Multi-reflecting Time-of-flight Mass Spectrometer With Orthogonal Acceleration

• US 20070176090A1
• Filed: 10/11/2006
• Published: 08/02/2007
• Est. Priority Date: 10/11/2005
• Status: Active Grant

• Current Assignee: LECO Corporation
• Original Assignee: LECO Corporation
• Inventors: Verentchikov, Anatoli
• Granted Patent: US 7,772,547 B2
• Time in Patent Office: Days
• US Class Current: 250/287
• CPC Class Codes: H01J 49/401 characterised by orthogonal acceleration, e.g. focusing or selecting the ions, pusher electrode
• CPC Class Codes: H01J 49/406 with multiple reflections

Abstract

The disclosed apparatus includes a multi-reflecting time-of-flight mass spectrometer (MR-TOF MS) and an orthogonal accelerator. To improve the duty cycle of the ion injection at a low repetition rate dictated by a long flight in the MR-TOF MS, multiple measures may be taken. The incoming ion beam and the accelerator may be oriented substantially transverse to the ion path in the MR-TOF, while the initial velocity of the ion beam is compensated by tilting the accelerator and steering the beam for the same angle. To further improve the duty cycle of any multi-reflecting or multi-turn mass spectrometer, the beam may be time-compressed by modulating the axial ion velocity with an ion guide. The residence time of the ions in the accelerator may be improved by trapping the beam within an electrostatic trap. Apparatuses with a prolonged residence time in the accelerator provide improvements in both sensitivity and resolution.

Claims

1. A multi-reflecting time-of-flight mass spectrometer (MR-TOF MS), comprising:

an ion source for generating an ion beam;

an orthogonal accelerator to convert the ion beam into ion packets;

an interface for ion transfer between said ion source and said orthogonal accelerator; and

a planar multi-reflecting analyzer providing multiple reflections of the ion packets within a jig-saw trajectory plane,

wherein the ion beam past said interface is oriented substantially across said trajectory plane.

2. The MR-TOF MS as in claim 1, further comprising an ion deflector to steer ion packets, wherein the direction and energy of the ion beam and, correspondingly, the angle of ion steering, are adjusted to compensate time distortions introduced by ion steering.

3. The MR-TOF MS as in claim 1, wherein the angle between said ion beam and a normal to said trajectory plane is less than 10 degrees.

4. The MR-TOF MS as in claim 1, wherein the angle between said ion beam and a normal to said trajectory plane is less than 5 degrees.

5. The MR-TOF MS as in claim 1, wherein the angle between said ion beam and a normal to said trajectory plane is less than 3 degrees.

6. The MR-TOF MS as in claim 1, wherein said planar multi-reflecting analyzer comprises a plurality of grid-free ion mirrors with a field-free space therebetween, and wherein said set of periodic lenses is provided in the field-free space.

7. The MR-TOF MS as in claim 1, wherein said ion source is one of:

ESI, APPI, APCI, ICP, EI, CI, SIMS, vacuum MALDI, atmospheric MALDI, MALDI at an intermediate gas pressure, a fragmentation cell of tandem mass spectrometer, and an ion reaction cell of tandem mass spectrometer.

8. A multi-reflecting time-of-flight mass spectrometer (MR-TOF MS), comprising:

an ion source for generating an ion beam;

an orthogonal accelerator to convert the ion beam into ion packets;

an interface for ion transfer between said ion source and said orthogonal accelerator; and

a multi-reflecting analyzer providing multiple reflections of the ion packets within electrostatic fields,

wherein said interface comprises a gas-filled radio frequency ion guide, said ion guide having means for periodic modulation of an axial electric field.

9. The MR-TOF MS as in claim 8, further comprising a transfer channel in between said ion guide and said orthogonal accelerator, said transfer channel is connected to an accelerating voltage for rapid ion transfer below 50 μ

s.

10. The MR-TOF MS as in claim 8, wherein said ion source is one of:

ESI, APPI, APCI, ICP, EI, CI, SIMS, vacuum MALDI, atmospheric MALDI, MALDI at an intermediate gas pressure, a fragmentation cell of tandem mass spectrometer, and an ion reaction cell of tandem mass spectrometer.

11. A multi-reflecting time-of-flight mass spectrometer (MR-TOF MS), comprising:

an ion source for generating an ion beam;

an orthogonal accelerator to convert the ion beam into ion packets;

an interface for ion transfer between said ion source and said orthogonal accelerator; and

a multi-reflecting analyzer providing multiple reflections of the ion packets within electrostatic fields,

wherein said orthogonal accelerator comprises an electrostatic trap.

12. The MR-TOF MS as in claim 11, wherein said electrostatic trap comprises miniature multi-reflecting and grid-free ion mirrors separated by a drift space and a mesh or a slot on a side of the drift space, said elements are arranged such that the ion beam experiences multiple reflections between said ion mirrors before being extracted through said mesh or slot by electric pulse.

13. The MR-TOF MS as in claim 11, wherein said electrostatic trap comprises a pair of coaxial ion mirrors arranged around the orthogonal acceleration stage and said ion interface comprises a device for modulating ion beam intensity or an ion accumulating device.

14. The MR-TOF MS as in claim 11, wherein said ion source is one of:

ESI, APPI, APCI, ICP, EI, CI, SIMS, vacuum MALDI, atmospheric MALDI, MALDI at an intermediate gas pressure, a fragmentation cell of tandem mass spectrometer, and an ion reaction cell of tandem mass spectrometer.

15. A method of multi-reflecting time-of-flight mass spectrometry, comprising the steps of:

forming an ion beam;

forming ion packets by applying a pulsed electric field in a substantially orthogonal direction to the ion beam;

introducing the ion packets into a field-free space in between ion mirrors, the ion mirrors forming a substantially two-dimensional electric field, extended along a drift axis; and

orienting the pulsed electric field substantially orthogonal to the drift direction such that the ion packets experience multiple reflections combined with slow displacement along the drift direction, thus forming a jig-saw ion path within a trajectory plane,

wherein said ion beam travels substantially orthogonal to the trajectory plane.

16. The method as in claim 15, further comprising a step of periodic focusing of ion packets in the drift direction and in between ion reflections in the ion mirrors.

17. The method as in claim 15, wherein the electric field of the ion mirrors is arranged to provide for high order spatial and time-of-flight focusing with respect to ion energy and to spatial and angular spread across the trajectory plane.

18. The method as in claim 15, further comprising a step of ion packet steering after the step of ion packet formation and wherein the orthogonal pulsed electric field is tilted to trajectory plane in order to compensate for time distortions introduced by the steering step.

19. The method as in claim 15, wherein said ion beam travels at an angle of less than 10 degrees from a normal to the trajectory plane.

20. The method as in claim 15, wherein said ion beam travels at an angle of less than 5 degrees from a normal to the trajectory plane.

21. The method as in claim 15, wherein said ion beam travels at an angle of less than 3 degrees from a normal to the trajectory plane.

22. The method as in claim 15, further comprising an additional step of sample separation in liquid phase prior to the step of ion beam formation.

23. The method as in claim 15, wherein the step of ion beam formation is made using one of:

ESI, APPI, APCI, ICP, EI, CI, SIMS, vacuum MALDI, atmospheric MALDI, and MALDI at an intermediate gas pressure.

24. The method as in claim 15, wherein the method of analysis further comprises additional steps of ion mass separation and fragmentation after the step of ion beam formation.

25. A method of multi-pass time-of-flight mass spectrometry, comprising the steps of:

forming an ion beam;

delivering the beam to a region of ion packet formation;

forming ion packets by applying a pulsed electric field in a substantially orthogonal direction to the ion beam; and

introducing the ion packets into an electrostatic field of a multi-reflecting time-of-flight analyzer, such that the ion packets experience multiple reflections,

wherein said step of ion beam delivery further comprises a step of time-modulating the intensity of the ion beam by axial electric field within an ion guide at an intermediate gas pressure, the modulation is synchronized to orthogonal electric pulses.

26. The method as in claim 25, further comprising a step of ion beam acceleration-deceleration for rapid transfer of said modulated ion beam to the orthogonal pulsed electric field.

27. The method as in claim 25, further comprising an additional step of sample separation in liquid phase prior to the step of ion beam formation.

28. The method as in claim 25, wherein the step of ion beam formation is made using one of:

ESI, APPI, APCI, ICP, EI, CI, SIMS, vacuum MALDI, atmospheric MALDI, and MALDI at an intermediate gas pressure.

29. The method as in claim 25, wherein the method of analysis further comprises additional steps of ion mass separation and fragmentation after the step of ion beam formation.

30. A method of multi-pass time-of-flight mass spectrometry, comprising the steps of:

forming an ion beam;

delivering the ion beam to a region of ion packet formation;

forming ion packets by applying a pulsed electric field in an electrostatic trap in a substantially orthogonal direction to the ion beam; and

introducing the ion packets into an electrostatic field of a multi-reflecting time-of-flight analyzer, such that the ion packets experience multiple reflections,

wherein said step of ion beam delivery into said pulsed electric field of the electrostatic trap further comprises a step of ion trapping in an electrostatic field and wherein at least a portion of trapped ions remains in a region of pulsed acceleration.

31. The method as in claim 30, wherein the trapping electrostatic field of the electrostatic trap is planar and ions are injected through the edge of the field structure.

32. The method as in claim 30, wherein the trapping electrostatic field of the electrostatic trap is coaxial and ions are injected through a pulsed switched field.

33. The method as in claim 30, further comprising an additional step of sample separation in liquid phase prior to the step of ion beam formation.

34. The method as in claim 30, wherein the step of ion beam formation is made using one of:

ESI, APPI, APCI, ICP, EI, CI, SIMS, vacuum MALDI, atmospheric MALDI, and MALDI at an intermediate gas pressure.

35. The method as in claim 30, wherein the method of analysis further comprises additional steps of ion mass separation and fragmentation after the step of ion beam formation.