Claims
- 1. A time-of-flight mass spectrometer comprising:a) an ion source; b) an ion selector that selects ions generated by the ion source substantially within a predetermined mass-to-charge ratio range; c) a pulsed ion accelerator positioned in a flight path of the selected ions and fragments thereof, the pulsed ion accelerator accelerating the selected ions and fragments thereof; and d) an electrode positioned in the flight path of the accelerated selected ions and fragments thereof after the pulsed ion accelerator, the electrode being biased with a time varying bias voltage that increases the kinetic energy of the fragments relative to the selected ions.
- 2. The mass spectrometer of claim 1 further comprising an ion fragmentor positioned in a flight path of the ions from the ion source, wherein the ion fragmentor fragments a fraction of the ions.
- 3. The mass spectrometer of claim 2 wherein the ion selector and the ion fragmentor are contained within a single device.
- 4. The mass spectrometer of claim 1 wherein the ion source focuses a packet of ions substantially within the predetermined mass-to-charge ratio range onto a focal plane in a flight path of the ions.
- 5. The mass spectrometer of claim 4 wherein the ion selector is positioned substantially at the focal plane.
- 6. The mass spectrometer of claim 4 wherein the focal plane is located between the ion selector and the pulsed ion accelerator.
- 7. The mass spectrometer of claim 4 wherein a time dispersion of the packet of ions is substantially minimized at the focal plane.
- 8. The mass spectrometer of claim 1 wherein the kinetic energy of the fragments relative to the selected ions is increased to substantially equal the kinetic energy of the selected ions.
- 9. The mass spectrometer of claim 1 wherein the ion source comprises a pulsed laser desorption/ionization ion source having delayed extraction.
- 10. The mass spectrometer of claim 1 wherein the time varying bias voltage increases the energy of the fragments relative to the selected ions, thereby increasing the mass resolution.
- 11. The mass spectrometer of claim 2 wherein the ion fragmentor comprises a collision cell wherein the ions collide with neutral molecules which causes the ions to energize sufficiently to fragment into ionic and neutral fragments.
- 12. The mass spectrometer of claim 1 further comprising an ion mirror positioned in the flight path of the selected ions and the fragments thereof after the electrode.
- 13. The mass spectrometer of claim 1 further comprising an ion detector positioned after the electrode, the ion detector detecting the selected ions and fragments thereof.
- 14. A method for improving mass resolution in time-of-flight mass spectrometers, the method comprising:a) selecting ions from a sample of interest that are substantially within a predetermined mass-to-charge ratio range; b) fragmenting a fraction of the selected ions to form fragments; and c) exposing the selected ions and the fragments thereof to a time varying bias voltage that adds energy to the fragments which at least partially compensates for energy lost due to fragmentation, thereby improving the mass resolution.
- 15. The method of claim 14 further comprising the step of analyzing the selected ions and the fragments thereof by time of flight mass spectrometry.
- 16. The method of claim 14 further comprising the step of generating ions from the group consisting of: electrospray, pneumatically-assisted electrospray, chemical ionization, MALDI, and ICP.
- 17. The method of claim 14 wherein the step of exposing the selected ions and fragments thereof to a time varying bias voltage comprises passing the ions through at least one of a grid and a conducting drift tube, wherein the at least one of the grid and the conducting drift tube are biased with the time varying bias voltage.
- 18. The method of claim 14 wherein the step of selecting ions comprises focusing generated ions having a predetermined mass-to-charge ratio range onto a timed ion selector and transmitting the selected ions through the timed ion selector while substantially blocking all other ions.
- 19. The method of claim 14 wherein the step of fragmenting a fraction of the selected ions comprises exciting the selected ions by colliding the selected ion with neutral gas molecules.
- 20. The method of claim 14 further comprising passing the selected ions and fragments thereof through a nearly field-free region after fragmentation, thereby allowing the selected ions to substantially complete fragmentation.
- 21. The method of claim 14 further comprising accelerating the selected ions and the fragments thereof after fragmentation.
- 22. A tandem time-of-flight mass spectrometer comprising:a) means for selecting ions that are substantially within a predetermined mass-to-charge ratio range; b) means for fragmenting a fraction of the selected ions to form fragments; and c) means for applying a time varying bias to the selected ions and the fragments thereof that adds energy to the fragments which at least partially compensates for energy lost due to fragmentation.
- 23. The mass spectrometer of claim 22 further comprising a means for generating ions from a sample of interest.
- 24. The mass spectrometer of claim 22 further comprising a means for analyzing the selected ions and the fragments thereof by time of flight mass spectrometry.
RELATED APPLICATION
This application claims priority to, and is a continuation of patent application Ser. No. 09/712,882 filed on Nov. 15, 2000, now U.S. Pat. No. 6,441,369 which is incorporated herein by reference.
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Number |
Name |
Date |
Kind |
4458149 |
Muga |
Jul 1984 |
A |
6204500 |
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Continuations (1)
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Number |
Date |
Country |
Parent |
09/712882 |
Nov 2000 |
US |
Child |
10/178631 |
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US |