Ion guide

Abstract

Ions are directed along the ion channel. A plurality of electrodes are arranged on a surface of the ion guide and apply a time-varying potential to repel the ions from the surface. The counter electrode arrangement includes a main counter electrode portion and has an opening extending along the counter electrode arrangement. The counter electrode arrangement applies a direct current (DC) counter potential to force the ions toward the surface. The time-varying potential and the DC counter potential together constrain the ions in the ion guide. The counter electrode arrangement applies a stronger DC counter electromotive force in a region adjacent to the main counter electrode portion than in a region adjacent to the opening, thereby confining the ions in an ion channel corresponding to the opening.

Description

Technical Field

[0001] The present disclosure relates to an ion guide. Background Art

[0002] Ion guides are used in various mass spectrometry systems. Ion guides are used to manipulate and control the movement of ions. For example, ion guides are often used to direct ions from an ion source to an analyzer.

[0003] Certain types of ion guides, such as traveling wave ion guides, use controlled electric fields to separate ions based on their mobility in a gas. This can provide additional separation and / or characterization of ions before they reach a mass analyzer.

[0004] In an ion mobility separator that utilizes drift separation, an electric field forces ions along a gas-filled ion path. This acceleration is resisted by collisions with a buffer gas, and ions of different mobilities reach different equilibrium velocities and separate, arriving at the end of the path at different times. The resolution of this separation process increases with the square root of the ion guide length, meaning that high-resolution separators typically require very long paths. In commercial instruments, linear drift tubes are typically limited to around 1m, and achieving longer separations typically requires folding the complex path into a small 2D plane or 3D volume.

[0005] A prominent example of a folded path ion mobility separator is a SLIM (lossless ion manipulation structure) ion guide, of the type described in US8835839B1, US9812311B2 and US11209393B2. These ion guides use a sandwich printed circuit board (PCB) structure with printed arrays of radio frequency (RF) and direct current (DC) electrodes to form a serpentine channel with a path of about 10 μm that can be mounted on a relatively small surface (e.g., on about 1 μm). 2 region). Traveling waves (US6894286B2, US6794641B2) are often used to propel ions, since maintaining a DC gradient over about 10 m increases the terminal potential to be very high. As described in US20190103261A1, beam switching can be implemented to allow a switchable path that can, for example, bypass a long mobility separator, which may be advantageous when the device is integrated into a mass spectrometer. This technology is increasingly being adopted due to the high resolution and simplicity of the mechanics and electronics.

[0006] A competing ion guide technology stems from the adaptation of stacked ring ion guides whereby a series of apertures form the ion path (S. Guan and AG Marshall, "Stacked Ring Electrostatic Ion Guides", Journal of the American Society for Mass Spectrometry, Vol. 7 (1996), pp. 101-106). US8552366B2 describes a long spiral tube formed from many separate electrode plates. The mechanical complexity of having many open-aperture electrodes results in tighter restrictions than PCB printing. Single closed loops such as those described in US9552969B2 have been manufactured, but single loops have a major disadvantage in that ions with very different mobilities will overlap each other, creating uncertainty in the number of overlaps the ions will experience before being extracted into the detector. This complicates the analysis.

[0007] In US 1 1 373 850 B2 the mechanical complexity problem in constructing a spiral or spiral ion guide is solved by combining a series of holes into a single plate, reducing the number of parts of a multi-turn spiral to that of a single circulating channel.

[0008] Another lesser known ion guide technology is the RF blanket (G. Bollen, International Journal of Mass Spectrometry, 2011, Vol. 299, pp. 131-138), whereby a stacked ring ion guide is essentially spread out over a wide surface and forms a plane that repels the RF pseudopotential. A counter electrode can be used to pin ions down onto the pseudopotential surface. UK patent application number GB2209555.8 describes the use of an RF blanket with an additional orthogonal DC or travelling wave for switching the ion beam between two paths.

[0009] In addition to drift separation, there are other methods for directing and separating ions. Trapped ion mobility spectrometry, included in the Bruker TIMS-ToF (trapped ion mobility spectrometry time of flight) series of instruments, has been widely adopted (Meier, F., Brunner, A.D., Koch, S., Koch, H., Lubeck, M., Krause, M., ... Mann, M. (2018); Online parallel accumulation-serial fragmentation (PASEF) with a novel trapped ion mobility mass spectrometer; Journal of Molecular and Cellular Proteomics, Vol. 17 (Issue 12), pp. 2534-2545). The application of this device is to act as an ion accumulator, releasing ion packets with concentrated mobility (and m / z) to the downstream quadrupole for fine selection and release to the ToF analyzer for MS / MS analysis, thereby reducing ion losses on the quadruplet by an order of magnitude. Very long drift tubes can also play this role.

[0010] While the above described system performs well in many respects, there remains a need for improvements in the manner in which ion guides are formed, particularly ion guides having elongated ion paths. Accordingly, the present disclosure addresses problems associated with constructing ion guides, such as ion guides having elongated ion paths. Summary of the invention

[0011] In this context, the present disclosure provides an ion guide according to claim 1 .

[0012] The ion guide is adapted to guide ions along an ion channel and comprises: a plurality of electrodes arranged on a surface of the ion guide and configured to apply a time-varying potential to repel the ions from the surface; and a counter electrode arrangement comprising a main counter electrode portion and having an opening extending along the counter electrode arrangement, the counter electrode arrangement being configured to apply a direct current (DC) counter potential to force the ions towards the surface, the time-varying potential and the DC counter potential together confining the ions in the ion guide; and

[0013] Wherein the counter electrode arrangement is configured to apply a stronger DC counter potential in a region adjacent to the main counter electrode portion than in a region adjacent to the opening, thereby confining the ions in the ion channel corresponding to the opening.

[0014] The opening that is arranged in this counter electrode arrangement can provide weaker counter potential in this region adjacent to this opening.The electric potential of this form limits ions that can be constrained in ion channel therein.This can be used to provide long path length.Opening can only partially extend in the main electrode part (that is, grooves can be present in a single electrode), or opening can extend through the main electrode part always, that is, opening can be the hole in the counter electrode arrangement (and auxiliary electrode part or back plate can be optionally set behind the opening).

[0015] Ion channels can generally correspond to openings because the form of the openings determines the form of the potential in the ion guide. An ion channel can be an area of ​​an ion guide defined by a potential well, such as an area where the potential is less than a certain percentage of the height of the potential well. The channel potential can be about 50 mV deep to constrain thermalized ions. In some embodiments, the depth of the potential well can be set to a higher voltage (such as up to 0.1 V or up to 0.5 V) to account for space charge effects. The ion channel well depth can be within a wide voltage range. For example, the ion channel well depth can be 1% to 90% of the counter electrode (also referred to as a deflector) potential and still effectively guide ions.

[0016] Some embodiments of the present disclosure provide RF blankets (that is, RF pseudopotential surfaces and opposing counter electrode arrangements) having circuitous or meandering ion paths that are created at least in part by modifying the counter electrode to include an opening (e.g., by cutting a focal line into the counter electrode arrangement). In some embodiments, angling the counter electrode arrangement relative to the RF surface can provide a DC gradient. In some embodiments, a traveling wave electrode is superimposed on the counter electrode arrangement, which can be used to improve the guidance of ions along the ion channel.

[0017] In some embodiments, the ion guide described herein may include a counter electrode arrangement having a first surface at a first distance (in a direction normal to the surface) from the plurality of electrodes and a second surface at a second greater distance (in a direction normal to the surface) from the plurality of electrodes, wherein the second of the surfaces corresponds to the ion channel. The second surface may be a back plate or may be a surface of a groove in the first surface of the counter electrode arrangement.

[0018] Embodiments of the present disclosure may provide 2D or 3D ion guides that can move ions from one surface to another surface mounted orthogonally ( Fig.10 ), or move to another surface mounted on the opposite side ( Fig.11 ), or moved to another surface mounted at a different level ( Fig. 9 (a)). This can provide complex 3D ion pathways in a very small space.

[0019] Fig.12 , Fig.13 , Fig.14 and Fig.15 Circulation models are shown in . These circulation models can be constructed as components of essentially planar surfaces or as curved RF blankets. Such arrangements can provide advantages such as long ion path lengths, especially if the shape of the counter electrode induces a 3D spiral motion.

[0020] Embodiments of the present disclosure seek to provide an ion guide having a simple mechanical structure, a long path length, a high mobility resolution and / or a high ion capacity. In some cases, the ion guide may include only one surface of the trapping RF electrode so that only one surface of the ion guide may be contaminated by ion deposition. Additional advantages arise from the ability to generate a DC gradient by angling the counter electrode.

[0021] These and other advantages will become apparent from the following disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present disclosure will now be described by way of example with reference to the accompanying drawings, in which:

[0023] Figure 1 (a) and Figure 1 (b) shows an ion guide in an embodiment of the present disclosure;

[0024] Figure 2 An ion guide in an embodiment of the present disclosure is shown;

[0025] Figure 3 (a) and Figure 3 (b) shows an embodiment of an opening in the counter electrode arrangement;

[0026] Figure 4 A mass spectrometry system incorporating an embodiment of the present disclosure is shown;

[0027] Figure 5 An ion guide in an embodiment of the present disclosure is shown;

[0028] Figure 6 An ion guide in an embodiment of the present disclosure is shown;

[0029] Figure 7 An ion guide in an embodiment of the present disclosure is shown;

[0030] Figure 8 An ion guide in an embodiment of the present disclosure is shown;

[0031] Fig. 9 (a) and Fig. 9 (b) shows an ion guide in an embodiment of the present disclosure;

[0032] Fig.10 An ion guide in an embodiment of the present disclosure is shown;

[0033] Fig.11 An ion guide in an embodiment of the present disclosure is shown;

[0034] Fig.12 shows the simulated behavior of an ion guide in an embodiment of the present disclosure;

[0035] Fig.13 shows the simulated behavior of an ion guide in an embodiment of the present disclosure;

[0036] Fig.14 (a) Fig.14 (b) and Fig.14 (c) shows an ion guide in an embodiment of the present disclosure;

[0037] Fig.15 An ion guide in an embodiment of the present disclosure is shown; and

[0038] Fig.16 (a) and Fig.16 (b) shows an ion guide in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0039] The present disclosure provides an improved ion guide and solves problems associated with constructing an ion guide. An elongated ion path can be used for ion mobility separation, but can also be used in many other situations. In some cases, it may be desirable to construct an ion channel that provides a long ion path in a relatively small area. For example, some embodiments provide an ion channel that folds a few meters of path into a small area (e.g., about 0.5×0.5 m), has low ion loss, has a high space charge capacity (internal volume), and / or can resist the negative effects caused by charging and contamination.

[0040] The present disclosure provides a device that combines a time-varying oscillating potential and an opposite counter potential. For example, an RF blanket can be provided by a pseudopotential surface formed by an array of electrodes arranged on the surface, wherein ions are pinned to the RF blanket by an opposing DC counter electrode (also described herein as a deflector). In some embodiments, a traveling wave (also described herein as a T wave) is used to guide ions along an ion channel, either superimposed on some or all of the RF electrodes, or applied to a separate electrode array mounted on a deflector to propel ions along the ion channel.

[0041] Such an arrangement is shown in Figure 1 (a) In. Figure 1 (a) depicts an ion guide having a plurality of electrodes 101, which essentially provide an RF surface, arranged on a surface of the ion guide (which surface is shown as being flat, but is not necessarily flat), the plurality of electrodes being configured to apply a time-varying potential to repel ions 150 from the surface. The time-varying potential may provide a pseudopotential barrier. The pseudopotential barrier will have a form corresponding to the plurality of electrodes 101, and may therefore be substantially planar. A counter electrode arrangement 102 (which in this embodiment is shown as a single counter electrode) is configured to apply a direct current (DC) counter potential to force ions 150 toward the surface; this DC counter potential effectively repels ions from the counter electrode arrangement and pins the ions against the time-varying potential, such that the time-varying potential and the DC counter potential together confine the ions 150 in the ion guide.

[0042] Figure 1 (b) shows how ion channels can be achieved by providing an RF blanket 101 and guides or openings 103 in the deflector 102 which help to confine the ions in the ion channel.

[0043] The counter electrode arrangement 102 is configured to apply a stronger DC counter potential in a region of the ion guide adjacent to a main portion of the counter electrode than in a region of the ion guide adjacent to an opening extending along the counter electrode arrangement 102. Figure 1 (b) is shown by the circuitous trace 103 which provides a region of weakened DC potential of the counter electrode arrangement 102. This confines the ions 150 in an ion channel corresponding to the opening in the counter electrode arrangement. The ion channel is elongated (i.e., its length (in the direction of ion travel) is much longer than its width (in a direction orthogonal to the direction of ion travel), at least an order of magnitude longer or 10 times higher). Figure 1 In (b), the opening in the counter electrode arrangement 102 defines an ion channel that folds back on itself four times, but different numbers of folds (e.g., 1, 2, 3, 4, 5, 6, 7) may also be provided. The ion channel and opening need not necessarily fold back completely on themselves; they may follow a generally circuitous or tortuous path that does not fold back completely. In general, the ion channel and opening may take any suitable form, such as linear and / or curved, etc.

[0044] Figure 1 (a) and Figure 1 The ion guide shown in (b) includes a plurality of electrodes 101 that span the xz plane but are relatively thin (e.g., substantially planar) in the y direction. Similarly, the counter electrode arrangement 102 extends in the x direction and the z direction, but is relatively thin in the y direction. The ion channel is defined by an opening in the counter electrode arrangement 102, and ions 150 moving along the ion channel are substantially constrained in the y direction, while the channel extends in the z direction and / or the x direction and causes the ions to move in the z direction and / or the x direction as they move along the ion channel. The directions x, y, and z are mutually orthogonal directions.

[0045] In order to achieve long path lengths in an ion guide, a large RF surface area can be divided into winding channels, and ions are entrained within the ion channels and prevented from taking a direct route through the ion guide. In a SLIM device, a printed DC electrode array is used to prevent ions from escaping a defined path. The embodiments of the present disclosure alternatively use a counter electrode arrangement to assist in ion confinement. The counter electrode arrangement may include a flat metal plate that can be altered so that a weakened DC potential region defining an ion channel can be tracked into the plate. Since the counter electrode repels ions, the weakened region acts as a relatively attractive track, thereby locking the ions into the weakened region. The weakened region can be formed, for example, by etching a relatively deep groove in a relatively thick deflector, or providing a hole in a relatively thin deflector and allowing the field from a less repellent backing plate to penetrate.

[0046] Figure 1(b) shows how such an opening (shown as a track) can be combined with the RF surface 101, where superimposed travelling waves travel in alternating directions to produce a complex folded ion path. The curvature of the opening ensures that the opening minimally conflicts with the travelling waves imposed in the ion guide.

[0047] The counter electrode arrangement may be a single unitary electrode having a main portion and an opening therein, or the counter electrode arrangement may comprise a plurality of electrode portions located on either side of an aperture extending all the way through the counter electrode arrangement.

[0048] Figure 1 A number of advantageous features are shown in . In general, it may be advantageous for the openings and ion channels to be circuitous. Figures 5 to 16 Also shown are tortuous ion channels. This ensures that long ion paths are obtained, which may be particularly useful in ion mobility separations. Openings and ion channels can be equivalently described as meandering or tortuous. Openings and ion channels can be in two spatial dimensions (e.g., Figure 1 ) or in three spatial dimensions (as shown in Figures 9 to 16 being discussed) is circuitous.

[0049] The ion guide, the opening and the ion channel may be arranged in a first direction (from Figure 1 (b) extends from the lower left corner to the upper right corner) (e.g., typically extending between the ion inlet and the ion outlet), and the opening and the ion channel may each include one or more portions extending away from the first direction. The ion channel may include multiple regions that deviate from the straight line between the ion inlet and the ion outlet. This can be described as the opening and the ion channel each including one or more first portions extending in the first direction and one or more second portions extending in a second direction different from the first direction. In some embodiments, the opening and the ion channel may also include one or more third portions extending in a third direction different from the first direction and the second direction. When described in such terms, the second direction and the third direction may be opposite directions (e.g., Figure 1 (b), wherein the opening and the ion channel rotate 180 degrees multiple times) and / or the angle between the second direction and the third direction can be greater than 90 degrees or greater than 120 degrees. The first direction can be perpendicular to the second direction and / or the third direction.

[0050] Figure 2An example of how a relatively attractive channel 103 (arranged as an opening in a counter electrode arrangement) can be cut in a deflector electrode 102 is shown, wherein field penetration from a back plate 104 helps provide ion confinement. The deflector 102 and the back plate 104 together define the counter electrode arrangement. The combined effect of the gaps in the deflector 102 and the back plate 104 provides an attractive weakened region that corresponds to the opening in the deflector and thus defines the ion channel. The main electrode portion of the counter electrode arrangement 102 is adjacent to the ion channel, and the back plate 104 is located behind the main electrode portion of the counter electrode arrangement 102.

[0051] For relatively long flight paths the large 1 / 4m 2 A flat, thin (e.g., about 0.5 mm thick) deflector 102 plate may be supported by additional material unless there are many mounting points on the RF electrode surface 101. In some cases, both the deflector 102 and the backing plate 104 may be mounted to a frame that may be common to both components. The frame may also be the backing plate 104 or may form the backing plate. In any case, an attractive region may be formed and thus an ion channel may be defined by the openings in the deflector 102 and the field penetration from the backing plate 104.

[0052] Figure 3 A field simulation illustrating the attractive potential well provided by embodiments of the present disclosure is shown. Figure 3 (a) shows a groove cut in a thick deflector electrode, and Figure 3 (b) shows a hole cut in the deflector with a backplate at a weaker DC potential. Figure 3 The field simulations in were constructed in the MASIM3D program and show the attractive potential wells >0.5 V created by scratching a 5 mm wide hole in a 0.5 mm thin deflector plate or a 2 mm deep, 10 mm wide groove in a thick plate at 10 V. The gaps between the counter electrode arrangement and the RF electrode surface were 4 mm and 3 mm respectively and the measurements were taken at 0.5 mm from the RF surface electrode where the electrons could be located. The action of the deflector was not affected by the provided grooves.

[0053] For ion mobility measurements, higher pressures improve resolution up to the limit of the RF trapping capability (approximately 0.1-10 mbar, or preferably 1 mbar). For simplicity, the RF surface can be a printed PCB, although the RF blanket can be constructed with very complex long board assemblies, or small electrodes mounted to a substrate. An RF electrode array can be used as a high-tolerance ion trapping mechanism. Alternating RF phases can be applied to each electrode in an electrode array on the surface (e.g., substrate) of the RF blanket. Typical electrode thicknesses and spacings for such devices are 0.5mm to 1.5mm, with 20V to 2000V RF applied at 1MHz to 3MHz frequencies. A traveling wave (T wave) can be superimposed on the RF electrode, or on another electrode array as desired. This can be implemented as 4+ phase additive RF, with each phase 90 degrees outward and typically running at a lower voltage and frequency than the trapping waveform. For example, a 5V to 50V traveling wave with a frequency of 50KHz to 250KHz can be provided. The traveling wave can also be implemented as a series of transient DC pulses, giving the impression of a DC pulse moving down the series of electrodes, typically 1 or 2 electrodes up and 3-6 electrodes down at a time.

[0054] Figure 3 The simulation in shows the effect of an opening in a counter electrode arrangement. The electric potential varies in the x-direction, with a potential well (and therefore an ion channel) being formed adjacent to the opening in the counter electrode arrangement. The region of the ion guide adjacent to the main counter electrode portion may be defined as a region that is closer to the main counter electrode portion than to the opening in the counter electrode arrangement. Similarly, the region of the ion guide adjacent to the opening may be defined as a region that is closer to the opening than to the main counter electrode portion. Thus, these regions may be distinguished by a surface extending from the edge of the opening in the counter electrode arrangement in a direction orthogonal to the surface of the counter electrode arrangement; all points on one side of this surface will be closer to the opening than to the main counter electrode portion, and this set of points may be referred to as the region of the ion guide adjacent to the opening. As Figure 3 As shown, since the formed potential is not a perfect square well and has a curved shape, the ion channel formed by the electrode arrangement in the present disclosure does not completely correspond to the shape of the opening, but generally corresponds to the shape of the opening in the counter electrode arrangement.

[0055] In general, the counter electrode arrangement described herein may be a deflector electrode. The openings in the counter electrode arrangement may be elongated openings in the counter electrode arrangement. For example, the lengths of the openings described herein (in the direction of ion travel) may be one order of magnitude longer than their widths (i.e., the lengths of the openings are at least 10 times their widths), or two orders of magnitude longer than their widths (i.e., the lengths of the openings are at least 100 times their widths).

[0056] In some embodiments, the counter electrode arrangement described herein may include a counter electrode, and the opening may include a recess in the counter electrode (e.g., a small space formed by providing a surface that is further back than the rest of the counter electrode in a direction orthogonal to the surface on which the plurality of electrodes are arranged). For example, the counter electrode arrangement may be a unitary (one piece of metal) counter electrode having a groove or recess serving as the opening. In such cases, the surface of the main counter electrode portion (i.e., the portion of the counter electrode arrangement closest to the plurality of electrodes arranged on the surface) may be at a first distance from the plurality of electrodes (e.g., in a direction orthogonal to the surface on which the plurality of electrodes are arranged), and the surface of the opening (e.g., the surface inside the recess, groove, or recess) may be at a second distance from the plurality of electrodes, the second distance being greater than the first distance. Thus, the opening may extend at least partially through the counter electrode arrangement. The counter electrode arrangement may be generally arranged on the surface, wherein the counter electrode arrangement surface is substantially parallel to the surface on which the plurality of electrodes are arranged. When the counter electrode is flat (ie, when the counter electrode arrangement surface is substantially planar), this may provide a blanket-like structure; however, in some embodiments, the counter electrode arrangement surface and the surface on which the plurality of electrodes are arranged may be curved and parallel to each other.

[0057] In some embodiments, the opening may extend completely through the counter electrode arrangement. That is, the opening may be a hole in the counter electrode arrangement. In such cases, the counter electrode arrangement may include a back plate (a second surface of the counter electrode arrangement) located behind the opening (i.e., the main counter electrode portion is located between the back plate and the ion channel (and between the back plate and the opposing plurality of electrodes), wherein the back plate is configured to apply a weaker DC counter potential (or even a small attractive potential) than the main counter electrode portion. Thus, a back plate may be provided. Figure 3 That is, in the ion guides described herein, the counter electrode arrangement may be configured to apply a DC potential having a potential minimum corresponding to the opening and the ion channel; the form of the ion channel may be defined by the shape of the opening.

[0058] The counter electrode arrangement described herein may include one or more main counter electrode portions adjacent to the opening and / or located on each side of the opening. For example, the counter electrode arrangement may include two main counter electrode portions, wherein the opening separates the counter electrode arrangement. The main counter electrode portions may be planar surfaces.

[0059] In some embodiments, an ion mobility separator using an ion guide as described herein can be coupled to a mass spectrometer, such as a tandem mass spectrometer. Thus, the present disclosure provides a mass spectrometry system comprising a mass analyzer and any one (or more) of the ion guides described herein. The ion guide can be configured to provide ions to the mass analyzer (directly or indirectly via an intermediate component).

[0060] An ion mobility spectrometer may also be provided. An ion mobility spectrometer may include any of the ion guides described herein which may provide a long ion path over which ions may be separated according to their mobility (thus providing high resolution ion mobility data).

[0061] In some embodiments, ion guides may be used to add one or both of ion mobility information to the mass analysis and / or operate in conjunction with a quadrupole (or other mass filter) to limit the fraction of ions that deposit on the quadrupole. Figure 4 A hybrid Orbitrap as described in US 10699888 B2 is shown. TM / Example of a multi-reflection time-of-flight mass spectrometer modified to incorporate an ion mobility separator according to embodiments of the present disclosure.

[0062] Similar to that described in US10699888B2 and therein Figure 1 To configure the system shown in the example Figure 4 The number of elements. Therefore, US10699888B2 is incorporated herein by reference, and the same figure numbers are used for elements common to US10699888B2 and the present disclosure. Specifically, the function of each of the following elements is more fully described in US10699888B2: electrospray ionization source 20; capillary 25; quadrupole mass filter 70; C-trap 100; orbital trap mass analyzer 110; fragmentation chamber 120; multipole ion guide 130; extraction trap 140; relatively tilted ion mirror 160; deflectors 170, 172; detector 180; and correction strip electrode 190. Figure 4 Additionally included is an ion funnel 30 that receives ions from the capillary 25 and an optional calibrant source 35 that provides a calibrant. The ions enter an ion mobility separator 40 that incorporates an ion guide according to the present disclosure. An optional charge detector 75 is provided to detect charged particles.

[0063] In use, ions are generated from the sample by the electrospray ionization source 20 and enter the vacuum system through the capillary 25 so as to be trapped in the ion funnel 30. In this case, the funnel 30 can act as an accumulating device for pulse introduction to the separator 40, but this function can also be combined into the separator 40 itself through the gate electrode. Then, the ions are introduced into the separator 40 and pass through the winding path, thereby being separated by mobility (and basically by m / z and charge state). When ions of different mobilities appear to the quadrupole 70, based on the understanding of the relationship between the analyte type and the mobility and m / z, the quadrupole 70 is set to transmit ions only with the target ion m / z within the mobility window. Then, the selected ions are optionally fragmented and sent to the orbital capture analyzer 110 or the multi-reflection flight time analyzer for mass analysis.

[0064] Figure 4 A bypass to the separator 40 is not shown, but such a bypass may be provided so that a mass spectrum over a wide m / z range may be recorded without the time and ion losses that occur to the separator device 40. This may be provided as a second path built into the RF blanket PCB, or by an additional ion guide with access controlled by beam switching techniques, such as described in US20190103261A1, which is incorporated herein by reference. Alternatively, in some embodiments, the orthogonal directional forces (i.e., Figure 1 The alternate T waves in the ion beam are shown in Figure 1 and can push ions directly to the ion exit in a more direct path (rather than the circuitous path shown). However, this method cannot be performed in parallel with accumulation and separation, which can be performed with a parallel shorter path. For this reason, beam switching and parallel paths can also be started before the accumulation region, and then the full MS spectrum can be repeatedly acquired during a single separation cycle.

[0065] Figure 5 An embodiment is shown in which the deflectors 102 (counter electrode arrangement) are tilted relative to the surface of the RF electrodes 101 to provide DC gradients in the Z and X directions, while a traveling wave superimposed on alternating sets of RF electrodes 101 pushes the ions 150 in the X direction opposite to the DC gradient. In this way, the T wave serves to raise the potential of the ions 150, resetting them so that they can drift back when they enter the DC-only region of the ion guide. Optionally, the segments of the RF electrodes 101 may be separated by DC guard electrodes that may extend upward from the RF surface 101, descend from the deflector electrodes 102, or connect both and provide mechanical support. While Figure 5 Not shown, but optional openings (eg, grooves or holes as previously described) may be provided in the counter electrode arrangement 102 to help confine the ions 150.

[0066] Returning to the general terminology used previously, in some embodiments, the time-varying potential applied by the plurality of electrodes is a radio frequency RF oscillating potential. This can provide an RF blanket type structure. Thus, each electrode in the plurality of electrodes can be configured to apply a potential having a different phase (e.g., opposite phase) to each adjacent electrode in the plurality of electrodes.

[0067] The plurality of electrodes may include an electrode set configured to apply a traveling wave potential along one or more portions of the ion channel to guide ions along the ion channel. These portions may extend in any spatial direction. The plurality of electrodes may additionally or alternatively include an electrode set configured to apply a DC potential gradient along one or more portions of the ion channel to guide ions along the ion channel. In some cases, the DC potential gradient may be superimposed on the RF electrode. In some embodiments, a plurality of different electrode sets may be configured to apply alternating traveling wave potentials and DC potential gradients along corresponding portions of the ion channel to guide ions along the ion channel. This arrangement may be as shown in FIG. Figure 5 As shown, it can optionally be combined with an opening in the counter-electrode arrangement (deflector).

[0068] Multiple electrodes may be disposed along the length of the ion channel; that is, a majority of the channel (e.g., at least 90% of its length) may be in close proximity to the electrodes that apply the time-varying potential. Figure 7 and Figure 8 As shown, the electrodes may follow the tortuous path of the channel. For at least a portion of the length of the ion channel, the electrodes in the plurality of electrodes may be substantially perpendicular to the ion channel. For example, for most of the length of the ion channel, Figure 5 The channels in the array are substantially perpendicular to the electrodes, with only small gaps (in the z-direction) between the parallel rows of electrodes.

[0069] The counter electrode arrangement may be tilted relative to the surface on which the plurality of electrodes are arranged (i.e., at a non-zero angle). For example, by varying the distance between the counter electrode arrangement and the plurality of electrodes, a DC gradient may be provided to direct ions along at least a portion of the ion channel. The tilt may be opposite to the direction in which the plurality of electrodes drive the ions. For example, Figure 5 As shown, the traveling wave can drive the ions in the positive X direction, while the overall tilt of the counter electrode arrangement can drive the ions in the negative X direction. This pattern alternates as the ions move along the ion channel. The counter electrode arrangement is configured to apply a traveling wave potential along one or more portions of the ion channel to guide the ions along the ion channel.

[0070] Figure 6Another embodiment of an ion guide is shown. In this embodiment, an attractive trace 103 (e.g., a groove or hole) in a deflector electrode 102 (which may alternatively be located on a PCB) provides a meandering or circuitous route, and a unidirectional T wave and / or DC gradient superimposed on an RF surface electrode 101 (which may be located on a PCB substrate) drives ions from the ion inlet to the ion outlet. In this embodiment, the route of the opening is not completely turned back, i.e., the DC does not travel completely against the traveling wave, which prevents the ions from being completely trapped.

[0071] The travelling waves may be supplied from an array of electrodes printed on the deflector plates 102 themselves or printed on a backplane PCB, with matching grooves or holes cut into the deflector plates 102 .

[0072] Figure 7 An embodiment is shown in which the path of ion travel and the traveling wave is defined by the deflector side, while the RF electrodes are only responsible for generating the RF surface. Figure 7 In the RF blanket, the T-wave electrodes printed on the deflector PCB form an ion path with only RF surface for the RF blanket. The T-wave does not need to be at a 90 degree angle, but can follow a curved path.

[0073] exist Figure 8 In the process, a traveling wave in one direction is generated from these electrodes.

[0074] Figure 8 yes Figure 7 An alternative scheme in which for one dimension of motion the T waves are applied to a deflector electrode arrangement and for the other dimension the T waves are applied to an RF blanket array. Figure 7 and Figure 8 The advantage of is that the RF surface electrodes have limited complexity, which opens the possibility that they can be formed from solid electrodes rather than printed.

[0075] It will be appreciated that various combinations of DC gradients, time-varying potentials, traveling waves, and formed channels may be provided and may be used. Figures 1 to 8 Various combinations of the techniques described in .

[0076] In the above embodiments, ion movement is performed in a single plane. However, the above techniques can be extended to three dimensions. More complex folded paths can be provided so that ions can benefit from three-dimensional movement, which, for PCB-based ion guides, can involve ions being transferred between different surfaces. In some embodiments, a curved PCB (including with printed electrodes) can be provided.

[0077] Fig. 9(a) shows an embodiment in which a traveling wave drives ions 150 away from the end of RF surface 101a before the ions fall onto another RF surface 101b under the influence of the DC field of deflector 102. Fig. 9 As shown in (a), the second RF surface 101b may be spaced apart from and parallel to the first RF surface 101a. Alternatively, the second surface 101b may be positioned back-to-back with the first surface 101a, such as Fig. 9 (b) and the second deflector 102 is mounted underneath, or the back side of the first surface substrate can be used as a deflector for a second RF surface mounted underneath. In the former case, the same deflector potential can be used, although the second surface is further away from its deflector than the first surface (i.e., the deflector can be located at a distance x and a second distance greater than x, as shown in FIG. Fig. 9 (b) may help to generate a net DC offset from the first surface 101a down to the second surface 101b. In the latter case, the traveling wave can continue around the edge of the substrate / PCB so that the RF surface effectively follows a sharp bend.

[0078] The ends of the PCB can be easily metallized, so that a single electrode can be easily formed. Fig. 9 The back-to-back arrangement in (b) may experience undesirable effects due to unterminated RF at the edge of the PCB. Such an abrupt end to the RF blanket may also create an RF barrier that the T waves will preferably be strong enough to overcome. Optionally, only DC may be applied to the ends of the PCB to reduce this fringe field and any resulting RF heating.

[0079] Returning to the general terminology used previously, the ion guides described herein can provide a circuitous ion path in three dimensions. In some embodiments, the counter electrode arrangement can at least partially or completely surround a plurality of electrodes (or a plurality of electrodes if there are multiple sets). For example, the counter electrode arrangement can extend in a first direction, and the ions can run around an RF blanket (or a plurality of RF blankets) extending in the first direction. To help achieve this, an opening in the counter electrode arrangement can extend along one or more (i.e., one or aplurality of) inner surfaces of the counter electrode arrangement. This can define a potential well that follows a circular or spiral path having an axis extending in the first direction.

[0080] The one or more surfaces on which the plurality of electrodes are arranged may be substantially planar. They may be back-to-back planar surfaces, such as Fig. 9 (b), or the planes may be spaced apart, as in Fig. 9(a). Thus, in general, the ion guides described herein may include a second plurality of electrodes (e.g., a second RF blanket) disposed on a second surface of the ion guide, the second plurality of electrodes being configured to apply a second time-varying potential to repel ions from the second surface. The first plurality of electrodes and the second plurality of electrodes may face the same direction, different directions, or opposite directions. For example, the second plurality of electrodes may be disposed on a rear surface of the surface on which the first plurality of electrodes are disposed. That is, Fig. 9 As shown in (b), the first plurality of electrodes and the second plurality of electrodes may be arranged back to back. The first surface and the second surface may be parallel and / or planar.

[0081] In some embodiments, there may be a third plurality of electrodes disposed on a third surface. Fig. 9 The parallel arrangement in can be combined with an orthogonal or angled third surface, such as Fig.10 shown.

[0082] The combination of electrodes and counter electrodes can provide complex three-dimensional pathways.For example, in some embodiments of the present disclosure, the ion channel can be any one or more of: cyclic; helical; and / or circuitous in two or three dimensions.

[0083] Fig.10 Ions 150 are shown being transferred from an ion channel adjacent to the first surface 101a to the second orthogonal surface 101b. Once the ions 150 land on the orthogonal surface 101b, they can be moved in either direction ( Fig.10 Move ions 150 up or down in the flow.

[0084] Thus, in general, in such embodiments, the second surface may be inclined (ie, at a non-zero angle) relative to the first surface or perpendicular to the first surface.By appropriately applying potentials and potential gradients, ions may be transferred from one surface to another.

[0085] The second plurality of electrodes may be configured to apply a traveling wave potential and / or a DC potential gradient potential along one or more parts of the ion channel to guide ions along the ion channel. This may be operated similarly to the previously described embodiments, wherein the alternating parts of the ion channel are defined by different potentials applied to different electrodes or electrode sets. Preferably, the ion channel extends from the first plurality of electrodes to the second plurality of electrodes. That is, ions may travel along the ion channel adjacent to the first surface, and then appropriate potentials may be applied at the region between the first surface and the second surface, so that ions are transferred from pinning to the first surface to pinning to the second surface. By a combination of a time-varying potential applied by the second surface and a DC counter potential applied by any potential of the electrode arranged by the counter electrode, ions may be pinned against the second surface. For example, in some embodiments, the counter electrode arrangement may include a second counter electrode arrangement relative to the second plurality of electrodes. In order to ensure that a continuous ion path is defined, an opening may be arranged along the first counter electrode and extended along the second counter electrode arrangement.

[0086] Fig.11 Shows Fig. 9 The circular ion guide is provided with back-to-back PCB electrodes 101 within a frame defined by a deflector 102 (counter electrode arrangement). The deflector 102 is arranged in a Fig.11 101 , which can help push ions 150 around the sides of RF electrode 101. Of course, deflectors with other cross-sections (e.g., square or rectangular) can also be used, as long as the appropriate potential is applied within the ion guide. In any case, the counter electrode arrangement can at least partially surround or completely surround the first plurality of electrodes and / or the second plurality of electrodes. Thus, a long three-dimensional ion channel can be defined.

[0087] Fig.12 Shows Fig.11 MASIM3D simulation of ion motion in a system of the type shown. Fig.12 In the simulation, the RF electrode was 0.4 mm thick and a 100 V 2 MHz trapping RF was applied. The repeller DC was set to 10 V and the traveling wave was a 4-phase 200 kHz RF with an amplitude of 7.5 V. It can be seen that the ion motion is greatly disturbed by the stripe RF at the 180 degree rotation point, and it is expected that the inverse scheme of rotating only 90 degrees at each angle will be preferred. In any case, this simulation proves that such a mechanism can be used to provide a long ion path.

[0088] An advantage of such an embodiment is that the design can be easily extruded in the Z direction to form a three-dimensional ion channel within the ion guide. Fig.13 shows how a small DC gradient can be superimposed to extend Fig.12A device is provided to drive ions down the length of the system. The ion motion forms a spiral, but is unconstrained in this drift dimension, with trajectories widely spread and overlapping. Thus, a confinement mechanism may be provided; for example, such an embodiment may benefit from having a spiral opening (e.g., a recess or full opening) in the counter electrode arrangement to improve the definition of the ion channel, as previously discussed.

[0089] Fig.14 (a) Fig.14 (b) and Fig.14 (c) shows Figures 11 to 13 The inverse of the structure. Fig.14 (a) shows a circulating ion guide with an assembly of a PCB electrode 101 surrounding a central deflector 102, Fig.14 (b) shows the out-of-plane DC gradient supplied by the wedge-shaped deflector 102, and Fig.14 (c) shows the ion motion in a 3D extruded version of the ion guide, showing the elongated spiral ion path. Here, the PCB printed electrode 101 is mounted on the inside of the outer layer, and the deflector 102 is positioned in the center. This can be provided with an arrangement of a flat PCB to form the RF electrode 101. Fig.14 (b) shows how ions can be induced to spiral up the length of the guide by a wedge or regular tetrahedral pyramid shape in the deflector 102, although the deflector 102 can also be a PCB with printed electrodes that have their own generated T-wave DC gradient, such as Fig.15 As shown (in this case, an opening may or may not be provided in the deflector 102).

[0090] Fig.14 The printed RF electrode 101, not shown, may have gaps to mount a DC guard electrode following a spiral path for drift control and to provide mechanical support for the deflector 102. The deflector 102 may also have a Figure 1 The etched guide paths (i.e. openings in the counter electrode arrangement) are described. The front and back sides of the device are accessible, allowing the injection and extraction guides to be integrated into the PCB. Here, the deflector 102 is conical and incorporates spiral grooves (openings) to limit ion drift.

[0091] Fig.15 A circulating ion guide is shown incorporating a central PCB deflector 102 to provide a guided DC gradient.A plurality of electrodes 101 are provided and arranged at least partially around a counter electrode 102.

[0092] Fig.16 (a) shows the Fig.14 Relatively circular end cross section, Fig.16 (b) shows the Fig.14 Rather circular side cross section. A cylindrical deflector 102 is provided within a plurality of electrodes 101 arranged on a cylindrical surface. A spiral opening 103 in the deflector improves the guidance of the ions in the manner previously described.

[0093] In these embodiments, a complex three-dimensional ion path can be provided. The counter electrode arrangement can be tapered, curved, conical or frustoconical. Additionally or alternatively, a plurality of electrodes can be arranged as cylindrical, conical or frustoconical. These geometries can provide long path lengths. In such cases, the first plurality of electrodes and / or the second plurality of electrodes can at least partially surround or completely surround the counter electrode arrangement.

[0094] It will be appreciated that many variations may be made to the above described systems and methods while retaining the advantages mentioned above. For example, where specific components have been described, alternative components providing the same or similar functionality may be provided.

[0095] The embodiments described herein include various potentials applied by a counter electrode arrangement, as well as potentials applied by multiple electrodes or multiple electrodes on another surface. These various different potentials can be combined (superimposed) to guide ions along the ion channels of the present disclosure.

[0096] The ion guides described herein can be incorporated into various mass spectrometry systems. The ion guides disclosed herein can manipulate and control the movement of ions in a vacuum environment or a pressurized gas (e.g., for an ion mobility spectrometer). The ion guides can provide a convenient device for guiding ions from an ionization source to a mass analyzer, thereby ensuring a long ion path, efficient ion transport, and / or accurate analysis.

[0097] The ion guide of the present disclosure can be operated in a pressure controlled or high vacuum environment to reduce or minimize the possibility of collisions between ions and gas molecules. In such cases, the materials and construction of the ion guide are compatible with vacuum conditions. For example, a gas-tight enclosure can be provided. In some embodiments, gas is introduced to assist in ion transport or cooling, or to control the degree of ion separation in ion mobility experiments. The gas dynamics and pressure within the guide can be carefully controlled to control ion behavior.

[0098] The ion guides of the present disclosure can provide precise control of the electric potential within the device to manipulate the ion trajectory. In many embodiments, an array of RF electrodes arranged on a surface can be used to control the electric field (and pseudopotential) that guides ions along a specific path. The electrodes of the present disclosure can be connected to and / or combined with various voltage sources. For example, each electrode can be connected to one or more power supplies to apply a specific voltage potential, and the voltage applied to one or more electrodes (or each electrode) can be independently controllable. The electrodes of the ion guides described herein can be configured to have RF and / or DC fields applied thereto; the combination of these fields can form a complex potential landscape that provides complex ion motion.

[0099] The ion guide of the present disclosure may provide a complex ion channel extending between an ion inlet port and an ion outlet port.The ion inlet may be connected to an ion source or another upstream ion processing component, and the ion outlet may be connected to a mass analyzer or some other downstream ion processing component.

[0100] A variety of different mass analyzers can be used with the ion guides of the present disclosure. For example, the ion guides described herein can be used in conjunction with any one or more of: a quadrupole analyzer; a time-of-flight analyzer; an ion trap; and / or an orbital trap mass analyzer.

[0101] Methods are also provided. For example, in one aspect, a method of guiding ions along an ion channel of an ion guide is provided, the ion guide comprising a plurality of electrodes and a counter electrode arrangement arranged on a surface, the counter electrode arrangement comprising a main counter electrode portion and an opening extending along the counter electrode arrangement, the method comprising: the plurality of electrodes applying a time-varying potential to repel ions from the surface; and the counter electrode arrangement applying a direct current (DC) counter potential to force the ions toward the surface, the time-varying potential and the DC counter potential together confining the ions in the ion guide; wherein the counter electrode arrangement applies a stronger DC counter potential in a region adjacent to the main counter electrode portion than in a region adjacent to the opening, thereby confining the ions in the ion channel corresponding to the opening.

[0102] Unless otherwise stated, each feature disclosed in this specification can be replaced by an alternative feature for the same, equivalent or similar purpose. Therefore, unless otherwise stated, each feature disclosed is only an example of a series of equivalent or similar property features.

[0103] As used herein (including in the claims), unless the context indicates otherwise, the singular forms of the terms herein are to be understood to include the plural forms, and vice versa when the context permits. For example, unless the context indicates otherwise, the singular forms herein, including in the claims, such as "a / an" (such as an electrode or an electric potential), mean "one or more" (e.g., one or more electrodes, or one or more electric potentials). In the description and claims of the present disclosure, the words "comprises," "comprising," "having," and "containing," as well as variations of the words, such as "consisting of," and "consisting of," or the like, indicate that the described features include the following additional features, and the presence of other components is not intended to (and does not) be excluded.

[0104] The use of any and all examples or exemplary language ("for example," "such as," and similar language) provided herein is intended to better illustrate the present disclosure only and does not indicate a limitation on the scope of the present disclosure unless otherwise required. No language in this specification should be construed as indicating any non-claimed element necessary to practice the present disclosure.

[0105] Unless otherwise specified or the context requires otherwise, any steps described in this specification may be performed in any order or simultaneously. In addition, where a step is described as being performed after a step, this does not exclude intermediate steps being performed.

[0106] All aspects and / or features disclosed in this specification may be combined in any combination, except for combinations in which at least some of such features and / or steps are mutually exclusive. Specifically, preferred features of the present disclosure are applicable to all aspects and embodiments of the present disclosure and may be used in any combination. Similarly, features described in non-essential combinations may be used alone (not in combination).

[0107] Terms :

[0108] 1. An ion guide for guiding ions along an ion channel, the ion guide comprising:

[0109] a plurality of electrodes disposed on a surface of the ion guide and configured to apply a time-varying electric potential to repel the ions from the surface; and

[0110] a counter electrode arrangement comprising a main counter electrode portion and having an opening extending along the counter electrode arrangement, the counter electrode arrangement being configured to apply a direct current (DC) counter potential to force the ions towards the surface, the time-varying potential and the DC counter potential together confining the ions in the ion guide;

[0111] The counter electrode arrangement is configured to apply a stronger DC counter potential in a region adjacent to the main counter electrode portion than in a region adjacent to the opening, thereby confining the ions in an ion channel corresponding to the opening.

[0112] 2. An ion guide according to clause 1, wherein the opening and the ion channel are circuitous.

[0113] 3. An ion guide according to clause 1 or clause 2, wherein the opening and the ion channel are tortuous in two spatial dimensions or in three spatial dimensions.

[0114] 4. An ion guide according to any preceding clause, wherein the opening and the ion channel each comprises one or more first portions extending in a first direction and one or more second portions extending in a second direction different from the first direction.

[0115] 5. The ion guide according to clause 4, wherein the opening and the ion channel include one or more third portions extending in a third direction different from the first direction and the second direction.

[0116] 6. An ion guide according to clause 5, wherein:

[0117] The second direction and the third direction are substantially opposite directions; and / or

[0118] Those

[0119] The angle between the second direction and the third direction is greater than 90 degrees or greater than

[0120] 120 degrees.

[0121] 7. An ion guide according to any of clauses 4 to 6, wherein the first direction is substantially perpendicular to the second direction and / or the third direction.

[0122] 8. An ion guide according to any preceding clause, wherein the opening is an elongated opening in the counter electrode arrangement.

[0123] 9. An ion guide according to any preceding clause, wherein the counter electrode arrangement comprises a counter electrode and wherein the opening comprises a recess in the counter electrode.

[0124] 10. An ion guide according to clause 9, wherein a surface of the main counter electrode portion is a first distance away from the plurality of electrodes, and a surface of the opening is a second distance away from the plurality of electrodes, the second distance being greater than the first distance.

[0125] 11. An ion guide according to any preceding clause, wherein the opening extends at least partially through the counter electrode arrangement.

[0126] 12. An ion guide according to any preceding clause, wherein the opening extends completely through the counter electrode arrangement.

[0127] 13. An ion guide according to clause 12, wherein the counter electrode arrangement comprises a back plate located behind the opening, the back plate being configured to apply a weaker DC back potential to the ions than the main counter electrode part.

[0128] 14. An ion guide according to any preceding clause, wherein the counter electrode arrangement comprises one or more main counter electrode portions adjacent to the opening and / or located on each side of the opening.

[0129] 15. An ion guide according to any preceding clause, wherein the counter electrode arrangement is configured to apply a DC potential having a potential minimum corresponding to the opening and the ion channel.

[0130] 16. An ion guide according to any preceding clause, wherein the counter electrode is arranged substantially parallel to the surface on which the plurality of electrodes are arranged.

[0131] 17. An ion guide according to any preceding clause, wherein:

[0132] The time-varying potential is a radio frequency RF oscillating potential.

[0133] 18. An ion guide according to any preceding clause, wherein each electrode of the plurality of electrodes is configured to apply a potential having a different phase to each adjacent electrode of the plurality of electrodes.

[0134] 19. An ion guide according to any preceding clause, wherein the plurality of electrodes comprises an electrode set configured to apply a travelling wave potential along one or more portions of the ion channel to guide the ions along the ion channel.

[0135] 20. An ion guide according to any preceding clause, wherein the plurality of electrodes comprises a set of electrodes configured to apply a DC potential gradient along one or more portions of the ion channel to guide the ions along the ion channel.

[0136] 21. An ion guide according to clause 20 as appended to clause 19, wherein the electrode set of the plurality of electrodes is configured to apply an alternating current along a corresponding portion of the ion channel.

[0137] Alternating traveling wave potentials and DC potential gradients are used to guide the ions along the ion channel.

[0138] 22. An ion guide according to any preceding clause, wherein the plurality of electrodes are arranged along the length of the ion channel.

[0139] 23. An ion guide according to any preceding clause, wherein the electrode of the plurality of electrodes is an elongated electrode arranged substantially perpendicular to the ion channel.

[0140] 24. An ion guide according to any of the preceding clauses, wherein the counter electrode arrangement is inclined relative to the surface on which the plurality of electrodes are arranged, preferably wherein the opening extends in a first direction and wherein the counter electrode arrangement is inclined in a direction different from the first direction, so that the counter potential guides the ions along at least a portion of the ion channel.

[0141] 25. An ion guide according to any preceding clause, wherein the counter electrode arrangement is configured to apply a travelling wave potential along one or more portions of the ion channel to guide the ions along the ion channel.

[0142] 26. An ion guide according to any preceding clause, wherein the ion channel is

[0143] Any one or more of: cyclic; spiral; and / or circuitous in three dimensions.

[0144] 27. An ion guide according to any preceding clause, wherein the counter electrode arrangement at least partially surrounds the plurality of electrodes.

[0145] 28. An ion guide according to clause 27, wherein the opening in the counter electrode arrangement extends along one or more inner surfaces of the counter electrode arrangement.

[0146] 29. An ion guide according to any preceding clause, wherein the cross-section of the counter electrode arrangement is substantially parallelogram-shaped.

[0147] 30. An ion guide according to any preceding clause, wherein the counter electrode arrangement is tapered, curved, conical or frustoconical.

[0148] 31. An ion guide according to any preceding clause, wherein the surface on which the plurality of electrodes are arranged is cylindrical, conical or frustoconical.

[0149] 32. An ion guide according to any preceding clause, wherein the main counter electrode portion is substantially planar and / or wherein the surface on which the plurality of electrodes are arranged is substantially planar.

[0150] 33. An ion guide according to any of the preceding clauses, wherein the surface on which the plurality of electrodes are arranged is a first surface, and the ion guide further comprises a second plurality of electrodes arranged on a second surface of the ion guide, and the second plurality of electrodes are configured to apply a second time-varying electric potential to repel the ions from the second surface.

[0151] 34. An ion guide according to clause 33, wherein the second plurality of electrodes are arranged on a rear surface of the surface on which the first plurality of electrodes are arranged.

[0152] 35. An ion guide according to clause 33 or clause 34, wherein the first surface and the second surface are substantially parallel and / or substantially planar.

[0153] 36. An ion guide according to any of clauses 33 to 35, wherein the second surface is inclined relative to the first surface or substantially perpendicular to the first surface.

[0154] 37. An ion guide according to any one of clauses 33 to 36, wherein the second plurality of electrodes is configured to apply one or more travelling wave potentials and / or one or more DC potential gradient potentials along one or more portions of the ion channel to guide the ions along the ion channel.

[0155] 38. An ion guide according to any of clauses 33 to 37, wherein the ion channel extends from the first plurality of electrodes to the second plurality of electrodes.

[0156] 39. An ion guide according to any of clauses 33 to 38, further comprising a second counter electrode arrangement opposite the plurality of second electrodes.

[0157] 40. The ion guide of clause 39, wherein the opening is arranged along the first counter electrode and extends along the second counter electrode.

[0158] 41. An ion guide according to any of clauses 33 to 40, wherein the counter electrode arrangement at least partially surrounds the first plurality of electrodes and / or the second plurality of electrodes.

[0159] 42. An ion guide according to any of clauses 33 to 40, wherein the first plurality of electrodes and / or the second plurality of electrodes at least partially surround the counter electrode arrangement.

[0160] 43. An ion mobility separator comprising an ion guide according to any preceding clause.

[0161] 44. A mass spectrometry system comprising a mass analyser and a mass spectrometry system according to clauses 1 to 42.

[0162] An ion guide as described above or an ion mobility separator according to clause 43.

[0163] 45. An ion mobility spectrometer comprising a flowmeter according to clauses 1 to 42.

[0164] The ion guide described in any one of the preceding claims.

[0165] 46. ​​A method of directing ions along an ion channel of an ion guide, the ion guide comprising a plurality of electrodes arranged on a surface and a counter electrode arrangement, the counter electrode arrangement comprising a main counter electrode portion and an opening extending along the counter electrode arrangement, the method comprising:

[0166] The plurality of electrodes applies a time-varying potential to repel ions from the surface; and

[0167] The counter electrode arrangement applies a direct current (DC) counter potential to force the ions toward the surface, the time-varying potential and the DC counter potential together confining the ions in the ion guide;

[0168] The counter electrode is arranged to apply a stronger DC counter potential in a region adjacent to the main counter electrode portion than in a region adjacent to the opening, thereby confining the ions in an ion channel corresponding to the opening.

Claims

1. An ion guide for guiding ions along an ion channel, the ion guide comprising: a plurality of electrodes disposed on a surface of the ion guide and configured to apply a time-varying potential to repel the ions from the surface; and a counter electrode arrangement comprising a main counter electrode portion and having an opening extending along the counter electrode arrangement, the counter electrode arrangement being configured to apply a direct current (DC) counter potential to force the ions towards the surface, the time-varying potential and the DC counter potential together confining the ions in the ion guide; The counter electrode arrangement is configured to apply a stronger DC counter potential in a region adjacent to the main counter electrode portion than in a region adjacent to the opening, thereby confining the ions in an ion channel corresponding to the opening.

2. The ion guide of claim 1, wherein the opening and the ion channel are circuitous.

3. An ion guide according to claim 1 or claim 2, wherein the opening and the ion channel are tortuous in two spatial dimensions or in three spatial dimensions.

4. An ion guide according to any preceding claim, wherein the opening and the ion channel each comprises one or more first portions extending in a first direction and one or more second portions extending in a second direction different from the first direction. 5 . The ion guide of claim 4 , wherein the opening and the ion channel include one or more third portions extending in a third direction different from the first direction and the second direction.

6. The ion guide of claim 5, wherein: The second direction and the third direction are substantially opposite directions; and / or An angle between the second direction and the third direction is greater than 90 degrees or greater than 120 degrees.

7. The ion guide of any one of claims 4 to 6, wherein the first direction is substantially perpendicular to the second direction and / or the third direction.

8. An ion guide according to any preceding claim, wherein the opening is an elongate opening in the counter electrode arrangement.

9. An ion guide according to any preceding claim, wherein the counter electrode arrangement comprises a counter electrode and wherein the opening comprises a recess in the counter electrode.

10. The ion guide of claim 9, wherein a surface of the main counter electrode portion is at a first distance from the plurality of electrodes, and a surface of the opening is at a second distance from the plurality of electrodes, the second distance being greater than the first distance.

11. An ion guide according to any preceding claim, wherein the opening extends at least partially through the counter electrode arrangement.

12. An ion guide according to any preceding claim, wherein the opening extends completely through the counter electrode arrangement.

13. An ion guide according to claim 12, wherein the counter electrode arrangement comprises a back plate located behind the opening, the back plate being configured to apply a weaker DC back potential to the ions than the main counter electrode part.

14. An ion guide according to any preceding claim, wherein the counter electrode arrangement comprises one or more main counter electrode portions adjacent to the opening and / or on each side of the opening.

15. An ion guide according to any preceding claim, wherein the counter electrode arrangement is configured to apply a DC potential having a potential minimum corresponding to the opening and the ion channel.

16. An ion guide according to any preceding claim, wherein the counter electrode is arranged substantially parallel to the surface on which the plurality of electrodes are arranged.

17. An ion guide according to any preceding claim, wherein: The time-varying potential is a radio frequency (RF) oscillating potential; and / or Each electrode of the plurality of electrodes is configured to apply a potential having a different phase to each adjacent electrode of the plurality of electrodes.

18. An ion guide according to any preceding claim, wherein the plurality of electrodes comprises a collection of electrodes configured to apply a travelling wave potential along one or more portions of the ion channel to guide the ions along the ion channel.

19. An ion guide according to any preceding claim, wherein the plurality of electrodes comprises a set of electrodes configured to apply a DC potential gradient along one or more portions of the ion channel to guide the ions along the ion channel.

20. An ion guide according to claim 19 as appended to claim 18, wherein the electrode set of the plurality of electrodes is configured to apply alternating travelling wave potentials and DC potential gradients along respective portions of the ion channel to guide the ions along the ion channel.

21. An ion guide according to any preceding claim, wherein the plurality of electrodes are provided along the length of the ion channel.

22. An ion guide according to any preceding claim, wherein the electrodes of the plurality of electrodes are elongate electrodes arranged substantially perpendicular to the ion channel.

23. An ion guide according to any preceding claim, wherein the counter electrode arrangement is inclined relative to the surface on which the plurality of electrodes are arranged, preferably wherein the opening extends in a first direction and wherein the counter electrode arrangement is inclined in a direction different from the first direction, so that the counter potential guides the ions along at least a portion of the ion channel.

24. An ion guide according to any preceding claim, wherein the counter electrode arrangement is configured to apply a travelling wave potential along one or more portions of the ion channel to guide the ions along the ion channel.

25. An ion guide according to any preceding claim, wherein the ion channel is any one or more of: circular; helical; and / or tortuous in three dimensions.

26. An ion mobility separator comprising an ion guide according to any preceding claim.

27. A mass spectrometry system comprising a mass analyser and an ion guide according to any one of claims 1 to 25 or an ion mobility separator according to claim 26.

28. An ion mobility spectrometer comprising the ion guide according to any one of claims 1 to 25.

29. A method of directing ions along an ion channel of an ion guide, the ion guide comprising a plurality of electrodes arranged on a surface and a counter electrode arrangement, the counter electrode arrangement comprising a main counter electrode portion and an opening extending along the counter electrode arrangement, the method comprising: The plurality of electrodes applies a time-varying potential to repel ions from the surface; and the counter electrode arrangement applies a direct current (DC) counter potential to force the ions toward the surface, the time-varying potential and the DC counter potential together confining the ions in the ion guide; The counter electrode is arranged to apply a stronger DC counter potential in a region adjacent to the main counter electrode portion than in a region adjacent to the opening, thereby confining the ions in an ion channel corresponding to the opening.

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