Mass spectrometry system with ion mobility analyzer at elevated pressure

Abstract

A hybrid mass spectrometry system and a method of operating the hybrid mass spectrometry system are provided, the system including an ion source, a first trapped ion mobility spectrometry (TIMS) analyzer and a mass analyzer, where the TIMS analyzer is located in and operates in a first vacuum chamber at an elevated pressure above 500 Pa.

Description

[0001] This application is a divisional application of the Chinese patent application with the application date of May 29, 2020, application number

[0002] 2020104762048, and the invention creation name of "Mass spectrometry system with an ion mobility analyzer under elevated pressure". Technical Field

[0003] The present invention relates to a hybrid mass spectrometry system in which trapped ion mobility spectrometry (TIMS) is coupled with mass spectrometry (MS), particularly tandem mass spectrometry (tandem MS), and a method of operating the hybrid mass spectrometry system. Background Art

[0004] Ion mobility spectrometry (IMS) is an analytical technique that is used to study the mobility of ions in a buffer gas and separate them according to their mobility.

[0005] 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, such that it is generally possible to resolve isomers or conformers that cannot be resolved by mass spectrometry. Many applications also utilize the ability to determine the cross-section of analyte ions from the measured mobility of the analyte ions. Knowledge of the cross-section has proven important in many fields, including the identification of compound classes and detailed structures, particularly in the field of structural biology.

[0006] In trapped ion mobility spectrometry (TIMS), ions are first trapped by a counterflow gas stream along a non-uniform DC electric field (electric field gradient, EFG) or by a counterflow gas stream 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 their mobility, and subsequently, the trapped ions are eluted from the TIMS analyzer over time according to their mobility by adjusting either the gas velocity or the height of the axial DC electric field (U.S. Patent No. 6,630,662 B1 to Loboda; U.S. Patent No. 7,838,826 B1 to Park). The TIMS analyzer operates in a low-pressure range of 2 to 500 Pa and uses an RF electric field to radially confine the 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).

[0007] U.S. Patent No. 9,683,964 (Park et al.) teaches a TIMS analyzer that includes a capture region and a separation region for parallel accumulation. The TIMS analyzer accumulates ions in the capture region and analyzes the pre-accumulated ions in parallel in time in the separation region. An air flow drives the ions against the slope of a reaction DC electric field barrier in the capture region such that the ions are axially captured and separated according to their mobility at their positions along the slope. During the accumulation of ions in the capture region, the air flow also drives the ions that have been accumulated in a previous accumulation and transferred to the separation region against the slope of a reaction DC electric field barrier in the separation region such that the ions are axially captured and spatially separated according to their mobility. After loading the separation region with the accumulated ions to be analyzed, the height of the reaction DC electric field barrier is steadily decreased such that ion species are released from the separation region in order of their mobility.

[0008] Published U.S. Patent Application 2017 / 0350860 (Raether et al.) teaches that the radial confinement RF electric field of a TIMS analyzer can be at least partially a hexapole, octupole, or higher order RF electric field.

[0009] U.S. Patent No. 10,241,079 (Park et al.) teaches a system that includes two TIMS analyzers with an ion gate therebetween. The ion gate is used to select one or more ion species after separation in an upstream TIMS analyzer for selective transfer to a downstream TIMS analyzer. A transient electric potential is applied to the electrodes of the ion gate such that the transmission of ions in at least one limited mobility range is reduced, preferably such that unwanted ions are eliminated or at least substantially reduced, and such that the transmission of a highly abundant ion species of interest is lower than the transmission of a less abundant ion species of interest.

[0010] There is still a need for a hybrid mass spectrometry system having one or more TIMS analyzers that can handle a higher ion current from an ion source in order to reduce the detection limit for low-abundance ion species. SUMMARY OF THE INVENTION

[0011] In a first aspect, the present invention provides a mass spectrometry system that includes an ion source, a first trapped ion mobility spectrometry (TIMS) analyzer, and a mass analyzer, wherein the TIMS analyzer is located in and operates in a first vacuum chamber at an elevated pressure above 500 Pa. The elevated pressure can be equal to or higher than 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa, or 10000 Pa.

[0012] The TIMS analyzer can include a DC electric field gradient (ramp) and a counterflow gas stream that drives ions against the DC electric field gradient such that the ions are axially trapped in the RF ion guide. The direction of the gas stream can be directed upstream towards the ion source or downstream away from the ion source. Most preferably, the DC electric field gradient is the rising edge of a DC electric field barrier having a vertex or a flat segment, and the counterflow gas stream drives the ions away from the ion source against the barrier. The TIMS analyzer can also include a gas stream having a velocity gradient and a counteracting (constant) DC electric field. Ions are radially confined by an RF electric field. The trapped ions are axially released from the ion guide according to their mobility by adjusting the DC electric field and / or the gas stream.

[0013] The mass spectrometry system further includes a second TIMS analyzer, wherein the second TIMS analyzer is located downstream of the first TIMS analyzer. The second TIMS analyzer can 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 can also be equal to or higher than the pressure in the first vacuum chamber.

[0014] The mass spectrometry system can 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 such that the transmission of ions in at least one limited mobility range is reduced, preferably such that unwanted ion species are eliminated or at least substantially reduced, and such that the transmission of the highly abundant ion species of interest is lower than the transmission of the less abundant ion species of interest.

[0015] At least one or both of the TIMS analyzers preferably include an accumulation zone for trapping and a mobility separation zone. A TIMS analyzer (separator) with parallel accumulation is disclosed in U.S. Patent No. 9,683,964 (Park et al.).

[0016] The first TIMS analyzer can be arranged collinearly with the second TIMS analyzer. More preferably, the first TIMS analyzer and the second TIMS analyzer are arranged non-collinearly. Non-collinear arrangement means that the angle between the axis of the first TIMS analyzer and the axis of the second TIMS analyzer is substantially non-zero. The angle between the axis of the first TIMS analyzer and the axis of the second TIMS analyzer is greater than 10°, preferably greater than 45°, more preferably greater than 75°, especially substantially 90° (orthogonal arrangement). The angle between the axis of the first TIMS analyzer and the axis of the second TIMS analyzer can be greater than 90°, for example greater than 90° and less than 120°. The first and / or second TIMS analyzer may include an RF funnel at the inlet. In the non-collinear case, the second TIMS analyzer preferably includes an RF funnel at its inlet.

[0017] The mass spectrometry system may further include an RF multipole located between the first and second TIMS analyzers. The RF multipole can be arranged collinearly with the first TIMS analyzer or inclined at an angle, for example less than 20°, with respect to the first TIMS analyzer. The RF multipole is most preferably linear (two-dimensional) and can be straight or curved. The RF multipole is preferably located between the ion gate and the second TIMS analyzer and can be, for example, one of an RF quadrupole, an RF hexapole, an RF octapole, and an RF ion tunnel. The RF multipole can 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 can be entirely located in the first or second vacuum chamber or can transition from the first vacuum chamber to the second vacuum chamber. The RF multipole can also be located in an additional vacuum chamber that is located between the first and second vacuum chambers and is separated from these vacuum chambers by a differential pumping stage, where the pressure in the additional vacuum chamber is preferably lower than the pressure in the first and second vacuum chambers.

[0018] The mass spectrometry system can include more than one ion source. One of the ion sources can be an atmospheric pressure ion source that is coupled to the first vacuum chamber by one of a single transfer capillary, multiple transfer capillaries, a porous transfer capillary, a single hole, and multiple holes. One of the ion sources can be a sub-atmospheric pressure ion source that can be located, for example, upstream of the first TIMS analyzer or between the first TIMS analyzer and the second TIMS analyzer. Ions can be generated using one of spray ionization (such as electrospray (ESI) or thermospray), desorption ionization (such as matrix-assisted laser / desorption ionization (MALDI) or secondary ionization), chemical ionization (CI), photoionization (PI), electron impact ionization (EI), and gas discharge ionization.

[0019] The mass analyzer is one of a time-of-flight analyzer (especially 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 spectrometry system may further include a mass filter and / or a fragmentation cell between the ion mobility analyzer and the mass analyzer. Ions can be fragmented by one of collision-induced dissociation (CID), surface-induced dissociation (SID), photodissociation (PD), electron capture dissociation (ECD), electron transfer dissociation (ETD), post electron transfer dissociation collision activation (ETcD), activation simultaneous with electron transfer dissociation (AI-ETD), and fragmentation by reaction with highly excited or radical neutral particles. Photodissociation preferably includes infrared multiphoton dissociation (IRMPD) or ultraviolet photodissociation (UVPD). For example, selected ions can be activated by multiphoton absorption or by collision-induced activation in a dipole or rotational AC electric field.

[0020] 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 above 500 Pa; selecting at least one ion species of interest; transferring the selected ion species of interest to a capture region of a second TIMS analyzer; separating the selected ion species of interest according to mobility in the second TIMS analyzer; 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 ion species of interest transferred to the second TIMS analyzer. The elevated pressure can be equal to or higher than 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa, or 10000 Pa.

[0021] The step of selecting at least one ion species of interest preferably includes: for ions within at least one limited mobility range, reducing the transfer 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 transfer of highly abundant ion species of interest is lower than the transfer of less abundant ion species of interest. For example, the selected ions can be from a single limited mobility range or from multiple non-overlapping mobility ranges.

[0022] Preferably, in the second TIMS analyzer, the selected ions of interest are separated at a pressure below 500 Pa, preferably between 100 Pa and 300 Pa. However, the selected ions of interest can also be separated in the second TIMS analyzer at elevated pressures equal to or higher than 500 Pa, 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa or 10000 Pa.

[0023] Preferably, the separation step and the selection step in the first TIMS analyzer are repeated, and the transmitted ions of interest are accumulated in the capture region of the second TIMS analyzer before being separated in the second TIMS analyzer. More preferably, in the second TIMS analyzer, the selected ions of interest are separated at a pressure below 500 Pa, preferably between 100 Pa and 300 Pa, and the separation repetition rate in the first TIMS analyzer can be 2, 5, 10, 20 or 50 times that of the separation repetition rate in the second TIMS analyzer. Due to operating 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, although the repetition rate is much higher and the ion throughput is also much higher. Alternatively, at the same repetition rate, the average mobility resolution of the first TIMS analyzer can be higher than that of the second TIM analyzer. In the case where both TIMS analyzers are operated at elevated pressures, the first TIMS analyzer can operate at a higher repetition rate (e.g., greater than 2, 5, 10, 20 or 50 times) and lower resolution, while the selected ions with reduced charge are analyzed in the second TIMS analyzer, which operates at a lower repetition rate and higher mobility resolution, especially at a mobility resolution equal to or greater than 500.

[0024] Before being captured in the capture region of the second TIMS analyzer, the selected ions of interest can be further filtered according to their mass or a combination of their mass and mobility.

[0025] 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 above 500 Pa; selecting an ion species of interest from a limited mobility range; fragmenting or activating the selected ion species of interest; transferring the fragment ions or activated ions to the 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 higher than 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa or 10000 Pa.

[0026] Preferably, in the second TIMS analyzer, the selected ion species of interest is separated at a pressure below 500 Pa, preferably between 100 Pa and 300 Pa. However, the selected ion species of interest may also be separated in the second TIMS analyzer at an elevated pressure equal to or higher than 500 Pa, 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa or 10000 Pa.

[0027] 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.

[0028] Before capturing the selected ion species of interest in the capture region of the second TIMS analyzer, the selected ion species of interest may be further filtered according to their mass or a combination of their mass and mobility.

[0029] 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 separation in the first TIMS analyzer to increase the selectivity of the selection step because the scan rate of the first TIMS analyzer is instantaneously reduced for the ion species of interest. The mobility resolution of the first TIMS analyzer for the ion species of interest is increased compared to the average mobility resolution of the first TIMS analyzer.

[0030] Surprisingly, the TIMS analyzer according to the present invention can handle a higher ion current from the ion source because, according to common sense, operation at elevated pressure reduces the RF pseudopotential that is necessary to confine ions along the axis of the TIMS analyzer without loss due to discharge. Reducing the RF pseudopotential results in a reduced charge capacity, i.e., fewer ions can be trapped in the TIMS analyzer and a reduced ion current can be handled. The idea of the present invention is that the effect of elevated pressure on the RF pseudopotential is compensated for, and even overcompensated for, for the following reasons:

[0031] First, the elevated 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 generating an arc, thereby strengthening the RF pseudopotential.

[0032] Second, the elevated pressure also shifts the stable region of ion motion such that a higher RF voltage can be applied to the electrodes of the TIMS analyzer without obtaining unstable ion trajectories.

[0033] Third, the mobility resolution of the TIMS analyzer scales approximately with K -3 / 4 and thus scales with p 3 / 4 , where K is the mobility of the ion and p is the pressure. The average mobility resolution scales approximately with (f TIMS ) -1 / 4 where f TIMSis the separation repetition rate, i.e., the TIMS analyzer at elevated pressure can operate at a higher repetition rate without sacrificing the mobility resolution and thus the selectivity in the selection step. A higher repetition rate is advantageous as it reduces the charge accumulation in the TIMS analyzer, i.e., the amount of charge per analysis. Additionally, selecting the ion species of interest results in a smaller ion current being transferred to the downstream TIMS analyzer compared to the ion current entering the first TIMS analyzer, i.e., reducing the amount of charge in the second TIMS analyzer. The selection step preferably includes substantially eliminating the ion species not of interest and reducing the ion species of interest with high abundance compared to the ion species of interest with low abundance.

[0034] Compared to operation at lower pressure, operation of the TIMS analyzer at elevated pressure enables the selection of ion species of interest at an increased repetition rate without reducing selectivity. In summary, the TIMS analyzer can be used to analyze a much higher ion current from the ion source at elevated pressure, which results in a lower detection limit. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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).

[0036] Figure 1B The ion source (101) having an RF funnel and a first TIMS analyzer, the ion gate (10), and the second TIMS analyzer (102) of the mass spectrometry system (100) are shown in more detail.

[0037] 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).

[0038] Figure 2B The ion source (201) having an RF funnel and a first TIMS analyzer, the ion gate (10), the RF quadrupole (11a), the laser system (12), and the second TIMS analyzer (202) of the mass spectrometry system (200) are shown in more detail.

[0039] 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).

[0040] Figure 3B The ion source (301) having a first TIMS analyzer, the ion gate (10), and the second TIMS analyzer (302) of the mass spectrometry system (300) are shown in more detail.

[0041] 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).

[0042] Figure 4B The ion source (401) having two TIMS analyzers of the mass spectrometry system (400) is shown in more detail. Detailed Description

[0043] Although the present invention has been shown and described with reference to several different embodiments of the present invention, those skilled in the art will recognize that combinations of embodiments and changes in form and detail can be made herein without departing from the scope of the present invention as defined by the appended claims. The present invention can be better understood by reference to the following drawings. The elements in the drawings are not necessarily to scale, and the emphasis is on illustrating the principles of the present invention (usually schematically). In different figures, the same or functionally equivalent elements are labeled with the same reference numerals.

[0044] 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) 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). The mass analyzer (105) is preferably a time-of-flight analyzer with orthogonal ion injection (OTOF-MS).

[0045] Figure 1B The ion source (101) having an RF funnel and a first TIMS analyzer, the ion gate (10), and the second TIMS analyzer (102) are shown in more detail.

[0046] The ion source (101) includes two chambers (1a, 1b).

[0047] 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 an ejection DC potential applied to the deflector electrode

[0048] (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.

[0049] 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 aperture of the deflector electrode (6a). Ions from the spray plume (4b) are introduced directly into the inlet of the RF funnel (7a).

[0050] The electrospray ion sources (3a, 4a) and (3b, 4b) can be operated simultaneously or separately from each other. A separation device (not shown) such as a liquid chromatography device or an electrophoresis device can be coupled to the spray emitters (3a, 3b).

[0051] The RF funnel (7a) is an octopole RF funnel known from the published US patent application 2004 / 0195503 (Park et al.). It is constructed as a stack of segmented perforated electrodes. Each perforated electrode includes eight segments. The apertures of the electrodes taper to a smaller diameter, thereby forming a funnel-shaped internal volume. Two phases of an RF voltage are alternately applied to adjacent segments of each individual electrode and adjacent segments of adjacent electrodes. The resulting RF pseudopotential keeps the ions away from the inner wall of the RF funnel (7a).

[0052] The ions are driven by an air stream (8a) into the first TIMS analyzer, which includes a capture region (9a) and a separation region (9b). The air stream (8a) is generated by pumping gas out of the vacuum chamber (1b) at the exit of the separation region (9b). The 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 that transitions to a segmented RF quadrupole. The separation region (9b) is constructed similarly to the capture region (9a), where the upstream segmented RF octopole transitions to the downstream segmented RF quadrupole. The octopole portion has a larger charge capacity per unit volume compared to the quadrupole portion.

[0053] The first TIMS analyzer preferably operates in a parallel accumulation mode, i.e., the first TIMS analyzer accumulates ions in the capture region (9a), while the pre-accumulated ions are analyzed in parallel in time in the separation region (9b). The gas flow (8a) drives the ions leaving the RF funnel (7a) against the ramp of the reaction DC electric field barrier in the capture region (9a), such that the ions are axially captured and separated according to their mobilities at their positions along the ramp. During the accumulation of ions in the capture region (9a), the gas flow (8a) also drives the ions that have been accumulated in a previous accumulation and transferred to the separation region (9b) against the ramp of the reaction DC electric field barrier in the separation region (9b), such that the ions are axially captured and spatially separated according to their mobilities. After loading the separation region (9b) with the ions to be analyzed, the height of the reaction DC electric field barrier is steadily decreased, such that the ion species are released from the separation region (9b) in the order of their mobilities. The velocity of the gas flow (8a) is on the order of about 100 m / s, and the operating pressure of the first TIMS analyzer is substantially 2000 Pa.

[0054] The second TIMS analyzer (102) includes 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 orthogonally arranged, i.e., 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°.

[0055] 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 about 200 Pa. The ions introduced into the vacuum chamber (1c) are deflected into the quadrupole RF funnel (7b) by an applied repulsive DC potential to the deflector electrode (6b), and then guided by the gas flow (8b) towards the exit of the quadrupole RF funnel (7b) into the capture region (9c). The gas flow (8b) is generated by pumping gas out of the vacuum chamber (1c) at the exit of the separation region (9d). The velocity of the gas flow (8b) is on the order of about 100 m / s, and the operating pressure of the second TIMS analyzer (102) is substantially 200 Pa.

[0056] Similar to the first TIMS analyzer (9a, 9b), the second TIMS analyzer (102) preferably operates in the parallel accumulation mode as described above, i.e., ions are accumulated in the capture region (9c), while the pre-accumulated ions are analyzed in parallel in the separation region (9d).

[0057] By pumping ports (5a - 5c) and through the exit of the separation region (9d) adjacent to the vacuum chamber of the mass filter (103) ( Figure 1B not shown in) the gas is pumped out of the ion source (101) and the second TIMS analyzer (102).

[0058] The ion gate (10) is an ion monopole lens. Other embodiments may include a Tyndall gate or a Bradbury-Nielsen gate operated with a DC voltage, where positive and negative DC potentials are alternately supplied to the wires of the gate. Alternatively, the Bradbury-Nielsen gate can be operated with an RF potential, thereby forming a reflecting pseudopotential around the wires. This RF Bradbury-Nielsen gate presents the following additional advantages: reflecting high-mobility ions while transmitting low-mobility ions, and the transmission limit depends on the RF frequency and the voltage on the wires (gate control voltage).

[0059] The first TIMS analyzers (9a, 9b) and the second TIMS analyzers (9c, 9d) can be operated in a selective transfer mode as described in U.S. Patent No. 10,241,079 (Park et al.), including the steps of:

[0060] Supplying ions from an atmospheric pressure ESI ion source (3a, 4a) and / or from a sub-atmospheric ESI ion source (3c, 4c) to the first TIMS analyzers (9a, 9b);

[0061] Separating ions according to mobility in the first TIMS analyzers (9a, 9b) at an elevated pressure of 2000 Pa;

[0062] Applying a transient DC potential to the electrodes of the ion gate (10) to adjust the transmission of the ion gate (10) and select the ion species of interest;

[0063] Transferring the selected ions to the capture region (9c) of the second TIMS analyzer (102);

[0064] Separating the selected ions according to mobility in the second TIMS analyzer (102); and

[0065] Analyzing the separated ions by mass spectrometry or tandem mass spectrometry using a downstream mass analyzer (105) and optionally using a downstream mass filter (103) and a fragmentation cell (104).

[0066] Preferably, the ion gate (10) is operated by adjusting its transmission such that the transmission of ions in at least one limited mobility range is reduced. Preferably, the ion gate (10) is operated such that unwanted ion species are eliminated or at least substantially reduced, and the transmission of the highly abundant ion species of interest is lower than the transmission of the less abundant ion species of interest.

[0067] Preferably, the separation step and the selection step in the first TIMS analyzers (9a, 9b) are repeated, and the ions to be transferred are accumulated in the capture region (9c) of the second TIMS analyzer (102) before being transferred to the separation region (9d) and separated therein.

[0068] The first TIMS analyzers (9a, 9b) and the second TIMS analyzers (9c, 9d) can also be operated in a tandem IMS mode, including the following steps:

[0069] Providing ions from an atmospheric pressure ESI ion source (3a, 4a) and / or from a sub-atmospheric ESI ion source (3c, 4c) to the first TIMS analyzers (9a, 9b);

[0070] Separating the ions according to mobility in the first TIMS analyzers (9a, 9b) at an elevated pressure of 2000 Pa;

[0071] Applying a transient DC potential to the electrodes of the ion gate (10) to adjust the transmission of the ion gate (10) and select an ion species of interest;

[0072] Fragmenting the selected ions by accelerating the selected ions into the vacuum chamber (1c) using the DC potential applied to the electrodes of the ion gate (10);

[0073] Transferring these fragment ions to the capture region (9c) of the second TIMS analyzer (102);

[0074] Separating the fragment ions according to mobility in the second TIMS analyzer (102); and analyzing the separated fragment ions by mass spectrometry or tandem mass spectrometry using a downstream mass analyzer (105) and optionally using a downstream mass filter (103) and a fragmentation cell (104).

[0075] Preferably, 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, the steps of separation, selection, fragmentation or activation, and transfer of the fragmented or activated ions in the first TIMS analyzers (9a, 9b) are repeated multiple times.

[0076] When the average mobility resolution R is between about 75 and 40, the repetition rate of separation in the second TIMS analyzers (9c, 9d) is preferably between 10 Hz and 100 Hz, respectively. The first TIMS analyzers (9a, 9b) operate at a pressure 10 times higher than the operating pressure of the second TIMS analyzers (9c, 9d), and can operate, for example, at a repetition rate 5 times higher than the repetition rate of the second TIMS analyzers (9c, 9d), such that the mobility resolution of the first TIMS analyzers is still about 3.8 times higher ( = 10 3 / 4 ·5 -1 / 4 ). Operation at elevated pressure results in better selectivity and ion throughput.

[0077] Figure 2A FIG. shows a schematic diagram of a second example of a mass spectrometry system according to the present invention. The mass spectrometry system (200) 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). The mass analyzer (205) is preferably a time-of-flight analyzer with orthogonal ion injection (OTOF-MS).

[0078] Figure 2B More detailed illustration of the ion source (201) having an RF funnel and a first TIMS analyzer, the ion gate (10), the RF quadrupole (11a), the laser system (12), and the TIMS analyzer (202).

[0079] The mass spectrometry system (200) differs from the mass spectrometry system (100) in that:

[0080] The ion gate (10) is located in the first vacuum chamber (1b);

[0081] The RF quadrupole (11a) bridges the vacuum chambers (1b) and (1c);

[0082] An additional sub-environment MALDI source is located in the vacuum chamber (1c); and

[0083] The laser system (12) for generating photons and introducing the photons into the RF quadrupole (11a).

[0084] As in the mass spectrometry system (100), the ion gate (10) can operate in a selective transmission mode or a tandem IMS mode. In selective transmission, 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 zone (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) such that a selected ion species 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).

[0085] The RF quadrupole (11a) can operate 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. By applying an appropriate DC potential to the exit electrode (11b), ions introduced from the first TIMS analyzer (9a, 9b) can be trapped within the RF quadrupole (11a).

[0086] The MALDI source includes a MALDI plate (3c), a MALDI plume (4c), and a MALDI laser (3e). Ions introduced into the vacuum chamber (1c) through the RF quadrupole (11a) are deflected to the entrance of the RF funnel (7b) by an extraction DC potential applied to the MALDI plate (3c) or a replacement electrode (not shown). Ions from the MALDI plume (4c) are introduced directly into the entrance of the RF funnel (7b).

[0087] The laser system (13) can generate photons in at least one of the vacuum ultraviolet range (VUV), ultraviolet range (UV), and 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 fundamental wavelength of the Nd:YAG laser system at 1064 nm or the pump light generated by a laser light-emitting diode can be used for IRMPD or IRMPA, the third harmonic at 355 nm can be used as the light source for the MALDI source (3c, 4c) of the sub-environment, and the fourth harmonic at 266 nm can be used for UVPD and optionally for post-ionization of the MALDI process.

[0088] For example, it is necessary to trap ions within the RF quadrupole (11a) in cases where photo-induced activation or fragmentation is not fast enough to induce fragmentation or activation during the time required for the ions to pass through the RF quadrupole (11a) (i.e., without trapping). The time required to induce fragmentation depends on the absorption cross-section of the ions and the photon density in the RF quadrupole (11a).

[0089] The mass spectrometry system (200) is capable of implementing multiple operating modes for hybrid IMS / MS analysis:

[0090] MS (without IMS separation)

[0091] Tandem MS (without IMS separation)

[0092] IMS separation / (tandem) MS

[0093] IMS separation with selection / IMS separation / (tandem) MS

[0094] IMS separation with selection / mass mobility filtering / (tandem) MS

[0095] Tandem IMS / (tandem) MS with fragmentation by CID or PD

[0096] Tandem IMS with fragmentation by CID or PD and mass mobility filtering / (tandem) MS

[0097] Figure 3A A schematic diagram showing a third example of a mass spectrometry system according to the present invention is presented. The mass spectrometry system (300) 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). The mass analyzer (305) is preferably a time-of-flight analyzer with orthogonal ion injection (OTOF-MS).

[0098] Figure 3B The ion source (301) having a first TIMS analyzer, the ion gate (10), and the second TIMS analyzer (302) are shown in more detail.

[0099] The ion source (301) includes two chambers (1a, 1b).

[0100] 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 an ejection 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 more and a length of 180 mm or less.

[0101] The vacuum chamber (1b) is maintained at an elevated pressure of about 3000 Pa and includes a sub-atmospheric electrospray source (spray emitter (3b), spray plume (4b)). The spray emitter (3b) is positioned in the aperture of the deflector electrode (6a). Ions from the spray plume (4b) are introduced directly into the inlet of the RF funnel (7a).

[0102] The electrospray ion sources (3a, 4a) and (3b, 4b) can be operated simultaneously or separately from each other. A separation device (not shown), such as a liquid chromatography device or an electrophoresis device, can be coupled to the spray emitters (3a, 3b).

[0103] The RF funnel (7a) is an octopole RF funnel known from the published US patent application 2004 / 0195503 (Park et al.). It is constructed as a stack of segmented perforated electrodes. Each perforated electrode includes eight segments. The holes of the electrodes taper to a smaller diameter, thereby forming an inner volume in the shape of a funnel. Two phases of an RF voltage are alternately applied to adjacent segments of each individual electrode and adjacent segments of adjacent electrodes. The resulting RF pseudopotential keeps the ions away from the inner wall of the RF funnel (7a).

[0104] The ions are driven by an air flow (8a) into the first TIMS analyzer, which includes a capture region (9a) and a separation region (9b). The air flow (8a) is generated by pumping gas out of the vacuum chamber (1b) at the exit of the separation region (9b). The 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), where the upstream segmented RF octopole transitions to the downstream segmented RF quadrupole. The octopole portion has a larger unit volume space capacity compared to the quadrupole portion.

[0105] The first TIMS analyzer preferably operates 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 in the capture region (9a), such that the ions are axially captured and separated according to their mobility at their positions 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 a previous accumulation and transferred to the separation region (9b) against the slope of the reaction DC electric field barrier in the separation region (9b), such that the ions are axially captured and spatially separated according to their mobility. After loading the separation region (9b) with the ions to be analyzed, the height of the reaction DC electric field barrier is steadily decreased, such 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 on the order of about 100 m / s, and the operating pressure of the first TIMS analyzer is substantially 3000 Pa.

[0106] The second TIMS analyzer (302) includes a capture region (9c) and a separation region (9d). Ions are introduced directly from the outlet of the separation region (9b) of the first TIMS analyzer into the capture region (9c) of the second TIMS analyzer (302). The first TIMS analyzer (9a, 9b) and the second TIMS analyzer (9c, 9d) are arranged collinearly, i.e., 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) preferably operates in a parallel accumulation mode as described above, i.e., ions are accumulated in the capture region (9c), while pre-accumulated ions are analyzed in parallel in the separation region (9d).

[0107] 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 about 150 Pa. A gas flow (8b) is generated by pumping gas out of the vacuum chamber (1c) at the outlet of the separation region (9d). The velocity of the gas flow (8b) is on the order of about 100 m / s.

[0108] The ion gate (10) is an ion single 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) can operate in a selective transfer mode as described in U.S. Patent No. 10,241,079 (Park et al.), including the steps of:

[0109] Ions from an atmospheric pressure ESI ion source (3a, 4a) and / or from a sub-atmospheric ESI ion source (3c, 4c) are provided to a first TIMS analyzer (9a, 9b);

[0110] At an elevated pressure of 3000 Pa, the ions are separated according to mobility in the first TIMS analyzer (9a, 9b);

[0111] A transient DC potential is applied to the electrodes of the ion gate (10) to adjust the transmission of the ion gate (10) and to select an ion species of interest;

[0112] These selected ions are transferred to the capture region (9c) of a second TIMS analyzer (302);

[0113] The selected ions are separated according to mobility in the second TIMS analyzer (302); and

[0114] The separated ions are analyzed by mass spectrometry or tandem mass spectrometry using a downstream mass analyzer (305) and optionally using a downstream mass filter (303) and fragmentation cell (304).

[0115] Preferably, the ion gate (10) is operated by adjusting the transmission of the ion gate such that the transmission of ions in at least one limited mobility range is reduced, preferably such that unwanted ion species are eliminated or at least substantially reduced, and such that the transmission of a highly abundant ion species of interest is lower than the transmission of a less abundant ion species of interest.

[0116] Preferably, before the resulting accumulated ions in the capture region (9c) of the second TIMS analyzer (302) are transferred to the separation region (9d) and separated therein, the steps of separating, selecting and transferring ions in the first TIMS analyzer (9a, 9b) are repeated a plurality of times.

[0117] The first TIMS analyzer (9a, 9b) and the second TIMS analyzer (9c, 9d) can also be operated in a tandem IMS mode, including the following steps:

[0118] Ions from an atmospheric pressure ESI ion source (3a, 4a) and / or from a sub-atmospheric ESI ion source (3c, 4c) are provided to a first TIMS analyzer (9a, 9b);

[0119] At an elevated pressure of 3000 Pa, the ions are separated according to mobility in the first TIMS analyzer (9a, 9b);

[0120] A transient DC potential is applied to the electrodes of the ion gate (10) to adjust the transmission of the ion gate (10) and to select an ion species of interest;

[0121] The selected ions are fragmented by accelerating them into the vacuum chamber (1c) using a DC potential applied to the electrodes of the ion gate (10).

[0122] These fragment ions are transferred to the capture region (9c) of the second TIMS analyzer (302).

[0123] In this second TIMS analyzer (302), these fragment ions are separated according to mobility; and

[0124] The separated fragment ions are analyzed by mass spectrometry or tandem mass spectrometry using a downstream mass analyzer (305) and optionally using a downstream mass filter (303) and fragmentation cell (304).

[0125] Preferably, the separation, selection, and fragmentation or activation steps in the first TIMS analyzer (9a, 9b) are repeated, and they are accumulated in the capture region (9c) of the second TIMS analyzer (302) before the transferred fragment ions or activated ions are transferred to the separation region (9d) and separated therein.

[0126] The separation repetition rate in the second TIMS analyzer (9c, 9d) can 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 can operate, for example, at a repetition rate 10 times higher than the repetition rate of the second TIMS analyzer (9c, 9d), such 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.

[0127] Figure 4A A schematic diagram showing a fourth example of a mass spectrometry system according to the present invention is shown. The mass spectrometry system (400) includes an ion source (401) having 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 with orthogonal ion injection (OTOF-MS).

[0128] Figure 4B An ion source (401) having two TIMS analyzers and an ion gate (10B) are shown.

[0129] The ion source (401) includes two chambers (1a, 1b). 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 an ejection DC potential applied to the deflector electrode (6a). The transfer capillary is preferably a short, large-diameter 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 includes a sub-atmospheric electrospray source (spray emitter (3b), spray plume (4b)). The spray emitter (3b) is positioned in the aperture of the deflector electrode (6a). Ions from the spray plume (4b) are introduced directly into the inlet of the RF funnel (7a). The electrospray ion sources (3a, 4a) and (3b, 4b) can be operated simultaneously or separately from each other. A separation device (not shown) such as a liquid chromatography device or an electrophoresis device can be coupled to the spray emitters (3a, 3b).

[0130] The RF funnel (7a) is a quadrupole RF funnel known from the published US patent application 2004 / 0195503 (Park et al.). It is constructed as a stack of segmented perforated electrodes. Each perforated electrode includes four segments. The apertures of the electrodes taper to a smaller diameter, thus forming an internal volume in the shape of a funnel. Two phases of the RF voltage are alternately applied to adjacent segments of each individual electrode and adjacent segments of adjacent electrodes. The resulting RF pseudopotential keeps the ions away from the inner wall of the RF funnel (7a).

[0131] 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 collinearly, i.e., the relative angle between the common axis of regions (9a, 9b) and the common axis of regions (9c) and (9d) is substantially zero.

[0132] Ions are driven by an air flow (8a) into the capture region (9a) of the first TIMS analyzer. The air flow (8a) is generated by pumping gas out of the vacuum chamber (1b) at the exit of the separation region (9d) of the second TIMS analyzer. 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 approximately 7 cm. The capture regions (9a, 9c) and the separation regions (9b, 9d) are constructed as segmented RF quadrupoles.

[0133] Both TIMS analyzers are preferably operated in parallel accumulation mode, i.e., the TIMS analyzer accumulates ions in the capture regions (9a, 9c), while analyzing the pre-accumulated ions in parallel in time in the separation regions (9b, 9d). The gas flow (8a) drives the ions against the ramp of the reaction DC electric field barrier in the capture regions (9a, 9c), such that the ions are axially captured and separated according to their mobility at their position along the ramp. During the accumulation of ions in the capture regions (9a, 9c), the gas flow (8a) also drives the ions that have been accumulated in a previous accumulation and transferred to the separation regions (9b, 9d) against the ramp of the reaction DC electric field barrier in the separation regions (9b, 9d), such that the ions are axially captured and spatially separated according to their mobility. After loading the separation regions (9b, 9d) with the ions to be analyzed, the height of the reaction DC electric field barrier is steadily reduced, such 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 on the order of 100 m / s, and the operating pressure of both TIMS analyzers is substantially 2000 Pa.

[0134] The ion gate (10b) is an ion single lens. It is located between the separation region (9b) and the capture region (9c) and is enclosed such that the gas flow (8a) can pass through both TIMS analyzers. The first TIMS analyzer (9a, 9b) and the second TIMS analyzer (9c, 9d) can be operated in selective transfer 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) such that the ion transmission in at least one finite mobility range is reduced, preferably such that unwanted ion species are eliminated or at least substantially reduced.

[0135] At an average mobility resolution R higher than 200, the separation repetition rate of both TIMS analyzers can be, for example, 100 Hz. Operation at elevated pressure results in high mobility resolution and ion throughput. At an average mobility resolution of about 170, the separation repetition rate of the first TIMS analyzer (9a, 9b) can be, for example, 200 Hz, while in the second TIMS analyzer (9c, 9d), ions selected from a limited mobility range with reduced charge amount 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 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 of 1000 Pa or higher than 1000 Pa and operates in the first vacuum chamber.

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

3. The mass spectrometry system according to claim 2, wherein, the second TIMS analyzer is located in the first vacuum chamber at the elevated pressure.

4. The mass spectrometry system according to claim 2, wherein, the second TIMS analyzer is located in a second vacuum chamber.

5. The mass spectrometry system according to claim 4, wherein, the pressure in the second vacuum chamber is higher than the pressure in the first vacuum chamber.

6. The mass spectrometry system according to claim 4, wherein, the pressure in the second vacuum chamber is lower than the pressure in the first vacuum chamber.

7. The mass spectrometry system according to claim 6, wherein, the pressure in the second vacuum chamber is lower than 500 Pa.

8. The mass spectrometry system according to claim 6, wherein, the pressure in the second vacuum chamber is between 100 Pa and 300 Pa.

9. The mass spectrometry system according to claim 2, further comprising an RF multipole located between the first TIMS analyzer and the second TIMS analyzer.

10. The mass spectrometry system according to claim 9, wherein, the RF multipole is located between the ion gate and the second TIMS analyzer.

11. The mass spectrometry system according to claim 9, wherein, the RF multipole is one of an RF quadrupole, an RF hexapole, an RF octopole, and an RF ion tunnel.

12. The mass spectrometry system according to claim 9, 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.

13. The mass spectrometry system according to claim 2, wherein, the first TIMS analyzer and the second TIMS analyzer are arranged collinearly.

14. The mass spectrometry system according to claim 2, wherein, the first TIMS analyzer and the second TIMS analyzer are arranged non - collinearly.

15. The mass spectrometry system according to claim 14, wherein, the angle between the axis of the first TIMS analyzer and the axis of the second TIMS analyzer is greater than 10°.

16. The mass spectrometry system according to claim 14, wherein, the angle between the axis of the first TIMS analyzer and the axis of the second TIMS analyzer is greater than 45°.

17. The mass spectrometry system according to claim 14, wherein, the angle between the axis of the first TIMS analyzer and the axis of the second TIMS analyzer is 90°.

18. The mass spectrometry system according to claim 14, wherein, The first TIMS analyzer and / or the second TIMS analyzer includes an RF funnel at the inlet.

19. The mass spectrometry system according to claim 2, wherein, the first TIMS analyzer and / or the second TIMS analyzer includes an accumulation region for capture and a mobility separation region for separating ions according to mobility.

20. The mass spectrometry system according to claim 1, wherein, the mass analyzer is one of a time-of-flight with orthogonal ion injection, an electrostatic ion trap, an RF ion trap, an ion cyclotron resonance ion trap, and a quadrupole mass filter.

21. The mass spectrometry system according to claim 1, further comprising a mass filter and / or a fragmentation cell between the TIMS analyzer and the mass analyzer.

22. 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 of 1000 Pa or higher than 1000 Pa; 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 according to mobility in the second TIMS analyzer; and analyzing the separated ions by mass spectrometry or tandem mass spectrometry.

23. The method according to claim 22, wherein, the step of selecting at least one ion species of interest includes reducing the transfer of ions to the second TIMS analyzer for ions within at least one limited mobility range, such that unwanted ion species are eliminated or at least significantly reduced.

24. The method according to claim 23, wherein, the transfer of highly abundant ion species of interest is lower than the transfer of less abundant ion species of interest.

25. The method according to claim 22, wherein, the at least one ion species of interest is from one limited mobility range or from different non-overlapping mobility ranges.

26. The method according to claim 22, wherein, separating the selected ions of interest in the second TIMS analyzer at an elevated pressure equal to or higher than 500 Pa, 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa, or 10000 Pa.

27. The method according to claim 22, wherein, separating the selected ions of interest in the second TIMS analyzer at a pressure lower than 500 Pa.

28. The method according to claim 22, wherein, separating the selected ions of interest in the second TIMS analyzer at a pressure between 100 Pa and 300 Pa.

29. The method according to claim 22, wherein, repeating the separation step and the selection step in the first TIMS analyzer, and accumulating the transferred ions of interest in the capture region of the second TIMS analyzer before separating the transferred ions of interest in the second TIMS analyzer.

30. The method according to claim 29, wherein, the selected ions of interest are separated in the second TIMS analyzer at a pressure below 500 Pa.

31. The method according to claim 29, wherein, the selected ions of interest are separated in the second TIMS analyzer at a pressure between 100 Pa and 300 Pa.

32. The method according to claim 30, wherein, the repetition rate of separation in the first TIMS analyzer is 2, 5, 10, 20 or 50 times higher than the repetition rate of separation in the second TIMS analyzer.

33. The method according to claim 32, 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.

34. The method according to claim 22, wherein, before capturing the selected ions of interest in the capture region of the second TIMS analyzer, the selected ions of interest are filtered according to the mass of the selected ions of interest or according to a combination of the mass and mobility of the selected ions of interest.

35. 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 of 1000 Pa or higher than 1000 Pa; selecting a species of ions of interest from a limited mobility range; fragmenting or activating the selected ions of interest; transferring the fragment ions or activated ions to the 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.

36. The method according to claim 35, wherein, the selected ions of interest are separated in the second TIMS analyzer at an elevated pressure equal to or higher than 500 Pa, 1000 Pa, 1500 Pa, 2000 Pa, 3000 Pa, 5000 Pa or 10000 Pa.

37. The method according to claim 35, wherein, the selected ions of interest are separated in the second TIMS analyzer at a pressure below 500 Pa.

38. The method according to claim 35, wherein, the selected ions of interest are separated in the second TIMS analyzer at a pressure between 100 Pa and 300 Pa.

39. The method according to claim 35, wherein, the steps of separation, selection and fragmentation or activation in the first TIMS analyzer are repeated, and before separating the transferred fragment ions or activated ions in the second TIMS analyzer, they are accumulated in the capture region of the second TIMS analyzer.

40. The method according to claim 39, wherein, the repetition rate of separation in the first TIMS analyzer is 2, 5, 10, 20 or 50 times higher than the repetition rate of separation in the second TIMS analyzer.

41. The method according to claim 40, 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.

42. The method according to claim 35, wherein, before the selected ions of interest are trapped in the trapping region of the second TIMS analyzer, the selected ions of interest are filtered according to the mass of the selected ions of interest or according to a combination of their mass and mobility.

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