ion trap

Abstract

An ion trap includes a multipole electrode assembly, a first confinement electrode, and a second confinement electrode. The multipole electrode assembly is configured to confine ions of the first polarity in an ion channel extending in an axial direction of the multipole electrode assembly. The first confinement electrode is disposed adjacent to the multipole electrode assembly and extends in the axial direction of the multipole electrode assembly. The second confinement electrode is disposed adjacent to the multipole electrode assembly and extends in the axial direction of the multipole electrode assembly in alignment with the first confinement electrode. The first and second confinement electrodes are spaced apart in the axial direction so as to define an ion confinement region of the ion channel between the first and second confinement electrodes. The first and second confinement electrodes are configured to receive a DC potential of the first polarity to further confine ions in the ion confinement region within the ion channel.

Description

Technical Field

[0001] This disclosure relates to ion traps and methods for ion capture. More specifically, this disclosure relates to ion traps for use in mass spectrometers. Background Technology

[0002] Ion traps can be used to accumulate ions prior to ion implantation mass analyzers. Specifically, such ion traps (often referred to as extraction traps) can be used to accumulate ions prior to ion implantation orbital trap mass analyzers or time-of-flight mass analyzers. Ion accumulation in the extraction trap can be used to convert a continuous ion beam into a concentrated, cooled ion cloud with spatial properties that match the accepting properties of the mass analyzer.

[0003] Linear ion traps known in the art can utilize a combination of RF potentials to confine ions radially using some form of multipole electrode assembly. Axial confinement in the multipole electrode assembly can be provided by applying a DC potential to the end electrodes at opposite ends of the multipole electrode assembly. Ions confined within the ion trap can be accumulated and cooled for injection into an associated mass analyzer.

[0004] Typically, ions confined in an ion trap are cooled to the central axis of the trap through collisions with a buffer gas (such as nitrogen or helium). Thermalization of the ions is usually achieved after multiple oscillations along the trap's axis between the ions and a delayed electrostatic field generated by a DC potential applied to the end electrodes. When thermal equilibrium is reached with the buffer gas, ions can be extracted from the ion trap by applying an additional DC field.

[0005] One problem with this arrangement is that, in order to confine the ions within the ion trap, the ions must be cooled after implantation. Specifically, the ions must be sufficiently cooled as they travel along the axial direction of the ion trap so that they are cool enough to be reflected by the end DC potential.

[0006] One known option for providing the required cooling is to increase the pressure within the ion trap. However, increasing the pressure within the ion trap can lead to ion scattering and fragmentation.

[0007] Another option is to increase the length of the ion trap, so that the increased travel time along the ion trap provides an additional time for ion cooling. However, this solution increases the length of the cooled ion cloud in the axial direction. Increasing the size of the cooled ion cloud is not desirable because such a cloud is mismatched with the spatial acceptor properties of the mass analyzer.

[0008] Another option for improving ion confinement is disclosed in EP-A-3462476. EP-A-3462476 discloses an ion trap in which the pore voltage is increased after all ions have entered the trap. This allows the creation of an axial trapping barrier that ions do not have to overcome first, thus allowing ions to enter the trap with less energy and requiring less cooling / gas pressure to remain within the trap.

[0009] GB-A-2570435 discloses another option for improving ion confinement. GB-A-2570435 discloses an ion trap comprising an auxiliary needle-shaped electrode positioned toward the center of the ion trap. A DC potential of opposite polarity is applied to the needle-shaped electrode to confine ions within the ion trap region surrounding the needle-shaped electrode.

[0010] In view of the above, one object of this disclosure is to provide an improved ion trap, or at least one commercially useful alternative. Summary of the Invention

[0011] According to a first aspect of this disclosure, an ion trap is provided for cooling ions of a first polarity for mass spectrometry analysis. The ion trap includes a multipolar electrode assembly, a first confinement electrode, and a second confinement electrode. The multipolar electrode assembly is configured to confine ions of the first polarity within an ion channel extending in an axial direction along the multipolar electrode assembly. The first confinement electrode is disposed adjacent to the multipolar electrode assembly and extends in the axial direction of the multipolar electrode assembly. The second confinement electrode is disposed adjacent to the multipolar electrode assembly and extends in the axial direction of the multipolar electrode assembly aligned with the first confinement electrode. The first and second confinement electrodes are spaced apart in the axial direction to define an ion confinement region of the ion channel between the first and second confinement electrodes. The first and second confinement electrodes are configured to receive a DC potential of the first polarity to further confine ions within the ion confinement region of the ion channel.

[0012] The ion trap of the first aspect of this disclosure provides first and second confinement electrodes that confine ions to an ion-confining region of the ion channel between the first and second confinement electrodes using a repulsive DC potential (i.e., the DC potential has the same polarity as the ion). The applied DC potential provides a method for cooling ions and confining them to the ion-confining region of the ion trap. Therefore, the length of the ion-confining region of the ion trap is not determined by the length of the multi-electrode assembly, but by the spacing between the first and second confinement electrodes. That is, the length of the ion trap is decoupled from the length of the ion-confining region.

[0013] The first and second confinement electrodes confine ions within a region (partial) of the ion channel (i.e., the ion confinement region) along the axial length of the ion channel. That is, the axial length of the ion confinement region is shorter than the length of the ion channel (e.g., the length of the multi-electrode assembly). By using the first and second confinement electrodes to define the ion confinement region within the ion trap, the length of the ion trap (i.e., the length of the ion channel defined by the multi-electrode assembly) can be increased to allow additional time to cool ions traveling within the ion trap without adversely affecting the length of the ion confinement region.

[0014] It should be understood that when ions are confined in the confinement region of the ion trap, the space charge of the confined ions increases. This increase in space charge effectively has an associated voltage potential present in the ion confinement region of the ion trap. Advantageously, in the ion trap of the first aspect, the first and second confinement electrodes are not aligned with, but spaced apart from, the ion confinement region of the ion trap. Therefore, the DC potential applied to the first and second confinement electrodes does not overlap with the voltage potential of the space charge. Thus, the increase in space charge due to the increased ion confinement in the ion confinement region does not interfere with the trapping potential applied to the first and second confinement electrodes, because the first and second confinement electrodes do not overlap with the ion confinement region.

[0015] Furthermore, the first and second confinement electrodes of the first aspect are configured to receive a repulsive DC potential. By using a repulsive DC potential to confine the ions, for example, the potential field between the first confinement electrode and the adjacent electrode of the multi-electrode assembly does not trap the ions. In contrast, when using an attractive DC potential (as in the ion trap of GB-A-2570435), the inventors have realized that such a potential attracts ions in both the axial and radial directions. Therefore, ions not strongly contained by the RF pseudopotential, specifically, ions with a higher mass-to-charge ratio, experience a reduced confinement barrier in the radial direction of the DC needle electrode. Therefore, when using an attractive DC potential to confine ions, ions (specifically, high mass-to-charge ratio ions) may be attracted out of the ion trap and toward the DC needle electrode. By using a repulsive DC potential, the ion trap of the first aspect can confine ions with a wider range of mass-to-charge ratios without the possibility of radial ion loss.

[0016] In some embodiments, the ion trap is configured to cool analyte ions within the ion confinement region and then eject the cooled analyte ions into a mass analyzer for mass analysis. Therefore, the ion trap can be configured to operate as an extraction trap for forming ion packs to be injected into the mass analyzer.

[0017] In some embodiments, the first and second confinement electrodes are electrically connected together. Therefore, the first and second confinement electrodes can have the same DC potential applied to them. In some embodiments, the first and second confinement electrodes can be connected by a cable, while in other embodiments, the first and second electrodes can be integrally formed such that they are directly electrically connected to each other. Providing the first and second confinement electrodes with the same DC potential simplifies the control of the ion trap.

[0018] In some embodiments, the first and / or second confinement electrodes extend at least 2 mm in the axial direction. Therefore, the first and / or second confinement electrodes can be elongated confinement electrodes extending in the axial direction (i.e., the first and second confinement electrodes are elongated in the axial direction). In some embodiments, the first and / or second confinement electrodes can be elongated such that they extend a greater distance in the axial direction than they extend circumferentially around the central axis of the ion channel. By providing the first and / or second confinement electrodes extending in the axial direction, the first and / or second confinement electrodes can provide a DC potential that focuses ions toward the ion confinement region.

[0019] In some embodiments, the first confinement electrode and / or the second electrode are spaced a variable distance from the central axis of the ion channel. It should be understood that the first and / or second confinement electrodes may protrude or recess relative to the electrodes of the multipolar electrode assembly in the radial direction of the ions. Therefore, the radial spacing of the first and / or second confinement electrodes may vary along the axial direction of the ion trap, while the radial spacing of the electrodes of the multipolar electrode assembly may be substantially constant along the axial direction of the ion trap. By providing a variable radial spacing for the first and / or second confinement electrodes, the first and / or second confinement electrodes can be further configured to focus ions toward the ion confinement region of the ion trap.

[0020] In some embodiments, the spacing between the first and / or second electrodes and the central axis of the ion channel increases from the end of the multi-electrode assembly toward the ion confinement region of the ion channel. Therefore, the first and / or second confinement electrodes are typically recessed toward the ion confinement channel. In some embodiments, the variable spacing of the first and / or second confinement electrodes can be provided by forming the respective electrodes as generally wedge-shaped electrodes. By providing the first and / or second confinement electrodes in this way, the ion trap can provide a repulsive DC potential that guides ions toward the ion confinement region.

[0021] In some embodiments, a plurality of first confinement electrodes are provided, uniformly distributed around the central axis of the multi-electrode assembly, and a plurality of second confinement electrodes are provided, uniformly distributed around the central axis of the multi-electrode assembly. Each of the first confinement electrodes may be aligned with a corresponding second confinement electrode in the axial direction. In some embodiments, the plurality of first confinement electrodes may be provided in pairs, each pair arranged on opposite sides of the ion trap. In some embodiments, the plurality of second confinement electrodes may be provided in pairs, each pair arranged on opposite sides of the ion trap. For example, at least two, four, six, or eight first and / or second confinement electrodes may be provided.

[0022] In some embodiments, the first and second confinement electrodes are provided by slotted electrodes arranged in the axial direction, the slotted electrodes including a first confinement electrode region and a second confinement electrode region separated by a groove formed in the slotted electrode, the groove being aligned with the ion confinement region of the ion channel. Therefore, the first and second confinement electrodes can be provided in an integrated manner. The groove is provided to ensure that the DC potential applied to the slotted electrode does not affect the ion confinement region. In some embodiments, the length of the groove of the slotted electrode is approximately the same as the intended size of the ion confinement region.

[0023] In some embodiments, the slotted electrode is a plate-shaped electrode. Therefore, the slotted electrode can be provided economically, and can be easily integrated into the multi-electrode assembly. For example, the slotted electrode can be arranged between adjacent electrodes of the multi-electrode assembly.

[0024] In some embodiments, a plurality of slotted electrodes may be provided. In some embodiments, the plurality of slotted electrodes are uniformly distributed around the central axis of the multi-electrode assembly. In some embodiments, the plurality of slotted electrodes may be provided in pairs, each pair being arranged on opposite sides of the ion trap. For example, at least two, four, six, or eight slotted electrodes may be provided.

[0025] In some embodiments, the ion trap further includes first and second end electrodes disposed at opposite ends of the multipolar electrode assembly. The first and second end electrodes can be used to control the injection of ions into and / or extraction of ions from the ion trap in the axial direction. In other embodiments, the multipolar electrode assembly, combined with the first and second limiting electrodes, can be used to control ion injection into the ion trap. For example, the first and second limiting electrodes may also be individually controllable to eject ions from the ion trap in the axial direction (e.g., by applying a potential across the first and second limiting electrodes). In some embodiments, an ion transport device adjacent to the ion trap (e.g., another ion trap, multipolar or fragmentation chamber, etc.) can be used to control ion injection into / ejection from the ion trap.

[0026] In some embodiments, the ion trap may further include a controller. The controller may be configured to apply an RF potential to the multipolar electrode assembly to confine ions within the ion channel. The controller may also be configured to apply a first DC potential to the first and second end electrodes. The controller may further be configured to apply a second DC potential to the first and second confinement electrodes. Thus, the RF potential and the first and second DC potentials of the ion trap can be controlled by the controller to confine ions within the ion confinement region. The controller may also be configured to control the first DC potential applied to the end electrodes of the ion trap. The first DC potential applied to the end electrodes can be controlled to allow ions to be injected into the ion trap and subsequently confined within it. Then, the second DC potential applied to the first and second confinement electrodes can further confine ions within the ion confinement region of the ion trap.

[0027] In some embodiments, the first DC potential is greater than the second DC potential. Therefore, the combination of the first and second DC potentials defines an electrostatic field that focuses ions toward the ion confinement region between the first and second confinement electrodes.

[0028] In some embodiments, the controller is configured to apply a second DC potential to the first and second confinement electrodes during a first time period when ions enter the ion trap, and to apply a third DC potential to the first and second confinement electrodes during a second time period after ions have entered the trap, wherein the third DC potential is greater than the second DC potential. Therefore, the effectiveness of the first and second confinement electrodes may be reduced during the first time period when ions are implanted into the ion trap. After ions are implanted into the ion trap and cooling begins, the DC potential applied to the first and second confinement electrodes can be increased to enhance the confinement effect. For example, in some embodiments, the second DC potential may be a relatively low DC potential, such as no greater than 2V, or even 0V. After ions have been implanted into the ion trap, the second DC potential can then be increased to the third potential, such as at least 10V. In some embodiments, the second time period for applying the third DC potential may begin immediately after ions have completed entering the ion trap. In some embodiments, a delay may exist between the first and second time periods to allow the implanted ions to cool in the ion trap. For example, there may be a delay of at least 0.5 milliseconds, or more preferably at least 1 millisecond, or at least 2 milliseconds between the first time period and the second time period, to allow ions to begin cooling toward the ion-confining region. In some embodiments, the delay may be no greater than 10 milliseconds, so that the time spent confining the ions does not become excessive.

[0029] In some embodiments, the multi-electrode assembly is a quadrupole, hexapole, or octapole assembly. The multi-electrode assembly may include multiple pole pairs, each pole pair extending in the axial direction. The first and second limiting electrodes may be arranged between adjacent electrodes of the multi-electrode assembly (e.g., between adjacent poles).

[0030] According to a second aspect of this disclosure, a mass spectrometer is provided. The mass spectrometer includes an ion trap according to a first aspect, and a mass analyzer configured to receive ions from the ion trap. The ion trap of the mass spectrometer may incorporate any optional features discussed above with respect to the first aspect. The mass analyzer can receive ions that have already been cooled in the ion trap of the first aspect.

[0031] According to a third aspect of this disclosure, a method for implanting ions into an ion trap is provided. The method includes:

[0032] Ions of a first polarity are injected into the multipolar electrode assembly of the ion trap, wherein the ions are confined in an ion channel extending along the axial direction of the multipolar electrode assembly.

[0033] The ion trap further includes:

[0034] A first limiting electrode is disposed adjacent to the multi-electrode assembly and extends in the axial direction of the multi-electrode assembly;

[0035] A second limiting electrode is disposed adjacent to the multi-pole electrode assembly and extends in the axial direction of the multi-pole electrode assembly aligned with the first limiting electrode.

[0036] The first and second confinement electrodes are spaced apart in the axial direction to define an ion confinement region of the ion channel between the first and second confinement electrodes.

[0037] The ions are further confined in the ion confinement region of the ion channel by applying a DC potential of the first polarity to the first and second confinement electrodes to bias the ions within the ion channel toward the ion confinement region.

[0038] According to a third aspect of this disclosure, a method for implanting ions into an ion trap is provided. The method of the third aspect can be performed using either the ion trap of the first aspect or the mass spectrometer of the second aspect. The method of the third aspect provides a way to implant ions into an ion trap, wherein the ions are cooled and confined within an ion-confined region independent of the total length of the ion trap. By cooling the ions in this manner, the ions can then be used for further analysis, for example, by injecting the ions into a mass analyzer.

[0039] In some embodiments, the ion trap is confined within the ion channel of the multipolar electrode assembly by first and second end electrodes arranged at opposite ends of the multipolar electrode assembly.

[0040] In some embodiments, an RF potential is applied to the multipolar electrode assembly to confine ions within the ion channel. In some embodiments, a first DC potential is applied to the first and second terminal electrodes to confine ions within the ion channel. In some embodiments, a first DC potential is applied to the first and second confinement electrodes.

[0041] In some embodiments, during a first time period when ions enter the ion trap, a second DC potential is applied to the first and second confinement electrodes. Then, during a second time period after ions have entered the trap, a third DC potential is applied to the first and second confinement electrodes, wherein the third DC potential is greater than the second DC potential. Attached Figure Description

[0042] This invention can be practiced in many ways, but specific embodiments will now be described by way of example only and with reference to the accompanying drawings, in which:

[0043] Figure 1 shows an example of an ion trap known in GB-A-2570435;

[0044] - Figure 2 A schematic arrangement of a mass spectrometer according to an embodiment of the present disclosure is shown;

[0045] - Figure 3 A schematic diagram of an ion trap according to an embodiment of the present disclosure is shown;

[0046] - Figure 4 A schematic diagram showing the ion's travel relative to the ion potential in the axial direction of the ion trap is shown.

[0047] - Figure 5a The graph shows the potential variation in the radial direction transverse to the axial direction in the ion trap;

[0048] - Figure 5b The graph shows the potential variation along the axial direction of the ion trap.

[0049] - Figure 6 A schematic diagram of a pair of slotted electrodes is shown;

[0050] - Figure 7a The mass analysis scan curves of a mass spectrometer equipped with an ion trap of GB-A-2570435 are shown.

[0051] - Figure 7b A mass analysis scan curve of a mass spectrometer incorporating an ion trap according to an embodiment of the present disclosure is shown.

[0052] - Figure 8 A flowchart of a method for implanting ions into an ion trap according to an embodiment of the present disclosure is shown. Detailed Implementation

[0053] Figure 2 A schematic arrangement of a mass spectrometer 10 according to an embodiment of the present disclosure is shown.

[0054] exist Figure 2 In this process, the sample to be analyzed is supplied (e.g., from an autosampler) to chromatographic equipment, such as a liquid chromatography (LC) column. Figure 2(Not shown in the image). One such example of an LC column is the PROSWIFT (RTM) monolithic column from Thermo Fisher Scientific, Inc., which provides high-performance liquid chromatography (HPLC) by forcing a sample carried in the mobile phase through a stationary phase composed of irregular or spherical particles under high pressure. In an HPLC column, sample molecules elute at different rates depending on their degree of interaction with the stationary phase. For example, sample molecules can be proteins or peptides.

[0055] The sample molecules separated by liquid chromatography are then ionized using an electrospray ionization (ESI) source 20, which is at atmospheric pressure, to form sample ions.

[0056] Sample ions generated by ESI source 20 are transported to ion trap 80 via the ion transport device of mass spectrometer 10. According to the ion transport device, sample ions generated by ESI source 20 enter the vacuum chamber of mass spectrometer 10 and are guided by capillary 25 to an RF-only S-lens 30. The ions are focused by S-lens 30 into an injection flatapole 40, which injects ions into a curved flatapole 50 having an axial field. The curved flatapole 50 guides (charged) ions through it along a curved path, while undesirable neutral molecules, such as entrained solvent molecules, are not guided along the curved path and are lost. Ion gate 60 is located at the distal end of the curved flatapole 50 and controls the entry of ions from the curved flatapole 50 into the channel of transport multipole 70. Figure 2 In the illustrated embodiment, the transfer multipole 70 is a transfer octet. The transfer multipole 70 guides analyte ions from the bent flat electrode 50 into the ion trap 80. Figure 2 In the embodiment shown, the ion trap 80 is configured to cool ions for extraction into the mass analyzer 90.

[0057] It should be understood that the above-described ion transport device is one possible implementation of this embodiment for transporting ions from an ion source to an ion trap 80. Other arrangements of ion transport optics suitable for transporting ions from an ion source to an ion trap 80, or variations of the above-described assembly, will be apparent to those skilled in the art. For example, Figure 2 The ion transport device shown can be modified as needed or replaced with other ion optical elements. For example, at least one of the mass selectors, such as a quadrupole mass filter and / or a mass-selected ion trap, and / or an ion mobility separator, can be positioned, for example, between a bent flat pole 50 and a transfer multipole 70 to provide the ability to select ions from the ion source 20 and guide them into the ion trap 80.

[0058] Ion trap 80 is configured to confine and cool the injected ions. The detailed operation and construction of ion trap 80 will be explained below. Cooled ions confined in ion trap 80 can be ejected orthogonally from ion trap 80 toward mass analyzer 90. For example... Figure 2 As shown, the mass analyzer is an orbital capture mass analyzer 90, such as the Orbitrap (RTM) mass analyzer sold by Thermo Fisher Scientific. The orbital capture mass analyzer 90 is an example of a Fourier transform mass analyzer. The orbital capture mass analyzer 90 has an eccentric injection port in its outer electrode, and ions are injected into the orbital capture mass analyzer as coherent packets through said eccentric injection port. The ions are then captured within the orbital capture mass analyzer by a superlog-electrostatic field and move back and forth in the longitudinal direction while orbiting around the inner electrode. The axial component (more or less) of the ion packet motion in the orbital capture mass analyzer is defined as simple harmonic motion, where the angular frequency in the axial direction is related to the square root of the mass-to-charge ratio of a given ionic substance. Therefore, over time, the ions separate according to their mass-to-charge ratio.

[0059] In the above configuration, sample ions are analyzed by the orbital capture mass analyzer 90 without fragmentation. The resulting mass spectrum is denoted as MS1.

[0060] although Figure 2 The diagram illustrates an orbital trap mass analyzer 90, but other Fourier transform mass analyzers can be used instead. For example, a Fourier transform ion cyclotron resonance (FTICR) mass analyzer can be used as a mass analyzer. Other types of electrostatic traps can also be used as Fourier transform mass analyzers. Fourier transform mass analyzers, such as orbital trap mass analyzer 90 and ion cyclotron resonance mass analyzers, can also be used in this invention, even when using other types of signal processing besides Fourier transform to obtain mass spectrometry information from transient signals (see, for example, WO-A-2013 / 171313, Thermo Fisher Scientific). In other embodiments, the mass analyzer can be a time-of-flight (ToF) analyzer. The ToF mass analyzer can be a ToF with an extended flight path, such as a multi-reflection ToF mass analyzer.

[0061] In the second operating mode of the ion trap 80, ions entering the ion trap 80 via the transfer multi-electrode 70 can continue their path through the ion trap 80, exiting through the opposite axial end of the ion trap 80 to the end where the ions entered, thus allowing the ions to travel into the fragmentation chamber 100. The transport or trapping of ions by the ion trap 80 can be selected by adjusting the voltage applied to the end electrodes of the ion trap 80. Therefore, the ion trap 80 can also be effectively used as an ion guide in the second operating mode. Alternatively, ions trapped and cooled in the ion trap 80 can be ejected axially from the ion trap 80 into the fragmentation chamber 100. This ejection can be controlled by applying a suitable voltage to the end electrodes of the ion trap 80.

[0062] Fracture chamber 100 in Figure 2 The mass spectrometer 10 contains a high-energy collisional dissociation (HCD) device, which is supplied with collision gas. Sample ions arriving at the fragmentation chamber 100 collide with collision gas molecules, causing the sample ions to fragment into fragment ions. These fragment ions can be returned from the fragmentation chamber 100 to the ion trap 80 by applying an appropriate potential to the end electrodes of the fragmentation chamber 100 and the ion trap 80. The fragment ions can be cooled and confined in the extraction trap 80, and then ejected from the extraction trap 80 to the mass analyzer 90 or mass analyzer. The resulting mass spectrum is represented as MS2. For MS2 scans, a transfer octap can also be used to mass-filter sample ions before they are injected into the ion trap 80 and the fragmentation chamber 100. Therefore, the transfer octap 70 can also be a mass-resolved octap.

[0063] although Figure 2 The HCD fragmentation chamber 100 is shown, but other fragmentation devices can be used instead, such as collision-induced dissociation (CID), electro-capture dissociation (ECD), electro-transfer dissociation (ETD), photodissociation, etc.

[0064] Figure 3 A schematic diagram of an ion trap 200 according to an embodiment of the present disclosure is shown. The ion trap 200 has a linear geometry. Therefore, the ion trap 200 can be used to replace... Figure 2 The ion trap 80 is shown in the mass spectrometer. It should be understood that the ion trap 200 may be provided in a linear form as shown, or alternatively, in a curved form similar to a C-shaped trap.

[0065] Figure 3The ion trap 200 includes a first end electrode 210, a second end electrode 212, a first confinement electrode 214, a second confinement electrode 216, and a multi-electrode assembly 220. The multi-electrode assembly 220, the first confinement electrode 214, and the second confinement electrode 216 are arranged between the first end electrode 210 and the second end electrode 212. In this example, the first end electrode 210 and the second end electrode 212 are in the form of plate electrodes. Each of the first end electrode 210 and the second end electrode 212 has ion holes 211, 213 disposed at its center for ion transport. For example, ions can axially enter and / or exit the ion trap 200 through the ion hole 211 in the first end electrode 210 or through the ion hole 213 in the second end electrode 212.

[0066] Figure 3 The illustrated multipolar electrode assembly 220 includes a plurality of elongated electrodes arranged around a central axis to define an elongated ion channel. The multipolar electrode assembly includes an elongated driving electrode 222 and opposing elongated traction electrodes 224. The elongated driving electrode 222 and elongated traction electrode 224 are spaced apart on opposite sides of the elongated ion channel. The elongated driving electrode 222 and elongated traction electrode 224 are substantially parallel to each other and aligned along the length of the elongated ion channel. Figure 3 As shown, the elongated pushing electrode 222 and the elongated traction electrode 224 have substantially flat opposing surfaces. In some embodiments, the opposing surfaces may have a hyperbolic profile. The elongated traction electrode 224 includes a traction electrode aperture 225 at a point along its length. Figure 3 As shown, the traction electrode hole 225 is located in the relatively central region of the elongated traction electrode 224. The traction electrode hole 225 extends through the thickness of the electrode and provides a path for ions to exit the ion trap 200 in a direction generally transverse to the axial direction of the ion trap 200. In this way, ions can be extracted from the ion trap 200 in a direction toward and into the mass analyzer 90, as... Figure 2 As shown. As discussed further below, the traction electrode aperture 225 can be aligned to coincide with the ion confinement region of the ion trap 200.

[0067] The multi-electrode assembly also includes first elongated split electrodes 226, 228 and second elongated split electrodes 230, 232. The first elongated split electrodes 226, 228 are spaced apart from the second elongated split electrodes 230, 232 on opposite sides of the elongated ion channel. The first elongated split electrodes 226, 228 and the second elongated split electrodes 230, 232 are substantially parallel to each other along the length of the elongated ion channel. The first elongated split electrodes 226, 228 and the second elongated split electrodes 230, 232 are spaced apart across the elongated ion channel in a direction transverse to the direction in which the elongated push electrode 222 and the elongated pull electrode 224 are spaced apart. Therefore, the first elongated split electrodes 226, 228 and the second elongated split electrodes 230, 232, the elongated push electrode 222 and the elongated pull electrode 224 define the boundaries for the elongated ion channel having a generally rectangular cross-section.

[0068] The first elongated split electrodes 226 and 228 can be formed by two elongated rod-shaped electrodes. The two elongated rod-shaped electrodes are spaced apart, such that the first and second confinement electrodes can be disposed between the two first elongated split electrodes. The two elongated rod-shaped electrodes can be aligned parallel to each other along the length of the ion channel.

[0069] The second slender split electrodes 230 and 232 can also be formed from two slender rod-shaped electrodes. For example... Figure 3 As shown, the two second elongated split electrodes 230 and 232 are spaced apart, so that the first and second limiting electrodes can be disposed in the region between the two elongated split electrodes 230 and 232.

[0070] like Figure 3 As shown, it should be understood that the elongated driving electrode 222, the elongated traction electrode 224, the first elongated splitting electrode 226, 228 and the second elongated splitting electrode 230, 232 are arranged to form a quadrupole ion trap.

[0071] The multi-electrode assembly 220 is configured to confine ions in the radial direction of the ion trap. The elongated multi-electrode assembly 220 is configured to receive a variable RF potential to confine ions. A variable RF potential can be applied across opposing elongated electrode pairs of the multi-electrode assembly 220 to form a pseudopotential trap. For example, according to one embodiment, the multi-electrode assembly 220 can be arranged to apply an RF potential to the elongated ion channel with an amplitude of at least 10V, more preferably at least 50V, and no greater than 10,000V, more preferably no greater than 5,000V (centered at 0V). Of course, those skilled in the art will understand that the exact RF potential amplitude and frequency can vary depending on the configuration of the multi-electrode assembly 220 and the ions to be confined. For example, in some embodiments, a sinusoidal voltage varying in amplitude at a frequency of 4.5MHz and an amplitude of 1000V can be supplied to the multi-electrode assembly 220.

[0072] The elongated electrodes of the multi-electrode assembly 220 may also have a DC potential applied thereto. Preferably, the DC potential of the elongated electrodes is 0V.

[0073] The multi-electrode assembly 220 extends between the first end electrode 210 and the second end electrode 212. The total length of the ion trap (i.e., the distance between the first end electrode 210 and the second end electrode 212) can be at least 20 mm. Such a length allows time for the ions to cool as they travel along the ion trap. The total length of the ion trap can also typically not exceed 300 mm, as lengths exceeding this may not be particularly space-efficient.

[0074] The multi-electrode assembly 220 defines an ion channel extending along the axial direction of the ion trap 80. Typically, the multi-electrode assembly 220 is arranged around the axial direction of the ion trap to define an ion channel having a radius of at least 1 mm (around the central axis). Typically, the ion channel has a radius no greater than about 10 mm, but a larger radius can be provided if desired. For example, Figure 3 The ion trap has a total length of approximately 80 mm and a radius of 2 mm.

[0075] The ion trap 80 is housed within a vacuum chamber. Typically, the vacuum chamber is equipped with an inert gas to provide a means of cooling the ions within the ion trap. Figure 2 In one embodiment, the ion trap 80 is disposed within a vacuum chamber, the vacuum chamber comprising approximately 10 - 4 mbar to 10 -2 N2 at mbar pressure.

[0076] like Figure 3 As shown, the first confinement electrode 214 and the second confinement electrode 216 can each be configured as elongated electrodes substantially parallel and aligned with the elongated ion channel and the second elongated split electrodes 230, 232. The first confinement electrode 214 and the second confinement electrode 216 are positioned on opposite sides of the ion confinement region of the elongated ion channel. Figure 3 In this embodiment, the ion confinement region of the elongated ion channel is the central region of the elongated ion channel. Therefore, the first confinement electrode 214 and the second confinement electrode 216 are spaced apart from each other on either side of the central region of the elongated ion channel so as to define an ion confinement region between the first confinement electrode 214 and the second confinement electrode 216.

[0077] The first confinement electrode 214 and the second confinement electrode 216 are configured to receive a DC potential with the same polarity as the ions to be confined within the ion trap 80. Therefore, when the DC potential is applied, the first confinement electrode 214 and the second confinement electrode 216 generate a repulsive potential that directs ions toward the central region of the ion channel, thereby confining the ions within the ion confinement region of the elongated ion channel. The DC potential applied to the first confinement electrode 214 and the second confinement electrode 216 is described in more detail below.

[0078] Figure 3 The first limiting electrode 214 and the second limiting electrode 216 shown are each elongated electrodes that extend in the axial direction of the ion trap 200. Therefore, each elongated electrode is aligned with an electrode of the multi-electrode assembly 220. Each elongated electrode may extend at least 2 mm in the axial direction. In some embodiments, the elongated electrodes extend at least 5 mm, 10 mm, 20 mm, or 50 mm. In some embodiments, the elongated electrodes may extend at least 10% of the total length of the ion trap 200 (i.e., the distance between the first end electrode 210 and the second end electrode 212).

[0079] An ion-confining region extends between the first and second confinement electrodes of the ion trap 200. Therefore, the axial length of the ion-confining region depends on the spacing between the first confinement electrode 214 and the second confinement electrode 216. In some embodiments, the ion-confining region may extend at least 2 mm in the axial direction. An ion-confining region that is too short may experience significant space charge effects or have limited ion confinement capability. In some embodiments, the axial length of the ion-confining region is at least 10% of the total length of the ion trap (between the end electrodes). For example, in some embodiments, the axial length of the ion trap may be at least 2 mm, 3 mm, 5 mm, or 10 mm. In some embodiments, the axial length of the ion-confining region may not exceed 20% of the total length of the ion trap. For example, the axial length may not exceed 20 mm, 15 mm, or 12 mm.

[0080] exist Figure 3 In this embodiment, the first and second confinement electrodes are configured as rod-shaped electrodes. It should be understood, of course, that the first and second confinement electrodes can be configured in any suitable shape to provide a repulsive DC potential on either side of the ion confinement region.

[0081] For example, Figure 6 Another example of a slotted electrode 218 that can be used to provide a first limiting electrode 214 and a second limiting electrode 216 is shown. Figure 6As shown, the slotted electrode 218 includes a region defining a first confinement electrode 214 (first confinement electrode region) and a region defining a second confinement electrode 216 (second confinement electrode region). The first confinement electrode region and the second confinement electrode region are separated by a groove 217 formed in the slotted electrode 218, wherein the groove 217 is aligned with the ion confinement region (extraction region) of the ion channel.

[0082] The slotted electrode 218 can be configured as a substantially planar electrode (i.e., a plate-shaped electrode). The slotted electrode 218 can be configured in a manner similar to... Figure 3 In the illustrated embodiment, the first limiting electrode 214 and the second limiting electrode 216 are disposed between the electrodes of the multi-electrode assembly 220. For example... Figure 6 As shown, a pair of slotted electrodes 218 can be disposed on opposite sides of the ion trap 200.

[0083] The slotted electrode 218 can be arranged in the ion trap such that the slots 217 are aligned in a direction generally transverse to the axial direction. For example, if the slotted electrode is a plate-shaped electrode, the plate can be arranged along a plane intersecting the central axis of the ion trap. The slotted electrode 218 can be positioned relative to the central axis of the ion trap such that the first limiting electrode 214 and the second limiting electrode 216 are positioned at similar distances from the central axis to the electrodes of the multi-electrode assembly 220. For example, in Figure 6 In one example, the multi-electrode assembly 220 can be located approximately 2 mm from the central axis in the radial direction. Therefore, in the region facing the ion confinement region, the first confinement electrode 214 and the second confinement electrode 216 are positioned at distances similar to those of the electrodes of the multi-electrode assembly 220 from the central axis. Figure 6 It can be seen that the first and second confinement electrodes can extend a variable amount in the radial direction along the axial direction of the ion trap. Therefore, the distance between the first confinement electrode 214 and / or the second electrode 216 and the central axis of the ion channel can vary along the length of the ion trap. Figure 6 In one embodiment, the distance between the first limiting electrode 214 and the second limiting electrode 216 and the central axis increases axially from the end of the multi-electrode assembly toward the ion-limiting region of the ion channel.

[0084] For example, in Figure 6 In one example, the first confinement electrode 214 is spaced 1.85 mm from the central axis at the end of the slotted electrode closest to the first end electrode 210. The spacing of the first confinement electrodes 218 increases by up to 2 mm toward the ion confinement region. Therefore, the first confinement electrode region of the slotted electrode is typically wedge-shaped. In some embodiments, the spacing may vary linearly, or, as... Figure 6As shown, this is a combination of linear gradients and constant spacing segments. In other embodiments, other variable spacing distributions may be provided, including one or more segments of: constant spacing, linear gradients, nonlinear gradients such as curves, or exponential gradients. This variable spacing helps guide ions toward the ion confinement region because a DC potential is applied closer to the central axis of the ion trap in regions further away from the ion confinement region.

[0085] The second confinement electrode 216 also has a different spacing from the central axis of the ion trap. In some embodiments, the spacing can be varied in a similar manner to that of the first confinement electrode, while... Figure 6 In the examples, the variable spacing is different. For example... Figure 6 As shown, the distance from the end of the slotted electrode 218 closest to the second end electrode 212 to the central axis is 1.5 mm, while the distance closest to the ion confinement region is 2 mm. Therefore, the second confinement electrode region of the slotted electrode is typically wedge-shaped.

[0086] In the groove 217 region of the slotted electrode, the groove 217 is configured such that the material of the slotted electrode is recessed in the radial direction. The groove 217 of the slotted electrode 218 is configured such that any material of the slotted electrode 218 is recessed at least 3 mm from the central axis of the ion confinement region. Therefore, the groove has a depth of at least 1 mm relative to the first and second confinement electrode regions.

[0087] The slot 217 of the slotted electrode 218 corresponds to the axial length of the ion confinement region. Figure 6 In the slotted electrode, the slotted electrode 218 has a slot 217 extending 10 mm in the axial direction. Figure 6 In one embodiment, the slotted electrode is positioned closer to the second end electrode 212 than the first end electrode 210.

[0088] like Figure 6 As shown, a pair of slotted electrodes is provided. The pair of slotted electrodes are disposed on opposite sides of the ion channel. The slots 217 of each slotted electrode 218 are aligned on opposite sides of the ion confinement region.

[0089] Therefore, the slotted electrode 218 can be used to provide the first confinement electrode 214 and the second confinement electrode 216 in a space-saving design. The first confinement electrode 214 and the second confinement electrode 216 can also be provided with a variable spacing relative to the central axis of the ion trap to improve the focusing of ions toward the ion confinement region of the ion trap.

[0090] Next, refer to Figure 2 The mass spectrometer 10 shown and Figure 3 The ion trap 200 shown illustrates a method for implanting ions into the ion trap. A flowchart of the method 100 for implanting ions into the ion trap is shown below. Figure 8 As shown.

[0091] Under the control of a controller (not shown), the mass spectrometer 10 is configured, for example, to control the generation of sample ions in the ESI source 20 to set an appropriate potential on the electrodes of the ion transport device, thereby guiding, focusing, and filtering (wherein the ion transport device includes a mass selector) the sample ions to capture mass spectrometry data from the mass analyzer 90, etc. It should be understood that the controller may include a computer that can operate according to a computer program including instructions to cause the mass spectrometer 10 to perform the steps described according to this disclosure.

[0092] It should be understood that Figure 2 The specific arrangement of the components shown is not required for the method described herein. In fact, other mass spectrometer arrangements may be suitable for performing the method of implanting ions into ion traps 80, 200, according to this disclosure. According to embodiments of the method, sample molecules are provided by an LC column, which is part of the aforementioned apparatus. In some embodiments, sample molecules may be supplied from the LC column for a duration corresponding to the duration of the chromatographic peak of the sample supplied from the LC column. Therefore, the controller can be configured to perform the method within a time period corresponding to the width (duration) of the chromatographic peak at its base.

[0093] like Figure 2 As shown, the orbital trap mass analyzer 90 is used to perform mass analysis on sample ions implanted into the ion trap 80. To implant ions into the ion trap, sample molecules from the LC column are ionized using an ESI source 20 to generate sample ions. The ESI source 20 can be controlled by a controller to generate sample ions with a first charge. The first charge can be positive or negative. According to the method described herein, the sample ions are positively charged (i.e., have positive polarity).

[0094] The sample ions then enter the vacuum chamber of the mass spectrometer 10. The sample ions are guided through the capillary 25, the RF-only S-lens 30, the implantation flat electrode 40, the bent flat electrode 50, and into the transport multi-electrode 70 as described above. The sample ions can then enter the ion trap 80, where they are accumulated. Therefore, sample ions with a first charge can be transported to and implanted into the ion trap 80 according to the steps described above. Thus, in the first step 101 of method 100, ions of a first polarity are implanted into the ion trap 80.

[0095] Next, we will refer to Figure 3 The control of ion trap 80 is described in more detail below for ion trap 200.

[0096] During a first time period, the controller controls the ion transport device to allow ions to enter ion traps 80 and 200. During this first time period, the controller can be configured to apply a first DC potential to the first end electrode 210 and the second end electrode 212, such that the injected ions are confined within the ion channel of the ion trap 200. During the first time period, the first DC potential applied to the first end electrode 210 and the second end electrode 212 may have the same polarity as the injected ions, thus confining the ions within the ion trap. In some embodiments, during the first time period, an initial DC potential may be applied to the end electrode through which the ions enter (e.g., the first end electrode 210), said initial DC potential being lower than the first DC potential applied to the opposite end electrode, while the ions travel through the aperture of the electrode. Then, after the ions have entered the ion trap 200 through the aperture 211 shown in the first end electrode 210, the first DC potential may be applied to the first end electrode 210.

[0097] For example, in some embodiments, the initial DC potential applied to the first end electrode 210 may be 0V as ions travel through it. Then, after all ions have entered the ion trap 200, but before any ions have had time to reflect off the second end electrode 212 and travel back to the first end electrode 210, a first DC potential may be applied to the first end electrode 210. The first DC potential applied to the first end electrode 210 and the second end electrode 212 has the same charge as the sample ions. Therefore, for positively charged ions, the controller is configured to apply a positive first DC potential to the first end electrode 210 and the second end electrode 212 to confine the positively charged sample ions during a first time period. The first DC potential applied to the first end electrode 210 and the second end electrode 212 is used to repel sample ions in the axial direction toward the central region of the elongated ion channel. Thus, the sample ions are initially confined by the first DC potential applied to the first end electrode 210 and the second end electrode 212. For example, the first DC potential applied to the first end electrode 210 and the second end electrode 212 may be +10V.

[0098] During the initial time period when ions enter the ion traps 80 and 200, the ions can have relatively high energy. Although a DC potential can be applied to the first and second confinement electrodes during the initial implantation, due to the relatively high energy of the ions, in some embodiments, the second DC potential applied to the first confinement electrode 214 and the second confinement electrode 216 may be relatively small, or even zero, when the ions enter the ion trap. This allows the ions entering the ion trap to initially travel the full length of the ion trap, which facilitates ion cooling. Once the ions have entered the trap and cooling has begun, the second DC potential applied to the first confinement electrode 214 and the second confinement electrode 216 can then be increased to a third DC potential to confine the ions within the ion confinement region. For example, during the first time period, the second DC potential applied to the first confinement electrode 214 and the second confinement electrode 216 may be 0V. In some embodiments, the second DC potential may be less than the first DC potential applied to the first terminal electrode 210 and the second terminal electrode 212. For example, the second DC potential may not be greater than: 70%, 50%, 30%, 20%, or 10% of the first DC potential. In some embodiments, the second DC potential may not exceed 7V, 5V, 3V, 2V, or 1V. Therefore, in step 102 of method 100, one or more DC potentials may be applied to the first and second confinement electrodes to confine ions within the ion trap.

[0099] The controller is also configured to apply an RF potential to the multi-electrode assembly 220, thereby forming a pseudopotential well in the elongated ion channel. In some embodiments, the frequency of the RF potential may be at least 3 MHz, and the RF potential may oscillate between, for example, -500V and +500V.

[0100] The first time period provides the duration for which ions are implanted into ion traps 80 and 200. The duration of the first time period will depend on the number of ions to be implanted into the ion trap. The duration of the first time period may also depend on the length of the ion trap and the time it takes for ions to travel along the length of the ion trap and reflect back to the end electrode where the ion entered the ion trap. In some embodiments, it may be desirable that the first time period is no longer than the time it takes for ions to travel along the ion trap and return to the end electrode where the ion entered the ion trap. For example, the first time period may have a duration of at least 100 microseconds, 200 microseconds, 500 microseconds, or 1 millisecond to allow a suitable number of ions to enter the ion trap. In some embodiments, the first time period may have a duration of no more than 10 milliseconds, 5 milliseconds, 3 milliseconds, or 2 milliseconds.

[0101] Once the ion implantation process is complete, the controller is configured to control the ion trap to cool the ions and confine them within the ion-confined region of the ion trap. Following the ion implantation process, the ions are relatively high in energy, causing them to travel between the first and second end electrodes, limited by a first DC potential applied to the first end electrode 210 and the second end electrode 212. An example of the initial ion movement is shown in… Figure 4 The curve in the graph.

[0102] Once the ions are confined between the first end electrode 210 and the second end electrode 212, the controller is configured to apply a third DC potential to the first confinement electrode 214 and the second confinement electrode 216 during a second time period to further confine the ions. The second time period may immediately follow the first time period when the ions enter the ion trap (i.e., the second time period begins when the ions have finished entering the ion trap). In some embodiments, a short cooling period may exist between the first and second time periods to allow the ions to cool further within the trap. The duration of the cooling period may not exceed, for example, 2 milliseconds, so that the total duration of ion cooling in the ion trap does not become excessively long. Thus, during step 103 of method 100, the ions can be cooled within the ion confinement region of the ion trap.

[0103] During the second time period, a first DC potential applied to the first confinement electrode 214 and the second confinement electrode 216 can be provided independently of a third DC potential applied to the first confinement electrode 214 and the second confinement electrode 216. A third DC potential applied to the first confinement electrode 214 and the second confinement electrode 216 is provided to confine sample ions within the ion confinement region of the elongated ion channel. The third DC potential has the same sample polarity as the ions. Because ions in the second time period typically cool towards the center of the ion trap (away from the end electrodes), the third DC potential applied to the first and second confinement electrodes repels ions from the first confinement electrode 214 and the second confinement electrode 216 towards the ion confinement region of the elongated ion channel. Figure 4 It is further shown how applying a third DC potential to the first and second limiting electrodes increases ion confinement in the ion-confined region of the ion trap.

[0104] In some embodiments, the third DC potential applied to the first and second confinement electrodes is the same as the second DC potential. Preferably, the magnitude of the third DC potential applied to the first and second confinement electrodes is increased relative to the second DC potential applied in the first time period. By increasing the DC potential applied to the first and second confinement electrodes in the second time period, ion confinement can be increased without adversely affecting ion capture in regions far from the ion confinement region, since ions are typically already confined within the ion confinement region. That is, increasing the DC potential on the first confinement electrode 214 and the second confinement electrode 216 may cause the capture pseudopotential to deviate from the ion confinement region, thus reducing the effect on ion retention in the ion trap. For example, in some embodiments, the third DC potential applied to the first end electrode 210 and the second end electrode 212 may be approximately +5V.

[0105] As mentioned above, Figure 4 A schematic diagram of ion movement in an ion trap is shown, where a DC potential is applied to the end electrode and the first confinement electrode 214 and the second confinement electrode 216. Figure 4 As shown, by applying second and third DC potentials to the first confinement electrode 214 and the second confinement electrode 216, a first potential well can be formed in the central region of the elongated ion channel, confining sample ions within the ion-confinement region of the elongated ion channel. Therefore, the first potential well can be formed relative to the DC potential of the multi-electrode assembly 220. The magnitude of the first potential well can be defined as the energy required for ions trapped at the bottom of the well to escape the potential well. The polarity of the potential well can be defined based on the polarity of the ions it is intended to confine. For example, a potential well with negative polarity will confine positive ions, while a potential well with positive polarity will confine negative ions.

[0106] Figure 4 A schematic diagram of the DC potential around the ion confinement region of the ion trap 200 along the ion trap axial direction is shown. Figure 4 As shown, a potential well is formed in the ion confinement region of the ion trap. The potential well extends in the axial direction of the elongated ion channel of the ion trap 200 to axially confine sample ions. The potential well formed between the first confinement electrode 214 and the second confinement electrode 216 can also be formed relative to the first end electrode 210 and the second end electrode 212. As... Figure 4As shown, the potential of the ion-confined region is the lowest point of the ion trap in the axial direction. This is due to the distance from the first and second end electrodes, and also due to the proximity of the first and second confinement electrodes to the ion-confined region. There is a steep, step-like change in DC potential between the first confinement electrode 214 and the second confinement electrode 216 near the ion-confined region, between the ion-confined region of the ion trap, and between the ion trap regions extending therefrom. Between the first ion-confined electrode and the first end electrode, the DC potential further increases towards the first end electrode due to the difference in DC potential (e.g., 5V for the first confinement electrode, 10V for the first end electrode).

[0107] like Figure 4 As shown, ions within the ion channel are initially confined between the first end electrode 210 and the second end electrode 212. As the ions cool within the ion channel, they lose energy and focus toward the ion-confining region. Once the ions are sufficiently cold, they no longer have the energy to escape the potential well of the ion-confining region, where they are further cooled and confined.

[0108] Figure 5a and 5b The diagram provides a further explanation of the effect of changing the DC potential applied to the first and second limiting electrodes of the ion trap 200 according to this disclosure. Figure 5a A graph is shown showing the pseudopotential traps formed along the radial direction (x direction) of the ion trap for different DC potentials (i.e., the second or third potential) applied to the first and second limiting electrodes. Figure 5a The graph shows that the pseudopotential well in the x-direction of the cross section along a point of the ion trap overlaps with one of the first confinement electrode 214 and the second confinement electrode 216. Figure 5b A graph is shown showing the pseudopotential well formed along the axial direction (z direction) of the ion trap for different DC potentials (i.e., the second or third potential) applied to the first and second limiting electrodes. Figure 5a and 5b The curve is a curve with Figure 5a and 5b The simulation results for the ion trap with the cross-section shown are presented. For ions with a mass-to-charge ratio of 500, Figure 5a and 5b The multi-electrode assembly 220 in the simulation has an RF potential of 500V at 3MHz.

[0109] like Figure 5aAs shown, increasing the DC potential applied to the first confinement electrode 214 and the second confinement electrode 216 reduces the depth of the pseudopotential trap in the radial direction of the ion trap. Therefore, it may be advantageous to reduce the DC potential applied to the first confinement electrode 214 and the second confinement electrode 216 (the second DC potential) when ions first enter the ion trap 200, since the ions may be relatively high-energy. Once the ions have begun to cool in the ion trap, the DC potential applied to the first confinement electrode 214 and the second confinement electrode 216 (the third DC potential) can be increased without adversely affecting the ion confinement in the radial direction. Figure 5b As shown, increasing the DC potential applied to the first and second confinement electrodes increases the depth of the potential well in the axial direction. Therefore, ions become increasingly confined within the ion-confinement region.

[0110] Therefore, the spatial distribution of ions within the ion trap 200 can be reduced by confining the ions within the ion-confinement region of the elongated ion channel using a potential trap. By confining the ions in the potential trap by applying a first DC potential to the first confinement electrode 214 and the second confinement electrode 216, it is no longer necessary to apply an initial DC potential to the first end electrode 210 and the second end electrode 212 to axially confine the sample ions within the ion trap 200. Thus, positively charged ions can be confined (axially and radially confined) within the elongated ion channel of the ion trap 200 by a combination of the first DC potential applied to the first end electrode 210 and the second end electrode 212, the second DC potential applied to the first confinement electrode 214 and the second confinement electrode 216 (and optionally a third DC potential), and the RF potential applied to the multi-electrode assembly 220.

[0111] By maintaining a second or third DC potential applied to the first confinement electrode 214 and the second confinement electrode 216, ions confined within the ion confinement region of the ion trap 200 can be stored within the ion trap. The ions stored within the ion trap 200 can then be ejected from the ion trap for further processing by the mass spectrometer 10 of FIG. 1. Ions can be ejected from the ion trap 200 through orifices 211 or 213 in the axial direction or through traction electrode orifices 225 in a direction transverse to the axial direction.

[0112] Ions can be ejected in the axial direction by applying a DC potential to the end electrode to guide ions through one of the holes 211 and 213.

[0113] Ion ejection can also be achieved by applying a pushing DC potential to the elongated pushing electrode 222 and a traction DC potential to the opposing traction electrode 224, thereby ejecting sample ions from the ion trap 200 through the traction electrode hole 225. The pushing DC potential is a DC potential configured to push (i.e., repel) ions, while the traction DC potential is a DC potential configured to attract (i.e., draw in) ions. Preferably, no RF potential is applied to the multi-electrode assembly 220 while sample ions are ejected from the ion trap 200. For example, for positive ions in the above method, the controller can be configured to apply a negative DC potential to the traction electrode 224 (e.g., -500V) and a positive DC potential (e.g., +500V) to the pushing electrode 222. Thus, positively charged sample ions can be ejected from the ion trap 200 through the hole 225 of the elongated traction electrode 224. By reducing the spatial distribution of sample ions before ejection from the ion trap 200, their spatial distribution can also be reduced when the sample ions are ejected from the ion trap 200. This results in improved transport efficiency of sample ions (sample ion packets) from ion trap 200 to the mass analyzer, because the sample ions can be focused more accurately into the mass analyzer. Therefore, in step 104 of method 100, cooled ions can be ejected from ion traps 80 and 200.

[0114] like Figure 2 As shown in the mass spectrometer 10, ions ejected from the ion trap 80 are ejected through a relatively narrow series of focusing lenses 95 before entering the mass analyzer 90. Those skilled in the art will understand that the focusing lenses 95 have relatively narrow apertures, which define a relatively narrow ion path to the mass analyzer 90. Typically, the width of the narrow ion path is approximately several hundred μm. Therefore, by reducing the spatial distribution of ions within the ion trap 80, the proportion of ions that can be successfully focused along the relatively narrow ion path and enter the mass analyzer 90 increases. Thus, the use of the ion trap 80 according to embodiments of the present disclosure results in increased transport efficiency from the ion trap 80 to the mass analyzer 90.

[0115] Comparative examples of the effects of ion traps according to embodiments of the present disclosure are presented in Figure 7a and 7b As shown in the image. Figure 7a Mass spectra obtained using a mass spectrometer are shown, wherein ions are injected from an ion trap into the mass spectrometer, as described in GB-A-2570435. Figure 7a In a comparative example, a DC potential of -10V was applied to a needle electrode located in an ion-confined region. Figure 7b It shows that in relation to Figure 7a Using the same experimental conditions, the present disclosure Figure 3 The mass spectra obtained using the ion trap described in [the text]. Figure 7bIn this example, a second DC potential of 2V was applied during ion implantation (the first time period), followed by a third DC potential of +10V (the second time period). It should be understood that... Figure 7b The mass spectrometry revealed a greater abundance of ionic substances, especially those with high m / z values. This is due to the improved ion confinement of the ion trap disclosed herein, which in turn improves the efficiency of the ion implantation mass analyzer.

[0116] Although the ion trap 200 of this disclosure includes a first end electrode 210 and a second end electrode 212, it should be understood that in other embodiments, the ion trap 200, 80 may be provided without the external end electrodes 210, 212. In some embodiments, ion implantation into the ion trap can be controlled by other ion transport components of the mass spectrometer. For example, in Figure 2 In one embodiment, ion implantation can be controlled by the transport multipole 70.

[0117] It should be understood that once the ion trap is implanted, the ions can be controlled by the potential trap provided by the first and second confinement electrodes (see, for example...). Figure 5b By providing a wedge-shaped profile for the first limiting electrode 214 and the second limiting electrode 216 (e.g., as shown in the image). Figure 6 The confinement potential of the first and second confinement electrodes can be further increased by providing a wedge-shaped electrode (i.e., in which the distance between the first confinement electrode 214 and / or the second electrode 216 and the central axis of the ion channel increases from the end of the multi-electrode assembly toward the ion confinement region of the ion channel).

[0118] In some embodiments, the first limiting electrode 214 and the second limiting electrode 216 can provide an ion trap 80 and an adjacent ion transport device (e.g., Figure 2 The bridging function between the transport multipole 70 in the mass spectrometer. Therefore, the first and / or second confinement electrodes can extend beyond the end of the multipole electrode assembly 220 toward the adjacent ion transport device to bridge the gap between the ion trap 80 and the transport multipole. This bridging of the ion trap allows ion implantation into the ion trap 80 to be controlled by the first confinement electrode 214 and / or the second confinement electrode 216.

[0119] Therefore, the ion trap and the method of implanting ions into the ion trap according to this disclosure provide improved ion cooling and ion confinement. Specifically, the ion trap 200 is well-suited for effectively confining ions, particularly high mass-to-charge ratio ions, for implantation into other mass spectrometry devices, such as mass analyzers.

[0120] It should be understood that this disclosure is not limited to the above embodiments, and modifications and variations to the above embodiments will be readily apparent to those skilled in the art. The features of the above embodiments can be combined with features of other embodiments in any suitable combination, as will be apparent to those skilled in the art. Therefore, the specific combinations of features described in the above embodiments should not be construed as limiting.

Claims

1. An ion trap for cooling ions of a first polarity for mass spectrometry analysis, the ion trap comprising: A multipolar electrode assembly including a traction electrode and a push electrode, the traction electrode having a through-hole therethrough, the push electrode being spaced apart from the traction electrode, and the multipolar electrode assembly being configured to confine ions of a first polarity in an ion channel extending along the axial direction of the multipolar electrode assembly, the ion channel being disposed between the push electrode and the traction electrode; A first limiting electrode is disposed adjacent to the multi-electrode assembly and extends in the axial direction of the multi-electrode assembly; A second limiting electrode is disposed adjacent to the multi-pole electrode assembly and extends in the axial direction of the multi-pole electrode assembly aligned with the first limiting electrode. The first and second confinement electrodes are spaced apart in the axial direction, and the space between the first and second confinement electrodes defines an ion confinement region of the ion channel. The first and second confinement electrodes are configured to receive a DC potential of the first polarity to further confine ions within the ion confinement region of the ion channel, and The aperture of the traction electrode is aligned with the ion confinement region such that when a driving DC potential is applied to the driving electrode and a traction DC potential is applied to the traction electrode, the ions are ejected from the ion trap.

2. The ion trap according to claim 1, wherein... The ion trap is configured to cool analyte ions within the ion confinement region and then eject the cooled analyte ions into a mass spectrometer for mass analysis.

3. The ion trap according to claim 1, wherein, The first limiting electrode and the second limiting electrode are electrically connected together.

4. The ion trap according to claim 1, wherein, The first limiting electrode and / or the second limiting electrode extend at least 2 mm in the axial direction.

5. The ion trap according to claim 4, wherein the first confinement electrode and / or the second confinement electrode are spaced a variable distance from the central axis of the ion channel along the ion channel.

6. The ion trap of claim 5, wherein the distance between the first confinement electrode and / or the second confinement electrode and the central axis of the ion channel increases from the end of the multipolar electrode assembly toward the ion confinement region of the ion channel.

7. The ion trap according to claim 1, wherein, The first and second limiting electrodes are provided by a slotted electrode arranged in the axial direction, the slotted electrode including a first limiting electrode region and a second limiting electrode region separated by a groove formed in the slotted electrode, the groove being aligned with the ion limiting region of the ion channel.

8. The ion trap according to claim 7, wherein the slotted electrode is a plate electrode.

9. The ion trap according to any one of claims 1 to 6, wherein a plurality of first confinement electrodes are provided, the plurality of first confinement electrodes being uniformly distributed around the central axis of the multi-electrode assembly; and A plurality of second limiting electrodes are provided, the plurality of second limiting electrodes being uniformly distributed around the central axis of the multi-electrode assembly.

10. The ion trap according to any one of claims 7 to 8, wherein a plurality of slotted electrodes are provided, the plurality of slotted electrodes being uniformly distributed around the central axis of the multi-electrode assembly.

11. The ion trap according to claim 1, further comprising: The first and second end electrodes are arranged at opposite ends of the multi-electrode assembly.

12. The ion trap of claim 11, further comprising a controller configured to: An RF potential is applied to the multipolar electrode assembly to confine ions within the ion channels; A first DC potential is applied to the first and second terminal electrodes; and A second DC potential is applied to the first and second limiting electrodes.

13. The ion trap according to claim 12, wherein The first DC potential is greater than the second DC potential.

14. The ion trap according to claim 12 or claim 13, wherein the controller is configured to: During a first time period when ions enter the ion trap, a second DC potential is applied to the first and second confinement electrodes; and During a second time period after the ions have entered the trap, a third DC potential is applied to the first and second confinement electrodes, wherein the third DC potential is greater than the second DC potential.

15. The ion trap according to claim 1, wherein the multi-electrode assembly is a quadrupole electrode assembly, a hexadecimal electrode assembly, or an octodecimal electrode assembly.

16. A mass spectrometer, comprising: Ion trap according to any one of claims 1 to 15; as well as A mass analyzer configured to receive ions ejected from the ion trap through a hole in the traction electrode.

17. A method for implanting ions into an ion trap, the method comprising: Ions of a first polarity are injected into the multipolar electrode assembly of the ion trap, wherein the multipolar electrode assembly includes a traction electrode and a push electrode, the traction electrode having a through-hole therethrough, the push electrode being spaced apart from the traction electrode, and the ions being confined in an ion channel extending along the axial direction of the multipolar electrode assembly, the ion channel being disposed between the push electrode and the traction electrode. The ion trap further includes: A first limiting electrode is disposed adjacent to the multi-electrode assembly and extends in the axial direction of the multi-electrode assembly; A second limiting electrode is disposed adjacent to the multi-pole electrode assembly and extends in the axial direction of the multi-pole electrode assembly aligned with the first limiting electrode. The first and second confinement electrodes are spaced apart in the axial direction, and the space between the first and second confinement electrodes defines an ion confinement region of the ion channel. The ions are further confined within the ion channel in the ion confinement region by applying a DC potential of the first polarity to the first and second confinement electrodes. The orifice of the traction electrode is aligned with the ion confinement region such that when a driving DC potential is applied to the driving electrode and a traction DC potential is applied to the traction electrode, the ions are ejected from the ion trap.

18. The method of claim 17, wherein The ion trap is confined within the ion channel of the multipolar electrode assembly by first and second end electrodes arranged at opposite ends of the multipolar electrode assembly.

19. The method of claim 18, wherein An RF potential is applied to the multipolar electrode assembly to confine ions within the ion channel; A first DC potential is applied to the first and second terminal electrodes to confine the ions within the ion channel; and A second DC potential is applied to the first and second limiting electrodes.

20. The method of claim 19, wherein During the first time period when ions enter the ion trap, a second DC potential is applied to the first and second confinement electrodes; and During a second time period after the ions have entered the trap, a third DC potential is applied to the first and second limiting electrodes, wherein the third DC potential is greater than the second DC potential.

21. The ion trap of claim 1, further comprising a controller, wherein... The controller is configured to apply voltage to the first and second end electrodes, causing ions to be ejected in the axial direction of the ion trap.

22. An ion trap for cooling ions of a first polarity for mass spectrometry analysis, the ion trap comprising: A multipolar electrode assembly configured to confine ions of the first polarity within an ion channel extending in the axial direction of the multipolar electrode assembly; A first limiting electrode is disposed adjacent to the multi-electrode assembly and extends in the axial direction of the multi-electrode assembly; A second limiting electrode is disposed adjacent to the multi-pole electrode assembly and extends in the axial direction of the multi-pole electrode assembly aligned with the first limiting electrode. The first and second confinement electrodes are spaced apart in the axial direction, and the space between the first and second confinement electrodes defines an ion confinement region of the ion channel. The first and second confinement electrodes are configured to receive a DC potential of the first polarity to further confine ions within the ion confinement region of the ion channel, and The first and second limiting electrodes are provided by a slotted electrode arranged in the axial direction, the slotted electrode including a first limiting electrode region and a second limiting electrode region separated by slots formed in the slotted electrode, the slots being aligned with the ion limiting region of the ion channel.

23. The ion trap according to claim 22, wherein the slotted electrode is a plate electrode.

24. The ion trap according to claim 22, wherein The ion trap is configured to cool analyte ions within the ion confinement region and then eject the cooled analyte ions into a mass spectrometer for mass analysis.

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