UTILIZING GAS FLOWS IN MASS SPECTROMETERS

• US 20120228492A1
• Filed: 11/15/2010
• Published: 09/13/2012
• Est. Priority Date: 11/17/2009
• Status: Active Grant

• Current Assignee: Bruker Daltonics GmbH and Co KG (Bruker Corporation)
• Original Assignee: Bruker Daltonik GmbH (Bruker Corporation)
• Inventors: Franzen, Jochen
• Granted Patent: US 8,941,058 B2
• Time in Patent Office: Days
• US Class Current: 250/288
• CPC Class Codes: H01J 49/401 characterised by orthogonal acceleration, e.g. focusing or selecting the ions, pusher electrode
• CPC Class Codes: H01J 49/421 Mass filters, i.e. deviating unwanted ions without trapping

Abstract

The invention relates to ions guided by gas flows in mass spectrometers, particularly in RF multipole systems, and to RF quadrupole mass filters and their operation with gas flows in tandem mass spectrometers. The invention provides a tandem mass spectrometer in which the RF quadrupole mass filter is operated at vacuum pressures in the medium vacuum pressure regime, utilizing a gas flow to drive the ions are through the mass filter. Vacuum pressures between 0.5 to 10 pascal are maintained in the mass filter. The mass filter may be enclosed by a narrow enclosure to guide the gas flow. The quadrupole mass filter may be followed by an RF multipole system, operated at the same vacuum pressure, serving as fragmentation cell to fragment the selected parent ions. The fragmentation cell may be enclosed by the same enclosure which already encloses the mass filter, so the ions may be driven by the same gas flow at the same vacuum pressure, greatly simplifying the required vacuum pumping system in tandem mass spectrometers. There are many other applications utilizing gas flows including supersonic gas jets in mass spectrometry.

Claims

1-10. -10. (canceled)

11. A mass spectrometer, comprising:

a Laval nozzle for the generation of a supersonic gas jet for guiding ions in a medium vacuum regime with a pressure between 10² to 10<sup>−

1</sup> Pascal, and

a compression funnel for accepting and transmitting the gas of the supersonic gas jet such that the ions are transported into a chamber at a pressure higher than the pressure in the medium vacuum regime.

12. A mass spectrometer according to claim 11, comprising means for the generation of an enveloping gas stream to reduce the friction between the supersonic gas jet and the ambient gas.

17. The mass spectrometer of claim 11, further comprising a compression funnel and a three-dimensional ion trap wherein the supersonic gas jet pushes ions through the compression funnel into the three-dimensional RF ion trap while at the same time establishing a working pressure in the three-dimensional ion trap.

18. The mass spectrometer of claim 17, wherein the supersonic gas jet is a helium gas jet.

19. The mass spectrometer of claim 18, wherein the ions are introduced laterally into the supersonic jet of helium.

20. The mass spectrometer of claim 11, wherein the compression funnel has a shape that does not reflect the supersonic gas jet sharply.

21. The mass spectrometer of claim 11, wherein the Laval nozzle has a compression factor between two and five.

13. A triple quadrupole mass spectrometer, having linearly arranged in series, a selection quadrupole that isolates selected parent ion species, a fragmentation quadrupole in which the selected parent ion species are fragmented through collisions, and an analyzer quadrupole that analyzes ions in accordance with their charge related mass m/z, comprising:

a differential pumping system to maintain a medium vacuum pressure between 10² and 10<sup>−

1</sup> Pascal within the triple quadrupole mass spectrometer; and

a nozzle to generate a supersonic gas flow through the triple quadrupole mass spectrometer for the transport of ions, wherein the selected parent ions are accelerated by a voltage difference between 30 and 200 volts between the selection quadrupole and the fragmentation quadrupole such that fragmentation occurs in collisions with the gas molecules of the supersonic gas flow, and wherein one of a curved and angled RF multipole rod system is located at the exit of the analyzer quadrupole to separate the ions from the supersonic gas flow.

16. The triple quadrupole mass spectrometer of claim 13, comprising an electron source that laterally introduces reactive ions for electron transfer dissociation into the fragmentation quadrupole.

14. A mass spectrometer with a quadrupole rode system, the mass spectrometer comprising:

a Laval nozzle for the generation of a supersonic gas jet for guiding ions; and

a partitioning wall between two regions of different pressure, the Laval nozzle having a rounded inlet in and extending into the quadrupole rod system, wherein the Laval nozzle is made from a high resistivity dielectric such that RF alternating fields produced by pole rods of the quadrupole rod system extend therethrough.

15. The mass spectrometer of claim 14, wherein the Laval nozzle has an outlet with a widening diameter and a shape of the widening produces a pressure ratio such that a sharply defined, parallel supersonic gas jet is generated by the Laval nozzle.

22. A mass spectrometer having a vacuum chamber and a vacuum system for reducing gas pressure in the vacuum chamber and comprising:

a Laval nozzle for the generation of a supersonic gas jet that consists of an inert gas and ions and that guides ions into the vacuum chamber;

an electrode that drives the ions out of the supersonic gas jet in the vacuum chamber; and

a compression funnel for accepting and transmitting the gas of the supersonic gas jet into a second chamber having a pressure higher than the pressure in the vacuum chamber.

23. The mass spectrometer of claim 22, wherein the inert gas is pure nitrogen.

24. The mass spectrometer of claim 22, wherein the second chamber comprises a forepump that removes gas in the chamber so that most of the gas in the supersonic gas jet is removed by the forepump instead of the vacuum system of the mass spectrometer.

25. The mass spectrometer of claim 22, wherein the compression funnel is fabricated of titanium.

26. The mass spectrometer of claim 22, further comprising a potential source that produces an electric field between the electrode and one of an ion funnel and a second electrode located on a side of the supersonic gas jet opposite the electrode in order to drive the ions out of the supersonic gas jet.