Mass spectrometer

• US 5,864,137 A
• Filed: 10/01/1996
• Issued: 01/26/1999
• Est. Priority Date: 10/01/1996
• Status: Expired due to Term

• Current Assignee: Agena Bioscience Inc. (Mesa Laboratories Inc.)
• Original Assignee: GeneTrace Systems Inc.
• Inventors: Young, Steven E., Becker, Christopher H.
• Primary Examiner(s): NGUYEN, KIET TUAN
• Application Number:
  US08/724,210
• Time in Patent Office: 847 Days
• Field of Search: 250/287, 250/288, 250/281, 250/282
• US Class Current: 250/287
• CPC Class Codes: H01J 49/164 Laser desorption/ionisation, e.g. matrix-assisted laser desorption/ionisation [MALDI] sample holders H01J49/0418
• CPC Class Codes: H01J 49/403 characterised by the acceleration optics and/or the extraction fields

Abstract

The invention provides a mass spectrometer having improved mass resolution, accuracy, sensitivity, reduced complexity, lower cost, and greater ease of use. The mass spectrometer provided comprises a first electrode and a second electrode, in a nested configuration to create a two-stage acceleration region that accelerates ions across a minimized acceleration region, resulting in decreased metastable decay and improved mass accuracy and resolution. The mass spectrometer also comprises a n alignment system to align the ion optics with the laser beam used for desorption/ionization. The mass spectrometer further comprises electrical circuits for delivering high voltage pulses for pulsed delayed ion extraction.

Claims

1. A time-of-flight mass spectrometer comprising:

a) a first electrode which has a funnel shape; and

b) a second electrode, placed adjacent to the first electrode and arranged in conjunction with the first electrode such that the axes of the electrodes are aligned and a flow of ions of the sample may pass through the first and second electrodes,

wherein an end of the second electrode protrudes into a wide opening of the first electrode and wherein the time-of-flight tube has a longitudinal axis defining a deflected path with an acute angle between the deflected path and the flow of ions through the first and second electrodes.

2. The mass spectrometer as recited in claim 1, further comprising a deflector configured to deflect the flow of ions along the deflected path.

3. The mass spectrometer as recited in claim 2, further comprising a first insulating member and a second insulating member, the first electrode being mounted to the first insulating member and the second electrode being mounted to the second insulating member.

4. The mass spectrometer as recited in claim 2, further comprising an ionizer configured to produce ions of the sample.

5. The mass spectrometer as recited in claim 4, wherein the ionizer is a laser.

6. A mass spectrometer comprising an alignment system configured to facilitate alignment of a first electrode, a sample, an ionizing beam produced by an ionizer, and a time-of-flight tube, wherein the time-of-flight tube has a longitudinal axis defining a deflected path with an acute angle between the deflected path and the path of the flow of ions through the first electrode and a second electrode.

7. The mass spectrometer as recited in claim 6, wherein the alignment system includes an aligning tube having a longitudinal axis along the path of the flow of ions through the first and second electrodes.

8. The mass spectrometer as recited in claim 7, wherein the alignment system further includes an illuminator configured to shine light through the aligning tube and through the first electrode.

9. The mass spectrometer as recited in claim 8, wherein the alignment system further includes a steering mirror adjustable to align the ionizing beam with the light on the sample.

10. The mass spectrometer as recited in claim 9, wherein the ionizer is a laser.

11. The mass spectrometer as recited in claim 10, further comprising a capacitor configured to capacitively couple a pulse power supply to at least one of the sample, the first electrode, and the second electrode.

12. The mass spectrometer as recited in claim 11, further comprising:

a switch having a source side in communication with the pulse power supply and a load

side in communication with the coupling capacitor, the switch being configured to couple the pulse power supply to the coupling capacitor when the switch is closed;

a bias resistor connected to the load side of the switch and through which the pulse power supply is connected to ground when the switch is closed; and

a constant voltage supply which is coupled, through a constant voltage supply isolation resistor, to at least one of the sample, the first electrode, and the second electrode, the constant voltage supply isolation resistor being configured to limit pulse power supply current toward the constant voltage supply.

13. The mass spectrometer as recited in claim 12, further comprising:

an energy storage capacitor placed across the pulse power supply;

a shunt diode placed across the bias resistor, the shunt diode being configured to protect the switch against reverse voltages;

a pulse power supply isolation resistor which connects the pulse power supply and the energy storage capacitor, and is configured to limit current from the pulse power supply;

a first load resistor, which couples the pulse power supply isolation resistor to the source side of the switch;

a first zener diode coupling the load side of the switch to the source side of the switch;

a second zener diode coupling ground to the load side of the switch;

a second load resistor, which couples the load side of the switch to the shunt diode, bias resistor, and coupling capacitor; and

a matching resistor, which connects the coupling capacitor to the mass spectrometer and to the constant high voltage supply isolation resistor.

14. The mass spectrometer as recited in claim 6, further comprising an ionizer configured to produce ions from the sample, wherein the first electrode has a conical shape and the second electrode is placed with a proximal end protriding into an interior volume of the first electrode and shaped such that a distance between the proximal end of the second electrode and the first electrode is smaller than a distance between any other part of the second electrode and the first electrode.

15. The mass spectrometer as recited in claim 14, wherein the first and second electrodes are configured to define the path along which the ions may flow.

16. The mass spectrometer as recited in claim 15, further comprising a deflector configured to deflect the flow of ions along the deflected path.

17. A mass spectrometer comprising:

a) an ionizer configured to produce ions of the sample;

b) a first electrode having a conical shape;

c) a second electrode axially aligned with the first electrode, placed with a proximal end protruding into an interior volume of the first electrode and with an end protruding into an aperture at a base of the first electrode and shaped such that a distance between the proximal end of the second electrode and the first electrode is smaller than a distance between any other part of the second electrode and the first electrode; and

d) a capacitor for pulsed delayed ion extraction configured to capacitively couple a power supply to at least one of the sample, the first electrode, and the second electrode;

wherein the first and second electrodes are spaced apart by at least one electrically insulating member and configured to define a path along which the ions may flow.

18. The mass spectrometer as recited in claim 17, further comprising a switch having a switching time of no longer than about 20 ns and configured to couple the power supply to the capacitor.

19. The mass spectrometer as recited in claim 18, further comprising a bias resistor coupling the switch to ground and through which the power supply is connected to ground when the switch is closed.

20. The mass spectrometer as recited in claim 19, further comprising a constant voltage supply configured to supply a constant voltage through a constant voltage supply isolation resistor to at least one of the sample, the first electrode, and the second electrode, to which the power supply is capacitively coupled through the capacitor.

21. The mass spectrometer as recited in claim 18, further comprising an alignment system configured to facilitate alignment of the first electrode, the sample and an ionizing beam produced by the ionizer with a time-of-flight tube, wherein the time-of-flight tube has a longitudinal axis defining a deflected path with an acute angle between the deflected path and the path of the flow of ions through the first electrode and a second electrode.

22. A time-of-flight mass spectrometer, comprising:

(a) ion optics defining a path for a flow of ions of a sample;

(b) a time-of-flight tube having a longitudinal axis which defines a deflected path with an acute angle between the deflected path and the path of the flow of ions through the ion optics; and

(c) an alignment system configured to facilitate alignment of an ionizing beam with the ion optics and the sample.

23. The mass spectrometer as recited in claim 22, wherein the alignment system comprises an aligning tube axially aligned with the path of the flow of ions through the ion optics.

24. The mass spectrometer as recited in claim 23, wherein the aligning tube is affixed to the time-of-flight tube.

25. The mass spectrometer as recited in claim 23, wherein the alignment system further comprises an illuminator configured to shine light through the aligning tube and the ion optics onto the sample.

26. The mass spectrometer as recited in claim 25, further comprising a steering mirror adjustable to align the ionizing beam with the light on the sample.

27. The mass spectrometer as recited in claim 26, further comprising an ionizer configured to produce the ionizing beam.

28. The mass spectrometer as recited in claim 27, wherein the ionizer is a laser.

29. An article of manufacture, comprising:

a) a time-of-flight mass spectrometer; and

b) a coupling capacitor for pulsed delayed ion extraction configured to capacitively couple a pulse power supply to the mass spectrometer.

30. The article of manufacture as recited in claim 29, further comprising a switch having a switching time of no longer than about 20 ns and having a source side in communication with the pulse power supply and a load side in communication with the coupling capacitor, the switch being configured to couple the pulse power supply to the coupling capacitor when the switch is closed.

31. The article of manufacture as recited in claim 30, further comprising a bias resistor connected to the load side of the switch and through which the pulse power supply is connected to ground when the switch is closed.

32. The article of manufacture as recited in claim 31, further comprising a constant voltage supply which is coupled, through a constant voltage supply isolation resistor, to the mass spectrometer together with the capacitively coupled pulse power supply, the constant voltage supply isolation resistor being configured to limit pulse power supply current toward the constant voltage supply.

33. The article of manufacture as recited in claim 32, further comprising an energy storage capacitor placed across the pulse power supply and a shunt diode placed across the bias resistor, the shunt diode being configured to protect the switch against reverse voltages in the mass spectrometer.

34. The article of manufacture as recited in claim 33, further comprising:

(a) a pulse power supply isolation resistor which connects the pulse power supply and the energy storage capacitor, and is configured to limit current from the pulse power supply;

(b) a first load resistor, which couples the pulse power supply isolation resistor to the source side of the switch;

(c) a first zener diode coupling the load side of the switch to the source side of the switch;

(d) a second zener diode coupling ground to the load side of the switch;

(e) a second load resistor, which couples the load side of the switch to the shunt diode, bias resistor, and coupling capacitor; and

(f) a matching resistor, which connects the coupling capacitor to the mass spectrometer and to the constant high voltage supply isolation resistor.

35. The mass spectrometer as recited in claim 30, further comprising an alignment system configured to facilitate alignment of the ion optics, a sample, and an ionizing beam produced by the ionizer with a time-of-flight tube, wherein the time-of-flight tube has a longitudinal axis defining a deflected path with an acute angle between the deflected path and the path of the flow of ions through the ion optics.

36. An electrical circuit for delivering high voltage pulses to a time-of-flight mass spectrometer comprising:

a) a pulse power supply; and

b) a coupling capacitor for pulsed delayed ion extraction configured to capacitively couple said pulse power supply to the time-of-flight mass spectrometer.

37. The electrical circuit as recited in claim 36, further comprising a speed switch having a switching capacity of no longer than about 20 ns and having a source side in communication with the pulse power supply and a load side in communication with the coupling capacitor, the switch being configured to couple the pulse power supply to the coupling capacitor when the switch is closed.

38. The electrical circuit as recited in claim 37, further comprising a bias resistor connected to the load side of the switch and through which the pulse power supply is connected to ground when the switch is closed.

39. The electrical circuit as recited in claim 38, further comprising a constant voltage supply which is coupled, through a constant voltage supply isolation resistor, to the mass spectrometer together with the capacitively coupled pulse power supply, the constant voltage supply isolation resistor being configured to limit pulse power supply current toward the constant voltage supply.

40. The electrical circuit as recited in claim 39, further comprising an energy storage capacitor placed across the pulse power supply and a shunt diode placed across the bias resistor, the shunt diode being configured to protect the switch against reverse voltages in the mass spectrometer.

41. The electrical circuit as recited in claim 40, further comprising:

a) a pulse power supply isolation resistor which connects the pulse power supply and the energy storage capacitor, and is configured to limit current from the pulse power supply;

b) a first load resistor, which couples the pulse power supply isolation resistor to the source side of the switch;

c) a first Zener diode coupling the load side of the switch to the source side of the switch;

d) a second Zener diode coupling ground to the load side of the switch;

e) a second load resistor, which couples the load side of the switch to the shunt diode, bias resistor, and coupling capacitor; and

f) a matching resistor, which connects the coupling capacitor to the mass spectrometer and to the constant high voltage supply isolation resistor.