Device for reacting analyte ions with electron or reactant ions

Abstract

A method of a mass spectrometer and / or an ion mobility spectrometer, the method comprising: capturing electrons or reactant ions (3) within a reaction region using a DC electric field; analyte ions (16) are delivered into a first side of the reaction zone and through the reaction zone such that the analyte ions react with the electron or reactant ions (3) and the resulting ions (20) are allowed to exit the reaction zone through a second side of the reaction zone opposite the first side.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to UK Patent Application No. 2303726.0, filed on 14 March 2023. The entire contents of this application are incorporated herein by reference. Technical Field

[0003] This invention relates generally to a method for using a mass spectrometer and / or an ion mobility spectrometer, wherein analyte ions react with electrons or reactant ions to produce charge-reduced analyte ions, fragment ions, or other product ions. The invention also provides a mass spectrometer or mobility spectrometer configured to perform this method. Background Technology

[0004] In the field of mass spectrometry, ion-electron and ion-ion reactions are well-known during the analysis of analyte ions. Examples of such reactions include electron capture dissociation (ECD) and electron transfer dissociation (ETD). To perform ECD, multiple protonated analyte molecules (i.e., analyte ions) are confined together with low-energy electrons, causing the analyte molecules and electrons to react with each other, thereby fragmenting the analyte molecules into daughter ions. Similarly, in ETD, multiple protonated analyte molecules are confined together with low-energy reactant ions, causing the analyte molecules and reactant ions to react with each other, thereby fragmenting the analyte molecules into daughter ions. Besides ETD and ECD, other ion-electron or ion-ion reactions can also be used for ion analysis, such as electron-induced dissociation (EID).

[0005] Mass analysis using electron-based fragmentation techniques (such as those described above) is advantageous because it can be more informative than other fragmentation techniques (such as collision-induced dissociation (CID)) since the product ions produced by the reaction retain unstable post-translational modifications. Furthermore, during the aforementioned ion-electron interactions, some analyte molecules may not dissociate into fragment ions but may instead become charge-reduced. This charge reduction can be used to separate ions that would otherwise have overlapping charge states, thus enabling reliable charge annotation. Moreover, electron-based fragmentation techniques can generate higher-quality (more complete) or complementary fragment information for polymers such as peptides.

[0006] However, although ion-electron and ion-ion reaction devices are known, their design is often complex, and their operation can be challenging, for example, due to the difficulty in confining analyte ions and low-energy electrons or reactant ions in the same region for a sufficient time and at a sufficient density for the reaction to occur. For instance, known ECD devices use an RF electric field to confine analyte ions, but this RF field increases the energy of the reactant electrons, thus reducing the probability of analyte ions capturing electrons and consequently reducing the probability of a reaction. Other known reaction devices use strong magnetic fields to confine electrons to low energies, but these also present difficulties in confining both analyte ions and reactant electrons in the same region so that the reaction occurs at the desired rate. Summary of the Invention

[0007] The present invention provides a method for using a mass spectrometer and / or an ion mobility spectrometer, the method comprising: capturing electrons or reactant ions in a reaction region using a DC electric field; delivering analyte ions to a first side of the reaction region and passing through the reaction region, such that the analyte ions react with electrons or reactant ions, and allowing the resulting ions to leave the reaction region through a second side of the reaction region opposite to the first side.

[0008] Using only a DC electric field to confine electrons or reactant ions within the reaction region allows for their confinement without significantly increasing their energy. This provides a relatively high reaction rate with analyte ions because the electrons or reactant ions have relatively low energy and can be confined for a relatively long time.

[0009] The analyte ions are transported to the first side of the reaction region, and ions resulting from the reaction between the analyte ions and electrons or reactant ions (along with any unreacted analyte ions) are allowed to leave the opposite side of the reaction region. This is a particularly convenient arrangement for carrying out the reaction, and it also allows the analyte ions to have relatively high kinetic energy as they pass through the reaction region, so that the trajectories of these ions are relatively unaffected by the space charge field formed by the trapped electrons or reactant ions.

[0010] The analyte ions can be positively charged ions. In this case, these ions can react with electrons, or the reactant ions can be negatively charged ions. Alternatively, the analyte ions can be negatively charged ions. In this case, the reactant ions can be positively charged ions. However, it is also conceivable that the analyte ions can have the same polarity as the reactant ions or electrons, for example, such that the reaction is an electron separation and dissociation (EDD) reaction between a negative analyte ion and a higher-energy electron.

[0011] Analyte ions can react with electrons or reactant ions, causing the analyte ions to dissociate to form fragment ions and / or transforming them into analyte ions with reduced charge. For example, analyte ions can react with electrons or reactant ions via ECD or ETD reactions.

[0012] The capture may include capturing electrons or reactant ions among: (i) at least two electrostatic mirrors; (ii) at least two electrostatic sectors; or (iii) at least one electrostatic mirror and at least one electrostatic sector.

[0013] Each electrostatic mirror described herein has an opening at one of its ends for receiving electrons or reactant ions. The mirror also has electrodes and voltage sources arranged and configured to generate a DC electric field within the mirror, which causes any electrons or reactant ions entering the mirror through the opening to be reflected back through the opening. The mirror may include a plurality of spaced-apart electrodes and voltage sources configured to apply different DC voltages to different corresponding electrodes among these electrodes to generate a DC electric field that reflects electrons or reactant ions. Essentially, all electrodes of the mirror can be maintained at voltages of the same polarity.

[0014] Using at least one electrostatic mirror is advantageous for capturing electrons or reactant ions because the mirror focuses the electrons or reactant ions (orthogonal to the reflection direction), preventing the electron or reactant ion cloud from expanding too much in the reaction region. For example, the mirror can be configured such that the geometrical magnification of the electron or reactant ion beam does not increase significantly with successive reflections. It has been found that using at least one electrostatic mirror is a more efficient way to capture electrons or reactant ions compared to using simple blocking electrodes.

[0015] The capture allows electrons or reactant ions to oscillate primarily in the first dimension through the reaction region, and analyte ions to be transported substantially along the first dimension through the reaction region.

[0016] At least one electrostatic mirror can be used to capture electrons or reactant ions in the reaction region by reflecting electrons or reactant ions in a first dimension, and analyte ions can be transferred into and through the mirror along an axis substantially in the first dimension.

[0017] For example, two electrostatic mirrors can be used to capture electrons or reactant ions in a reaction region by reflecting electrons or reactant ions in a first dimension.

[0018] Because analyte ions can be transported to the first side of the reaction region traveling in the first dimension, this allows the analyte ions to pass through inflection points where electrons or reactant ions are reflected. As described elsewhere in this document, this can be advantageous because electrons or reactant ions have low kinetic energy at these points and are therefore more likely to react with the analyte ions.

[0019] Alternatively, the trapping causes electrons or reactant ions to oscillate primarily in the first dimension through the reaction region, and analyte ions can be transported into and through the reaction region along an axis substantially orthogonal to the first dimension.

[0020] At least one electrostatic mirror can be used to capture electrons or reactant ions in the reaction region by reflecting electrons or reactant ions in a first dimension, and analyte ions can be transferred into and through the mirror along an axis substantially orthogonal to the first dimension.

[0021] The analyte ions can pass through a position within the mirror where oscillating electrons or reactant ions are redirected in the first dimension.

[0022] Alternatively, the analyte ion may cross the reaction region at a location where the oscillating electron or reactant ion does not change direction. For example, the analyte ion may cross the reaction region at a location between the inflection points of the oscillating electron or reactant ion.

[0023] In the method disclosed herein, analyte ions can be transported to the reaction region with sufficient kinetic energy such that when the analyte ions react with electrons or reactant ions in the reaction region to form fragments and / or product ions, at least some of these fragments and / or product ions, as well as optionally unreacted analyte ions, have sufficient kinetic energy to leave the reaction region without being trapped within it. In other words, at least some of the fragments and / or product ions, as well as optionally unreacted analyte ions, may not be trapped by the DC electric field performing the trapping of electrons or reactant ions.

[0024] For example, if electrons or reactant ions are trapped between the electrostatic mirrors, analyte ions can be transported to the reaction region with sufficient kinetic energy, such that at least some of the fragments and / or product ions, as well as optionally unreacted analyte ions, pass through and exit at least one of the electrostatic mirrors.

[0025] This method may include capturing analyte ions such that they repeatedly pass through the reaction region in which electrons and reactant ions reside.

[0026] The steps of capturing analyte ions may include capturing analyte ions between: (i) at least two electrostatic microscopes; (ii) at least two electrostatic sectors; or (iii) at least one electrostatic microscope and at least one electrostatic sector.

[0027] The analyte ions are preferably captured by an electrostatic device that is different from the electrostatic device used to capture electrons or reactant ions.

[0028] The method may include: capturing electrons or reactant ions between a first mirror and a second mirror, such that the electrons or reactant ions oscillate back and forth between the first mirror and the second mirror in a first dimension; and capturing analyte ions between a third mirror and a fourth mirror, such that the analyte ions oscillate back and forth between the third mirror and the fourth mirror and pass through a reaction region therein where electrons and reactant ions are captured.

[0029] The third and fourth mirrors can reflect analyte ions, causing them to oscillate in the first dimension. Both the first and second mirrors can be located between the third and fourth mirrors, allowing the oscillating analyte ions to pass through the first and second mirrors in the first dimension.

[0030] Each of the first and second mirrors may have a first DC potential difference at its two ends in a first dimension for reflecting electrons or reactant ions, and each of the third and fourth mirrors may have a larger second DC potential difference at its two ends in a first dimension for reflecting analyte ions.

[0031] All DC potentials applied to the first and second mirrors to form the first DC potential difference can have a magnitude of ≤10V or ≤5V.

[0032] These small potentials help ensure that the trajectory of analyte ions is not adversely affected.

[0033] Therefore, the first potential difference can be ≤10V or ≤5V.

[0034] The second potential difference needs to be large enough to reflect analyte ions, which may have significantly more kinetic energy than electrons or reactant ions, for example, due to the way they are formed by the ion source and / or so that the analyte ions can be transported through the first and second mirrors without their trajectory being significantly adversely affected.

[0035] The second potential difference is preferably at least 50V. For example, the second potential difference can be ≥60V, ≥70V, ≥80V, ≥90V, ≥100V, ≥120V, ≥140V, or ≥160V.

[0036] The method may include: capturing electrons or reactant ions such that the electrons or reactant ions oscillate back and forth in a first dimension; and capturing analyte ions such that the analyte ions oscillate back and forth through the reaction region along an axis at an angle to the first dimension.

[0037] For example, the axis can be substantially orthogonal to the first dimension.

[0038] Electrostatic components (such as those described herein) can be used to capture analyte ions. Alternatively, other components can be used to capture analyte ions, such as devices that use RF voltage to confine or reflect analyte ions, for example, RF ion directors.

[0039] The method may include generating electrons or reactant ions within the reaction region.

[0040] In the methods disclosed herein, the analyte ions and / or reactant ions can be multiply charged ions. For example, the charge state of a multiply charged analyte ion can be ≥3.

[0041] Using highly charged analyte ions is advantageous because it reduces the density of electrons or reactant ions that need to be trapped in the reaction region and / or does not require low energy of electrons or reactant ions to achieve a given reaction rate.

[0042] Therefore, higher charge states are preferred, such as at least 5, at least 10, at least 20, at least 40, at least 60, at least 80, or at least 100 charge states. A charge state of at least 100 has been found to be particularly advantageous.

[0043] The method may include maintaining the pressure in the reaction zone at 10. -5 Up to 10 -1 Between millibars. This pressure results in a collision rate low enough between gas molecules and electrons or reactant ions to avoid significant loss, while being high enough to help reduce the thermal energy of electrons or reactant ions.

[0044] The analyte ion can react with electrons or reactant ions to dissociate the analyte ion to form fragment ions and / or to convert the analyte ion into a reduced-charge analyte ion; and the method may further include mass analysis of the fragment ions and / or the reduced-charge analyte ions or ions derived therefrom using a mass analyzer to obtain mass spectrometry data.

[0045] Mass analysis of ions can be performed within the reaction zone, such as by using inductive or capacitive ion detectors. Alternatively, fragment ions and / or charge-reduced analyte ions (as well as any unreacted analyte ions) can be transferred from the reaction zone to a downstream mass analyzer, which performs mass analysis on the fragment ions and / or charge-reduced analyte ions or ions derived therefrom.

[0046] The method may include providing molecules of a known kind in a reaction region and reacting these molecules with electrons or reactant ions to form calibrator ions with a known mass-to-charge ratio; performing mass analysis on the calibrator ions in a mass analyzer to measure the mass-to-charge ratio of the calibrator ions; and calibrating the mass spectrometry data based on the difference between the known mass-to-charge ratio of the calibrator ions and the measured mass-to-charge ratio.

[0047] Electrons or reactant ions can be confined within the reaction apparatus without the use of any RF electric or magnetic fields.

[0048] By confining electrons or reactant ions within the reaction region without using magnets, this method can be relatively low in complexity and cost. For example, magnetic fields can cause channel bending of electrons, reactant ions, or analyte ions, which can be problematic. Additionally, magnetic confinement can enhance the space charge effect, potentially affecting the trajectories and focusing of ions and electrons. Furthermore, the stability of the magnetic field can vary with temperature.

[0049] The present invention also provides a mass spectrometer and / or ion mobility spectrometer configured to perform any of the methods described herein.

[0050] Therefore, the present invention provides a mass spectrometer and / or ion mobility spectrometer comprising: an ion source for generating analyte ions; an electrostatic trap for capturing electrons or reactant ions in a reaction region using a DC electric field; and at least one ion guiding device for guiding analyte ions to a first side of the electrostatic trap such that the analyte ions pass through the reaction region inside the electrostatic trap, and wherein the electrostatic trap is configured to allow ions obtained by the reaction between the analyte ions and electrons or reactant ions to leave a second side of the electrostatic trap opposite to the first side.

[0051] As described above, the spectrometer can be configured to perform any of the methods described herein.

[0052] Therefore, an electrostatic trap may include: (i) at least two electrostatic mirrors; (ii) at least two electrostatic sectors; or (iii) at least one electrostatic mirror and at least one electrostatic sector.

[0053] An electrostatic trap can be configured to cause electrons or reactant ions to oscillate primarily in a first dimension through a reaction region, and at least one ion guiding device can be arranged to guide analyte ions substantially along the first dimension through the reaction region. For example, at least one electrostatic mirror can be used to capture electrons or reactant ions in the reaction region by reflecting them in the first dimension, and analyte ions can be transferred into and through the mirror along an axis substantially in the first dimension. Two electrostatic mirrors can be used to capture electrons or reactant ions in the reaction region by reflecting them in the first dimension.

[0054] The electrostatic trap can be configured to allow electrons or reactant ions to oscillate primarily in the first dimension through the reaction region, and at least one ion guiding device is arranged and configured to guide analyte ions along an axis substantially orthogonal to the first dimension through the reaction region and to the location where the oscillating electrons or reactant ions within the electrostatic trap are redirected.

[0055] An electrostatic trap may include at least one electrostatic mirror, and at least one ion guiding device may be arranged to guide analyte ions through the mirror.

[0056] Alternatively, at least one ion guiding device may be arranged to guide analyte ions through the reaction region at positions where oscillating electrons or reactant ions do not change direction. For example, at least one ion guiding device may be arranged to allow analyte ions to pass through the reaction region at positions between the turning points of oscillating electrons or reactant ions.

[0057] The spectrometer can be configured to deliver analyte ions to the reaction region with sufficient kinetic energy, such that when the analyte ions react with electrons or reactant ions in the reaction region to form fragments and / or product ions, at least some of these fragments and / or product ions, as well as optionally unreacted analyte ions, have sufficient kinetic energy to leave the reaction region without being trapped within it. For example, the spectrometer can have a voltage source configured to apply a voltage to the electrodes of the spectrometer to provide the sufficient kinetic energy for the analyte ions.

[0058] Alternatively, at least one ion guiding device may be arranged and configured to capture analyte ions such that they repeatedly pass through the reaction region in which electrons and reactant ions reside.

[0059] The at least one ion guiding device may include: (i) at least two electrostatic mirrors; (ii) at least two electrostatic sectors; or (iii) at least one electrostatic mirror and at least one electrostatic sector.

[0060] The analyte ions are preferably captured by an electrostatic device that is different from the electrostatic device used to capture electrons or reactant ions.

[0061] The electrostatic trap may include a first mirror and a second mirror for capturing electrons or reactant ions, such that the electrons or reactant ions oscillate back and forth between the first mirror and the second mirror in a first dimension; wherein at least one guiding device includes a third mirror and a fourth mirror for capturing analyte ions, such that the analyte ions oscillate back and forth between the third mirror and the fourth mirror and pass through the reaction region; and wherein the third mirror and the fourth mirror are arranged and configured to reflect the analyte ions, such that the analyte ions oscillate in the first dimension, and wherein both the first mirror and the second mirror are located between the third mirror and the fourth mirror, such that the oscillating analyte ions pass through the first mirror and the second mirror in the first dimension.

[0062] The spectrometer may have a voltage source configured to apply a voltage to the electrodes of each of the first and second mirrors, such that each of these mirrors has a first DC potential difference across its terminals in a first dimension for reflecting electrons or reactant ions. The spectrometer may also have a voltage source configured to apply a voltage to the electrodes of each of the third and fourth mirrors, such that each of these mirrors has a larger second DC potential difference across its terminals in a first dimension for reflecting analyte ions.

[0063] The voltage applied to the electrodes of the first and second mirrors to form the first DC potential difference can have a magnitude of ≤10V or ≤5V.

[0064] The voltage applied to the electrodes of the third and fourth mirrors to form the second DC potential difference can have a magnitude of at least 50V.

[0065] The spectrometer may have one or more vacuum pumps in communication with the reaction region, the one or more vacuum pumps being configured to maintain the pressure in the reaction region at 10. -5 Up to 10 -1 Between milligrams.

[0066] The spectrometer may include a mass analyzer for mass analysis of fragment ions and / or analyte ions with reduced charge or ions derived therefrom to obtain mass spectrometry data.

[0067] Mass analysis of ions can be performed within the reaction zone, such as by using inductive or capacitive ion detectors. Alternatively, fragment ions and / or charge-reduced analyte ions (as well as any unreacted analyte ions) can be transferred from the reaction zone to a downstream mass analyzer, which performs mass analysis on the fragment ions and / or charge-reduced analyte ions or ions derived therefrom.

[0068] Methods and spectrometers have been described in which analyte ions are delivered to a first side of a reaction region and pass through the reaction region, such that they react with electrons or reactant ions, and the resulting ions are allowed to exit the reaction region through a second side opposite the first side. However, it is contemplated that the resulting ions may alternatively exit the reaction region through the first side, for example in an embodiment where the ions are reflected between mirrors. Attached Figure Description

[0069] Various embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, wherein:

[0070] Figure 1 A schematic diagram of a reaction apparatus according to an embodiment of the present invention is shown;

[0071] Figure 2 It shows the relationship with Figure 1 The same implementation scheme as the one described above, except that the analyte ions are transported through the reaction apparatus along a different axis;

[0072] Figure 3 An embodiment in which analyte ions and reactant ions or electrons are simultaneously captured in the reaction apparatus along the same axis is shown;

[0073] Figure 4 An embodiment in which analyte ions and reactant ions or electrons are simultaneously captured in the reaction apparatus along different axes is shown;

[0074] Figure 5 It shows the relationship with Figure 1 The implementation schemes are the same as those in the previous schemes, except that the mirrors for capturing electrons or reactant ions are configured differently;

[0075] Figure 6 An embodiment in which electrons or reactant ions are captured by an electrostatic sector is shown; and

[0076] Figure 7 A schematic diagram of a mass spectrometer according to an embodiment of the present invention is shown. Detailed Implementation

[0077] Embodiments of the present invention provide an ion-electron or ion-ion reaction apparatus for reacting analyte ions with electrons or reactant ions. Electrons or reactant ions can be confined within the reaction apparatus without the use of any RF electric or magnetic field. For example, a DC electric field can be used solely to confine the electrons or reactant ions. Analyte ions may also be trapped within the reaction apparatus as they react with electrons or reactant ions. Alternatively, analyte ions can be simply transported through the reaction apparatus, wherein electrons or reactant ions are trapped, such that the reaction can occur without trapping the analyte ions within the reaction apparatus.

[0078] In embodiments where the analyte ion reacts with the captured electron, the analyte ion can be a positively charged ion. In embodiments where the analyte ion reacts with the captured reactant ion, the analyte ion and the reactant ion preferably carry opposite charges. For example, the analyte ion can be a positive ion, while the reactant ion can be a negative ion, or vice versa.

[0079] The reaction apparatus can be used to react analyte ions with electrons or reactant ions to cause a reduction in the charge of the analyte ions and / or to cause the analyte ions to dissociate into fragment ions (e.g., ECD or ETD).

[0080] Figure 1 A schematic diagram of a reaction apparatus according to an embodiment of the invention is illustrated. The reaction apparatus includes a first mirror 2 for reflecting electrons or reactant ions 3 and a second mirror 4 for reflecting electrons or reactant ions 3. The mirrors are spaced apart from each other by a flight region 6. The mirrors are arranged and configured such that electrons or reactant ions are repeatedly reflected back and forth between the two mirrors in a first dimension, such that electrons or reactant ions are trapped in the first dimension. Such mirrors for reflecting charged particles are known, such as ion mirrors, or reflectors.

[0081] Each mirror has an opening 8 at one of its ends in a first dimension for receiving electrons or reactant ions. The mirror also has electrodes and voltage sources arranged and configured to generate a DC electric field within the mirror, which causes any electrons or reactant ions entering the mirror through the opening to be reflected back through the opening. For example, the mirror may include a plurality of electrodes 10 and voltage sources spaced apart along the first dimension, the voltage sources being configured to apply different DC voltages to different corresponding electrodes among these electrodes to generate a DC electric field that reflects electrons or reactant ions. For example, if electrons or negative reactant ions are captured between the mirrors, gradually increasing negative DC voltages can be applied to the electrodes within each mirror according to the distance from the opening 8. Conversely, if positive reactant ions are captured between the mirrors, gradually increasing positive DC voltages can be applied to the electrodes within each mirror according to the distance from the opening.

[0082] Each mirror may have an end cap 12 at the end opposite the opening 8 in the first dimension. The end cap may be one of the electrodes 10 having a voltage applied thereto to reflect electrons or reactant ions. However, it is conceivable that an end cap electrode may not be provided.

[0083] It should be understood that the voltage applied to the electrodes of the mirror for reflecting electrons or reactant ions also serves to confine the electrons or reactant ions within the mirror in a dimension orthogonal to the first dimension. If the flight region 6 is provided between the mirrors, the flight region can be provided by arranging one or more electrodes to extend between the mirrors. For example, tubular electrodes or other ion-guiding electrodes can be arranged between the mirrors. One or more DC voltages can be applied to one or more electrodes to confine electrons or reactant ions in a dimension orthogonal to the first dimension when they are reflected between the mirrors. For example, one or more electrodes can be maintained at the same voltage as the electrodes defining the entrance opening of the mirror, such that there is essentially no axial electric field in the flight region.

[0084] The first mirror includes an analyte inlet port 14 for receiving analyte ions 16 into the reaction apparatus, such that the analyte ions are transported to a region that traps electrons or reactant ions, thereby causing the analyte ions to react with electrons or reactant ions and dissociate to produce fragment ions and / or other product ions, such as charge-reduced analyte ions or adduct ions. The second mirror 4 includes an outlet port 18 for allowing product ions 20 to exit the reaction apparatus.

[0085] In the illustrated embodiment, the inlet aperture 14 and outlet aperture 18 are arranged such that the axis passing through these apertures extends along a first dimension through the region in which electrons or reactant ions are captured. Therefore, analyte ions can be propelled into the inlet aperture with sufficient energy in the first dimension, causing fragments and / or product ions derived therefrom to exit through the outlet aperture. As described above, the analyte ions (and the fragments and / or product ions derived therefrom) preferably have the opposite polarity to the captured electrons or reactant ions. Therefore, the voltage applied to the mirror will generate a DC electric field that attracts the analyte ions towards the mirror electrodes, and opposite to the movement of the analyte ions through the first mirror 2 in the direction toward the outlet aperture 18.

[0086] Analyte ions 16 are transported with sufficient energy in the first dimension into the inlet aperture 14, enabling the analyte ions, along with their derived fragments and / or product ions, to overcome the forces generated by the DC gradient in the first mirror 2 and to travel to and exit from the outlet aperture 18. The DC voltage applied to the mirror electrode 10 can have a relatively low amplitude to minimize these negative effects on the movement of the analyte ions. Therefore, it should be understood that the voltage applied to the electrodes of the reaction apparatus and the energy of the analyte ions entering the reaction apparatus are selected such that the analyte ions, along with their derived fragments and / or product ions, are not trapped (and / or substantially deflected) within the reaction apparatus.

[0087] In the illustrated embodiment, the inlet hole 14 and the outlet hole 18 are respectively provided in the end caps 12 of the first mirror 2 and the second mirror 4, although this is not required.

[0088] Figure 2 Showing about Figure 1 Another embodiment of the same implementation described herein, except that the analyte ions 16 are transported through the reaction apparatus along a different axis. More specifically, the inlet orifice 14 and the outlet orifice 18 are arranged on opposite sides of the first mirror 2 such that the analyte ions interact with electrons or reactant ions 3 in the first mirror, and the resulting fragments and / or product ions 20 exit the reaction apparatus from the first mirror. The analyte ions can be transported along an axis substantially orthogonal to the first dimension. This has various advantages, such as minimizing the loss of fragments and / or product ions because of their shorter path length through the reaction apparatus. Preferably, this axis extends through the region within the mirror where electrons or reactant ions are deflected. The kinetic energy of the trapped electrons or reactant ions is minimum at this location, thus providing a relatively high probability of reaction between electrons or reactant ions and the analyte ions as the analyte ions pass through this region.

[0089] Although the analyte ions are only illustrated as being transported through the first mirror 2, it should be understood that the analyte ions can also, or alternatively, be transported through the second mirror 3 in a corresponding manner. For example, the analyte ions can be transported through the first mirror 2 and then also guided through the second mirror 4. It is conceivable that the ions can repeatedly circulate around such a device to repeatedly pass through the inflection points of electrons or reactant ions in the two mirrors 2, 4. Additionally or alternatively, the analyte ions can also be transported through the flight region 6 (if it exists) in a direction substantially orthogonal to the first dimension.

[0090] Return to reference Figure 1It should be understood that capturing analyte ions in the same region as the region where reactant ions or electrons are captured is not direct. First, analyte ions have the opposite polarity to reactant ions or electrons, making it difficult to confine both polarities when using only a DC electric field. Second, reactant ions or electrons are expected to have low kinetic energy, thus requiring a relatively small DC electric field to confine them. If the analyte ions have relatively high kinetic energy, such a field may not be suitable for confining them.

[0091] Figure 3 An embodiment of the present invention for simultaneously capturing analyte ions 16 and reactant ions or electrons 3 within a reaction apparatus is shown. The reaction apparatus includes a first trap 21 for capturing reactant ions or electrons 3. The first trap can be configured with respect to... Figure 1 The reaction apparatus is configured and operated in the same manner as described, such that reactant ions or electrons are trapped between mirrors 2 and 4. Figure 3 The reaction apparatus also includes a third mirror 22 and a fourth mirror 24 arranged at opposite ends of the first ion trap 21 in the first dimension. The third and fourth mirrors are mirrors that reflect the analyte ions 16 back and forth between them, such that the ions pass through the first trap as they pass between the mirrors 22 and 24.

[0092] In addition to being suitable for reflecting analyte ions 16 with higher kinetic energy than reactant ions or electrons 3, each of the third mirror 22 or the fourth mirror 24 may have a configuration corresponding to that of the first mirror 2 or the second mirror 4. That is, each of the third and fourth mirrors has an opening at one end of its end 26 in the first dimension for receiving analyte ions from the first trap. Each of these mirrors 22, 24 also has electrodes 28 and voltage sources arranged and configured to generate an electric field, such as a DC electric field, within the mirrors 22, 24, which causes any analyte ions entering the mirrors 22, 24 through the opening 26 to be reflected back out of the mirrors and back into the first trap. For example, the mirrors 22, 24 may include a plurality of electrodes 28 and voltage sources spaced apart along the first dimension, the voltage sources being configured to apply different voltages (such as DC voltages) to different corresponding electrodes among these electrodes to generate an electric field that reflects the analyte ions. For example, if positive analyte ions are captured between the mirrors, a progressively increasing positive DC voltage can be applied to the electrodes in each mirror 22, 24, depending on the distance from the opening 26. Conversely, if negative analyte ions are captured between the mirrors 22, 24, a progressively increasing negative DC voltage can be applied to the electrodes in each mirror, depending on the distance from the opening 26.

[0093] Each of the third and fourth mirrors may have an end cap 30 at its end opposite its opening 26 in a first dimension. The end cap may be one of the electrodes 28 having a voltage applied thereto to reflect analyte ions. At least one of the mirrors 22, 24 has an inlet port 32 for introducing analyte ions into the reaction apparatus. For example, analyte ions 16 may be introduced through the inlet port 32 in the end cap 30 of the third mirror 22. At least one of the mirrors 22, 24 has an outlet port for extracting fragment or product ions generated within the reaction apparatus. The outlet port may be the same as the inlet port 32, or it may be another port, such as the port 34 in the end cap of the fourth mirror 24.

[0094] During operation, reactant ions or electrons are introduced into the first well 21, or generated within the first well. For example... Figure 3 As shown in extension 40, in an embodiment where electrons are trapped in the first trap 21, electrons 3 can be generated within the first trap by means of a heated filament 42. The filament can generate electrons with a kinetic energy of, for example, a few electron volts. These electrons are then reflected back and forth between mirrors 2 and 4 of the first trap in the manner described above, i.e., along the axis in the first dimension. The filament can be spaced apart from the axis in a direction orthogonal to the axis, and the electrons generated by the filament can be propelled onto the axis by one or more deflector electrodes 44, such that the electrons travel along the axis and are reflected by the mirrors. The density of the trapped electrons eventually accumulates to a density sufficient to provide a reaction with the analyte (such as an ECD reaction). Alternatively, as described above, reactant ions instead of electrons can be trapped in the first trap.

[0095] As described above, analyte ions are introduced into the reaction apparatus through inlet aperture 32 in the third mirror 22. The inlet aperture is arranged such that the injected analyte ions have sufficient kinetic energy to pass through the third mirror in the first dimension, through the inlet opening 26 of the third mirror, through the first trap 21 in which reactant ions or electrons are captured, and into the fourth mirror 24. When the analyte ions pass through the first trap, they can react with reactant ions or electrons to produce fragment ions or product ions, such as analyte ions with reduced charge. The fragment or product ions, along with analyte ions that have not yet reacted with reactant ions or electrons, are then passed into the fourth mirror. The fourth mirror then reflects these ions in the first dimension, causing them to return to the first trap and pass through it, and then into the third mirror. The ions can then leave the reaction apparatus, or the third and fourth mirrors can reflect the ions a further number of times, repeating the above process, wherein each time the analyte ions return through the first trap, they are able to react with reactant ions or electrons.

[0096] Once the analyte ions have passed through the first trap a sufficient number of times, i.e., after reacting with reactant ions or electrons for a sufficient duration, the third and / or fourth mirrors (or another part of the reaction apparatus) can be switched so that fragment or product ions are optionally ejected from the reaction apparatus along with any unreacted analyte ions, allowing for mass analysis of these ions. For example, the electric field in the third and / or fourth mirrors used to reflect ions can be altered to allow ions to exit through exit openings in the third and / or fourth mirrors, such as through openings 32, 34 in the end cap electrodes 30 of the mirrors.

[0097] Alternatively or additionally, for mass analysis of ions downstream of the reaction apparatus, the ions can be analyzed within the reaction apparatus. For example, an ion detector can be positioned within the reaction apparatus to determine the frequency at which the captured ion species oscillate between the third and fourth mirrors. The frequency at which ions oscillate in this manner indicates their mass-to-charge ratio, therefore the spectrometer can have circuitry configured to determine the mass-to-charge ratio of the ions captured within the reaction apparatus based on the oscillation frequency of the ions detected between the third and fourth mirrors. Thus, the ion detector can be a Fourier transform ion detector.

[0098] The ion detector can be an inductive or capacitive detector with electrode 46, inducing a charge on the electrode each time an ion oscillates and passes through it. The signal induced at the electrode is detected and used to determine the frequency of the ion oscillation between the third and fourth mirrors. These frequencies are then used by the spectrometer to determine the mass-to-charge ratio of the ions. The electrodes of the ion detector can be, for example, plate electrodes or tubular electrodes, through which the ions pass when they oscillate. The electrodes can be arranged between the third and fourth mirrors, within the first trap, such as in the flight region of the first trap.

[0099] In this embodiment, an inductive or capacitive detector has been described as including electrodes 46 arranged between the mirrors of the first trap. However, to minimize the number of electrodes picking up signals from oscillating electrons or reactant ions, the inductive or capacitive detector may include one or more electrodes axially located outside the first trap. For example, electrodes may be arranged between the first trap and mirror 22, and / or between the first trap and mirror 24, to pick up ion signals generated by analyte ions and / or fragment or product ions derived therefrom. These electrodes may be selected to be at a ground potential. If electrodes are arranged on both sides of the first trap, signals from these electrodes may be combined and analyzed as a single signal, or amplified separately and analyzed as two distinct signals.

[0100] Alternatively or additionally, the ion detector may be a bombardment detector arranged within the path of the oscillating ions, such that a portion of these ions bombard the detector during each oscillation. Similarly, the signal from the detector can be used to determine the frequency at which the ions oscillate between the third and fourth mirrors, and these frequencies can then be used by a spectrometer to determine the mass-to-charge ratio of the ions. The surface of the ion detector bombarded by ions may be, for example, a microchannel plate.

[0101] As described above, inductive or capacitive ion detectors can be used to detect ion signals caused by ions oscillating within the device. As is well known in charge detection mass spectrometry (CDMS), the amplitude of the detected ion signal can be used to determine the mass of the ion.

[0102] Figure 3 An example of potential distribution 48 is shown, which can be provided along the central axis of the reaction apparatus when analyte ions and reactant ions or electrons are trapped within the reaction apparatus. The example shown is used to trap negative reactant ions or electrons in a first trap and positive analyte ions between the third and fourth mirrors. However, it should be understood that the polarity of the potential values ​​shown can be reversed to trap both negative analyte ions and positive reactant ions. The magnitudes of the potential values ​​shown can also vary depending on the energies of the trapped analyte ions and reactant ions or electrons.

[0103] As can be seen, each mirror in the first well has a relatively small potential difference across its ends to reflect reactant ions or electrons, while each of the third and fourth mirrors has a larger potential difference across its ends to reflect analyte ions. This is because the reactant ions or electrons are tuned to have relatively low kinetic energy to provide a relatively high probability of reacting with the analyte ions, which have higher kinetic energy, as they pass through the first well. In the example shown, the flight region between the mirrors in the first well is grounded at 0V, and a potential difference of 4V is provided across each mirror to reflect and trap reactant ions or electrons between them. It should be understood that the potential difference across each of these mirrors can be greater than or less than the potential difference shown. For example, other potential differences less than or equal to, for example, 5V or 10V can be used to trap electrons within the first well, while larger potential differences can be used to trap reactant ions within the first well.

[0104] As described above, the analyte ions need to pass through mirrors 2 and 4 of the first trap in two directions. Therefore, the potential applied to the mirrors of the first trap is preferably relatively small, such that they do not substantially interfere with the axial movement of the analyte ions as they pass through the first trap. Electrons or reactant ions trapped in the first trap will be charged and will therefore also have a potential, but the charge density of the trapped electrons or reactant ions makes the potential negligible and substantially does not interfere with the movement of the analyte ions through the first trap.

[0105] In the example shown, the third and fourth mirrors are designed to reflect analyte ions with an energy of 130V per charge. The potential at the inlet of each of the third and fourth mirrors is -4V, and the potential at each end cap electrode is +170V. However, other potential differences can be provided to create a potential gradient suitable for reflecting and trapping the analyte ions. For example, if the analyte ions have relatively high kinetic energy, a relatively high potential difference will be maintained across each of the third and fourth mirrors, while if the analyte ions have lower kinetic energy, a lower potential difference can be maintained across each of the third and fourth mirrors.

[0106] Figure 4 Another implementation is shown, which is related to... Figure 3 The illustrated and described embodiments are identical, except that the first well 21 is arranged to reflect electrons or reactant ions 3 along a first axis, while the third mirror 22 and the fourth mirror 24 are arranged to reflect analyte ions 16 along a second axis at an angle to the first axis, wherein the first axis intersects the second axis such that the analyte ions can react with electrons or reactant ions at the region where the axes intersect. In this embodiment, a field-free flight region 6, 50, can be provided between the mirrors in the first well, and a field-free flight region 50 can be provided between the third and fourth mirrors, and the axes can intersect in the field-free flight regions 6, 50. This arrangement provides the reaction region in a relatively simple manner. It should be understood that one or more electrodes forming the flight region 6 of the first well 21 have openings along an axis orthogonal to the first axis to allow analyte ions to pass through the first well. Furthermore, one or more electrodes 52 can be disposed between the first well 21 and each of the third mirror 22 and the fourth mirror 24 to define the flight region 50 along which the analyte ions travel. The mass analysis of fragments or product ions can be performed in the manner described above, i.e., inside and / or outside the reaction apparatus.

[0107] For example, inductive or capacitive detectors can be used for mass analysis of fragment or product ions (and / or analyte ions). In such embodiments, the elongated electrodes of the inductive or capacitive detector extend along the dimension along which the fragment or product ions (and / or analyte ions) oscillate, orthogonal to the dimension along which the electron or reactant ions oscillate. Therefore, the signal picked up from the oscillating electron or reactant ions is minimized. One such electrode can be arranged between the first trap and mirror 22, and / or between the first trap and mirror 24, to pick up the ion signals generated by the analyte ions and / or fragment or product ions derived therefrom. These electrodes can be selected to be at a ground potential. If electrodes are arranged on both sides of the first trap, the signals from these electrodes can be combined and analyzed as a single signal, or amplified separately and analyzed as two distinct signals.

[0108] Despite Figure 4 The first axis is shown as being orthogonal to the second axis, but it is conceivable that these axes could be at other angles to each other, as long as they intersect.

[0109] Figure 5 Showing about Figure 1 Another embodiment shown is identical to the described embodiment, except that the mirrors 2 and 4, which capture electrons or reactant ions 3, have different configurations. According to... Figure 5 Mirrors 2 and 4 still receive electrons or reactant ions along an axis extending through opening 8, but each mirror includes one or more DC electrodes having surfaces that converge toward the axis according to their distance from opening 8 to generate a DC field along the axis that reflects electrons or reactant ions. For example, each mirror may have a tapered inner surface that converges in a direction away from the opening to generate a DC field along the axis that reflects electrons or reactant ions. Alternatively, each mirror may include multiple elongated electrodes, such as rods or plates, arranged such that their inner surfaces converge in a direction away from the opening to generate a DC field along the axis that reflects electrons or reactant ions.

[0110] about Figure 5 The described electron or reactant ion trapping arrangement may replace any electron or reactant ion trapping arrangement described elsewhere in this document, such as those concerning... Figures 1 to 4 As described.

[0111] Figure 6Another embodiment is shown in which electrons or reactant ions 3 are captured by two electrostatic sectors 60, 62. In the example shown, electrons or reactant ions 3 enter the entrance of the first electrostatic sector in electrostatic sector 60, are guided along a curved path within the sector, leave the first sector, and then travel through flight area 64 to reach the entrance of the second sector in sector 62. Electrons or reactant ions enter the entrance of the second sector 62, are guided along a curved path within the sector, leave the second sector, and then travel through flight area 64 to reach the entrance of the first sector. Thus, electrons or reactant ions are captured by sectors 60, 62.

[0112] Analyte ions 16 are introduced into a region between sectors, through which electrons or reactant ions travel as they pass between sectors. At least some of the analyte ions react with electrons or reactant ions 3, producing fragment or product ions 20 in a manner described elsewhere herein. These fragments or products are then transported downstream. Although not shown, analyte ions may be directed into the reaction region via an ion director, and / or fragment / product ions may be directed away from the reaction region via an ion director. It is conceivable that the analyte ions and the fragment / product ions generated therefrom may be trapped, causing them to repeatedly cross the reaction region. For example, Figure 6 The trapping device for electrons or reactant ions shown can replace the one described above. Figure 4 The described capture device.

[0113] Electrostatic sectors can be 2D sectors, or they can be 3D sectors, such as hemispherical sectors.

[0114] Furthermore, although two sectors are shown for capturing electrons or reactant ions along a figure-eight flight path, such that the electrons or reactant ions pass through the reaction region twice for each loop through the sector, it is conceivable that other configurations and numbers of sectors could be used, for example, to capture electrons or reactant ions along a flight path such that the electrons or reactant ions pass through the reaction region only once or more than twice for each loop through the sector.

[0115] According to the embodiments described herein, the trapping region for capturing electrons or reactant ions is ideally maintained at a relatively low sub-atmospheric pressure, resulting in a relatively low collision rate between the gas and the electrons or reactant ions. However, the gas pressure in this region is also desirable to be high enough to help reduce the thermal energy of the captured electrons or reactant ions. Therefore, the gas pressure in this region can be 10... -7 10 millibars -1 Between millibars. The gas can be an inert gas.

[0116] Although embodiments in which the captured electrons react with analyte ions have been described, it is conceivable that the captured electrons may alternatively or additionally react with background gas molecules in the reaction region to ionize these gas molecules and form radical or non-radical cations and anions, for example, via electron collision ionization (EI). Based on knowledge of what the gas comprises, the types of cations and anions produced can be predicted, and thus the true mass-to-charge ratio of such ions can be known. Therefore, these cations or anions can be mass-analyzed by the same mass analyzer used for mass analysis of fragment or product ions, and can thus be used as calibration or lock-in mass ions for the calibration of the mass analyzer, i.e., for correcting the mass-to-charge ratio of ions detected by the mass analyzer. Alternatively, radical or non-radical cations and anions may be captured in the reaction region and react with analyte ions.

[0117] Embodiments of the present invention enable analyte ions with relatively high charge states to react with electrons or reactant ions. For relatively highly charged ions, the probability of electron-ion interactions is relatively high because the Thomson radius, which defines the trapping / interaction area, increases with the square of the ion charge.

[0118] For example, in ion-electron interaction events, the Thomson radius, which defines the trapping cross-sectional area, increases as a function of the square of the ion's charge state and is inversely proportional to the square of the electron-ion pair's kinetic energy (at the center of the mass frame). For instance, if the charge state of the analyte ion increases from 3+ to 300+, the trapping cross-sectional area increases by 10,000. Therefore, analyte ions with relatively high charge states require only a relatively low density of electrons to achieve a certain rate of ion-electron reaction, while analyte ions with lower charge states require a higher density of electrons to achieve the same rate of ion-electron reaction. Thus, using highly charged analyte ions means that conventional, relatively complex techniques for trapping electrons with magnetic fields and RF fields to enhance low-energy electron density can be avoided.

[0119] Furthermore, analyte ions in relatively low-charge states require relatively low-energy electrons to achieve a certain rate of ion-electron reaction, while analyte ions in higher-charge states do not require electrons with such low energy to achieve the same rate of ion-electron reaction. Therefore, using analyte ions in relatively high-charge states alleviates design constraints, as capturing low-energy electrons is more challenging than capturing higher-energy electrons. Additionally, because relatively high-charge analyte ions have a relatively high probability of reacting with electrons, the reaction region can be relatively small. This allows for greater freedom in how analyte ions and electrons intersect. For example, the electron beam can be captured along the axis, and the analyte ions can pass orthogonally through the beam, rather than the analyte ions having to pass along the beam's axis.

[0120] Figure 7 A schematic diagram of an embodiment of a mass spectrometer including the reaction apparatus as described herein is shown. The spectrometer includes an ion source 70 and a reaction apparatus 72. The ion source may be an electrospray ionization (ESI) ion source. Any other type of ion source may be used instead of an ESI ion source, but as described above, an ion source that produces analyte ions with a high charge state is preferred. The analyte ions generated in the ion source, or ions derived therefrom, are transferred to the reaction apparatus. The ions may be filtered, for example, in a quadrupole mass filter 74, and / or separated by mobility in an ion mobility separator 76 before entering the reaction apparatus. The ions transferred to the reaction apparatus react with electrons or reactant ions therein, for example via an ECD or ETD reaction, to produce fragments, product ions, or analyte ions with reduced charge. These ions, along with any unreacted analyte ions, can be mass-analyzed within the reaction apparatus in the manner described above. Alternatively, these ions may be ejected or released from the reaction apparatus and transferred downstream for analysis. For example, these ions can be analyzed to determine their ion mobility through the ion mobility separator 78 and / or their mass-to-charge ratio can be determined using the mass analyzer 80 downstream of the reaction apparatus.

[0121] Although the invention has been described with reference to various embodiments, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of the invention as set forth in the appended claims.

[0122] For example, although certain devices for capturing electrons or reactant ions and optionally for capturing analyte ions have been described, it should be understood that various other forms of devices can be used. For example, other forms or electrostatic traps, electrostatic mirrors, or electrostatic sectors can be used to capture electrons or reactant ions. These devices can be arranged and configured to capture electrons or reactant ions at low kinetic energies. Because the captured electrons or reactant ions are at low energies, only a low DC voltage is required at the electrodes of the device to maintain the capture (e.g., ≤5V). Therefore, analyte ions can be transported through the captured electrons or reactant ions at higher kinetic energies (e.g., ≥100eV), such that the trajectory of the analyte ions is substantially unaffected by the capture of electrons or reactant ions, or only slightly modified. This greatly simplifies the operation of the reaction apparatus. Analyte ions with lower kinetic energies can be used, for example, to improve reaction efficiency, but their trajectories are more likely to be deflected by the field of the captured electrons or reactant ions. In such embodiments, an additional electric field can be provided to correct the deflected trajectory of the analyte ions.

[0123] The device used to capture electrons or reactant ions, and optionally analyte ions, can be a gridless device. This avoids particle scattering and loss.

[0124] The device used to capture electrons or reactant ions, and optionally analyte ions, can be a plane or cylindrical mirror / reflector, or a quadratic or quadratic field can be used.

[0125] Although the mirror used to capture analyte ions has been described as an embodiment of a DC-only device, it is conceivable that such a device could additionally or alternatively use an RF field or even a magnetic field, provided that the electrons or reactant ions are not subjected to these fields.

[0126] Embodiments in which the analyte ions have opposite polarity to the reactant ions or electrons to produce a reaction have been described. For example, the reaction can be ECD, ETD, negative ETD (referred to as nETD), wherein a negative analyte ion reacts with a positive reactant ion or EID. However, the invention is also applicable to reactions between analyte ions having the same polarity as the reactant ions or electrons, for example, to electron separation dissociation (EDD) reactions between a negative analyte ion and a higher-energy electron.

Claims

1. A method for using a mass spectrometer and / or an ion mobility spectrometer, the method comprising: Using a DC electric field to capture electrons or reactant ions within the reaction region; The analyte ions are delivered to a first side of the reaction region and pass through the reaction region, such that the analyte ions react with electrons or reactant ions, and the resulting ions are allowed to exit the reaction region through a second side of the reaction region opposite to the first side.

2. The method of claim 1, wherein the capture comprises capturing the electron or reactant ion between: (i) at least two electrostatic mirrors; (ii) at least two electrostatic sectors; or (iii) at least one electrostatic mirror and at least one electrostatic sector.

3. The method according to claim 1 or 2, wherein the capture causes the electron or reactant ion to oscillate primarily in the first dimension through the reaction region, and the analyte ion is transported substantially along the first dimension through the reaction region.

4. The method of claim 3, wherein at least one electrostatic mirror is used to capture the electrons or reactant ions in the reaction region by reflecting the electrons or reactant ions in the first dimension, and wherein the analyte ions are transferred into and through the mirror along an axis substantially in the first dimension.

5. The method of claim 1 or 2, wherein the capture causes the electron or reactant ion to oscillate primarily in the first dimension through the reaction region, and the analyte ion is transported into and through the reaction region along an axis substantially orthogonal to the first dimension.

6. The method of claim 5, wherein at least one electrostatic mirror is used to capture the electrons or reactant ions in the reaction region by reflecting the electrons or reactant ions in the first dimension, and wherein the analyte ions are transmitted into and through the mirror along an axis substantially orthogonal to the first dimension.

7. The method of claim 6, wherein the analyte ions pass through a position within the mirror, and electrons or reactant ions oscillating at the position deflect in the first dimension.

8. The method according to any preceding claim, wherein the analyte ions are delivered to the reaction region with sufficient kinetic energy such that when the analyte ions react with the electrons or reactant ions in the reaction region to form fragments and / or product ions, at least some of these fragments and / or product ions, as well as optionally unreacted analyte ions, have sufficient kinetic energy to leave the reaction region without being trapped in the reaction region.

9. The method according to any preceding claim, the method comprising capturing the analyte ion such that the analyte ion repeatedly passes through the reaction region in which the electron and the reactant ion are located.

10. The method according to claim 9, wherein the method comprises: The electrons or reactant ions are captured between the first mirror and the second mirror, causing the electrons or reactant ions to oscillate back and forth between the first mirror and the second mirror in the first dimension; as well as The analyte ions are captured between the third and fourth mirrors, such that the analyte ions oscillate back and forth between the third and fourth mirrors and pass through the reaction region where the electrons and reactant ions are captured.

11. The method of claim 10, wherein the third mirror and the fourth mirror reflect the analyte ions such that the analyte ions oscillate in the first dimension, and wherein both the first mirror and the second mirror are located between the third mirror and the fourth mirror such that the oscillating analyte ions pass through the first mirror and the second mirror in the first dimension.

12. The method of claim 11, wherein each of the first and second mirrors has a first DC potential difference at its two ends in the first dimension for reflecting the electrons or reactant ions, and wherein each of the third and fourth mirrors has a larger second DC potential difference at its two ends in the first dimension for reflecting the analyte ions.

13. The method of claim 12, wherein all DC potentials applied to the first mirror and the second mirror to form the first DC potential difference have a magnitude of ≤10V or ≤5V.

14. The method according to any one of claims 1 to 10, the method comprising: The electrons or reactant ions are captured, causing them to oscillate back and forth in the first dimension; as well as The analyte ions are captured such that they oscillate back and forth along an axis at an angle to the first dimension through the reaction region.

15. The method according to any of the preceding claims, wherein the analyte ion and / or the reactant ion is a multiply charged ion.

16. The method according to any preceding claim, wherein the analyte ion reacts with the electron or reactant ion to dissociate the analyte ion to form fragment ions and / or to convert the analyte ion into a charge-reduced analyte ion; and wherein the method further comprises performing mass analysis on the fragment ions and / or the charge-reduced analyte ions or ions derived therefrom using a mass analyzer to obtain mass spectrometry data.

17. The method of claim 16, the method comprising providing molecules of a known kind in the reaction region and reacting these molecules with the electron or reactant ion to form a calibrator ion having a known mass-to-charge ratio; performing mass analysis on the calibrator ion in the mass analyzer to measure the mass-to-charge ratio of the calibrator ion; and The mass spectrometry data are calibrated based on the difference between the known mass-to-charge ratio of the calibrator ion and the measured mass-to-charge ratio.

18. The method according to any of the preceding claims, wherein the electrons or reactant ions are confined within the reaction apparatus without the use of any RF electric or magnetic field.

19. A mass spectrometer and / or an ion mobility spectrometer, said mass spectrometer and / or ion mobility spectrometer comprising: An ion source, said ion source being used to generate analyte ions; An electrostatic trap is used to capture electrons or reactant ions in a reaction region using a DC electric field; and At least one ion guiding device is provided for guiding the analyte ions to a first side of the electrostatic trap, such that the analyte ions pass through the reaction region inside the electrostatic trap, and wherein the electrostatic trap is configured to allow ions resulting from a reaction between the analyte ions and the electrons or reactant ions to exit a second side of the electrostatic trap opposite to the first side.

20. The spectrometer of claim 19, wherein the electrostatic trap is configured to cause the electron or reactant ion to oscillate primarily in a first dimension through the reaction region, and the at least one ion guiding device is arranged and configured to guide the analyte ion along an axis substantially orthogonal to the first dimension through the reaction region and through the position of the oscillating electron or reactant ion within the electrostatic trap.

21. The spectrometer of claim 19, wherein the electrostatic trap comprises a first mirror and a second mirror for trapping the electrons or reactant ions, such that the electrons or reactant ions oscillate back and forth between the first mirror and the second mirror in a first dimension; The at least one guiding device includes a third mirror and a fourth mirror for capturing the analyte ions, such that the analyte ions oscillate back and forth between the third mirror and the fourth mirror and pass through the reaction region; and The third and fourth mirrors are arranged and configured to reflect the analyte ions such that the analyte ions oscillate in the first dimension, and both the first and second mirrors are located between the third and fourth mirrors such that the oscillating analyte ions pass through the first and second mirrors in the first dimension.

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