Field Switching Combined with Bradbury–Nielsen
Gate for Ion Mobility Spectrometry
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Abstract
Bradbury–Nielsen gate (BNG)
is commonly used in ion mobility
spectrometers. It, however, transmits only a small fraction of the
ions into the drift region, typically 1%. In contrast, all ions in
the ionization chamber could be efficiently compressed into the drift
region by the field switching gate (FSG). We report in this paper
on the simultaneous use of BNG and field switching (FS) to enhance
ion utilization of the BNG. In this technique, the FS collects the
ions existing in the region between the FS electrode and the BNG and
drives them quickly, going through the BNG in the period of gate opening.
The BNG acts as the retarding field in the reported FSG to stop ions
from diffusing into the drift region in the period of gate closing.
Using this technique, an increase of at least 10-fold in the ion peak
height without any loss of resolution is achieved for acetone compared
with the BNG-only approach at a gate pulse width of 150 μs,
and an even larger improvement factor of 21 is achieved for heavier
DMMP dimer ions. This technique can be adapted to the current BNG-based
ion mobility instruments to significantly enhance their sensitivity
without any modification of the drift tube hardware