Differential Mobility Spectrometry Method

• US 20180003675A1
• Filed: 12/16/2015
• Published: 01/04/2018
• Est. Priority Date: 12/31/2014
• Status: Active Grant

• Current Assignee: DH Technologies Development Pte. Ltd. (Danaher Corporation)
• Original Assignee: DH Technologies Development Pte. Ltd. (Danaher Corporation)
• Inventors: CAMPBELL, John Lawrence, LE BLANC, Yves
• Granted Patent: US 10,345,261 B2
• Time in Patent Office: Days
• CPC Class Codes: G01N 27/624 Differential mobility spectrometry [DMS]; Field asymmetric-waveform ion mobility spectrometry [FAIMS]
• CPC Class Codes: H01J 49/004 Combinations of spectrometers, tandem spectrometers, e.g. MS/MS, MSn

Abstract

Methods and systems are provided herein for varying the CoV about a nominal CoV-apex while monitoring the ion of interest corresponding to the nominal CoV-apex as it is transmitted by a DMS. In various aspects, the CoV can be swept or stepped across a series of values during the injection of ions into the DMS such that a composite spectra of the ion of interest transmitted by the DMS (or its product ions following one or more stages of fragmentation) can be generated so as to include the transmission of the particular ion at a CoV with optimum sensitivity (i.e., if distinct from the CoV-apex), thereby improving the robustness, accuracy, and/or selectivity during experimental conditions relative to known DMS techniques, which typically used a fixed CoV value for each ion of interest.

Claims

1. A method of operating a system comprising a differential mobility spectrometer, the method comprising:

(a) injecting a stream of ions into a differential mobility spectrometer during a first duration, the stream of ions containing or suspected of containing an ion species of interest;

(b) determining a compensation voltage apex for the ion species of interest in the differential mobility spectrometer;

(c) varying the compensation voltage applied to the differential mobility spectrometer over a range about the determined compensation voltage apex during said first duration;

(d) detecting the ion species of interest transmitted by the differential mobility spectrometer during said first duration.

2. The method of claim 1, wherein the compensation voltage apex represents a nominal optimum for transmission of the ion species of interest based on operating conditions of the differential mobility spectrometer, optionally wherein the nominal optimum is provided by a look-up table.

3. The method of claim 1, wherein the compensation voltage apex for the ion species of interest is determined based on a theoretical optimum transmission compensation voltage.

4. The method of claim 1, wherein said range about the compensation voltage apex comprises a range between a first compensation voltage value less than said compensation voltage apex and a second compensation voltage value greater than said compensation voltage apex.

5. An apparatus for analyzing ions comprising:

an ion source configured to generate ions from a sample containing or suspected of containing an ion species of interest;

a differential mobility spectrometer configured to receive the plurality of ions from the ion source and transmit one or more ions species based on the differential mobility of the ion species therein;

a detector for detecting the ion species transmitted by the differential mobility spectrometer; and

a controller operatively coupled to the ion source, the differential mobility spectrometer, and the detector, and configured to;

cause the ion source to inject a stream of ions into the differential mobility spectrometer during a first duration;

determine a compensation voltage apex for the ion species of interest in the differential mobility spectrometer;

vary the compensation voltage applied to the differential mobility spectrometer over a range about the determined compensation voltage apex during said first duration; and

detect the ion species of interest transmitted by the differential mobility spectrometer during said first duration.

6. The apparatus of claim 5, wherein the compensation voltage apex represents a nominal optimum for transmission of the ion species of interest based on operating conditions of the differential mobility spectrometer.

7. The apparatus of claim 5, further comprising data storage associated with the controller, wherein the data storage is configured to store compensation voltage apex for one or more ion species under operating conditions of the differential mobility spectrometer.

8. The apparatus of claim 5, wherein the compensation voltage apex for the ion species of interest is selected based on a theoretical optimum transmission compensation voltage.

9. The apparatus of claim 5, wherein said range about the compensation voltage apex comprises a range between a first compensation voltage value less than said compensation voltage apex and a second compensation voltage value greater than said compensation voltage apex.

10. The apparatus of claim 9, wherein the controller is configured to discretely vary, in stepwise fashion, the compensation voltage applied to the differential mobility spectrometer between the first compensation value and the second compensation value.

11. The apparatus of claim 9, wherein the controller is configured to continuously vary the compensation voltage applied to the differential mobility spectrometer between the first compensation value and the second compensation value.

12. The apparatus of claim 5, wherein said range about the compensation voltage apex is predetermined.

13. The apparatus of claim 12, wherein said range represents ±

1.0V of the compensation voltage apex, optionally wherein the compensation voltage is varied in stepwise increments of 0.1V.

14. The apparatus of claim 5, further comprising an input device configured to receive an input from a user regarding the compensation voltage apex, optionally wherein the input device is configured to receive an input from the user of said range about said compensation voltage apex.

15. The apparatus of claim 5, wherein said range is determined through a user-selected deviation from the compensation voltage apex.

16. The apparatus of claim 5, further comprising a fragmentor disposed between the differential mobility spectrometer and the detector, wherein the fragmentor is configured to fragment the ions transmitted by the differential mobility spectrometer, and wherein the detector is configured to detect the ion species of interest by detecting one or more fragments of the ion species of interest.

17. The apparatus of claim 15, wherein the controller is configured to calculate the m/z for each fragment detected by the detector and optionally wherein the controller is configured to generate a mass spectrum corresponding to the ion fragment m/z data during said first duration.

18. The apparatus of claim 16, wherein the fragmentor comprises a collision cell wherein beam-type fragmentation is implemented.

19. The apparatus of claim 16, wherein the fragmentor comprises a collision cell wherein resonance excitation for fragmentation is implemented.

20. The apparatus of claim 5, further comprising a drift gas supply for providing a drift gas for flowing through the differential mobility spectrometer and a modifier liquid supply for supplying a modifier liquid to the drift gas.