Disambiguation of spectra from a cyclic ion analyzer

Abstract

Method for operating an analyzer comprising an ion analyzer configured to analyze ions by determining ion drift times along an ion path, wherein the ion path comprises at least a first segment and a cyclic segment, wherein the ion path is configured such that ions make a single pass through the first segment and make one or more passes through the cyclic segment;the method comprises: operating the analyzer in a first operating mode, wherein in the first operating mode (i) a first electrical potential is provided along the first segment of the ion path, (ii) a second electrical potential is provided along the cyclic segment of the ion path, (iii) the first segment of the ion path has a first path length, and (iv) the cyclic segment of the ion path has a second path length, and analyzing ions by determining drift times of ions along the ion path to obtain a first set of ion data; operating the analyzer in a second operating mode by changing at least one of (i) the second electrical potential and (ii) the second path length, and analyzing ions by determining drift times along the ion path to obtain a second set of ion data;Comparing the first set of ion data with the second set of ion data, and identifying a first ion peak in the first set of ion data that corresponds to a second ion peak in the second set of ion data; determining the number N of iterations of the cyclic segment of the ion path taken by ions assigned to the corresponding first and second ion peaks; and using the determined number N of iterations to determine a value of a physicochemical property of the ions assigned to the corresponding first and second ion peaks.

Description

AREA OF INVENTION

[0001] The present invention relates to methods for the analysis of ions and in particular to time-of-flight (ToF) mass analyzers and ion mobility analyzers. STATE OF THE ART

[0002] In time-of-flight (ToF) analyzers and ion mobility analyzers, ions are passed through a drift chamber of the analyzer and finally detected. A physicochemical property of an ion, such as its mass-to-charge ratio (m / z) or its ion mobility, is determined from the ion's drift time through the drift chamber.

[0003] It is often desirable to increase the resolution of an analyzer, both for improved separation of analyte ions and for accurate determination of their physicochemical properties, such as mass. The resolution of an instrument is limited by the total length of the ion flight path through the analyzer.

[0004] There are several "cyclic" analysis techniques in which ions are made to complete multiple repeated cycles along an ion flight path within the analyzer. Increasing the number of cycles, N, increases the length of the ion flight path taken within the analyzer, thereby increasing the analyzer's resolution.

[0005] During several cycles N through the analyzer, however, lighter, faster-moving ions can catch up with (e.g., overtake) heavier, slower ions. This complicates the resulting spectra and can make it difficult to accurately determine the physicochemical properties of all detected ions.

[0006] It is assumed that there is room for improvement in the operating procedures of ion analyzers. SUMMARY

[0007] A first consideration provides a method for operating an analytical instrument comprising an ion analyzer configured to analyze ions by determining ion drift times along an ion path, wherein the ion path comprises at least a first segment and a cyclic segment, the ion path being configured such that ions make a single pass through the first segment and one or more passes through the cyclic segment; wherein the method comprises: Operating the analyzer in a first operating mode, wherein in the first operating mode (i) a first electrical potential is provided along the first segment of the ion path, (ii) a second electrical potential is provided along the cyclic segment of the ion path, (iii) the first segment of the ion path has a first path length, and (iv) the cyclic segment of the ion path has a second path length, and analyzing ions by determining drift times of ions along the ion path to obtain a first set of ion data; Operating the analyzer in a second operating mode by changing at least one of (i) the first electrical potential, (ii) the second electrical potential, (iii) the first path length and (iv) the second path length, and analyzing ions by determining drift times along the ion path to obtain a second set of ion data; Comparing the first set of ion data with the second set of ion data, and identifying a first ion peak in the first set of ion data that corresponds to a second ion peak in the second set of ion data; Determining the number N of iterations of the cyclic segment of the ion path taken by ions assigned to the corresponding first and second ion peaks; and Using the specified number of iterations N to determine a physicochemical property of the ions assigned to the corresponding first and second ion peaks.

[0008] Embodiments relate to methods for operating a cyclic ion analyzer. The analyzer is configured to analyze ions by determining (e.g., measuring) the drift times of the ions along an ion path, whereby the ions may complete multiple passes through a cyclic segment of the ion path before being detected. In cyclic analyzers, ions exhibiting very different physicochemical properties (e.g., mass-to-charge ratio (m / z) or ion mobility) may have similar drift times through the analyzer, for example, due to the fact that faster-moving ions catch up with (e.g., overtake) slower-moving ions in the cyclic segment of the ion path. This can complicate the resulting spectra and make it difficult to accurately determine the physicochemical properties of the detected ions.

[0009] Embodiments provide methods for disambiguating the spectra generated by cyclic ion analyzers. As described in more detail below, by comparing two sets of ion data obtained using different analyzer settings, the number N of passes through the cyclic segment of the ion path taken by ions contributing to an ion peak can be determined, thus enabling the physicochemical properties of these ions to be uniquely assigned to the ion peak.

[0010] The analytical instrument can be a mass spectrometer, an ion mobility spectrometer, or a combination of both (e.g., a mass spectrometer that includes an ion mobility separator). The instrument can include an ion source. Ions can be generated from a sample in the ion source. The ions can be guided from the ion source to the analyzer via one or more ion optics devices positioned between the ion source and the analyzer.

[0011] The one or more ion optic devices may comprise any suitable arrangement of one or more ion guides, one or more lenses, one or more gates, and the like. The one or more ion optic devices may include one or more ion transfer guides for transferring ions, and / or one or more mass selectors or filters for mass-selecting ions, and / or one or more ion cooling guides for cooling ions, and / or one or more collision or reaction cells for fragmenting or reacting ions, and so on. One or more, or each, ion guide may comprise a multipole ion guide, such as a quadrupole ion guide, hexapole ion guide, etc., a segmented multipole ion guide, a stacked ring-type ion guide, and the like.

[0012] The ion analyzer is configured to analyze ions by determining the drift times of ions along an ion path. Thus, the ion analyzer can include an ion injector located at the beginning of the ion path and an ion detector located at the end of the ion path. The ion injector can be configured to capture ions from the ion source via one or more ion optic devices. The ion injector can be configured to inject ions into the ion path (e.g., by accelerating ions along the path), whereupon the ions move along the path to the detector. The ion injector can be in any suitable form, such as an ion trap or one or more (e.g., orthogonal) accelerating electrodes. Upon reaching the detector, the ions can be detected, and their arrival time, for example, can be recorded.From the measured drift time, a physicochemical property of the ions, such as their mass-to-charge ratio and / or their ion mobility, can then be determined.

[0013] The ion analyzer is a cyclic analyzer. Thus, the ion path includes a cyclic segment, where ions can complete multiple (repeated) passages through the cyclic segment as they move along the ion path (from the ion injector to the detector). The ion path also includes at least one first (non-cyclic) segment, where ions complete only a single passage through the first segment as they move along the ion path (from the ion injector to the detector). The first segment can be directly adjacent to the cyclic segment of the ion path. The first segment can be located upstream or downstream of the cyclic segment.

[0014] The ion path can optionally include a second (non-cyclic) segment, where ions make only a single pass through the second segment as they move along the ion path (from the ion injector to the detector). The second segment can be directly adjacent to (i.e., directly connected to) the cyclic segment of the ion path. The second segment can be upstream or downstream of the cyclic segment, such that the ion path includes a first (non-cyclic) segment, a cyclic segment located downstream of the first segment, and a second (non-cyclic) segment located downstream of the cyclic segment.

[0015] Thus, as ions move along the ion path (from the ion injector to the detector), they can complete a single pass through the first segment, followed by one or more (e.g., multiple) passes through the cyclic segment, optionally followed by a single pass through the second segment, before being detected.

[0016] The ion analyzer can be a time-of-flight (ToF) mass analyzer configured to determine the mass-to-charge ratio (m / z) of ions from their drift times, or an ion mobility analyzer configured to determine the ion mobility of ions from their drift times.

[0017] In embodiments, the analyzer is a closed-loop, multi-reflection ion-trap mass analyzer. Thus, the analyzer can comprise two ion mirrors spaced apart and facing each other in a first direction X, an ion injector for injecting ions into a space between the ion mirrors, and a detector for capturing ions after they have completed a multitude of reflections between the ion mirrors. The two ion mirrors can together form an ion trap. The two ion mirrors can be configured such that ions trapped in the ion trap oscillate between the ion mirrors (in the first direction X), e.g., indefinitely, until they are released for detection. Ion inlet and extraction into the ion trap can be controlled by applying suitable voltage(s) to a deflector located in the region between the mirrors.

[0018] In these embodiments, the ion path can be configured such that ions make a single pass through a first segment of the ion path between the injector and the deflector, then make multiple passes through a cyclic segment of the ion path between the ion mirrors, and then make a single pass through a second segment of the ion path between the deflector and the detector.

[0019] In particular embodiments, the analyzer is a multi-reflection time-of-flight analyzer (MR-ToF), which can, for example, be configured to operate in a so-called "zoom" mode. Thus, the analyzer can comprise two ion mirrors spaced apart and facing each other in a first direction X, each mirror generally extended along a drift direction Y between a first end and a second end, the drift direction Y being orthogonal to the first direction X; an ion injector for injecting ions into a space between the ion mirrors, the ion injector being located near the first end of the ion mirrors; and a detector for detecting ions after they have completed a multitude of reflections between the ion mirrors, the detector being located near the first end of the ion mirrors.

[0020] The analyzer can be configured to analyze ions by: (i) Injecting ions from the ion injector into the space between the ion mirrors, the ions completing a first cycle in which the ions follow a zigzag ion path that has multiple K reflections between the ion mirrors in the X direction, while: (a) they drift along the Y direction towards the second end of the ion mirrors, (b) reverse the drift direction velocity near the second end of the ion mirrors, and (c) drift back along the Y direction towards the first end of the ion mirrors; (ii) they reverse the drift direction velocity of the ions near the first end of the ion mirrors, such that the ions are caused to complete a further cycle in which the ions follow a zigzag ion path that has multiple K reflections between the ion mirrors in the X direction, while: (a) they drift along the Y direction towards the second end of the ion mirrors, (b) they reverse the drift direction velocity near the second end of the ion mirrors, and (c) they drift back along the Y direction towards the first end of the ion mirrors; (iii) Repeat step (ii) once or several times; and then (iv) cause the ions to move towards the detector for detection.

[0021] The analyzer may further include a deflector or lens located near the first end of the ion mirrors. The analyzer may be configured to analyze ions by: (i) Injecting ions from the ion injector into the space between the ion mirrors, the ions completing a first cycle in which the ions follow a zigzag ion path exhibiting multiple K-reflections between the ion mirrors in the X direction, while: (a) drifting along the drift direction Y from the deflector or lens towards the second end of the ion mirrors, (b) reversing the drift direction velocity near the second end of the ion mirrors, and (c) drifting back along the drift direction Y towards the deflector or lens; (ii) Using the deflector or lens to reverse the drift direction velocity of the ions such that the ions are caused to complete a further cycle in which the ions follow a zigzag ion path that has multiple K-reflections between the ion mirrors in the X direction, while: (a) drifting along the drift direction Y from the deflector or lens towards the second end of the ion mirrors, (b) reversing the drift direction velocity near the second end of the ion mirrors, and (c) drifting back along the drift direction Y towards the deflector or lens; (iii) Repeat step (ii) once or several times; and then (iv) Causing the ions to move from the deflector or lens to the detector for detection.

[0022] The deflector or lens can be positioned approximately equidistant (in the X direction) between the first and second ion mirrors. The deflector or lens can be positioned along the ion path after the first ion mirror reflection (in the first ion mirror), which the ion beam experiences after being injected by the injector but before its second ion mirror reflection (in the second ion mirror). Similarly, the deflector or lens can be positioned along the ion path before the final ion mirror reflection (in the second ion mirror), which the ion beam experiences before reaching the detector but after its penultimate ion mirror reflection (in the first ion mirror).

[0023] The multiple reflection time-of-flight (ToF) mass analyzer can incorporate any suitable type of MR-ToF. For example, the analyzer can include an MR-ToF with a set of periodic lenses configured to keep the ion beam focused along its trajectory, as described in the article by A. Verenchikov et al., Journal of Applied Solution Chemistry and Modelling, 2017, 6, 1-22.

[0024] In particular embodiments, however, the analyzer is a multi-reflection time-of-flight mass analyzer of the inclined-mirror type, e.g., of the type described in U.S. Patent No. 9,136,101, the contents of which are incorporated herein by reference. Thus, the ion mirrors can have a non-constant distance from each other in the X-direction along at least a portion of their lengths in the drift direction Y. An electric field resulting from the non-constant distance between the two mirrors can oppose the drift velocity of ions toward the second end of the ion mirrors. This electric field can cause the ions to reverse their drift velocity near the second end of the ion mirrors and drift back toward the deflector along the drift direction.

[0025] Alternatively, the analyzer can be a single multi-reflection time-of-flight mass analyzer of the focusing lens type, e.g., of the type described in UK Patent No. 2,580,089, the contents of which are incorporated herein by reference. Thus, the deflector can be a first deflector, and the analyzer can include a second deflector located near the second end of the ion mirrors. The second deflector can be configured to cause the ions to reverse their drift direction velocity near the second end of the ion mirrors and drift back along the drift direction towards the deflector. This can be achieved by applying a suitable voltage to the second deflector, e.g., in the manner described in UK Patent No. 2,580,089.

[0026] In embodiments, the deflector can comprise one or more trapezoidal or prismatic electrodes arranged adjacent to the ion beam. This deflector design has a sufficiently wide acceptance range to allow an ion beam that is relatively widely spread in the drift direction to be properly captured and deflected by the deflector. The deflector can include a first trapezoidal or prismatic electrode positioned above the ion beam and a second trapezoidal or prismatic electrode positioned below the ion beam. The electrode(s) can be angled relative to the ion beam such that when a suitable DC voltage is applied to the electrode(s), the resulting electric field induces a deflection in the ion beam. Suitable deflection voltages are on the order of ± a few volts, ± a few tens of volts, or ± a few hundred volts.

[0027] The deflector should be configured (and is in some embodiments) to cause the ion beam to be deflected by a desired (selected) angle. The angle by which the ion beam is deflected by the deflector can be adjustable, for example, by adjusting the magnitude of one or more (DC) voltages applied to the deflector. The deflector can be configured to deflect the ion beam by any desired angle.

[0028] In embodiments, the method comprises injecting ions from the ion injector into the space between the ion mirrors. The ions can then be reflected in the first ion mirror and subsequently travel to the deflector. Once the ions reach the deflector, the deflector can be configured so as not to deflect the ion beam (or so as to deflect the ion beam by a suitably small angle), for example, such that the drift velocity of the ions is substantially unchanged, allowing the ions to pass beyond the deflector and be reflected in the second ion mirror. This can involve, for example, applying or removing a voltage from the deflector (or applying a suitably small voltage to the deflector).The ions are then caused to complete a first cycle in which the ions follow a zigzag ion path that has multiple (K) reflections between the ion mirrors in the X direction, while: (a) they drift along the Y direction from the deflector towards the second end of the ion mirrors, (b) reverse the drift direction velocity near the second end of the ion mirrors, and (c) drift back along the Y direction towards the deflector.

[0029] After the ions have completed this first cycle, the deflector can be used to reverse the drift velocity of the ions, causing them to complete a further cycle in which they follow a zigzag ion path exhibiting multiple (K) reflections between the ion mirrors in the X direction, while: (a) they drift along the Y direction from the deflector toward the second end of the ion mirrors, (b) the drift velocity reverses near the second end of the ion mirrors, and (c) they drift back along the Y direction toward the deflector. For this purpose, the deflector can be configured to deflect the ion beam, for example, by reversing the drift velocity of the ions. This may involve applying one or more suitable voltages to the deflector, for example, during a period when the ions are expected to return to the deflector.Suitable deflection voltages for reversing the drift direction of the ions are on the order of a few hundred volts.

[0030] The step of using the deflector to reverse the drift direction velocity of the ions can be repeated one or more times. Thus, the procedure can involve causing the ions to complete several (N) cycles within the analyzer, with in each cycle the ions following a zigzag ion path that exhibits several (K) reflections between the ion mirrors in the X direction while: (a) they drift along the Y direction from the deflector toward the second end of the ion mirrors, (b) they reverse the drift direction velocity near the second end of the ion mirrors, and (c) they drift back along the Y direction toward the deflector.The first cycle can be initiated by injecting the ions into the space between the ion mirrors, and after the ions have completed the first cycle, each subsequent cycle can be initiated by using the deflector to reverse the drift direction velocity of the ions.

[0031] The method can include causing the ions to move from the deflector to the detector for detection. That is, after the ions have completed the desired (multiple) number (N) of cycles within the analyzer, they can move from the deflector to the detector for detection. For this purpose, the deflector can be configured so that it does not deflect the ion beam (or deflects the ion beam by a suitably small angle), for example, such that the drift velocity of the ions is not substantially changed, allowing the ions to pass beyond the deflector, be reflected in the second ion mirror, and continue to the detector. This can, for example, involve not applying or removing one or more voltages from the deflector (or applying a suitably small voltage to the deflector) so that the ions are caused to leave the deflector in a direction toward the detector.The ions can be reflected in one of the ion mirrors before moving to the detector.

[0032] Upon reaching the detector, the ions can be detected; for example, their arrival time can be recorded. The flight time and / or mass-to-charge ratio of the ions can then be determined, optionally combined with flight time and / or mass-to-charge ratio information from other ions, and a mass spectrum can be generated, for example. It should be noted that not all ions injected into the analyzer can be detected, for example, due to unavoidable losses at various points between the injector and the detector and / or detector inefficiencies. Thus, as used herein, the term "the ions" should be understood to mean "some, most, or all of the ions."

[0033] In these embodiments, the ion path can be configured such that ions make a single pass of a first segment of the ion path between the injector and the deflector or lens, then make multiple passes of a cyclic segment of the ion path between the first and second ends of the ion mirrors, and then make a single pass of a second segment of the ion path between the deflector or lens and the detector.

[0034] In this method, the analyzer is initially operated in a first operating mode, and ions are analyzed while the analyzer is operating in this first mode (by determining drift times of ions along the ion path) to obtain a first set of ion data. The analyzer is then switched to a second operating mode, and ions are analyzed while the analyzer is operating in this second mode (by determining drift times of ions along the ion path) to obtain a second set of ion data.

[0035] The first set of ion data can include multiple ion peaks. The number N of passes of the cyclic segment of the ion pathway made by ions corresponding to some, most, or all of the ion peaks in the first set of ion data (i.e., resulting in them) can be ambiguous. Similarly, the second set of ion data can include multiple ion peaks, and the number N of passes of the cyclic segment of the ion pathway made by ions corresponding to some, most, or all of the ion peaks in the second set of ion data (i.e., resulting in them) can be ambiguous. The first and second sets of ion data can be determined by analyzing ions from the same sample (e.g.,by analyzing ions produced from neighboring regions of a sample and / or by analyzing ions produced from a sample at close (adjacent) time points), e.g. such that ion peaks corresponding to some, most or all (significant) ion peaks in the first set of ion data appear in the second set of ion data.

[0036] In the first operating mode, (i) a first electrical potential is provided along the first segment of the ion path, (ii) a second electrical potential is provided along the cyclic segment of the ion path, (iii) the first segment of the ion path has a first path length, and (iv) the cyclic segment of the ion path has a second path length. The first electrical potential can be provided along part of the first segment, most of the first segment, or all of the first segment of the ion path. Similarly, the second electrical potential can be provided along part of the cyclic segment, most of the cyclic segment, or all of the cyclic segment of the ion path. The first path length can be the path length of the entire first segment.The second path length can be the path length taken by ions in a single cycle (a single loop) of the cyclic segment of the ion path.

[0037] In the second operating mode, at least one of (i) the first electrical potential, (ii) the second electrical potential, (iii) the first path length, and (iv) the second path length is modified with respect to the first operating mode. Thus, the method may involve switching the analyzer from the first operating mode to the second operating mode by at least one of: (i) changing the first electrical potential, (ii) changing the second electrical potential, (iii) changing the first path length, and (iv) changing the second path length. The modification may be such that its effect on the drift time of ions along the first segment is proportional to its effect on the drift time of ions along the cyclic segment.Thus, for example, in certain embodiments, only one of (i) the first electrical potential, (ii) the second electrical potential, (iii) the first path length and (iv) the second path length is changed with respect to the first operating mode (and the others are not changed between the first and second operating modes).

[0038] In particular embodiments where the analyzer is a multi-reflection time-of-flight (ToF) mass analyzer (as described above), the method includes changing the second path length in the second operating mode by changing the number K of reflections that ions form between the ion mirrors while tracing the zigzag ion path. This can be achieved by changing the angle at which the ion beam is deflected from the deflector, i.e., by changing the voltage applied to the deflector. Suitable deflection voltage shifts to thus change the beam angle are on the order of a few volts or several tens of volts.

[0039] Thus, in the first operating mode, the analyzer can be configured such that in each cycle, ions make a first number K1 of reflections between the ion mirrors in the X-direction, while: (a) they drift along the Y-direction from the deflector toward the second end of the ion mirrors, (b) the drift direction reverses near the second end of the ion mirrors, and (c) they drift back along the Y-direction toward the deflector. In the second operating mode, the analyzer can be configured such that in each cycle, ions make a second, different number K2 of reflections between the ion mirrors in the X-direction, while: (a) they drift along the Y-direction from the deflector toward the second end of the ion mirrors, (b) the drift direction reverses near the second end of the ion mirrors, and (c) they drift back along the Y-direction toward the deflector.The first and second numbers can differ by a small integer amount, such as one, i.e., |K1-K2| = 1.

[0040] In alternative embodiments, the method includes changing part, most, or all of the electrical potential in the second operating mode. Thus, in the first operating mode, the analyzer can be configured to provide a first electrical potential distribution along the first segment of the ion path, and in the second operating mode, the analyzer can be configured to provide a different electrical potential distribution along the first segment of the ion path.

[0041] The first and second electrical potential distributions can differ such that the electric field experienced by ions moving along the first segment in the first operating mode differs from the electric field experienced by ions moving along the first segment in the second operating mode. This difference can cause the flight time of ions (with a given m / z) along the first segment in the first operating mode to differ from the flight time of ions (with the same given m / z) along the first segment in the second operating mode. This flight time difference can depend on (e.g., be proportional to) the mass-to-charge ratio (m / z) of the ions.Thus, changing the first electrical potential between the first and second operating modes can lead to a mass-to-charge dependent time-of-flight shift of ions traveling along the first segment between the first and second operating modes.

[0042] The first electrical potential can be changed between the two operating modes in any suitable way. For example, the device can include a flight tube arranged along at least part of the first segment of the ion path, and the method can involve changing the first electrical potential in the second operating mode by changing a voltage applied to the flight tube (relative to a voltage applied to the flight tube in the first operating mode). Alternatively, the method can involve changing the first electrical potential in the second operating mode by changing a (pulsed) acceleration field provided by the ion injector (where, for example, the ion injector acts as an ion trap by changing a (pulsed) extraction field provided within the ion injector).This can be achieved by changing one or more pulsed accelerating voltages applied to one or more electrodes of the ion injector. Thus, in the first operating mode, the ion injector can be configured to accelerate ions along the ion path using a first accelerating field (one or more first accelerating voltages), and in the second operating mode, the ion injector can be configured to accelerate ions along the ion path using a different second accelerating field (one or more different second accelerating voltages). Suitable accelerating fields for the ion injector are on the order of a few hundred V / mm, and suitable accelerating field shifts between the first and second operating modes are on the order of several tens of V / mm.The method involves comparing the first set of ion data with the second set of ion data, for example, to identify a first ion peak in the first set of ion data that corresponds to a second ion peak in the second set of ion data. The method can include identifying several such pairs of corresponding ion peaks in the first and second sets of ion data. An ion peak can correspond to another ion peak if the ions that give rise to these ion peaks have the same physicochemical property (e.g., they can be of the same species).

[0043] Identifying a first ion peak in the first set of ion data that corresponds to a second ion peak in the second set of ion data may involve identifying ion peaks that exhibit values ​​of the physicochemical property within an expected (e.g., small) range.

[0044] Alternatively, identifying a first ion peak in the first set of ion data that corresponds to a second ion peak in the second set of ion data can include the following: Determine, for each ion peak of one or more ion peaks in the first set of ion data, a first list of possible values ​​of the physicochemical property that ions assigned to that ion peak could have; Determine, for each ion peak of one or more ion peaks in the second set of ion data, a second list of possible values ​​of the physicochemical property that ions assigned to that ion peak could have; and Comparing the first list with the second list and identifying, based on this comparison, an ion peak in the first set of ion data that corresponds to an ion peak in the second set of ion data. This can be done by identifying ion peaks that have the same values ​​or values ​​of the physicochemical property within an expected error range.

[0045] The procedure involves determining the number N of traverses of the cyclic segment of the ion path driven by ions corresponding to (i.e., resulting in) the respective first and second ion peaks. This determination can be based on comparing the first set of ion data with the second set of ion data. For example, determining the number N of traverses of the cyclic segment of the ion path driven by ions assigned to the corresponding first and second ion peaks can involve measuring a drift time difference between the first and second ion peaks and using the measured drift time difference to estimate the number N of traverses of the cyclic segment of the ion path driven by ions assigned to the corresponding first and second ion peaks.

[0046] The procedure involves using a specific number of iterations N to determine a value for the physicochemical property of the ions corresponding to (i.e., resulting from) the respective first and second ion peaks. This process of determining a value for the physicochemical property of the pair of corresponding ion peaks (based on the determined value of N) can be repeated for each identified pair of corresponding ion peaks of interest.

[0047] Another aspect is a non-volatile, computer-readable storage medium that stores computer software code which, when executed on a processor, performs the procedure(s) described above.

[0048] Another aspect is providing a control system for an analytical instrument, such as a mass and / or ion mobility spectrometer, wherein the control system is configured to cause the analytical instrument to perform the procedure(s) described above.

[0049] Another aspect is provided by an analytical instrument, such as a mass and / or ion mobility spectrometer, which includes the control system described above.

[0050] Another aspect is provided by an analytical instrument, such as a mass and / or ion mobility spectrometer, including: an ion analyzer configured to analyze ions by determining ion drift times along an ion path, wherein the ion path comprises at least a first segment and a cyclic segment, the ion path being configured such that ions make a single pass through the first segment and one or more passes through the cyclic segment; and a control system configured to: Operating the analyzer in a first operating mode and analyzing ions by determining drift times of ions along the ion path to obtain a first set of ion data, wherein in the first operating mode (i) a first electrical potential is provided along the first segment of the ion path, (ii) a second electrical potential is provided along the cyclic segment of the ion path, (iii) the first segment of the ion path has a first path length, and (iv) the cyclic segment of the ion path has a second path length; Operating the analyzer in a second operating mode by changing at least one of (i) the first electrical potential, (ii) the second electrical potential, (iii) the first path length and (iv) the second path length, and analyzing ions by determining drift times along the ion path to obtain a second set of ion data; Comparing the first set of ion data with the second set of ion data, and identifying a first ion peak in the first set of ion data that corresponds to a second ion peak in the second set of ion data; Determining the number N of iterations of the cyclic segment of the ion path taken by ions assigned to the corresponding first and second ion peaks; and Using the specified number of iterations N to determine a physicochemical property of the ions assigned to the corresponding first and second ion peaks.

[0051] These considerations and embodiments can, and in embodiments do, include any or more of the optional features described herein.

[0052] For example, the ion analyzer can be a time-of-flight (ToF) mass analyzer, and the physicochemical property can be a mass-to-charge ratio (m / z).

[0053] Thus, the analyzer can include the following: two ion mirrors spaced apart and facing each other in a first direction X, each mirror generally being extended along a drift direction Y between a first end and a second end, the drift direction Y being orthogonal to the first direction X; an ion injector for injecting ions into a space between the ion mirrors, wherein the ion injector is located near the first end of the ion mirrors; and a detector for detecting ions after they have completed a multitude of reflections between the ion mirrors, the detector being located near the first end of the ion mirrors;

[0054] The analyzer can be configured to analyze ions by: (i) Injecting ions from the ion injector into the space between the ion mirrors, the ions completing a first cycle in which the ions follow a zigzag ion path that has multiple K reflections between the ion mirrors in the X direction, while: (a) they drift along the Y direction towards the second end of the ion mirrors, (b) reverse the drift direction velocity near the second end of the ion mirrors, and (c) drift back along the Y direction towards the first end of the ion mirrors; (ii) they reverse the drift direction velocity of the ions near the first end of the ion mirrors, such that the ions are caused to complete a further cycle in which the ions follow a zigzag ion path that has multiple K reflections between the ion mirrors in the X direction, while: (a) they drift along the Y direction towards the second end of the ion mirrors, (b) they reverse the drift direction velocity near the second end of the ion mirrors, and (c) they drift back along the Y direction towards the first end of the ion mirrors; (iii) Repeat step (ii) once or several times; and then (iv) cause the ions to move towards the detector for detection.

[0055] Alternatively, the analyzer can be an ion mobility analyzer, and the physicochemical property can be ion mobility. DESCRIPTION OF THE DRAWINGS

[0056] Various embodiments are now described in more detail with reference to the attached figures, in which: Fig. 1 schematically shows an analysis device according to embodiments; Fig. Figure 2 schematically shows a cyclic ion analyzer according to embodiments; Fig. Figure 3 schematically shows a multi-reflection ion trap mass analyzer with a closed circuit according to embodiments; Fig. Figure 4 schematically shows a multiple reflection time-of-flight mass analyzer according to embodiments; Fig. Figure 5 schematically shows a multi-reflection time-of-flight mass analyzer according to embodiments; Fig. Figure 6 schematically shows a method for disambiguating spectra obtained from a cyclic ion analyzer according to embodiments; Fig.Figure 7 schematically shows a method for disambiguating spectra obtained from a cyclic ion analyzer according to embodiments; Fig. Figure 8 schematically shows a cyclic ion analyzer according to embodiments; Fig. Figure 9 illustrates how different m / z ions can fall into different numbers of cycles in a cyclic analyzer and the resulting complex time-of-flight spectrum; Fig. 10A shows complicated time-of-flight spectra, and Fig. 10B shows a recovered mass spectrum found using a method according to embodiments; Fig. 11A shows measured ion peaks for m / z-524 ions that were recorded when the device was Fig. 4 was operated without the zoom mode, and Fig. 11B-D measured ion peaks for m / z-524 ions show that were recorded when the instrument was Fig.4 was operated with the zoom mode according to embodiments; Fig. 12 mass spectra of a calibration solution are shown, which are obtained using a zoom mode according to embodiments; and Fig. 13 data from a disambiguation procedure according to embodiments is shown. DETAILED DESCRIPTION

[0057] Fig. Figure 1 schematically illustrates an analytical instrument that can be operated according to embodiments. The analytical instrument can be a mass spectrometer (which may optionally include an ion mobility separator) or an ion mobility spectrometer. As shown in Fig. As shown in Figure 1, the analyzer includes an ion source 10, one or more ion transfer stages 20 and an analyzer 30.

[0058] The ion source 10 is configured to generate ions from a sample. The ion source 10 can be any suitable continuous or pulsed ion source, such as an electrospray ionization (ESI) source, a MALDI ion source, an atmospheric pressure ionization (API) source, a plasma ion source, an electron ionization source, a chemical ionization ion source, and so on. In some embodiments, more than one ion source can be provided and used. The ions can be any suitable type of ions to be analyzed, e.g., small and large organic molecules, biomolecules, DNA, RNA, proteins, peptides, fragments thereof, and the like.

[0059] The ion source 10 can optionally be coupled with a separation device, such as a liquid chromatography separation device or a capillary electrophoresis separation device (not shown), so that the sample ionized in the ion source 10 originates from the separation device.

[0060] The ion transfer stage(s) 20 are arranged downstream of the ion source 10 and may include an atmospheric pressure interface and one or more ion guides, lenses, and / or other ion optics devices configured to transfer some or all of the ions generated by the ion source 10 from the ion source 10 to the analyzer 30. The ion transfer stage(s) 20 may include any suitable number and configuration of ion optics devices, for example, optionally one or more of the following: one or more RF and / or multipole ion guides, one or more cooling ion guides, one or more mass-selective ion guides, and so on.

[0061] The analyzer 30 is located downstream of the ion transfer stage(s) 20 and is configured to collect ions from the ion transfer stage(s) 20. The analyzer is configured to analyze the ions in order to determine a physicochemical property of the ions, such as their mass-to-charge ratio, mass, ion mobility, and / or collision cross-section (CCS). For this purpose, the analyzer 30 is configured to move ions along an ion path within the analyzer 30 and to measure the time required (the drift time) for ions to travel along the ion path. Thus, the analyzer 30 can include an ion detector located at the end of the ion path, with the analyzer configured to record the arrival time of ions at the detector. The instrument can be configured to determine the physicochemical property of the ions from their measured drift time.The device can be configured to generate a spectrum of the analyzed ions, such as a mass spectrum or an ion mobility spectrum.

[0062] In certain embodiments, the analyzer 30 is a time-of-flight (ToF) mass analyzer, e.g. configured to determine the mass-to-charge ratio (m / z) of ions by moving the ions along an ion path within a drift range of the analyzer, the drift range being at high vacuum (e.g. < 1 × 10 -5Ions are held in a pressure of approximately 1 mbar. They can be accelerated into the drift region by an electric field and detected by an ion detector located at the end of the ion path. The acceleration can cause ions with a relatively low mass-to-charge ratio to reach a relatively high velocity and arrive at the ion detector before ions with a relatively high mass-to-charge ratio. Thus, ions reach the ion detector after a time determined by their velocity and the length of the ion path, allowing the mass-to-charge ratio of the ions to be determined. Each ion or group of ions arriving at the detector can be sampled, and the signal from the detector can be digitized. A processor can then determine a value indicating the time of flight and / or the mass-to-charge ratio (m / z) of the ion or group of ions.Data for multiple ions can be collected and combined to generate a time-of-flight (“ToF”) spectrum and / or a mass spectrum.

[0063] In alternative embodiments, the analyzer 30 is an ion mobility analyzer, configured, for example, to determine the ion mobility of ions by guiding the ions along an ion path within a drift region of the analyzer, with a buffer gas provided in the drift region. Ions can be forced through the buffer gas by an electric field (or ions can be forced through the drift region by a gas flow, with an electric field provided to oppose the gas flow) and can be detected by an ion detector located at the end of the ion path. Ions with relatively high mobility reach the ion detector before ions with relatively low mobility. Thus, ions can be separated according to their ion mobility and can reach the ion detector after a time determined by their ion mobility.Each ion or group of ions arriving at the detector can be scanned, and the signal from the detector can be digitized. A processor can then determine a value indicating the drift time and / or ion mobility of the ion or group of ions. Data for multiple ions can be collected and combined to generate a drift time spectrum and / or an ion mobility spectrum.

[0064] It would also be possible for the analyzer 30 to comprise an ion mobility separator coupled to a mass analyzer, for example, where a mass analyzer is provided at the end of the ion mobility portion of the ion path. In these embodiments, any suitable type of mass analyzer can be provided, such as a time-of-flight mass analyzer or an electrostatic ion trap mass analyzer, such as an electrostatic orbital trap, and in particular an orbital trap TM-FT mass analyzer as manufactured by Thermo Fisher Scientific.

[0065] It should be noted that Fig.Figure 1 is merely schematic and the analyzer can include any number of one or more additional components, and does so in embodiments. For example, in some embodiments, the analyzer includes a collision or reaction cell for fragmenting or reacting ions, and the ions analyzed by the analyzer 30 can be fragments or productions generated by fragmenting or reacting parent ions produced by the ion source 10.

[0066] As in Fig. As shown in Figure 1, the device is controlled by a control unit 50, such as a suitably programmed computer, which controls the operation of various components of the device, including the analyzer 30. The control unit 50 can also receive and process data from various components, including the detector(s) according to the embodiments described herein.

[0067] According to various embodiments, the analyzer 30 is a cyclic analyzer. Thus, the ion path within the analyzer 30 consists of at least a first part and a second cyclic part, wherein the ion path is configured such that ions moving along the ion path make only a single pass through the first part and make one or more (e.g., multiple) passes through the second cyclic part before being detected. This is schematically illustrated by Fig. 2 illustrated.

[0068] As in Fig. As shown in Figure 2, the analyzer 30 includes an ion path 32 provided between an ion injector 31 and an ion detector 33. The ion injector 31 is configured to inject ions into the ion path 32, whereupon ions move along the ion path 32 and are detected by the detector 33, which is located at the end of the ion path 32. As shown in Figure 2, the analyzer 30 includes an ion path 32 which is provided between an ion injector 31 and an ion detector 33. The ion injector 31 is configured to inject ions into the ion path 32, whereupon the ions move along the ion path 32 and are detected by the detector 33, which is located at the end of the ion path 32. Fig.As shown in Figure 2, the ion path 32 consists of a first segment 32a, a second cyclic segment 32b, and a third segment 32c. Ions moving along the ion path 32 between the ion injector 31 and the ion detector 33 complete only a single pass through the first segment 32a, followed by one or more (e.g., multiple) passes through the second cyclic segment 32b, followed by only a single pass through the third segment 32c. The ion path 32 can include any number of additional segments. It would also be possible for the ion path to include only one of the first segment 32a and one of the third segment 32c.

[0069] It is understood that cyclic analyzers advantageously allow the length of the ion path 32, which ions take within the analyzer 30 (between the injector 31 and the detector 33), to be increased, thereby increasing the resolution of the analyzer 30.

[0070] The cyclic analyzer 30 can comprise any suitable cyclic ion analyzer with an ion path 32 configured to allow ions to make multiple passes through a cyclic segment 32b of the ion path before being detected. For example, the analyzer 30 can be a cyclic time-of-flight (ToF) mass analyzer, a cyclic ion mobility analyzer, or a cyclic ion mobility separator coupled to a mass analyzer. Fig. Figures 3-5 illustrate various exemplary embodiments of the cyclic analyzer 30.

[0071] Fig. Figure 3 schematically illustrates a detail of a closed multireflection ion trap time of a flight mass analyzer according to a first exemplary embodiment of the analyzer 30.

[0072] As in Fig.As shown in Figure 3, the analyzer comprises a pair of ion mirrors 34, 35 facing each other, which together form an ion trap. The ion mirrors 34, 35 are configured such that ions trapped in the ion trap oscillate between the ion mirrors 34, 35 on an infinitely extended (cyclic) ion path 32b until they are released. Ions can be introduced into the ion trap from an ion source (injector) 31 and finally detected by an ion detector 33. In the Fig. In the embodiment shown in Figure 3, ion access and ion extraction into the ion trap are controlled by applying suitable voltage(s) to a deflector 36 arranged in the region between the mirrors 34, 35. Alternatively, ion access and extraction can be achieved by making one or both of the ion mirrors 34, 35 switchable between a capture mode and a transmissive mode.

[0073] In the Fig.In the embodiment shown in Figure 3, the ion path 32 is configured such that ions make a single pass through a first segment 32a of the ion path (between the injector 31 and the deflector 36), then several passes through a second cyclic segment 32b of the ion path (between the ion mirrors 34, 35), and then a single pass through a third segment 32c of the ion path (between the deflector 36 and the detector 33).

[0074] With this type of cyclic analyzer, the ion flight time can be many milliseconds long, so the resolution can typically reach > 100,000 or even > 500,000. However, the space charge within the limited volume can impair the analyzer performance due to strong coalescence effects.

[0075] Fig. 4 and Fig.Figure 5 illustrates further exemplary embodiments of the analyzer 30 in detail and schematically. In these embodiments, the analyzer 30 is a multi-reflection time-of-flight (MR-ToF) mass analyzer that can be operated in a so-called multi-progression “zoom” operating mode.

[0076] As in the Fig. 4 and Fig. As shown in Figure 5, the multiple reflection time-of-flight analyzer 30 includes a pair of ion mirrors 34, 35, which are spaced apart from each other in a first direction X and face each other. The ion mirrors 34, 35 are extended along an orthogonal drift direction Y between a first end and a second end.

[0077] At one end (the first end) of the analyzer, an ion source (injector) 31 is arranged, which may be in the form of an ion trap. The ion source 31 can be arranged and configured to receive ions from the ion transfer stage(s) 20. Ions can be accumulated in the ion source 31 before being injected into the space between the ion mirrors 34, 35. As shown in the Fig. 4 and Fig. As shown in Figure 5, ions from the ion source 31 can be injected with a relatively small injection angle or a relatively small drift direction velocity, thereby generating a zigzag ion path with different oscillations spatially separated between the mirrors 34, 35. In comparison to the analyzer of Fig. 3. This has the effect of reducing the space charge effects within the analyzer.

[0078] One or more lenses and / or deflectors can be arranged along the ion path between the ion source 31 and the ion mirror 35, which the ions first encounter. For example, as in the Fig. 4 and Fig. Figure 5 shows a first out-of-plane lens 37, an injection deflector 38, and a second out-of-plane lens 39 arranged along the ion path between the ion source 31 and the ion mirror 35 first encountered by the ions. Other arrangements are possible. In general, the one or more lenses and / or deflectors can be configured to appropriately condition, focus, and / or deflect the ion beam, i.e., to cause it to follow the desired path through the analyzer.

[0079] The analyzer also includes another deflector 36, which is arranged along the ion path between the ion mirrors 34, 35. As shown in the Fig. 4 and Fig.As shown in Figure 5, the deflector 36 can be arranged approximately equidistantly between the ion mirrors 34, 35 along the ion path after its first ion mirror reflection (in ion mirror 35) and before its second ion mirror reflection (in the other ion mirror 34).

[0080] The analyzer also includes a detector 33. The detector 33 can be any suitable ion detector configured to detect ions and to record, for example, an intensity and arrival time assigned to the arrival of the ion(s) at the detector. Suitable detectors include, for example, one or more conversion dynodes, optionally followed by one or more electron multipliers, and the like.

[0081] In its “normal” operating mode, ions from the ion source 31 are injected into the space between the ion mirrors 34, 35, causing the ions to assume a zigzag ion path with multiple reflections between the ion mirrors 34, 35 in the X direction, while: (a) they drift along the Y direction from the deflector 36 towards the opposite (second) end of the ion mirrors 34, 35, (b) the drift direction reverses near the second end of the ion mirrors 34, 35, and then (c) drift back along the Y direction towards the deflector 36. The ions can then be directed from the deflector 36 to the detector 33.

[0082] In the analyzer of Fig.4. Both ion mirrors 34, 35 are inclined with respect to the X and / or drift-Y direction. It would be possible, however, for only one of the ion mirrors 34, 35 to be inclined, and, for example, for the other ion mirror 34, 35 to be arranged parallel to the drift-Y direction. In general, the ion mirrors are spaced at a non-constant distance from each other in the X direction along their lengths in the drift direction Y. An electric field, resulting from the non-constant distance between the two mirrors, opposes the drift velocity of ions towards the second end of the ion mirrors. This electric field causes the ions to reverse their drift velocity near the second end of the ion mirrors and drift back towards the deflector along the drift direction.

[0083] The in Fig.The analyzer shown in Figure 4 further includes a pair of corrective strip electrodes 40. Ions moving down the drift length are slightly deflected with each pass through the mirrors 34, 35, and the additional strip electrodes 40 are used to correct the time-of-flight error caused by the varying distance between the mirrors. For example, the strip electrodes 40 can be electrically biased such that the period of ion oscillation between the mirrors is essentially constant along the entire drift length (despite the non-constant distance between the two mirrors). The ions are then reflected back into the drift space and focused at the detector 33.

[0084] Further details of the multi-reflection time-of-flight mass analyzer of the inclined mirror type by Fig. 4 are described in US Patent No. 9,136,101, the contents of which are incorporated herein by reference.

[0085] In the analyzer of Fig. In 5, the ion mirrors 34 and 35 are parallel to each other. To cause the ions to reverse their drift direction velocity near the second end of the ion mirrors and drift back along the drift direction towards the deflector, the analyzer includes a second deflector 41 at the second end of the ion mirrors 34 and 35.

[0086] As in Fig.As shown in Figure 5, in this embodiment a lens can be enclosed in the injection deflector 38 and / or in the deflector 36. This allows the ion beam to propagate a short distance into the analyzer before encountering a long focal length lens, causing the ion beam to focus along its length. The lens can be an elliptical drift-focusing (converging) lens mounted within the deflector 36. The second deflector 41, which can also enclose a lens, is used to reverse the beam direction while maintaining control of the focus characteristics.

[0087] Further details of the single-lens multi-flexion time-of-flight mass analyzer from Fig. 5 are described in UK patent no. GB ​​2,580,089, the contents of which are hereby incorporated by reference.

[0088] In the Fig. 4 and Fig.In the five analyzers shown, the ion beam can be scattered relatively widely (in the drift direction Y) for most of its trajectory. This contrasts, for example, with multiple reflection time-of-flight (ToF) mass analyzers, which use a set of periodic lenses to focus the ion beam along its entire trajectory, as described, for example, in the article by A. Verenchikov et al., Journal of Applied Solution Chemistry and Modelling, 2017, 6, 1-22. A significant advantage of allowing the ion beam to generally spread out for most of its trajectory is the reduction of space charge effects, which can be a considerable problem for time-of-flight analyzers. Nevertheless, the embodiments described herein are also applicable to other MR-ToF analyzer designs, such as the Verenchikov-type MR-ToF analyzer.

[0089] In the in the Fig. 4 and Fig.In the embodiments shown in Figure 5, the fact that the ion beam is relatively wide in the drift dimension Y means that the deflector 36 should be able to accommodate such a wide beam without clipping or uneven deflection. A suitable deflector design is a trapezoidal or prismatic deflector. Thus, the deflector 36 can comprise a trapezoidal or prismatic electrode positioned above the ion beam and another trapezoidal or prismatic electrode positioned below the ion beam. The electrodes can be angled with respect to the ion beam. Ions can be exposed to a relatively strong electric field at the edges of the angled electrodes, which induces deflection.The electrodes can be located outside the plane of deflection, which allows them to easily capture a wide ion beam (at least compared to conventional deflection plates that would be located on both sides of the beam).

[0090] In embodiments, the multi-reflection time-of-flight (MR-ToF) mass analyzer is operated in a multi-pass “zoom” mode. Ions are caused to complete multiple cycles within the analyzer in the drift direction Y. Increasing the number of cycles N increases the length of the ion path taken within the analyzer (between the injector and the detector), thereby increasing the analyzer's resolution. In the Verenchikov analyzer, this can be achieved by applying a voltage to an entrance lens. For the [unclear] Fig. 4 and Fig.In the 5 analyzers shown, the deflector 36 on the front of the analyzer, which is normally used to reduce the injection angle and / or to optimize the number (K) of oscillations within a single drift pass, can (also) be used to reverse the drift direction velocity of the ions in such a way that the ions are caused to complete another cycle through the analyzer.

[0091] Thus, in a multi-path "zoom" operating mode, ions are caused to complete multiple (N) cycles within the analyzer, with the ions drifting in the Y direction from the deflector 36 (or the entrance lens) towards the opposite (second) end of the ion mirrors 34, 35 and then back to the deflector 36 (or the entrance lens) in each cycle. In each cycle, the ions also complete multiple (K) reflections between the ion mirrors in the X direction. Therefore, in each cycle, the ions follow a zigzag ion path 32b through the space between the ion mirrors 34, 35.

[0092] In the Fig. 4 and Fig.In the five analyzers shown, an initial cycle can be initiated by injecting ions from the injector 31 into the space between the ion mirrors 34 and 35. The ions can be reflected in one of the ion mirrors 35 and then move towards the deflector 36. No voltage can be applied to the deflector 36 (or a suitable (e.g., relatively small) voltage can be applied to the deflector), causing the ions to exit the deflector 36 in a direction opposite the second end of the ion mirrors.In the presence of the deflector 36, the ions assume a zigzag ion path 32b with multiple (K) reflections between the ion mirrors 34, 35 in the direction X, while: (a) they drift along the drift direction Y from the deflector 36 towards the second end of the ion mirrors, (b) reverse the drift direction velocity near the second end of the ion mirrors, and (c) drift back along the drift direction Y towards the deflector 36.

[0093] After the ions have completed this initial cycle, each subsequent cycle is initiated by using the deflector 36 to reverse the drift velocity of the ions (near the first end of the ion mirrors). This can be achieved by applying a suitable voltage to the deflector 36, causing the ions to leave the deflector 36 with a drift velocity opposite to the drift velocity with which the ions originally entered the deflector 36.

[0094] After the ions have completed the desired (multiple) number (N) of cycles within the analyzer, they are allowed to move from the deflector 36 to the detector 33 for detection. This can be achieved by removing the voltage from the deflector 36 (or by applying a suitable voltage to the deflector) so that the ions are caused to leave the deflector 36 in the direction of the detector 33. The ions may be reflected in one (or the other) of the ion mirrors 34 before moving towards (and being detected by) the detector 33.

[0095] In the in the Fig. 4 and Fig.In the embodiments shown in Figure 5, the ion path is configured such that ions make a single pass through a first segment 32a of the ion path (between the injector 31 and the deflector 36 via an ion mirror 35), then several passes through a second cyclic segment 32b of the ion path (between the deflector 36 and the deflector 36 via the opposite (second) end of the ion mirrors 34, 35), and then a single pass through a third segment 32c of the ion path (between the deflector 36 and the detector 33 via the other ion mirror 34).

[0096] Although the Fig. Figures 3-5 illustrate exemplary embodiments of the cyclic analyzer 30; it is understood that various alternative embodiments are possible. For example, the analyzer 30 can instead be a cyclic ion mobility analyzer or a cyclic ion mobility separator coupled with a mass analyzer.

[0097] In these embodiments, the cyclic ion mobility analyzer or cyclic ion mobility separator can include a closed-loop ion separator, such as that described in GB patent application no. GB ​​2,562,690. Ions can be caused to separate around the ion mobility separator according to their ion mobility over a fixed integer number of cycles. A gate can be provided that can be closed to allow multiple passes. The gate can be opened to allow ions to exit the ion mobility separator after they have completed one or more cycles. The use of a cyclic ion mobility separator can provide a higher degree of separation and thus a higher ion mobility resolution.

[0098] In these embodiments, the ion path can be configured such that ions make a single pass through a first segment of the ion path (before the closed-loop ion separator), then several passes through a second cyclic segment of the ion path (within the closed-loop ion separator), and then a single pass through a third segment of the ion path (after the closed-loop ion separator).

[0099] A common advantage among the different types of cyclic analyzers (in which ions are caused to make multiple N repeated cycles along an ion path within the analyzer) is that increasing the number N of cycles increases the length of the ion path that ions take within the analyzer, thereby increasing the resolution of the analyzer.

[0100] A common problem, however, is that during several cycles N through the analyzer, faster-moving (e.g., lighter) ions can catch up with (e.g., overtake) slower-moving (e.g., heavier) ions. This complicates the resulting spectra and can make it difficult to accurately determine the desired physicochemical property (e.g., m / z or ion mobility) of all detected ions, as the number of cycles N recorded by each ion peak in a spectrum becomes ambiguous.

[0101] Thus, embodiments provide methods for disambiguating a spectrum generated by a cyclic ion analyzer. By comparing two sets of ion data obtained under different analyzer settings, the number N of passes through the cyclic segment 32b of the ion path 32 taken by ions contributing to an ion peak can be determined, thereby enabling the physicochemical properties of these ions to be uniquely determined and assigned to the ion peak.

[0102] Although parts of the following discussion relate to the MR-ToF analyzers of the Fig. 4 and Fig. As described in section 5, the person skilled in the art understands that similar considerations can be applied to the various other types of cyclic analyzers, such as cyclic ToF analyzers and cyclic ion mobility separators.

[0103] The one in the Fig.4 and Fig. The ion path shown in Figure 5 is followed, for example, by all ions with a mass-to-charge ratio in the range of (m / z)1 to (m / z)2. The deflector 36 must be switched from mode 1 (deflection from source 31 to the loop) to mode 2 (deflection from the loop back to the loop) and finally to mode 3 (deflection from the loop to the detector 33). The switching times are each denoted as t 12 and t 23 The zero time is defined as the time of injection.

[0104] The first switch between modes 1 and 2 should only occur when the heaviest ion (m / z)2 first passes through deflector 36, and at the latest when the lightest ion (m / z)1 generates a0 + K oscillations, where K is the number of oscillations per loop (between successive passes of deflector 36) and a0 represents a segment of an oscillation prior to the ion source 31 and the first pass of deflector 36. Otherwise, the lightest ions will not be properly adjusted to the next loop. This results in the double inequality: a0T2≤t12≤(a0+K)T1 where T1 and T2 are the oscillation times for the lightest and heaviest ions, respectively. In the embodiments of the Fig. 4 and Fig. 5 is a0 ≈ 1 / 2.

[0105] The second switch from mode 2 to mode 3 should only occur when the heaviest ion generates a0 + (N - 1)K oscillations, where N is the intended number of loops. Otherwise, the heaviest ion will leave the loop before all loops are completed. Conversely, the second switch should only occur when the lightest ion generates a0 + NK oscillations; otherwise, this ion will remain undesirably in the analyzer for the next loop. This double inequality states: (a0+NK−K)T2≤t23≤(a0+NK)T1

[0106] Both equations (a) and (b) establish upper limits for the ratio of T2 and T1, at which for a pair t 12 and t 23 is present; and the limit of (b) is stronger (lower) than that of (a) for every N>1; T2T1≤(T2T1)max=a0+NKa0+NK−K

[0107] Since the flight time is proportional to the square root of m / z, this inequality is directly applied to the maximum unique mass range (UMR) as: (m / z)2(m / z)1≤UMR=(a0+NKa0+NK−K)2

[0108] To achieve the full UMR, the switching time t must be 23 be: t23=(a0+NK)T1=(a0+NK−K)T2

[0109] The initial switching time allows for some flexibility. For example, it can be assumed that its lowest possible value t 12 = a0T2 can be adopted, which enables electronic ripples before the lightest ion reaches the deflector at the next time.

[0110] Table 1 shows simulations of a mass analyzer with an effective oscillation spacing of 1.25 m and twenty oscillations per loop. The resolution is calculated in terms of the peak full-width half-maximum. The drop in the m / z range is rather pronounced as the number of loops increases. Table 1 Number of loops FWHM / ns Resolution, K Unambiguous mass range No zoom 1,7 125 Limited source > 15x 2x 6,5 65 3,9x 3x 2,2 280 2,23x 4x 7,0 120 1,77x 5x 3,0 340 1,56x

[0111] The m / z range of ions entering analyzer 30 could be limited, for example, by using the switchable deflector, the mass filter (e.g., quadrupole mass filter), or otherwise, to approximately match their m / z range to the UMR of the zoom method and thereby eliminate the ambiguity in the m / z assignment. However, this is rather wasteful for ion transfer, and more efficient methods may be preferred to maintain sensitivity.

[0112] Accordingly, the disambiguation of complex spectra according to embodiments is generally preferred, wherein the correct number of drift reflections is assigned to individual ion peaks and from there the exact m / z for each ion peak is determined.

[0113] One possible approach to disambiguation would be to directly assign the correct number of cycles N to each ion peak based on that peak's resolution. From the resolution shifts observed in Table 1, this initially appears to be a rather appealing approach. Similarly, m / z-dependent properties (such as a single ion detector response, distances between different charge states, isotopes, or common fragmentation routes, such as loss of ammonia or water, etc.) could be used to pre-assign an approximate m / z to individual ion peaks and thus the number of cycles. A comparison with an acquisition scan without zoom mode is also possible, particularly for drift-separated MR-ToF analyzers, where even the acquisition scan is very high-resolution and mass-accurate.In practice, however, these approaches are significantly complicated by space charge effects for intense ion peaks and statistical problems for small ion peaks.

[0114] According to embodiments, the disambiguation of cyclic analyzer spectra (such as ToF mass analyzer spectra or ion mobility analyzer spectra) is performed by varying the flight time separately on the ion path segments that are included (32b) or not included (32a, 32c) in the repeating loop.

[0115] As used here, the "effective ion path" is defined as the flight times of the ions under a nominal acceleration voltage. The effective ion path can be varied either by directly changing the ion path length or by changing the voltage(s), which alters the flight time.

[0116] Referring again to Fig.2 The effective ion pathway along the entire ion pathway 32 consists of three parts: L=L0+LmN+L1 where L0 and L1 correspond to the non-repeated segments 32a, 32c outside the loop (e.g., in the Fig. 3-5, which each correspond to path 32a between the injector 31 and the switchable deflector 36, and to path 32c from this deflector 36 to the ion detector 33). Path L m is the effective length of segment 32b, which is repeated N times in the loop.

[0117] If the effective ion pathways L0, L m and L1 is modified proportionally, the measured flight time changes in the same proportion for each ion, regardless of how many loops N the ion makes. Changing L m by ΔL m , while L0+L1 remains unchanged, the flight time is modified by Δt in the ratio: Δtt=ΔLmNL0+LmN+L1

[0118] What is solvable for N as: N=L0+L1Lm(ΔLmLmtΔt−1)−1

[0119] In the other case, where the sum L0+L1 is changed by ΔL0 and L m If the relative flight time difference remains unchanged, it is: Δtt=ΔL0L0+LmN+L1 which yields another formula for N: N=L0+L1Lm(ΔL0L0+L1tΔt−1)

[0120] Therefore, in both cases, the number of loops N can be determined based on the measured time shift Δt for an ion peak detected at moment t after injection. With the known number of oscillations N, the flight time t can be converted into the mass-to-charge ratio (or ion mobility) using a standard conversion.

[0121] Thus, in embodiments, a first set of ion data is obtained when operating the analyzer in a first operating mode, and a second set of ion data is obtained when operating the analyzer in a second, different operating mode. The first and second sets of ion data can be obtained by analyzing ions originating from the same sample (e.g., by analyzing ions generated from adjacent regions of a sample and / or by analyzing ions generated from a sample at close (adjacent) time points), such that ion peaks corresponding to some, most, or all (significant) ion peaks in the first set of ion data appear in the second set of ion data.

[0122] The first and second operating modes differ with respect to at least one parameter of the analyzer 30. Specifically, the ion path 32 of the analyzer is divided into two segments: one with a trajectory 32b influenced by the number N of passes, and at least one 32, 32c that remains unaffected. A parameter change is applied between the two operating modes, which alters the drift time over one of these segments disproportionately compared to the other. Thus, the proportional change in the drift time depends on how many passes N an ion makes through the cyclic segment 32b. In embodiments, either the effective ion path in the loop L m The effective ion path outside the loop L0 + L1 is changed between the two operating modes.

[0123] An effective ion path can be modified either by directly changing the ion path length or by changing voltage(s) that alter the flight time. Thus, in the first operating mode, (i) a first electrical potential is provided along the first segment 32a, 32c of the ion path, (ii) a second electrical potential is provided along the cyclic segment 32b of the ion path, (iii) the first segment of the ion path 32a, 32c has a first path length, and (iv) the cyclic segment of the ion path 32b has a second path length. In the second operating mode, at least one of: (i) the first electrical potential, (ii) the second electrical potential, (iii) the first path length, and (iv) the second path length is modified relative to the first operating mode, e.g., such that one of the effective ion path in loop L mand the effective ion path outside the loop L0 + L1 is changed relative to the first operating mode.

[0124] This parameter change induces a time shift Δt for each ion peak between the two sets of ion data. The first set of ion data is then compared with the second set to identify corresponding (matching) ion peaks. For each identified ion peak pair of interest, the time shift Δt for that peak pair between the two data sets is measured. The number of loops N for each peak is then estimated from the measured time shift Δt (e.g., using the equations described above), and N is used to calculate the mass-to-charge ratio (or other physicochemical property) of the ions corresponding to the ion peak.

[0125] Various exemplary embodiments for changing either the effective ion path in loop L m or the effective ion path outside the loop L0 + L1 are described below. However, it is understood that various alternatives are possible, e.g., depending on the specific design of the cyclic ion analyzer 30.

[0126] In a first embodiment, the path length of the cyclic segment 32b of the ion path is changed between the first and the second operating mode.

[0127] In the multiple reflection analyzer of the Fig. 4 and Fig.5. The effective length of the loop can be changed by altering the number of reflections K between the ion mirrors 34, 35 made by ions per cycle, i.e., by changing the number of reflections K in the X-direction made by the ions as they (a) drift along the Y-direction from the deflector 36 to the second end of the ion mirrors, (b) reverse their drift velocity near the second end of the ion mirrors, and (c) drift back along the Y-direction to the deflector 36. This can be achieved by appropriately changing the voltage applied to the deflector 36 between the two operating modes, i.e., such that ions exit the deflector 36 at slightly different angles between the two operating modes. Suitable voltage shifts are on the order of a few volts or a few tens of volts. In the case of the tilted-mirror analyzer of Fig.4. The change in K can also or instead be achieved by adjusting the voltages applied to the strip electrode 40.

[0128] In embodiments, the number of reflections K between the ion mirrors 34, 35 is changed by ±1 between the two operating modes, and corresponding time shifts Δt are measured for individual ion peaks. Since the number of iterations N is low (usually less than 6), the time shifts Δt can be measured with moderate precision, and the exact number of iterations N can be determined by rounding (Eq. Na) to the nearest integer.

[0129] The effective length of the loop L m is proportional to K, which leads to a relative change ΔL m / L m The formula = 1 / K results when the number of oscillations K is increased by one. In this case, the formula (Eq. Na) is: N=a0+a1K(tKΔt−1)−1=a0+a1tΔt−K where a0 is the fraction of an oscillation between injection and the first pass through the switchable deflector 36, and a1 is the fraction of an oscillation after leaving the loop and before hitting the detector 33. In the Fig. 4 and Fig. In the analyzer shown, these fractions are approximately 0.5 and 0.45 respectively.

[0130] Table 2 shows an example of this disambiguation algorithm applied to a ToF spectrum of the Flexmix calibration mixture. The low m / z ions are tuned to reach the detector after N = 2 loops, with each loop containing K1 = 21 oscillations. Corresponding flight times are shown in the first column. However, some higher m / z ions (predominantly Ultramark ions) make an additional loop, N = 3, due to their lower propagation velocities. To assign each peak the correct number of loops, the system was switched to a mode with K2 = 22 oscillations in each loop, and corresponding flight times were recorded for each of the peaks. These are shown in the second column. The formula (Eq. N.dk) was used to estimate the values ​​of N* from the flight-time differences, and these values ​​were rounded to the nearest integer.Finally, the m / z ratios were calculated using the following formula: . mz=(1+cN)×2U0×(ToFL0+L1+NLm)2 where U0 is the accelerating voltage and c N << 1 is a calibration coefficient that was defined a priori experimentally for each number of loops N = 2 and 3. Table 2 Measured ToF t, µs t / Δt N* N m / z, Th K = 21 K=22 1938,553 1851,682 21,315 3 3 393,224318 1941,024 1854,042 21,315 3,001 3 394,227718 1963,009 1875,042 21,315 3,000 3 403,208721 1992,4 1903,708 21,464 2,037 2 922,008848 2197,923 2100,044 21,456 2,077 2 1121,99485 2238,375 2138,068 21,315 3,0004 3 524,264857 2240,516 2140,113 21,315 3,0013 3 525,268358 2293,732 2191,626 21,464 2,0380 2 1221,9884 2294,673 2192,525 21,464 2,0382 2 1222,99131 2385,733 2279,534 21,465 2,0356 2 1321,9844 2386,639 2280,397 21,464 2,0384 2 1322,98508 2438,161 2328,901 21,315 3,0007 3 622,027987

[0131] In some embodiments, the fraction of N* arises from limited calibration accuracy. Nevertheless, the assignment of the integer N to the rounded value N* is unambiguous. The fewer loops that need to be distinguished from one another, the more reliable the disambiguation method becomes.

[0132] One advantage of the "zoom" mode described above in the analyzer of the Fig. 4 or Fig. 5 consists in the fact that the analyzer has a relatively long length L mper loop (a few tens of meters) and has a relatively small number of loops (N = 1...5). For example, a 15x m / z range provided by ion source 10, with the zoom mode configured to give the highest m / z ions two drift passes (N = 2), means that the lowest m / z ions make four passes (N = 4), so the ambiguity is only whether ions make N = 2, 3, or 4 passes.

[0133] Fig. Figure 6 is a flowchart illustrating a disambiguation procedure according to these embodiments. As in Fig.As shown in Figure 6, the procedure involves acquiring first and second mass spectra by operating the analyzer with different numbers of ion oscillations (K1 and K2) per cycle (step 60). Corresponding pairs of ion peaks in the two spectra are then identified (step 61), and the number N of iterations of the cyclic segment of the ion path taken by the ions assigned to each pair of corresponding ion peaks is estimated (step 62). Finally, N is used to calculate the true m / z of the ions (step 63).

[0134] Another approach to determining the number of loops from the flight times at different numbers of oscillations K per loop is to compute a list of possible mass-to-charge ratios for each ion peak (from Eq. mz) under different assumptions about the possible number of loops N. This yields several possible values ​​m / z(N,K), where N is a candidate number of loops and K = K1, K2. Only for the correct value of N are the candidate values ​​m / z(N,K1) and m / z(N,K2) (approximately) the same (e.g., within a narrow tolerance, such as 10 ppm), while incorrect assumptions about N lead to substantially different values.

[0135] As illustrated in Tables 3A and 3B, only one candidate N (correspondingly 3 and 2) yields immediate candidates for m / z for different values ​​of K. These candidate values ​​are accepted as correct, and all other m / z calculated with different assumptions about the number of loops are rejected as incorrect. Table 3A Exactly m / z = 524.26 K = 21 K = 22 Measured ToF, µs 2138,068 2238,375 Assumed number of loops, N Candidates for m / z, Th Δm / z, Th 1 4451,092 4462,579 11,487 2 1162,336 1163,102 0,766 3 (correct) 524,2646 524,2647 0,0001 4 297,0923 296,9936 -0,0987 5 190,9889 190,8871 -0,1018 Table 3B Exactly m / z = 922.01 K = 21 K = 22 Measured ToF, µs 1903,708 1992,400 Assumed number of loops, N Candidates for m / z, Th Δm / z, Th 1 3530,773 3537,682 6,909 2 (correct) 922,0088 922,0419 0,0331 3 415,8663 415,6076 -0,2587 4 235,6648 235,4398 -0,225 5 151,4996 151,3246 -0,175 Table 3

[0136] Fig. Figure 7 is a flowchart illustrating a disambiguation procedure according to these embodiments. As in Fig.As shown in Figure 7, the procedure involves acquiring first and second mass spectra by operating the analyzer with different numbers of ion oscillations (K and K+1) per cycle (step 70). Pairs of corresponding ion peaks are identified (step 71). With respect to each candidate value of N (step 72), a candidate m / z value is calculated for each peak (step 73). This generates a list of possible m / z values ​​for each ion peak. Matching pairs of ion peaks between the two spectra are then identified to determine the accuracy N for each pair of corresponding ion peaks (step 74). Finally, the unique m / z of each matching pair of ion peaks is determined and assigned to each ion peak (step 75).

[0137] In some embodiments, due to the possibility that some peaks may be lost due to the shift of K, e.g., due to ions present within the deflector 36 during voltage switching, it may be advantageous to use more than two values ​​of K, at the cost of the overall acquisition speed. The disappearance of ion peaks in the spectrum can also, or alternatively, be used to provide disambiguation information, since the m / z values ​​that are lost can be calculated based on the deflection magnitude, switching speed / times, and so on.

[0138] In general, embodiments may include analyzing ions in a third operating mode (by determining drift times of ions along the ion path) to obtain a third set of ion data, wherein in the third operating mode at least one of: (i) the first electrical potential, (ii) the second electrical potential, (iii) the first path length, and (iv) the second path length is modified with respect to the first and / or second operating mode, whereby the third set of ion data is compared with the first and / or second set of ion data, and based on the comparison, the number N of passes of the second part of the ion path taken by ions assigned to the corresponding ion peaks is determined.

[0139] In a second exemplary embodiment, disambiguation is achieved by comparing the flight times between two spectra, wherein the non-reflective segment of the trajectory has been modified by changing an electrical potential of the non-reflective segment of the trajectory.

[0140] Fig. Figure 8 schematically shows a simplified (e.g., MR-ToF) analyzer layout that includes a short section of the flight tube 80 upstream of the detector 33. The flight tube 80 could easily be integrated into a detector array, e.g., as part of a so-called post-accelerator, which comprises an array of suitably biased electrodes configured to accelerate ions onto a conversion dynode. The flight tube 80 allows the potential to be varied to shift the flight time of ions in the non-reflective segment of the ion path 32c upstream of the detector 33. Fig.Figure 8 also shows a division of the ion flight path 32 into several sections, the injection L0, the reflecting part L m and the extraction to the detector L1 with the built-in flight tube L t .

[0141] The time-of-flight shift caused by a voltage v applied to flight tube 70 is proportional to √(m / z) and does not depend on the number of cycles N. Measuring the time-of-flight spectrum with two (or more) values ​​of v allows for an independent evaluation of m / z. Therefore, the number of cycles N can be assigned to each peak. From the perplexed time-of-flight spectrum and the number of cycles assigned to each affected ion peak, accurate values ​​of m / z can then be determined.

[0142] In the schematic diagram of Fig. 8. An ion with a mass-to-charge ratio µ=m / z reaches the second mirror at the following time: tn(μ)=μ2ε0[L0+(2n+1)Lm] where ε0 is the accelerating voltage and L0 and L m These are effective lengths. The second mirror is to switch abruptly from a reflection mode to a transmission mode at time T2. The number of reflections completed in the second mirror before T2 is: N(μ)=〚12Lm(T22ε0μ−L0+Lm)〛 where the double brackets [[...]] denote the integer part. The time at which the ion is detected is: tD(μ)=μ2ε0(L0+(2N(μ)+1)Lm+L1)

[0143] Since the number of cycles N decreases stepwise with the mass-to-charge ratio µ, the function t D (µ) is not monotonic. This means that a ToF spectrum t D (µ) is ambiguous and a peak that occurs at t D located, can correspond to a number of different mass-to-charge ratios µ.

[0144] Intervals of µ corresponding to a specific integer N(µ) are called unique mass intervals. For N cycles, the corresponding unique interval ranges of M N+1 to M N , where: MN=T22ε0μ−L0+Lm=2T22ε0((2N−1)Lm+L0)2

[0145] The unambiguous mass range is therefore: UMRN=MNMN+1=(2N+L0 / Lm+12N+L0 / Lm−1)2

[0146] Consider the short flight tube 80 with length Lt, located between the second mirror and the detector 33 and biased with a voltage v << ε0. When the voltage is applied, the peak appears shifted by: ΔtD(μ)=μ2(ε0−v)Lt−μ2ε0Lt=μ2ε0Lt(11−v / ε0−1)≅v2ε0μ2ε0Lt

[0147] Since v << ε0, the peak width is not significantly broadened and the center-of-mass shift is measurable. This allows a rough estimate of the reverse ion velocity and the mass-to-charge ratio µ as: μ*2ε0≅(ε0ε0−v−1)−1ΔtDLt≅2ε0v(vε0)−1ΔtDLt, μ*≅(2ε0)3Lt3(ΔtDv)2

[0148] The precision is low, but sufficient to determine the number of cycles N for a given peak. For this purpose, the estimated value µ* is substituted into the formula (equation Nµ) N(µ*) = [[N*]], where: N*≅12Lm(v2ε0T2ΔtDLt−L0+Lm)

[0149] The exact µ is then determined as: μ=2ε0(tDL0+(2〚N*〛+1)Lm+L1)2 where N* is rounded down.

[0150] Thus, in these embodiments, a first set of ion data is obtained when operating the analyzer in a first operating mode, and a second set of ion data is obtained when operating the analyzer in a second operating mode, wherein in the second operating mode the electrical potential along the first (and / or third) segment 32a, 32c of the ion path is changed relative to the first operating mode. This change induces a time shift Δt for each ion peak between the two sets of ion data, which are used to estimate the number of cycles N for each peak and, accordingly, the mass-to-charge ratio (or another physicochemical property), e.g., in the manner described above.

[0151] In the through Fig. In the 8 illustrated embodiments, it would instead be possible to position the flight tube 80 in the ion path 32a between the source 31 and the first mirror.

[0152] Another embodiment consists of modifying the acceleration field provided by the ion injector 31 to accelerate ions along the ion path. If the ion injector is an ion trap, this can include modifying the extraction field provided within the ion trap to accelerate ions from the ion trap along the ion path (e.g., if, in this embodiment, at least a portion of the first segment 32a of the ion path can be considered to lie within the ion trap). Suitable extraction fields are on the order of a few hundred V / mm, and suitable extraction field shifts between the first and second operating modes are on the order of several tens of V / mm.

[0153] It should also be noted that if the voltage applied to the flight tube 80 is relatively small, the number of cycles N for the vast majority of ion peaks, with the exception of ion peaks located near M, will be relatively small. N will be maintained.

[0154] These embodiments can also be easily implemented in cyclic ion mobility spectrometry (which measures the time of flight through a gas-filled drift path). For example, UK patent application GB 2,562,690 describes a device combining a cyclic ion mobility analyzer and a short linear drift tube, which could be easily adapted to shift the overall drift times in a similar manner to that described above.

[0155] Although the foregoing exemplary embodiments have been described with respect to changing (between the first and the second operating mode) either (i) the electrical potential along the non-cyclic segment 32a, 32c of the ion path or (ii) the path length of the cyclic segment 32b of the ion path, it is understood that it would instead be possible to either (iii) change the electrical potential along the cyclic segment 32b of the ion path (e.g., by enclosing a flight tube along the cyclic segment 32b of the ion path), or (iv) change the path length of the non-cyclic segment 32a, 32c of the ion path (e.g., by controlling the number of reflections that K ions make between two ion mirrors), i.e., such that one of the effective ion path in the loop L m and the effective ion path outside the loop L0 + L1 is changed relative to the first operating mode.

[0156] A numerical example of the in Fig. The arrangement shown in section 8 was modeled using L m = 0.5 m, L0 and L1 = 0.4 m, L t = 0.3 m, T2 = 0.5 ms and ε0 = 1000 eV. A voltage shift of 10 V was applied to the flight tube 80 between the two spectra. Flight times were calculated for ions with mass-to-charge ratios ranging from 250 to 3250 in 150 m / z steps.

[0157] Fig. Figure 9 shows how different m / z ions (top field) fall into different numbers of reflections, and the resulting converged time-of-flight spectrum (left field).

[0158] Fig. 10A shows two overlapping time-of-flight spectra, which demonstrate the small shift between peaks caused by a 10 V offset applied to the L t -area is created, and Fig.Figure 10B shows the recovered mass spectrum, which is obtained by measuring the shift between peaks and assigning the number of cycles. This information is also presented in Table 4. Table 4 Number of peaks Model m / z Acquisition time, µs Shifted acquisition time*, µs N [N] Recovered m / z 0. 250,0 526,7950 526,8210 14,3360 14 250,0 1 400,0 532,1840 532,2180 11,3960 11 400,0 2 550,0 519,1600 519,2000 9,7630 9 550,0 3 700,0 526,5310 526,5760 8,6880 8 700,0 4 850,0 515,0170 515,0660 7,9120 7 850,0 5 1000,0 558,6140 558,6680 7,3180 7 1000,0 6 1150,0 523,2180 523,2760 6,8440 6 1150,0 7 1300,0 556,2960 556,3570 6,4550 6 1300,0 8 1450,0 587,5140 587,5780 6,1280 6 1450,0 9 1600,0 527,7120 527,7800 5,8480 5 1600,0 10 1750,0 551,8940 551,9650 5,6050 5 1750,0 11 1900,0 575,0610 575,1350 5,3910 5 1900,0 12 2050,0 597,3290 597,4060 5,2020 5 2050,0 13 2200,0 618,7970 618,8760 5,0320 5 2200,0 14 2350,0 531,1470 531,2290 4,8780 4 2350,0 15 2500,0 547,8370 547,9210 4,7390 4 2500,0 16 2650,0 564,0320 564,1190 4,6110 4 2650,0 17 2800,0 579,7760 579,8650 4,4940 4 2800,0 18 2950,0 595,1030 595,1950 4,3860 4 2950,0 19 3100,0 610,0450 610,1390 4,2860 4 3100,0 20 3250,0 624,6300 624,7260 4,1930 4 3250,0

[0159] This example assumes that there is no difficulty in fitting peaks before and after the shift, which can be useful for small shifts and uncongested spectra. In more complex cases, it can be advantageous to have precise calibrations for both shifted and unshifted spectra and to assign several possible m / z values ​​to each ion peak, and then to fit peaks as described above in relation to the first exemplary disambiguation procedure.

[0160] A mass spectrometer, which incorporates the analyzer design of Fig.The analyzer, which includes 4 kV, was constructed. The analyte ions m / z 524, generated from an electrospray source, were isolated by a quadrupole, collected, cooled within an extraction ion trap, and ejected into the analyzer by a 330 V / mm pulsed field, under which they are rapidly accelerated to 4 kV flight energy.

[0161] Ion scattering was controlled by a pair of lenses, and the ion direction was set by the first prism deflector 38, so that ions passed through a reflection from an ion mirror 35 to the second prism deflector 36. The second prism deflector 36 was set to -160 V to allow ions to reach the analyzer. After approximately 200 µs, this prism deflector was switched to +280 V capture mode and held there for 800 µs, sufficient for the ions to complete a second drift pass. The prism 37 was then switched back to -160 V transmission mode, and the captured ions were extracted to an electron multiplier detector 33.

[0162] Fig.Figure 11 shows the m / z-524 peaks captured when the device was operated in single-pass and zoom modes. A significantly higher resolution was observed in 3x zoom mode without substantial signal loss, although higher numbers of drift passes were required to substantially reduce transmission.

[0163] Fig. Figure 12 shows zoom-mode mass spectra of the Pierce Flexmix calibration solution, a common calibration mixture containing MRFA and Ultramark. In this example, the ion mass ranges supplied to the ToF analyzer were first isolated using a high-resolution quadrupole to remove ambiguous peaks. From the first mass, 390, an approximately 1.6 × m / z range was observed.

[0164] Fig.Figure 13 shows data from a test of the disambiguation method according to the first embodiment. Flexmix ions were injected into the trap at a much wider m / z isolation window of 390–2000 than the unambiguous m / z window of 390–625, resulting in high m / z Ultramark ions with a -1 drift pass in the mass spectrum. The number of oscillations K per drift pass was then reduced by one, and the mass calibration coefficients were recalculated. It was observed that the high m / z Ultramark peaks were shifted by -620 ppm in m / z, which facilitated their identification.

[0165] A similar experiment according to the second exemplary embodiment was carried out by varying the pulsed extraction field of the ion injector from 330 to 240 V / mm, which shifted the high m / z ions by -40 ppm.

[0166] It is evident from the foregoing embodiments that the embodiments provide a method for operating an analytical instrument, such as a time-of-flight mass spectrometer, which includes an analyzer configured to determine the time of flight of ions along a path comprising a cyclic segment and a non-cyclic segment. The cyclic segment is configured such that at least some ions complete more than one loop in it, and the non-cyclic segment is configured such that all ions complete only one loop. At least one of the cyclic and non-cyclic segments is controlled, for example, by at least one electrode with a switchable voltage which, when switched, modifies the time of flight of an ion in that segment.

[0167] The method may include determining a first set of ion flight times after completion of the cyclic and non-cyclic segments, changing a voltage on at least one of the control electrodes, and then determining a second set of ion flight times after completion of the cyclic and non-cyclic segments. The method may include determining a number of loops in the cyclic segment formed by ions of interest, based on flight time differences between the first and second sets of flight times. The method may then include determining a mass-to-charge ratio of at least one ion based on the complete trajectory, which includes the determined number of loops in the cyclic segment.

[0168] The cyclic or non-cyclic segment can be controlled by a voltage that, when applied, modifies the ion velocity in at least one section of the path, which in turn modifies the flight time in the cyclic or non-cyclic segment. The cyclic segment can be controlled by a voltage that modifies the ion flight length within that segment. The ions can perform more than one oscillation within a single loop in the cyclic segment, and the number of such oscillations can be controlled by applying a control voltage.

[0169] The relative difference in flight times between the first and second sets can essentially depend on the number of loops of an ionic orbit in the cyclic segment, and the number of loops can be estimated from the difference for at least one ion. The mass-to-charge ratios can be estimated for a set of loop candidates, and the true number of loops can be determined by comparing the mass-to-charge ratios estimated from the first and second sets of flight times.

[0170] Although the present invention has been described with reference to various embodiments, it is understood that various modifications can be made without deviating from the scope of protection of the invention as set out in the attached claims. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 9136101 [0024, 0084] UK 2580089 [0025, 0087] GB 2562690 [0097, 0154]

Claims

[1] Method for operating an analytical instrument comprising an ion analyzer configured to analyze ions by determining ion drift times along an ion path, wherein the ion path comprises at least a first segment and a cyclic segment, wherein the ion path is configured such that ions make a single pass through the first segment and make one or more passes through the cyclic segment; wherein the method comprises: Operating the analyzer in a first operating mode, wherein in the first operating mode (i) a first electrical potential is provided along the first segment of the ion path, (ii) a second electrical potential is provided along the cyclic segment of the ion path, (iii) the first segment of the ion path has a first path length, and (iv) the cyclic segment of the ion path has a second path length, and analyzing ions by determining drift times of ions along the ion path to obtain a first set of ion data; Operating the analyzer in a second operating mode by changing at least one of (i) the first electrical potential, (ii) the second electrical potential, (iii) the first path length and (iv) the second path length, and analyzing ions by determining drift times along the ion path to obtain a second set of ion data; Comparing the first set of ion data with the second set of ion data, and identifying a first ion peak in the first set of ion data that corresponds to a second ion peak in the second set of ion data; Determining the number N of iterations of the cyclic segment of the ion path taken by ions assigned to the corresponding first and second ion peaks; and Using the specified number of iterations N to determine a value of a physicochemical property of the ions assigned to the corresponding first and second ion peaks. [2] Method according to claim 1, wherein the ion analyzer is a time-of-flight (ToF) mass analyzer and wherein the physicochemical property is a mass-to-charge ratio (m / z). [3] The method of claim 2, wherein the time-of-flight mass analyzer is a multi-reflection time-of-flight (MR-ToF) mass analyzer, comprising: two ion mirrors spaced apart and facing each other in a first direction X, each mirror generally being extended along a drift direction Y between a first end and a second end, the drift direction Y being orthogonal to the first direction X; an ion injector for injecting ions into a space between the ion mirrors, wherein the ion injector is located near the first end of the ion mirrors; and a detector for capturing ions after they have completed a multitude of reflections between the ion mirrors, with the detector being located near the first end of the ion mirrors. [4] Method according to claim 3, wherein the analyzer is configured to analyze ions by: (i) Injecting ions from the ion injector into the space between the ion mirrors, the ions completing a first cycle in which the ions follow a zigzag ion path that has multiple K reflections between the ion mirrors in the X direction, while: (a) they drift along the Y direction towards the second end of the ion mirrors, (b) reverse the drift direction velocity near the second end of the ion mirrors, and (c) drift back along the Y direction towards the first end of the ion mirrors; (ii) they reverse the drift direction velocity of the ions near the first end of the ion mirrors, such that the ions are caused to complete a further cycle in which the ions follow a zigzag ion path that has multiple K reflections between the ion mirrors in the X direction, while: (a) they drift along the Y direction towards the second end of the ion mirrors, (b) they reverse the drift direction velocity near the second end of the ion mirrors, and (c) they drift back along the Y direction towards the first end of the ion mirrors; (iii) Repeat step (ii) once or several times; and then (iv) cause the ions to move towards the detector for detection. [5] The method of claim 4, wherein the multiple reflection time-of-flight (MR-ToF) mass analyzer further comprises: a deflector located near the first end of the ion mirrors; and the analyzer is configured to analyze ions by: (i) Injecting ions from the ion injector into the space between the ion mirrors, the ions completing a first cycle in which the ions follow a zigzag ion path that has multiple K reflections between the ion mirrors in the X direction, while: (a) they drift along the Y direction from the deflector towards the second end of the ion mirrors, (b) reverse the drift direction velocity near the second end of the ion mirrors, and (c) drift back along the Y direction towards the deflector; (ii) they use the deflector to reverse the drift direction velocity of the ions such that the ions are caused to complete a further cycle in which the ions follow a zigzag ion path that has multiple K reflections between the ion mirrors in the X direction, (a) drifting along the Y direction from the deflector towards the second end of the ion mirrors, (b) reversing the drift direction velocity near the second end of the ion mirrors, and (c) drifting back along the Y direction towards the deflector; (iii) Repeat step (ii) once or several times; and then (iv) cause the ions to move from the deflector to the detector for detection. [6] Method according to claim 4 or 5, wherein the method comprises changing the second path length in the second operating mode by changing the number K of reflections that ions make between the ion mirrors when following the zigzag ion path. [7] Method according to claims 5 and 6, wherein the number K of reflections made by ions between the ion mirrors when following the zigzag ion path is changed by changing a voltage applied to the deflector. [8] Method according to claim 5, 6 or 7, wherein the ion mirrors have a non-constant distance from each other in the X-direction along at least a part of their lengths in the drift direction Y, wherein an electric field opposes the drift direction velocity of ions towards the second end of the ion mirrors, which results from the non-constant distance between the two mirrors, and wherein the electric field causes the ions to reverse their drift direction velocity near the second end of the ion mirrors and drift back along the drift direction towards the deflector. [9] Method according to claim 5, 6 or 7, wherein the deflector is a first deflector and the analyzer comprises a second deflector located near the second end of the ion mirrors, wherein the second deflector is configured to cause the ions to reverse their drift direction velocity near the second end of the ion mirrors and drift back along the drift direction towards the deflector. [10] Method according to claim 1, wherein the analyzer is an ion mobility analyzer and wherein the physicochemical property is ion mobility. [11] Method according to any of the preceding claims, wherein the method comprises changing the first electrical potential in the second operating mode. [12] Method according to claim 11, wherein the device further comprises a flight tube arranged along at least a part of the first segment of the ion path, and wherein the method comprises changing the first electrical potential in the second operating mode by changing a voltage applied to the flight tube. [13] Method according to claim 11, wherein the ion analyzer comprises an ion injector configured to accelerate ions along the ion path, and wherein the method comprises changing the first electrical potential in the second operating mode by changing an acceleration field provided by the ion injector to accelerate ions along the ion path. [14] Method according to any of the preceding claims, comprising determining the number N of passes of the cyclic segment of the ion path taken by ions assigned to the corresponding first and second ion peaks: Measuring a drift time difference between first and second ion peaks; and Using the measured drift time difference to estimate the number N of passes of the cyclic segment of the ion path taken by ions assigned to the corresponding first and second ion peaks. [15] Non-volatile, computer-readable storage medium that stores computer program code which, when executed on a processor, performs the method according to any of the preceding claims. [16] Control system for an analyzer, wherein the control system is configured to cause the analyzer to perform the method according to any one of claims 1-14. [17] Analytical instrument, such as a mass and / or ion mobility spectrometer, comprising: an ion analyzer configured to analyze ions by determining ion drift times along an ion path, wherein the ion path comprises at least a first segment and a cyclic segment, the ion path being configured such that ions make a single pass through the first segment and one or more passes through the cyclic segment; and a control system configured to: Operating the analyzer in a first operating mode and analyzing ions by determining drift times of ions along the ion path to obtain a first set of ion data, wherein in the first operating mode (i) a first electrical potential is provided along the first segment of the ion path, (ii) a second electrical potential is provided along the cyclic segment of the ion path, (iii) the first segment of the ion path has a first path length, and (iv) the cyclic segment of the ion path has a second path length; Operating the analyzer in a second operating mode by changing at least one of (i) the first electrical potential, (ii) the second electrical potential, (iii) the first path length and (iv) the second path length, and analyzing ions by determining drift times along the ion path to obtain a second set of ion data; Comparing the first set of ion data with the second set of ion data, and identifying a first ion peak in the first set of ion data that corresponds to a second ion peak in the second set of ion data; Determining the number N of iterations of the cyclic segment of the ion path taken by ions assigned to the corresponding first and second ion peaks; and Using the specified number of iterations N to determine a value of a physicochemical property of the ions assigned to the corresponding first and second ion peaks. [18] Analyzer according to claim 17, wherein the ion analyzer is a time-of-flight (ToF) mass analyzer and the physicochemical property is a mass-to-charge ratio (m / z); or the analyzer is an ion mobility analyzer and the physicochemical property is ion mobility. [19] Analysis device according to claim 17 or 18, wherein the analyzer is a multi-reflection time-of-flight (MR-ToF) mass analyzer, comprising: two ion mirrors spaced apart and facing each other in a first direction X, each mirror generally being extended along a drift direction Y between a first end and a second end, the drift direction Y being orthogonal to the first direction X; an ion injector for injecting ions into a space between the ion mirrors, wherein the ion injector is located near the first end of the ion mirrors; and a detector for detecting ions after they have completed a multitude of reflections between the ion mirrors, the detector being located near the first end of the ion mirrors; the analyzer is configured to analyze ions by: (i) Injecting ions from the ion injector into the space between the ion mirrors, the ions completing a first cycle in which the ions follow a zigzag ion path that has multiple K reflections between the ion mirrors in the X direction, while: (a) they drift along the Y direction towards the second end of the ion mirrors, (b) reverse the drift direction velocity near the second end of the ion mirrors, and (c) drift back along the Y direction towards the first end of the ion mirrors; (ii) they reverse the drift direction velocity of the ions near the first end of the ion mirrors, such that the ions are caused to complete a further cycle in which the ions follow a zigzag ion path that has multiple K reflections between the ion mirrors in the X direction, while: (a) they drift along the Y direction towards the second end of the ion mirrors, (b) they reverse the drift direction velocity near the second end of the ion mirrors, and (c) they drift back along the Y direction towards the first end of the ion mirrors; (iii) Repeat step (ii) once or several times; and then (iv) cause the ions to move towards the detector for detection.

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