Acquisition of fragment ion mass spectra of ions separated by their mobility

Patent metadata

Field	Value
Publication number	US-9891194-B2
Application number	US-201514931163-A
Country	US
Kind code	B2
Filing date	Nov 3, 2015
Priority date	Nov 3, 2015
Publication date	Feb 13, 2018
Grant date	Feb 13, 2018

Abstract

The invention provides a method for acquiring fragment ion spectra of substances in complex substance mixtures wherein a trapped ion mobility spectrometer (“TIMS”) is used as the ion mobility separator separation device. The fragment ion spectra may be used for the identification of high numbers of proteins in complex mixtures, or for a safe quantification of some substances, by their fragment ion mass spectra in a mass spectrometer with up-front substance separator. TIMS with parallel accumulation provides the unique possibility to prolong the ion accumulation duration to find more detectable ion species without decreasing the measuring capacity for fragment ion mass spectra. The high measurement capacity for fragment ion mass spectra permits the repeated measurement of low abundance ion species to improve the quality of the fragment ion spectra.

First claim

The invention claimed is:

1. A multi-cycle method to acquire fragment ion spectra of substances in complex substance mixtures by a mass spectrometer with an ion source, an ion mobility separator, a mass filter, an ion fragmentation cell, and a mass analyzer, wherein in a first measurement cycle a map of ion species with ion mobility scan times versus ion masses is measured, from which several sets of temporally separated ion species with distinct masses and distinct mobility scan times can be selected, and wherein in further measurement cycles the ion species of a set each are selected by their mobility scan time, filtered by mass in the mass filter, and fragmented in the fragmentation cell, and wherein the fragment ion mass spectra are measured by the mass analyzer, characterized by the fact that a trapped ion mobility spectrometer (TIMS) is used as ion mobility separator, wherein the separator is operated in a parallel accumulation mode in which ions are provided from the ion source to the separator during a measurement cycle in an accumulator unit of the separator at a rising edge of an electric field barrier such that the ions are spatially separated by their ion mobility along the rising edge.

2. The multi-cycle method according to claim 1 , wherein the ion accumulation durations of the separator are adapted to obtain a predetermined number of detectable ion species in the map.

3. The multi-cycle method according to claim 2 , wherein the ion mobility scan durations substantially equal the ion accumulation durations.

4. The multi-cycle method according to claim 2 , wherein a spatial zoom mode is applied to enlarge the number of detectable ion species and to increase the ion mobility resolution by choosing selected ranges of ion mobility.

5. The multi-cycle method according to claim 4 , wherein the ion mobility ranges of the spatial zoom are adapted to the ion mobility distribution of the ion species generated from the substance mixture.

6. The multi-cycle method according to claim 1 , wherein the fragment ion mass spectra of selected ion species are measured repeatedly in subsequent measurement cycles to improve their spectrum quality.

7. The multi-cycle method according to claim 6 , wherein the repetitive measurement of further fragment ion mass spectra of the same ion species is ended when a predefined quality is obtained or when the ion species is identified in a database search using the fragment ion spectra.

8. The multi-cycle method according to claim 6 , wherein an up-front chromatograph is used to separate substances, and wherein the repetitive measurements of fragment ion mass spectra of the same selected ion species is continued to measure the ion species over a full peak of the chromatogram for accurate quantification of selected substances.

9. The multi-cycle method according to claim 8 , wherein the selected ion species is a reporter ion split from a substance chemically labeled with a mass tag.

10. The multi-cycle method according to claim 1 , wherein a second mass-mobility map for a second measurement loop is measured when a predetermined time interval is over, when a predetermined number of fragment ion spectra is acquired or when the present mass-mobility map essentially does no longer offer sufficient unmeasured ion species to be selected.

11. The multi-cycle method according to claim 10 , wherein the mobility range of the second mass-mobility map differs from the mobility range of the first mass-mobility map.

12. The multi-cycle method according to claim 10 , wherein the ion accumulation duration of the second mass-mobility map differs from the ion accumulation duration of the first mass-mobility map.

13. The multi-cycle method according to claim 12 , wherein the ion accumulation duration of the second mass-mobility map is increased compared to the ion accumulation duration of the first mass-mobility map in order to obtain more detectable ion species.

14. The multi-cycle method according to claim 1 , operating on substance mixtures delivered from an up-front substance separator, such as a liquid chromatograph or a capillary electrophoresis unit.

15. The multi-cycle method according to claim 1 , wherein a time-of-flight mass analyzer with orthogonal ion injection (OTOF) is used as mass analyzer.

16. The multi-cycle method according to claim 1 , wherein the mass filter comprises an RF quadrupole mass filter.

17. The multi-cycle method according to claim 16 , wherein the ion mobility scan is interrupted during the switching time of the RF quadrupole mass filter.

18. The multi-cycle method according to claim 1 , wherein two or more fragment ion spectra are measured for at least one ion species in different measurement cycles and added together to improve the quality of the fragment ion spectra or a sum spectrum thereof.

19. The multi-cycle method according to claim 18 , wherein the measurement of the fragment ion mass spectra of the at least one ion species is ended when a predefined quality of the spectrum is obtained or when the selected ion species is identified in a database search using the fragment ion spectra.

20. The multi-cycle method according to claim 1 , wherein the selected ion species is a reporter ion split from a substance chemically labeled with a mass tag.

21. The multi-cycle method according to claim 16 , wherein the RF quadrupole mass filter is switched to the mass of the ion species to be measured next in such a way that the transmission through the mass filter first is closed, then tuned to the next mass, and then opened again.

22. The multi-cycle method according to claim 16 , wherein the quadrupole mass filter is switched from the mass of a preceding ion species to the next ion species of a set in such a way that the mass of the next ion species is lower than the mass of the preceding ion species.

23. The multi-cycle method according to claim 15 , wherein the time needed for acquiring the fragment ion spectrum of one of the selected ion species is approximately 2.5 milliseconds or less.

Assignees

• Mann Matthias
• Raether Oliver
• Park Melvin Andrew
• Lubeck Markus
• Bruker Daltonik Gmbh

Inventors

• Mann Matthias
• Raether Oliver
• Park Melvin Andrew
• Lubeck Markus

Classifications

• H01J49/4215

  Quadrupole mass filters (H01J49/4225 takes precedence) · CPC title

• H01J49/0031 Primary

  Step by step routines describing the use of the apparatus (H01J49/0081 takes precedence) · CPC title

• G01N27/622 Primary

  Ion mobility spectrometry · CPC title

• G01N33/483

  Physical analysis of biological material · CPC title

• G01N30/7266

  by electric field, e.g. electrospray · CPC title