Two-dimensional mass spectrometry using ion micropacket detection
The invention generally relates to two-dimensional mass spectrometry using ion micropacket detection. In certain aspects, the invention provides systems including a mass spectrometer having an ion trap and one or more detectors. The system includes a central processing unit (CPU), and storage coupled to the CPU for storing instructions that when executed by the CPU cause the system to: apply one or more scan functions to the ion trap that excite a precursor ion and eject a product ion from the ion trap; and determine a secular frequency of the product ion by detecting micropackets of the product ion as the micropackets are ejected from the ion trap.
1. A system comprising:
a mass spectrometer comprising an ion trap and one or more detectors; and
a central processing unit (CPU), and storage coupled to the CPU for storing instructions that when executed by the CPU cause the system to:
apply one or more scan functions to the ion trap that excite a precursor ion and eject a product ion from the ion trap; and
determine a secular frequency of the product ion or a harmonic thereof by detecting micropackets of the product ion as the micropackets are ejected from the ion trap.
2. The system of claim 1 , wherein the one or more scan functions are applied in a manner that precursor and product ions are correlated without isolation of the precursor ions.
3. The system of claim 1 , wherein the one or more scan functions that excite the precursor ion comprise a nonlinear frequency sweep at a constant rf voltage or the one or more scan functions that excite the precursor ion comprise a fixed frequency excitation while the rf amplitude is ramped linearly.
4. The system of claim 3 , wherein the one or more scan functions that eject a product ion from the ion trap comprise a broadband waveform.
5. The system of claim 1 , wherein a fast Fourier transform of a mass spectral peak recovers the secular frequency of the product ion or a harmonic thereof.
6. The system of claim 1 , wherein the system comprises two detectors and a fast Fourier transform of a mass spectral peak recovers twice the secular frequency of the product ion.
7. The system of claim 1 , wherein a rate of appearance of the micropackets at the one or more detectors corresponds to an excitation frequency of the product ion.
8. The system of claim 1 , wherein the instructions that when executed by the CPU cause the system to eject the micropackets at regularly spaced intervals.
9. The system of claim 1 , wherein the ion trap is pressurized with helium, nitrogen, carbon dioxide, or air.
10. The system of claim 1 , wherein the ion trap is a quadrupole ion trap and excitation and ejection signals can be on a same pair of quadrupole electrodes or on orthogonal electrode pairs.
11. The system of claim 1 , further comprising an ionization source.
12. The system of claim 1 , wherein dissociation of the precursor ion is caused by a technique selected from the group consisting of: collision-induced dissociation, surface-induced dissociation, infrared multiphoton dissociation, ultraviolet photodissociation, electron capture dissociation, and electron transfer dissociation.
13. A method for operating a mass spectrometer, the method comprising:
applying one or more scan functions to an ion trap of a mass spectrometer that excite a precursor ion and eject a product ion from the ion trap; and
determining a secular frequency of the product ion by detecting micropackets of the product ion as the micropackets are ejected from the ion trap.
14. The method of claim 13 , wherein the one or more scan functions are applied in a manner that precursor and product ions are correlated without isolation of the precursor ions.
15. The method of claim 13 , wherein the one or more scan functions that excite the precursor ion comprise a nonlinear frequency sweep at a constant rf voltage or the one or more scan functions that excite the precursor ion comprise a fixed frequency excitation while the rf amplitude is ramped linearly.
16. The method of claim 15 , wherein the one or more scan functions that eject a product ion from the ion trap comprise a broadband waveform.
17. The method of claim 13 , wherein a fast Fourier transform of a mass spectral peak recovers the secular frequency of the product ion or a harmonic thereof.
18. The method of claim 13 , wherein the determining step utilizes two detectors and a fast Fourier transform of a mass spectral peak recovers twice the secular frequency of the product ion.
19. The method of claim 13 , wherein a rate of appearance of the micropackets at the one or more detectors corresponds to an excitation frequency of the product ion.
20. The method of claim 13 , wherein the micropackets are ejected at regularly spaced intervals.