Method for IDA using CID-ECD

Abstract

Apparatus and a modified IDA method are provided for detecting and separately dissociating alkali metal adducts of compounds. An ion source assembly ionizes one or more compounds of a sample to produce an ion beam. A mass filter selects a mass range of precursor ions from the ion beam, and a mass analyzer measures the intensity and m / z value of the precursor ions and selects one or more of the precursor ions for a peak list. For each pair of precursor ions in the peak list, if the m / z difference within the pair corresponds to the m / z difference between one alkali metal ion and another alkali metal ion or a proton, a processor is used to dissociate one or both precursor ions of the pair using an ExD assembly. A CID assembly is used to dissociate all other precursor ions in the peak list.

Description

[0001] Related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 877,173, filed on July 22, 2019, the contents of which are incorporated herein by reference in their entirety.

[0003] Introduction

[0004] The teachings herein relate to mass spectrometry apparatus for detecting and separately dissociating alkali metal adducts of compounds in information dependent acquisition (IDA) mass spectrometry experiments. More particularly, alkali metal adducts are identified from an IDA survey peak list as follows: each pair of precursor ions of the peak list is analyzed and a determination is made as to whether the mass-to-charge ratio (m / z) difference within the pair corresponds to an m / z difference between one alkali metal ion and another alkali metal ion or proton. If a pair is found to include one or two alkali metal adducts, one or both precursor ions of the pair are dissociated using an electron-based dissociation (ExD) device. All other ions of the IDA peak list are dissociated using a collision-induced dissociation (CID) device.

[0005] The devices and methods disclosed herein are also compatible with processors, controllers, microcontrollers or computer systems such as Figure 1 It is carried out in combination with computer systems.

[0006] Mass spectrometry background

[0007] Mass spectrometry (MS) is an analytical technique for detecting and quantifying compounds based on analyzing the m / z values ​​of ions formed from those compounds. MS involves ionizing one or more compounds of interest from a sample, generating precursor ions, and mass analysis of the precursor ions.

[0008] Tandem mass spectrometry or mass spectrometry / mass spectrometry (MS / MS) involves ionizing one or more compounds of interest from a sample, selecting one or more precursor ions of the one or more compounds, fragmenting the one or more precursor ions into product ions, and mass analysis of the product ions.

[0009] Mass spectrometers are often coupled to chromatograms or other separation systems to identify and characterize relevant eluting compounds from a sample. In such coupled systems, the compounds in the elution solvent are ionized and a series of mass spectra are obtained at specified time intervals. These time intervals range from, for example, 1 second to 100 minutes or longer. The intensity values ​​derived from the series of mass spectra constitute a chromatogram. For example, the sum of all intensities produces a total ion chromatogram (TIC) and the intensity of a mass value produces an extracted ion chromatogram (XIC).

[0010] The peaks present in the chromatogram are used to identify or characterize known peptides or compounds in the sample because they elute at known times, called retention times. More particularly, the retention times and / or areas of the peaks are used to identify or characterize (quantitate) known peptides or compounds in the sample.

[0011] In a conventional separation-coupled mass spectrometry system, a precursor ion of a known compound is selected for analysis. An MS / MS scan is then performed at each separation interval over a mass range encompassing the precursor ion. The intensities of the product ions found in each MS / MS scan are collected over time and analyzed as a batch of spectra or, for example, XIC.

[0012] Both MS and MS / MS can provide both qualitative and quantitative information. The measured precursor or product ion spectra can be used to identify the molecules of interest. The intensities of the precursor and product ions can also be used to quantify the amount of a compound present in a sample.

[0013] There are many different types of experimental acquisition methods or workflows that can be performed with a tandem mass spectrometer. Three broad categories of these workflows are targeted acquisition, information-dependent acquisition (IDA) or data-dependent acquisition (DDA), and data-independent acquisition (DIA).

[0014] In targeted acquisition methods, one or more conversions of precursor ions to product ions are predetermined or known for the compound of interest. A tandem mass spectrometer is introduced with the sample and the one or more conversions are monitored over multiple time periods or cycles. In other words, the mass spectrometer selects and fragments the precursor ions for each conversion and performs targeted mass analysis on the product ions of the conversion. As a result, an intensity (product ion intensity) is generated for each conversion. Targeted acquisition methods include, but are not limited to, multiple reaction monitoring (MRM) and selected reaction monitoring (SRM).

[0015] In the IDA method, the user can specify criteria for performing non-targeted mass analysis of product ions when the sample is introduced into a tandem mass spectrometer. For example, in the IDA method, a precursor ion or mass spectrometry (MS) survey scan is performed to generate a precursor ion peak list. The user can select criteria for filtering the peak list to obtain a subset of precursor ions on the peak list. MS / MS is then performed on each precursor ion of the subset of precursor ions. A product ion spectrum is generated for each precursor ion. As the sample is introduced into the tandem mass spectrometer, MS survey scans and subsequent multiple MS / MS scans can be repeatedly (iteratively) performed on the precursor ions of the subset of precursor ions. IDA can also be referred to as data-dependent analysis (Thermo Fisher) or data-directed analysis (Waters). For example, the term "data-dependent" is trademarked by Thermo Fisher and the term "DDA" is trademarked by Waters.

[0016] Measuring complex (e.g., biological) samples using various omics techniques, such as proteomics and metabolomics, results in a large number of compounds of diverse types and a wide dynamic range. In proteomics and many other sample types, the complexity and dynamic range of compounds are enormous. This presents challenges for traditional targeted and IDA methods, which require very high-speed MS / MS acquisition to deeply interrogate the sample in order to identify and quantify a wide range of analytes.

[0017] As a result, DIA methods, i.e., the third broad category of tandem mass spectrometry, have been developed. These DIA methods have been used to increase the reproducibility and comprehensiveness of data collection from complex samples. DIA methods can also be referred to as non-specific fragmentation methods. In traditional DIA methods, based on the data obtained in the previous precursor or product ion scan, the activity of the tandem mass spectrometer remains unchanged in each MS / MS scan. Instead, a precursor ion mass range is selected. The precursor ion mass selection window is then stepped across the precursor ion mass range. All precursor ions in the precursor ion mass selection window are fragmented, and all product ions of all precursor ions in the precursor ion mass selection window are mass analyzed.

[0018] Cracking technology background

[0019] Electron-based dissociation (ExD), ultraviolet light dissociation (UVPD), infrared light dissociation (IRMPD) and collision-induced dissociation (CID) are often used as fragmentation techniques for tandem mass spectrometry (MS / MS). CID is the most common technique used for dissociation in tandem mass spectrometers.

[0020] ExD can include, but is not limited to, electron induced dissociation (EID), electron impact excitation in organics (EIEIO), electron capture dissociation (ECD), or electron transfer dissociation (ETD).

[0021] Alkali Metal Adduct IDA Problem

[0022] Analysis via IDA acquisition is one of the most widely used methods to generate MS / MS information in an automated manner. Over the years, several filters have been developed to filter peak lists of subsets of precursor ions to be dissociated, with the goal of optimizing the automated selection of relevant ions in specific applications. These filters have included charge state selection for peptides, mass defects for relevant metabolites, isotope ratio standards for pesticides, and kinetic background subtraction for compounds with liquid chromatography (LC) profiles. However, there has been little or no effort to ensure that singly or multiply charged ions selected in real time will systematically generate MS / MS information that can be used for identification.

[0023] Ionization is usually achieved by adding a proton to a molecule [M+H] +ions, but other forms, called adducts, can be formed by the addition of alkali metal ions such as sodium (Na + ) to obtain [M+Na] + , potassium [M+K] + or lithium [M+Li] + In the case of protonated compounds ([M+H] + In the case of MS / MS, CID generally produces fragment ions that can lead to compound identification. However, in the case of equivalent alkali metal adducts of the same compound, such as [M+Na] + or [M+K] + In the case of CID-MS / MS, weak or no fragment ions are typically observed, which reduces the effectiveness of IDA and the amount of information generated in metabolomics applications.

[0024] Mosely et al., Anal. Chem. 2011, 83, 4068-4075 and others have recently reported that EID and EIEIO can be used to dissociate singly charged alkali metal adducts. Similarly, it is well known that ECD and ETD can be used to preferentially dissociate large multiply charged compounds such as peptides and protein backbones. However, it is also known that the EID method is not well suited for the dissociation of singly charged protonated compounds ([M+H] + ).

[0025] As a result, additional equipment and methods are required to enable the dissociation of alkali metal adducts in IDA experiments. Summary of the Invention

[0026] Disclosed herein are apparatus, methods, and computer program products for detecting and separately dissociating alkali metal adducts of compounds in an IDA mass spectrometry experiment. The apparatus includes an ion source assembly and a tandem mass spectrometer. The tandem mass spectrometer includes a mass filter assembly, an Exo-D-ionization (E-D) assembly, a CID assembly, and a mass analyzer. The ion source assembly 210 ionizes one or more compounds in a sample, generating an ion beam.

[0027] During the first phase of an IDA experiment, the tandem mass spectrometer first constructs a precursor ion peak list using an MS survey scan. A mass filter assembly transmits a range of precursor ions from the ion beam. The mass analyzer measures the intensity and m / z values ​​of the precursor ions. The tandem mass spectrometer or processor then selects one or more of the measured precursor ions for the peak list.

[0028] During the second time period of the IDA experiment, the tandem mass spectrometer selects and dissociates each precursor ion of the peak list. The mass filter device selects each precursor ion of the peak list from the ion beam. Before selecting each precursor ion, each possible precursor ion pair is checked by the mass analyzer to determine whether the pair includes at least one alkali metal adduct.

[0029] In this test, the m / z difference within each pair is compared to the m / z value of one or more alkali metal ions minus the proton m / z. The m / z difference within each pair is also compared to each difference in the m / z values ​​of one or more different combinations of two different alkali metal ions.

[0030] Based on the inspection of each pair in the peak list, the dissociation type is determined. In particular,

[0031] For each pair of precursor ions, if the m / z difference within the pair corresponds to the difference between the alkali metal ion and the proton (e.g.

[0032] Na + -H + ) or the difference in m / z values ​​of two different alkali metal ions, the ExD device is used

[0033] Dissociate one or both precursor ions of the pair. Dissociate all other precursor ions of the peak list using a CID device.

[0034] These and other features of the applicants' teachings are as described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The skilled artisan will appreciate that the drawings described below are for illustration purposes only and are not intended to limit the scope of the present teachings in any way.

[0036] Figure 1 is a block diagram illustrating a computer system upon which embodiments of the present teachings may be implemented.

[0037] Figure 2 is a schematic diagram of an apparatus for detecting and separately dissociating alkali metal adducts of compounds in an information dependent acquisition (IDA) mass spectrometry experiment, with reference to various embodiments.

[0038] Figure 3 are exemplary graphs of hypothetical precursor ion spectra showing how a precursor ion pair may be examined to determine whether the pair includes at least one alkali metal adduct, with reference to various embodiments.

[0039] Figure 4 is a schematic diagram of a Chimera ExD device with reference to various embodiments.

[0040] Figure 5 3D perspective views of a cross-section of the Chimera ExD and CID collision cells, with reference to various embodiments.

[0041] Figure 6 is a flow chart showing methods for detecting and separately dissociating alkali metal adducts of compounds in IDA mass spectrometry experiments, with reference to various embodiments.

[0042] Figure 7 is a schematic diagram of a system including one or more different software modules that implements a method for detecting and separately dissociating alkali metal adducts of a compound in an IDA mass spectrometry experiment, with reference to various embodiments.

[0043] Before describing one or more embodiments of the present teachings in detail, those skilled in the art will understand that the present teachings are not limited to the construction details, component arrangements, and step arrangements described in the following detailed description or illustrated in the accompanying drawings. In addition, it should be understood that the phrases and terms used herein are intended to describe and should not be considered as limiting.

[0044] Description of various embodiments

[0045] Computer-implemented systems

[0046] Figure 1 is a block diagram illustrating a computer system 100 in which embodiments of the present teachings may be implemented. Computer system 100 includes a bus 102 or other communication mechanism for communicating information, and a processor 104 coupled to bus 102 for processing information. Computer system 100 also includes a memory 106, which can be a random access memory (RAM) or other dynamic storage device, coupled to bus 102 for storing instructions to be executed by processor 104. Memory 106 may also be used to store temporary variables or other intermediate information during the execution of instructions to be executed by processor 104. Computer system 100 also includes a read-only memory (ROM) 108 or other static storage device coupled to bus 102 for storing static information and instructions for processor 104. Storage device 110, such as a magnetic disk or optical disk, is provided and coupled to bus 102 for storing information and instructions.

[0047] The computer system 100 may be coupled via the bus 102 to a display 112, such as a cathode ray tube (CRT) or a liquid crystal display (LCD), for displaying information to a computer user. An input device 114, including alphanumeric and other keys, is coupled to the bus 102 for communicating information and command selections to the processor 104. Another type of user input device is a cursor controller 116, such as a mouse, trackball, or cursor navigation keys, for communicating guidance information and command selections to the processor 104 and for controlling cursor movement on the display 112. The input device typically has two degrees of freedom, a first axis (i.e., x) and a second axis (i.e., y), which allows the device to specify a position in a plane.

[0048] Computer system 100 is capable of implementing the present teachings. Consistent with certain implementations of the present teachings, computer system 100 provides results in response to processor 104 executing one or more sequences of one or more instructions contained in memory 106. The instructions may be read into memory 106 from another computer-readable medium, such as storage device 110. Execution of the sequences of instructions contained in memory 106 causes processor 104 to perform the processes described herein. Alternatively, hard-wired circuitry may be used in place of or in combination with software instructions to implement the present teachings. Thus, implementation of the present teachings is not limited to any specific combination of hardware circuitry and software.

[0049] In various embodiments, computer system 100 can be connected to one or more other computer systems similar to computer system 100 over a network to form a networked system. The network can include a private network or a public network such as the Internet. In a networked system, one or more computer systems can store and deliver data to other computer systems. In cloud computing, the one or more computer systems that store and deliver data can be referred to as servers or clouds. The one or more computer systems can include, for example, one or more network servers. The other computer systems that send and receive data to and from the servers or cloud can be referred to as clients or cloud devices, for example.

[0050] The term "computer-readable medium," as used herein, refers to any medium that participates in providing instructions to processor 104 for execution. Such media may take many forms, including, but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as storage device 110. Volatile media include dynamic memory, such as memory 106. Transmission media include coaxial cables, copper wire, and fiber optics, including the wires comprising bus 102.

[0051] Common forms of computer-readable media or computer program products include, for example, floppy disks, flexible disks, hard disks, magnetic tape or any other magnetic medium, CD-ROMs, digital versatile disks (DVDs), Blu-ray discs, any other optical medium, thumb drives, memory cards, RAM, PROMs, and EPROMs, FLASH-EPROMs, any other memory chips or tapes, or any other tangible medium from which a computer can read.

[0052] Various forms of computer-readable media may be involved in carrying one or more sequences of one or more instructions to processor 104 for execution. For example, the instructions may initially be carried on a disk on a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to computer system 100 can receive the data on the telephone line and convert the data into an infrared signal using an infrared transmitter. An infrared detector coupled to bus 102 can receive the data carried in the infrared signal and place the data on bus 102. Bus 102 carries the data to memory 106, from which processor 104 retrieves and executes the instructions. The instructions received by memory 106 may optionally be stored on storage device 110 before or after execution by processor 104.

[0053] According to various embodiments, instructions configured to be executed by a processor for performing the method are stored on a computer-readable medium. A computer-readable medium can be a device that stores digital information. For example, a computer-readable medium includes a compact disc read-only memory (CD-ROM), as is known in the art for storing software. The computer-readable medium is accessed by a processor adapted to execute the instructions configured to be executed.

[0054] The various implementations of the present teachings described below are for illustrative and illustrative purposes. They are not exhaustive and do not limit the present teachings to the precise form disclosed. Modifications and variations are possible with reference to the above teachings or can be derived from implementations of the present teachings. Additionally, the implementations described include software, but the present teachings can be implemented as a combination of hardware and software or in hardware alone. The present teachings can be implemented using both object-oriented and non-object-oriented programming systems.

[0055] Detection and dissociation of alkali metal adducts in IDA

[0056] As described above, analysis via IDA acquisition is one of the most widely used methods for generating MS / MS information in an automated manner. However, there is little or no effort to ensure that single-charged species selected in real time will systematically generate MS / MS information that can be used for identification. In particular, when alkali metal adducts of compounds are subjected to CID-MS / MS, no fragment ions or very few fragment ions are generally observed. This reduces the effectiveness and efficiency of IDA (waste of time) and the amount of information generated in metabolomics applications.

[0057] It is known that EID and EIEIO can be used to dissociate singly charged alkali metal adducts. Similarly, it is known that ECD and ETD can be used to preferentially dissociate large multiply charged compounds such as peptides and protein backbones. However, the EID method is not well suited for the dissociation of singly charged protonated compounds. As a result, additional equipment and methods are required to make it possible to dissociate alkali metal adducts in IDA experiments.

[0058] In various embodiments, additional equipment is provided and the IDA method is modified to detect and separately dissociate the alkali metal adducts of the compound in the IDA experiment. As described above, it has been observed that ExD (>8 eV) of the alkali metal adducts of the compound can produce useful fragmentation, wherein the fragment mixture is Frag + and [Frag+alkali metal] + However, in the [M+H] + When ExD is performed in a non-specific manner, the efficiency is generally lower and fewer new / complementary compound cleavage messages are generated compared to CID cleavage.

[0059] In various embodiments, a method for real-time differentiation of protonated ions ([M+H] + ) and those ions derived from alkali metal adducts ([M+Na] + or [M+K] + ) allows IDA to produce MS / MS fragmentation of compounds that will yield the highest yields for CID and ExD, respectively. One means of detecting sodiated or potassiumated compounds is, for example, to look for evidence of mass pairs with precise differences corresponding to the presence of protons and sodium ions (Na + ) or the m / z difference between the potassium ion (K + ) between the m / z difference (δ mass 37.9559). The observed difference is equivalent to Na + -H + (21.981944) and K + -H + (37.955881). For higher mass ions corresponding to alkali metal adducts, MS / MS data were collected using an ExD instrument.

[0060] Additionally, in various embodiments, detecting peaks with a mass difference (e.g., equivalent to the mass difference between sodium and potassium ions (38.963158 - 22.989221 = 15.973937)) can also reveal compounds that are ionized only in their alkali metal adduct form and can also be selected for ExD fragmentation. In other words, detecting peak pairs where the m / z difference within the pair corresponds to the m / z difference of two different alkali metal ions can also be used to detect alkali metal adducts of the compound. All other peaks are assumed to originate from protonated compounds and subjected to CID MS / MS analysis.

[0061] IDA Alkali Metal Adduct Detection and Dissociation Instrument

[0062] Figure 2 is a schematic diagram 200 of an apparatus for detecting and separately dissociating alkali metal adducts of compounds in an IDA mass spectrometry experiment, with reference to various embodiments. Figure 2 The device includes an ion source device 210 and a tandem mass spectrometer 220.

[0063] The ion source device 210 ionizes one or more compounds of the sample to generate an ion beam. The ion source device 210 can be, but is not limited to, an electrospray ionization source (ESI) device, a chemical ionization (CI) source device such as an atmospheric pressure chemical ionization source (APCI) device, an atmospheric pressure photoionization (APPI) source device, or a matrix-assisted laser desorption source (MALDI) device. In an exemplary embodiment, the ion source device 210 is an ESI device.

[0064] Tandem mass spectrometer 220 includes a mass filter device 224, an ExD device 225, a CID device 226, and a mass analyzer 227. In the first time period of the IDA experiment, the tandem mass spectrometer 220 first constructs a precursor ion peak list. The tandem mass spectrometer 220 uses the mass filter device 224 and the mass analyzer 227 to construct the precursor ion peak list. The mass filter device 224 transmits the precursor ions from the ion beam. The mass analyzer 227 measures the intensity and m / z value of the precursor ions. The tandem mass spectrometer 220 then selects one or more of the measured precursor ions for the peak list. In the IDA method, for example, the precursor ion with the highest measured intensity is selected for the peak list.

[0065] In the Figure 2 In the exemplary embodiment of FIG, the mass filter device 224 is a Q1 quadrupole. However, the mass filter device 224 can be any type of mass filter, such as an ion trap.

[0066] In the Figure 2In an exemplary embodiment, mass analyzer 227 is a time-of-flight (TOF) mass analyzer. However, mass analyzer 227 can be any type of mass analyzer, including but not limited to a quadrupole, ion trap, linear ion trap, orbiting ion trap, or Fourier transform ion cyclotron resonance mass analyzer.

[0067] During the second time period of the IDA experiment, the tandem mass spectrometer 220 selects and dissociates each precursor ion of the peak list. The precursor ions of the peak list are selected from the ion beam using a mass filter device 224. Before selecting each precursor ion, each possible precursor ion pair is checked using a mass analyzer 227 to determine whether the pair includes at least one alkali metal adduct. In this check, the m / z difference within the pair is compared to the m / z difference between one alkali metal ion and another alkali metal ion or proton. In various embodiments, the tandem mass spectrometer 220 can filter the peak list before selecting and dissociating each peak. For example, peaks that have been previously analyzed can be removed.

[0068] Figure 3 is an exemplary graph 300 of a hypothetical precursor ion spectrum showing how a precursor ion pair may be examined to determine whether the pair includes at least one alkali metal adduct, with reference to various embodiments. Figure 3 In , for example, nine precursor ion peaks are found to be above a threshold intensity of 310 and are selected for use in the IDA peak list. Each possible unique pairing of the nine precursor ions is examined to determine whether the pair includes at least one alkali metal adduct.

[0069] First, the m / z difference within the pair is compared to the m / z difference between one or more alkali metal ions and the proton, i.e., X + -H + (Equivalent to XH.) For example, compare the m / z difference to the sodium m / z value minus the proton m / z (21.9819) or the potassium m / z value minus the proton m / z (37.9559).

[0070] From this first comparison, it was found that the m / z difference 325 between peak 320 and peak 330 was 37.9559. From the difference 325, it was determined that peak 320 was the protonated form [M1+H] of compound M1. + Peak 330 is the potassium form or adduct of compound M1 [M1+K] + It was also found that the m / z difference 365 between peak 360 and peak 370 was 21.9819. From the difference 365, it was determined that peak 360 was the protonated form [M3+H] of compound M3. + Peak 370 is the sodium form or adduct of compound M3 [M3+Na] + .

[0071] In a second comparison, the m / z differences within each pair are also compared to the m / z differences for one or more different combinations of two different alkali metal ions. For example, the m / z difference is compared to the m / z difference between sodium and potassium ions (38.963158 - 22.989221 = 15.973937). From this second comparison, it is found that the m / z difference 345 between peak 340 and peak 350 is 15.9739. From the difference 345, it is determined that peak 340 is the sodium form of compound M2 [M2 + Na]. + , while peak 350 is the potassium form or adduct of compound M2 [M2+K] + .

[0072] What is implied here is that [M2+H] does not exist in the list + For example, it is absent or below the threshold intensity 310. In various embodiments, for example, if an alkali metal adduct of compound M2 ([M2+Na] + or [M2+K] + ) and the protonated form of the compound ([M2+H] + ) is not in the list, peaks below a threshold intensity 310 can be analyzed for protonated forms. If a peak for a protonated form is found, it can be fragmented using CID.

[0073] As described below, in various embodiments, if the m / z difference within the precursor ion pair corresponds to the difference between an alkali metal ion and a proton (e.g., Na + -H + ), one precursor ion of the pair is dissociated using the ExD device. For example, the precursor ion of the pair with the higher m / z value is dissociated using the ExD device. In this case, all precursor ions with the m / z value of peak 330 are dissociated using the ExD device because peak 330 has a higher m / z value. All precursor ions with the m / z value of peak 320 are dissociated using the CID device.

[0074] In various embodiments, if the difference in m / z within the precursor ion pair corresponds to the difference in m / z of two different alkali metal ions, then one or both precursor ions of the pair are dissociated using the ExD device. If one precursor ion of the pair is dissociated using the ExD device, then the precursor ion of the pair with the higher m / z value or with the higher intensity can be dissociated using the ExD device. In this case, all precursor ions with the m / z value of peak 340 or peak 350 can be dissociated using the ExD device. If only one precursor ion of the pair is dissociated and the selection criterion is higher intensity, then all precursor ions with the m / z value of peak 340 are dissociated using the ExD device. If only one precursor ion of the pair is dissociated and the selection criterion is higher m / z value, then all precursor ions with the m / z value of peak 350 are dissociated using the ExD device.

[0075] Back to Figure 2 , based on an inspection of each pair in the peak list, the dissociation type is determined. Specifically, for each pair of precursor ions in the peak list, if the m / z difference within the pair corresponds to the m / z difference between an alkali metal ion and a proton (e.g., Na + -H + ) or the difference in m / z between two different alkali metal ions, one precursor ion or both precursor ions of the pair are dissociated using the ExD device 225. All other precursor ions of the peak list are dissociated using the CID device 226.

[0076] In the Figure 2 In an exemplary embodiment, the ExD device 225 is a Chimera device. However, the ExD device 225 can be any type of ExD device, including but not limited to an EID, EIEIO, ECD, or ETD device.

[0077] Figure 4 4 is a schematic diagram of a Chimera ExD device, with reference to various embodiments. The Chimera ExD device includes an electron emitter or filament 410 and an electron gate 420. Electrons are emitted perpendicular to the ion flow 430 and parallel to the magnetic field direction 440.

[0078] Figure 5 is a cross-sectional three-dimensional perspective view 500 of a Chimera ExD and CID collision cell, with reference to various embodiments. Figure 5 It is shown that fragmentation of the precursor ion can be selectively performed at position 511 in the Chimera ExD 514 or at position 512 in the CID collision cell 515.

[0079] Back to Figure 2 In various embodiments, during the second time period of the IDA experiment, a mass analyzer 227 is used to further measure the intensity and m / z value of the product ions of each precursor ion dissociated by the ExD device 225 to generate an ExD product ion spectrum for each precursor ion dissociated 225 by the ExD device.

[0080] In various embodiments, the tandem mass spectrometer 220 further identifies the compounds of the sample by comparing the ExD product ion spectrum to a library of product ions generated by ExD. The library of product ions generated by ExD is similar to those generated by electron ionization or electron impact (EI). The National Institute of Standards and Technology (NIST) library provides reference electron impact ionization (EI) spectra of hundreds of thousands of compounds, which are generated by gas chromatography coupled to mass spectrometry (GC-MS). The EI spectrum is generated by the precursor molecule radical cation M ·+and characteristic fragments. The EID of alkali metal adducts of singly charged compounds provides ·+ and EI-characteristic fragment spectra, it is therefore possible to identify compounds from the EID spectrum by comparison with the EI spectrum.

[0081] Similarly, in various embodiments, tandem mass spectrometer 220 further identifies the compounds of the sample by comparing the CID product ion spectrum to a library of spectra of product ions generated by CID.

[0082] In various embodiments, if the m / z difference within a pair corresponds to the difference between an alkali metal ion and a proton (e.g., Na + -H + ), the tandem mass spectrometer 220 dissociates one precursor ion of the pair using an ExD device 225. For example, the precursor ion of the pair with the higher m / z value is dissociated 225 using an ExD device.

[0083] In various embodiments, if the difference in m / z within the pair corresponds to the difference in m / z of two different alkali metal ions, the tandem mass spectrometer 220 dissociates one precursor ion or both precursor ions of the pair using the ExD device 225. If one precursor ion of the pair is dissociated using the ExD device 225, the precursor ion of the pair with the higher m / z value or the higher intensity can be dissociated using the ExD device 225.

[0084] In various embodiments, the alkali metal ions include lithium ions (Li + ), sodium ion (Na + ), potassium ion (K + ), rubidium ions (Rb + ), cesium ions (Cs + ) or francium ions (Fr + ) One of the two different alkali metal ions including Li + 、Na + , K + , Rb + 、Cs + or Fr + Any two of .

[0085] In various embodiments, the ExD device 225 performs one of EID or EIEIO on singly charged precursor ions and one of ECD or ETD on multiply charged precursor ions.

[0086] In various embodiments, the processor 230 is used to control or provide instructions to the ion source device 210, the tandem mass spectrometer 220, the mass filter device 224, the ExD device 225, the CID device 226, and the mass analyzer 227, and to analyze the data collected. The processor 230 controls or provides instructions by, for example, controlling one or more voltage, current, or pressure sources (not shown). The processor 230 can be configured as follows: Figure 2 Shown is a separate device or can be a processor or controller of one or more devices of the tandem mass spectrometer 220. The processor 230 can be, but is not limited to, a controller, a computer, a microprocessor, Figure 1 A computer system or any device capable of sending and receiving control signals and data.

[0087] In various embodiments, the tandem mass spectrometer 220 can further include an opening and skimmer 221 , an ion guide 222 , and a Q0 ion guide 223 .

[0088] IDA Alkali Metal Adduct Detection and Dissociation Method

[0089] Figure 6 is a flow chart illustrating a method 600 for detecting and separately dissociating alkali metal adducts of a compound in an IDA mass spectrometry experiment, with reference to various embodiments.

[0090] In step 610 of method 600 , a processor instructs an ion source assembly to ionize one or more compounds of a sample to generate an ion beam.

[0091] In step 620, a processor is used to instruct a mass filter of a tandem mass spectrometer to transmit a mass range of precursor ions from the ion beam.

[0092] In step 630, the processor instructs the mass analyzer of the tandem mass spectrometer to measure the intensity and m / z value of the precursor ion.

[0093] In step 640, a processor selects one or more of the precursor ions for the IDA experiment for the peak list.

[0094] In step 650, for each pair of precursor ions in the peak list of the IDA experiment, if the m / z difference within the pair corresponds to the m / z difference between one alkali metal ion and another alkali metal ion or a proton, the processor instructs the ExD device of the tandem mass spectrometer to dissociate one or both precursor ions of the pair.

[0095] In step 650, the processor instructs the CID device of the tandem mass spectrometer to dissociate all other precursor ions of the peak list of the IDA experiment.

[0096] IDA Alkali Metal Adduct Detection and Dissociation Computer Program Product

[0097] In various embodiments, a computer program product comprises a tangible computer-readable storage medium having a program as its contents, the instructions of which are executed on a processor to perform a method for detecting and separately dissociating alkali metal adducts of a compound in an IDA mass spectrometry experiment. The method is performed by a system comprising one or more different software modules.

[0098] Figure 7 is a schematic diagram of a system 700 comprising one or more different software modules for performing a method for detecting and separately dissociating alkali metal adducts of a compound in an IDA mass spectrometry experiment, with reference to various embodiments. The system 700 comprises a control module 710 and an analysis module 720.

[0099] The control module 710 instructs the ion source assembly to ionize one or more compounds in the sample to generate an ion beam. The control module 710 instructs the mass filter of the tandem mass spectrometer to transmit precursor ions of a mass range from the ion beam. The control module 710 instructs the mass analyzer of the tandem mass spectrometer to measure the intensity and m / z value of the precursor ions.

[0100] The analysis module 720 selects one or more of the precursor ions for the peak list of the IDA experiment.

[0101] For each pair of precursor ions in the peak list of the IDA experiment, if the m / z difference within the pair corresponds to the m / z difference between one alkali metal ion and another alkali metal ion or a proton, the control module 710 instructs the ExD device of the tandem mass spectrometer to dissociate one or both precursor ions of the pair.

[0102] Control module 710 instructs the CID device of the tandem mass spectrometer to dissociate all other precursor ions of the peak list for the IDA experiment.

[0103] Furthermore, when describing various embodiments, the specification may present a method and / or process as a particular sequence of steps. However, to the extent that a method or process does not rely on the particular order of steps described herein, the method or process should not be limited to the particular sequence of steps described. One of ordinary skill in the art will understand that other sequences of steps may be possible. Therefore, the particular order of steps described in the specification should not be construed as limiting the claims. Furthermore, claims relating to methods and / or processes should not be limited to performing their steps in the order described, and one of ordinary skill in the art will readily understand that the sequence can vary and still fall within the spirit and scope of the various embodiments.

Claims

1. An apparatus for detecting and separately dissociating alkali metal adducts of a compound in an information dependent acquisition (IDA) mass spectrometry experiment, comprising: an ion source device for ionizing one or more compounds of the sample to generate an ion beam; and A tandem mass spectrometer comprising a mass filter device, an electron-based dissociation (ExD) device, a collision-induced dissociation (CID) device and a mass analyzer, and wherein Constructing a precursor ion peak list for an IDA experiment by transmitting a mass range of precursor ions from an ion beam using a mass filter, measuring the intensity and mass-to-charge ratio (m / z) values ​​of the precursor ions using a mass analyzer, and selecting one or more of the precursor ions for the peak list, and The precursor ions of the peak list in the IDA experiment are dissociated as follows: for each pair of precursor ions in the peak list, if the m / z difference within the pair corresponds to the m / z difference between one alkali metal ion and another alkali metal ion or a proton, one or both precursor ions of the pair are dissociated using the ExD device, while all other precursor ions of the peak list are dissociated using the CID device.

2. The apparatus of claim 1 , wherein the tandem mass spectrometer further measures the intensity and m / z value of the product ions of each precursor ion dissociated using the ExD device using a mass analyzer to generate an ExD product ion spectrum for each precursor ion dissociated using the ExD device.

3. The apparatus of claim 2, wherein the tandem mass spectrometer further identifies compounds of the sample by comparing the ExD product ion spectrum to a library of spectra of product ions generated by electron ionization (EI).

4. The apparatus according to claim 1, wherein the tandem mass spectrometer further measures the intensity and m / z value of the product ions of each precursor ion dissociated by the CID device using a mass analyzer to generate a CID product ion spectrum for each precursor ion dissociated by the CID device.

5. The apparatus of claim 4, wherein the tandem mass spectrometer further identifies compounds of the sample by comparing the CID product ion spectrum to a library of product ion spectra generated by CID.

6. The apparatus of claim 1, wherein if the tandem mass spectrometer determines that the intra-pair m / z difference corresponds to the m / z difference between an alkali metal ion and a proton, the tandem mass spectrometer dissociates one precursor ion of the pair using an ExD device.

7. The apparatus of claim 6, wherein the tandem mass spectrometer dissociates one precursor ion of the pair with an ExD device by dissociating the precursor ion of the pair with the higher m / z value.

8. The apparatus of claim 1, wherein the tandem mass spectrometer dissociates one precursor ion of the pair using an ExD device if the tandem mass spectrometer determines that the intra-pair m / z difference corresponds to the m / z difference between one alkali metal ion and another alkali metal ion.

9. The apparatus of claim 8, wherein the tandem mass spectrometer dissociates one precursor ion of the pair with an ExD device by dissociating the precursor ion of the pair with the higher m / z value.

10. The apparatus of claim 8, wherein the tandem mass spectrometer dissociates one precursor ion of the pair with an ExD device by dissociating the precursor ion of the pair with a higher intensity.

11. The apparatus of claim 1 , wherein if the tandem mass spectrometer determines that the intra-pair m / z difference corresponds to the m / z difference between one alkali metal ion and another alkali metal ion, the tandem mass spectrometer dissociates the two precursor ions of the pair using an ExD device.

12. The apparatus of claim 1, wherein the alkali metal ions comprise lithium ions (Li + ), sodium ion (Na + ), potassium ion (K + ), rubidium ions (Rb + ), cesium ions (Cs + ) or francium ions (Fr + ) and the two different alkali metal ions include Li + 、Na + , K + , Rb + 、Cs + or Fr + Any two of .

13. The apparatus of claim 1 , wherein the ExD device performs one of electron induced dissociation (EID) or electron impact excitation in organic matter (EIEIO) on singly charged precursor ions and performs one of electron capture dissociation (ECD) or electron transfer dissociation (ETD) on multiply charged precursor ions.

14. A method for detecting and separately dissociating an alkali metal adduct of a compound in an information dependent acquisition (IDA) mass spectrometry experiment, comprising: Instructing the ion source device with a processor to ionize one or more compounds of the sample to generate an ion beam; instructing, with the processor, a mass filter of a tandem mass spectrometer to transmit a mass range of precursor ions from the ion beam; instructing a mass analyzer of a tandem mass spectrometer to measure the intensity and mass-to-charge ratio (m / z) value of the precursor ion using the processor; selecting, with the processor, one or more of the precursor ions for a peak list for an IDA experiment; for each pair of precursor ions in the peak list of the IDA experiment, if the m / z difference within the pair corresponds to the m / z difference between one alkali metal ion and another alkali metal ion or a proton, instructing an electron-based dissociation (ExD) device of the tandem mass spectrometer to dissociate one or both precursor ions of the pair with the processor; and The processor is used to instruct the collision-induced dissociation (CID) device of the tandem mass spectrometer to dissociate all other precursor ions of the peak list for the IDA experiment.

15. A computer program product comprising a non-transitory, tangible computer-readable storage medium having contents comprising a program, the instructions of the program being executed on a processor to perform a method for detecting and separately dissociating an alkali metal adduct of a compound in an information dependent acquisition (IDA) mass spectrometry experiment, the method comprising: Providing a system, wherein the system comprises one or more different software modules, and wherein the different software modules comprise a control module and an analysis module; Using the control module to instruct the ion source device to ionize one or more compounds in the sample to generate an ion beam; instructing, with the control module, a mass filter of a tandem mass spectrometer to transmit a mass range of precursor ions from the ion beam; Using the control module to instruct a mass analyzer of a tandem mass spectrometer to measure the intensity and mass-to-charge ratio (m / z) value of the precursor ion; selecting one or more of the precursor ions for a peak list of an IDA experiment using the analysis module; for each pair of precursor ions in the peak list of the IDA experiment, if the m / z difference within the pair corresponds to the m / z difference between one alkali metal ion and another alkali metal ion or a proton, instructing an electron-based dissociation (ExD) device of the tandem mass spectrometer, with the control module, to dissociate one or both precursor ions of the pair; and The control module is used to instruct the collision-induced dissociation (CID) device of the tandem mass spectrometer to dissociate all other precursor ions of the peak list of the IDA experiment.

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