Radio-frequency ionization of chemicals

• US 9,818,593 B2
• Filed: 09/13/2013
• Issued: 11/14/2017
• Est. Priority Date: 09/13/2012
• Status: Active Grant

• Current Assignee: University of Maine System Board of Trustees
• Original Assignee: University of Maine System Board of Trustees
• Inventors: Solouki, Touradj, Zekavat, Behrooz
• Primary Examiner(s): STOFFA, WYATT A
• Application Number:
  US14/426,475
• Publication Number:
  US 20150221492A1
• Time in Patent Office: 1,523 Days
• CPC Class Codes: H01J 27/16 using high-frequency excitation, e.g. microwave excitation
• CPC Class Codes: H01J 49/105 using high-frequency excitation, e.g. microwave excitation, Inductively Coupled Plasma [ICP]
• CPC Class Codes: H01J 49/36 Radio frequency spectrometers, e.g. Bennett-type spectrometers, Redhead-type spectrometers

Abstract

Methods and systems for performing ionization, including applying radio frequency energy to a chemical compound so that at least one ion of the compound or of a compound fragment is generated, and detecting at least one such ion.

Claims

1. A method of performing ionization, comprising:

providing a pair of trapping plates located within a chamber,

wherein the pair of trapping plates define a first end and a second end of a cell, the first end trapping plate comprising at least one opening allowing passage of ions therethrough, and

introducing an analyte into the chamber, wherein a partial pressure of the analyte after its introduction into the chamber is between about 1×

10<sup>−

3</sup> torr and about 1×

10<sup>−

12</sup> torr; and

applying a radio frequency (RF) signal to an ion guide assembly comprising at least one ion guide rod, wherein the ions are formed in a gap between an exposed end of the at least one ion guide rod and the first end trapping plate.

2. The method of claim 1, further comprising detecting the ions with a mass spectrometer (MS).

3. The method of claim 2, wherein the MS is selected from the group consisting of:

a quadrupole MS, a sector (electric and magnetic) instrument, a Fourier Transform Ion Cyclotron Resonance (FT-ICR) MS, a Time of Flight (TOF) MS, and an Orbitrap MS.

4. The method of claim 1, wherein a frequency of the RF signal is between about 1.0 MHz to about 100 MHz.

5. The method of claim 1, wherein the gap between the exposed end of the at least one ion guide rod and the first end trapping plate is between about 0.1 nm and about 4 mm.

6. The method of claim 1, wherein the analyte comprises one or more chemical compounds.

7. The method of claim 1, wherein the analyte is or comprises a gas.

8. The method of claim 1, wherein the analyte is or comprises a liquid.

9. The method of claim 1, wherein the analyte is or comprises a solid.

10. The method of claim 1, wherein the step of applying comprises applying radio frequency energy to the analyte for between about 0.001 second and about 3.0 seconds, inclusive.

11. The method of claim 1, wherein the at least one opening is located off-axis of a central axis that is longitudinally parallel with the at least one ion guide rod of the ion guide assembly.

12. The method of claim 2, further comprising:

positioning a wire ion guide between the first and second end trapping plates inside the cell, wherein the wire ion guide is electrically isolated from the cell; and

applying a voltage to the wire ion guide during ion excitation and detection.

13. The method of claim 12, wherein the wire is copper, silver, and/or gold.

14. The method of claim 12, wherein the voltage is pulsed.

15. An ionization system, comprising:

a source of radio frequency (RF) energy for providing power for production of ions;

a chamber;

a pair of trapping plates located within the chamber, wherein the pair of trapping plates define a first end and a second end of a cell, the first end trapping plate comprising at least one opening allowing passage of ions therethrough;

an ion guide assembly comprising at least one ion guide rod, wherein the ions are formed in a gap between an exposed end of the at least one ion guide rod and the first end trapping plate; and

a wire ion guide positioned between a center of the end trapping plates in the cell, wherein the wire ion guide is electrically isolated from the cell.

16. The system of claim 15, wherein the gap between the exposed end of the at least one ion guide rod and the first end trapping plate is between about 0.1 nm and about 4 mm.

17. The system of claim 15, further comprising a mass spectrometer (MS).

18. The system of claim 17, wherein the mass spectrometer is selected from the group consisting of a quadrupole MS, a sector (electric and magnetic) instrument, a Fourier Transform Ion Cyclotron Resonance (FT-ICR) MS, a Time of Flight (TOF) MS, and an Orbitrap MS.

19. The system of claim 15, wherein the source of RF energy is located in the chamber.

20. The system of claim 15, wherein the at least one opening is located off-axis of a central axis that is longitudinally parallel with the at least one ion guide rod of the ion guide assembly.

21. The system of claim 15, wherein the wire is copper.

22. The system of claim 15, further comprising an aperture for introducing an analyte.

23. The system of claim 15, wherein the at least one opening has a diameter between about 1 nm and about 1.0 cm.