Method and apparatus to increase the resolution and widen the range of differential mobility analyzers (DMAs)
OwnerJuan Fernandez De la Mora, Michael J. Labowskyinventors
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Abstract
A differential mobility analyzer (DMA) for separating charged particles or ions suspended in a gas and a method of using the DMA for separating such particles. The invention includes various means for increasing the resolution of the DMA by stabilizing the laminar flow within the DMA and by allowing unusually large flow velocities.
Claims38
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) maintaining the flow of said sheath gas within said analyzing region as laminar flow;
- (d) 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;
- and
- (e) 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.
A differential mobility analyzer for separating ions and charged particles suspended in a mixture comprising:
- means to provide a laminar flow of ion-free sheath gas into an upstream end of an analyzing region at a Reynolds number in excess of 2000;
- ion supply means for introducing said ions and charged particles into said analyzing region;
- at least two electrodes charged to suitable potentials to create an electric field within said analyzing region;
- whereby said ions are separated in space by combined action of the electric field and the flow of sheath gas;
- at least one sampling or collecting device, wherein ions of a desired mobility are sampled or collected;
- power supply means to charge said at least two electrodes to said potentials;
- means for maintaining said laminar flow within said analyzing region;
- and
- means to maintain flow spatial symmetry in the analyzing region while minimizing pressure drop.
The differential mobility analyzer as recited in 18, wherein a downstream end of the means to provide a laminar flow of ion-free sheath gas into the upstream end of the analyzing region is converging until it meets said inlet slit or orifice (4).
Dependencies are inferred from the claim text.