Apparatus for ion desolvation in FAIMS
Ion separation in a FAIMS analyzer is affected by the presence of neutral species and solvent vapor. A diffuser element, which is fabricated from a porous material, is disposed within a curtain gas chamber adjacent to the FAIMS ion inlet, such that a flow of a curtain gas is blocked from flowing directly out through a curtain gas orifice. The porous material creates a pressure drop across the diffuser and results in the flow of curtain gas being provided out of the curtain gas orifice, along a direction that is approximately perpendicular to a plane containing the curtain gas orifice. The perpendicular gas flow opposes ions traveling toward the curtain gas orifice from an ionization source, thereby desolvating the ions. Providing a perpendicular curtain gas flow for desolvating ions reduces the ion losses that are normally associated with the curtain gas flow deflecting some of the ions away from the curtain gas orifice and toward a curtain plate electrode.
1. An apparatus for separating ions, comprising:
a first electrode having a first orifice defined therethrough;
a FAIMS analyzer comprising a second electrode having a second orifice defined therethrough, the second orifice spaced-apart from and approximately aligned with the first orifice when the apparatus is in an assembled condition;
a curtain gas chamber defined by a space between the first electrode and the second electrode and being dimensioned larger than a size of either one of the first orifice and the second orifice, the curtain gas chamber including a third orifice for providing a flow of a gas from a gas source into the curtain gas chamber; and,
a diffuser comprising a porous material and having a length, the diffuser including a passageway extending along the length between a first end of the diffuser and an opposite second end of the diffuser, the passageway being open at the first end and at the second end, the diffuser being disposed within the curtain gas chamber between the third orifice and each of the first and second orifices, and such that both of the first orifice and the second orifice are aligned with the passageway through the diffuser.
2. An apparatus according to claim 1 , wherein a cross-sectional area of the passageway taken along a plane perpendicular to the length is dimensioned to be larger than a size of either one of the first orifice and the second orifice.
3. An apparatus according to claim 2 , wherein the diffuser substantially blocks a shortest gas flow-path between the third orifice and each of the first and second orifices.
4. An apparatus according to claim 3 wherein the porous material of the diffuser provides a plurality of gas flow-paths through the diffuser.
5. An apparatus according to claim 3 , wherein the porous material is a ceramic material.
6. An apparatus according to claim 3 , wherein the porous material is a metallic mesh.
7. An apparatus according to claim 3 , wherein the porous material is a polymeric material.
8. An apparatus according to claim 4 , wherein the diffuser is generally cylindrical and has an outer periphery defining an outer surface and an inner periphery defining the passageway.
9. An apparatus according to claim 8 , wherein the porous material has a substantially uniform thickness between the outer periphery and the inner periphery.
10. An apparatus according to claim 9 , wherein the thickness of the porous material between the outer periphery and the inner periphery is small relative to a cross-sectional area of the passageway taken along a plane perpendicular to the length.
11. An apparatus for separating ions, comprising:
a FAIMS analyzer comprising a first electrode and a second electrode disposed in a spaced-apart relationship one relative to the other so as to define an analyzer region therebetween, the first electrode having an inlet orifice defined therethrough for providing fluid communication between the analyzer region and a region that is external to the analyzer region;
a curtain gas chamber disposed within the region that is external to the analyzer region and in fluid communication with the analyzer region via the inlet orifice, the curtain gas chamber including a curtain gas inlet for receiving a flow of a curtain gas from a curtain gas source, and including a curtain plate electrode having an outlet orifice defined therethrough; and,
a diffuser disposed within the curtain gas chamber between the first electrode and the curtain plate electrode, the diffuser comprising a porous material having a passageway defined therethrough and open at both ends such that the inlet orifice and the outlet orifice are in fluid communication one with the other via the passageway, and such that the curtain gas inlet is in fluid communication with each of the inlet orifice and the outlet orifice via a plurality of gas flow-paths defined through the porous material.
12. An apparatus according to claim 11 , wherein the porous material is a ceramic material.
13. An apparatus according to claim 11 , wherein the porous material is a metallic mesh.
14. An apparatus according to claim 11 , wherein the porous material is a polymeric material.
15. An apparatus according to claim 11 , wherein the diffuser is generally cylindrical and having an outer periphery defining an outer surface and an inner periphery defining the passageway.
16. An apparatus according to claim 15 , wherein, the porous material has a substantially uniform thickness between the outer periphery and the inner periphery.
17. An apparatus for separating ions, comprising:
a FAIMS analyzer comprising a first electrode and a second electrode disposed in a spaced-apart relationship one relative to the other so as to define an analyzer region therebetween, the first electrode having an inlet orifice defined therethrough for providing fluid communication between the analyzer region and a region that is external to the analyzer region;
a curtain gas chamber disposed adjacent to the inlet orifice, the curtain gas chamber including a curtain gas inlet for receiving a flow of a curtain gas from a curtain gas source and a curtain gas outlet for providing a flow of the curtain gas; and,
means for restricting gas flow between the curtain gas inlet and the curtain gas outlet such that the flow of curtain gas out of the curtain gas outlet is provided along a direction substantially perpendicular to a plane containing the curtain gas outlet.
18. An apparatus according to claim 17 , wherein the means for restricting gas flow comprises a diffuser comprising a porous material.
19. An apparatus according to claim 18 , wherein the porous material is a ceramic material.
20. An apparatus according to claim 18 , wherein the porous material is a metallic mesh.
21. An apparatus according to claim 18 , wherein the porous material is a polymeric material.
22. An apparatus according to claim 17 , wherein the means for restricting gas flow forms a substantially gas-tight seal about each one of the curtain gas outlet and the inlet orifice.
23. An apparatus according to claim 22 , wherein the means for restricting gas flow includes a passageway extending between opposite ends thereof, the passageway for providing fluid communication between the curtain gas outlet and the inlet orifice.
24. An apparatus according to claim 23 , wherein the means for restricting gas flow comprises a porous material disposed between the curtain gas inlet and the passageway, the porous material for supporting a generally symmetrical flow of the curtain gas from the curtain gas chamber inwardly toward the passageway.
25. An apparatus according to claim 17 , comprising an ionization source disposed in a spaced-apart arrangement with the curtain gas outlet and in fluid communication therewith for providing a flow of ions along a direction that is generally opposite the flow of curtain gas out of the curtain gas outlet.
26. A method of separating ions, comprising:
providing a FAIMS analyzer region that is in fluid communication with a curtain gas region via a first orifice;
providing an ionization source that is in fluid communication with the curtain gas region via a second orifice;
providing a flow of a curtain gas into the curtain gas region via a third orifice that is spaced-apart from each of the first orifice and the second orifice;
directing the flow of a curtain gas through a porous wall of a diffuser element that is disposed within the curtain gas region and into a passageway within the interior of the diffuser element so as to restrict the flow of a curtain gas between the third orifice and each one of the first orifice and the second orifice;
providing a flow of the curtain gas along the passageway and out through the second orifice along a direction that is substantially perpendicular to a plane containing the second orifice; and,
directing a flow of ions from the ionization source toward the second orifice so as to desolvate the ions in the flow of the curtain gas.