Improving Ion Mobility Measurement Sensitivity by
Utilizing Helium in an Ion Funnel Trap
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Abstract
Ion mobility instruments that utilize
nitrogen as buffer gas are
often preceded by an ion trap and accumulation region that also uses
nitrogen, and for different inert gases, no significant effects upon
performance are expected for ion mobility spectrometry (IMS) of larger
ions. However, we have observed significantly improved performance
for an ion funnel trap upon adding helium; the signal intensities
for higher <i>m</i>/<i>z</i> species were improved
by more than an order of magnitude compared to using pure nitrogen.
The effect of helium upon IMS resolving power was also studied by
introducing a He/N<sub>2</sub> gas mixture into the drift cell, and
in some cases, a slight improvement was observed compared to pure
N<sub>2</sub>. The improvement in signal can be largely attributed
to faster and more efficient ion ejection into the drift tube from
the ion funnel trap