Mass filter having extended operational lifetime

Patent metadata

Field	Value
Publication number	US-10453667-B2
Application number	US-201615578053-A
Country	US
Kind code	B2
Filing date	May 31, 2016
Priority date	May 29, 2015
Publication date	Oct 22, 2019
Grant date	Oct 22, 2019

Abstract

A mass filter is disclosed having at least one electrode ( 42 - 48 ) comprising an aperture ( 43 ) or recess. Voltages are applied to the electrodes ( 42 - 48 ) of the mass filter such that ions having mass to charge ratios in a desired range are confined by the electrodes and are transmitted along and through the mass filter, whereas ions ( 47,49 ) having mass to charge ratios outside of said desired range are unstable and pass into the aperture ( 43 ) or recess such that they are filtered out by the mass filter. The aperture ( 43 ) or recess reduces or eliminates the number of ions that would otherwise impact the electrode surface facing the ion transmission axis and hence reduces degradation of the ion transmission properties of the mass filter.

First claim

The invention claimed is:

1. A method of mass filtering ions comprising:
mass filtering ions using a first mass filter so as to mass selectively transmit only ions having a first range of mass to charge ratios; and
mass filtering the ions transmitted by the first mass filter using a second mass filter, wherein the second mass filter only transmits ions having a second range of mass to charge ratios that is a sub-set of the first range of mass to charge ratios;
wherein at least one electrode of the first mass filter comprises an aperture extending entirely through the electrode and/or comprises a recess extending only partially through the electrode, wherein the aperture and/or recess:
is arranged and configured such that ions that are unstable in the first mass filter pass into or through the aperture and/or into the recess such that they are not transmitted by the first mass filter, and
increases in cross-sectional area in a direction away from the central axis of the first mass filter, such that the cross-sectional area of the aperture and/or recess increases in a tapered manner in a radially outward direction;

wherein the ions transmitted by the first mass filter are guided into the second mass filter using a RF-only ion guide arranged between the first mass filter and the second mass filter.

2. The method of claim 1 , wherein the first mass filter and/or second mass filter is a multipole mass filter, such as a quadrupole mass filter.

3. The method of claim 1 , comprising applying RF and DC voltages to electrodes of the first mass filter and/or to electrodes of the second mass filter so as to confine ions desired to be transmitted between the electrodes and to cause ions that are not desired to be transmitted to be unstable and not confined between the electrodes.

4. The method of claim 1 , comprising:
guiding the ions into the first mass filter using a second ion guide arranged upstream, optionally directly upstream, of the first mass filter; optionally wherein the second ion guide is an RF-only ion guide to which only RF potentials are applied and not DC potentials.

5. The method of claim 1 , wherein at least one of the electrodes of the second mass filter and/or at least one of the electrodes of a first ion guide comprises an aperture extending entirely through the electrode and/or comprises a recess extending only partially through the electrode, wherein the aperture and/or recess is arranged and configured such that ions that are unstable in the second mass filter or first ion guide pass into or through the aperture and/or into the recess such that they are not transmitted by the second mass filter or first ion guide.

6. The method of claim 1 , wherein the electrode having the aperture or recess is elongated in a direction along the length of the first mass filter, and wherein the aperture is a slotted aperture or the recess is a slotted recess.

7. The method of claim 1 , comprising arranging a conductive grid or mesh over, or in, the aperture or recess so as to support an electric field generated by the electrode.

8. The method of claim 1 , wherein ions that pass into or through the aperture or recess are not detected and are neutralised or discarded.

9. The method of claim 1 , wherein at least some of the electrodes of the first mass filter are heated.

10. The method of claim 1 , wherein at least one of the electrodes of the first mass filter and/or at least one of the electrodes of the second mass filter is axially segmented so as to comprise segments that are spaced apart along the longitudinal axis by one or more gaps such that ions that are unstable in the first mass filter pass into or through the gaps such that they are not transmitted by the first mass filter.

11. The method of claim 1 , wherein at least one electrode of the first mass filter comprises a longitudinal recess extending only partially through the electrode; and
wherein the recess is arranged and configured such that ions that are unstable in the first mass filter pass into the recess such that they are not transmitted by the first mass filter.

12. A method of mass filtering ions comprising:
supplying ions to a mass filter formed from a plurality of electrodes, wherein at least one of the electrodes comprises an aperture extending entirely through the electrode and/or comprises a recess extending only partially through the electrode, wherein the aperture and/or recess increases in cross-sectional area in a direction away from the central axis of the mass filter, such that the cross-sectional area of the aperture and/or recess increases in a tapered manner in a radially outward direction; and
applying voltages to the electrodes such that ions having mass to charge ratios in a desired range are confined by the electrodes and are transmitted along and through the mass filter, whereas ions having mass to charge ratios outside of said desired range are unstable and pass into or through the aperture and/or into the recess such that they are filtered out by the mass filter;
wherein ions that pass into or through the aperture and/or into the recess are not detected and are neutralised or discarded.

13. The method of claim 12 , further comprising detecting ions transmitted by the mass filter and/or mass analysing ions transmitted by the filter.

14. A mass and/or ion mobility spectrometer comprising:
a first mass filter comprising a plurality of electrodes;
a second mass filter comprising a plurality of electrodes arranged downstream of the first mass filter so as to receive ions transmitted by the first mass filter;
a RF-only ion guide arranged between the first mass filter and the second mass filter so as to guide the ions transmitted by the first mass filter into the second mass filter; one or more voltage supplies; and
a controller set up and configured to:
control said one or more voltage supplies so as to apply voltages to the first mass filter so that it mass selectively transmits only ions having a first range of mass to charge ratios, wherein at least one of the electrodes of the first mass filter comprises an aperture extending entirely through the electrode and/or comprises a recess extending only partially through the electrode, wherein the aperture and/or recess:
is arranged and configured such that when said voltages are applied to the first mass filter ions become unstable in the first mass filter and pass into or through the aperture and/or into the recess such that they are not transmitted by the first mass filter to the second mass filter, and
increases in cross-sectional area in a direction away from the central axis of the first mass filter, such that the cross-sectional area of the aperture and/or recess increases in a tapered manner in a radially outward direction; and
control said one or more voltage supplies so as to apply voltages to the second mass filter so that it mass filters the ions transmitted by the first mass filter, and such that the second mass filter only transmits ions having a second range of mass to charge ratios that is a sub-set of the first range of mass to charge ratios.

Assignees

• Micromass Ltd

Inventors

• Green Martin
• Wildgoose Jason
• Richardson Keith
• Giles Kevin
• Kenny Daniel
• Langridge David
• Moulds Richard

Classifications

• H01J49/4215 Primary

  Quadrupole mass filters (H01J49/4225 takes precedence) · CPC title

• H01J49/421 Primary

  Mass filters, i.e. deviating unwanted ions without trapping · CPC title

• H01J49/4255

  with particular constructional features · CPC title

• H01J49/067

  Ion lenses, apertures, skimmers · CPC title

• H01J49/0027

  Methods for using particle spectrometers · CPC title