# US 11,994,491 B2 · Method and apparatus for identifying substances using ion mobility based ion separation techniques

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- Number: US 11,994,491 B2
- Document ID: US11994491B2
- Status: Granted
- Kind: B2
- Application number: 17/264,504
- Filed: 2019-07-26
- Published: 2021-09-23
- Granted: 2024-05-28
- Earliest claimed: 2018-07-31
- Assignees: Smiths Detection-Watford Limited
- Applicants: Smiths Detection-Watford Limited
- Inventors: Jonathan Richard Atkinson; Alastair Clark
- Web page: https://patentgrep.com/patent/US11994491B2

## CPC

- G01N 27/622: Ion mobility spectrometry
- G01N 27/623: combined with mass spectrometry
- G01N 27/333: Ion-selective electrodes or membranes (glass electrodes G01N27/36)
- G01N 27/4035: {Combination of a single ion-sensing electrode and a single reference electrode (G01N27/406 and G01N27/413 take precedence)}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

An ion mobility spectrometry method comprising (i) applying a voltage difference between a first electrode of an ion gate and a second electrode of the ion gate to prevent ions from leaving a reaction region of an ion mobility spectrometer; (ii) opening the ion gate to allow the ions to travel from the reaction region into a modification region between the first electrode and the second electrode; (iii) applying a radio frequency, RF, voltage between the first electrode and the second electrode to fragment the ions in the modification region to provide daughter ions; (iv) allowing the daughter ions to travel from the modification region into a drift region of the ion mobility spectrometer towards a collector; (v) closing the ion gate; and (vi) determining the time of flight of the daughter ions from the ion gate to the collector.

## Claims

### Claim 1

An ion mobility spectrometry method comprising:
(i) applying a voltage difference between a first electrode of an ion gate and a second electrode of the ion gate to prevent ions from leaving a reaction region of an ion mobility spectrometer;
(ii) opening the ion gate to allow the ions to travel from the reaction region into a modification region between the first electrode of the ion gate and the second electrode of the ion gate;
(iii) applying a radio frequency, RF, voltage between the first electrode of the ion gate and the second electrode of the ion gate to fragment the ions in the modification region to provide daughter ions;
(iv) allowing the daughter ions to travel from the modification region into a drift region of the ion mobility spectrometer towards a collector;
(v) closing the ion gate; and
(vi) determining the time of flight of the daughter ions from the ion gate to the collector.

### Claim 2 (depends on 1)

The method of claim 1 wherein comprising applying a voltage profile for moving the ions from the reaction region to the collector, wherein (ii) opening the gate comprises applying a DC voltage difference between the first electrode and the second electrode which matches the voltage profile.

### Claim 3 (depends on 2)

The method of claim 2 wherein the first electrode is spaced apart from the second electrode in a drift direction of the ion mobility spectrometer.

### Claim 4 (depends on 3)

The method of claim 3 wherein the first electrode separates the second electrode from the reaction region, and the voltage difference comprises a voltage which matches the voltage profile at the second electrode.

### Claim 5 (depends on 4)

The method of claim 4 wherein applying the voltage difference comprises providing an electric field between the first electrode and the second electrode, which electric field opposes the voltage profile.

### Claim 6 (depends on 2)

The method of claim 2 wherein the radio frequency voltage is superimposed on the DC voltage difference.

### Claim 7 (depends on 1)

The method of claim 1 further comprising:
prior to steps (ii) to (vi), opening the gate to allow a preceding packet of ions to travel from the reaction region into the drift region and towards the collector, closing the gate, and determining the time of flight of the preceding packet of ions from the ion gate to the collector.

### Claim 8 (depends on 7)

The method of claim 7 wherein the ions and the preceding packet of ions are obtained from the same sample, the method comprising identifying the presence of a substance of interest in the sample based on the time of flight of the daughter ions and the time of flight of the preceding packet of ions.

### Claim 9

An ion mobility spectrometer comprising:
a reaction region,
a drift region, comprising a voltage profile along which ions travel in a drift direction from the reaction region to a collector;
an ion gate comprising a first electrode and a second electrode; and
a gate voltage controller configured to:
apply a voltage difference between the first electrode of the ion gate and the second electrode of the ion gate to prevent ions from leaving the reaction region;
open the ion gate to allow the ions to travel from the reaction region into a modification region between the first electrode of the ion gate and the second electrode of the ion gate;
apply a radio frequency voltage between first electrode of the ion gate and the second electrode of the ion gate to fragment ions in the modification region to provide daughter ions;
to allow the daughter ions to pass from the modification region and into the drift region; and
to close the ion gate by applying the voltage difference between the first electrode of the ion gate and the second electrode of the ion gate;
wherein the ion mobility spectrometer is configured to determine the time of flight of the daughter ions from the ion gate through the drift region to the collector.

### Claim 10 (depends on 9)

The ion mobility spectrometer of claim 9 wherein the first electrode and the second electrode each comprise a plurality of elongate conductors, and the elongate conductors of the first electrode are each aligned, in a direction transverse to the drift direction, with a corresponding elongate conductor of the second electrode.

### Claim 11 (depends on 9)

The ion mobility spectrometer of claim 9 wherein the first electrode separates the second electrode from the reaction region, and the voltage difference comprises a voltage which matches the voltage profile at the second electrode.

### Claim 12 (depends on 11)

The ion mobility spectrometer of claim 11 wherein applying the voltage difference comprises providing an electric field between the first electrode and the second electrode which opposes the voltage profile.

### Claim 13 (depends on 9)

The ion mobility spectrometer of claim 9 wherein opening the gate comprises applying a DC voltage difference between the first electrode and the second electrode which matches the voltage profile.

### Claim 14 (depends on 13)

The ion mobility spectrometer of claim 13 wherein the RF voltage is superimposed on the DC voltage difference.

### Claim 15

A method of controlling an ion gate in an ion mobility spectrometer, the method comprising:
applying a voltage difference between two electrodes of the ion gate to prevent ions from leaving a reaction region of the ion mobility spectrometer, and
opening the gate, and while the gate is open applying an RF voltage between the same two ion gate electrodes to fragment ions as they pass through the gate.

### Claim 16 (depends on 15)

The method of claim 15 wherein the two electrodes each comprise a plurality of mutually coplanar elongate conductors and the two electrodes are spaced apart in the drift direction.

### Claim 17 (depends on 16)

The method of claim 16 wherein the elongate conductors of a first of the electrodes are each aligned, in a direction transverse to the drift direction, with a corresponding elongate conductor of a second of the two electrodes.

### Claim 18 (depends on 16)

The method of claim 16 wherein the first electrode separates the second electrode from the reaction region and applying the voltage difference comprises applying a voltage to the second electrode which matches the voltage profile.

### Claim 19 (depends on 16)

The method of claim 16 wherein opening the gate comprises applying a DC voltage difference between the two electrodes which matches a voltage profile of the ion mobility spectrometer, and the radio frequency voltage is superimposed on the DC voltage difference.