A method and apparatus enabling increased sensitivity in
ion mobility spectrometry /
mass spectrometry instruments which substantially reduces or eliminates the loss of ions in
ion mobility
spectrometer drift tubes utilizing a device for transmitting ions from an
ion source which allows the transmission of ions without significant
delay to an
hourglass electrodynamic ion funnel at the entrance to the
drift tube and / or an internal ion funnel at the exit of the
drift tube. An
hourglass electrodynamic funnel is formed of at least an entry element, a center element, and an exit element, wherein the aperture of the center element is smaller than the aperture of the entry element and the aperture of the exit elements. Ions generated in a relatively
high pressure region by an
ion source at the exterior of the
hourglass electrodynamic funnel are transmitted to a relatively low pressure region at the entrance of the hourglass funnel through a conductance limiting orifice. Alternating and direct electrical potentials are applied to the elements of the hourglass electrodynamic funnel thereby drawing ions into and through the hourglass electrodynamic funnel thereby introducing relatively large quantities of ions into the
drift tube while maintaining the
gas pressure and composition at the interior of the drift tube as distinct from those at the entrance of the electrodynamic funnel and allowing a positive
gas pressure to be maintained within the drift tube, if desired. An internal ion funnel is provided within the drift tube and is positioned at the exit of said drift tube. The
advantage of the internal ion funnel is that ions that are dispersed away from the exit aperture within the drift tube, such as those that are typically lost in conventional drift tubes to any subsequent analysis or measurement, are instead directed through the exit of the drift tube, vastly increasing the amount of ions exiting the drift tube.