Method and apparatus for analyzing samples using mass spectrometry

Patent metadata

Field	Value
Publication number	US-11004669-B2
Application number	US-201616063104-A
Country	US
Kind code	B2
Filing date	Dec 15, 2016
Priority date	Dec 17, 2015
Publication date	May 11, 2021
Grant date	May 11, 2021

Abstract

A method and apparatus for analyzing samples using mass spectrometry are disclosed. The apparatus includes a reaction device configured to dissociate sample ions into fragments by reacting the sample ions with a charged species (e.g., electrons) such as through ECD, EID, or EIEIO. The kinetic energy of the charged species is such that the fragments may be detected and produce spectra that allow for the determination of isomeric species in the sample and the location of double bonds and/or the orientation of those double bonds within the sample molecules. The fragments may include radical fragments and non-radical fragments. Spectra resulting from analysis of the fragments may allow for the determination of the oxygen-radical fragments resulting from the dissociation of the sample molecules as confirmation of the presence of those radical fragments.

First claim

What is claimed is:

1. A method for analyzing a sample containing at least one carbon-carbon double-bond containing lipid using a mass spectrometer, the method comprising:
ionizing the sample to form a plurality of precursor ions,
fragmenting at least a portion of the plurality of precursor ions into a plurality of fragment ions by irradiating the plurality of precursors ions with electrons; wherein the dissociation reaction is configured to allow distinguishing mass signatures of two isomeric species of said at least one carbon-carbon double-bond containing lipid; and
detecting at least a portion of the plurality of fragment ions at a detector of the mass spectrometer to form at least one spectrum for mass analysis of the sample, and wherein peak intensities associated with the plurality of fragment ions in said at least one spectrum is used to indicate the cis/trans orientation of said at least one carbon-carbon double bond.

2. The method of claim 1 wherein said electrons have a kinetic energy of about 4 electron volts to about 12 electron volts.

3. The method of claim 1 wherein the peak intensities associated with the plurality of fragment ions are characteristic of a carbon-carbon single bond situated next to said carbon-carbon double-bond.

4. The method of claim 3 wherein the carbon-carbon single bond is situated at a position +1 to the location of the carbon-carbon double bond along a carbon chain of said lipid.

5. The method of claim 3 wherein the peak intensities associated with the plurality of fragment ions comprise a first peak characteristic of non-radical species and a second peak characteristic of a radical fragment species.

6. The method of claim 5 wherein said first peak and said second peak are separated by about 1 Dalton in said spectrum.

7. The method of claim 6 wherein a ratio of said first peak to said second peak is determined and said ratio is used to indicate the cis/trans orientation of said at least one carbon-carbon double bond.

8. The method of claim 7 wherein said ratio is compared to a standard ratio, wherein said standard ratio is obtained by analyzing a standard sample utilizing the same method utilized to calculate said ratio with the exception that said standard sample comprises a lipid species that consists essentially of either a pure cis or pure trans form of said double-bond containing lipid.

9. The method of claim 8 wherein a relative abundance of cis and trans double bonds present in said sample is determined based on said ratio and said standard ratio.

10. The method of claim 1 wherein said plurality of precursor ions are single-charged species.

11. The method of claim 1 wherein the lipid is selected from the group of triacylglycerols and wherein said lipid is complexed with an alkali metal salt prior to ionization.

12. The method of claim 11 wherein the lipid is complexed with an alkali metal salt in a solution of dichloromethane and methanol and optionally wherein the dichloromethane and methanol are mixed in a 50:50 solution by volume.

13. The method of claim 12 wherein the alkali metal salt is a sodium salt and preferably sodium acetate.

14. A system for analyzing a sample containing a carbon-carbon double-bond-containing lipid comprising:
a mass spectrometer comprising an ion-electron reaction device and a mass analyzer;
a processor in communication with the mass spectrometer configured to:
instruct the ion-election reaction device to conduct an ion-electron reaction between an ionized lipid containing a carbon-carbon double bond and electrons that causes the production of two or more product ions;
receive an intensity for each of the two or more product ions from the mass spectrometer;
identifies a grouping of the two or more product ions and their associated intensities that is characteristic of a carbon-carbon single bond situated next to said carbon-carbon double bond, at least one or the two or more product ions being characteristic of a non-radical species and another of the two or more product ions being characteristic of a radical species;
determines a ratio of the intensities of said non-radical species to said radical species; and
determines the cis/trans orientation of the carbon-carbon double bond based on said ratio.

15. The system of claim 14 wherein the processor identifies a grouping of two or more product ions and their associated intensities that is characteristic of a carbon-carbon double bond, at least one of these characteristic double-bond intensities corresponding to a double-bond radical fragment.

16. The system of claim 15 wherein the double-bond radical fragment and the radical species are separated by 12 Daltons.

17. The system of claim 14 wherein the ionized lipid is singly charged.

18. The system of claim 14 wherein the ionized lipid is doubly charged.

19. A method for analyzing a sample containing or suspected of containing at least one lipid using a mass spectrometer, the lipid being selected from the group of sphingomyelins, the method comprising:
ionizing the sample to form a plurality of precursor ions;
performing an electron-ion reaction to fragment at least a portion of the plurality of precursor ions into a plurality of product ions,
detecting at least a portion of the plurality of product ion species at a detector of the mass spectrometer to form at least one spectrum for mass analysis of the sample and determining the presence of at least one sphingomyelin species in said sample by identifying in said spectrum, diagnostic peaks situated at about m/z 184.075 and about m/z 225.100 or at about m/z 184.075, about m/z 225.100 and about m/z 253.095.

20. The method of claim 19 wherein a DMS separation is performed between the steps of ionizing of the sample and the electron-ion reaction.

Assignees

• Dh Technologies Dev Pte Ltd

Inventors

• Baba Takashi
• Baker Paul
• Campbell John Lawrence
• Le Blanc Yves

Classifications

• G01N33/6848

  Methods of protein analysis involving mass spectrometry · CPC title

• H01J49/0072 Primary

  by ion/ion reaction, e.g. electron transfer dissociation, proton transfer dissociation · CPC title

• H01J49/0054 Primary

  by an electron beam, e.g. electron impact dissociation, electron capture dissociation · CPC title

• G01N33/92

  involving lipids, e.g. cholesterol {, lipoproteins, or their receptors (steroid hormones G01N33/743)} · CPC title