Ion mobility spectrometer
An ion mobility spectrometer is described having an ion filter in the form of at least one ion channel having a plurality of electrodes. A time-varying electric potential applied to the conductive layers allows the filler to selectively admit ion species. The electric potential has a drive and a transverse component, and in preferred embodiments each of the electrodes is involved in generating a component of both the drive and transverse fields. The device may be used without a drift gas flow. Microfabrication techniques are described for producing microscale spectrometers, as are various uses of the spectrometer.
1. A field asymmetric ion mobility spectrometer comprising:
at least one ion channel;
a plurality of electrodes disposed proximate the ion channel; and
electrode control means for controlling the electrodes such that a first drive electric field is generated along the length of the ion channel, and a second transverse electric field is simultaneously generated orthogonal to the first, and wherein each of said plurality of electrodes is involved in simultaneously generating a component of both the drive and transverse electric fields.
2. The spectrometer of claim 1 , wherein the drive electric field is a static electric field.
3. The spectrometer of claim 1 , wherein the transverse electric field varies over time.
4. The spectrometer of claim 3 , wherein the transverse electric field comprises an AC component and a DC component.
5. The spectrometer of claim 1 , wherein the electrodes are disposed adjacent the entrance and exit to the ion channel.
6. The spectrometer of claim 1 , wherein at least two electrode pairs are provided.
7. The spectrometer of claim 1 , further including an ion filter having a plurality of ion channels.
8. The spectrometer of claim 7 , wherein the ion channels are defined by a plurality of electrode fingers forming a comb-like arrangement.
9. The spectrometer of claim 7 , wherein the filter comprises two or more interdigitated electrode arrays, each array having a plurality of electrode fingers.
10. The spectrometer of claim 7 , wherein the filter has a generally wafer-like form.
11. The spectrometer of claim 7 , wherein the spectrometer comprises a plurality of functional layers, each layer having a wafer-like form.
12. The spectrometer of claim 1 , further comprising one or more of an inlet layer, a dehumidifier layer, and a preconcentrator layer.
13. The spectrometer of claim 1 , further comprising a semipermeable membrane.
14. The spectrometer of claim 13 wherein the membrane comprises a heating element.
15. The spectrometer of claim 13 wherein the membrane is in the form of an inlet tube.
16. The spectrometer of claim 1 comprising at least one ion filter.
17. The spectrometer of claim 1 comprising at least one ion detector.
18. The spectrometer of claim 1 further comprising means for generating a gas flow through the spectrometer.
19. The spectrometer of claim 18 wherein the gas flow is a counterflow against the direction of movement of ions.
20. A method for performing ion mobility spectrometry comprising:
passing ions through at least one ion channel having a conductive layer and a plurality of electrodes;
controlling each of the plurality of electrodes such that a first drive electric field is generated along the length of the at least one ion channel, and a second transverse electric field is simultaneously generated orthogonal to the first, and
simultaneously generating a component of both the drive and transverse electric fields involving each of said plurality of electrodes.