability of reduced-pressure ion mobility systems
remains limited due to comparatively expensive commercial options
and limited shared design features in the open literature. This report
details the complete design and benchmarking characteristics of a
reduced-pressure ion mobility system. The system is constructed from
FR4 PCB electrodes and encased in a PTFE vacuum enclosure with custom
torque-tightened couplers to utilize standard KF40 bulkheads. The
PTFE enclosure directly minimizes the overall system expenses, and
the implementation of threaded brass inserts allows for facile attachments
to the vacuum enclosure without damaging the thermoplastic housing.
Front and rear ion funnels maximize ion transmission and help mitigate
the effects of radial ion diffusion. A custom planar ion shuttle transports
ions from the exit of the rear ion funnel into the ion optics of an
ion trap mass analyzer. The planar ion shuttle can couple the IM system
to any contemporary Thermo Scientific ion trap mass analyzer. Signal
stability and ion intensity remain unchanging following the implementation
of the planar ion shuttle when compared to the original stacked ring
ion guide. The constructed IM system showed resolving powers up to
85 for various small molecules and proteins using the Fourier transform
from a ∼1 m drift tube. Recorded mobilities derived from first
principles agree with published literature results with an average
error of 1.1% and an average error toward literature values using
single field calibration of <1.3%.