Mass Spectrometer

• US 20100327157A1
• Filed: 12/10/2007
• Published: 12/30/2010
• Est. Priority Date: 12/08/2006
• Status: Active Grant

• Current Assignee: Micromass UK Ltd (Waters Corporation)
• Original Assignee: Micromass UK Ltd (Waters Corporation)
• Inventors: Green, Martin, Wildgoose, Jason Lee
• Granted Patent: US 8,598,518 B2
• Time in Patent Office: Days
• US Class Current: 250/282
• CPC Class Codes: H01J 49/065 having stacked electrodes, e.g. ring stack, plate stack
• CPC Class Codes: H01J 49/40 Time-of-flight spectrometers H01J49/36 takes precedence
• CPC Class Codes: H01J 49/403 characterised by the acceleration optics and/or the extraction fields
• CPC Class Codes: H01J 49/4225 Multipole linear ion traps, e.g. quadrupoles, hexapoles
• CPC Class Codes: H01J 49/426 Methods for controlling ions

Abstract

A mass spectrometer is disclosed comprising a time of flight mass analyser (7). The time of flight mass analyser (7) comprises an ion guide comprising a plurality of electrodes (1) which are interconnected by a series of resistors (2) forming a potential divider. Ions are confined radially within the ion guide by the application of a two-phase RF voltage to the electrodes (1). A single phase additional RF voltage is applied across the potential divider so that an inhomogeneous pseudo-potential force is maintained along the length of the ion guide.

Claims

1. A time of flight mass analyser comprising:

an ion guide comprising a plurality of electrodes;

first means arranged and adapted to confine ions radially within said ion guide; and

second means arranged and adapted to apply a time varying inhomogeneous axial electric field along at least a portion of the axial length of said ion guide.

11. A time of flight mass analyser as claimed in claim 1, wherein said first means comprises first RF voltage means arranged and adapted to apply a first RF voltage to at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% of the electrodes forming said ion guide in order to confine ions radially within said ion guide.

15. A time of flight mass analyser as claimed in claim 11, wherein said first RF voltage applied, in use, to said electrodes causes or generates a radial pseudo-potential well which acts to confine ions radially, in use, within said ion guide, or wherein said first RF voltage comprises a two-phase or multi-phase RF voltage.

18. A time of flight mass analyser as claimed in claim 1, wherein said second means comprises means for applying a second RF voltage to said electrodes.

19. A time of flight mass analyser as claimed in claim 18, wherein said second RF voltage comprises a single phase RF voltage.

20. A time of flight mass analyser as claimed in claim 18, wherein the phase difference of said second RF voltage between adjacent electrodes or adjacent groups of electrodes is substantially 0°

.

23. A time of flight mass analyser as claimed in claim 18, wherein in a mode of operation the maximum amplitude of said second RF voltage at one or more points along the axial length of said ion guide is arranged to remain substantially constant with time or is arranged to vary, increase or decrease with time.

26. A time of flight mass analyser as claimed in claim 1, wherein said second means is arranged and adapted to apply a time varying axial electric field along at least a portion of the axial length of said ion guide and wherein said axial electric field increases or decreases along the length of said ion guide in a direction from an ion entrance region of said ion guide to an ion exit region of said ion guide.

27. A time of flight mass analyser as claimed in claim 26, wherein said axial electric field is arranged to increase or decrease in a linear or non-linear manner along the length of said ion guide in a direction from an ion entrance region of said ion guide to an ion exit region of said ion guide.

28. A time of flight mass analyser as claimed in claim 1, wherein said second means is arranged and adapted to accelerate or decelerate ions axially along at least a portion of the axial length of said ion guide.

29. A time of flight mass analyser as claimed in claim 1, wherein said second means further comprises one or more auxiliary electrodes.

38. A time of flight mass analyser as claimed in claim 1, wherein said time of flight mass analyser comprises a reflectron time of flight mass analyser wherein in a mode of operation ions travel in a first direction, are reflected within said ion guide and then travel in a second direction which is substantially opposed to said first direction.

39. A time of flight mass analyser as claimed in claim 1, wherein in a mode of operation ions enter said ion guide via an entrance electrode, entrance region or entrance aperture and traverse the length of said ion guide and exit said ion guide via an exit electrode, exit region or exit aperture.

40. A time of flight mass analyser as claimed in claim 39, wherein ions are not substantially reflected axially within said ion guide as they traverse from said entrance electrode, entrance region or entrance aperture to said exit electrode, exit region or exit aperture.

2-10. -10. (canceled)

12-14. -14. (canceled)

16. (canceled)

17. (canceled)

21. (canceled)

22. (canceled)

24. (canceled)

25. (canceled)

30-37. -37. (canceled)

41-87. -87. (canceled)

88. A method of mass analysing ions according to their time of flight comprising:

providing an ion guide comprising a plurality of electrodes;

confining ions radially within said ion guide; and

applying a time varying inhomogeneous axial electric field along at least a portion of the axial length of said ion guide.

89. (canceled)

90. (canceled)

91. A method of temporally separating ions according to their mass to charge ratio and/or ion mobility, comprising:

providing an ion guide comprising a plurality of electrodes;

confining ions radially within said ion guide; and

applying a time varying inhomogeneous axial electric field along at least a portion of the axial length of said ion guide.

92. A method of temporally separating ions as claimed in claim 91, wherein applying the time varying inhomogeneous electric field comprises applying a supplemental voltage that varies as a cosine and has an amplitude of oscillation that varies from electrode to electrode of the plurality of electrodes.