Patent ID: 6787763
Filing Date: 2004-09-07
Classification: G01N,H01J

Abstract:
A method of separating charged particles or ions in a differential mobility analyzer, wherein a stream of charged particles or ions is introduced into an upstream portion of an analyzing region through an inlet slit or orifice and wherein a combination of a laminar flow field and an electrical field leads to ions of different mobilities separating in space, said method comprising the steps of:(a) introducing a stream of charged particles or ions of various electrical mobilities 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; (c) providing an electrical field in said analyzing region by a combination of electrodes and grids charged to various voltages and charging devices to maintain said electrodes and grids at said various voltages; (d) 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; and (e) minimizing flow resistance of the ion-free sheath as through the differential mobility analyzer by placing a diffuser downstream from the analyzing region.