Patent ID: 7161143

Claim:
A method of separating charged particles or ions in a differential mobility analyzer having a diffuser downstream of an analyzing region, wherein a stream of charged particles or ions of various electrical mobilities is introduced into an upstream portion of the analyzing region through an inlet and wherein an electrical field is provided in the analyzing region by a combination of electrodes and/or grids charged to various voltages and at least one charging device is provided to maintain the electrodes and grids at the various voltages, and wherein a combination of a laminar flow field and the electrical field leads to ions of different mobilities separating in space, said method comprising the steps of: (a) introducing the stream of charged particles or ions into said analyzing region; (b) laminarizing a flow of an ion-free sheath gas, and introducing said sheath gas into said differential mobility analyzer immediately upstream of said analyzing region; and (c) sampling or collecting said separated particles or ions within a narrow range of electrical mobilities through at least one sampling or collector device, the last of which defines the exit of said analyzing region, wherein flow resistance of the ion-free sheath gas through the differential mobility analyzer is minimized by the diffuser.