Mass spectrometry system with ion mobility analyzer at elevated pressure

Abstract

The present invention provides a hybrid mass spectrometry system and a method for operating the hybrid mass spectrometry system, the system comprising an ion source, a first trapped ion mobility spectrometry (TIMS) analyzer and a mass analyzer, wherein the TIMS analyzer is located in a first vacuum chamber at an elevated pressure above 500 Pa and operates therein.

Description

Technical Field

[0001] The present invention relates to a hybrid mass spectrometry system in which trapped ion mobility spectrometry (TIMS) is coupled with mass spectrometry (MS), in particular tandem mass spectrometry (tandem MS), and a method of operating the hybrid mass spectrometry system. Background Art

[0002] Ion mobility spectrometry (IMS) is an analytical technique that is used to study the mobility of ions in a buffer gas and to separate them according to their mobility.

[0003] An inherent feature of ion mobility spectrometry is that the mobility of ions in a buffer gas depends on the molecular geometry of the ions, making it generally possible to resolve and therefore separate isomers or conformers that cannot be resolved by mass spectrometry. Many applications also exploit the ability to determine the cross section of an analyte ion from its measured mobility. Knowledge of the cross section has proven to be important in many fields, particularly in the field of structural biology, including identifying the class and detailed structure of a compound.

[0004] In trapped ion mobility spectrometry (TIMS), ions are first trapped by a counter-acting gas flow along a non-uniform DC electric field (electric field gradient, EFG) or by a counter-acting gas flow with a non-uniform axial velocity distribution (gas velocity gradient) along a uniform DC electric field. The trapped ions are first spatially separated in the TIMS analyzer according to mobility, and then the trapped ions are eluted from the TIMS analyzer over time according to their mobility by adjusting one of the gas velocity and the height of the axial DC electric field (Loboda's U.S. Patent No. 6,630,662 B1; Park's U.S. Patent No. 7,838,826 B1). TIMS analyzers operate in the low pressure range of 2 to 500 Pa and use RF electric fields to radially confine ions. For the theoretical basis of TIMS, see the article “Fundamentals of Trapped Ion Mobility Spectrometry” by Michelmann et al. (J. Am. Soc. Mass Spectrom., 2015, 26, 14-24).

[0005] U.S. Patent No. 9,683,964 (Park et al.) teaches a TIMS analyzer including a capture region and a separation region for parallel accumulation. The TIMS analyzer accumulates ions in the capture region, while pre-accumulated ions are analyzed in parallel in time in the separation region. The gas flow drives the ions against the slope of the reaction DC electric field barrier of the capture region, so that the ions are axially trapped and separated according to their mobility at the position along the slope. During the accumulation of ions in the capture region, the gas flow also drives the ions that have been accumulated in the previous accumulation and transferred to the separation region against the slope of the reaction DC electric field barrier of the separation region, so that the ions are axially trapped and spatially separated according to their mobility. After the separation region is loaded with the accumulated ions to be analyzed, the height of the reaction DC electric field barrier is steadily reduced, so that the ion species are released from the separation region in the order of their mobility.

[0006] Published U.S. patent application 2017 / 0350860 (Raether et al.) teaches that the radially confined RF field of a TIMS analyzer can be at least partially a hexapole, octupole, or higher order RF field.

[0007] U.S. Patent No. 10,241,079 (Park et al.) teaches a system comprising two TIMS analyzers with an ion gate between the two TIMS analyzers. The ion gate is used to select one or more ion species after being separated in an upstream TIMS analyzer for selective transmission to a downstream TIMS analyzer. A transient potential is applied to an electrode of the ion gate so as to reduce the transmission of ions in at least one limited mobility range, preferably so as to eliminate or at least substantially reduce unwanted ions, and so as to reduce the transmission of ion species of interest with high abundance to less than the transmission of ion species of interest with lower abundance.

[0008] There remains a need for a hybrid mass spectrometry system having one or more TIMS analyzers that can handle higher ion currents from an ion source in order to reduce the detection limit of low-abundance ion species. Summary of the invention

[0009] In a first aspect, the present invention provides a mass spectrometry system comprising an ion source, a first trapped ion mobility spectrometer (TIMS) analyzer and a mass analyzer, wherein the TIMS analyzer is located and operated in a first vacuum chamber at an elevated pressure above 500 Pa. The elevated pressure may be equal to or higher than 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa or 10000 Pa.

[0010] The TIMS analyzer can include a DC electric field gradient (ramp) and a reaction gas flow, which drives ions to counteract the DC electric field gradient so that the ions are axially trapped in the RF ion guide. The direction of the gas flow can be directed upstream toward the ion source or downstream away from the ion source. Most preferably, the DC electric field gradient is a rising edge of a DC electric field barrier with a vertex or plateau, and the reaction gas flow drives ions away from the ion source to counteract the barrier. The TIMS analyzer can also include a gas flow with a velocity gradient and a reaction (constant) DC electric field. Ions are radially constrained by an RF electric field. By adjusting the DC electric field and / or gas flow, the trapped ions are axially released from the ion guide according to their mobility.

[0011] The mass spectrometry system also includes a second TIMS analyzer, wherein the second TIMS analyzer is located downstream of the first TIMS analyzer. The second TIMS analyzer may also be located in the first vacuum chamber or the second vacuum chamber. The pressure in the second vacuum chamber is preferably lower than the pressure in the first vacuum chamber, for example, lower than 500 Pa, preferably between 100 Pa and 300 Pa. However, the pressure in the second vacuum chamber may also be equal to or higher than the pressure in the first vacuum chamber.

[0012] The mass spectrometry system may also include an ion gate between the two TIMS analyzers, which is preferably located at or near the exit of the first TIMS analyzer. The ion gate can be used to select one or more ion species after separation in the first TIMS analyzer for selective transfer to the second TIMS analyzer, as described in U.S. Patent No. 10,241,079 (Park et al.), or for tandem IMS. For selective transfer, the ion gate can be operated by adjusting the transmission of the ion gate so that the transmission of ions in at least one limited mobility range is reduced, preferably so that unwanted ion species are eliminated or at least substantially reduced, and the transmission of high abundance ion species of interest is lower than the transmission of lower abundance ion species of interest.

[0013] At least one or both TIMS analyzers preferably include an accumulation region for trapping and a mobility separation region.A TIMS analyzer (separator) with parallel accumulation is disclosed in US Pat. No. 9,683,964 (Park et al.).

[0014] The first TIMS analyser may be arranged in line with the second TIMS analyser. More preferably, the first TIMS analyser is arranged non-collinearly with the second TIMS analyser. Non-collinear arrangement means that the angle between the axis of the first TIMS analyser and the axis of the second TIMS analyser is substantially non-zero. The angle between the axis of the first TIMS analyser and the axis of the second TIMS analyser is greater than 10°, preferably greater than 45°, more preferably greater than 75°, in particular substantially 90° (orthogonal arrangement). The angle between the axis of the first TIMS analyser and the axis of the second TIMS analyser may be greater than 90°, for example greater than 90° and less than 120°. The first and / or second TIMS analyser may include an RF funnel at the entrance. In the non-collinear case, the second TIMS analyser preferably includes an RF funnel at its entrance.

[0015] The mass spectrometry system may also include an RF multipole between the first and second TIMS analyzers. The RF multipole may be arranged in line with the first TIMS analyzer or tilted at an angle of, for example, less than 20° relative to the first TIMS analyzer. The RF multipole is most preferably linear (two-dimensional) and may be straight or curved. The RF multipole is preferably located between the ion gate and the second TIMS analyzer, and may be, for example, one of an RF quadrupole, an RF hexapole, an RF octupole, and an RF ion tunnel. The RF multipole may operate as one of a mass filter, a mobility mass filter, an ion guide, a fragmentation cell, an activation cell, and an ion trap. The RF multipole may be completely located in the first or second vacuum chamber, or may transition from the first vacuum chamber to the second vacuum chamber. The RF multipole may also be located in an additional vacuum chamber, which is located between the first and second vacuum chambers and is separated from these vacuum chambers by a differential pumping stage, wherein the pressure in the additional vacuum chamber is preferably lower than the pressure in the first and second vacuum chambers.

[0016] The mass spectrometer system can include more than one ion source. One of the ion sources can be an atmospheric pressure ion source, which is coupled to the first vacuum chamber by a single transfer capillary, a plurality of transfer capillaries, a porous transfer capillary, a single hole and a plurality of holes. One of the ion sources can be a sub-ambient pressure ion source, which can be, for example, located upstream of the first TIMS analyzer or between the first TIMS analyzer and the second TIMS analyzer. Spray ionization (for example electrospray (ESI) or thermal spray), desorption ionization (for example matrix assisted laser / desorption ionization (MALDI) or secondary ionization), chemical ionization (CI), photoionization (PI), electron impact ionization (EI) and a gas discharge ionization can be used to generate ions.

[0017] The mass analyzer is one of a time-of-flight analyzer (particularly a time-of-flight analyzer with orthogonal ion injection), an electrostatic ion trap, an RF ion trap, an ion cyclotron frequency ion trap, and a quadrupole mass filter. The mass spectrometer system may also include a mass filter and / or a fragmentation cell between the ion mobility analyzer and the mass analyzer. Ions may be fragmented by collision-induced dissociation (CID), surface-induced dissociation (SID), photodissociation (PD), electron capture dissociation (ECD), electron transfer dissociation (ETD), collision activation after electron transfer dissociation (ETcD), activation (AI-ETD) occurring simultaneously with electron transfer dissociation, and by cracking with highly excited or free radical neutral particle reactions. Photodissociation preferably includes infrared multiphoton dissociation (IRMPD) or ultraviolet light dissociation (UVPD). For example, selected ions may be activated by multiphoton absorption or by collision-induced activation in a dipole or rotational AC electric field.

[0018] In a second aspect, the present invention provides a method for analyzing ions, comprising the steps of: providing ions from an ion source to a first TIMS analyzer; separating the ions according to mobility in the first TIMS analyzer at an elevated pressure greater than 500Pa; selecting at least one ion species of interest; transferring the selected ions of interest to a capture region of a second TIMS analyzer; separating the selected ions of interest in the second TIMS analyzer according to mobility; and analyzing the separated ions by mass spectrometry or tandem mass spectrometry. The ion current provided from the ion source to the first TIMS analyzer is lower than the ion current of the selected ions of interest transferred to the second TIMS analyzer. The elevated pressure may be equal to or greater than 1000Pa, 1500Pa, 2000Pa, 3000Pa, 5000Pa, or 10000Pa.

[0019] The step of selecting at least one ion species of interest preferably includes, for ions within at least one limited mobility range, reducing the transmission of ions to the second TIMS analyzer, preferably such that unwanted ion species are eliminated or at least substantially reduced, and more preferably such that the transmission for high abundance ion species of interest is lower than the transmission for lower abundance ion species of interest. For example, the selected ions may be from a single limited mobility range or from a plurality of non-overlapping mobility ranges.

[0020] Preferably, the selected ions of interest are separated in the second TIMS analyser at a pressure below 500 Pa, preferably between 100 Pa and 300 Pa. However, the selected ions of interest may also be separated in the second TIMS analyser at an elevated pressure equal to or above 500 Pa, 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa or 10000 Pa.

[0021] Preferably, the separation step and the selection step in the first TIMS analyzer are repeated, and the transferred ions of interest are accumulated in the capture region of the second TIMS analyzer before the transferred ions of interest are separated in the second TIMS analyzer. More preferably, in the second TIMS analyzer, the selected ions of interest are separated at a pressure below 500Pa, preferably between 100Pa and 300Pa, and the separation repetition rate in the first TIMS analyzer can be 2, 5, 10, 20 or 50 times the separation repetition rate in the second TIMS analyzer. Due to the operation of the first TIMS analyzer at an elevated pressure, the average mobility resolution of the first TIMS analyzer can be substantially equal to the average mobility resolution of the second TIMS analyzer, despite the much higher repetition rate and the much higher ion throughput. Alternatively, at the same repetition rate, the average mobility resolution of the first TIMS analyzer can be higher than the average mobility resolution of the second TIM analyzer. In a case where both TIMS analyzers are operated at elevated pressure, the first TIMS analyzer can be operated at a higher repetition rate (e.g., greater than 2, 5, 10, 20, or 50 times) and a lower resolution, while selected ions having reduced charge are analyzed in a second TIMS analyzer operating at a lower repetition rate and a higher mobility resolution, particularly at a mobility resolution equal to or greater than 500.

[0022] Prior to trapping in the trapping region of the second TIMS analyser, selected ions of interest may be further filtered based on their mass or a combination of their mass and mobility.

[0023] In a third aspect, the present invention provides a method for analyzing ions, comprising the steps of: providing ions from an ion source to a first TIMS analyzer; separating the ions according to mobility in the first TIMS analyzer at an elevated pressure greater than 500 Pa; selecting an ion species of interest from a limited range of mobilities; fragmenting or activating the selected ions of interest; transferring the fragment ions or activated ions to a capture region of a second TIMS analyzer; separating the fragment ions or activated ions according to mobility in the second TIMS analyzer; and analyzing the separated ions by mass spectrometry or tandem mass spectrometry. The elevated pressure may be equal to or greater than 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa or 10000 Pa.

[0024] Preferably, the selected ions of interest are separated in the second TIMS analyser at a pressure below 500 Pa, preferably between 100 Pa and 300 Pa. However, the selected ions of interest may also be separated in the second TIMS analyser at an elevated pressure equal to or above 500 Pa, 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa or 10000 Pa.

[0025] Preferably, the steps of separation, selection, and fragmentation or activation in the first TIMS analyzer are repeated, and the transferred fragment ions or activated ions are accumulated in the capture region of the second TIMS analyzer before separation in the second TIMS analyzer. More preferably, the separation repetition rate in the first TIMS analyzer is 2, 5, 10, 20 or 50 times higher than the separation repetition rate in the second TIMS analyzer. The average mobility resolution of the first TIMS analyzer may be substantially equal to or higher than the average mobility resolution of the second TIMS analyzer.

[0026] Prior to trapping the selected ions of interest in the trapping region of the second TIMS analyser, the selected ions of interest may be further filtered based on their mass or a combination of their mass and mobility.

[0027] The time scaling mode of the TIMS analyzer is described in U.S. Patent No. 8,766,176 (Park et al.) and includes adjusting the DC electric field and / or gas flow at a high scan rate outside the mobility range of interest and reducing the scan rate within the mobility range of interest to achieve high transient ion mobility resolution. The time scaling mode can be used during the separation in the first TIMS analyzer to increase the selectivity of the selection step because the scan rate of the first TIMS analyzer is transiently reduced for the ion species of interest. The mobility resolution of the first TIMS analyzer for the ion species of interest is improved compared to the average mobility resolution of the first TIMS analyzer.

[0028] Surprisingly, a TIMS analyser according to the present invention can handle higher ion currents from the ion source because, according to common sense, operation at elevated pressures reduces the RF pseudopotentials necessary to confine ions along the axis of the TIMS analyser without causing losses through discharge. Reducing the RF pseudopotentials results in reduced charge capacity, i.e., fewer ions can be trapped in the TIMS analyser, and a reduced ion current can be handled. The present invention is based on the idea that the effects of elevated pressure on the RF pseudopotentials are compensated, or even overcompensated, for the following reasons:

[0029] First, the increased pressure shifts the operating point of the TIMS analyzer away from the minimum of the Paschen curve and allows a higher RF voltage to be applied to the electrodes of the TIMS analyzer without arcing, thereby enhancing the RF pseudopotential.

[0030] Second, the increased pressure also shifts the stable region of ion motion, allowing higher RF voltages to be applied to the electrodes of the TIMS analyzer without resulting in unstable ion trajectories.

[0031] Third, the mobility resolution of the TIMS analyzer scales approximately with K -3 / 4 , so scale p 3 / 4 , where K is the mobility of the ion and p is the pressure. The average mobility resolution is approximately the same as (f TIMS ) -1 / 4 proportional to, where f TIMSis the repetition rate of the separation, i.e., a TIMS analyzer at elevated pressure can be operated at a higher repetition rate without giving up mobility resolution and therefore selectivity in the selection step. A higher repetition rate is advantageous because it reduces the accumulation of charge in the TIMS analyzer, i.e., the amount of charge per analysis. In addition, the ion species of interest are selected so that the ion current delivered to the downstream TIMS analyzer is smaller than the ion current entering the first TIMS analyzer, i.e., the amount of charge in the second TIMS analyzer is reduced. The selection step preferably includes substantially eliminating ion species that are not of interest and reducing high abundance ion species of interest compared to lower abundance ion species of interest.

[0032] Operation of the TIMS analyzer at elevated pressure enables selection of ion species of interest at increased repetition rates without loss of selectivity compared to operation at lower pressures. In summary, much higher ion currents from the ion source can be analyzed using a TIMS analyzer at elevated pressures, which results in a lower limit of detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1A A schematic diagram of a first exemplary mass spectrometry system (100) is shown, which includes an ion source (101) having an RF funnel and a first TIMS analyzer, an ion gate (10), a second TIMS analyzer (102), a mass filter (103), a fragmentation cell (104), and a mass analyzer (105).

[0034] Figure 1B The ion source (101) with the RF funnel and the first TIMS analyser, the ion gate (10) and the second TIMS analyser (102) of the mass spectrometry system (100) are shown in more detail.

[0035] Figure 2A A schematic diagram of a second exemplary mass spectrometry system (200) is shown, which includes an ion source (201) having an RF funnel and a first TIMS analyzer, an ion gate (10), an RF quadrupole (11A), a laser system (12), a second TIMS analyzer (202), a mass filter (203), a fragmentation cell (204) and a mass analyzer (205).

[0036] Figure 2B The ion source (201) with RF funnel and first TIMS analyser, ion gate (10), RF quadrupole (11a), laser system (12) and second TIMS analyser (202) of the mass spectrometry system (200) are shown in more detail.

[0037] Figure 3AA schematic diagram of a third exemplary mass spectrometry system (300) is shown, which includes an ion source (301) having a first TIMS analyzer, an ion gate (10), a second TIMS analyzer (302), a mass filter (303), a fragmentation cell (304) and a mass analyzer (305).

[0038] Figure 3B The mass spectrometry system (300) is shown in more detail with an ion source (301) having a first TIMS analyser, an ion gate (10) and a second TIMS analyser (302).

[0039] Figure 4A A schematic diagram of a fourth exemplary mass spectrometry system (400) is shown, which includes an ion source (401) having two TIMS analyzers, a mass filter (403), a fragmentation cell (404), and a mass analyzer (405).

[0040] Figure 4B An ion source (401) having two TIMS analysers of a mass spectrometry system (400) is shown in more detail. DETAILED DESCRIPTION

[0041] Although the present invention has been shown and described with reference to a plurality of different embodiments of the present invention, it will be appreciated by those skilled in the art that combinations of embodiments and changes in form and detail may be made without departing from the scope of the present invention as defined by the appended claims. The present invention may be better understood by reference to the following drawings. The elements in the drawings are not necessarily to scale, and emphasis is placed on illustrating the principles of the present invention (usually schematically). In different figures, the same or functionally equivalent elements are marked with the same reference numerals.

[0042] Figure 1A A schematic diagram of a first example of a mass spectrometry system according to the present invention is shown. The mass spectrometry system (100) comprises an ion source (101) having an RF funnel and a first TIMS analyzer, an ion gate (10), a second TIMS analyzer (102), a mass filter (103), a fragmentation cell (104) and a mass analyzer (105). The mass analyzer (105) is preferably a time-of-flight analyzer (OTOF-MS) with orthogonal ion injection.

[0043] Figure 1B The ion source (101) with the RF funnel and the first TIMS analyser, the ion gate (10) and the second TIMS analyser (102) are shown in more detail.

[0044] The ion source (101) comprises two chambers (1a, 1b).

[0045] The chamber (1a) is maintained at atmospheric pressure and includes an electrospray ion source (spray emitter (3a), spray plume (4a)). Ions from the spray plume (4a) are introduced into the first vacuum chamber (1b) via a transfer capillary (2) and then deflected into the RF funnel (7a) by a repulsive DC potential applied to a deflector electrode (6a). The transfer capillary is preferably a short, large-bore capillary having an inner diameter of 1 mm or more and a length of 180 mm or less.

[0046] The vacuum chamber (1b) is maintained at an elevated pressure of about 2000 Pa and includes a sub-ambient electrospray source (spray emitter (3b), spray plume (4b). The spray emitter (3b) is positioned in the hole of the deflector electrode (6a). Ions from the spray plume (4b) are introduced directly into the inlet of the RF funnel (7a).

[0047] The electrospray ion sources (3a, 4a) and (3b, 4b) may be operated simultaneously or separately from each other. A separation device (not shown) such as a liquid chromatography device or an electrophoresis device may be coupled to the spray emitters (3a, 3b).

[0048] The RF funnel (7a) is an octupole RF funnel known from published US patent application 2004 / 0195503 (Park et al.). It is constructed as a stack of segmented apertured electrodes. Each apertured electrode comprises eight segments. The apertures of the electrodes taper to a smaller diameter, thereby forming a funnel-shaped internal volume. Two phases of RF voltage are applied alternately to adjacent segments of each single electrode and adjacent segments of adjacent electrodes. The generated RF pseudopotential keeps ions away from the inner wall of the RF funnel (7a).

[0049] The ions are driven by a gas flow (8a) into a first TIMS analyzer comprising a capture region (9a) and a separation region (9b). The gas flow (8a) is generated by pumping gas out of a vacuum chamber (1b) at the outlet of the separation region (9b). An octopole RF funnel (7a) enables a smooth transition to the RF field of the capture region (9a). The combined length of the two regions (9a) and (9b) is approximately 7 cm. The inlet portion of the capture region (9a) is constructed as a segmented RF octopole, which transitions to a segmented RF quadrupole. The separation region (9b) is constructed similarly to the capture region (9a), wherein an upstream segmented RF octopole transitions to a downstream segmented RF quadrupole. The octopole portion has a larger charge capacity per unit volume than the quadrupole portion.

[0050] The first TIMS analyzer is preferably operated in a parallel accumulation mode, i.e. the first TIMS analyzer accumulates ions in the capture region (9a) while analyzing pre-accumulated ions in parallel in time in the separation region (9b). The gas flow (8a) drives the ions leaving the RF funnel (7a) against the slope of the reaction DC electric field barrier of the capture region (9a), so that the ions are axially trapped and separated according to their mobility at the position along the slope. During the accumulation of ions in the capture region (9a), the gas flow (8a) also drives the ions that have been accumulated in the previous accumulation and transferred to the separation region (9b) against the slope of the reaction DC electric field barrier of the separation region (9b), so that the ions are axially trapped and spatially separated according to their mobility. After the separation region (9b) is loaded with the ions to be analyzed, the height of the reaction DC electric field barrier is steadily reduced, so that the ion species are released from the separation region (9b) in the order of their mobility. The velocity of the gas flow (8a) is of the order of 100 m / s and the operating pressure of the first TIMS analyser is substantially 2000 Pa.

[0051] The second TIMS analyzer (102) comprises a quadrupole RF funnel (7b), a capture region (9c) and a separation region (9d). The first TIMS analyzer (9a, 9b) and the second TIMS analyzer (9c, 9d) are arranged orthogonally, that is, the relative angle between the common axis of the regions (9a, 9b) and the common axis of the regions (9c) and (9d) is substantially 90°.

[0052] The pressure of the vacuum chamber (1c) of the second TIMS analyzer (102) is maintained lower than the pressure of the first vacuum chamber (1b), preferably at about 200Pa. The ions introduced into the vacuum chamber (1c) are deflected into the quadrupole RF funnel (7b) by the repulsive DC potential applied to the deflector electrode (6b), and then guided into the capture region (9c) toward the outlet of the quadrupole RF funnel (7b) by the gas flow (8b). The gas flow (8b) is generated by pumping gas out of the vacuum chamber (1c) at the outlet of the separation region (9d). The speed of the gas flow (8b) is of the order of 100m / s, and the operating pressure of the second TIMS analyzer (102) is substantially 200Pa.

[0053] Similar to the first TIMS analyser (9a, 9b), the second TIMS analyser (102) is preferably operated in parallel accumulation mode as described above, ie, ions are accumulated in the trapping region (9c) while the pre-accumulated ions are analysed in parallel in the separation region (9d).

[0054] The vacuum chamber ( 9d ) and mass filter ( 103 ) are connected through the pumping ports ( 5a - 5c ) and through the separation zone ( 9d ). Figure 1B An adjacent outlet (not shown) pumps gas out of the ion source (101) and the second TIMS analyzer (102).

[0055] The ion gate (10) is an ion einzel lens. Other embodiments may include a Tyndall gate or a Bradbury-Nielsen gate operated with a DC voltage, wherein positive and negative DC potentials are alternately supplied to the gate's wires. Alternatively, the Bradbury-Nielsen gate may be operated with an RF potential, thereby forming a reflection pseudopotential around the wires. The RF Bradbury-Nielsen gate presents the additional advantage of reflecting high mobility ions while transmitting low mobility ions, with the transmission limit being dependent on the RF frequency and the voltage on the wires (gate control voltage).

[0056] The first TIMS analyzer (9a, 9b) and the second TIMS analyzer (9c, 9d) may be operated in a selective delivery mode as described in U.S. Patent No. 10,241,079 (Park et al.), comprising the steps of:

[0057] providing ions from an atmospheric pressure ESI ion source (3a, 4a) and / or from a sub-ambient ESI ion source (3c, 4c) to a first TIMS analyzer (9a, 9b);

[0058] separating the ions according to mobility in a first TIMS analyzer (9a, 9b) at an elevated pressure of 2000 Pa;

[0059] applying a transient DC potential to electrodes of the ion gate (10) to modulate transmission of the ion gate (10) and select ion species of interest;

[0060] transferring the selected ions to a capture region (9c) of a second TIMS analyzer (102);

[0061] separating the selected ions according to mobility in a second TIMS analyzer (102); and

[0062] The separated ions are analyzed by mass spectrometry or tandem mass spectrometry using a downstream mass analyzer (105) and optionally a downstream mass filter (103) and fragmentation cell (104).

[0063] Preferably, the ion gate (10) is operated by adjusting the transmission of the ion gate so that the transmission of ions in at least one limited mobility range is reduced. Preferably, the ion gate (10) is operated so that unwanted ion species are eliminated or at least substantially reduced, and the transmission of ion species of interest with high abundance is lower than the transmission of ion species of interest with lower abundance.

[0064] Preferably, the separation step and the selection step in the first TIMS analyser (9a, 9b) are repeated and the transferred ions are accumulated in a capture region (9c) of a second TIMS analyser (102) before transferring them to a separation region (9d) and separating them therein.

[0065] The first TIMS analyzer (9a, 9b) and the second TIMS analyzer (9c, 9d) may also be operated in a tandem IMS mode, comprising the following steps:

[0066] providing ions from an atmospheric pressure ESI ion source (3a, 4a) and / or from a sub-ambient ESI ion source (3c, 4c) to a first TIMS analyzer (9a, 9b);

[0067] separating the ions according to mobility in a first TIMS analyzer (9a, 9b) at an elevated pressure of 2000 Pa;

[0068] applying a transient DC potential to electrodes of the ion gate (10) to modulate transmission of the ion gate (10) and select an ion species of interest;

[0069] fragmenting the selected ions by accelerating the selected ions into a vacuum chamber (1c) using a DC potential applied to electrodes of an ion gate (10);

[0070] passing the fragment ions to a capture region (9c) of a second TIMS analyzer (102);

[0071] separating the fragment ions according to mobility in a second TIMS analyzer (102); and

[0072] The separated fragment ions are analyzed by mass spectrometry or tandem mass spectrometry using a downstream mass analyzer (105) and optionally a downstream mass filter (103) and fragmentation cell (104).

[0073] Preferably, the steps of separation, selection, fragmentation or activation in the first TIMS analyzer (9a, 9b) and transfer of the fragmented or activated ions are repeated multiple times before the resulting accumulated ions in the capture region (9c) of the second TIMS analyzer (102) are transferred to the separation region (9d) and separated therein.

[0074] When the average mobility resolution R is between about 75 and 40, the repetition rate of the separation in the second TIMS analyzer (9c, 9d) is preferably between 10 Hz and 100 Hz, respectively. The first TIMS analyzer (9a, 9b) is operated at a pressure 10 times higher than the operating pressure of the second TIMS analyzer (9c, 9d), and can be operated at a repetition rate 5 times higher than the repetition rate of the second TIMS analyzer (9c, 9d), so that the mobility resolution of the first TIMS analyzer is still about 3.8 times higher (=10 3 / 4 ·5 -1 / 4 ). Operation at elevated pressure results in better selectivity and ion throughput.

[0075] Figure 2A A schematic diagram of a second example of a mass spectrometry system according to the present invention is shown. The mass spectrometry system (200) comprises an ion source (201) having an RF funnel and a first TIMS analyzer, an ion gate (10), an RF quadrupole (11a), a laser system (12), a second TIMS analyzer (202), a mass filter (203), a fragmentation cell (204) and a mass analyzer (205). The mass analyzer (205) is preferably a time-of-flight analyzer (OTOF-MS) with orthogonal ion injection.

[0076] Figure 2B The ion source (201) with the RF funnel and the first TIMS analyser, the ion gate (10), the RF quadrupole (11a), the laser system (12) and the TIMS analyser (202) are shown in more detail.

[0077] The mass spectrometry system (200) differs from the mass spectrometry system (100) in that:

[0078] The ion gate (10) is located in the first vacuum chamber (1b);

[0079] An RF quadrupole (11a) bridges the vacuum chambers (1b) and (1c);

[0080] An additional sub-ambient MALDI source is located in the vacuum chamber (1c); and

[0081] A laser system (12) for generating photons and introducing the photons into the RF quadrupole (11a).

[0082] As in the mass spectrometry system (100), the ion gate (10) can be operated in a selective transfer mode or a tandem IMS mode. In selective transfer, a transient DC potential is applied to the electrodes of the ion gate (10) to regulate the transmission of ions that have been separated according to mobility in the separation region (9b) of the first TIMS analyzer. In the tandem IMS mode, a transient DC potential is applied to the electrodes of the ion gate (10) so that an ion species of interest is selected and fragmented by accelerating the selected ions into the RF quadrupole (11a) using the DC potential applied to the electrodes of the ion gate (10).

[0083] The RF quadrupole (11a) can be operated as a fragmentation cell using CID or photodissociation (PD) (e.g., in tandem TIMS mode), as an activation cell using collision induced activation (CIA) or photon induced activation (PA), or as a combined mass mobility filter. Ions introduced from the first TIMS analyzer (9a, 9b) can be trapped in the RF quadrupole (11a) by applying an appropriate DC potential to the exit electrode (11b).

[0084] The MALDI source comprises a MALDI plate (3c), a MALDI plume (4c) and a MALDI laser (3e). Ions introduced into a vacuum chamber (1c) via an RF quadrupole (11a) are deflected to the entrance of an RF funnel (7b) by a repulsive DC potential applied to the MALDI plate (3c) or a replacement electrode (not shown). Ions from the MALDI plume (4c) are directly introduced into the entrance of an RF funnel (7b).

[0085] The laser system (13) can generate photons in at least one of the vacuum ultraviolet range (VUV), the ultraviolet range (UV) and the infrared (IR) range. The photons can be used for single photon induced dissociation (PD) such as by VUVPD or UVPD, or for infrared multiphoton induced dissociation (IRMPD) or for infrared multiphoton activation (IRMPA). Optionally, the MALDI laser (3e) and the laser system (13) can be a single multi-wavelength laser system, such as a diode pumped solid-state Nd:YAG laser system. The basic principle of the Nd:YAG laser system at a wavelength of 1064nm or the pump light generated by a laser light emitting diode can be used for IRMPD or IRMPA, the third harmonic at a wavelength of 355nm can be used as the light source of the MALDI source (3c, 4c) of the sub-ambient, and the fourth harmonic at a wavelength of 266nm can be used for UVPD and optionally for post-ionization of the MALDI process.

[0086] For example, in the case where the photon-induced activation or fragmentation is not fast enough to induce fragmentation or activation during the time required for the ion to pass through the RF quadrupole (11a) (i.e., without trapping), it is necessary to trap the ion within the RF quadrupole (11a). The time required to induce fragmentation depends on the absorption cross section of the ion and the photon density in the RF quadrupole (11a).

[0087] The mass spectrometry system (200) is capable of multiple operating modes for hybrid IMS / MS analysis:

[0088] MS (without IMS separation)

[0089] Tandem MS (without IMS separation)

[0090] IMS separation / (tandem)MS

[0091] IMS separation with selection / IMS separation / (tandem) MS

[0092] IMS separation with selection / mass mobility filtration / (tandem)MS

[0093] Tandem IMS / (tandem)MS with fragmentation by CID or PD

[0094] Tandem IMS and mass mobility filtration / (tandem)MS with fragmentation by CID or PD

[0095] Figure 3A A schematic diagram of a third example of a mass spectrometry system according to the present invention is shown. The mass spectrometry system (300) comprises an ion source (301) having a first TIMS analyzer, an ion gate (10), a second TIMS analyzer (302), a mass filter (303), a fragmentation cell (304) and a mass analyzer (305). The mass analyzer (305) is preferably a time-of-flight analyzer (OTOF-MS) with orthogonal ion injection.

[0096] Figure 3B The ion source (301) with a first TIMS analyser, the ion gate (10) and the second TIMS analyser (302) are shown in more detail.

[0097] The ion source (301) comprises two chambers (1a, 1b).

[0098] The chamber (1a) is maintained at atmospheric pressure and includes an electrospray ion source (spray emitter (3a), spray plume (4a)). Ions from the spray plume (4a) are introduced into the first vacuum chamber (1b) via a transfer capillary (2) and then deflected into the RF funnel (7a) by a repulsive DC potential applied to a deflector electrode (6a). The transfer capillary is preferably a short, large-bore capillary having an inner diameter of 1 mm or more and a length of 180 mm or less.

[0099] The vacuum chamber (1b) is maintained at an elevated pressure of about 3000 Pa and includes a sub-ambient electrospray source (spray emitter (3b), spray plume (4b)). The spray emitter (3b) is positioned in the hole of the deflector electrode (6a). Ions from the spray plume (4b) are introduced directly into the inlet of the RF funnel (7a).

[0100] The electrospray ion sources (3a, 4a) and (3b, 4b) may be operated simultaneously or separately from each other. A separation device (not shown) such as a liquid chromatography device or an electrophoresis device may be coupled to the spray emitters (3a, 3b).

[0101] The RF funnel (7a) is an octupole RF funnel known from published US patent application 2004 / 0195503 (Park et al.). It is constructed as a stack of segmented apertured electrodes. Each apertured electrode comprises eight segments. The apertures of the electrodes taper to a smaller diameter, thereby forming a funnel-shaped internal volume. Two phases of RF voltage are applied alternately to adjacent segments of each single electrode and adjacent segments of adjacent electrodes. The generated RF pseudopotential keeps ions away from the inner wall of the RF funnel (7a).

[0102] The ions are driven by a gas flow (8a) into a first TIMS analyzer, which includes a capture region (9a) and a separation region (9b). The gas flow (8a) is generated by pumping gas out of a vacuum chamber (1b) at the outlet of the separation region (9b). An octopole RF funnel (7a) enables a smooth transition to the RF field of the capture region (9a). The combined length of the two regions (9a) and (9b) is about 10 cm. The inlet portion of the capture region (9a) is constructed as a segmented RF octopole, which transitions to a segmented RF quadrupole. The separation region (9b) is constructed similarly to the capture region (9a), wherein an upstream segmented RF octopole transitions to a downstream segmented RF quadrupole. The octopole portion has a larger unit volume space capacity than the quadrupole portion.

[0103] The first TIMS analyzer is preferably operated in a parallel accumulation mode, i.e. the first TIMS analyzer accumulates ions in the capture region (9a) and analyzes the pre-accumulated ions in parallel in time in the separation region (9b). The gas flow (8a) drives the ions leaving the RF funnel (7a) against the slope of the reaction DC electric field barrier of the capture region (9a), so that the ions are axially trapped and separated according to their mobility at the position along the slope. During the accumulation of ions in the capture region (9a), the gas flow (8a) also drives the ions that have been accumulated in the previous accumulation and transferred to the separation region (9b) against the slope of the reaction DC electric field barrier of the separation region (9b), so that the ions are axially trapped and spatially separated according to their mobility. After the separation region (9b) is loaded with the ions to be analyzed, the height of the reaction DC electric field barrier is steadily reduced, so that the ion species are released from the separation region (9b) in the order of their mobility. The velocity of the gas flow (8a) is of the order of 100 m / s and the operating pressure of the first TIMS analyser is substantially 3000 Pa.

[0104] The second TIMS analyzer (302) includes a capture region (9c) and a separation region (9d). Ions are introduced directly into the capture region (9c) of the second TIMS analyzer (302) from the outlet of the separation region (9b) of the first TIMS analyzer. The first TIMS analyzer (9a, 9b) and the second TIMS analyzer (9c, 9d) are arranged in a colinear manner, that is, the relative angle between the common axis of the regions (9a, 9b) and the common axis of the regions (9c) and (9d) is zero. Similar to the first TIMS analyzer (9a, 9b), the second TIMS analyzer (302) is preferably operated in a parallel accumulation mode as described above, that is, ions are accumulated in the capture region (9c), and the pre-accumulated ions are analyzed in parallel in the separation region (9d).

[0105] The pressure of the vacuum chamber (1c) of the second TIMS analyzer (302) is maintained lower than the pressure of the first vacuum chamber (1b), preferably at about 150 Pa. A gas flow (8b) is generated by pumping gas out of the vacuum chamber (1c) at the outlet of the separation zone (9d). The velocity of the gas flow (8b) is of the order of 100 m / s.

[0106] The ion gate (10) is an ion einzel lens. Other embodiments may include a Tyndall gate or a Bradbury-Nielsen gate. The first TIMS analyzer (9a, 9b) and the second TIMS analyzer (9c, 9d) may be operated in a selective transfer mode as described in U.S. Patent No. 10,241,079 (Park et al.), comprising the steps of:

[0107] providing ions from an atmospheric pressure ESI ion source (3a, 4a) and / or from a sub-ambient ESI ion source (3c, 4c) to a first TIMS analyzer (9a, 9b);

[0108] separating the ions according to mobility in a first TIMS analyzer (9a, 9b) at an elevated pressure of 3000 Pa;

[0109] applying a transient DC potential to electrodes of the ion gate (10) to modulate transmission of the ion gate (10) and select ion species of interest;

[0110] transferring the selected ions to a capture region (9c) of a second TIMS analyzer (302);

[0111] separating the selected ions according to mobility in a second TIMS analyzer (302); and

[0112] The separated ions are analyzed by mass spectrometry or tandem mass spectrometry using a downstream mass analyzer (305) and optionally a downstream mass filter (303) and fragmentation cell (304).

[0113] Preferably, the ion gate (10) is operated by adjusting the transmission of the ion gate so as to reduce the transmission of ions within at least one limited mobility range, preferably so as to eliminate or at least substantially reduce unwanted ion species, and so as to reduce the transmission of high abundance ion species of interest below the transmission of lower abundance ion species of interest.

[0114] Preferably, the steps of separating, selecting and transferring ions in the first TIMS analyser (9a, 9b) are repeated multiple times before the resulting accumulated ions in the capture region (9c) of the second TIMS analyser (302) are transferred to the separation region (9d) and separated therein.

[0115] The first TIMS analyzer (9a, 9b) and the second TIMS analyzer (9c, 9d) may also be operated in a tandem IMS mode, comprising the following steps:

[0116] providing ions from an atmospheric pressure ESI ion source (3a, 4a) and / or from a sub-ambient ESI ion source (3c, 4c) to a first TIMS analyzer (9a, 9b);

[0117] separating the ions according to mobility in a first TIMS analyzer (9a, 9b) at an elevated pressure of 3000 Pa;

[0118] applying a transient DC potential to electrodes of the ion gate (10) to modulate transmission of the ion gate (10) and select an ion species of interest;

[0119] fragmenting the selected ions by accelerating the selected ions into a vacuum chamber (1c) using a DC potential applied to electrodes of an ion gate (10);

[0120] passing the fragment ions to a capture region (9c) of a second TIMS analyzer (302);

[0121] separating the fragment ions according to mobility in the second TIMS analyzer (302); and

[0122] The separated fragment ions are analyzed by mass spectrometry or tandem mass spectrometry using a downstream mass analyzer (305) and optionally a downstream mass filter (303) and fragmentation cell (304).

[0123] Preferably, the separation, selection and fragmentation or activation steps in the first TIMS analyser (9a, 9b) are repeated and the transferred fragment ions or activated ions are accumulated in the capture region (9c) of the second TIMS analyser (302) before being transferred to the separation region (9d) and separated therein.

[0124] The separation repetition rate in the second TIMS analyzer (9c, 9d) may be, for example, about 50 Hz, and the average mobility resolution R is 60. The first TIMS analyzer (9a, 9b) operates at a pressure 20 times higher than the operating pressure of the second TIMS analyzer (9c, 9d), and may, for example, operate at a repetition rate 10 times higher than the repetition rate of the second TIMS analyzer (9c, 9d), so that the mobility resolution of the first TIMS analyzer is still 5.3 times higher (=20 3 / 4 10 -1 / 4 ). Operation at elevated pressure results in better selectivity and ion throughput.

[0125] Figure 4A A schematic diagram of a fourth example of a mass spectrometry system according to the present invention is shown. The mass spectrometry system (400) comprises an ion source (401) with two TIMS analyzers, a mass filter (403), a fragmentation cell (404) and a mass analyzer (405). The mass analyzer (405) is preferably a time-of-flight analyzer (OTOF-MS) with orthogonal ion injection.

[0126] Figure 4B An ion source (401) and ion gate (10B) with two TIMS analysers are shown.

[0127] The ion source (401) comprises two chambers (1a, 1b). Chamber (1a) is maintained at atmospheric pressure and comprises an electrospray ion source (spray emitter (3a), spray plume (4a)). Ions from the spray plume (4a) are introduced into the first vacuum chamber (1b) via a transfer capillary (2) and then deflected into the RF funnel (7a) by a repulsive DC potential applied to the deflector electrode (6a). The transfer capillary is preferably a short large-bore capillary with an inner diameter of 1 mm or greater and a length of 180 mm or less. The vacuum chamber (1b) is maintained at an elevated pressure of about 2000 Pa and comprises a sub-ambient electrospray source (spray emitter (3b), spray plume (4b)). The spray emitter (3b) is positioned in the hole of the deflector electrode (6a). Ions from the spray plume (4b) are directly introduced into the entrance of the RF funnel (7a). The electrospray ion sources (3a, 4a) and (3b, 4b) may be operated simultaneously or separately from each other. A separation device (not shown) such as a liquid chromatography device or an electrophoresis device may be coupled to the spray emitters (3a, 3b).

[0128] The RF funnel (7a) is a quadrupole RF funnel known from published US patent application 2004 / 0195503 (Park et al.). It is constructed as a stack of segmented apertured electrodes. Each apertured electrode comprises four segments. The apertures of the electrodes taper to a smaller diameter, thereby forming a funnel-shaped internal volume. Two phases of RF voltage are applied alternately to adjacent segments of each single electrode and adjacent segments of adjacent electrodes. The generated RF pseudopotential keeps ions away from the inner wall of the RF funnel (7a).

[0129] The first TIMS analyzer (9a, 9b) and the second TIMS analyzer (9c, 9d) are located in the same vacuum chamber (1b). Each TIMS analyzer includes a capture region (9a, 9c) and a separation region (9b, 9d). The first TIMS analyzer (9a, 9b) and the second TIMS analyzer (9c, 9d) are arranged in a colinear manner, that is, the relative angle between the common axis of the regions (9a, 9b) and the common axis of the regions (9c) and (9d) is substantially zero.

[0130] The ions are driven by a gas flow (8a) into the capture region (9a) of the first TIMS analyser. The gas flow (8a) is generated by pumping gas out of a vacuum chamber (1b) at the outlet of the separation region (9d) of the second TIMS analyser. The quadrupole RF funnel (7a) enables a smooth transition to the RF field of the capture region (9a). The combined length of the two regions (9a) and (9b) is about 7 cm. The capture regions (9a, 9c) and the separation regions (9b, 9d) are constructed as segmented RF quadrupoles.

[0131] Both TIMS analyzers are preferably operated in parallel accumulation mode, that is, the TIMS analyzers accumulate ions in the capture region (9a, 9c) and analyze the pre-accumulated ions in parallel in time in the separation region (9b, 9d). The gas flow (8a) drives the ions against the slope of the reaction DC electric field barrier of the capture region (9a, 9c), so that the ions are axially trapped and separated according to their mobility at the position along the slope. During the accumulation of ions in the capture region (9a, 9c), the gas flow (8a) also drives the ions that have accumulated in the previous accumulation and transferred to the separation region (9b, 9d) against the slope of the reaction DC electric field barrier of the separation region (9b, 9d), so that the ions are axially trapped and spatially separated according to their mobility. After the separation region (9b, 9d) is loaded with the ions to be analyzed, the height of the reaction DC electric field barrier is steadily reduced, so that the ion species are released from the separation region (9b) in the order of their mobility. The velocity of the gas flow (8a) is of the order of 100 m / s and the operating pressure of the two TIMS analysers is substantially 2000 Pa.

[0132] The ion gate (10b) is an ion single lens. It is located between the separation region (9b) and the capture region (9c) and is closed so that the gas flow (8a) can pass through the two TIMS analyzers. The first TIMS analyzer (9a, 9b) and the second TIMS analyzer (9c, 9d) can be operated in a selective transmission mode, as described in U.S. Patent No. 10,241,079 (Park et al.). Preferably, the ion gate (10b) is operated by adjusting the transmission of the ion gate (10b) so that the ion transmission in at least one limited mobility range is reduced, preferably so that unwanted ion species are eliminated or at least substantially reduced.

[0133] The repetition rate of the separation of the two TIMS analyzers can be, for example, 100 Hz when the average mobility resolution R is above 200. Operation at elevated pressure results in high mobility resolution and ion throughput. At an average mobility resolution of about 170, the repetition rate of the separation of the first TIMS analyzer (9a, 9b) can be, for example, 200 Hz, while in the second TIMS analyzer (9c, 9d) ions of reduced charge, such as selected from a limited mobility range, are selected and analyzed at a repetition rate of only 10 Hz at a mobility resolution of 420.

Claims

1. A mass spectrometry system comprising an ion source, a first TIMS analyzer, a second TIMS analyzer and a mass analyzer, wherein: In the first TIMS analyzer, ions are radially confined by an RF electric field; the first TIMS analyzer is located in a first vacuum chamber at an elevated pressure above 500 Pa and operates in the first vacuum chamber; the second TIMS analyzer is located downstream of the first TIMS analyzer, and the repetition rate of separation in the first TIMS analyzer is at least 2 times higher than the repetition rate of separation in the second TIMS analyzer.

2. The mass spectrometry system according to claim 1, wherein: The elevated pressure is equal to or higher than 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa or 10000 Pa.

3. The mass spectrometry system according to claim 1, further comprising an ion gate, wherein: The ion gate is located between the first TIMS analyzer and the second TIMS analyzer.

4. The mass spectrometry system according to claim 3, wherein: The second TIMS analyzer is located in the first vacuum chamber at the elevated pressure.

5. The mass spectrometry system according to claim 3, wherein: The second TIMS analyzer is located in a second vacuum chamber.

6. The mass spectrometry system according to claim 5, wherein: The pressure in the second vacuum chamber is higher than the pressure in the first vacuum chamber.

7. The mass spectrometry system according to claim 5, wherein: The pressure in the second vacuum chamber is lower than the pressure in the first vacuum chamber.

8. The mass spectrometry system according to claim 7, wherein: The pressure in the second vacuum chamber is lower than 500 Pa.

9. The mass spectrometry system according to claim 7, wherein: The pressure in the second vacuum chamber is between 100 Pa and 300 Pa.

10. The mass spectrometry system of claim 3, further comprising an RF multipole located between the first TIMS analyzer and the second TIMS analyzer.

11. The mass spectrometry system according to claim 10, wherein: The RF multipole is located between the ion gate and the second TIMS analyser.

12. The mass spectrometry system according to claim 10, wherein: The RF multipole is one of an RF quadrupole, an RF hexapole, an RF octupole and an RF ion tunnel.

13. The mass spectrometry system according to claim 10, wherein: The RF multipole operates as one of a mass filter, a mobility mass filter, an ion guide, a fragmentation cell, an activation cell, and an ion trap.

14. The mass spectrometry system according to claim 3, wherein: The first TIMS analyzer and the second TIMS analyzer are arranged in line.

15. The mass spectrometry system according to claim 3, wherein: The first TIMS analyzer and the second TIMS analyzer are arranged non-collinearly.

16. The mass spectrometry system according to claim 15, wherein: The angle between the axis of the first TIMS analyser and the axis of the second TIMS analyser is greater than 10°.

17. The mass spectrometry system according to claim 15, wherein: The angle between the axis of the first TIMS analyser and the axis of the second TIMS analyser is greater than 45°.

18. The mass spectrometry system of claim 15, wherein: The angle between the axis of the first TIMS analyser and the axis of the second TIMS analyser is 90°.

19. The mass spectrometry system of claim 15, wherein: The first TIMS analyser and / or the second TIMS analyser comprises an RF funnel at an inlet.

20. The mass spectrometry system of claim 3, wherein: The first TIMS analyser and / or the second TIMS analyser comprises an accumulation region for trapping and a mobility separation region for separating ions according to mobility.

21. The mass spectrometry system of claim 1, wherein: The mass analyzer is one of time of flight with orthogonal ion injection, electrostatic ion trap, RF ion trap, ion cyclotron frequency ion trap, and quadrupole mass filter.

22. The mass spectrometry system of claim 1, further comprising a mass filter and / or a fragmentation cell between the first TIMS analyzer and the mass analyzer.

23. A method for analyzing ions, comprising the steps of: providing ions from the ion source to a first TIMS analyzer where the ions are radially confined by an RF electric field; separating the ions according to mobility in the first TIMS analyzer at an elevated pressure above 500 Pa; Select at least one ion species of interest; delivering the selected ions of interest to a trapping region of a second TIMS analyzer; separating the selected ions of interest according to mobility in the second TIMS analyzer, wherein a repetition rate of the separation in the first TIMS analyzer is at least 2 times higher than a repetition rate of the separation in the second TIMS analyzer; as well as The separated ions are analyzed by mass spectrometry or tandem mass spectrometry.

24. The method according to claim 23, wherein: The elevated pressure is equal to or higher than 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa or 10000 Pa.

25. The method according to claim 23, wherein: The step of selecting at least one ion species of interest comprises, for ions within at least one limited mobility range, reducing the transmission of ions to the second TIMS analyser such that unwanted ion species are eliminated or at least significantly reduced.

26. The method according to claim 25, wherein: The transmission of a high abundance ion species of interest is lower than the transmission of a lower abundance ion species of interest.

27. The method according to claim 23, wherein: The at least one ion species of interest is from one finite mobility range or from different disjoint mobility ranges.

28. The method of claim 23, wherein: The selected ions of interest are separated in the second TIMS analyzer at an elevated pressure equal to or greater than 500 Pa, 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa or 10000 Pa.

29. The method of claim 23, wherein: Selected ions of interest are isolated in the second TIMS analyzer at pressures below 500 Pa.

30. The method of claim 23, wherein: Selected ions of interest were isolated in the second TIMS analyzer at a pressure between 100 Pa and 300 Pa.

31. The method of claim 23, wherein: The steps of separating and selecting in the first TIMS analyzer are repeated, and the transferred ions of interest are accumulated in the trapping region of the second TIMS analyzer before the transferred ions of interest are separated in the second TIMS analyzer.

32. The method according to claim 31, wherein: Selected ions of interest are isolated in the second TIMS analyzer at pressures below 500 Pa.

33. The method according to claim 31, wherein: Selected ions of interest were isolated in the second TIMS analyzer at a pressure between 100 Pa and 300 Pa.

34. The method of claim 32, wherein: The repetition rate of the separation in the first TIMS analyser is 5, 10, 20 or 50 times higher than the repetition rate of the separation in the second TIMS analyser.

35. The method of claim 34, wherein: The average mobility resolution of the first TIMS analyzer is equal to or higher than the average mobility resolution of the second TIMS analyzer.

36. The method of claim 23, wherein: Prior to trapping the selected ions of interest in the trapping region of the second TIMS analyzer, the selected ions of interest are filtered based on their mass or based on a combination of their mass and mobility.

37. A method for analyzing ions, comprising the steps of: providing ions from the ion source to a first TIMS analyzer where the ions are radially confined by an RF electric field; separating the ions according to mobility in the first TIMS analyzer at an elevated pressure above 500 Pa; Select an ion species of interest from a limited range of mobilities; fragmentation or activation of selected ions of interest; delivering the fragment ions or activated ions to a trapping region of a second TIMS analyzer; separating the fragment ions or activated ions according to mobility in the second TIMS analyzer, wherein a repetition rate of the separation in the first TIMS analyzer is at least 2 times higher than a repetition rate of the separation in the second TIMS analyzer; as well as The separated ions are analyzed by mass spectrometry or tandem mass spectrometry.

38. The method of claim 37, wherein: The elevated pressure is equal to or higher than 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa or 10000 Pa.

39. The method of claim 37, wherein: The selected ions of interest are separated in the second TIMS analyzer at an elevated pressure equal to or greater than 500 Pa, 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa or 10000 Pa.

40. The method of claim 37, wherein: Selected ions of interest are isolated in the second TIMS analyzer at pressures below 500 Pa.

41. The method of claim 37, wherein: Selected ions of interest were isolated in the second TIMS analyzer at a pressure between 100 Pa and 300 Pa.

42. The method of claim 37, wherein: The steps of separation, selection and fragmentation or activation in the first TIMS analyser are repeated and the transferred fragment ions or activated ions are accumulated in the trapping region of the second TIMS analyser before being separated in the second TIMS analyser.

43. The method of claim 42, wherein: The repetition rate of the separation in the first TIMS analyser is 5, 10, 20 or 50 times higher than the repetition rate of the separation in the second TIMS analyser.

44. The method of claim 43, wherein: The average mobility resolution of the first TIMS analyzer is equal to or higher than the average mobility resolution of the second TIMS analyzer.

45. The method of claim 37, wherein: Prior to trapping the selected ions of interest in the trapping region of the second TIMS analyser, the selected ions of interest are filtered according to their mass or according to a combination of their mass and mobility.

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