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EP-4736215-A1 - MASS SPECTROMETERS COMPRISING A STATIC MASS PRE-FILTER

EP4736215A1EP 4736215 A1EP4736215 A1EP 4736215A1EP-4736215-A1

Abstract

A mass spectrometer comprises an ion source, a static mass pre-filter downstream of the ion source, a collision cell downstream of the static mass pre-filter, at least one mass analyzer downstream of the collision cell, and at least one ion detector downstream of the at least one mass analyzer. The static mass pre-filter (20) comprises a first magnetic sector unit (21) for separating ions into partial ions beams (2), a second magnetic sector unit (22) for merging the partial ion beams, and a slit (23) arranged between the first magnetic sector unit and the second magnetic sector unit for selectively passing partial ion beams (2). The partial ion beams (2) may be symmetric relative to a plane (S) perpendicular to the partial ion beams.

Inventors

  • SCHWIETERS, JOHANNES
  • JUNG, GERHARD

Assignees

  • Thermo Fisher Scientific (Bremen) GmbH

Dates

Publication Date
20260506
Application Date
20240628

Claims (20)

  1. 1. A mass spectrometer, comprising an ion source, a static mass pre-filter downstream of the ion source, a collision cell downstream of the static mass pre-filter, at least one mass analyzer downstream of the collision cell, and at least one ion detector downstream of the at least one mass analyzer, characterized in that the static mass pre-filter comprises a first magnetic sector unit for separating ions into partial ions beams, a second magnetic sector unit for merging partial ion beams, and a slit arranged between the first magnetic sector unit and the second magnetic sector unit for selectively passing partial ion beams, and in that the selected partial ion beams are symmetric.
  2. 2. The mass spectrometer according to claim 1, wherein the first magnetic sector unit is configured for separating ions into parallel partial ion beams.
  3. 3. The mass spectrometer according to claim 1, wherein the first magnetic sector unit is configured for separating ions into diverging partial ion beams.
  4. 4. The mass spectrometer according to claim 1, wherein the mass pre-filter comprises an ion lens assembly arranged between the first magnetic sector unit and the second magnetic sector unit.
  5. 5. The mass spectrometer according to claims 2 and 4, wherein the ion lens assembly comprises a first pair of lenses upstream of the slit and a second pair of lenses downstream of the slit.
  6. 6. The mass spectrometer according to claim 5, wherein the first pair of lenses comprises a first zoom lens for converting the parallel ion beams into diverging ions beams and a correction lens for converting the diverging ions beams into parallel ions beams, and wherein the second pair of lenses comprises a first correction lens for converting the parallel ion beams into converging ions beams and a zoom lens for converting the converging ions beams into parallel ions beams.
  7. 7. The mass spectrometer according to claims 3 and 4, wherein the ion lens assembly comprises an inversion lens.
  8. 8. The mass spectrometer according to claim 7 , wherein the ion lens assembly comprises a single inversion lens which is preferably arranged upstream of the slit.
  9. 9. The mass spectrometer according to claim 7 , wherein the ion lens assembly comprises a pair of inversion lenses which are preferably arranged on either side of the slit.
  10. 10. The mass spectrometer according to claim 7 , wherein the ion lens assembly comprises an inversion lens and a pair of zoom lenses, the zoom lenses being arranged on either side of the inversion lens, the inversion lens preferably being arranged downstream of the slit.
  11. 11. The mass spectrometer according to any of the preceding claims, wherein the at least one mass analyzer comprises a magnetic sector mass analyzer.
  12. 12. The mass spectrometer according to any of the preceding claims, wherein the at least one mass analyzer comprises a multipole mass filter, preferably a quadrupole mass filter.
  13. 13. The mass spectrometer according to any of the preceding claims, further comprising an electric sector unit downstream of the collision cell.
  14. 14. The mass spectrometer according to any of the preceding claims, wherein the partial ion beams are mirror symmetric relative to a plane perpendicular to at least one partial ion beam.
  15. 15. The mass spectrometer according to any of the preceding claims, wherein the partial ion beams are mirror symmetric relative to a plane coinciding with at least one partial ion beam.
  16. 16. The mass spectrometer according to any of the preceding claims, wherein the partial ion beams are symmetric for at least a selected range of mass-to-charge ratios.
  17. 17. The mass spectrometer according to claim 16, wherein the selected range of mass-to-charge ratios comprises at least all isotopes of an element of which ions are to be detected.
  18. 18. The mass spectrometer according to any of the preceding claims, which is an isotope ratio mass spectrometer.
  19. 19. A static mass pre-filter for use in a mass spectrometer, characterized in that the mass pre-filter comprises a first magnetic sector unit for separating ions into partial ion beams, a second magnetic sector unit for merging partial ion beams, and a slit arranged between the first magnetic sector unit and the second magnetic sector unit for selectively passing partial ion beams, and in that the magnetic sector units are arranged for producing symmetric selected partial ion beams.
  20. 20. The static mass pre-filter according to claim 19, wherein the first magnetic sector unit is configured for separating ions into parallel ion beams.

Description

MASS SPECTROMETERS COMPRISING A STATIC MASS PRE-FILTER Field of the invention The present invention relates to mass spectrometers. More in particular, the invention relates to mass spectrometers comprising at least one pre-filter to filter ions before they enter a further component of the mass spectrometer, such as a collision cell. Background of the invention US 2018/308674 Al (Schwieters et al.) describes a mass spectrometer comprising an ion source, a mass filter, a collision cell, and a sector field mass analyzer. The mass filter upstream of the collision cell, which may be referred to as mass pre-filter, is a quadrupole mass filter, which requires a varying field to filter ions according to their m/z ratio. Although such dynamic mass filters function well, the resulting different trajectories of ions having different m/z ratios, and thus the different travel times of the ions, may in some instances cause isotope discrimination. US 2022/223401 Al (Schwieters et al.) describes an isotope ratio mass spectrometer comprising an ion source, a static field mass filter, a collision/reaction cell, and a sector field mass analyser for spatially separating ions from the reaction cell according to their mass-charge ratio (m/z ratio). A detector platform is configured for detecting a plurality of different ion species separated by the sector field mass analyser. The static field mass filter acts as a pre-filter to filter ions from the ion source before they enter the reaction cell. The static field mass filter of US 2022/223401 Al comprises a first Wien filter that deflects ions away from a longitudinal symmetry axis of the mass spectrometer in accordance with the ions' m/z ratio, and a second Wien filter that deflects ions back towards the longitudinal symmetry axis in accordance with the ions' m/z ratio. An inverting lens is positioned along the longitudinal axis between the Wien filters to invert the direction of deflection of the ions from the first Wien filter. The deflected ions return to substantially the same trajectories, independent of the m/z ratios, thus allowing a high-resolution isotope analysis, for example. Summary of the invention The present invention provides a mass spectrometer comprising an ion source, a static mass prefilter downstream of the ion source, a collision/reaction cell downstream of the mass pre-filter, at least one mass analyzer downstream of the collision/reaction cell, and at least one ion detector downstream of the at least one mass filter. The mass pre-filter can comprise a first magnetic sector unit for separating ions into partial ion beams, a second magnetic sector unit for merging the partial ion beams, and a slit arranged between the first magnetic sector unit and the second magnetic sector unit for selectively passing partial ion beams. At least the selected partial ion beams can be symmetric. The first magnetic sector unit can be configured for separating ions into parallel, diverging, or converging partial ion beams. The mass pre-filter may comprise an ion lens assembly arranged between the first magnetic sector unit and the second magnetic sector unit, which ion lens assembly may comprise an inversion lens and/or other ion lenses. The ion lens assembly may comprise a first lens or pair of lenses upstream of the slit and a second lens or pair of lenses downstream of the slit (or slit mechanism), or a single lens or pair of lenses of one side of the slit only. Instead of a single slit, multiple slits and/or diaphragms may be provided. The single or multiple slits and/or diaphragms may be movable. The slits (or slit mechanisms) or diaphragms may be arranged perpendicular to an axis of the arrangement of magnetic sector units but may also be slanted relative to such an axis. The first pair of lenses may comprise a first zoom lens for converting the parallel ion beams into diverging ions beams and a correction lens for converting the diverging ions beams into parallel ions beams. The second pair of lenses may comprise a first correction lens for converting the parallel ion beams into converging ions beams and a zoom lens for converting the converging ions beams into parallel ions beams. The ion lens assembly may comprise an inversion lens, for example a single inversion lens which is preferably arranged upstream of the slit. Alternatively, the ion lens assembly may comprise a pair of inversion lenses, preferably arranged on either side of the slit. In an embodiment, the ion lens assembly may comprise an inversion lens and a pair of zoom lenses, the zoom lenses being arranged on either side of the inversion lens, the inversion lens preferably being arranged downstream of the slit. The ion source may comprise an inductively coupled plasma (ICP) ion source, for example. However, other ion sources may also be used, such as glow discharge sources, photo-ionization sources, and other ion sources. The collision/reaction cell (which may also be referred to as collision cell or