MASS ANALYSER

Abstract

A mass analyser for use in a mass spectrometer, the mass analyser having: a set of sector electrodes spatially arranged to provide an electrostatic field in a 2D reference plane suitable for guiding ions along an orbit in the 2D reference plane, wherein the set of sector electrodes extend along a drift path that is locally orthogonal to the reference plane so that, in use, the set of sector electrodes provide a 3D electrostatic field region; and an injection interface configured to inject ions into the mass analyser via an injection opening such that the ions injected into the mass analyser are guided by the 3D electrostatic field region along a 3D reference trajectory according to which ions perform multiple turns within the mass analyser whilst drifting along the drift path, wherein each turn corresponds to a completed orbit in the 2D reference plane. The injection interface includes at least one injection deflector located within the mass analyser, the at least one injection deflector being configured to deflect ions injected into the mass analyser in the direction of the drift path, wherein the injection interface is preferably configured so that ions guided along the 3D reference trajectory are, after injection into the mass analyser, kept adequately distant from the injection opening such that they are substantially unaffected by electric field distortions around the injection opening.

Claims

1. A mass analyser for use in a mass spectrometer, the mass analyser having: a set of sector electrodes spatially arranged to provide an electrostatic field in a 2D reference plane suitable for guiding ions along an orbit in the 2D reference plane, wherein the set of sector electrodes extend along a drift path that is locally orthogonal to the reference plane so that, in use, the set of sector electrodes provide a 3D electrostatic field region; and an injection interface configured to inject ions into the mass analyser via an injection opening such that the ions injected into the mass analyser are guided by the 3D electrostatic field region along a 3D reference trajectory according to which ions perform multiple turns within the mass analyser whilst drifting along the drift path, wherein each turn corresponds to a completed orbit in the 2D reference plane; wherein the injection interface includes at least one injection deflector located within the mass analyser, the at least one injection deflector being configured to deflect ions injected into the mass analyser in the direction of the drift path, wherein the injection interface is preferably configured so that ions guided along the 3D reference trajectory are, after injection into the mass analyser, kept adequately distant from the injection opening such that they are substantially unaffected by electric field distortions around the injection opening.

2. A mass analyser according to claim 1, wherein the injection deflector is configured to deflect ions injected into the mass analyser in the direction of the drift path so as to increase the distance between the 3D reference trajectory and the injection opening.

3. A mass analyser according to claim 1, wherein the at least one injection deflector is configured to deflect ions injected into the mass analyser in the direction of the drift path before those ions have completed their first half turn within the mass analyser.

4. A mass analyser according to claim 1, wherein: the mass analyser includes an extraction interface configured to extract ions out from the mass analyser via an extraction opening after the ions extracted out from the mass analyser have been guided by the 3D electrostatic field region along the 3D reference trajectory; and the extraction deflector is configured to deflect ions injected into the mass analyser in the direction of the drift path so as to increase the distance between the 3D reference trajectory and the extraction opening.

5. A mass analyser according to claim 4, wherein the at least one extraction deflector is configured to deflect ions injected into the mass analyser in the direction of the drift path after those ions have started their last three turns within the mass analyser.

6. A mass analyser according to claim 4, wherein the at least one injection deflector is used as the at least one extraction deflector.

7. A mass analyser according to claim 1, wherein the drift path is curved around a reference axis, and the 3D reference trajectory includes at least five pairs of adjacent turns for which an angle measured using straight lines extending from the reference axis to corresponding vertices of the adjacent turns of the 3D reference trajectory as projected in a plane perpendicular to the reference axis is 6 or less.

8. A mass analyser according to claim 1, wherein the drift path is linear, and the 3D reference trajectory includes at least five turns for which an angle measured using straight lines extending between three consecutive vertices of the 3D reference trajectory as projected in a plane perpendicular to the 2D reference plane is 3 or less.

9. A mass analyser according to claim 1, wherein the mass analyser includes a reversing deflector set, wherein the reversing deflector set includes one or more reversing deflectors configured to reverse the direction in which ions drift along the drift path, so that ions drifting towards the reversing deflector set are made to drift back towards the injection interface.

10. A mass analyser according to claim 9, wherein the mass analyser includes a second reversing deflector set, wherein the second reversing deflector set includes one or more reversing deflectors configured to reverse the direction in which ions drift along the drift path, so that ions drifting towards the second reversing deflector set are made to drift back towards the first reversing deflector set.

11. A mass analyser according to claim 10, wherein the at least one injection deflector is configured to additionally operate as the second reversing deflector set.

12. A mass analyser according to claim 9, wherein at least one extraction deflector is configured to additionally operate as a reversing deflector set.

13. A mass analyser according to claim 10, wherein the at least one injection deflector is configured to additionally operate the at least one extraction deflector, and as the second reversing deflector set.

14. A mass analyser according to claim 1, wherein at least one above-mentioned deflector is positioned at a location along the 3D reference trajectory at which the 3D reference trajectory is not surrounded by sector electrodes.

15. A mass analyser according to claim 1, wherein the mass analyser includes one or more focussing lens electrodes configured to focus ions towards the 3D reference trajectory, wherein at least one above-mentioned deflector is located within a focussing lens electrode.

16. A mass spectrometer having: an ion source for producing ions having different initial coordinates and velocities; a mass analyser according to any previous claim, wherein the injection interface is configured to inject ions produced by the ion source into the mass analyser via the injection opening such that the ions are guided along the 3D reference trajectory; an ion detector for detecting ions produced by the ion source after the ions have been guided along the 3D reference trajectory.

17. A mass analyser for use in a mass spectrometer, the mass analyser having: a set of sector electrodes spatially arranged to provide an electrostatic field in a 2D reference plane suitable for guiding ions along an orbit in the 2D reference plane, wherein the set of sector electrodes extend along a drift path that is locally orthogonal to the reference plane so that, in use, the set of sector electrodes provide a 3D electrostatic field region; and an extraction interface configured to extract ions out from the mass analyser via an extraction opening after the ions extracted out from the mass analyser have been guided by the 3D electrostatic field region along a 3D reference trajectory according to which ions perform multiple turns within the mass analyser whilst drifting along the drift path, wherein each turn corresponds to a completed orbit in the 2D reference plane; wherein the extraction interface includes at least one extraction deflector, located within the mass analyser, the at least one extraction deflector being configured to deflect ions following the 3D reference trajectory in the direction of the drift path, wherein the extraction deflector is configured to deflect ions following the 3D reference trajectory in the direction of the drift path so as to increase the distance between the 3D reference trajectory and the extraction opening.

18. A mass spectrometer having: an ion source for producing ions having different initial coordinates and velocities; a mass analyser according to claim 16, wherein the mass analyser is configured to guide ions produced by the ion source along the 3D reference trajectory; an ion detector for detecting ions produced by the ion source after the ions have travelled along the 3D reference trajectory and have been extracted from the mass analyser by the extraction interface via the extraction opening.

Description

SUMMARY OF THE FIGURES

[0111] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

[0112] FIGS. 1A and 1B show a mass analyser implementing the disclosure of U.S. Pat. No. 9,082,602B2.

[0113] FIGS. 2A and 2B show a mass analyser implementing the present invention.

[0114] FIG. 3 shows another mass analyser implementing the present invention.

[0115] FIGS. 4A and 4B show another mass analyser implementing the present invention.

[0116] FIGS. 5A-C show another mass analyser implementing the present invention.

[0117] FIGS. 6A-B show another mass analyser implementing the present invention.

[0118] FIG. 7 shows another mass analyser implementing the present invention.

[0119] FIGS. 8A-B show another mass analyser implementing the present invention.

[0120] FIG. 9 shows another mass analyser implementing the present invention.

[0121] FIG. 10 shows an alternative positioning of deflectors of the injection and extraction interfaces.

[0122] FIGS. 11A(i)-C show example parallel plate deflectors.

[0123] FIGS. 12A(i)-C(ii) show example combined parallel plate and multipole deflectors.

[0124] FIGS. 13A-B show an example of a deflector embedded into a conical lens electrode.

DETAILED DESCRIPTION OF THE INVENTION

[0125] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

[0126] In the following examples, additional deflectors located within a mass analyser are used to cause ions to fly farther away from the injection and extraction openings which cause large electric field distortions. This helps to improves analyser mass resolution.

[0127] In addition, this also allows for an increased number of turns performed by ions within the mass analyser, which again helps to improve mass resolution.

[0128] Finally, injection and extraction deflectors can be used for additional steering to compensate for possible alignment errors of the main electrodes, e.g. to reduce losses of ions on reversing deflectors and/or small extraction openings. This may help to improve transmission efficiency.

[0129] In the examples shown, small additional deflectors are included, in addition to the sector electrodes of a mass analyser. The purpose of the deflectors in these examples is to deflect ions in the drift direction so as to increase distances from the injection opening to the first turn ion trajectories and from the extraction opening to the last turn ion trajectories. This means that field distortions at the injection/extraction openings have a significantly lowered influence on mass resolution and transmission efficiency. At least one injection deflector is needed in order to deflect ions away from the injection opening (if present). At least one extraction deflector is needed in order to deflect ions away from the extraction opening (if present). The same deflector(s) may be used as both injection and extraction deflectors. The deflectors are positioned inside the mass analyser, preferably in a field free region. Alternatively, they can be embedded into internal focussing lens electrodes. Apart from the main purpose of bypassing the areas of poor field quality the injection/extraction deflectors can also be used for additional steering in the two transverse directions to compensate for possible alignment errors of the main electrodes.

[0130] FIGS. 1A and 1B show a mass analyser implementing the disclosure of U.S. Pat. No. 9,082,602B2.

[0131] This mass analyser includes: [0132] a set of sector electrodes spatially arranged to provide an electrostatic field in a reference plane suitable for guiding ions along an orbit in the 2D reference plane, wherein the set of sector electrodes extend along a drift path D that is locally orthogonal to the reference plane so that, in use, the set of sector electrodes provide a 3D electrostatic field region; and [0133] an injection interface configured to inject ions into the mass analyser via an injection opening such that the ions injected into the mass analyser are guided by the 3D electrostatic field region along a 3D reference trajectory according to which ions perform multiple turns within the mass analyser whilst drifting along the drift path, wherein each turn corresponds to a completed orbit in the 2D reference plane.

[0134] As depicted, the reference plane is perpendicular to the page on which FIGS. 1A and 1B are shown.

[0135] In FIGS. 1A and 1B, a mass analyser 1 is shown with ions 10 being injected from an external ion source (not shown) via an injection opening 3a at the distal end of an injection tube 3.

[0136] At the end of the first turn ion pass the region near the injection opening 3a of the injection tube 3, at which location the electrostatic field produced by the sector electrodes of the mass analyser is distorted by the presence of the injection tube 3.

[0137] Thus, as taught by U.S. Pat. No. 9,082,602B2, a PCB fringe field corrector 5 is used to compensate electric field distortions at the injection opening 3a. This PCB fringe field corrector 5 is described in detail in U.S. Pat. No. 9,082,602B2, with reference to FIG. 15D of U.S. Pat. No. 9,082,602B2. A similar PCB fringe field corrector may also be used at an extraction opening of the mass analyser (not shown).

[0138] A disadvantage of the PCB fringe field corrector 5 shown in FIGS. 1A and 1B is that ions may pass too close to the corrector 5. This problem is exacerbated at small analyser sizes or small drift angles (i.e. a larger number of turns). In such cases both the analyser mass resolving power and transmission efficiency may be reduced. Besides, misalignments of the correctors or their poor fabrication quality may contribute to degradation of the same key parameters.

[0139] FIGS. 2A and 2B show a mass analyser 101 implementing the present invention.

[0140] In this example, the injection interface includes a single injection deflector 107, located within the mass analyser, the injection deflector 107 being configured to deflect ions injected into the mass analyser in the direction of the drift path D before those ions have completed a first turn within the mass analyser so as to increase the distance between the deflected ions completing the first turn and the injection opening 103a. Note that as a result of including the injection deflector 107, the distance between the 3D reference trajectory and the injection opening 103a is significantly increased, that is ions following the 3D reference trajectory pass less close to the injection opening 103a than would have been case had the injection deflector 107 been absent.

[0141] Thus the injection deflector 107 is used to increase distance from ions moving within the mass analyser to the injection tube 103 (other than ions entering the mass analyser through the injection tube) and therefore the injection opening 103a. The distance is preferably made large enough, so that influence of the field distortion by the tube 103 on the ion optics of the mass analyser is negligible, and so that a PCB fringe field corrector 105 is not required.

[0142] As depicted in FIGS. 2A and 2B a PCB fringe field corrector 5 is not used. However, in other examples (not shown), a PCB fringe field corrector 5 may be used, but its influence on the ion beam will be substantially reduced as a result of the primary deflector 107.

[0143] In this example, the primary deflector 107 is located in a field free region of the 3D reference trajectory about halfway through the first closed orbit (turn) completed by the ions.

[0144] FIG. 3 shows another mass analyser 101 implementing the present invention.

[0145] In this example, an extraction interface includes a single extraction deflector 109, located within the mass analyser, the extraction deflector 109 being configured to deflect ions following a 3D reference trajectory in the direction of the drift path D after those ions have started their last turn within the mass analyser so as to increase the distance between the deflected ions entering their last turn and an extraction opening 104a at the distal end of an extraction tube 104. The extracted ions 111 may then be detected by a suitable detector, e.g. a TOF detector. Note that as a result of including the injection deflector 107, the distance between the 3D reference trajectory and the extraction opening 104a is significantly increased, that is ions following the 3D reference trajectory pass less close to the extraction opening 104a than would have been case had the extraction deflector 109 been absent.

[0146] In the example of FIG. 2 only a single injection deflector 107 is used. The inventor notes that it is possible (by appropriately locating this deflector 107 and setting the deflection it provides accordingly, as well as appropriately setting up the injection tube 103) to both ensure that ions completing their first turn are adequately spaced from the injection opening 103a, whilst also achieving a small angle (in the drift direction D) between adjacent turns of the 3D reference trajectory.

[0147] Similarly, in the example of FIG. 3, only a single extraction deflector 109 is used. The inventor notes that it is possible (by appropriately locating this deflector 109 and setting the deflection it provides accordingly, as well as appropriately setting up the extraction tube 104) to both ensure that ions entering their last turn are adequately spaced from the extraction opening 104a, whilst also achieving a small angle (in the drift direction D) between adjacent turns of the 3D reference trajectory.

[0148] However, as will now be described in relation to FIGS. 4A and 4B, if reversing deflectors are used, the considerations are more complex and it is generally preferred to use more than one injection deflector and more than one extraction deflector, and preferably the same injection deflectors are also used as the extraction deflectors, to avoid ions hitting these deflectors.

[0149] FIGS. 4A and 4B show another mass analyser 201 implementing the present invention.

[0150] In this example, an injection interface which includes an injection tube 203 also includes injection deflectors 207a, 207b.

[0151] The injection deflectors 207a, 207b are configured to deflect ions injected into the mass analyser via an injection opening 203a of the injection tube 203 in the direction of the drift path before those ions have completed a first turn within the mass analyser so as to increase the distance between the deflected ions completing the first turn and the injection opening.

[0152] In this example, the mass analyser includes a reversing deflector set that includes two reversing deflectors 215a, 215b wherein the reversing deflectors 215a, 215b are configured to reverse the direction in which ions drift along the drift path, so that ions are made to drift back towards the injection interface.

[0153] Thus, in this example, ions are made two perform two passes of the instrument before extraction. The reason for including two injection deflectors 207a, 207b can best be understood from the discussion of FIG. 5B below. The reason for including two reversing deflectors 215a, 215b here is to improve isochronous properties in the drift direction, and also because it is technically difficult to position a single reversing deflector inside the main sector S2.

[0154] In this example, the injection and extraction tubes 203, 204 are located one above the other (see FIG. 4B), and the injection deflectors 207a, 207b are also used as extraction deflectors (by applying appropriate voltages at the appropriate times), and are therefore referred to as injection/extraction deflectors 207a, 207b.

[0155] The injection/extraction deflectors 207a, 207b are configured to, when used as extraction deflectors, deflect ions following the 3D reference trajectory in the direction of the drift path after those ions have started their last turn within the mass analyser so as to increase the distance between the deflected ions entering their last turn and the extraction opening.

[0156] In this example, the injection/extraction deflectors 207a, 207b are located one above the other in field free regions of the 3D reference trajectory, as are the injection and extraction tubes 203, 204, thus the azimuthal positions of the injection and extraction tubes 203, 204 coincide (see FIG. 4B). Such a layout helps to provide maximum flight path length and hence mass maximum resolving power m/dm.

[0157] With the layout shown in FIGS. 4A and 4B, the deflectors 207a, 207b are used for both injection (where ions are deflected by both of them over the first half-turn) and for extraction (where ions pass through and deflected by both of them over the last half-turn before extraction).

[0158] In this example, it is envisaged that each deflector 207a, 207b take the form of parallel plates, separated in a direction of the drift path, wherein the potentials on the two plates are not equal, even at equal geometry parameters, so as to provide deflection.

[0159] Since the same deflectors 207a, 207b are used for injection and extraction, the potentials applied to these deflectors 207a, 207b are preferably switchable so that the potentials applied to the deflectors 207a, 207b for injection are swapped to the potentials applied to the deflectors 207a, 207b for extraction, before extraction begins.

[0160] By extending the flight path, the mass resolving power m/dm can be increased.

[0161] In the example shown in FIGS. 4A and 4B (preferably also the examples shown in FIGS. 2-3), the deflectors of the injection and extraction interfaces are preferably located in field free regions of the 3D reference trajectory, in the upper and lower (polar) regions of the mass analyser.

[0162] FIGS. 5A-C show another mass analyser 301 implementing the present invention.

[0163] In this example, ions are made two perform two passes of the instrument before extraction, and there is only one injection deflector 307, and only one extraction deflector 309.

[0164] As can be seen from FIG. 5B, in order for only one injection deflector 307 and only one extraction deflector 309 to be used, the 3D reference trajectory passes very close to the injection and extraction deflectors 307, 309. There is very little room for installation of these deflectors 307, 309 between the adjacent turns. For this reason an analyser 301 having the form shown in FIGS. 5A-C cannot be made too small. Also, there will be additional losses of ions (oscillating around the reference trajectory) on the deflectors 307, 309, and higher tolerance requirements to positioning of the deflector azimuthally will be required. These problems can be avoided by using two deflectors for injection and two deflectors for extraction (as in the embodiment shown in FIGS. 4A-B), but FIGS. 5A-C do at least show that it is possible to use only one injection deflector 307, and only one extraction deflector 309.

[0165] FIGS. 6A-B show another mass analyser 401 implementing the present invention.

[0166] Here, the drift path is linear, i.e. extending along a straight line, with just one injection deflector 407 located within the first half-turn after injection, and one extraction deflector 409 located within the last half-turn before extraction. No injection/extraction PCB correctors are used.

[0167] The positioning of the deflectors 407, 409 can be seen from the side view of FIG. 6B.

[0168] FIG. 7 shows a modified mass analyser 401 similar to that shown in FIGS. 6A-B, except that here the injection deflector 407 is located within the second turn after injection. Similarly, the extraction deflector 409 is located within the second from last turn.

[0169] Here, the injection deflector 407 is configured to increase the distance between the 3D reference trajectory and the injection opening by being mutually configured with the injection tube 403 such that the injection interface injects ions into the mass analyser with an initial trajectory such that ions are substantially unaffected by electric field distortions around the injection opening, wherein the injection deflector is configured to bring subsequent turns within the mass analyser closer together.

[0170] FIGS. 8A-B show another mass analyser 501 implementing the present invention.

[0171] Here, the drift path is linear, i.e. extending along a straight line, with just one injection deflector 507 located within the first half-turn after injection of ions 510 through the injection opening 503, and one extraction deflector 509 located within the last half-turn before extraction of ions 511 through the extraction opening 504. No injection/extraction PCB correctors are used.

[0172] In this example, reversing deflectors 515a, 515b (upper and lower) are used to allow ions to perform two passes of the mass analyser 501.

[0173] FIG. 9 shows a modified mass analyser 501 similar to that shown in FIGS. 8A-B, except that here the injection deflector 507 and extraction deflector 509 are used as a second reversing deflector set, such that ions can be made to complete more than two passes of the mass analyser.

[0174] FIG. 10 shows an alternative positioning of deflectors of the injection and extraction interfaces.

[0175] In the example shown in FIG. 10, deflectors 607a, 607b of the injection and extraction interfaces are positioned within focussing lens electrodes L1, L2 configured to focus ions towards the 3D reference trajectory.

[0176] Note that separation in the direction of the drift path of adjacent turns inside lenses L1, L2 is much larger than is the case at the polar regions, so deflectors embedded within focussing electrodes may be advantageous for analysers of very small size, compared with locating the deflectors in the polar regions (in which their positioning might be difficult in a small analyser).

[0177] A potential issue with locating deflectors within focussing lens electrodes is that the inventor has deduced from simulations that such deflectors need to be able to deflect ions in both the direction of the drift path and a transverse direction that is locally perpendicular to the reference trajectory and to the drift path.

[0178] Whereas the inventor has observed that positioning the deflectors in the polar regions can be implemented using only deflectors able to deflect ions in the direction of the drift path (although some additional deflection in the transverse direction might still be desirable for correcting misalignments, even if the deflectors are positioned in the polar regions). The inventor also observes that embedding deflectors in focussing lens electrodes is in general more difficult in manufacturing and assembling compared with electrodes to be located in field free regions.

[0179] FIGS. 2B and 7 have been labelled with the drift angle 115, 415 for a curved drift path example and a linear drift path example, based on the definitions already provided above (the straight lines referenced in those earlier definitions are shown here as dashed lines).

[0180] By way of comparison, in the analyser shown in FIG. 1, the drift angle (angle between adjacent turns) cannot be made too small (typically it needs to be at least 5-6) since at small drift angles ions pass too close to the injection/extraction PCB correctors. Whereas use of injection/extraction deflectors according to the invention permits drift angle to be made smaller on the portion of the 3D reference trajectory that is after the injection deflector(s) and before the extraction deflector(s), and indeed the drift angle is preferably made as small a possible down to a minimum drift angle that depends on deflector dimensions and separation of adjacent turns at the deflector positions. Positioning inside conical focussing lens electrodes F1, F2 (as in FIG. 10 discussed below) could allow the use of 3 or even smaller drift angles resulting in respectively increased turn numbers.

[0181] FIGS. 11A(i)-(iii) schematically show a parallel plate deflector for generating deflecting electric field in the drift direction by applying positive and negative potentials +V and V to the plates.

[0182] FIG. 11 B shows a 3D model of another parallel plate deflector.

[0183] FIG. 11C shows a 3D model of another parallel plate deflector.

[0184] FIGS. 12A(i)-(ii) schematically show a combined parallel plate deflector for generating deflecting electric fields in the drift direction and in the (other) transverse direction by applying, respectively, potentials +V.sub.1 and +V.sub.2 to the plates.

[0185] FIG. 12B shows a multipole deflector (having twelve poles) for generating deflecting electric fields in the drift direction and in the (other) transverse direction by applying a number of potentials distributed over the poles.

[0186] FIGS. 12C(i)-(ii) respectively show 3D models of (i) the combined parallel plate deflector and (ii) the multipole deflector.

[0187] FIGS. 13A-B show an example of a deflector embedded into a conical lens electrode (e.g. as may be used in the example shown in FIG. 10) for generating electric field for deflecting ions in the drift direction. In addition to the main deflector electrodes with potentials +V.sub.1 there are auxiliary inner (lower in the figure) and outer (upper in the figure) electrodes with potentials +0.742V.sub.1 and +0.25V.sub.1 dedicated to improvement of the electric field uniformity in the (other) transverse direction.

[0188] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0189] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0190] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0191] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0192] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word comprise and include, and variations such as comprises, comprising, and including will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0193] It must be noted that, as used in the specification and the appended claims, the singular forms a, an, and the include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent about, it will be understood that the particular value forms another embodiment. The term about in relation to a numerical value is optional and means for example +/10%.

REFERENCES

[0194] A number of publications are cited above in order to more fully describe and disclose the invention and the state of the art to which the invention pertains. Full citations for these references are provided below. The entirety of each of these references is incorporated herein. [0195] A High Resolution Multi-turn TOF Mass Analyser, V. Shchepunov et al, SHIMADZU REVIEW, Vol. 72, No. 3.4 (2015). [0196] U.S. Pat. No. 9,082,602B2 [0197] U.S. Pat. No. 7,504,620B2 [0198] WO2011/086430A1 [0199] WO2018/033494A1