Improvements in and relating to ion analysis

Abstract

To process data determined from image charge / current signals representing multiple ions of a given charge state (Q), each undergoing vibrational motion at respective oscillation frequencies (f) within an ion analysis apparatus.SOLUTION: A data set includes a measured signal frequency (f0) common to a plurality of measured image charge / current signals, and a plurality of estimated ion charge values corresponding to the respective amplitudes of the measured image charge / current signals. Using an integer charge value ([Qi]) corresponding to one of the estimated ion charge values rounded to the nearest integer, a plurality of different image charge / current signal frequency candidate values (fiCand) is calculated. The plurality of calculated image charge / current signal frequency candidate values (fiCand) is compared with the plurality of different signal frequencies (f) of the measured image charge / current signals to measure a score value representing the similarity between them on the basis of the comparison.SELECTED DRAWING: Figure 2b

Description

Technical Field

[0001] The present invention relates to a method and apparatus for ion analysis using image charge / current analysis and an ion analyzer therefor. In particular, the present invention relates to, but is not limited to, the analysis of image charge / current signals for identifying the charge of ions. For example, the image charge / current signal can be generated by an ion mobility analyzer, a charge detection mass spectrometer (CDMS), or an ion trap device such as an ion cyclotron, Orbitrap (registered trademark), electrostatic linear ion trap (ELIT), quadrupole ion trap, orbital frequency analyzer (OFA), planar electrostatic ion trap (PEIT), or other ion analyzer for generating vibrational motion inside.

Background Art

[0002] Generally, an ion trap mass spectrometer functions to capture ions and vibrate the captured ions, for example, back and forth along a linear orbit or on a circular orbit. An ion trap mass spectrometer can generate a magnetic field, an electromagnetic field, an electrostatic field, or a combination of these fields to capture ions. When an electrostatic field is used to capture ions, the ion trap mass spectrometer is typically called an "electrostatic" ion trap mass spectrometer.

[0003] Generally, the frequency of the oscillation of the trapped ions in an ion trap mass spectrometer depends on the mass-to-charge ratio (m / z) of the ions. This is because ions with a large m / z ratio generally require a longer time to oscillate compared to ions with a small m / z ratio. Using an image charge / current detector, an image charge / current signal representing the oscillating trapped ions can be nondestructively obtained in the time domain. This image charge / current signal can be converted to the frequency domain, for example, by Fourier transform (FT). Since the frequency of the oscillation of the trapped ions depends on m / z, the image charge / current signal in the frequency domain can be regarded as mass spectral data providing information on the m / z distribution of the trapped ions.

[0004] In mass spectrometry, one or more ions undergoing oscillatory motion within an ion analyzer (e.g., an ion trap) induce an image charge / current signal detectable by a sensor electrode of a device configured for the detection of the image charge / current signal. One well-established method for analyzing such an image charge / current signal is to convert this time-domain signal into the frequency domain. The most widely used conversion for this purpose is the Fourier transform (FT). The Fourier transform decomposes the time-domain signal into sine-wave components each having a specific frequency (or period), amplitude, and phase. These parameters are related to the frequency (or period), amplitude, and phase of the periodic components (frequency components) present in the measured image charge / current signal. The frequency (or period) of those periodic components can be readily associated with the m / z value or mass if the charge state of each ion species is known. In ordinary mass spectrometry (MS), it is typical for a large number of ions to be injected into the ion analyzer simultaneously. After a while, those ions become isolated, compact ion packets (clouds) in space. Each cloud corresponds to the same (or very nearly the same) value of mass-to-charge ratio (m / z). By utilizing the position of each signal peak in the frequency domain and the frequency difference between adjacent peaks corresponding to different charge states of a given molecular ion species, it is possible to attempt to regain the charge of the ions in each ion cloud. However, to do so, it must be assumed that all the ions in one cloud have the same charge. This assumption is problematic. This is because it is not necessarily correct to assign one charge to one given frequency peak amplitude if the composition of the ion cloud, e.g., the number of ions it contains and how many ions have been lost from the cloud during the oscillation, is unknown. Generally, the assumption that all the ions in one cloud have the same charge is incorrect. This is because there may be other ions in the cloud having the same (or very nearly the same) m / z value (e.g., a larger mass M and a higher charge Z). This situation is typical for actual experiments in which numerous species are mixed in the sample.Furthermore, when the ion mass becomes very large (e.g., about 1 MDa or more), it may become difficult to distinguish the peaks of the m / z charge state signals with existing analytical methods, and sometimes it becomes impossible to distinguish them at all. In addition, especially when each ion is polyvalent, the space charge in the ion cloud worsens the situation. This space charge rapidly blurs (diffuses) the ion cloud in space, and the quality of the spectrum of the signal from the ion analyzer deteriorates. It may be found that it is difficult to accurately measure the information on the true charge state of the ion due to the influence of noise (such as instrument noise) in the measured image charge / current signal. As a result, the measurement accuracy of the mass value of each ion species decreases.

[0005] The present invention has been made in view of the above matters.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Non-Patent Documents

[0007]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Means for Solving the Problems

[0008] An image charge / current signal can be obtained in a mass spectrometer that utilizes non-destructive detection of a signal including a periodic component corresponding to the vibration of some ion species captured. However, the present invention can be applied to ion analysis in any other field where it is necessary to analyze a signal including a periodic component. The frequency of ion motion depends on the mass-to-charge (m / z) ratio of the ion, and when there are multiple packets of ions in an ion analyzer (for example, an ion trap), due to the convergence characteristics of the ion analyzer, the motion of each packet of ions having the same m / z ratio may be synchronized.

[0009] The detection of ions using image charges is based on the principles derived by Shockley (Non-Patent Document 1) and Ramo (Non-Patent Document 2). Here, it has been shown that a measurable current is induced in the electrode by the image (mirror image) of a charge moving past the vicinity of an electrode of finite size. The image charge q induced on the electrode of the detection device by a charge Q moving in free space with a velocity vector v(r) depends only on the position r and velocity of the moving charge, and the configuration of the electrode of the detection device. The image charge q does not depend on the bias voltage applied to the electrode nor on the space charge present, and is given by the following equation.

Equation

[0010] Here, V(r) is the electrostatic potential at the position of the charge given by the vector r in the detection device in a situation where the selected electrode is at unit potential and all other electrodes are at zero potential when the charge Q is not present. The induced image charge / current I is given as follows by the rate of change of this quantity.

Equation

[0011] Here, E(r) is an electric field (vector) known as the "weight field". As a simple and specific example of how to implement this relationship, consider a detection device equipped with a pair of parallel planar electrode plates spaced at a uniform interval d. Suppose an ion with charge Q moves along a circular orbit in a plane perpendicular to the surfaces of the two electrode plates at a speed v0 between the electrode plates. The "weight field" is uniform, perpendicular to the electrode plates, and directed parallel to the ion orbit (practically speaking, if the dimensions of the plates are much larger than their spacing and as a result the fringe effect can be ignored, this is substantially true). Therefore, [Number] it is. As a result, the induced image charge / current becomes a sinusoidal vibration signal of the following form. [Number]

[0012] The amplitude of the induced image charge / current is proportional to the charge Q of the ion. Once the proportionality constant term v0 / d is taken into account, the charge of the ion can be determined by measuring this amplitude. More generally, the principle also applies to more complex electrode structures of detection devices in that the amplitude of the induced image charge / current is proportional to the charge Q of the ion, and the proportionality constant term varies depending on the electrode structure of the detection device.

[0013] The present invention relates to the analysis of image charge / current signals. For example, in the image charge / current analysis method, it is necessary to measure the signal charge ratio (m / z) and the charge (Q) of the ion in order to be able to estimate the mass of the ion through the following relationship. [Number] The frequency of the vibrational motion of ions can be specified very precisely, but the accuracy with which the ion charge Q can be estimated by direct measurement of the image charge / current signal is very much reduced by the electronic noise within the ion analyzer.

[0014] The inventors have realized a process for more accurately measuring the charge of an ion based on a procedure of rounding the measured (estimated) charge value to an integer and assigning a score to the rounded charge value, using a score calculated based on the presence or absence of the contribution of the image charge / current signal from the said ion to a data set of other ions, to assign a score to the proposed charge value. If the proposed charge value achieves a sufficiently high score, it can be used in place of the measured (estimated) charge value. As a result, the number of misassignments of ion charge values can be reduced. If the ion charge is correctly assigned, the resulting mass spectrum will be better. It may be possible to obtain a more accurate mass spectrum while using the output of an image charge / current system with low charge measurement accuracy. In prior art systems, charge measurement accuracy is typically improved by using complex and expensive optimized components in the image charge / current system and cooling the detection circuitry to cryogenic temperatures. The present invention provides a method of achieving an improvement in measured charge accuracy without relying on complex and expensive electronics and / or cryogenic temperatures.

[0015] In a first aspect, the present invention is a method of processing data determined from an image charge / current signal representing a plurality of ions of a given charge state (Q) each undergoing vibrational motion at a respective vibrational frequency (f) within an ion analyzer, A measured signal frequency (f) common to a plurality of measured image charge / current signals 0 and a data set including a plurality of estimated ion charge values corresponding to the amplitudes of each of the plurality of measured image charge / current signals are obtained, generating an integer charge value ([Q]) corresponding to rounding one of the said estimated ion charge values to the nearest integer value, and, (a) said integer charge value ([Q i) is selected and used to calculate a plurality of different image charge / current signal frequency candidate values (f i Cand ) according to the selected measured signal frequency (f0), and according to ions (e.g., proton addition (n), adduct ions (l)), and / or one or more corresponding ones of a plurality of different charge state candidates of isotopes or isotopic molecular species of the ions, and then (b) comparing the calculated plurality of image charge / current signal frequency candidate values (f i Cand ) with a plurality of different signal frequencies (f) of the measured image charge / current signal, and calculating a score value representing the similarity between them based on the comparison, if the score value matches or exceeds the score threshold, determining that the charge state (Q) of the ion undergoing oscillatory motion of the selected measured signal frequency (f0) is equal to the integer charge value ([Q i ^]), to provide a method including.

[0016] For example, the image charge / current signal can be generated by an ion mobility analyzer, a charge detection mass spectrometer (CDMS), or an ion cyclotron, Orbitrap (registered trademark), electrostatic linear ion trap (ELIT), quadrupole ion trap, orbital frequency analyzer (OFA), planar electrostatic ion trap (PEIT), or other ion trap devices such as other ion analyzers for generating oscillatory motion inside.

[0017] Preferably, the step of generating the integer charge value ([Q]) includes generating a plurality of integer charge values ([Q]) corresponding to rounding the estimated ion charge values to the nearest integer values respectively, and (c) repeating steps (a) and (b) for each of the generated integer charge values ([Q]) among the generated integer charge values ([Q i ), and (d) Identifying the integer charge value ([Q i ^]) that achieves the highest said score value including, where the score threshold corresponds to the highest said score value, and the charge state (Q) of the ion is determined to be equal to the identified integer charge value ([Q i ^]) that achieves the highest said score value.

[0018] Consider an ion with mass M0 undergoing oscillatory motion at frequency f0 within an image charge / current signal type mass spectrometer. in which n protons are bonded to this ion having a charge amount of Q×e by proton addition (Q, n = integers) Assume that these protons add extra mass and charge to the original mass M0 and add a charge (Q + n)e to the ion (where e is the charge of a proton). Thus, the mass-to-charge ratio (m / z) of this complex (i.e., the ion and the protons bound to it) is

Equation

Equation

Equation

Equation

Equation

[0019] Therefore, preferably, the calculation of a plurality of different image charge / current signal frequency candidate values (f i Cand ) is performed with the integer n selected to quantify the number of proton-added protons bound to the ions, the mass of the proton m p (assuming this is equal to the mass of the neutron), the charge of the proton e, and a preset calibration constant α, as [Number] Perform it so as to satisfy the condition. The value of n can be selected to be any integer value as required, and different values of n can be selected in a desired number, and the corresponding number of different frequency candidate values f i Cand can be generated by this formula. In other words, [Q i +n represents a given proton addition state state and can represent different proton addition states with different values of n. Therefore, for a given value [Q i , the number difference of proton-added protons between two different proton addition states can be determined with the integer n.

[0020] Preferably, as a generalization of this, the calculation of a plurality of different image charge / current signal frequency candidate values (f i Cand ) is performed by setting the integer selected to quantify the number of proton-added protons bonded to the ion as n, the integer selected to quantify the number difference of neutrons in the nucleus between different isotopes or isotopomer species of the ion as k, the mass of the proton as m p (assuming this is equal to the mass of the neutron), the charge of the proton as e, and the preset calibration constant as α,

Equation

[0021] In the present application, the term "isotope" can be understood to include a reference to any one of two or more forms of an element in which the number of protons in the nucleus of those atoms is the same but the number of neutrons is different. As a result, atoms of the same isotope have the same atomic number but different mass numbers (atomic weights). Further, in the present application, the term "isotope molecular species" can be understood to include a reference to any one of two or more forms of a compound that differ only in their isotope composition (e.g., water and heavy water).

[0022] Desirably, as a further generalization, the calculation of a plurality of different image charge / current signal frequency candidate values (f i Cand ) is performed so as to satisfy the condition that, taking l as an integer selected to quantify the number of additional ions of mass m bonded to the ion, X The values of n, k, and l can be selected to be any integer values as needed, and different values of n, k, and l can be selected in a desired number, and the corresponding number of different frequency candidate values f [Number] can be generated by this formula. To avoid misunderstanding, [Q i Cand +n represents a given proton addition state i and different values of n can represent different proton addition states. Therefore, for a given value of [Q state , the difference in the number of proton-added protons between two different proton addition states can be determined by the integer n. i

[0023] The step of obtaining the dataset can include selecting a measured signal frequency (f0) common to the plurality of measured image charge / current signals, and calculating the plurality of estimated ion charge values based on the measured amplitude of each of the plurality of measured image charge / current signals.

[0024] The similarity may include the sum of the number of calculated image charge / current signal frequency candidates (f i Cand ) whose difference from any signal frequency among the plurality of measured image charge / current signals is less than a predetermined difference threshold. Among the plurality of measured image charge / current signals, the similarity between the candidate frequency (f i Cand ) and the measured frequency (f j ) may include the sum of the number of signal frequency candidates (f j , j = 0, 1, …, N - 1) whose difference from any signal frequency is less than a predetermined difference threshold (ε). For example, the similarity may simply be the count of the number of candidate frequencies that satisfy the condition of i Cand . The predetermined difference threshold (ε) may be set by the user. The predetermined difference threshold (ε) can be set to be approximately equal to the uncertainty range or standard deviation / variance determined in advance or measured in advance in the measured values (f i Cand , j = 0, 1, …, N - 1) of the image charge / current signal frequency components. This method may include determining the integer charge value ([Q

Number

Number

[0025] Calculation of a plurality of different image charge / current signal frequency candidate values (f i Cand ) can include selecting a plurality of different candidate states of the isotope or isotopic molecular species (k) of the ion, each sharing a common fixed candidate state of the ion-proton addition (n).

[0026] Calculation of a plurality of different image charge / current signal frequency candidate values (f i Cand ) can include selecting a plurality of different charge state candidates of the ion (such as ion-proton addition (n) or additional ion (l)), each sharing a common fixed candidate state of the isotope or isotopic molecular species (k) of the ion.

[0027] Calculation of a plurality of different image charge / current signal frequency candidate values (f i Cand ) can include selecting different charge state candidates of the ion (such as proton addition (n), additional ion (l)) and selecting different candidate states of the isotope or isotopic molecular species (k) of the ion.

[0028] This method can include determining the mass value (M) of the ion oscillating at the selected measured signal frequency (f0) according to the identified integer charge value ([Q i ^]) that achieves the highest said score value, and

Number

[0029] It should be understood that each of the methods described above can be carried out in an apparatus configured to carry out these methods. For example, the apparatus can be provided with a processor or a computer. Each method may be carried out by the apparatus by applying the method to data generated by a separate ion analyzer and subsequently acquired (i.e., not “live” data simultaneous with the generation of the data). Alternatively, or in addition, each method can be carried out by an apparatus comprising an ion analyzer provided with such a processor or computer.

[0030] In a second aspect, the invention is an apparatus configured to process data determined from an image charge / current signal representing a plurality of ions of a given charge state (Q) undergoing oscillatory motion at respective oscillation frequencies (f) within an ion analyzer, acquiring a data set comprising a measured signal frequency (f0) common to a plurality of measured image charge / current signals and a plurality of estimated ion charge values corresponding to the respective amplitudes of the plurality of measured image charge / current signals, generating an integer charge value ([Q]) corresponding to rounding one of the estimated ion charge values to the nearest integer value, (a) selecting the integer charge value ([Q i ) and using it to calculate a plurality of different image charge / current signal frequency candidate values (f i Cand ) according to the selected measured signal frequency (f0) and in accordance with one or more different charge state candidates of one or more of the ions (e.g., proton addition (n), adduct ion (l)), and / or isotopes or isotopologue species (k) of the ion, and (b) comparing the calculated plurality of image charge / current signal frequency candidate values (f i Cand ) with the plurality of different signal frequencies (f) of the measured image charge / current signals and calculating a score value representing the degree of similarity therebetween based on the comparison, If the score value matches or exceeds the score threshold, the charge state (Q) of the ion that is undergoing oscillatory motion at the selected measured signal frequency (f0) is determined to be equal to the identified integer charge value ([Q i ^]). The apparatus can include a processor module configured as described above.

[0031] Preferably, the processor module generates an integer charge value [Q] by generating a plurality of integer charge values ([Q]) corresponding to rounding the estimated ion charge values to the nearest integer values respectively, (e) repeating steps (a) and (b) for each of the generated integer charge values ([Q]) among the generated integer charge values ([Q i ), and (f) identifying the integer charge value ([Q i ^]) that achieves the highest score value, wherein the score threshold corresponds to the highest score value, and the charge state (Q) of the ion is determined to be equal to the identified integer charge value ([Q i ^]) that achieves the highest score value.

[0032] Desirably, the processor module selects an integer n for quantifying the number of proton - added protons bound to the ion, the mass of a proton m p (which is assumed to be equal to the mass of a neutron), the charge of a proton e, and a preset calibration constant α,

Number

[0033] Desirably, as a generalization of the above conditions, the processor module selects an integer n for quantifying the number of proton-added protons bound to an ion, an integer k for quantifying the difference in the number of protons in the nucleus between different isotopes or isotopic molecular species of the ion, and the mass of a proton as m p (assuming the mass of a neutron), the charge of a proton as e, and a preset calibration constant as α, [Number] such that the plurality of different image charge / current signal frequency candidate values (f i Cand ) are calculated. The values of n and k can be selected to be any integer values as needed, and different values of n and k are selected in a desired number, and the corresponding number of different frequency candidate values f i Cand can be generated by this formula.

[0034] Desirably, as a further generalization of the above conditions, the processor module selects an integer l for quantifying the number of additional ions with mass m X bound to the ion, [Number] such that the plurality of different image charge / current signal frequency candidate values (f i Cand ) are calculated. The values of n, k, and l can be selected to be any integer values as needed, and different values of n, k, and l are selected in a desired number, and the corresponding number of different frequency candidate values f i Cand can be generated by this formula.

[0035] The processor module can be configured to obtain the data set by selecting a measured signal frequency (f0) common to the plurality of measured image charge / current signals and calculating the plurality of estimated ion charge values based on the measured amplitude of each of the plurality of measured image charge / current signals.

[0036] The processor module calculates the similarity as the sum of the number of calculated image charge / current signal frequency candidate values (f i Cand ) whose difference from any signal frequency among the plurality of measured image charge / current signals is less than a predetermined difference threshold. Among the plurality of measured image charge / current signals, the similarity between the candidate frequency (f i Cand ) and the measured frequency (f j ) can be the sum of the number of signal frequency candidate values (f j , j = 0, 1, …, N−1) whose difference from any signal frequency (f i Cand ) is less than a predetermined difference threshold (ε). For example, the similarity can be simply the count of the number of candidate frequencies that satisfy the i Cand condition. The predetermined difference threshold (ε) may be set by the user. The predetermined difference threshold (ε) can be set to be approximately equal to the uncertainty range or standard deviation / variance determined in advance or measured in advance in the measured values (f

Number

Number

[0037] The processor module calculates the similarity such that it includes the total number of calculated image charge / current signal frequency candidate values (f i Cand ) whose difference from any signal frequency among the plurality of measured image charges / current signals is less than a predetermined difference threshold.

[0038] Desirably, the processor module calculates the plurality of different image charge / current signal frequency candidate values (f i Cand ) through a process that includes selecting a plurality of different candidate states of the isotope or isotopic molecular species (k) of the ion, each sharing a common fixed candidate state of ion proton addition (n).

[0039] Preferably, the processor module calculates the plurality of different image charge / current signal frequency candidate values (f i Cand ) through a process that includes selecting a plurality of different charge state candidates of the ion (such as ion proton addition (n) or added ion (l)), each sharing a common fixed candidate state of the isotope or isotopic molecular species (k) of the ion.

[0040] Preferably, the processor module calculates the plurality of different image charge / current signal frequency candidate values (f i Cand ) by a process that includes selecting different charge state candidates of ions (e.g., proton addition (n), adduct ion (l)) and selecting different candidate states of isotopes or isotope molecular species (k) of the ions.

[0041] In a third aspect, the present invention can provide an ion analyzer including the above-described apparatus.

[0042] In a fourth aspect, the present invention can provide a computer program or a computer program product adapted to execute the above-described method.

[0043] In a fifth aspect, the present invention can provide a computer-readable storage medium or a data carrier including the above-described computer program or computer program product.

[0044] The described aspects and combinations of preferred features are included in the present invention unless such combinations are clearly unacceptable or explicitly avoided.

Brief Description of the Drawings

[0045] The principles of the present invention will be discussed below with reference to the accompanying drawings for embodiments and experiments that illustrate the principles.

[0046]

Figure 1

Figure 2a

Figure 2b

Figure 3

Figure 4

Figure 5a

Figure 5

Figure 6

Figure 7

Best Mode for Carrying Out the Invention

[0047] Aspects and embodiments of the present invention will be discussed below with reference to the accompanying drawings. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this document are incorporated herein by reference.

[0048] In the drawings, for the sake of consistency, the same reference numerals are assigned to the same elements. In the following example, the image charge / current signal is generated by a real or simulated charge detection mass spectrometer (CDMS) and is referred to as a CDMS image charge / current signal. However, it should be understood that instead, an ion mobility analyzer, or an ion cyclotron, Orbitrap (registered trademark), electrostatic linear ion trap (ELIT), quadrupole ion trap, orbital frequency analyzer (OFA), planar electrostatic ion trap (PEIT), or other ion trap device such as another ion analyzer for generating internal vibrational motion, may be used to generate the image charge / current signal.

[0049] FIG. 1(a) schematically shows a CDMS ion analyzer in the form of an electrostatic ion trap 1 for mass spectrometry. This electrostatic ion trap includes ion analysis chambers (2, 3, 4, 5), which are configured to receive one or more ions 6A and generate an image charge / current signal in response to the vibrational motion 7 of the received ions 6B when they are within the ion analysis chamber. The ion analysis chamber comprises a first electrode array 2 and a second electrode array 3 spaced from the first electrode array by a substantially constant separation distance.

[0050] A voltage supply unit (not shown) is arranged to supply a voltage to each electrode of the first and second electrode arrays during use to form an electrostatic field in the space between the electrode arrays. The electrodes of the first array and the electrodes of the second array are supplied with voltages of substantially the same pattern from the voltage supply unit, whereby the potential distribution in the space between the first and second electrode arrays (2, 3) is such that ions 6B are reflected in the flight direction 7 and caused to perform a periodic oscillatory motion in the space. The electrostatic ion trap 1 can be configured as described, for example, in Patent Document 1 (Ding et al.), the entire disclosure of which is incorporated herein by reference. Other arrangements are possible and will be readily apparent to those skilled in the art.

[0051] The periodic oscillatory motion of ions 6B in the space between the first and second electrode arrays can be converged, for example, approximately in the middle between the first and second electrode arrays, as described in Patent Document 1 (Ding et al.), by applying appropriate voltages to the first and second electrode arrays. Other arrangements are possible and will be readily apparent to those skilled in the art.

[0052] One or more electrodes of each of the first and second electrode arrays are configured as image charge / current sensor electrodes 8 and are connected as such to a signal recording unit 10. This unit is configured to receive an image charge / current signal 9 from the sensor electrodes and record the received image charge / current signal in the time domain. The signal recording unit 10 can be provided with an amplification circuit system as required for detecting an image charge / current having a periodic component / frequency component related to the mass-to-charge ratio of the ions 6B performing the periodic oscillatory motion 7 in the space between the first and second electrode arrays (2, 3).

[0053] The first and second electrode arrays are, for example, as described in Patent Document 1 (Ding et al.), (a) parallel strip electrodes, and / or, (b) concentric, circular, or partially circular conductive rings It can be made to have a planar array formed thereby. Other arrangements are also possible, which will be readily understood by those skilled in the art. Each of the first and second electrode arrays extends in the direction of the periodic oscillatory motion 7 of the ions 6B. The ion analysis chamber includes a main part defined by the first and second electrode arrays and the space therebetween, as well as two end electrodes (4, 5). A voltage difference applied between the main segment and each end segment forms a potential barrier for reflecting the ions 6B in the direction of the oscillatory motion 7, thereby trapping the ions within the space between the first and second electrode arrays. The electrostatic ion trap can include an ion source (not shown. For example, an ion trap) configured to temporarily accumulate the ions 6A outside the ion analysis chamber and then inject the accumulated ions 1A into the space between the first and second electrode arrays through an ion injection opening formed in one 4 of the two end electrodes (4, 5). For example, the ion source can include a pulsar (not shown) for injecting ions into the space between the first and second electrode arrays, as described in Patent Document 1 (Ding et al.). Other arrangements are also possible, which will be readily understood by those skilled in the art.

[0054] The ion analyzer 1 further includes a signal processing unit 12 configured to receive the recorded image charge / current signal 11 from the signal recording unit 10, process the recorded signal to determine the amplitude or magnitude of the time-domain signal, and use it to calculate the charge of the ions oscillating within the ion analysis device. The signal processing unit 12 also determines the frequency of the oscillatory motion of the ions within the ion analysis device.

[0055] The amplitude value in the time domain representing the charge of the target ion can be, for example, an amplitude value derived using the above-described "weight field" converted from a pre-calibrated proportional relationship between the amplitude value and the corresponding ion charge Q. These signal processing steps are executed by the signal processing unit 12, which will be described in more detail later. The signal processing unit 12 comprises a processor or computer programmed to execute computer program instructions for performing the above signal processing steps on an image charge / current signal representing a trapped ion undergoing oscillatory motion. The result is a value representing the charge of the ion and / or a mass value representing the mass of the ion. The ion analyzer 1 further includes a storage unit and / or a display unit 14 configured to receive data 13 corresponding to the charge of the ion and to indicate the measured charge value and / or mass value to the user and / or store the value in the storage unit.

[0056] As shown in FIG. 1(c), the image charge / current signal 9 contains a number of simultaneous oscillatory signals in the time domain. Each of the simultaneous oscillatory signals in this image charge / current signal 9 contains a single oscillatory signal as schematically shown in FIG. 1(b), which signal exists for only a finite "lifetime" (LT) with a substantially constant signal amplitude and a substantially constant signal frequency (f). When the apparatus 1 is in use, it is typical for there to be a number of ions of different masses and charge states inside it, and since they are all simultaneously undergoing their own oscillatory motion, the image charge / current signal 9 contains a number of simultaneous individual oscillatory signals, each signal having the shape shown in FIG. 1(b) and each having a different signal amplitude and signal frequency.

[0057] The signal processing unit 12 is configured to generate an estimated value of the charge state (Q) of each ion undergoing oscillatory motion at each oscillation frequency (f) within the ion analyzer by processing the image charge / current signal (FIG. 1(c)). For example, the induced image charge / current signal is

Number

[0058] The signal processing unit 12 is configured to acquire a data set (20 in Fig. 2(a)) including the measured signal frequency (f0 = 170.661 kHz) common to a plurality of measured CDMS image charge / current signals (Fig. 1(a)) and a plurality of estimated ion charge values Q respectively corresponding to the amplitudes of each of the plurality of measured CDMS image charge / current signals. This acquisition can be achieved by applying known CDMS image charge / current signal processing techniques that are easily available to those skilled in the art to the overall spectrum, and obtaining the amplitude QA and the frequency f0 = ω / 2π from the relevant frequency components of the overall signal.

[0059] The signal processing unit 12 is configured to generate an integer charge value ([Q]) corresponding to rounding the estimated ion charge value Q to the nearest integer value. Specifically, each of the plurality of distinct estimated charge values of the set 20 of estimated charges associated with the measured signal frequency (f0 = 170.661 kHz) has a non-integer value derived from the non-integer amplitude value QA of the induced image charge / current signal (where A is a non-integer calibration constant). Since it is known that the true value of the charge of an ion must be an integer multiple of the unit charge e of an electron (or proton), it may be assumed that the true charge state of the ion is one of the following integers.

Number

[0060]

Table 1

[0061] In this way, the set of 10 estimated (measured) ion charge state values is reduced to three possible integer candidate values: [Q] = 48, [Q] = 49, and [Q] = 50. These correspond to three values of the incremental integer n: n = 0, ±1. In other examples, there may be only one corresponding value of the incremental integer n at the end of this rounding process. Of course, whether this is the case and how many different values of the incremental integer are actually used depend on the spread of the values of the estimated (measured) ion charge value Q. The value of the incremental integer n may be set by the user or may be pre-set within the signal processing unit 12. For example, if the true charge state of the ion is [Q] TRUE = 50, then if n = -2, -1, 0 are selected, the same rounded charge value is achieved. Of course, what should be specified is the true charge state of the ion, and the signal processing unit 12 is configured to better predict its true value through an elimination process that includes selecting one or more rounded charge values ([Q i ) from among the rounded charge values it generates, and determining whether the selection meets a predetermined criterion indicating that it actually improves the estimated (measured) value of the ion charge state.

[0062] For this purpose, the signal processing unit 12 then selects one integer charge value ([Q i) is selected and used to calculate a plurality of different CDMS image charge / current signal frequency candidate values (f i Cand ) according to the selected measured signal frequency (f0) and according to the corresponding one of one or more different candidate states of ion proton addition (n). In other words, it is assumed that different values of the increment integer n correspond to different amounts of proton addition to the ion (i.e., different numbers of protons bound to the ion). The difference in the number of protons that may be bound to the ion not only has the effect of changing the charge state of the proton-added ion (an integer multiple of the proton charge), but also has the effect of changing the mass of the proton-added ion (according to the mass of the proton). The processor module uses n as the integer selected to quantify the number of proton-added protons bound to the ion, m p as the mass of the proton, e as the charge of the proton, and α as the preset calibration constant,

Equation

Equation

Number

[0063] Therefore, the signal processing unit 12 calculates a plurality of different CDMS image charge / current signal frequency candidate values (f i Cand) is compared with a plurality of different signal frequencies (f) of the measured CDMS image charge / current signal, and a score value representing the similarity between the two is calculated based on the comparison. If the score value matches or exceeds the score threshold, the signal processing unit 12 determines that the true charge state (Q) of the ions vibrating at the selected measured signal frequency (f0 = 170.661 kHz0) is equal to the identified integer charge value ([Q i ^]). The score threshold can be a preset score value determined by the user. For example, the signal processing unit 12 sequentially selects one integer charge value ([Q i ) and performs the above calculation to determine whether the one integer charge value results in a score value that matches or exceeds the score threshold. If not, it proceeds to select an alternative integer charge value ([Q i ) and repeat the process. This process can be repeated until a preset number of different alternative integer charge values ([Q i ) are selected and considered as above, or until a selected alternative integer charge value ([Q i ) achieves a score value that matches or exceeds the score threshold (e.g., until it first appears).

[0064] Alternatively, the signal processing unit 12 may select a plurality of alternative integer charge values ([Q i ) and generate a corresponding plurality of score thresholds, one for each selected integer charge value ([Q i ). The signal processing unit 12 may dynamically set the threshold such that the score value of the highest score among the corresponding plurality of score values becomes the score threshold. In this way, the highest score value will always be accepted as matching the score threshold. For example, the processor module generates a plurality of integer charge values ([Q]) by rounding each estimated ion charge value to the nearest integer value, and for each individual integer charge value ([Q i ) among the generated integer charge values ([Q]), ·Select one integer charge value ([Q i ), and use it to calculate a plurality of different CDMS image charge / current signal frequency candidate values (f i Cand ) according to the selected measured signal frequency (f0) and according to the corresponding one of one or more different candidate states of ion proton addition (n), and then, ·Compare the calculated plurality of different CDMS image charge / current signal frequency candidate values (f i Cand ) with a plurality of different signal frequencies (f) of the measured CDMS image charge / current signal, and calculate a score value representing the similarity between the two based on the comparison. It can be configured to repeat the steps described above. The processor module can then be configured to identify the integer charge value ([Q i ^]) that achieves the highest said score value. Here, the score threshold corresponds to the highest score value, and the charge state (Q) of the ion is determined to be equal to the identified integer charge value ([Q i ^]) that achieves the highest score value.

[0065] In some embodiments of the present invention, the processor module

Number

[0066] In some embodiments of the present invention, the processor module is configured to

Equation

[0067] Thus, the processor module is considered the reason for the change in the number and position of spectral (frequency) components in the measured CDMS image charge / current signal due to different masses and different charges binding or adding to the ions · Protons bound to the ions (proton addition), · Change in the mass of the ions due to isotopes, and · Additional ions bound to the ions (e.g., Na + ) Considering, the plurality of different CDMS image charge / current signal frequency candidate values (f i Cand ) can be calculated.

[0068] By selecting the measured signal frequency (f0) common to the plurality of measured CDMS image charge / current signals and calculating the corresponding plurality of estimated ion charge values Q based on the measured amplitude of each of the plurality of measured CDMS image charge / current signals, the signal processing unit 12 can provide raw data including data pairs (f, Q) of the signal frequency values of the CDMS image charge / current signal components and the associated estimated / measured charge values. For example, as shown in FIG. 2a, nine separate signal frequency values (f = f0, f1, …, f8) appear as distinct CDMS image charge / current signal components, each having its own cluster of different estimated / measured ion charge values Q (e.g., the signal frequency value f0 has data cluster 20). The process of comparing the calculated plurality of different CDMS image charge / current signal frequency candidate values (f i Cand ) with the plurality of different signal frequencies (f) of the measured CDMS image charge / current signal is the difference value Δ of the difference between a given frequency candidate value and each of the N distinct frequencies of the signal components in the CDMS image charge / current signal (e.g., N = 9 in FIG. 2a) i,jCand may include calculating. That is,

Number

Number

Number

Number

Number

[0069] ​The score value may be calculated by applying some weighting to the frequency difference. For example,

Number

Number

[0070] As described above, the processor module selects a plurality of different candidate states of the isotope or isotopic molecular species of the ion by selecting a plurality of different values for an additional integer k, and / or selects a plurality of different candidate states of the ion proton addition by selecting a plurality of different values for an integer n, and / or selects a plurality of different candidate states of the adduct ion by selecting a plurality of different values for yet another integer l, by a process including a plurality of different CDMS image charge / current signal frequency candidate values (f i Cand) can be configured to calculate. Each of these different frequency values may correspond to a certain common fixed candidate state (i.e., the same fixed value of n, k, or l) of ion proton addition, or isotope or isotopic molecular species, or adduct ion, or some but not all of them may correspond to a certain common candidate state (i.e., the same value of n, k, or l) of ion proton addition, or isotope or isotopic molecular species, or adduct ion, or some or all of them may correspond to different candidate states (i.e., different values of n, k, or l) of ion proton addition, or isotope or isotopic molecular species, or adduct ion.

[0071] For example, the processor module may calculate the plurality of different CDMS image charge / current signal frequency candidate values (f i Cand ) through a process that includes selecting a plurality of different candidate states of ion proton addition (n) and / or adduct ion (l) that each share a common fixed candidate state of the isotope or isotopic molecular species (k) of the ion. i Cand ) can be configured to calculate. Other combinations and variations of the integers n, k, or l can also be considered according to the user's desire.

[0072] Once the integer charge value ([Q i ^]) that achieves the highest score value is identified by the scoring process, the processor module uses that identified integer charge value ([Q i ^]) to

Number

[0073] FIG. 2b is a flowchart of the procedure of a process for determining the integer charge value for ions vibrating at a given frequency, selected from different signal frequency values and a plurality of different estimated charge values [Q] corresponding thereto in FIG. 2a. This method can be applied to the processing of a data set of data determined from an image charge / current signal representing a plurality of ions in a given charge state (Q) vibrating at each vibration frequency (f) within an ion analyzer. This method includes the following steps in one embodiment of the present invention. Step S1: Obtain a data set. Step S2: Generate a plurality of integer charge values ([Q]) corresponding to rounding each estimated ion charge value to the nearest integer value. Step S3: Select one integer charge value ([Q i ) and use it to calculate a plurality of different CDMS image charge / current signal frequency candidate values (f i Cand ) according to the selected measured signal frequency (f0), and in accordance with one or a plurality of different charge state candidates of ions (for example, proton addition (n) and / or added ions (l)), and / or isotopes or isotope molecular species (k) of the ions. Step S4: Compare the calculated plurality of different CDMS image charge / current signal frequency candidate values (f i Cand ) with a plurality of different signal frequencies (f) of the measured CDMS image charge / current signal. Step S5: Calculate a score value representing the similarity between the candidate signal frequency and the measured signal frequency based on the comparison in Step S4. Step S5B: For each integer charge value ([Q]) among the generated integer charge values ([Q i ), repeat steps S3, S4, and S5. Step S6: Identify the integer charge value ([Q i ^]) that achieves the highest score value. Step S7: Determine that the charge state (Q) of the ion undergoing oscillatory motion at the selected measured signal frequency (f0) is equal to the integer charge value ([Q i ^]) that achieves the highest score value.

Example

[0074] Example 1 In the CDMS experiment, the amplitudes of all detected frequency components were measured and converted into charge values. By doing so, a dataset of frequency-charge value pairs (f i , Q), that is, a list, was obtained. Then, each measured frequency f i was taken in order from the list as the object of study. Specifically, the measured charge value Q associated with it was processed according to the above-described scoring method. Since the true charge value must be an integer (in units of the electron charge), the measured charge value Q was rounded to the nearest integer. That is, with [Q] being an integer, Q → [Q]. It was assumed that the ion with the oscillation frequency f0 (and the corresponding mass-to-charge ratio (m / z)) might be charged with a charge selected from [Q] - 2, [Q] - 1, [Q], [Q] + 1, [Q] + 2. For example, assume that the mass-to-charge ratio of the ion is (m / z) = 800 Th and the measured charge after rounding to an integer is [Q] = 50 e. This means M = 800 Th × 50 e - 50 m pIt means estimating a mass of 39950 Da. The number of such estimated values may be selected according to the background CDMS image charge / current signal noise level. Note that the background noise level is determined by electronic circuit components and temperature, and furthermore depends on the ion lifetime (LT). The smaller the LT, the higher the noise level, and vice versa. A score for each estimated charge [Q] was calculated, and the charge achieving the highest score was selected. For example, the score was maximum when [Q] - 1 = 49e. If the best estimated charge value is 49e at (m / z) = 800 Th (which remains unchanged), the molecular mass is M = 800 Th × 49e - 49m p is estimated to be 39151 Da. Here, ([Q] - 1)m is subtracted to reach the estimated value of the molecular mass (without proton addition). p This mass is considered to be correct or at least a better estimated value, while 39950 Da is considered incorrect.

[0075] Scores for each of the five different integer charge value candidates of [Q] - 2, [Q] - 1, [Q], [Q] + 1, [Q] + 2 were calculated as follows. Since the measured values of CDMS image charge / current contain simultaneous data for a huge number of ions derived from the analyte, the data corresponds to a large number of different combinations of isotope molecular species (determined by isotope composition and amount of isotopes) and charge states (determined by the shape and structure of the molecule and ionization conditions). This means that we will see molecules with the same molecular type (corresponding to frequency f0) but different charge states and isotope compositions. Therefore, a number of rules to be confirmed are determined. As an example, charge states of ±1 and ±5m p (isotope molecular species), and frequency positions of signal frequency components corresponding to charge states that are 1e larger and ±5m p as their mixture were confirmed. Summarized as follows. (1) Charge state is one proton lower: n = -1 (2) Charge state is one proton higher: n = 1 (3) Mass is 5m p lower (charge state is the same: n = 0): k = -5 (4) Five times higher in mass (same charge state: n = 0): k = 5 p (5) One proton higher in charge state and five times higher in mass: n = 1, k = 5 p (6) One proton higher in charge state and five times lower in mass: n = 1, k = -5 p

[0076] There are six rules in total. When presenting the first candidate integer charge value [Q] = 48e, the estimated molecular mass is

Number

Number

[0077] Next, the integer charge candidate was increased to [Q] = 49e and the above process was repeated. The process was repeated again for each of the five different integer charge value candidates of [Q] - 2, [Q] - 1, [Q], [Q] + 1, and [Q] + 2. When five scores (one for each integer charge candidate) were thus obtained, the score for [Q] = [Q^] = 49e was the maximum. This charge was accepted as a more accurate charge estimate for the ion at the oscillation frequency f0 instead of the initial 50e.

[0078] Then, for the next frequency f in the dataset of frequency and charge value pairs (f i , Q), the above procedure was repeated. That is, at the end of the process, the frequency value taken from the first dataset (f i ) was transformed to (f i , [Q i ^]). Here, the frequency value (and consequently the m / z value) remained unchanged, while the value of Q was improved as Q → [Q i ^]. Then, i ^] and the corresponding mass spectrum was obtained from the frequency spectrum of the data (i.e., the value of f

Number

Equation

Equation

[0079] The 40 kDa protein mass was simulated with a certain range of isotope molecular species that were Gaussian distributed around the most likely mass of 40 kDa, and possible charge states that were similarly Gaussian distributed around the most likely charge of 50e. The standard deviation (SD) of these distributions was 2m p(or 2Da) and 5e. Figures 3(a) and (b) show the range of mass displacement and charge state included in this example. Therefore, the detected (simulated detection) charge has an uncertainty of 1e (which is also a Gaussian distribution, SD = 1e). Figure 4 shows the distribution of the generated charge Q and the distribution of ions with a separated charge state of 50e (corresponding to ions with a vibration frequency centered at 170.67 kHz). Finally, there was a jitter of ±0.1 Hz (uniformly distributed) in the measured frequency. The total number of points in the dataset was 10,000.

[0080] Figures 5a, 5(b), and 5(c) show plots following the histograms below.

[0081] In Figure 5a, the data generated as described above is shown by the upper line read from the left vertical axis. The mass value M is obtained as M = m / z × Q from the measured charge Q and the measured m / z. This mass histogram is very wide due to the low charge measurement accuracy and does not resolve the isotope molecular species. The data generated as described above, with the measured charge Q rounded to the nearest integer value [Q], is shown by the lower line read from the right vertical axis. In this graph, the mass value is obtained according to the rounded charge. That is, M = m / z × [Q] - [Q] × m p is. In this histogram, the isotope molecular species are resolved, but only for the charges that match the actual charge on the ion after rounding. All others result in a mass error of m / z × 1e = approximately 800 Da. These peaks are errors and cannot be distinguished from the true peaks in an actual experiment. Therefore, although rounding does improve the mass histogram, it is still not suitable for high-precision mass spectrometry.

[0082] Figures 5(b) and 5(c) show M = M0 + Δm isotIt shows a mass spectrum corresponding to the actual mass of a protein (i.e., the mass reduced by excluding the mass of all proton-added protons) in this form. Figure 5(b) is an enlarged view of a part of Figure 5(a), which omits the data corresponding to the generated mass value M and shows only the rounded integer charge value [Q]. Figure 5(c) is an enlarged view of Figure 5(b).

[0083] Figures 6(a) and (b) show mass histograms obtained after obtaining the mass after generating a new charge [Q i ^] using a scoring algorithm. Figure 6(b) shows an enlarged view of a part of Figure 6(a). The broadening of the peak width is due to frequency jitter, and the region of the red peak is maintained compared to the region of the black peak. In Figures 6(a) and (b), the data marked "Scored" shows the mass spectrum obtained after applying the scoring algorithm from the first data set (which has the "generated" mass spectrum shown in Figure 5(a)), and the data marked "true" represents the true mass distribution. There are no suspicious peaks, and it can be seen that the number of detected points (the area under the mass histogram) is equal to the number of masses (the area under the "true" curve) used in the simulation. Here, among multiple measured CDMS image charge / current signals, the similarity between the candidate frequency (f i Cand ) and the measured frequency (f j ) is calculated as the sum of the number of frequency candidate values (f j ) whose difference from any signal frequency (f i Cand ) is less than a predetermined difference threshold (ε) ("score" = S i Cand ). Here, ε = 0.5 Hz, and by using a scoring threshold = 4, the value of the "best score" must not exceed 4. The following are examples of scores considering three frequencies.

[0084] Frequency = 161.921602000 [kHz]: Assumed [Q] = 41: Score = 0 Assumed [Q]=42: Score = 0 Assumed [Q]=43: Score = 0 Assumed [Q]=44: Score = 0 Assumed [Q]=45: Score = 213 Assumed [Q]=46: Score = 0 Assumed [Q]=47: Score = 0 Best [Q]=[Q^]=45: Score = 213

[0085] Frequency = 180.610672000[kHz]: Assumed [Q]=52: Score = 0 Assumed [Q]=53: Score = 0 Assumed [Q]=54: Score = 0 Assumed [Q]=55: Score = 0 Assumed [Q]=56: Score = 161 Assumed [Q]=57: Score = 0 Assumed [Q]=58: Score = 0 Best [Q]=[Q^]=56: Score = 161

[0086] Frequency = 161.919572000[kHz]: Assumed [Q]=42: Score = 0 Assumed [Q]=43: Score = 0 Assumed [Q]=44: Score = 0 Assumed [Q]=45: Score = 242 Assumed [Q]=46: Score = 0 Assumed [Q]=47: Score = 0 Assumed [Q]=48: Score = 0 Best [Q]=[Q^]=45: Score = 242

[0087] Losses / additives as part of the mass spectrum

[0088] Figures 7(a) and (b) show the mass histograms of myoglobin (protein mass 17 kDa) obtained after improving the measured charge value Q using the scoring algorithm disclosed in this specification.

[0089] These are real experimental data. This mass histogram consists of a main envelope 30 that seems to correspond to the most likely protein mass and three accompanying envelopes 31. These accompanying envelopes 31 are thought to correspond to water loss products, sodium adducts in the form of cation Na + , water adducts, and potassium adducts in the form of cation K + . Na + and K + were not considered in the scoring algorithm during data processing, yet such envelopes as described above appear in this histogram. This is because if there is a peak caused by Na + , that peak will appear based on the next m / z position during scoring in all charge states.

Number

Number

[0090] f i Cand = 157.307912900 [kHz]: Assumed [Q] = 16: score = 2 Assumed [Q] = 17: score = 6 Assumed [Q] = 18: score = 45 Assumed [Q] = 19: score = 6 Assumed [Q] = 20: score = 8 Assumed [Q] = 21: score = 2 Assumed [Q] = 22: score = 5 Assumed [Q] = 23: score = 0 Assumed [Q] = 24: score = 2 Assumed [Q] = 25: score = 4 Assumed [Q] = 26: score = 7 Best [Q^] = 18: score = 45 Accepted result: New Q = [Q^] = 18, new mass = 16971.22218

[0091] f i Cand = 161.647224000 [kHz]: Assumed [Q] = 16: score = 4 Assumed [Q]=17: Score = 2 Assumed [Q]=18: Score = 10 Assumed [Q]=19: Score = 51 Assumed [Q]=20: Score = 8 Assumed [Q]=21: Score = 5 Assumed [Q]=22: Score = 3 Assumed [Q]=23: Score = 7 Assumed [Q]=24: Score = 2 Assumed [Q]=25: Score = 6 Assumed [Q]=26: Score = 8 Best [Q^]=19: Score = 51 Accepted result: New Q = [Q^]=19, New mass = 16965.19485

[0092] f i Cand =165.871058500[kHz]: Assumed [Q]=16: Score = 5 Assumed [Q]=17: Score = 7 Assumed [Q]=18: Score = 11 Assumed [Q]=19: Score = 11 Assumed [Q]=20: Score = 12 Assumed [Q]=21: Score = 4 Assumed [Q]=22: Score = 4 Assumed [Q]=23: Score = 6 Assumed [Q]=24: Score = 5 Assumed [Q]=25: Score = 8 Assumed [Q]=26: Score = 2 Best [Q^]=20: Score = 12 Accepted result: New Q = [Q^]=20, New mass = 16960.18229

[0093] f i Cand =169.912148600[kHz]: Assumed [Q]=16: Score = 23 Assumed [Q]=17: Score = 7 Assumed [Q]=18: Score = 7 Assumed [Q]=19: Score = 8 Assumed [Q]=20: Score = 25 Assumed [Q]=21: Score = 177 Assumed [Q]=22: Score = 13 Assumed [Q]=23: Score = 4 Assumed [Q]=24: Score = 5 Assumed [Q]=25: Score = 5 Assumed [Q]=26: Score = 5 Best [Q^]=21: Score = 177 Accepted result: New Q = [Q^]=21, New mass = 16971.18562

[0094] The advantage of the scoring approach disclosed in this specification is that, compared to simply averaging the charges, it is not necessary to know which molecules are being dealt with and which charge states should be assigned to points near a certain frequency. This method is not as targeted as the method of averaging charges, but is a more general-purpose method. It is applicable to proteins, antibodies, viruses, and all biomolecules that can carry multiple charges. This approach is also suitable for polyvalent molecules where large signal noise makes it impossible to accurately measure low charge states.

[0095] Aspects and features of the present invention are described in the following Sections A to O.

[0096] (Section A) A method for processing data determined from image charge / current signals representing a plurality of ions in a given charge state (Q) each undergoing oscillatory motion at a respective oscillation frequency (f) within an ion analyzer, comprising: A measured signal frequency (f) common to a plurality of measured image charge / current signals 0 and a data set including a plurality of estimated ion charge values corresponding to the amplitudes of each of the plurality of measured image charge / current signals are obtained, generating an integer charge value ([Q]) corresponding to rounding one of the estimated ion charge values to the nearest integer value, and (a) selecting the integer charge value ([Q i ) and using it to calculate a plurality of different image charge / current signal frequency candidate values (f 0 ) according to the selected measured signal frequency (f i Cand ) and according to one corresponding to one of one or more different charge state candidates of the ion and / or the isotope or isotopic molecular species of the ion, and (b) comparing the calculated plurality of image charge / current signal frequency candidate values (f i Cand ) with a plurality of different signal frequencies (f) of the measured image charge / current signals and calculating a score value representing the degree of similarity therebetween based on the comparison, if the score value matches or exceeds a score threshold, determining that the charge state (Q) of the ion undergoing oscillatory motion at the selected measured signal frequency (f 0) is equal to the integer charge value ([Q i ^]) including the method.

[0097] (Section B) The step of generating the integer charge value ([Q]) includes generating a plurality of integer charge values ([Q]) corresponding to rounding each of the estimated ion charge values to the nearest integer value, and (c) repeating steps (a) and (b) for each of the generated integer charge values ([Q]) among the generated integer charge values ([Q i ), and (d) identifying the integer charge value ([Q i ^]) that achieves the highest score value including, where the score threshold corresponds to the highest score value, and the charge state (Q) of the ion is determined to be equal to the identified integer charge value ([Q i ^]) that achieves the highest score value, the method according to item A.

[0098] (Item C) Calculating a plurality of different image charge / current signal frequency candidate values (f i Cand ) by selecting an integer n for quantifying the number of proton-added protons bound to the ion, an integer k for quantifying the difference in the number of neutrons in the nucleus between different isotopes or isotopologue species of the ion, the mass of a proton m p , the charge of a proton e, and a preset calibration constant α as

Number

[0099] (Item D) Calculating a plurality of different image charge / current signal frequency candidate values (f i Cand ) by selecting an integer l for quantifying the number of additional ions of mass m X bound to the ion, an integer n for quantifying the number of proton-added protons bound to the ion, an integer k for quantifying the difference in the number of neutrons in the nucleus between different isotopes or isotopologue species of the ion, the mass of a proton m p , the charge of a proton e, and a preset calibration constant α as

Number

[0100] (Item E) Obtaining the dataset includes selecting a measured signal frequency (f 0 ) common to the plurality of measured image charge / current signals, and calculating the plurality of estimated ion charge values based on the measured amplitude of each of the plurality of measured image charge / current signals, the method according to any one of items A to D.

[0101] (Item F) The similarity includes the sum of the number of calculated image charge / current signal frequency candidate values (f i Cand ) whose difference from any one of the signal frequencies of the plurality of measured image charge / current signals is smaller than a predetermined difference threshold, the method according to any one of items A to E.

[0102] (Item G) Calculating a plurality of different image charge / current signal frequency candidate values (f i Cand ) includes selecting a plurality of different candidate states of the isotope or isotopologue species (k) of the ion that share a common fixed candidate state of ion proton addition (n), the method according to any one of items A to F.

[0103] (Item H) A plurality of different image charge / current signal frequency candidate values (f i Cand Calculating (0) includes selecting a plurality of different candidate states of ion-proton addition (n), each sharing a common fixed candidate state of the isotope or isotopic molecular species (k) of the ion, according to any one of Items A to G.

[0104] (Item I) Calculating a plurality of different image charge / current signal frequency candidate values (f i Cand ) includes selecting different candidate states of ion-proton addition (n) and different candidate states of the isotope or isotopic molecular species (k) of the ion, according to any one of Items A to H.

[0105] (Item J) According to the identified integer charge value ([Q i ^]) that achieves the highest score value, and

Number

[0106] (Item K) An apparatus configured to process data determined from an image charge / current signal representing a plurality of ions in a given charge state (Q) each undergoing vibrational motion of a respective vibration frequency (f) within an ion analyzer, Obtaining a data set including a measured signal frequency (f 0 ) common to a plurality of measured image charge / current signals and a plurality of estimated ion charge values corresponding to the amplitudes of each of the plurality of measured image charge / current signals, Generating an integer charge value ([Q]) corresponding to rounding one of the estimated ion charge values to the nearest integer value, (a) Selecting the integer charge value ([Q i ) and using it to calculate a plurality of different image charge / current signal frequency candidate values (f i Cand ) according to the selected measured signal frequency (f0), and according to one or more different charge state candidates of the ion and / or the isotope or isotopic molecular species (k) of the ion, and (b) Comparing the calculated plurality of image charge / current signal frequency candidate values (f i Cand ) with the plurality of different signal frequencies (f) of the measured image charge / current signals and calculating a score value representing the similarity therebetween based on the comparison, If the score value matches or exceeds a score threshold, determining that the charge state (Q) of the ion undergoing vibrational motion of the selected measured signal frequency (f 0 ) is equal to the identified integer charge value ([Q i ^]) An apparatus comprising a processor module configured as such.

[0107] (Item L) The processor module generates integer charge values [Q] by generating a plurality of integer charge values ([Q]) corresponding to the estimated ion charge values each rounded to the nearest integer value, (c) repeating steps (a) and (b) for each of the generated integer charge values ([Q]) among the integer charge values ([Q i ), and (d) identifying the integer charge value ([Q i ^]) that achieves the highest score value, configured such that the score threshold corresponds to the highest score value, and the charge state (Q) of the ion is determined to be equal to the identified integer charge value ([Q i ^]) that achieves the highest score value, the apparatus according to Item K.

[0108] (Item M) An ion analyzer comprising the apparatus according to Item K or L.

[0109] (Item N) A computer program or computer program product adapted to execute the method according to any one of Items A to J.

[0110] (Item O) A computer-readable storage medium or data carrier comprising the computer program or computer program product according to Item N.

[0111] Each feature disclosed in the foregoing description, the claims hereinafter, or the accompanying drawings may, as necessary, be expressed in its specific form or from the perspective of means for performing the disclosed function or method or process for obtaining the disclosed result, but these features can be used, individually or in any combination of several features, to implement the present invention in its various forms.

[0112] In the foregoing, the present invention has been described in connection with exemplary embodiments, but many equivalent modifications and variations will be apparent to those skilled in the art in light of the disclosure of this application. Accordingly, the exemplary embodiments of the present invention described above should be regarded as illustrative and not limiting. Various changes can be made to the embodiments without departing from the spirit and scope of the present invention.

[0113] For the sake of avoiding doubt, it should be stated that any theoretical explanations made in this specification are for the purpose of deepening the reader's understanding. The inventors do not wish to be bound by any of these theoretical explanations. The headings used in this specification are for the purpose of organization only and should not be construed as limiting the described subject matter.

[0114] Throughout this specification, including the following claims, the words "comprise" and "include" and their variations (such as "comprises", "comprising", "including", etc.) should be construed to mean including the recited integer or step or group of integers or steps, but not to mean excluding other integers or steps or group of integers or steps, unless the context requires a different interpretation.

[0115] In addition, the singular forms used in this specification and the appended claims include cases where the object of indication is plural, unless the context clearly indicates otherwise. When representing a range in this specification, the term "about" may be attached to a certain specific numerical value as the starting point and / or another specific numerical value as the ending point. When the range is represented in such a manner, the form in which the certain specific numerical value is exactly the starting point and / or the other specific numerical value is exactly the ending point constitutes another embodiment. Similarly, when a value is represented as an approximate value due to the use of the prefix "about", it should be understood that the specific value constitutes another embodiment. The relationship between the term "about" and the numerical value is arbitrary and, for example, means ±10%.

[0116] References

[0117] So far, many publications have been cited to more fully explain and disclose the present invention and the state of the art related to the present invention. The complete list of cited documents is as follows. The respective entities of these references are incorporated herein by reference. W. Shockley: “Currents to Conductors Induced by a Moving Point Charge”, Journal of Applied Physics 9, 635 (1938)] S. Ramo: “Currents Induced by Electron Motion”, Proceedings of the IRE, Volume 27, Issue 9, Sept. 1939 WO2012 / 116765 (A1) (Ding et al.)

Claims

1. 1. A method of processing data determined from an image charge / current signal representative of a plurality of ions of a given charge state (Q) undergoing oscillatory motion at respective oscillatory frequencies (f) within an ion analyzer, comprising: The measured signal frequency (f ０ ) and a plurality of estimated ion charge values ​​corresponding to the amplitude of each of the plurality of measured image charge / current signals; generating an integer charge value ([Q]) corresponding to one of the estimated ion charge values ​​rounded to the nearest integer value; and (a) the integer charge value ([Q i ]) and using it to calculate the selected actual signal frequency (f ０ ) and in response to a corresponding one of one or more different candidate charge states of the ion and / or the ion's isotope or isotopic species, a plurality of different candidate image charge / current signal frequencies (f ｉ Ｃａｎｄ ), and (b) the calculated candidate image charge / current signal frequencies (f ｉ Ｃａｎｄ ) with a plurality of different signal frequencies (f) of the measured image charge / current signal, and calculating a score value representing the degree of similarity therebetween based on the comparison; If the score value meets or exceeds the score threshold, the selected measured signal frequency (f ０ The charge state (Q) of an ion undergoing vibrational motion of the integer charge value ([Q ｉ ^]) The method includes:

2. generating integer charge values ​​([Q]) comprising generating a plurality of integer charge values ​​([Q]) each corresponding to a rounded off value of the estimated ion charge value to the nearest integer value; and (c) each of the integer charge values ​​([Q]) among the generated integer charge values ​​([Q ｉ Repeating steps (a) and (b) for each (d) the integer charge value that achieves the highest score value ([Q ｉ ^]) wherein the score threshold corresponds to the highest score value, and the charge state (Q) of an ion is selected from the identified integer charge values ​​([Q ｉ 2. The method of claim 1 , wherein the first digit is determined to be equal to the first digit.

3. A number of different candidate image charge / current signal frequencies (f ｉ Ｃａｎｄ ) is calculated by using n as an integer chosen to quantify the number of protons attached to the ion, k as an integer chosen to quantify the difference in the number of neutrons in the nucleus between different isotopes or isotopic species of the ion, and m as the mass of the proton. ｐ , the charge of the proton is e, and a preset calibration constant is α. [0047] The method according to claim 1 or 2, wherein the method is carried out so as to satisfy the following condition.

4. A number of different candidate image charge / current signal frequencies (f ｉ Ｃａｎｄ ) is calculated by dividing the mass m Ｘ Let l be an integer chosen to quantify the number of adduct ions of , n be an integer chosen to quantify the number of protonated protons attached to the ion, k be an integer chosen to quantify the difference in the number of neutrons in the nucleus between different isotopes or isotopic species of the ion, and m be the mass of the proton. ｐ , the charge of the proton is e, and a preset calibration constant is α. [0048] The method according to any one of claims 1 to 3, wherein the method is carried out so as to satisfy the following condition.

5. Acquiring the data set includes determining a measured signal frequency (f ０ 5. The method of claim 1, further comprising: selecting a plurality of estimated ion charge values ​​based on a measured amplitude of each of the plurality of measured image charge / current signals.

6. The degree of similarity is determined by calculating a candidate image charge / current signal frequency (f ｉ Ｃａｎｄ The method according to any one of claims 1 to 5, comprising the sum of the numbers of

7. A number of different candidate image charge / current signal frequencies (f ｉ Ｃａｎｄ 7. The method of claim 1, wherein calculating (n) comprises selecting a plurality of different candidate states of an isotope or isotopic species (k) of the ion, each of which shares a common fixed candidate state of ion protonation (n).

8. A number of different candidate image charge / current signal frequencies (f ｉ Ｃａｎｄ 8. The method of claim 1, wherein calculating (n) comprises selecting a plurality of different candidate charge states for ion protonation (n), each of which shares a common fixed candidate state of an isotope or isotopic species (k) of the ion.

9. A number of different candidate image charge / current signal frequencies (f ｉ Ｃａｎｄ 9. The method of claim 1, wherein calculating n comprises selecting different ion protonations (n) of the ion and selecting different candidate states of isotopes or isotopic species (k) of the ion.

10. The identified integer charge value ([Q ｉ ^]) and, [0049] According to the above relationship, the selected measured signal frequency (f ０ 10. The method of claim 1, further comprising determining the mass value (M) of an ion undergoing vibrational motion of

11. 1. An apparatus configured to process data determined from an image charge / current signal representative of a plurality of ions of a given charge state (Q) undergoing oscillatory motion at respective oscillatory frequencies (f) within an ion analyzer, comprising: The measured signal frequency (f ０ ) and a plurality of estimated ion charge values ​​corresponding to the amplitude of each of the plurality of measured image charge / current signals; generating an integer charge value ([Q]) corresponding to one of the estimated ion charge values ​​rounded to the nearest integer value; (a) the integer charge value ([Q i ]) and using it to calculate the selected actual signal frequency (f ０ ) and in response to a corresponding one of one or more different candidate charge states of the ion and / or the ion's isotope or isotopic species (k), a plurality of different candidate image charge / current signal frequencies (f ｉ Ｃａｎｄ ), and (b) the calculated candidate image charge / current signal frequencies (f ｉ Ｃａｎｄ ) to a plurality of different signal frequencies (f) of the measured image charge / current signal and calculate a score value representing the degree of similarity therebetween based on the comparison; If the score value meets or exceeds the score threshold, the selected measured signal frequency (f ０ The charge state (Q) of an ion undergoing vibrational motion of the ion is determined by the identified integer charge value ([Q ｉ ^]) An apparatus including a processor module configured as described above

12. the processor module generates integer charge values ​​[Q] by generating a plurality of integer charge values ​​([Q]) each corresponding to the estimated ion charge value rounded to the nearest integer value; (c) each of the integer charge values ​​([Q]) among the generated integer charge values ​​([Q ｉ Repeating steps (a) and (b) for each (d) the integer charge value that achieves the highest score value ([Q ｉ ^]), wherein the score threshold corresponds to the highest score value, and the charge state (Q) of an ion is selected from the identified integer charge values ​​([Q ｉ 12. The apparatus of claim 11, wherein the first and second inputs are determined to be equal to each other.

13. An ion analyzer comprising a device according to any one of claims 11 or 12.

14. A computer program or computer program product adapted to carry out the method according to any of claims 1 to 10.

15. A computer readable storage medium or data carrier comprising a computer program or a computer program product according to claim 14.

Images