Method for performing MS / MS with high-intensity ion beams using a band-pass filtration collision cell to improve the robustness of mass spectrometry.

Abstract

In one aspect, a method of performing mass spectrometry is disclosed, the method including introducing a plurality of precursor ions into a mass spectrometer, selecting a portion of the precursor ions having m / z ratios within a first desired range to provide a plurality of precursor ions, causing fragmentation of at least a portion of the precursor ions to generate a plurality of product ions, selecting a portion of the product ions having m / z ratios within a second desired range, and performing mass spectrometry of the selected product ions.

Description

Technical Field

[0001] (Related Application) This application claims priority to U.S. Provisional Application No. 63 / 148,099, filed Feb. 10, 2021, titled "Method of Performing MS / MS of High Intensity Ion Beams Using a Bandpass Filtering Collision Cell to Enhance Mass Spectrometry Robustness", which is hereby incorporated by reference in its entirety.

[0002] The present disclosure generally relates to mass spectrometers and methods for performing mass spectrometry, e.g., mass spectrometers in which SRM (selective reaction monitoring) is employed to elucidate the structure of a specimen.

Background Art

[0003] Mass spectrometry (MS) is an analytical technique for determining the structure of chemical substances being examined, involving both qualitative and quantitative applications. MS can be useful for identifying unknown compounds, determining the atomic composition in a molecule, determining the structure of a compound by observing its fragmentation, and quantifying the amount of a specific chemical compound in a mixed sample. A mass spectrometer detects chemical substances as ions, and thus the conversion of the specimen into charged ions must occur during sample processing.

[0004] One of the main causes of signal and resolution degradation in mass spectrometers is due to the transmission of ions other than the target specimen into the mass analyzer and the accumulation of such ions on the inner surface of the mass analyzer, which can lead to the charging of those surfaces and the attendant degradation in performance. To mitigate this problem, in some mass spectrometers, ions are filtered prior to their introduction into the first mass analyzer.

[0005] Selective reaction monitoring (SRM) is a method used in tandem mass spectrometry, in which a specific mass of precursor ions is selected in the first stage of the tandem mass spectrometer, and the ionic products of the precursor ion fragmentation reaction are selected in the second stage of the mass spectrometer for detection. While the use of ion filtration in the first stage can help reduce the problem of contamination of various components of the mass spectrometer located upstream in the second stage, the generated ions resulting from the fragmentation of precursor ions can accumulate on the mass spectrometer used to detect the generated ions, thus potentially causing performance degradation.

[0006] Therefore, there is a need for improved mass spectrometers and methods for performing mass spectrometry, in particular for mass spectrometers that can be employed to perform SRM of specimens. [Overview of the project] [Means for solving the problem]

[0007] In one aspect, a method for performing mass spectrometry is disclosed, which includes introducing a plurality of precursor ions into a mass spectrometer, selecting a portion of the precursor ions having an m / z ratio within a first desired range to provide a plurality of precursor ions, causing fragmentation of at least a portion of the precursor ions to generate a plurality of product ions, selecting a portion of the product ions having an m / z ratio within a second desired range, and performing mass spectrometry of the selected product ions.

[0008] In some embodiments, the selection of some of the ions received by the ion source can be performed by introducing precursor ions into a first mass filter, and the selection of some of the generated ions for mass spectrometry can be performed by introducing the generated ions into a second mass filter. The mass filter can be implemented in a variety of different ways. For example, in some embodiments, the mass filter may include a plurality of rods arranged in a multipole configuration to which an RF voltage and / or DC voltage can be applied to ensure that ions having a desired m / z ratio pass through the mass filter, while ions having other m / z ratios are prevented from passing through the mass filter, for example, by undergoing unstable orbits.

[0009] In some embodiments, the multipole configuration can be a quadrupole configuration. Furthermore, in some embodiments, the application of an RF voltage and / or DC voltage to one or more of the rods results in the generation of an electromagnetic field within the mass filter to facilitate the selection of some of the ions received from the ion source or generated ions.

[0010] In a related aspect, a mass spectrometer is disclosed that includes an orifice for receiving multiple ions from an ion source and a first band-pass mass filter for receiving at least a portion of the ions, wherein the first band-pass mass filter is configured to select a portion of ions having an m / z ratio within a first desired range or at a desired value for providing multiple precursor ions. The mass spectrometer may further include a collision cell located downstream of the first band-pass filter for receiving at least a portion of the precursor ions, causing fragmentation of at least a portion of them, and generating multiple product ions. The mass spectrometer may further include a second band-pass mass filter for receiving at least a portion of the product ions, wherein the second band-pass mass filter is configured to select a portion of the product ions having an m / z ratio within a selected range or at a selected value. The selected product ions can then be mass-analyzed, for example, via a downstream mass spectrometer to generate their mass spectra.

[0011] In some embodiments, the impact cell and the second band-pass mass filter are located within the same chamber. Such a chamber can be maintained at a pressure in the range of about 1 to about 10 milliliters to promote the fragmentation of at least some of the precursor ions. Alternatively, the impact cell and the second band-pass mass filter can be located within separate chambers, with the second band-pass mass filter positioned downstream of the impact cell and configured to select a portion of the generated ions that exhibit an m / z ratio within a desired range or value.

[0012] A mass spectrometer can be positioned downstream of a second band-pass mass filter to receive at least some of the generated ions selected by the second band-pass mass filter and to provide mass analysis of them. Various mass spectrometers can be employed. For example, in some embodiments, the mass spectrometer can be a quadrupole mass spectrometer.

[0013] In some embodiments, one of the first and second band-pass mass filters includes a plurality of rods arranged according to a multipole configuration, for example, a quadrupole configuration, wherein the plurality of rods are configured for the application of RF voltages and / or DC voltages to generate an electromagnetic field within the band-pass mass filter to facilitate the selection of ions received from an ion source and / or generated ions.

[0014] In some embodiments, the first band-pass mass filter has an m / z bandwidth in the range of about 0.7 to about 25, and the second band-pass mass filter has an m / z bandwidth in the range of about 10 to about 200. In some embodiments, the second band-pass mass filter has an m / z bandwidth in the range of about 200 to about 400.

[0015] In some embodiments, an ion guide is positioned upstream of a first band-pass mass filter to receive ions passing through an orifice and provide ion focusing. The ion guide may include a plurality of rods arranged in a multi-rod configuration, the plurality of rods being configured for the application of RF voltages and / or DC voltages to the plurality of rods to generate an electromagnetic field for focusing ions. This specification also provides, for example, the following: (Item 1) A method for performing mass spectrometry, wherein the method is Introducing multiple precursor ions into the mass spectrometer, Selecting a portion of the precursor ions having an m / z ratio within a first desired range, This causes fragmentation of at least some of the selected precursor ions, generating multiple product ions. Selecting a portion of the generated ions having an m / z ratio within a second desired range, The mass spectrometry of the selected generated ions is performed. Methods that include... (Item 2) The method according to item 1, wherein the step of selecting a portion of the precursor ions includes introducing the precursor ions into a first mass filter. (Item 3) The method according to item 2, wherein the step of selecting a portion of the generated ions includes introducing the generated ions into a second mass filter. (Item 4) The method according to item 3, wherein either of the first and second mass filters comprises a plurality of rods arranged in a multipole configuration. (Item 5) The method according to item 4, wherein the rod is configured for the application of any DC voltage and / or RF voltage to the rod to generate an electromagnetic field within the mass filter in order to facilitate the selection of any portion of the precursor ions and generated ions. (Item 6) The multipole configuration is the method according to any one of items 4 and 5, wherein the multipole configuration comprises a quadrupole configuration. (Item 7) A mass spectrometer, wherein the mass spectrometer is An orifice for receiving multiple precursor ions from an ion source, A first band-pass mass filter for receiving at least a portion of the ions, wherein the first band-pass mass filter is configured to select a portion of the precursor ions having an m / z ratio within a first desired range, A collision cell located downstream of the first band-pass mass filter, the collision cell receiving at least a portion of the selected precursor ions, causing fragmentation of at least a portion of them, and generating a plurality of product ions, A second band-pass mass filter for receiving at least a portion of the generated ions, wherein the second band-pass mass filter is configured to select a portion of the generated ions having an m / z ratio within a second desired range. A mass spectrometer equipped with this feature. (Item 8) The mass spectrometer described in item 7, wherein the impact cell and the second band-pass mass filter are located in the same chamber. (Item 9) The mass spectrometer described in item 7, wherein the impact cell and the second band-pass mass filter are located in separate chambers. (Item 10) The mass spectrometer according to any one of items 7-9, further comprising a mass spectrometer positioned downstream of the second band-pass mass filter, which receives at least a portion of the selected generated ions and provides mass analysis of them. (Item 11) The mass spectrometer is the mass spectrometer described in item 10, which is equipped with a quadrupole mass spectrometer. (Item 12) The mass spectrometer according to any one of items 7-11, wherein either of the first and second band-pass mass filters comprises a plurality of rods arranged in a multipole configuration, the plurality of rods being configured for the application of either an RF voltage and / or a DC voltage to the plurality of rods to generate an electromagnetic field within the band-pass mass filter in order to facilitate the selection of any portion of the precursor ions and generated ions. (Item 13) The multi-pole configuration is a mass spectrometer according to item 12, comprising a quadrupole configuration. (Item 14) The first band-pass mass filter has a bandwidth in the range of about 0.7 to about 25 m / z, as described in any one of items 7-13 of the mass spectrometer. (Item 15) The second band-pass mass filter has a bandwidth in the range of about 10 to about 200 m / z, as described in any one of items 7-14 of the mass spectrometer. (Item 16) The second band-pass mass filter has a bandwidth in the range of approximately 200 to approximately 400 m / z, as described in any one of items 7-14 of the mass spectrometer. (Item 17) The mass spectrometer according to any one of items 7-16, further comprising an ion guide positioned upstream of the first band-pass mass filter, the ion guide receiving ions passing through the orifice and providing focus of the ions. (Item 18) The mass spectrometer according to item 17, wherein the ion guide comprises a plurality of rods arranged in a multi-rod configuration, and the plurality of rods are configured for the application of an RF voltage and / or DC voltage to the plurality of rods to generate an electromagnetic field for focusing the ions.

[0016] A further understanding of various aspects of the present disclosure can be obtained by referring to the following detailed description and the associated drawings, which are briefly described below.

Brief Description of the Drawings

[0017] [Figure 1] Figure 1 is a flowchart according to one embodiment of this instruction, illustrating the various steps in a method for performing mass spectrometry. [Figure 2] Figure 2 shows a mass spectrometer according to one embodiment of this teaching. [Figure 3] Figure 3 shows an example of applying DC and RF voltages to the rods of the mass filter employed in the mass spectrometer of Figure 2 for selecting a portion of the generated ions based on their m / z ratio. [Figure 4] Figure 4 is a schematic diagram of a mass spectrometer according to another embodiment. [Modes for carrying out the invention]

[0018] This instruction generally relates to methods for performing mass spectrometry and to mass spectrometers on which such methods can be implemented. In some embodiments, a plurality of precursor ions are fragmented, for example, through collisions with a background gas (e.g., N2), and a portion of the resulting ions having an m / z ratio within a desired range are selected for mass spectrometry.

[0019] Referring to the flowchart in Figure 1, a method according to one embodiment of this teaching for performing mass spectrometry includes introducing a plurality of ions into a mass spectrometer (step 1), selecting a portion of those ions at a desired value (or having an m / z ratio within a desired range) via, for example, a mass filter to provide a plurality of precursor ions (step 2), and causing fragmentation of at least a portion of the selected precursor ions (e.g., via collisional dissociation) to provide a plurality of product ions (step 3). The method further includes selecting a portion of the product ions having an m / z ratio within a desired range (step 4), and performing mass spectrometry of the selected product ions (step 5).

[0020] The method described in this instruction can be implemented in various mass spectrometers, and various techniques for ion fragmentation can be used.

[0021] As an example, Figure 2 schematically depicts a mass spectrometer 100 including an ion source 102 for generating multiple ions. Various ion sources can be employed in the practice of this teaching. Some examples of suitable ion sources, but not limited to, include, among others, electrospray ionization devices, sprayer-assisted electrospray devices, chemical ionization devices, sprayer-assisted atomization devices, chemical ionization devices, matrix-assisted laser desorption / ionization (MALDI) ion sources, photoionization devices, laser ionization devices, thermospray ionization devices, inductively coupled plasma (ICP) ion sources, sonic spray ionization devices, glow discharge ion sources, and electron impulse ion sources.

[0022] The generated ions pass through the orifice 104a of the kir template 104 and the orifice 106a of the orifice plate 106, which is located downstream of the kir template and separated from it, thereby forming a gas curtain chamber between the orifice and the kir template. A curtain gas supply unit (not shown) can provide curtain gas flow (e.g., N2) between the kir template 104 and the orifice plate 106, helping to keep the downstream section of the mass spectrometer clean by declumping and discharging large neutral particles. The curtain chamber can be maintained at a high pressure (e.g., above atmospheric pressure), while the downstream section of the mass spectrometer can be maintained at one or more selected pressures via discharging through one or more vacuum pumps (not shown).

[0023] In this embodiment, ions passing through the orifices of the car template and orifice plate are received by a QJet ion guide, which comprises four rods 108 (two of which are visible in this figure) arranged in a quadrupole configuration to form an ion beam for transmission to downstream components of the mass spectrometer. When in use, the QJet ion guide can be employed to capture and focus ions received through the openings of the orifice plate 106 using a combination of gas dynamics and radio frequency fields.

[0024] The ion beam exits the QJet ion guide and is focused through lens IQ0 into a subsequent ion guide Q0, which includes four rods 110 (two of which are visible in this figure), arranged in a quadrupole configuration, and an RF voltage and / or DC voltage may be applied to the four rods 110 to focus ions as they pass through the Q0 ion guide. In other embodiments, other multipole configurations, such as a sextupole or octupole configuration, may also be utilized. In some embodiments, the pressure in the Q0 ion guide can be maintained, for example, in the range of about 3 milliliters to about 10 milliliters. In this embodiment, the Q0 ion guide includes four rods 109 arranged in a quadrupole configuration, and an RF voltage and / or DC voltage may be applied to the four rods 109 to generate an electromagnetic field for focusing ions as they pass through the ion guide.

[0025] The Q0 ion guide delivers ions to a downstream ion guide Q1 configured to function as a mass filter, via an ion lens IQ1 and a short, thick lens ST1 that functions as a Brubaker lens. In this embodiment, the ion guide Q1 is arranged in a quadrupole configuration (however, in other embodiments, other multipole configurations may also be employed) and includes four rods 112 (two of which are visible in this figure) to which an RF voltage and / or DC voltage may be applied. In some embodiments, the Q1 ion guide has a range, for example, about 0.6 to about 4 × 10⁻⁶ -5 It can be installed in a vacuum chamber that can be maintained at a pressure within the Torr range.

[0026] More specifically, in this embodiment, the quadrupole rod assembly Q1 can be operated as a conventional transmission RF / DC quadrupole mass filter for selecting ions having an m / z value of interest or an m / z value within a range of interest. For example, the quadrupole rod assembly Q1 can be provided with an RF / DC voltage suitable for operation in mass resolution mode. For example, the parameters of the applied RF and DC voltages can be selected such that Q1 establishes a transmission window for the selected m / z ratio, thereby allowing these ions to traverse Q1 with minimal perturbation. However, ions with m / z ratios outside the window can be prevented from traversing the quadrupole rod assembly Q1, as they do not achieve stable orbits within the quadrupole. It should be understood that this mode of operation is only one possible mode of operation for Q1.

[0027] In this embodiment, ions selected by the Q1 mass filter are focused into the impact cell Q2 via a short, wide lens and an ion lens IQ2. In this embodiment, the impact cell Q2 includes a pressurized compartment which can be maintained at a pressure in the range of, for example, about 1 milliliter to about 10 milliliters, although other pressures may be used for this or other purposes. A suitable impact gas (e.g., nitrogen, argon, helium, etc.) can be provided via a gas inlet (not shown) to fragment at least some of the ions received by the impact cell.

[0028] In this embodiment, the collision cell Q2 includes three sets of rods Q2a, Q2b, and Q2c arranged in series with respect to each other. In this embodiment, the Q2a rod set includes four rods (two of which are visible in the figure) arranged in a quadrupole configuration, providing a passage for ions to pass through. Ions can undergo collisions as they pass through the passages between the Q2a rod sets, and these collisions cause fragmentation of at least some of the ions received by the collision cell (also referred to herein as precursor ions), generating a plurality of generated ions. Applying an RF voltage to the Q2a rod set can provide an electromagnetic field to radially restrict the precursor ions and / or generated ions. Applying a DC voltage to Q2a can provide a potential drop relative to the Q1 rod offset, and the potential drop is required to accelerate the precursor ions into the collision cell and induce fragmentation. In some embodiments, the Q2a DC offset voltage relative to the Q1 rod offset voltage can be in the range of about 5 to about 150 V.

[0029] In this embodiment, each of the Q2B rod set and the Q2C rod set includes four rods arranged in a quadrupole configuration. The Q2B rod set functions as a mass filter for selecting generated ions having an m / z ratio within a desired range (or a desired value). More specifically, the quadrupole rod set Q2B can be provided with an RF / DC voltage suitable for operating in mass resolution mode. For example, the parameters of the applied RF and DC voltages can be selected such that Q2B will establish a transmission window for generated ions having an m / z value within a desired range. The application of an RF voltage and / or DC voltage to the Q2c rod set can similarly provide an electromagnetic field for radially restricting precursor ions and / or generated ions. The DC voltage applied to Q2c will be 0.5 to 1 V more inductive than the DC rod offset applied to the Q2b rod set.

[0030] Figure 3 schematically illustrates an example of RF voltages that may be applied to Q2B rods numbered 12a, 12b, 12c, and 12d. More specifically, the voltage applied across rods 12b and 12c can be defined according to equation (1), and the voltage applied across rods 12a and 12d can be defined according to equation (2). R0 2b -[U-Vcos(Ωt)] Equation (1) R0 2b +[U-Vcos(Ωt)] Equation (2) During the ceremony, R0 2b This generally represents the DC rod offset voltage set to be inductive within a range of approximately 0.5 to 1V compared to the DC rod offset applied to the Q2a rod set. U represents the amplitude of the decomposed DC voltage. V represents the amplitude of the RF voltage. Ω represents the angular frequency of the RF voltage, and Ω = 2πf, where f represents the frequency of the RF voltage.

[0031] In some embodiments, the resolved DC (i.e., U) voltage can be in the range of about 1 to about 500 V, the amplitude of the RF voltage (i.e., V) can be in the range of about 10 Vp-p to about 3,000 Vp-p, and the frequency of the RF voltage (i.e., f) can be in the range of about 300 kHz to about 5 MHz. With respect to a given U, V, and Ω, the overall ionic motion can result in a stable orbit for some ions having a m / z at a particular value (or within a particular range). Such ions can pass through the quadrupole mass spectrometer, while other ions experience an unstable orbit and are therefore prevented from passing through the quadrupole mass spectrometer.

[0032] The generated ions selected by the Q2b rod are further cooled by collision within the Q2c section, then exit the collision cell Q2, and are focused through its inlet 115 into the downstream quadrupole mass spectrometer Q3 by the ion lens IQ3 and the short, wide lens ST3.

[0033] The quadrupole mass spectrometer Q3 includes four rods 116 arranged relative to each other in a quadrupole configuration, and an RF voltage and / or DC voltage can be applied to the four rods 116 in a manner known in the art to provide mass spectrometry of the generated ions.

[0034] In the embodiments described above, the mass filter is located within the impact cell chamber, but in other embodiments, one or more mass filters may be located downstream of the impact cell in one or more separate chambers. As an example, Figure 4 schematically depicts an example of a mass spectrometer 500 according to such an embodiment, which is similar to the embodiments described above except that it includes a band-pass mass filter Qx located downstream of the impact cell in a separate chamber from the chamber in which the rods of the impact cell are positioned.

[0035] The generated ions produced by the collision cell 402 are received by the downstream quadrupole mass spectrometer Q3 via a short, wide lens that functions to focus the generated ions into the quadrupole mass spectrometer. The quadrupole mass spectrometer Q3 includes four rods arranged relative to each other in a quadrupole configuration, to which RF voltages and / or DC voltages are applied in a manner known in the art, and which can provide mass spectrometry of the generated ions. The ions transmitted through the Q3 mass spectrometer pass through exit lenses 118 and 120 and are then detected by an ion detector 120, which is part of the analyzer module 124.

[0036] This instruction offers several advantages over conventional mass spectrometers. For example, the mass spectrometer according to this instruction can exhibit less contamination in components such as the mass spectrometer and / or ion optics, which are located downstream of the collision cell.

[0037] Those skilled in the art will understand that various modifications to the above embodiments can be made without departing from the scope of the present invention.

Claims

1. A method for performing mass spectrometry, wherein the method is Introducing multiple precursor ions into the mass spectrometer, The method involves introducing the precursor ions into a first band-pass mass filter to select a portion of the precursor ions having a first desired m / z ratio, wherein the first band-pass mass filter comprises a plurality of rods arranged in a multipole configuration, the plurality of rods being configured for applying RF and resolved DC voltages to generate an electromagnetic field within the first band-pass mass filter to facilitate the selection of the precursor ions, and In the collision cell, fragmentation is induced in at least some of the selected precursor ions, generating multiple product ions. The method involves introducing the generated ions into a second band-pass mass filter to select a portion of the generated ions having a second desired m / z ratio, wherein the second band-pass mass filter comprises a plurality of rods arranged in a multipole configuration, the plurality of rods being configured for applying RF and resolved DC voltages to generate an electromagnetic field within the second band-pass mass filter to facilitate the selection of the portion of the generated ions, and The mass spectrometry of the selected generated ions is performed using a mass spectrometer that is separate from and located downstream of the second band-pass mass filter. Methods that include...

2. The method according to claim 1, wherein the multipole configuration comprises a quadrupole configuration.

3. A mass spectrometer, wherein the mass spectrometer is An orifice for receiving multiple precursor ions from an ion source, A first band-pass mass filter for receiving at least a portion of the precursor ions, wherein the first band-pass mass filter is configured to select a portion of the precursor ions having an m / z ratio within a first desired range, A collision cell located downstream of the first band-pass mass filter, the collision cell receiving at least a portion of the selected precursor ions, causing fragmentation of at least a portion of them, and generating a plurality of product ions, A second band-pass mass filter for receiving at least a portion of the generated ions, wherein the second band-pass mass filter is configured to select a portion of the generated ions having a second desired m / z ratio, A mass spectrometer positioned downstream of the second band-pass mass filter, which receives at least a portion of the selected generated ions and provides mass analysis of them. It is equipped with, A mass spectrometer comprising a plurality of rods arranged in a multipole configuration, wherein the first and second band-pass mass filters are configured for the application of RF and resolved DC voltages to generate an electromagnetic field within the first and second band-pass mass filters to facilitate the selection of the precursor and generated ions.

4. The mass spectrometer according to claim 3, wherein the collision cell and the second band-pass mass filter are located within the same chamber.

5. The mass spectrometer according to claim 3, wherein the collision cell and the second band-pass mass filter are located in separate chambers.

6. The mass spectrometer according to claim 3, wherein the mass spectrometer comprises a quadrupole mass spectrometer.

7. The mass spectrometer according to claim 3, wherein the multi-pole configuration comprises a quadrupole configuration.

8. The mass spectrometer according to any one of claims 3-7, wherein the first band-pass mass filter has a bandwidth in the range of about 0.7 to about 25 m / z.

9. The mass spectrometer according to any one of claims 3-8, wherein the second band-pass mass filter has a bandwidth in the range of about 10 to about 200 m / z.

10. The mass spectrometer according to any one of claims 3-8, wherein the second band-pass mass filter has a bandwidth in the range of about 200 to about 400 m / z.

11. The mass spectrometer according to any one of claims 3-10, further comprising an ion guide positioned upstream of the first band-pass mass filter, wherein the ion guide receives ions passing through the orifice and provides focus of the ions.

12. The mass spectrometer according to claim 11, wherein the ion guide comprises a plurality of rods arranged in a multi-rod configuration, the plurality of rods being configured for the application of an RF voltage and / or DC voltage to generate an electromagnetic field for focusing the ions.

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