Ion modification

• US 10,910,207 B2
• Filed: 09/12/2019
• Issued: 02/02/2021
• Est. Priority Date: 08/23/2013
• Status: Active Grant

• Current Assignee: Smiths Detection-Watford Ltd.
• Original Assignee: Smiths Detection-Watford Ltd.
• Inventors: Atkinson, Jonathan, Clark, Alastair, Grant, Bruce
• Primary Examiner(s): Stoffa, Wyatt A
• Application Number:
  US16/568,987
• Publication Number:
  US 20200083033A1
• Time in Patent Office: 509 Days
• CPC Class Codes: G01N 27/622 Ion mobility spectrometry
• CPC Class Codes: H01J 49/0045 characterised by the fragmentation or other specific reaction
• CPC Class Codes: H01J 49/061 Ion deflecting means, e.g. ion gates

Abstract

An ion mobility spectrometer comprising an ioniser for ionising a sample; a detector separated from the ioniser by a drift chamber along which ions can travel from the ioniser toward the detector; a gate for controlling the passage of ions from the ioniser to the drift chamber; an ion modifier arranged between the ioniser and the detector and comprising a first electrode and a second electrode; and a voltage provider configured to provide a time varying voltage between the first electrode and the second electrode wherein the time varying voltage has a frequency of at least 2.5 MHz.

Claims

1. An ion mobility spectrometer comprising:

an ioniser for ionising a sample to provide parent ions;

a detector separated from the ioniser by a drift chamber along which the parent ions can travel from the ioniser toward the detector, the parent ions each having a time of flight to the detector;

an ion modifier arranged between the ioniser and the detector, the ion modifier comprising a first electrode and a second electrode; and

a voltage provider configured to provide a time varying voltage between the first electrode and the second electrode to provide additional information to be used to infer an identity of the parent ions by fragmenting the parent ions in a region between the first electrode and the second electrode to provide daughter ions, each daughter ion having a different time of flight than its respective parent ion, wherein the time varying voltage has a frequency of at least 2.5 MHz, wherein the time varying voltage comprises varying voltages of equal amplitude provided to the first electrode and the second electrode, wherein the voltage provided to the second electrode is out of phase with the voltage provided to the first electrode.

2. The ion mobility spectrometer of claim 1 wherein the ioniser is arranged in an ionisation chamber that is separated from the drift chamber by a gate.

3. The ion mobility spectrometer of claim 2 wherein the ion modifier is arranged in one of the drift chamber and the ionisation chamber.

4. The ion mobility spectrometer of claim 3 comprising a drift gas inlet and a drift gas outlet arranged to provide a flow of drift gas along the drift chamber and through the ion modifier.

5. The ion mobility spectrometer of claim 1 wherein the voltage provider is configured to vary the voltage of the second electrode more quickly than the voltage of the first electrode.

6. The ion mobility spectrometer of claim 1 wherein the first electrode and the second electrode are spaced apart in the direction of travel of the ions, and the voltage provider is configured to hold the voltage of the first electrode at a voltage selected according to a voltage profile that moves the ions from the ioniser towards the detector and the location of the first electrode along the voltage profile.

7. The ion mobility spectrometer of claim 1 wherein at least one of the first electrode or the second electrode comprises conductors arranged across the direction of travel of the ions.

8. The ion mobility spectrometer of claim 7 wherein at least one of the first electrode or the second electrode comprises a mesh.

9. The ion mobility spectrometer of claim 1, wherein the first electrode and the second electrode are spaced apart in the direction of travel of the ions.

10. The ion mobility spectrometer of claim 9, wherein the spacing between the first electrode and the second electrode is less than 0.4 mm.

11. The ion mobility spectrometer of claim 1, wherein the spectrometer is configured to (i) measure ions'"'"' time of flight to the detector when the ion modifier electrodes are operated to fragment the parent ions;

and (ii) measure ions'"'"' time of flight to the detector when the ion modifier electrodes are not operated to fragment the parent ions.

12. An ion mobility spectrometer comprising:

an ioniser for ionising a sample to provide parent ions;

a detector separated from the ioniser by a drift chamber along which the parent ions can travel from the ioniser toward the detector, the parent ions each having a time of flight to the detector;

an ion modifier arranged between the ioniser and the detector, the ion modifier comprising a first electrode and a second electrode; and

a voltage provider configured to provide a time varying voltage between the first electrode and the second electrode to provide additional information to be used to infer an identity of the parent ions by fragmenting the parent ions in a region between the first electrode and the second electrode to provide daughter ions, each daughter ion having a different time of flight than its respective parent ion, wherein the time varying voltage has a frequency of at least 2.5 MHz, wherein the voltage provider is configured to vary the voltage of the first electrode less than the voltage of the second electrode.

13. A method of modifying parent ions in an ion mobility spectrometer to provide additional information to be used to infer an identity of the parent ions, the method comprising:

allowing parent ions to be moved from an ioniser towards a detector, the parent ions each having a time of flight to the detector; and

subjecting a region in the spectrometer to a time varying electric field to fragment the parent ions to provide daughter ions, each daughter ion having a different time of flight than its respective parent ion, wherein the parent ions pass through the region toward the detector from a first side of the region to a second side of the region, and the time varying electric field varies with a frequency of at least 2.5 MHz, wherein the time varying voltage comprises varying voltages of equal amplitude provided to the first electrode and the second electrode, wherein the voltage provided to the second electrode is out of phase with the voltage provided to the first electrode.

14. The method of claim 13, wherein the first side of the region and the second side of the region are separated by less than 0.4 mm.

15. The method of claim 13 comprising measuring ions'"'"' time of flight to the detector when the ion modifier electrodes are not operated to fragment the parent ions;

and measuring ions'"'"' time of flight to the detector when the ion modifier electrodes are operated to fragment the parent ions.