Tandem quadrupole mass spectrometer for selected ion fragmentation studies and low energy collision induced dissociator therefor

• US 4,234,791 A
• Filed: 11/13/1978
• Issued: 11/18/1980
• Est. Priority Date: 11/13/1978
• Status: Expired due to Term

• Current Assignee: Research Corporation
• Original Assignee: Research Corporation
• Inventors: Enke, Christie G., Yost, Richard A., Morrison, James D.
• Primary Examiner(s): Dixon, Harold A.
• Application Number:
  US05/960,439
• Time in Patent Office: 736 Days
• Field of Search: 250/281, 250/423 R, 250/296, 250/284
• US Class Current: 250/281
• CPC Class Codes: H01J 49/005 by collision with gas, e.g. by introducing gas or by accelerating ions with an electric field
• CPC Class Codes: H01J 49/4215 Quadrupole mass filters H01J49/4225 takes precedence

Abstract

A tandem quadrupole-based mass spectrometer including a highly efficient intermediate fragmentation stage. The disclosed fragmentation stage employs collision-induced dissociation (CID), in an electrodynamic focus device, which may be a quadrupole operated in a broad band filter mode. The disclosed CID process occurs at low energy (e.g., less than 1 keV, but preferably 2 eV to 100 eV), and is quite different from the high energy (e.g, greater than 1 keV, and typically 3 keV to 10 keV) CID process in prior tandem instruments such as mass-analyzed ion kinetic energy spectrometry (MIKES) systems. The efficiency of the present CID fragmentation is as high as 65%.

Claims

1. A selected ion mass spectrometer for the analysis of unknown samples comprising:

a source capable of ionizing unknown sample molecules of widely varying molecular weights to produce molecular ions, fragment ions, and/or other ions derived from sample components;

first and second mass analyzers in tandem;

means for directing ionized unknown sample molecules, fragments or otherwise derived ions of sample components from said source into said first mass analyzer;

means, interposed between said mass analyzers, for fragmenting and/or reacting, by collision-induced dissociation or reaction, ionized sample molecules, fragments or derivatives selected by said first mass analyzer, the fragmentation and/or reaction being accomplished within a focus device and being induced by unknown sample ions, fragments or components having axial kinetic energies of less than 1 keV colliding with collision gas atoms or molecules; and

a detector responsive to the output of said second mass analyzer.

2. A mass spectrometer according to claim 1, wherein said focus device is an electrodynamic focus device.

3. A mass spectrometer according to claim 2, wherein the collision energy level is within the approximate range of 2 eV to 100 eV.

4. A mass spectrometer according to claim 1, wherein the collision energy level is within the approximate range of 2 eV to 100 eV.

5. A selected ion mass spectrometer for the analysis of unknown samples comprising:

a source capable of ionizing unknown sample molecules of widely varying molecular weights to produce molecular ions, fragment ions, and/or other ions derived from the sample components;

first and second analyzers in tandem;

means for directing unknown ionized sample molecules, fragments or otherwise derived ions of sample components from said source into said first mass analyzer;

a low-energy collision-induced dissociation fragmentation/reaction stage interposed between said mass analyzers for receiving selected ionized sample molecules, fragments or components from said first mass analyzer, for fragmenting or reacting the selected ionized sample molecules, fragments or derivatives into ionized further fragments or products, for collecting the ionized further fragments or products, and for directing the ionized further fragments or products into said second mass analyzer, said fragmentation/reaction stage including a collision gas-containing electrodynamic focus device; and

a detector responsive to the output of said second mass analyzer.

6. A mass spectrometer according to claim 5, wherein said electrodynamic focus device is a quadrupole-type device.

7. A mass spectrometer according to claim 6, wherein said quadrupole-type device is operated in a broad band filter mode.

8. A quadrupole-based selected ion mass spectrometer for the analysis of unknown samples comprising, in series:

a source capable of ionizing unknown sample molecules of widely varying molecular weights to produce molecular ions, fragment ions, and/or other ions derived from the sample components;

a first quadrupole-type mass analyzer capable of scanning and selecting ionized sample molecules, fragments or derivatives of particular mass over a range of atomic mass units;

a low-energy collision-induced dissociation fragmentation/reaction stage including an electrodynamic focus device, with a collision gas introduced into said electrodynamic focus device, said low-energy fragmentation/reaction stage arranged to receive the selected ionized sample molecules, fragments or derivatives from said first quadrupole-type mass analyzer, and producing ionized further fragments or products of the selected ionized sample molecules, fragments, or derivatives;

a second quadrupole-type mass analyzer capable of scanning over a range of atomic mass units for selecting ionized further fragments or products of particular mass; and

a detector at the output of said second quadrupole-type mass analyzer;

whereby the output of said detector may be examined as said first and/or second mass analyzers are scanned to produce a representation of a mass spectrum for identifying the unknown sample and/or components thereof.

9. A mass spectrometer according to claim 8, wherein said electrodynamic focus device is a quadrupole-type device.

10. A mass spectrometer according to claim 9, wherein said quadrupole type device is operated in a broad band filter mode.

11. A mass spectrometer according to claim 8, wherein selected ionized sample molecules received by said low-energy fragmentation stage have ion axial kinetic energies of less than 1 keV.

12. A mass spectrometer according to claim 11, wherein the selected ionized sample molecules have ion axial kinetic energies within the approximate range of 2 eV to 100 eV.

13. A mass spectrometer according to claim 8, wherein the collision gas is argon.

14. A mass spectrometer according to claim 8, wherein the collision gas is specifically chosen to enhance particular features of the fragmentation process.

15. A tandem quadrupole mass spectrometer for selected ion fragmentation studies to analyze unknown samples, comprising:

first, second and third quadrupole-type devices arranged in tandem;

means for operating said first and third quadrupole-type devices in a scanning mass analysis mode over a range of atomic mass units;

means for operating said second quadrupole-type device in a broad-band filter mode;

means for introducing a collision gas into said second quadrupole-type device;

a source capable of ionizing unknown sample molecules of widely varying molecular weights to produce molecular ions, fragment ions, and/or other ions derived from the sample components;

means for injecting molecular ions produced by said source into said first quadrupole-type device at relatively low ion axial kinetic energies; and

means for detecting the output of said third quadrupole-type device

16. A quadrupole mass spectrometer according to claim 15, wherein molecular ions selected by said first quadrupole-type device are injected into said second quadrupole-type device for collisions with the atoms or molecules of said collision gas at ion axial kinetic energies of less than 1 keV.

17. A quadrupole mass spectrometer according to claim 16, wherein the selected molecular ions are injected into said second quadrupole-type device at ion axial kinetic energies within the approximate range of 2 eV to 100 eV.

18. An efficient arrangement for fragmenting molecular ions by collision-induced dissociation and collecting the resultant fragments, said arrangement comprising:

an electrodynamic focus device;

a collision gas introduced into said electrodynamic focus device; and

means for injecting molecular ions at relatively low ion kinetic energies into one end of said electrodynamic focus device;

fragments or reaction products of the injected molecular ions being produced as a result of collisions with the atoms or molecules of said collision gas, being confined radially within said electrodynamic focus device, and exiting from the other end of said electrodynamic focus device, the collision gas being specifically chosen to enhance particular features of the fragmentation and/or reaction process.

19. A method for analyzing unknown samples by tandem mass spectroscopy, comprising the steps of:

(1) ionizing a quantity of unknown sample to produce molecular ions, fragment ions and/or other ions derived from sample components;

(2) mass scanning the molecular ions, fragment ions and/or derivative ions to select ions of various particular molecular weights at different times during a mass scan;

(3) directing ions selected in step (2) at relatively low ion kinetic energies into an electrodynamic focus device having a collision gas introduced therein, fragment or product ions being produced as a result of collisions between the selected ions and the collision gas atoms or molecules;

(4) mass scanning the fragment or product ions produced in step (3) for each of the various particular weights selected during the step (2) mass scan; and

(5) detecting the ions selected in step (4) to produce a representation of a mass spectrum for comparison with reference spectra to identify an unknown sample and/or components thereof.

20. A method according to claim 19, wherein in step (3) ions are directed at axial kinetic energies of less than 1 keV into the electrodynamic focus device.

21. A method according to claim 20, wherein the step (3) ions are directed at axial kinetic energies within the approximate range of 2 eV to 100 eV.