Systems and Methods for Ion Isolation

Patent metadata

Field	Value
Publication number	US-2016336164-A1
Application number	US-201514709387-A
Country	US
Kind code	A1
Filing date	May 11, 2015
Priority date	May 11, 2015
Publication date	Nov 17, 2016
Grant date	—

Abstract

A mass spectrometer includes a radio frequency ion trap and a controller. The controller is configured to cause an ion population to be injected into the radio frequency ion trap and supply an isolation waveform to the radio frequency ion trap. The isolation waveform has at least one notch at a target mass-to-charge ratio and a frequency profile determined to eject unwanted ions at a plurality of frequencies in a substantially similar amount of time.

First claim

1 . A mass spectrometer comprising:
a radio frequency ion trap; and a controller configured to:
cause an ion population to be injected into the radio frequency ion trap; and
supply an isolation waveform to the radio frequency ion trap, the isolation waveform having at least one notch at a target mass-to-charge ratio, the isolation waveform having a frequency profile determined to eject unwanted ions at a plurality of frequencies in a substantially similar amount of time.

2 . The mass spectrometer of claim 1 , wherein the frequency profile is determined by applying a waveform with flat frequency profile to calibrant ions in the radio frequency ion trap and identifying an amplitude required to eject ions at a plurality of mass-to-charge ratios.

3 . The mass spectrometer of claim 1 , wherein the controller is further configured to apply a time domain waveform amplitude gain to the isolation waveform.

4 . The mass spectrometer of claim 3 , wherein the time domain waveform amplitude gain is determined by characterizing the dependence of amplitude versus mass-to-charge at a reference q value.

5 . The mass spectrometer of claim 1 , wherein the isolation waveform includes a plurality of notches at a plurality of target mass-to-charge ratios.

6 . The mass spectrometer of claim 5 , wherein each of the plurality of notches have a width determined to exceed a threshold isolation efficiency for the corresponding target mass-to-charge ratio.

7 . The mass spectrometer of claim 1 , wherein a frequency error correction is applied to the location of the at least one notch within the isolation waveform.

8 . The mass spectrometer of claim 1 , wherein the isolation waveform applies an excitation force to ions at a plurality of frequencies to eject unwanted ions in substantially the same amount of time.

9 . The mass spectrometer of claim 1 , wherein the frequency profile is empirically determined to eject unwanted ions at a plurality of frequencies in the substantially the same amount of time.

10 . A method for determining a frequency profile for an isolation waveform used in a radio frequency ion trap in a mass spectrometer, the method comprising:
1) supplying an ion population from a calibrant to be injected into the radio frequency ion trap, the ion population having a plurality of ion species covering a range of mass-to-charge ratios; 2) applying a waveform having a flat frequency profile to the radio frequency ion trap; 3) identifying ions of the ion population remaining in in the radio frequency ion trap; 4) repeating steps 1-3 at increasing amplitudes of the waveform to identify an amplitude at which all the ions of a given ion species are ejected from the radio frequency ion trap for each ion species of the ion population; and 5) characterizing the frequency profile for the radio frequency ion trap based on the amplitudes at which all the ions of a given ion species are ejected from the radio frequency ion trap.

11 . The method of claim 10 , further comprising repeating steps 1-4 at multiple trapping radio frequency amplitude levels to cover a range of possible frequencies.

12 . The method of claim 10 , wherein the isolation waveform applies an excitation force to ions at a plurality of frequencies to eject unwanted ions in substantially the same amount of time.

13 . The method of claim 10 , wherein the frequency profile is a best fit to the amplitudes at which all the ions of a given ion species are ejected from the radio frequency ion trap.

14 . The method of claim 13 , wherein the frequency response profile is determined by a segmented regression to a plurality of regions.

15 . The method of claim 13 , wherein the frequency response profile is determined by a polynomial regression to one or more regions.

16 . The method of claim 10 , further comprising characterizing the dependence of amplitude versus mass-to-charge at a reference q value.

17 . The mass spectrometer of claim 16 , wherein characterizing the dependence of amplitude versus mass-to-charge at the reference q value includes:
a) supplying an ion population from the calibrant to the radio frequency ion trap; b) applying a waveform having the amplitude frequency profile to the radio frequency ion trap, the waveform having a notch at a target mass-to-charge ratio; c) obtaining a spectra of the ions remaining within the radio frequency ion trap; d) repeating steps a-c at increasing amplitudes of the waveform to identify an amplitude at which all unwanted ions are ejected from the radio frequency ion trap; and e) repeating steps a-d at multiple trapping radio frequency levels to characterize the dependence of amplitude versus mass-to-charge at the reference q value.

18 . A mass spectrometer comprising:
a radio frequency ion trap; a storage device having data describing a frequency profile stored therein, the frequency response profile determined to eject unwanted ions substantially simultaneously; and a controller configured to:
cause an ion population to be injected into the radio frequency ion trap; and
supply an isolation waveform to the radio frequency ion trap, the isolation waveform having at least one notch at a target mass-to-charge ratio, the isolation waveform having a frequency profile based on the data.

19 . The mass spectrometer of claim 18 , wherein the frequency profile is determined by applying a waveform with flat frequency profile to calibrant ions in the radio frequency ion trap and increasing voltage to identify an amplitude required to eject ions at a plurality of mass-to-charge ratios.

20 . The mass spectrometer of claim 18 , wherein the controller is further configured to apply a time domain waveform amplitude gain to the isolation waveform.

21 . The mass spectrometer of claim 20 , wherein the time domain waveform amplitude gain is determined by characterizing the dependence of amplitude versus mass-to-charge at a reference q value.

22 . The mass spectrometer of claim 21 , wherein the dependence of amplitude versus mass-to-charge at a reference q value is recorded by the storage device.

23 . The mass spectrometer of claim 18 , wherein the isolation waveform includes a plurality of notches at a plurality of target mass-to-charge ratios.

24 . The mass spectrometer of claim 23 , wherein each of the plurality of notches have a width determined to exceed a threshold isolation efficiency for the corresponding target mass-to-charge ratio.

25 . The mass spectrometer of claim 18 , wherein a frequency error correction is applied to the location of the at least one notch within the isolation waveform.

26 . The mass spectrometer of claim 18 , wherein the isolation waveform applies an excitation force to ions at a plurality of frequencies to eject unwanted ions in substantially the same amount of time.

27 . The mass spectrometer of claim 18 , wherein the frequency profile is empirically determined to eject unwanted ions at a plurality of frequencies in substantially the same amount of time.

Assignees

• Thermo Finnigan Llc

Inventors

• Remes Philip M
• Schwartz Jae C

Classifications

• H01J49/0031 Primary

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

• H01J49/427 Primary

  Ejection and selection methods · CPC title

• H01J49/423

  with radial ejection · CPC title

• H01J49/0027

  Methods for using particle spectrometers · CPC title

• H01J49/4205

  Device types · CPC title