Precursor Accumulation in Single Charge State in Mass Spectrometry

Abstract

To provide precursor accumulation in a single charge state in mass spectrometry.SOLUTION: An ion source ionizes a compound, producing precursor ions with different m / z values. A reagent source supplies a charge reducing reagent. An ion guide is positioned between a mass filter and both the ion source and the reagent source. The ion guide applies an AC voltage and DC voltage to its electrodes that create a pseudopotential to trap the precursor ions in the ion guide below a threshold m / z. This AC voltage, in turn, causes the trapped precursor ions to be charge-reduced by the reagent so that m / z values of the trapped precursor ions increase to a single m / z value above the threshold m / z. The ion guide applies the DC voltage to its electrodes relative to a DC voltage applied to electrodes of the mass filter that causes the precursor ions with m / z values increased beyond the single m / z value to be continuously transmitted to the mass filter.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] (Related Applications) This application claims the benefit of U.S. Provisional Patent Application No. 62 / 724,495, filed Aug. 29, 2018, the contents of which are incorporated herein by reference in their entirety.

[0002] (Introduction) The teachings herein relate to a mass spectrometer for reducing the charge of precursor ions of the same compound having different m / z values to continuously accumulate and transmit precursor ions at a single mass-to-charge ratio (m / z) value with a preset z charge state. More specifically, a Q0 ion guide is positioned between a Q1 mass filter device and both an ion source device and a reagent source device. The ion source device and the reagent source device are operated simultaneously or sequentially in time in various embodiments. The Q0 ion guide uses a pseudo-potential generated by an alternating current (AC) voltage applied at the exit of the Q0 ion guide or on a lens electrode on the Q0 ion guide to capture charge reduction reagents and two or more precursor ions with m / z values below a threshold m / z value. A DC voltage is also applied on the lens electrode, and the DC bias on the lens electrode is negative (positive) with respect to the DC bias on the Q0 ion guide for precursor ions having positive (negative) charges and for charge reduction ions. This AC voltage then charge-reduces the two or more captured precursor ions such that their m / z values increase to a single m / z value that exceeds the threshold m / z. The two or more precursor ions with m / z values increased to a single m / z value are continuously transmitted to the Q1 mass filter device by applying a DC voltage to the Q0 ion guide device with respect to the direct current (DC) voltage applied to the Q1 mass filter device. Q1 selects (or isolates) a charge-reduced species with a single m / z value and selects a target compound with a preset charge state. Using this method, the intensity of the isolated precursor is the sum of precursor ions with initially different charge states that is higher than a preset value given by a preset threshold.

[0003] The devices and methods disclosed herein may also be implemented in conjunction with a computer system such as a processor, controller, microcontroller, or the computer system of FIG. 1.

Background Art

[0004] (Background) (Precursor ions with different charge states) In mass spectrometry, electrospray ionization (ESI) can, for example, give precursor ions many different charge states. Since the mass-to-charge ratio (m / z) of the precursor ions depends on the charge, this in turn gives precursor ions a wide range of different m / z values in the case of large biomolecules such as proteins.

[0005] FIG. 2 is an exemplary plot 200 of the precursor ion mass spectrum for pure myoglobin showing how electrospray ionization (ESI) can generate precursor ions with many different m / z values. For example, bracket 210 indicates that the ESI of myoglobin can generate at least 17 precursor ions with different m / z values from 771 to 2,000.

[0006] In many conventional experiments, only one of the precursor ions of myoglobin is selected for analysis using a quadrupole ion filter (or Q1). For example, only the precursor ion of myoglobin with an m / z of 1413.82 is selected for fragmentation in a mass spectrometry / mass spectrometry (MS / MS) experiment. Selecting only one precursor ion means that the remaining precursor ions under bracket 210 with different m / z values are not considered or are lost.

[0007] Selecting only one precursor ion reduces the overall sensitivity of the measurement. Sensitivity is, for example, the observed change in ion current per molecule of interest. By selecting only the precursor ion of myoglobin with an m / z of 1413.82, the ion current from the remaining 16 precursor ions is lost, reducing the overall sensitivity.

[0008] One way to recapture sensitivity is to forego isolating a single precursor ion and apply MS / MS to all precursor ions. In other words, the 17 precursor ions in bracket 210 are selected from the background noise ions outside bracket 210 by Q1 set in broadband transmission so as to cover the precursor ions within bracket 210. Unfortunately, this method can often not be applied when the sample contains more than one protein or additional contaminants. In such cases, it may not be possible to distinguish the precursor ions of the protein of interest from the precursor ions of other proteins or contaminants.

[0009] Another way to recapture sensitivity is to essentially move two or more precursor ions to the same m / z value. McLuckey et al., Anal. Chem. 2002, 74, 336-346 (hereinafter referred to as the "McLuckey paper") provides a method for moving precursor ions, referred to as "ion residency". The McLuckey paper explains that prior to the development of the ion residency technique, it was well known that the ion charge associated with high-mass polyvalent ions could be manipulated.

[0010] For example, it was known that ions accumulated in an ion trap device could be mixed with a strong neutral base gas to generate an ion / molecule reaction that reduces the charge state of the ions. Similarly, it was known that the accumulated ions could also be mixed with ions of the opposite charge to generate a proton transfer reaction (PTR) and also reduce the charge state of the ions.

[0011] However, the McLuckey paper introduced a new technique in which the ion / ion PTR rate is blocked in a selective manner such that only specific ions are maintained in the trap. The McLuckey paper refers to this blocking of the ion / ion PTR as "ion trapping". To block the ion / ion PTR, the technique of the McLuckey paper applies a bipolar resonance excitation voltage to the endcap electrodes of a 3D quadrupole ion trap. The exemplary resonance excitation voltage described in the McLuckey paper has a frequency of about tens of thousands of Hertz.

[0012] The resonance excitation AC voltage is applied at the long-term frequency of the target precursor peak in a pre-set charge state so as to excite the species, and then the PTR is applied to a group of ions with multiple charge states. Since the PTR reaction rate is decreased by the high kinetic energy of the precursor ions, the PTR is stopped when the precursor charge state or m / z reaches the excited target.

[0013] Unfortunately, this approach is not implemented in commercial instruments due to the complex parameter settings required. Another problem with this approach is that the resonance excitation of the precursor ions has a very high probability of losing vulnerable post-translational modification parts such as glycosylation in the precursor ions. In other words, the resonance excitation of the precursor ions can fragment the precursor ions. Yet another problem with this approach is that it involves pulsed emission of PTR ions. The PTR ions remain in the trap. They are then all released from the trap at once for selection and analysis. This pulsed emission means that a large number of ions can be released at once. The release of a large number of ions at once can lead to saturation of the downstream mass analyzer due to space charge.

[0014] (Mass Spectrometry Background) Mass spectrometry (MS) is an analytical technique for the detection and quantification of chemical compounds based on the analysis of the m / z values of the ions formed from those compounds. MS involves ionization of one or more target compounds from a sample, generation of precursor ions, and mass analysis of the precursor ions.

[0015] Tandem mass spectrometry or mass spectrometry / mass spectrometry (MS / MS) involves ionization of one or more target compounds from a sample, selection of one or more precursor ions of one or more compounds, fragmentation of one or more precursor ions into product ions, and mass spectrometry of the product ions.

[0016] Both MS and MS / MS can provide qualitative and quantitative information. The measured precursor or product ion spectra can be used to identify the target molecule. The intensities of the precursor ions and product ions can also be used to quantify the amount of the compound present in the sample.

[0017] (Fragmentation Technique Background) Electron-based dissociation (ExD), collision-induced dissociation (CID), and ultraviolet (UV) or infrared (IR) photodissociation are often used as fragmentation techniques for tandem mass spectrometry (MS / MS). ExD can include, but is not limited to, electron capture dissociation (ECD), electron transfer dissociation (ETD), and electron impact excitation of ions from organic substances (EIEIO). CID is the most conventional technique for dissociation in tandem mass spectrometers. Summary of the Invention Means for Solving the Problems

[0018] (Abstract) An apparatus, method, and computer program product are disclosed for continuously accumulating and transmitting precursor ions at a single m / z value by reducing the charge of precursor ions of the same compound having different m / z values. The apparatus includes an ion source device, a reagent source device, a mass filter device, and an ion guide device.

[0019] The ion source device ionizes the compounds of the sample. This generates two or more precursor ions of compounds with different m / z values. The reagent source device supplies a charge reduction reagent.

[0020] The ion guide device is positioned between a mass filter device and both an ion source device and a reagent source device. The ion guide device receives two or more precursor ions from the ion source device and a charge reduction reagent from the reagent source device.

[0021] The ion guide device applies an AC voltage and a DC voltage to one or more electrodes of the ion guide device to generate a pseudo-potential and capture two or more received precursor ions having an m / z value below a threshold m / z within the ion guide device. This AC voltage, in turn, causes the two or more captured precursor ions to be charge-reduced by the received charge reduction reagent such that the m / z values of the two or more precursor ions increase to a single m / z value above the threshold m / z. The ion guide device also applies a DC voltage to one or more electrodes of the ion guide device relative to a DC voltage applied to an electrode of the mass filter device that continuously transmits two or more precursor ions having an m / z value increased to the single m / z value to the mass filter device.

[0022] These and other features of the applicant's teachings are described herein. The present invention provides, for example, the following items. (Item 1) An apparatus for reducing the charge of precursor ions of the same compound having different m / z values in order to continuously accumulate and transmit precursor ions at a single mass-to-charge ratio (m / z) value, an ion source device for ionizing a compound of a sample and generating two or more precursor ions of the compound with different m / z values, a reagent source device for supplying a charge reduction reagent, a mass filter device, an ion guide device positioned between the mass filter device and both the ion source device and the reagent source device, wherein the ion guide device receives the two or more precursor ions from the ion source device and the charge reduction reagent from the reagent source device, generates a pseudo potential, captures the received two or more precursor ions having an m / z value below a threshold m / z within the ion guide device, and thus, applies an alternating current (AC) voltage and a direct current (DC) voltage to one or more electrodes of the ion guide device to charge-reduce the captured two or more precursor ions by the received charge reduction reagent such that the m / z values of the two or more precursor ions increase to a single m / z value exceeding the threshold m / z, applies the DC voltage to the one or more electrodes with respect to a DC voltage applied to an electrode of the mass filter device for continuously transmitting the two or more precursor ions having an m / z value increased to the single m / z value to the mass filter device, an ion guide device and (Item 2) The apparatus according to Item 1, wherein the charge reduction reagent includes a neutral charge scavenger reagent. (Item 3) The apparatus according to Item 2, wherein the neutral charge scavenger reagent includes ammonia or acetone. (Item 4) The apparatus according to Item 1, wherein the charge reduction reagent source device includes a proton transfer reaction (PTR) reagent source device, the charge reduction reagent includes PTR reagent ions, and the ion guide device generates the pseudo potential and captures both the received two or more precursor ions and the received PTR reagent ions having an m / z value below the threshold m / z with each other, and applies the AC voltage to one or more electrodes of the ion guide device. (Item 5) The device according to item 1, wherein one or more electrodes of the ion guide device comprise rods of the ion guide device. (Item 6) The device according to item 1, wherein one or more electrodes of the ion guide device comprise electrodes of an exit aperture or a lens of the ion guide device. (Item 7) The device according to item 1, wherein the two or more precursor ions from the ion source device and the charge reduction reagent from the reagent source device are separately and continuously received by the same inlet of the ion guide device. (Item 8) The device according to item 7, wherein the two or more precursor ions from the ion source device and the charge reduction reagent from the reagent source device are separately and continuously introduced through an orifice and an ion guide to the same inlet of the ion guide device. (Item 9) The device according to item 7, wherein the ion guide device comprises a quadrupole, hexapole, or octupole ion guide device. (Item 10) The device according to item 1, wherein the two or more precursor ions from the ion source device and the charge reduction reagent from the reagent source device are continuously and simultaneously received at different inlets of the ion guide device. (Item 11) The device according to item 10, wherein the ion guide device comprises a chimeric device including eight L-shaped electrodes providing four branches, and a matched pair of branches receives the two or more precursor ions from the ion source device, and simultaneously, another matched pair of branches receives the charge reduction reagent from the reagent source device. (Item 12) The device according to item 10, further comprising a second ion guide device positioned between the ion guide device and the mass filter device, and applying a DC voltage to one or more electrodes of the ion guide device with respect to a DC voltage applied to electrodes of the second ion guide device and with respect to a DC voltage applied to electrodes of the mass filter device for continuously transmitting the two or more precursor ions with increased m / z values up to the single m / z value through the second ion guide device to the mass filter device. (Item 13) The apparatus according to item 10, further comprising an ExD device positioned after the mass filter device, wherein the mass filter device selects the two or more precursor ions with m / z values increased to the single m / z value, transmits the two or more precursor ions with m / z values increased to the single m / z value to the ExD device, and the ExD device fragments the two or more precursor ions with m / z values increased to the single m / z value. (Item 14) A method for reducing the charge of precursor ions of the same compound having different m / z values in order to continuously accumulate and transmit precursor ions at a single mass-to-charge ratio (m / z) value, using a processor to ionize a compound in a sample and instruct an ion source device to generate two or more precursor ions of the compound with different m / z values; using the processor to instruct a reagent source device to supply a charge reduction reagent; using the processor to instruct an ion guide device positioned between the mass filter device and both the ion source device and the reagent source device to receive the two or more precursor ions from the ion source device and the charge reduction reagent from the reagent source device; using the processor to generate a pseudo potential, capture the two or more received precursor ions with m / z values below a threshold m / z in the ion guide device, and thus charge reduce the two or more captured precursor ions with the received charge reduction reagent so that the m / z values of the two or more precursor ions increase to a single m / z value above the threshold m / z, and instruct the ion guide device to apply an alternating current (AC) voltage and a direct current (DC) voltage to one or more electrodes of the ion guide device; using the processor to instruct the ion guide device to apply the DC voltage to the one or more electrodes with respect to a DC voltage applied to an electrode of the mass filter device that continuously transmits the two or more precursor ions with m / z values increased to the single m / z value to the mass filter device comprising the method. (Item 15) A computer program product comprising a non-transitory tangible computer-readable storage medium, the content of the non-transitory tangible computer-readable storage medium including a program with instructions executable on a processor to implement a method for reducing the charge of precursor ions of the same compound having different m / z values in order to continuously accumulate and transmit precursor ions at a single mass-to-charge ratio (m / z) value, the method comprising: Providing a system, the system comprising one or more distinct software modules, the distinct software modules comprising a control module; Using the control module to command an ion source device to ionize a compound of a sample and generate two or more precursor ions of the compound with different m / z values; Using the control module to command a reagent source device to supply a charge reduction reagent; Using the control module to command an ion guide device positioned between a mass filter device and both the ion source device and the reagent source device to receive the two or more precursor ions from the ion source device and the charge reduction reagent from the reagent source device; Using the control module to generate an alternating current (AC) voltage and a direct current (DC) voltage, capture the two or more received precursor ions having m / z values below a threshold m / z within the ion guide device, and thereby reduce the charge of the captured two or more precursor ions by the received charge reduction reagent such that the m / z values of the two or more precursor ions increase to a single m / z value above the threshold m / z, and command the ion guide device to apply the AC voltage and the DC voltage to one or more electrodes of the ion guide device; Using the control module to command the ion guide device to apply the DC voltage to one or more electrodes of the ion guide device with respect to a DC voltage applied to an electrode of the mass filter device to continuously transmit the two or more precursor ions having m / z values increased to the single m / z value to the mass filter device; A computer program product, comprising:

[0023] One of ordinary skill in the art will understand that the drawings described below are for illustrative purposes only and are not intended to limit the scope of the present teachings in any way.

Brief Description of the Drawings

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[0035] Before one or more embodiments of the present teachings are described in detail, those skilled in the art will understand that the present teachings are not limited to the details of the structures, arrangements of components, and arrangements of steps described in the following detailed description or illustrated in the drawings in their applications. It should also be understood that the phrases and terminology used herein are for the purpose of explanation and should not be regarded as limiting.

[0036] (Description of Various Embodiments) (Computer-Implemented System) FIG. 1 is a block diagram illustrating a computer system 100 in which an embodiment of the present teachings may be implemented. The computer system 100 includes a bus 102 or other communication mechanism for communicating information, and a processor 104 coupled to the bus 102 for processing information. The computer system 100 also includes a memory 106, which may be a random access memory (RAM) or other dynamic storage device, coupled to the bus 102 for storing instructions to be executed by the processor 104. The memory 106 may also be used to store temporary variables or other intermediate information during the execution of instructions to be executed by the processor 104. The computer system 100 further includes a read-only memory (ROM) 108 or other static storage device coupled to the bus 102 for storing static information and instructions for the processor 104. A storage device 110, such as a magnetic disk or optical disk, is provided for storing information and instructions and is coupled to the bus 102.

[0037] Computer system 100 may be coupled via 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 bus 102 for communicating information and command selections to processor 104. Another type of user input device is a cursor control 116, such as a mouse, trackball, or cursor direction keys, for communicating direction information and command selections to processor 104 and for controlling cursor movement on display 112. This input device typically has two degrees of freedom in two axes, namely, a first axis (i.e., x) and a second axis (i.e., y), which enable the device to define a position within a plane.

[0038] Computer system 100 can implement the present teachings. According to one implementation of the present teachings, results are provided by computer system 100 in response to processor 104 executing one or more sequences of one or more instructions contained within memory 106. Such instructions may be read into memory 106 from another computer-readable medium, such as storage device 110. Execution of the sequence of instructions contained within memory 106 causes processor 104 to perform the processes described herein. Alternatively, wired circuitry may be used in place of or in combination with software instructions to implement the present teachings. Accordingly, implementations of the present teachings are not limited to any specific combination of hardware circuitry and software.

[0039] In various embodiments, computer system 100 can be connected to one or more other computer systems, such as computer system 100, across 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 data and supply it to other computer systems. One or more computer systems that store and supply data can be referred to as servers or, in a cloud computing scenario, the cloud. One or more computer systems can include, for example, one or more web servers. Other computer systems that send data to and receive data from a server or the cloud can be referred to as clients or cloud devices, for example.

[0040] As used herein, the term "computer-readable medium" refers to any medium that participates in providing instructions to processor 104 for execution. Such a medium can take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks such as storage device 110. Volatile media includes dynamic memory such as memory 106. Transmission media includes coaxial cables, copper wire, and fiber optics, including the wires that make up bus 102.

[0041] A general form of a computer-readable medium or computer program product can include, for example, a floppy disk, flexible disk, hard disk, magnetic tape, or any other magnetic medium, a CD-ROM, a digital video disk (DVD), a Blu-ray (registered trademark) disk, any other optical medium, a thumb drive, a memory card, RAM, PROM, and EPROM, flash EPROM, any other memory chip or cartridge, or any other tangible medium readable by a computer.

[0042] 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 first be carried on a magnetic disk of a remote computer. The remote computer can load the instructions into its dynamic memory and use a modem to send the instructions via a telephone line. A modem local to computer system 100 can receive data on the telephone line and use an infrared transmitter to convert the data into an infrared signal. 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 where processor 104 reads and executes the instructions. The instructions received by memory 106 may optionally be stored on storage device 110 either before or after execution by processor 104.

[0043] According to various embodiments, instructions configured to be executed by a processor to implement a method are stored on a computer-readable medium. The computer-readable medium can be a device that stores digital information. For example, the computer-readable medium includes a compact disc read-only memory (CD-ROM) as known in the art for storing software. The computer-readable medium is accessed by a suitable processor to execute the instructions configured to be executed.

[0044] The following description of various implementations of the present teachings is presented for purposes of illustration and description. It is not exhaustive and does not limit the present teachings to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be obtained from practice of the present teachings. In addition, the implementations described include software, but the present teachings may be implemented as a combination of hardware and software, or in hardware alone. The present teachings may be implemented using both object-oriented and non-object-oriented programming systems.

[0045] (Pseudo-potential ion accumulation and charge reduction) As described above and as shown in FIG. 2, electrospray ionization (ESI) can, for example, give many different charge states to the precursor ions of a protein. Since the mass-to-charge ratio (m / z) of the precursor ions depends on the charge, this can, in turn, give a number of different m / z values to the precursor ions of a single protein.

[0046] In many experiments, only one of the precursor ions of the compound of interest is selected for analysis. However, this reduces the overall sensitivity of the analysis. One way to recapture sensitivity is to essentially move two or more precursor ions to the same m / z value. The McLuckey paper provides a method of moving precursor ions, called ion trapping. In this technique, an ion / ion proton transfer reaction (PTR) is blocked at a selected charge state or m / z value by applying a resonant excitation voltage to the endcap electrodes of a 3D quadrupole ion trap. Unfortunately, this approach requires complex parameter settings, can fragment the precursor ions, and can cause saturation problems due to the pulsed emission of charge-reduced precursor ions.

[0047] In various embodiments, precursor ions are accumulated in the ion guide in the same charge state without using resonant excitation. Instead, an additional alternating current (AC) voltage is applied to all the rods of the ion guide or to the exit aperture or lens of the ion guide to create a pseudo-potential voltage barrier through which only precursor ions that have reached a certain m / z value can be transmitted.

[0048] In the McLuckey paper, the additional AC resonant excitation applied to the ion trap is given a frequency corresponding to the m / z value at which charge reduction is blocked. This frequency excites the ions at this m / z value with higher kinetic energy, preventing them from reacting with the charge reduction reagent. Unfortunately, this higher kinetic energy can also fragment these precursor ions.

[0049] In contrast, the additional AC voltage applied to the ion guide generates a pseudo-potential barrier that, in various embodiments, prevents precursor ions with m / z values below the threshold m / z value from moving axially between the Q0 ion guide and the Q1 filter. This allows them to continue to react with the charge reduction reagent. The amplitude of the additional AC voltage is proportional to the square root of the threshold m / z value. As a result, decreasing the amplitude of the AC voltage decreases the threshold m / z value.

[0050] In the case of ion residence applied to a linear RFQ such as Q0, the AC voltage is applied radially to excite the long-term frequency of the charge reduction species. In contrast, in various embodiments, the AC voltage is applied axially, which does not induce resonant excitation radially. Instead, this generates a potential barrier between the Q0 ion guide rods at the exit of the Q0 ion guide. There are at least two options for applying the AC voltage to the Q0 ion guide. One is that the AC voltage is applied on the Q0 rods such that an AC electric field is applied between the Q0 rod set and the lens electrode installed at the exit of the Q0 (or IQ1 electrode) ion guide. Another option is that the AC voltage is applied at the IQ1 electrode.

[0051] To generate a mass-selective threshold, a DC bias is applied between the IQ1 electrode and the Q0 ion guide. For precursor ions with a positive charge, IQ1 is set negative with respect to the Q0 ion guide. For precursor ions with a negative charge, IQ1 is set positive with respect to the Q0 ion guide.

[0052] In a quadrupole ion guide, for example, an appropriate radio frequency (RF) voltage is applied to opposite electrode pairs within the ion guide to confine ions radially. In various embodiments, an additional AC voltage is superimposed across the RF voltage to generate an axial pseudo-potential barrier at the exit of Q0. Background information on pseudo-potentials can be found in Gerlich, RF Ion Guides in “The Encyclopedia of Mass Spectrometry,” Vol 1, 182-194 (2003), which is incorporated herein by reference.

[0053] U.S. Patent No. 7,456,388, issued November 25, 2008 (hereinafter the “‘388 patent”), which is incorporated herein by reference, describes, for example, an ion guide for concentrating ion packets. The ‘388 patent provides, for example, an apparatus and method that enable the analysis of ions over a wide m / z range, substantially without transmission loss. The emission of ions from the ion guide is affected by generating conditions such that all ions (regardless of m / z) arrive at a designated point within a space such as an extraction region of a time-of-flight (TOF) mass analyzer or an accelerator, for example, using substantially the same energy, in a desired sequence or at a desired time. Ions bunched in such a manner can then be manipulated as a group, for example, by being extracted using a TOF extraction pulse and propelled along a desired path to arrive at the same spot on a TOF detector.

[0054] To emit ions from the ion guide such that all ions arrive at a desired location at a desired time using substantially the same energy, the '388 patent applies an additional AC voltage to the ion guide. This additional AC voltage creates a pseudo-potential barrier. In the '388 patent, the amplitude of the AC voltage is initially set to allow only the emission of ions with the maximum m / z value. Then, the amplitude of the AC voltage is stepped down gradually to vary the depth of the pseudo-potential well and allow ions with increasingly smaller m / z values to be emitted from the ion guide. In other words, in the '388 patent, the AC voltage amplitude is scanned.

[0055] In various embodiments, the AC voltage applied to the ion guide is not scanned. One AC voltage amplitude is set to correspond to an m / z threshold. Additionally, the AC voltage is not used to continuously emit ions of different m / z values. Instead, the AC voltage is used to create a barrier such that ions that reach the threshold m / z value after charge reduction due to PTR are continuously emitted.

[0056] FIG. 3 is a schematic diagram 300 of an apparatus for reducing the charge of precursor ions of the same compound having different m / z values to continuously accumulate and transmit precursor ions at a single m / z value using an ion guide in which sample ions and reagents are simultaneously received through different ports according to various embodiments. The apparatus of FIG. 3 includes an ion source device 311, a reagent source device 312, a Q1 mass filter device 318, and a Q0 ion guide device 315. The apparatus is, for example, part of a mass spectrometer 310.

[0057] The ion source device 311 ionizes a sample compound and generates two or more precursor ions of the compound with different m / z values. The two or more precursor ions are received by the Q0 ion guide device 315 through, for example, an orifice and skimmer 313, and a Q jet 314. Two or more precursor ions of the compound myoglobin with different m / z values are shown, for example, in FIG. 2.

[0058] Returning to FIG. 3, the reagent source device 312 supplies the PTR reagent to the Q0 ion guide device 315. Two or more precursor ions and the PTR reagent are supplied to the Q0 ion guide device 315 simultaneously and continuously. This is possible because the Q0 ion guide device 315 includes at least two separate inlet ports.

[0059] The Q0 ion guide device 315 is, for example, also the chimeric device shown in FIGS. 4 and 5. The chimeric device includes eight L-shaped electrodes that provide four branches. A matched pair of branches receives two or more precursor ions from the ion source device 311. At the same time, another matched pair of branches receives the PTR reagent from the reagent source device 312.

[0060] FIG. 4 is a schematic diagram 400 of a chimeric device configured as an ExD cell according to various embodiments. The chimeric device for ExD includes an electron emitter or filament 410 and an electron gate 420. Electrons are emitted perpendicular to the flow of ions 430 and parallel to the direction of the magnetic field 440.

[0061] Returning to FIG. 3, since the Q0 ion guide device 315 is not used for fragmentation, the chimeric device need not include an electron source or any other device necessary to implement ExD.

[0062] FIG. 5 is a three-dimensional perspective view 500 of the chimeric device according to various embodiments. FIG. 5 shows the direction of flow of sample compound ions 510 through the chimeric device. FIG. 5 also shows that the PTR reagent can be added to the chimeric device in the direction 520.

[0063] Returning to FIG. 3, two or more precursor ions and the PTR reagent are supplied to a Q0 ion guide device 315 having a chimeric structure to reduce the charge state of the two or more precursor ions. However, without a certain degree of trapping force, the two or more precursor ions will simply pass through the Q0 ion guide device 315. To trap the two or more precursor ions within the Q0 ion guide device 315, an AC voltage is applied to all the rods of the Q0 ion guide device 315 using, for example, an AC voltage source 322. In various alternative embodiments, the AC voltage is applied to the electrodes of the exit aperture or the IQ1 lens 316. As described above, the AC voltage generates a pseudo-potential received by the two or more precursor ions.

[0064] Plot 340 depicts the potential received by different precursor ions at different locations within the mass spectrometer 310. For example, line 341 depicts the DC potential received by all precursor ions between the Q0 ion guide device 315 and the mass filter device 318. Line 342 depicts the combined AC and DC (pseudo) potential received by precursor ions with m / z values below the threshold m / z value. Line 342 indicates that there is a barrier preventing these ions from moving to the Q1 mass filter device 318.

[0065] Line 343 depicts the combined AC and DC (pseudo) potential received by precursor ions with m / z values above the threshold m / z value. Line 343 indicates that there is no barrier preventing these ions from moving to the Q1 mass filter device 318. Reagent ions with opposite charge signs are always trapped within Q0 regardless of their m / z values because the DC potential acts as a trapping barrier.

[0066] Plot 340 shows that the AC voltage captures precursor ions with m / z values below the threshold m / z value, but also allows precursor ions with m / z values above the threshold m / z value to continuously move to the mass filter device 318. The AC voltage captures precursor ions with m / z values below the threshold m / z value, and since the Q0 ion guide device 315 is supplied with the PTR reagent, these captured precursor ions are charge-reduced by the PTR reagent until their m / z values increase above the threshold m / z. Thus, the AC voltage limits the PTR.

[0067] The PTR reagent can include, for example, ions with a negative charge. Alternatively, the PTR reagent can include neutral charge scavenger ions such as ammonia or acetone. In this case, mutual capture is not required.

[0068] The DC potential 341 within plot 340 is generated, for example, by setting the DC voltage of the exit aperture or IQ1 lens 316 lower than the DC voltage of the rods of the Q0 ion guide device 315. Additionally, the DC voltage of the optional ST1 ion guide device 317 is set lower than the exit aperture or IQ1 lens 316, and the DC voltage of the Q1 mass filter device 318 is set lower than the DC voltage of the rods of the Q0 ion guide device 315. By combining the DC voltage and the pseudo-potential generated by the AC voltage in the vicinity of the exit aperture or IQ1 lens 316, the Q0 ion guide device 315 performs high m / z filter extraction.

[0069] Due to the PTR, the charge state of the precursor ions within the Q0 ion guide device 315 is continuously decreasing, and their m / z values are increasing. When the m / z value of the precursor ions reaches an m / z higher than the m / z extraction threshold, the ions are extracted from the Q0 ion guide device 315. Since there is no PTR reagent outside the Q0 ion guide device 315, further charge reduction is stopped. This means that the charge state of the precursor ions accumulates at a single value determined by the high m / z extraction threshold.

[0070] Figure 6 is an exemplary plot 600 of precursor ions for myoglobin, hypothetically showing how the m / z values of these precursor ions are increased using the apparatus of FIG. 3 according to various embodiments. Brackets 210 delimit, again, at least 17 precursor ions of myoglobin with different m / z values, for example, from 771 to 2,000. However, when an AC voltage is applied to the apparatus of FIG. 3 such that an m / z threshold is generated at about 1,413 Da, 12 precursor ions within brackets 210 with m / z below 1,413 are charge-reduced. This increases the m / z values of the 12 precursor ions to a single m / z of 1,413.82, as indicated, for example, by the arrows in FIG. 6. As a result, the intensity of a total of 13 precursor ions is found here at 1,413.83. When this m / z value is selected here and used for mass spectrometry or fragmentation, the sensitivity is significantly improved.

[0071] However, brackets 620 indicate a setting where the m / z threshold at 1,413 does not integrate all of the precursor ions at 1,413.82 Da. Four precursor ions have m / z values above this value and are transmitted without being charge-reduced. The ion current contribution from these four precursor ions is not included only when a single m / z of 1,413.82 is selected by the mass filter device. In other words, not setting the m / z threshold close to the m / z value of the precursor ion with the highest m / z value can leave some precursor ions unused.

[0072] Collecting ion current from many of the precursor ions having lower m / z values results in a high percentage of the ion current that is possible as a total, so it is not a significant problem. Additionally, setting the threshold m / z value overly high can cause other problems. For example, a mass filter device may not be able to select ions at the highest m / z value of the precursor ions. Also, reaching increasingly higher m / z values requires a longer PTR time. In some experiments, there may not be enough time for the PTR to wait for the precursor ions with the lowest m / z value to move to the m / z value of the precursor ions with the highest m / z value. Another problem can be lower dissociation efficiency after electron capture in an ExD experiment when the precursor charge state is overly high.

[0073] Figure 7 is an exemplary hypothetical plot 700 of precursor ions for myoglobin that is hypothetically transmitted from the Q0 ion guide device of FIG. 3 to the Q1 mass filter device according to various embodiments. Figure 7 shows that the Q0 ion guide device 315 of FIG. 3 acts as a high m / z extraction filter or a high m / z pass filter. Only precursor ions with m / z values above the m / z threshold at approximately 1413 are shown here in Figure 7. The precursor ion with an m / z value of 1413.82 here includes ion current from 13 precursor ions (the first precursor ion and 12 that have been charge-reduced and moved to this m / z value). Parentheses 620 indicate that 4 precursor ions with m / z values above the m / z threshold are still there. Additionally, several other high m / z ions that can be protein precursor ions, precursor ions from other proteins, or contaminant precursor ions are present. As a result, the Q1 mass filter device 318 of FIG. 3 is used to select the improved precursor ions with an m / z value of 1413.82 and remove the remaining precursor ions with different charge states and the high m / z contaminant ions generated from the impurities shown in Figure 7.

[0074] FIG. 8 is an exemplary hypothetical plot 800 of precursor ions for pure myoglobin hypothetically selected and transmitted by the Q1 mass filter device of FIG. 3 according to various embodiments. FIG. 8 shows that the Q1 mass filter device 318 of FIG. 3 acts as a band-pass m / z extraction filter. Here, only precursor ions with an m / z value of 1413.82, as shown in FIG. 8, are selected and transmitted. The Q1 mass filter device 318 of FIG. 3 effectively removes all other precursor ions with m / z values above the threshold m / z.

[0075] Returning to FIG. 3, the Q1 mass filter device 318 here transmits the selected precursor ions downstream of the other components of the mass spectrometer 310 for mass spectrometry or fragmentation. For example, the accumulated and isolated precursor ions enable high-sensitivity ExD analysis. The mass spectrometer 310 includes, for example, a second Q2 chimera device 319 that can be used to apply ExD to the precursor ions selected by the Q1 mass filter device 318. Alternatively, the mass spectrometer 310 includes a Q2CID collision cell 320 that can be used to apply CID to the precursor ions selected by the Q1 mass filter device 318. The generated ions are then mass analyzed by the mass analyzer device 321.

[0076] In yet a further alternative embodiment, the accumulated and isolated precursor ions may simply be mass analyzed. In this case, the precursor ions selected by the Q1 mass filter device 318 are simply transmitted to the mass analyzer device 321 by the Q2 chimera device 319 and the Q2CID collision cell 320.

[0077] The Q0 ion guide device 315 filters and charge-reduces the continuous flow of precursor ions from the ion source device 311, but in various embodiments, the ions in the Q0 ion guide device 315 are periodically refreshed or discarded to empty the Q0 ion guide device 315. Periodically emptying the Q0 ion guide device 315, for example, prevents the accumulation of contaminant ions.

[0078] FIG. 9 is a schematic diagram 900 of the apparatus of FIG. 3 in which a Q0 ion guide device that simultaneously receives sample ions and reagents through different ports according to various embodiments is replaced by a Q0 ion guide device that separately and continuously receives sample ions and reagents through the same port. Specifically, the chimeric Q0 ion guide device 315 of FIG. 3 is replaced by the multipole Q0 ion guide device 915 of FIG. 9. The multipole Q0 ion guide device 915 can be, but is not limited to, a quadrupole, hexapole, or octupole.

[0079] The ion source device 311 and the reagent source device 312 here each transmit their two or more precursor ions and reagents to the Q0 ion guide device 915 through a single inlet port of the Q0 ion guide device 915. The two or more precursor ions and reagents are transmitted, for example, through the orifice and skimmer 313 and the ion guide 314. Since the two or more precursor ions and reagents use the same ion path, they need to be transmitted separately and continuously. For example, first, the two or more precursor ions are transmitted to the Q0 ion guide device 915. Then, the ion source device 311 is stopped and the reagent source device 312 is opened to transmit the charge reduction reagent to the Q0 ion guide device 915. In various embodiments, the charge reduction reagent is introduced by the reagent source device 312 through the orifice and skimmer 313 and the ion guide 314 when negative chemical ionization is used at atmospheric pressure.

[0080] (Pseudo-potential capture and charge reduction device) Returning to FIG. 3, the mass spectrometer 310 includes a device for reducing the charge of precursor ions of the same compound having different m / z values in order to continuously accumulate and transmit precursor ions at a single m / z value. The device includes an ion source device 311, a reagent source device 312, a Q1 mass filter device 318, and a Q0 ion guide device 315.

[0081] The ion source device 311 ionizes the sample compounds of the sample. This generates two or more precursor ions of the compounds with different m / z values. The ion source device 311 can be, but is not limited to, an electrospray ionization source (ESI) device, an electron impact source and a fast atom bombardment source 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 a preferred embodiment, the ion source device 311 is an ESI device.

[0082] The reagent source device 312 supplies a charge reduction reagent. The charge reduction reagent can be a neutral molecule or a charged ion.

[0083] The Q1 mass filter device 318 is shown as a quadrupole. However, the Q1 mass filter device 318 can be any type of mass filter such as a magnetic sector type mass spectrometer.

[0084] The Q0 ion guide device 315 is positioned between the Q1 mass filter device 318 and both the ion source device 311 and the reagent source device 312. The Q0 ion guide device 315 receives two or more precursor ions from the ion source device 311 and the charge reduction reagent from the reagent source device 312. The Q0 ion guide device 315 generates a pseudo potential and applies an AC voltage to one or more electrodes of the Q0 ion guide device 315 to capture two or more received precursor ions with m / z values below a threshold m / z within the Q0 ion guide device 315. This AC voltage, in turn, causes the two or more captured precursor ions to be charge-reduced by the received charge reduction reagent such that the m / z values of the two or more precursor ions increase to a single m / z value above the threshold m / z. The Q0 ion guide device 315 applies a DC voltage to one or more electrodes of the Q0 ion guide device 315 relative to the DC voltage applied to the electrodes of the mass filter device 318 to continuously transmit two or more precursor ions with m / z values increased to a single m / z value to the mass filter device 318.

[0085] In various embodiments, the charge reduction reagent supplied by the reagent source device 312 can be a neutral charge scavenger reagent. The neutral charge scavenger reagent can include, but is not limited to, ammonia or acetone.

[0086] In various alternative embodiments, the reagent source device 312 is a PTR reagent source device. The charge reduction reagent includes PTR reagent ions. In addition, the ion guide device 315 applies an AC voltage and mutually captures both two or more precursor ions received with m / z values below the threshold m / z and the received PTR reagent ions.

[0087] In various embodiments, one or more electrodes of the Q0 ion guide device 315 are rods of the Q0 ion guide device 315. In various alternative embodiments, one or more electrodes of the Q0 ion guide device 315 include the exit aperture of the Q0 ion guide device 315 or the IQ1 lens 316.

[0088] Returning to FIG. 9, in various embodiments, two or more precursor ions from the ion source device 311 and the charge reduction reagent from the reagent source device 312 are separately and continuously received by the same inlet of the Q0 ion guide device 915. Two or more precursor ions from the ion source device 311 and the charge reduction reagent from the reagent source device 312 are separately and continuously introduced through the orifice and skimmer 313 and the ion guide 314 to the same inlet of the Q0 ion guide device 915. The Q0 ion guide device 915 is, for example, a multipole ion guide. The Q0 ion guide device 915 can be, but is not limited to, a quadrupole, hexapole, or octapole ion guide device.

[0089] Returning to FIG. 3, in various embodiments, two or more precursor ions from the ion source device 311 and the charge reduction reagent from the reagent source device 312 are continuously and simultaneously received at different inlets of the Q0 ion guide device 315.

[0090] In various embodiments, the Q0 ion guide device 315 is a chimeric device. The device includes eight L-shaped electrodes that provide four branches. A matched pair of branches receives two or more precursor ions from the ion source device 311. At the same time, another matched pair of branches receives a charge reduction reagent from the reagent source device 312.

[0091] In various embodiments, a second ST1 ion guide device 317 is positioned between the Q0 ion guide device 315 and the Q1 mass filter device 318. The Q0 ion guide device 315 applies a DC voltage to one or more electrodes of the Q0 ion guide device 315 relative to the DC voltage applied to the electrodes of the second ST1 ion guide device 317 and relative to the DC voltage applied to the electrodes of the Q1 mass filter device 318. The DC voltage applied to one or more electrodes of the Q0 ion guide device 315 continuously transmits two or more precursor ions with m / z values increased to a single m / z value through the second ST1 ion guide device 317 to the Q1 mass filter device 318.

[0092] In various embodiments, an ExD device is positioned after the Q1 mass filter device 318. The ExD device is, for example, a second Q2 chimeric device 319. The Q1 mass filter device 318 selects two or more precursor ions with m / z values increased to a single m / z value and transmits the two or more precursor ions with m / z values increased to a single m / z value to the ExD device. The ExD device fragments the two or more precursor ions with m / z values increased to a single m / z value.

[0093] In various embodiments, the processor 330 is used to control instructions or provide to and analyze data collected by the ion source device 311, reagent source device 312, Q1 mass filter device 318, and Q0 ion guide device 315. The processor 330 controls or provides instructions, for example, by controlling one or more voltage, current, or pressure sources (not shown). The processor 330 can be a separate device as shown in FIG. 3, or can be a processor or controller of one or more devices of the mass spectrometer 310. The processor 330 can be, but is not limited to, a controller, computer, microprocessor, the computer system of FIG. 1, or any device capable of transmitting and receiving control signals and data.

[0094] (Method for pseudo-potential capture and charge reduction) FIG. 10 is a flowchart showing a method 1000 for reducing the charge of precursor ions of the same compound having different m / z values to continuously accumulate and transmit precursor ions at a single m / z value, according to various embodiments.

[0095] In step 1010 of method 1000, the ion source device is instructed, using the processor, to ionize a sample compound and generate two or more precursor ions of the compound with different m / z values.

[0096] In step 1020, the reagent source device is instructed, using the processor, to supply a charge reduction reagent.

[0097] In step 1030, an ion guide device positioned between the mass filter device and both the ion source device and the reagent source device is instructed, using the processor, to receive two or more precursor ions from the ion source device and the charge reduction reagent from the reagent source device.

[0098] In step 1040, the ion guide device is instructed to apply an AC voltage and a DC voltage to one or more electrodes of the ion guide device using a processor to generate a pseudo-potential and capture two or more received precursor ions with m / z values below a threshold m / z within the ion guide device. This AC voltage, in turn, charge-reduces the two or more captured precursor ions with a charge-reducing reagent such that the m / z values of the two or more precursor ions increase to a single m / z value above the threshold m / z.

[0099] In step 1050, the ion guide device is instructed to apply a DC voltage to one or more electrodes with respect to the DC voltage applied to the electrodes of the mass filter device using a processor. This DC voltage applied to one or more electrodes of the ion guide device continuously transmits two or more precursor ions with m / z values increased to a single m / z value to the mass filter device.

[0100] (Computer Program Product for Pseudo-Potential Capture and Charge Reduction) In various embodiments, the computer program product includes a tangible computer-readable storage medium containing a program with instructions that, when executed on a processor, implement a method for reducing the charge of precursor ions of the same compound having different m / z values to continuously accumulate and transmit precursor ions at a single m / z value. This method is implemented by a system that includes one or more distinct software modules.

[0101] FIG. 11 is a schematic diagram of a system 1100 that includes one or more distinct software modules that implement a method for reducing the charge of precursor ions of the same compound having different m / z values to continuously accumulate and transmit precursor ions at a single m / z value, according to various embodiments. System 1100 includes a control module 1110.

[0102] The control module 1110 commands the ion source device to ionize the sample compounds and generate two or more precursor ions of compounds with different m / z values. The control module 1110 commands the reagent source device to supply a charge reduction reagent. The control module 1110 commands an ion guide device positioned between the mass filter device and both the ion source device and the reagent source device to receive two or more precursor ions from the ion source device and the charge reduction reagent from the reagent source device.

[0103] The control module 1110 commands the ion guide device to apply an AC voltage and a DC voltage to one or more electrodes of the ion guide device to generate a pseudo-potential and capture two or more received precursor ions with m / z values below a threshold m / z within the ion guide device. This AC voltage, in turn, charge-reduces the two or more captured precursor ions by the received charge reduction reagent such that the m / z values of the two or more precursor ions increase to a single m / z value above the threshold m / z.

[0104] The control module 1110 commands the ion guide device to apply a DC voltage to one or more electrodes with respect to the DC voltage applied to the electrodes of the mass filter device. This DC voltage applied to one or more electrodes of the ion guide device continuously transmits two or more precursor ions with m / z values increased to a single m / z value to the mass filter device.

[0105] The present teachings are described in conjunction with various embodiments, but the present teachings are not intended to be limited to such embodiments. In contrast, the present teachings include various alternatives, modifications, and equivalents, as would be understood by one of ordinary skill in the art.

[0106] Furthermore, when describing various embodiments, this specification may present methods and / or processes as a particular sequence of steps. However, unless a method or process depends on a particular order of the steps described herein, the method or process should not be limited to the particular sequence of steps described. As will be understood by those skilled in the art, other sequences of steps may be possible. Accordingly, the particular order of steps described herein should not be construed as a limitation with respect to the claims. Additionally, claims directed to methods and / or processes should not be limited to the performance of those steps in the written order, and one skilled in the art can readily understand that the sequence can be varied and still remain within the spirit and scope of the various embodiments.

Claims

1. An apparatus for reducing the charge of precursor ions of the same compound having different mass-to-charge ratio (m / z) values ​​in order to successively store and transmit the precursor ions at a single m / z value, the apparatus comprising: an ion source device for ionizing a compound of the sample and generating two or more precursor ions of said compound having different m / z values; a reagent source device for providing a charge-reducing reagent; A mass filter device; an ion guide device positioned between the mass filter device and both the ion source device and the reagent source device; Equipped with the ion guide device receives the two or more precursor ions from the ion source device and the charge-reducing reagent from the reagent source device, and applies an alternating current (AC) voltage and a direct current (DC) voltage to one or more electrodes of the ion guide device; the AC voltage and the DC voltage generate a pseudopotential to trap the received two or more precursor ions having m / z values ​​below a threshold m / z in the ion guide device, thereby causing the trapped two or more precursor ions to be charge reduced by the received charge-reducing reagent such that the m / z values ​​of the two or more precursor ions increase to a single m / z value above the threshold m / z; wherein the DC voltage applied by the ion guide device to the one or more electrodes is set based on a DC voltage applied to an electrode of the mass filter device, thereby causing the two or more precursor ions having m / z values ​​increased up to the single m / z value to be transmitted successively to the mass filter device.

2. The device of claim 1, wherein the charge reducing reagent comprises a neutral charge scavenger reagent.

3. The apparatus of claim 2, wherein the neutral charge scavenger reagent comprises ammonia or acetone.

4. The apparatus of claim 1, wherein the charge reduction reagent source device comprises a proton transfer reaction (PTR) reagent source device, the charge reduction reagent including PTR reagent ions, and the ion guide device applies the AC voltage to the one or more electrodes of the ion guide device, the AC voltage generating the pseudopotential to mutually capture both the accepted two or more precursor ions having m / z values ​​below the threshold m / z and the accepted PTR reagent ions.

5. The apparatus of claim 1, wherein the one or more electrodes of the ion guide device comprise a rod of the ion guide device.

6. The apparatus of claim 1, wherein the one or more electrodes of the ion guide device comprise electrodes of an exit aperture or lens of the ion guide device.

7. The apparatus described in claim 1, wherein the two or more precursor ions from the ion source device and the charge-reducing reagent from the reagent source device are received separately and consecutively by the same inlet of the ion guide device.

8. The apparatus described in claim 7, wherein the two or more precursor ions from the ion source device and the charge-reducing reagent from the reagent source device are separately and continuously introduced into the same inlet of the ion guide device through an orifice and an ion guide.

9. The apparatus of claim 7, wherein the ion guide device comprises a quadrupole, hexapole, or octapole ion guide device.

10. The apparatus of claim 1, wherein the two or more precursor ions from the ion source device and the charge-reducing reagent from the reagent source device are received continuously and simultaneously at different inlets of the ion guide device.

11. The apparatus described in claim 10, wherein the ion guide device comprises a chimeric device including eight L-shaped electrodes providing four branches, wherein an aligned pair of branches receives the two or more precursor ions from the ion source device, while another aligned pair of branches receives the charge-reducing reagent from the reagent source device.

12. The apparatus of claim 10, further comprising a second ion guide device positioned between the ion guide device and the mass filter device, wherein a direct current (DC) voltage applied by the ion guide device to the one or more electrodes of the ion guide device is set based on a DC voltage applied to an electrode of the second ion guide device, and the direct current (DC) voltage applied by the ion guide device is further set based on a DC voltage applied to an electrode of the mass filter device, thereby causing the two or more precursor ions having m / z values ​​increased up to the single m / z value to be continuously transmitted through the second ion guide device to the mass filter device.

13. The apparatus of claim 10, further comprising an ExD device positioned after the mass filter device, the mass filter device selecting the two or more precursor ions having m / z values ​​increased to the single m / z value and transmitting the two or more precursor ions having m / z values ​​increased to the single m / z value to the ExD device, which fragments the two or more precursor ions having m / z values ​​increased to the single m / z value.

14. A method for reducing the charge of precursor ions of the same compound having different mass-to-charge ratio (m / z) values ​​for successively storing and transmitting precursor ions at a single m / z value, the method comprising: using a processor to instruct an ion source device to ionize a compound of the sample and generate two or more precursor ions of said compound having different m / z values; using the processor to instruct a reagent source device to supply a charge-reducing reagent; using the processor to instruct an ion guide device positioned between a mass filter device and both the ion source device and the reagent source device to receive the two or more precursor ions from the ion source device and the charge reduced reagent from the reagent source device; instructing the ion guiding device to apply alternating current (AC) and direct current (DC) voltages to one or more electrodes of the ion guiding device; Including, using the processor to generate a pseudopotential to trap the received two or more precursor ions having m / z values ​​below a threshold m / z in the ion guide device, thereby causing the trapped two or more precursor ions to be charge reduced by the received charge-reducing reagent such that the m / z values ​​of the two or more precursor ions increase to a single m / z value above the threshold m / z; a DC voltage applied by the ion guide device to the one or more electrodes is set based on a DC voltage applied to an electrode of the mass filter device, thereby causing, using the processor, the two or more precursor ions having m / z values ​​increased up to the single m / z value to be transmitted successively into the mass filter device.

15. A computer program product comprising a non-transient tangible computer-readable storage medium, the contents of which include a program having instructions for execution on a processor to implement a method for reducing charge of precursor ions of the same compound having different mass-to-charge ratio (m / z) values ​​in order to successively store and transmit precursor ions at a single m / z value; The method comprises: providing a system comprising one or more distinct software modules, the distinct software modules comprising a control module; using the control module to instruct an ion source device to ionize a compound of a sample and generate two or more precursor ions of the compound having different m / z values; commanding a reagent source device to supply a charge-reducing reagent using the control module; using the control module to instruct an ion guide device positioned between a mass filter device and both the ion source device and the reagent source device to receive the two or more precursor ions from the ion source device and the charge reduced reagent from the reagent source device; instructing the ion guiding device to apply alternating current (AC) and direct current (DC) voltages to one or more electrodes of the ion guiding device; Including, using the control module to generate a pseudopotential to trap the received two or more precursor ions having m / z values ​​below a threshold m / z in the ion guide device, thereby causing the trapped two or more precursor ions to be charge reduced by the received charge-reducing reagent such that the m / z values ​​of the two or more precursor ions increase to a single m / z value above the threshold m / z; a control module for controlling a mass filter device that receives an m / z value from a first precursor ion having an m / z value greater than or equal to the m / z value of the first precursor ion and a second precursor ion having an m / z value greater than or equal to the m / z value of the second precursor ion.

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