Ion transfer arrangement with spatially alternating DC and viscous ion flow

• US 8,148,680 B2
• Filed: 11/07/2007
• Issued: 04/03/2012
• Est. Priority Date: 11/07/2006
• Status: Active Grant

• Current Assignee: Thermo Fisher Scientific (Bremen) GmbH (Thermo Fisher Scientific Incorporated)
• Original Assignee: Thermo Fisher Scientific (Bremen) GmbH (Thermo Fisher Scientific Incorporated)
• Inventors: Makarov, Alexander, Pesch, Reinhold, Malek, Robert, Kozlovskiy, Viacheslav
• Primary Examiner(s): Wells, Nikita
• Application Number:
  US12/513,954
• Publication Number:
  US 20100038533A1
• Time in Patent Office: 1,609 Days
• Field of Search: 250/283, 250/289, 250/288, 250/293, 250/297, 250/396.R, 313/360.1, 313/7
• US Class Current: 250/283
• CPC Class Codes: H01J 3/14 Arrangements for focusing or reflecting ray or beam H01J3/02, H01J3/04 take precedence
• CPC Class Codes: H01J 49/062 Ion guides linear ion traps performing mass selection H01J49/4225, mass filters H01J49/421

Abstract

A method of transporting gas and entrained ions between higher and lower pressure regions of a mass spectrometer comprises providing an ion transfer conduit 60 between the higher and lower pressure regions. The ion transfer conduit 60 includes an electrode assembly 300 which defines an ion transfer channel. The electrode assembly 300 has a first set of ring electrodes 305 of a first width D1, and a second set of ring electrodes of a second width D2 (≧D1) and interleaved with the first ring electrodes 305. A DC voltage of magnitude V₁ and a first polarity is supplied to the first ring electrodes 205 and a DC voltage of magnitude V₂ which may be less than or equal to the magnitude of V₁ but with an opposed polarity is applied to the second ring electrodes 310. The pressure of the ion transfer conduit 60 is controlled so as to maintain viscous flow of gas and ions within the ion transfer channel.

Claims

1. A method of transporting gas and entrained ions between a first, relatively high pressure region and a second, relatively low pressure region, comprising the steps of:

providing, between the high and low pressure regions, an ion transfer conduit including an electrode assembly which defines an ion transfer channel through which the gas and entrained ions pass, and which has a first set of electrodes of a first width D1 in the longitudinal direction of the ion transfer conduit, and a second set of electrodes of a second width D2 (≧

D1) in the longitudinal direction and interleaved with the first set of electrodes;

supplying a DC voltage of magnitude V₁ and a first polarity to the first set of electrodes and a DC voltage of magnitude V₂ (|V₂|≦

|V₁|) and a second, opposite polarity relative to the average voltage distribution in the longitudinal direction of the electrode assembly, to the second set of electrodes; and

controlling the pressure of the ion transfer conduit so as to maintain viscous flow of gas and ions within the ion transfer channel.

2. The method of claim 1, wherein the step of controlling the pressure of the ion transfer conduit comprises pumping a region surrounding the ion transfer channel so as to maintain the pressure in the ion transfer channel between atmosphere and about 1 mbar.

3. The method of claim 1, wherein the ion transfer conduit defines an ion transfer channel which is no more than about 1 meter in length, and no more than 1 cm in diameter.

4. The method of claim 1, further comprising arranging the average separation of an electrode of the first set of electrodes from an adjacent electrode of the second set of electrodes to be greater than the mean free path of ions within the ion transfer channel.

5. The method of claim 1, further comprising the step of heating the ion transfer channel so as to promote evaporation of residual liquid solvent within the ion transfer channel.

6. The method of claim 1, further comprising locating the ion transfer conduit at least partly within an evacuable chamber.

7. The method of claim 6, wherein the ion transfer conduit is located entirely within an evacuable chamber, the method further comprising evacuating the evacuable chamber in which the conduit is located, to a pressure which is below atmospheric pressure.

8. The method of claim 6, further comprising back filling the evacuable chamber with a back filling gas.

9. The method of claim 6, further comprising locating a tube with a sidewall having a plurality of apertures radially outwardly of the DC electrode structure.

10. The method of claim 9, further comprising pumping a region outside of the tube so as to draw gas through the plurality of apertures.

11. The method of claim 1, further comprising focusing ions from the relatively high pressure region into the ion transfer conduit, using one of an aerodynamic or electric lens.

12. The method of claim 1, wherein the first and second sets of electrodes comprise ring electrodes.

13. The method of claim 1, further comprising enclosing the ion transfer conduit within a gas tight enclosure, and pumping the gas tight enclosure so as to reduce the pressure therein, so as to draw gas within the ion transfer channel through the passageways in the tube and into the gas tight enclosure.