Differential trapping ion mobility separator

Abstract

The invention relates to a trapped ion mobility separator, a mixed mass spectrometry system and a method for analyzing ions. The trapping ion mobility separator includes an ion channel in which ions move along an axis between a first end at which ions are introduced into the ion channel and a second end. Two axial forces acting on the ion are provided, the first axial force being caused by the alternating axial electric field and having an effect on ion movement associated with differential mobility, and the second axial force at least temporarily counteracting the first axial force. At least one of the two forces varies spatially and temporally such that ions are trapped along the axis at mobility-related locations and gradually driven to one end of the ion channel as a function of their differential mobility.

Description

Technical Field

[0001] The invention relates to a trapped ion mobility separator, a hybrid mass spectrometry system and a method for analyzing ions. Background Art

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

[0003] An inherent feature of ion mobility spectrometry is that the mobility of ions in a gas depends on the molecular geometry of the ions, thereby often being able 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 mobility or cross section has proven to be important in many areas, including identifying analytes (e.g., in proteomics and metabolomics), separating classes of compounds, and determining molecular structure (e.g., in structural biology).

[0004] In trapped ion mobility spectrometry, ions are typically trapped by a spatially non-uniform DC electric field (typically an electric field gradient) and a counteracting gas flow, or by a spatially uniform DC electric field, by a counteracting gas flow with a spatially non-uniform axial velocity distribution along an axis. The trapped ions are separated in space according to their ion mobility, and then the trapped ions are eluted over time according to their mobility by adjusting the gas velocity or the strength of the axial DC electric field (see, for example, U.S. Pat. No. 6,630,662 B1 to Loboda, and U.S. Pat. No. 7,838,826 B1 to Park). The theoretical basis of trapped ion mobility spectrometry is also described, for example, in the article "Fundamentals of Trapped Ion Mobility Spectrometry" by Michelmann et al.

[0005] (J. Am. Soc. Mass Spectrom., 2015, 26, 14-24).

[0006] Trapped ion mobility separators are known, for example, from U.S. Patent Application Publication US2022 / 0299473A1. The disclosed trapped ion mobility separators include an ion channel through which ions move from an inlet to an outlet along an axis, and the ion channel has an elongated cross-sectional profile perpendicular to the axis. Another trapped ion mobility separator is known, for example, from U.S. Patent 9683964 (Park et al.).

[0007] Typically, trapped ion mobility separators operate at pressures of several hundred Pascals (Pa), and the electric fields used in trapped ion mobility spectrometry range from a few volts per centimeter to several hundred volts per centimeter (e.g., 200 V / cm). In this low-field limit, the ion drift velocity is proportional to the electric field strength, and the mobility K is independent of the applied field. However, above about 20 Td (which involves an electric field strength of about 5000 V / cm at atmospheric pressure), the ion drift velocity is no longer directly proportional to the applied electric field, and the mobility K becomes dependent on the applied electric field, with a considerable nonlinear dependence on the electric field (EA Mason and EW McDaniel "Transport Properties of Ions in Gases" (Wiley, New York, 1988)). At high ratios of electric field strength to particle density, the mobility K is better represented by the low electric field constant mobility K(0) and the field-dependent term α i express:

[0008] K(E)=K(0)[1+α2(E / N) 2 +α4(E / N) 4 +…] (1)

[0009] Where E = electric field strength ([E] = V / m) and N = particle density ([N] = m -3 )

[0010] The effect of the dependence of mobility on the applied electric field is used in field asymmetric waveform ion mobility spectrometry (FAIMS), also known as differential mobility spectrometry (DMS). FAIMS is usually performed at atmospheric pressure and is based on the interaction of ion species with an applied electric field of high strength K. H The mobility under low electric field strength K LThe difference of mobility under - i.e. " differential mobility " of ion - separates gas phase ions. The differential mobility dK of the ion measured by FAIMS is provided by equation (2) below. The operating principle of FAIMS is for example described in the article " Atmospheric Pressure Ion Trapping in a Tandem FAIMS-FAIMS Coupled to aTOFMS: Studies with Electrospray Generated Gramicidin S Ions (atmospheric pressure ion trapping in the FAIMS-coupled to TOFMS in tandem FAIMS-: research on the gramicidin S ions generated by electrospray)" (J.Am.Soc.Mass Spectrom., 2001,12,1320-1330) of Guevremont et al. However, using the FAIMS technology, ions are only selectively transmitted through the analyzer region, and thus all ion species that are not transmitted are filtered out and discarded by discharge. This is a significant shortcoming, especially when analyzing complicated multi-component samples. When transmitting a selected component by FAIMS, all other components are lost.

[0011] dK(E)=K(0)[α2(E / N) 2 +α4(E / N) 4 +…] (2),

[0012] where dK(E) is the differential mobility of the ion.

[0013] The article "Differential Ion Mobility Separations in the Low-Pressure Regime" by Shvartsburg et al. (Analytical Chemistry, 2018, 90, 936-943) discloses a FAIMS filter operating under a rough vacuum and at a pressure as low as 4.7 Torr (6 mbar). U.S. Patent Application Publication 2013 / 0306858A1 discloses a linear ion trap in which an asymmetric voltage waveform is applied to electrodes forming the ion trap, which causes ions to be radially separated according to their differential ion mobility. An axial potential barrier is arranged at the exit of the ion trap so that ions having a first differential ion mobility and a first radial displacement are axially retained in the ion trap, but ions having a second differential ion mobility and a second radial displacement are axially ejected from the ion trap.

[0014] In view of the above, the present invention is based on the following purpose, namely, to improve and enrich the prior art and overcome the above-mentioned shortcomings by providing a new ion trapping and separation dimension in trapped ion mobility spectrometry. In particular, the purpose of the present invention can be seen as providing a trapped ion mobility separator, which allows to trap and separate all introduced ion species according to the different behavior of the mobility of the introduced ion species under low and high electric field strengths. Finally, there is also a need to expand and improve the analytical capabilities of hybrid mass spectrometry systems. In the context of the present disclosure, the trapped ion mobility separator is hereinafter referred to as "TIMS".

[0015] The invention solves the object on which it is based by a trapped ion mobility separator according to claim 1, a mass spectrometry system according to claim 14 and a method of analyzing ions according to claim 21. Advantageous embodiments of the invention are subject matter of the dependent claims and are explained in more detail in the following description. Summary of the invention

[0016] In a first aspect, the present invention provides a trapped ion mobility separator. The trapped ion mobility separator comprises:

[0017] an ion channel in which ions move along an axis between a first end of the ion channel and a second end of the ion channel, at the first end of the ion channel ions are introduced into the ion channel, the ion channel containing a gas through which the ions pass, wherein a radial confinement voltage is applied to the ion channel to prevent ions from escaping laterally out of the ion channel,

[0018] at least one first electrode and a second electrode, which are arranged spaced apart from each other along the axis of the ion channel to define an ion separation region therebetween,

[0019] a first generator, which generates an alternating axial electric field by applying a separation voltage to the first electrode and the second electrode, the first generator causing a first axial force to be exerted on the ions along the axis, the first axial force having an effect on the motion of the ions through its interaction with the gas, the motion of the ions being related to differential mobility, wherein the separation voltage is an alternating voltage and is applied so as to generate an electric field having a first field strength in a first time interval and to generate an opposite electric field having a second field strength in a second time interval after the first time interval, the second field strength being of a lower magnitude than the first field strength, the first time interval lasting a shorter time span than the second time interval,

[0020] a second generator causing a second axial force to be exerted on the ions along the axis, the second axial force at least temporarily counteracting the first axial force, wherein the first generator and the second generator are configured to cause at least one of the axial forces to vary in strength along the axis to trap the ions at mobility-dependent locations along the axis at which a force balance of the first and second axial forces exists for the ions,

[0021] Also included is an electrical controller that communicates with the first generator and the second generator and varies at least one of the first axial force and the second axial force over time so that trapped ions are progressively driven to one of the first end and the second end of the ion channel as a function of differential mobility.

[0022] The present invention is based on the recognition that the differential mobility behavior of ions can be used to trap and separate ions in a trapping ion mobility separator. In the context of the present invention, the term "differential mobility" is defined as the difference in mobility of an ion species at high electric field strength relative to the mobility at low electric field strength (see equation (2) above).

[0023] In this context, "low electric field strength" is defined as a field strength in the order of magnitude where the mobility K of the ions is essentially defined by the low electric field constant mobility K(0):

[0024] K(E)≈K(0)(3)

[0025] Or, in other words, referring to equation (1) above, "low electric field strength" means that the electric field strength is so low that the mathematical existence of the term α i (E / N) i become so small that their contribution to the determination of the mobility K is below the resolution limit and can therefore be neglected. Therefore, the term "low electric field strength" can be used under the assumption that the mobility K is represented by the low electric field constant mobility K(0), while at high electric field strength the mobility K is represented by the low electric field constant mobility K(0) and the field-dependent term α i (See equation (1) above) which indicates that is better.

[0026] In the context of the present disclosure, the introduction, separation and trapping of ions along the axis in the separation region by the force balance of the first axial force and the second axial force can be understood as an accumulation phase. In addition, in the context of the present disclosure, gradually driving the trapped ions to one of the first end and the second end of the ion channel as a function of the differential mobility of the trapped ions by changing at least one of the first axial force and the second axial force over time can be understood as a subsequent elution phase.

[0027] In the context of the present disclosure, the introduction of ions into the ion channel at the first end of the ion channel must be understood as introducing, or inserting, or inputting ions along the axis of the ion channel, and the ions move between the first end and the second end of the ion channel along the axis. In particular, this means that the ions are introduced along the axis and the ions are separated along the axis. Therefore, in the context of the present disclosure, the introduction of ions into the ion channel, the separation of ions in the separation region in the ion channel, and the elution of ions at one of the first end and the second end of the ion channel occur in a colinear manner.

[0028] In the context of the present disclosure, the above-mentioned alternating voltage is referred to as an alternating separation voltage. As described above, the first axial force caused by applying the above-mentioned alternating separation voltage to the first electrode and the second electrode can be described as a synthetic asymmetric waveform V (t), as referred to in the prior art. As known from the prior art, the alternating electric field represented by the asymmetric waveform V (t) can lead to different mobility behaviors of ions. Different drift velocities of ions can be generated as described below:

[0029] During a first time interval representing a high voltage portion of the asymmetric waveform, ions travel in the ion channel in a separation region between the first electrode and the second electrode at approximately v H =K H E H The longitudinal velocity v H Move, where E H is the applied high electric field, and K H is the high-field mobility under operating conditions (ie, electric field, pressure, temperature, etc.). The distance traveled by the ions during the first time interval of the asymmetric waveform can be approximated by d H =v H t H , where t H is the duration of the high field portion. During the second, longer time interval representing the opposite polarity, low voltage portion of the asymmetric waveform, the lateral velocity is v L =K L E L , where E L is the applied low electric field, K Lis the low field mobility under the operating conditions. The distance traveled is d L =V L t L , where t L is the duration of the low field portion. H Mobility K H Not equal to the low electric field E L Mobility K L , so within a single cycle, the ions experience a net displacement from their original position in the ion channel. If the ion species respond differently to high electric fields, then K H With K L The ratio of can be different for each ion species. Thus, the ions are separated according to their differential mobility.

[0030] According to the present invention, according to the arrangement of the first electrode and the second electrode along the axis of the ion channel of the trapping ion mobility separator, due to the alternating axial electric field generated above, the ions experience a net displacement along the axis in the ion channel. In the context of the present disclosure, this net displacement is referred to as differential mobility drift.

[0031] Therefore, the trapped ion mobility separator according to the present invention is called a differential trapped ion mobility separator (dTIMS). Compared with the TIMS device and method in the prior art, the dTIMS device and method of the present invention provide an additional tool for ion research in a trapped ion mobility separator, because the change of ion mobility (differential mobility) can be monitored, rather than the absolute ion mobility. This represents another dimension in which ions are separated by trapped ion mobility spectrometry. Compared with FAIMS, the dTIMS device and method allow all introduced ion species to be analyzed according to their differential mobility, and therefore, compared with the FAIMS technology, show significant advantages.

[0032] Taking advantage of the different behaviors of ion species in high and low electric fields, dTIMS allows the capture and separation of ion species essentially based on their charge state, since differential mobility is related to the charge state. This presents clear advantages, particularly for its application in hybrid mass spectrometry systems, especially if dTIMS is nested with a conventional ion mobility separator, such as TIMS, which is constructed and operated to disperse ions based on ion mobility, preferably in the low field limit, (tandem dTIMS / TIMS). In this way, ion species with a defined charge state can be selected and / or discarded for selective subsequent analysis. For example, ion species with a charge state Z=1 can be captured and individually transferred to an analytical device located downstream, such as a fragmentation unit, or can even be discarded, since the fragmentation spectrum of a singly charged ion species has no or little information. Finally, the addition of dTIMS to a mass spectrometry system produces a significant advantage, namely that the peak capacity can be increased due to the addition of another dimension of separation. This also results in the mass spectrum acquired by the mass analyzer as the final detector not being crowded or reduced in mass signals, peaks or features, which may facilitate its evaluation and interpretation.

[0033] It should be clear that the difference between the generated alternating axial electric field (which is used as the first axial force according to the differential trap ion mobility separator of the present disclosure) and the generated traveling wave field (which can be used for the trap ion mobility separator) is that with the alternating axial electric field, at substantially any time, the direction of the first axial force does not change along the axis in the separation region of the disclosed trap ion mobility separator. In contrast, with the traveling wave field, the axial force induced thereby has a direction change that depends on the position of the "traveling wave" within the separation region.

[0034] The first end of the ion channel can constitute an entrance area for ions to enter the ion channel. The first end of the ion channel can be tapered. In particular, the first end of the ion channel can include an ion funnel. In this way, ions can be focused when entering the ion channel. The second end of the ion channel can constitute an exit area for ions to leave the ion channel. The second end of the ion channel can be tapered. In particular, the second end of the ion channel can include an ion funnel. In this way, ions can be focused when leaving the ion channel. In addition, the first end and the second end are tapered, which advantageously leads to minimizing the influence of the electric field inside the dTIMS device on the device selectively located upstream or downstream. It is also conceivable that the first end of the ion channel can simultaneously constitute the entrance area of ​​ions and the exit area of ​​ions.

[0035] One or more varying voltages may be applied to the first electrode and the second electrode simultaneously. In particular, an alternating separation voltage is applied to the first electrode and the second electrode to generate an alternating axial electric field. In addition, a compensation voltage may be applied to the first electrode and the second electrode to generate a compensation electric field. In addition, a confinement voltage may be applied to the first electrode and the second electrode to generate a confinement electric field, thereby laterally confining ions in the gas-filled ion channel. The confinement voltage may be a radio frequency (RF) voltage or a combination of an RF voltage and a direct current (DC) voltage.

[0036] The dTIMS can be operated by substantially continuously varying at least one counteracting axial force to increase the first axial force relative to the second axial force, or to increase the second axial force relative to the first axial force. Alternatively, the dTIMS can be operated by step-wisely varying at least one counteracting force to increase the first axial force relative to the second axial force, or to increase the second axial force relative to the first axial force. The stepwise variation can be accomplished in a plurality of incremental steps or over several steps. For example, the stepwise variation can be accomplished over 3 to 100 steps, preferably 3 to 50 steps, and most preferably 3 to 10 steps. For example, a stepwise variation accomplished over 3 to 10 steps produces a corresponding number of fractions, each fraction comprising ion species having a specific range of differential mobilities.

[0037] The first time interval may correspond to less than half of a cycle of the separation voltage to a quarter of a cycle of the separation voltage. The second time interval may correspond to greater than half of a cycle of the separation voltage to three quarters of a cycle of the separation voltage. Preferably, the first time interval may correspond to a third of a cycle of the separation voltage, and the second time interval may correspond to two thirds of a cycle of the separation voltage. Selecting these time intervals, good resolution for separating ions can be achieved. In particular, the first time interval may last for about 3.33 μs, and the second time interval may last for about 6.66 μs.

[0038] The separation voltage applied by the first generator may be applied such that in the first time interval the potential is 500 V to 1000 V and in the second time interval the potential is -150 V to -450 V. Preferably, the separation voltage applied by the first generator may be applied such that in the first time interval the potential is 700 V and in the second time interval the potential is -350 V. Thus, in the first time interval an electric field may be generated whose field strength is high enough that the ion velocity is no longer directly proportional to the applied field and the mobility K is more suitably determined by the low field constant mobility K(0) and the field-dependent term αi Represented (see equation (1) above). In particular, in the first time interval, a voltage of 350V can be applied to the first electrode, a voltage of -350V can be applied to the second electrode, and in the second time interval, a voltage of -175V can be applied to the first electrode, and a voltage of 175V can be applied to the second electrode. In general, it is preferred to generate the voltage between the first and second electrodes by applying two potentials of opposite signs to these electrodes. By keeping the absolute potential on any given electrode as small as possible while generating the maximum possible potential difference across the analyzer, ion separation can be maximized while minimizing the risk of discharge between electrodes or electrical elements. Alternatively, it is conceivable that in the first time interval, a voltage of 700V can be applied to the first electrode and the second electrode has a potential of 0V, or in other words, the second electrode is maintained at ground potential, and in the second time interval, a voltage of -350V can be applied to the first electrode and the second electrode has a potential of 0V, or in other words, the second electrode is maintained at ground potential.

[0039] Select the above-mentioned time intervals respectively corresponding to the first time interval (short time interval t H ) and the second time interval (long time interval t L ) duration, and the voltage level or potential height (high voltage V H and low voltage V L ) ensures that the integrated voltage-time product (∫t·V(t)dt) during each complete cycle, and therefore the field-time product, is substantially zero. In particular, assuming that the electric field strength in the time interval is constant, the above preferred parameters substantially ensure that (V H t H )+(V L t L )=0.

[0040] However, it should be noted at this point that the combination of voltage and pressure constitutes a non-linear behavior of the drift velocity / mobility of the ions. Therefore, even voltages lower in magnitude than the above mentioned voltages may be sufficient to induce this non-linear behavior of the mobility if there is a correspondingly adjusted pressure setting.

[0041] In a preferred embodiment, the separation voltage is a substantially rectangular voltage. A substantially rectangular voltage provides the advantage that in the event of a change in the electric field, the full field strength is immediately present. In an alternative embodiment, the separation voltage may be a substantially double-sinusoidal voltage. It is also conceivable that the separation voltage may be a triangular voltage.

[0042] In another preferred embodiment, the applied separation voltage has a frequency of 50kHz to 2MHz. Preferably, the applied separation voltage has a frequency of 80kHz to 120kHz. Most preferably, the applied separation voltage has a frequency of 100kHz.

[0043] In another preferred embodiment, the alternating axial electric field generated by the first generator has a maximum strength of 20Td to 500Td. In the context of the present disclosure, the alternating axial electric field is also referred to as a "dispersed electric field". Td (townsend) is the unit of the ratio of electric field strength to gas particle density. When the ratio of electric field strength to particle density (E / N) is about 20Td (1Td = 10 -17 Vcm 2 ) or more, the ion mobility has a considerable nonlinear dependence on the electric field. A ratio of electric field strength to particle density (E / N) of about 20 Td relates to an electric field strength of about 5000 V / cm at atmospheric pressure. Preferably, the alternating axial electric field generated by the first generator has a strength of 150 Td to 250 Td. Most preferably, the alternating axial electric field generated by the first generator has a strength of 200 Td.

[0044] The second axial force can be induced in different ways. In a preferred embodiment, the second axial force is caused by the second generator, which applies a compensation voltage to the first electrode and the second electrode to generate a compensation electric field. The generated compensation electric field can be oriented downstream, that is, toward the outlet end. Alternatively, the generated compensation electric field can be oriented upstream, that is, toward the inlet end. Finally, the generated compensation electric field must be oriented so that the second axial force represented by the compensation electric field offsets the first axial force. Depending on the direction of the compensation electric field, the movement of the ions is oriented toward the first end or the second end of the ion channel. Preferably, the second axial force is caused by the second generator by applying a DC voltage to the first electrode and the second electrode to generate an axial direct current field (DC field). This gives an advantage over the prior art TIMS, that is, dTIMS can be operated when the gas is stationary. This provides an additional advantage, that is, expensive gases, such as helium, can also be used. In the prior art TIMS analyzer, the force on the ions is usually generated using a moving gas. However, the gas laminar flow through the analyzer forms a parabolic flow profile. The advantage of using a DC electric field instead of gas flow as the second axial force is that the DC field can be designed so that it is constant along the lateral direction, thereby causing a uniform force in the lateral direction on the ions, and thus causing a uniform drift across the entire internal width of the ion channel. In addition, the cross-section and length of TIMS necessarily determine its gas conductivity. Therefore, the lateral dimensions and length of the TIMS analyzer using axial gas flow as the second axial force will be limited by the pumping speed of a commercially reasonable pump. The advantage of the dTIMS operated under the condition of static gas is that the lateral extension of the device does not affect or limit its resolution.

[0045] In an alternative embodiment, the second axial force is induced by the second generator by applying a transient DC voltage to the first electrode and the second electrode to produce an axial transient DC electric field (also called a "traveling wave field").

[0046] However, those skilled in the art will understand that, in the context of the present invention, where two electric fields are generated as first and second axial forces, the above-mentioned first generator and second generator may also be understood as a common electrical component having two different electrical units (representing the first and second generators) that generate the first and second axial forces, respectively.

[0047] In yet another embodiment, the second axial force is caused by the second generator generating an axial airflow.

[0048] In another preferred embodiment, the first electrode and the second electrode are shaped and arranged so that the first electrode and the second electrode surround the separation region perpendicular to the axis in the ion channel. Like this, the electric field produced by providing voltage to these electrodes affects the whole volume of ion channel. This also advantageously causes ions to be confined in the ion channel filled with gas, or prevents ions from escaping ion channel laterally. The first electrode can be assigned to the first end of the ion channel. The second electrode can be assigned to the second end of the ion channel. Therefore, the electric field produced by supplying voltage to the electrodes is parallel to the longitudinal orientation of ion channel, so that ions move along the desired direction, i.e., move between the first end and the second end of ion channel along the longitudinal direction.

[0049] In another preferred embodiment, the ion channel includes a plurality of additional electrodes, which have the same shape and arrangement as the first electrode and the second electrode. The additional electrode is located between the first electrode and the second electrode in the ion channel along the axis. In this way, a stable and uniform electric field can be obtained. The additional electrodes can be arranged to be approximately 1 mm apart from each other. At the same time or in an alternative embodiment, the additional electrodes can be connected by a resistor chain. In particular, all resistors can have the same resistance. In this way, a uniform distribution of voltage is ensured. At the same time or in an alternative embodiment, the additional electrodes can be supplied with voltage using a separate voltage generator. In this way, different voltages can be supplied to each additional electrode. The additional electrodes can be stacked (stacked electrodes). An alternating separation voltage for generating an alternating axial electric field can be applied to the additional electrode. In addition, a compensation voltage for generating a compensation electric field can be applied to the additional electrode. Another RF voltage, or a combination of an RF voltage and a DC voltage can be applied to the additional electrode. The latter allows ions to be confined in a gas-filled ion channel.

[0050] In another preferred embodiment, the ion channel has an elongated cross-sectional profile perpendicular to the axis, which has a first extension direction and a second extension direction. Therefore, the first extension direction is preferably longer than the second extension direction. In the longitudinal direction (z) along the axis, the ion channel can have a size of 10mm to 30mm. Preferably, the ion channel can have a size of 15mm in the longitudinal direction along the axis. In the first transverse direction (x) perpendicular to the longitudinal extension and representing the first extension direction, the ion channel can have a size of 10mm to 300mm. Preferably, in the first transverse direction, the ion channel can have a size of 60mm. In the second transverse direction (y) perpendicular to the longitudinal extension and representing the second extension direction, the ion channel can have a size of 5mm to 10mm. Preferably, in the second transverse direction, the ion channel can have a size of 8mm. This transversely extended shape advantageously allows ions to be trapped in an extended volume that is essentially elongated in the transverse direction without having to be trapped along a line. In this way, compared with devices without a transversely extended shape, the charge capacity is significantly increased without limiting the mobility resolution. Furthermore, this allows to obtain high field strengths in the longitudinal direction by applying reasonable voltages to the electrodes.The ion channel may be shaped straight or curved along the extended lateral dimension.

[0051] In an alternative preferred embodiment, the ion channel has a circular cross-sectional profile perpendicular to the longitudinal axis. The circular cross-sectional profile may have a diameter of 30mm to 70mm. Preferably, the circular cross-sectional profile may have a diameter of 50mm. In this embodiment, the ion channel may have an outer wall. The outer wall may represent the outer radius of the ion channel. In addition, the ion channel may have an inner wall. The inner wall may represent the inner radius of the ion channel. A gap may be provided between the outer radius and the inner radius. The gap may constitute a ring, i.e., the difference (annular space) between the outer radius and the inner radius. The ring may have a size of 8mm, which represents the thickness of the ring. Ions may be radially confined in the ring. Confining ions in the ring provides an increased charge capacity. This shaping method may further increase the charge capacity. In this embodiment, in the longitudinal direction (z) along the axis, the ion channel may have a size of 10mm to 30mm. Preferably, the ion channel may have a size of 15mm in the longitudinal direction along the axis.

[0052] In another preferred embodiment, the trapped ion mobility separator is coupled to a vacuum system designed and configured to operate dTIMS at a pressure in the range of 0.5 mbar to 20 mbar. Preferably, the vacuum system is designed and configured to operate dTIMS at a pressure in the range of 2 mbar to 10 mbar. For this purpose, the vacuum system may include a pump. This pressure range allows for lateral ion confinement by using RF electric fields.

[0053] In another preferred embodiment, the trapped ion mobility separator also includes an ion trap. The ion trap is located upstream of the separation region in the ion channel. The ion trap may be adjacent to the separation region. The ion trap is configured to store ions. The additional ion trap allows the dTIMS to operate in a parallel accumulation mode in a beneficial manner. This means that the ion trap can accumulate ions in an advantageous manner while the ions can be separated downstream in the separation region. In particular, the ion trap allows a parallel accumulation mode with a duty cycle close to one hundred percent. Preferably, the ion trap may have a width substantially the same as the separation region. Preferably, the ion trap may have a height substantially the same as the separation region.

[0054] In another preferred embodiment, the first generator and the second generator are configured such that the effective axial force generated by the first axial force and the second axial force forms a barrier having a substantially constant plateau, at which trapped ions leave the separation region and / or the ion channel.

[0055] In another preferred embodiment, the separation voltage applied by the first generator is applied such that the potential applied to the first electrode has an opposite polarity to the potential applied to the second electrode.

[0056] In another preferred embodiment, the first generator and the second generator are configured such that the variation over time of at least one of the first axial force and the second axial force is gradual, thereby resulting in the release of multiple fractions, each fraction comprising multiple ion species, or is substantially continuous.

[0057] The trapped ion mobility separator according to the present invention can be operated as a separate device (or stand-alone device) for measuring the differential mobility of ions. Alternatively, it is conceivable that the dTIMS is coupled to other devices, such as a mass spectrometer (mass analyzer). When the dTIMS is coupled to a mass spectrometer, both the differential mobility and the mass of the ions can be determined from the measured data.

[0058] In a second aspect, the present invention provides a mass spectrometry system. The mass spectrometry system comprises an ion source and a mass analyzer having an ion detector. In addition, the mass spectrometry system comprises at least a first trapped ion mobility separator located downstream of the ion source. At the same time or in an alternative embodiment, the first trapped ion mobility separator is located upstream of the mass analyzer. The first trapped ion mobility separator comprises:

[0059] an ion channel in which ions move along an axis between a first end of the ion channel and a second end of the ion channel, at the first end of the ion channel ions are introduced into the ion channel, the ion channel containing a gas through which the ions pass, wherein a radial confinement voltage is supplied to the ion channel to prevent ions from escaping laterally from the ion channel,

[0060] at least a first electrode and a second electrode arranged spaced apart from each other along the axis of the ion channel to define an ion separation region therebetween,

[0061] a first generator, by applying a separation voltage to the first electrode and the second electrode to generate an alternating axial electric field, the first generator causing a first axial force to be exerted on the ions along the axis, by which it interacts with the gas, the first axial force having an effect on the motion of the ions, the motion of the ions being related to differential mobility, wherein the separation voltage is an alternating voltage and is applied so as to generate an electric field having a first field strength in a first time interval and a reverse electric field having a second field strength in a second time interval after the first time interval, the second field strength being lower in magnitude than the first field strength, the first time interval lasting a shorter time span than the second time interval,

[0062] a second generator causing a second axial force to be exerted on the ions along the axis, the second axial force at least temporarily counteracting the first axial force, wherein the first generator and the second generator are configured such that at least one of the axial forces varies in strength along the axis to trap the ions at mobility-dependent locations along the axis at which a force balance of the first and second axial forces exists for the ions,

[0063] Also included is an electrical controller that communicates with the first generator and the second generator and varies at least one of the first axial force and the second axial force over time so that trapped ions are gradually driven to one of the first end and the second end of the ion channel as a function of their differential mobility.

[0064] Therefore, the above-mentioned trapped ion mobility separator can be part of a hybrid mass spectrometry system, which system further includes at least one ion source located upstream of the trapped ion mobility separator, and a mass analyzer having an ion detector located downstream of the trapped ion mobility separator. The above-mentioned trapped ion mobility separator according to the present invention is called a differential trapped ion mobility separator (dTIMS).

[0065] The ion source of mass spectrometry system is arranged to produce ions. For example, the ion source of mass spectrometry system can produce ions using spray ionization (for example, electrospray (ESI) or thermospray). Alternatively, the ion source of mass spectrometry system can produce ions using desorption ionization (for example, matrix assisted laser / desorption ionization (MALDI) or secondary ionization (SIMS)). In another alternative, the ion source of mass spectrometry system can produce ions using chemical ionization (CI). In another alternative, the ion source of mass spectrometry system can produce ions using photoionization (PI). In another alternative, the ion source of mass spectrometry system can produce ions using electron impact ionization (EI). In another alternative, the ion source of mass spectrometry system can produce ions using gas discharge ionization.

[0066] The mass analyzer of the mass spectrometry system is arranged to analyze the ions according to their mass or more precisely according to their mass-to-charge ratio. For example, the mass analyzer may be a time-of-flight analyzer. Preferably, the mass analyzer may be a time-of-flight analyzer with orthogonal injection of ions. Alternatively, the mass analyzer may be a Kingdon type electrostatic ion trap, such as the one from Thermo Scientific. In another alternative, the mass analyser may be an RF ion trap. In another alternative, the mass analyser may be an ion cyclotron resonance (ICR) ion trap or a quadrupole mass filter.

[0067] In a preferred embodiment, the mass spectrometry system further comprises a fragmentation unit. The fragmentation unit is configured to dissociate ions into fragment ions. Preferably, the fragmentation unit is located between the first trapped ion mobility separator and the mass analyzer. For example, ions can be dissociated in the fragmentation unit by collision induced dissociation (CID). Alternatively, ions can be dissociated in the fragmentation unit by surface induced dissociation (SID). In another alternative, ions can be dissociated in the fragmentation unit by photodissociation (PD). In another alternative, ions can be dissociated in the fragmentation unit by electron induced dissociation, such as electron capture dissociation (ECD), electron transfer dissociation (ETD), collision activation after electron transfer dissociation (ETcD), or activation (AI-ETD) occurring simultaneously with electron transfer dissociation. In another alternative, ions can be dissociated in the fragmentation unit by reaction with highly excited or free radical neutral particles. It is also conceivable to have an embodiment of an additional dTIMS located downstream of the fragmentation unit. This is beneficial for selecting fragment ions with defined charge states, since dTIMS allows trapping and separation of ion species essentially based on their charge state, as differential mobility is charge state dependent.

[0068] In another preferred embodiment, the mass spectrometry system further comprises a mass filter. Preferably, the mass filter is located between the first trapped ion mobility separator and the fragmentation unit.

[0069] In another preferred embodiment, the mass spectrometry system further comprises a second ion mobility separator, preferably a trapping ion mobility separator. Preferably, the second ion mobility separator is located downstream of the first trapping ion mobility separator. Preferably, the second ion mobility separator is a trapping ion mobility separator constructed and operated to disperse ions according to ion mobility, preferably at a low field limit. Alternatively, the second ion mobility separator may be another ion mobility separator according to the present invention. Preferably, the first trapping ion mobility separator and the second ion mobility separator are nestedly coupled, i.e., the first trapping ion mobility separator operates on a much larger time scale than the second ion mobility separator, so that the second ion mobility separator can analyze a single ion species separated by the first trapping ion mobility separator, or each fraction provided by the first trapping ion mobility separator. In this way, the information content of the two devices (determined by the field-related term α) is relatively large. i The differential mobility given, and the constant mobility K(0)) can be added together. A system comprising a first differential TIMS coupled to a TIMS nest may be referred to as a tandem dTIMS / TIMS, which is constructed and operated to disperse ions according to ion mobility, preferably in the low field limit.

[0070] In another preferred embodiment, the mass spectrometry system further comprises a first housing assigned to the first trapped ion mobility separator. In particular, the first housing may surround the first trapped ion mobility separator. In addition, the mass spectrometry system comprises a second housing assigned to the second ion mobility separator. In particular, the second housing may surround the second ion mobility separator. The first housing and the second housing may each constitute a vacuum chamber. The first housing and the second housing may each contain a gas (drift gas). The gas assigned to the first housing (and therefore to the first ion mobility separator) may be different from the gas assigned to the second housing (and therefore to the second ion mobility separator). In particular, the gas assigned to the first housing and the first ion mobility separator may be a gas different from the gas assigned to the second housing and the second ion mobility separator. For example, the gas used may be one of H2, He, Ar, N2, CO2 or a mixture of these gases. It is conceivable to use other gases other than the above gases or a mixture of any other gases or a mixture with any other gas. Optionally, a modifier may be introduced into the gas. The modifier may include acetonitrile, methanol, small molecule hydrocarbons, SF6 or any other vapor. The use of different gases in the first and second housings can advantageously allow ions that may not be adequately separated in the first ion mobility separator to be separated in the second ion mobility separator, since the type of gas has an effect on the drift velocity of the ions. It should be noted that even if the ion mobility separator is operated with the gas stationary (which is the case when both the first and second axial forces are generated by the electric field), there is a low gas flow. However, this low gas flow is only used for the gas environment within the separation housing.

[0071] In another preferred embodiment, the mass spectrometry system further comprises an ion selector. The ion selector is configured to select ions. Preferably, the ion selector is located between the first trapping ion mobility separator and the second ion mobility separator.

[0072] In another preferred embodiment, the mass spectrometry system further comprises at least one ion trap. The ion trap is configured to store ions. Preferably, the first ion trap is located upstream of the first trapped ion mobility separator. Additionally or alternatively, the second ion trap is located between the first trapped ion mobility separator and the second ion mobility separator.

[0073] Furthermore, the mass spectrometry system may include a separation device. The separation device may be a gas chromatography device. Alternatively, the separation device may be a liquid chromatography device. It is also conceivable that the mass spectrometry system further includes an electrophoresis device. Alternatively, the electrophoresis device may be coupled to a hybrid mass spectrometry system.

[0074] The preferred embodiments described for the above-described trapped ion mobility separator are also preferred embodiments of the mass spectrometry system. The preferred embodiments of the mass spectrometry system involving the trapped ion mobility separator are also preferred embodiments of the above-described trapped ion mobility separator.

[0075] In a third aspect, the present invention provides a method for analyzing ions using a first trapped ion mobility separator. Preferably, the method is performed in a mass spectrometry system. The method comprises the following steps:

[0076] providing an ion channel in which ions move along an axis between a first end of the ion channel and a second end of the ion channel, at the first end of the ion channel ions are introduced into the ion channel, the ion channel containing a gas through which the ions pass, wherein the ion channel is supplied with a radial confinement voltage for preventing ions from escaping the ion channel laterally,

[0077] providing at least a first electrode and a second electrode arranged to be spaced apart from each other along the axis of the ion channel to define an ion separation region therebetween,

[0078] applying an alternating separation voltage to the first electrode and the second electrode to generate an alternating axial electric field, generating a first axial force applied to the ions along the axis, wherein the first axial force has an effect on the motion of the ions through its interaction with the gas, and the motion of the ions is related to differential mobility,

[0079] applying the alternating separation voltage so that for a first time interval an electric field having a first field strength is generated and for a second time interval following the first time interval an opposite electric field having a second field strength is generated, the second field strength being lower in magnitude than the first field strength, the first time interval lasting a shorter time span than the second time interval,

[0080] generating a second axial force that is applied to the ions along the axis and that at least temporarily counteracts the first axial force,

[0081] varying at least one of the axial forces in strength along the axis to trap the ion at a mobility-dependent position along the axial direction where a force balance of the first axial force and the second axial force exists for the ion,

[0082] At least one of the first axial force and the second axial force is varied over time such that the trapped ions are gradually driven to one of the first end and the second end of the ion channel as a function of the differential mobility of the trapped ions.

[0083] The above-mentioned trapped ion mobility separator according to the present invention is referred to as a differential trapped ion mobility separator (dTIMS).

[0084] The method for analyzing ions comprises the steps of: introducing ions into the ion channel at the first end of the ion channel. Introducing ions into the ion channel at the first end of the ion channel should be understood as introducing ions along the axis of the ion channel, and the ions move between the first end and the second end of the ion channel along the axis. In particular, this means that the ions are introduced along the axis and they are separated along the axis. Introducing ions into the ion channel can be understood as injecting or inserting or inputting ions into the ion channel.

[0085] The first time interval may correspond to less than half of a cycle of the separation voltage to a quarter of a cycle of the separation voltage, and the second time interval may correspond to greater than half of a cycle of the separation voltage to three quarters of a cycle of the separation voltage. Preferably, the first time interval may correspond to a third of a cycle of the separation voltage, and the second time interval may correspond to two thirds of a cycle of the separation voltage. These time intervals are selected to achieve good resolution in separating ions. In particular, the first time interval may last for about 3.33 μs, and the second time interval may last for about 6.66 μs.

[0086] In a preferred embodiment, the method for analyzing ions further comprises the step of generating an alternating axial electric field with a maximum strength of 20Td to 500Td, preferably 150Td to 250Td, most preferably 200Td. Preferably, an alternating axial electric field with a strength of 150Td to 250Td is generated. Most preferably, an alternating axial electric field with a strength of 200Td is generated. Preferably, the first generator can be used to generate the alternating axial electric field.

[0087] The first generator may apply the separation voltage such that the potential is 500 V to 1000 V in the first time interval and is -150 V to -450 V in the second time interval. Preferably, the first generator may apply the separation voltage such that the potential is 700 V in the first time interval and is -350 V in the second time interval. Thus, in the first time interval, an electric field may be generated whose field strength is high enough that the ion velocity is no longer directly proportional to the applied electric field and the mobility K is more suitably determined by the low field constant mobility K(0) and the field-dependent term α i(See equation (1) above). In particular, in the first time interval, a voltage of 350V can be applied to the first electrode and a voltage of -350V can be applied to the second electrode. In particular, in the second time interval, a voltage of -175V can be applied to the first electrode and a voltage of 175V can be applied to the second electrode. In general, it is preferred to generate a voltage between the first and second electrodes by applying two potentials of opposite signs to these electrodes. By keeping the absolute potential on any given electrode as small as possible while generating the maximum possible potential difference across the analyzer, ion separation can be maximized while minimizing the risk of discharge between electrodes or electrical elements. Alternatively, it is conceivable that in the first time interval, a voltage of 700V can be applied to the first electrode and the second electrode has a potential of 0V, or in other words, the second electrode is maintained at ground potential, and in the second time interval, a voltage of -350V can be applied to the first electrode and the second electrode has a potential of 0V, or in other words, the second electrode is maintained at ground potential.

[0088] However, it should be noted at this point that the combination of voltage and pressure constitutes a non-linear behavior of the drift velocity / mobility of the ions. Therefore, even voltages lower in magnitude than the above mentioned voltages may be sufficient to induce this non-linear behavior if there is a correspondingly adjusted pressure setting.

[0089] In another preferred embodiment, the method for analyzing ions further comprises the step of analyzing the separated ions as a function of mobility in a second ion mobility separator. Preferably, the second ion mobility separator is a trapped ion mobility separator constructed and operated to disperse ions according to mobility, preferably in the low field limit. Preferably, the second trapped ion mobility separator is located downstream of the first trapped ion mobility separator.

[0090] In another preferred embodiment, the method for analyzing ions further comprises the step of analyzing the separated ions as a function of mass in a mass analyzer. The mass analyzer is located downstream of the second ion mobility separator, which is constructed and operated to disperse the ions according to ion mobility, preferably in the low field limit.

[0091] In another preferred embodiment, the method for analyzing ions further comprises the steps of: dissociating the separated ions into fragment ions and analyzing the fragment ions in a mass analyzer. Preferably, the ions are dissociated in a fragmentation unit. Preferably, the fragmentation unit and the mass analyzer are located downstream of the first trapped ion mobility separator. In another embodiment, a second ion mobility separator is provided, which is constructed and operated to disperse ions according to ion mobility, preferably in low field confinement, and is located downstream of the first trapped ion mobility separator, and the fragmentation unit and the mass analyzer are preferably located downstream of the second ion mobility separator.

[0092] In another preferred embodiment, the method for analyzing ions further comprises the step of selecting and / or filtering the separated ions according to mass before fragmentation. Additionally, or in an alternative embodiment, the method for analyzing ions further comprises the step of selecting and / or filtering the separated ions according to charge state of the separated ions before fragmentation.

[0093] In another preferred embodiment, the method for analyzing ions further comprises the step of accumulating ions from an ion source in an ion trap located upstream of the first trapping ion mobility separator while analyzing ions in the first trapping ion mobility separator.

[0094] In another preferred embodiment, the method for analyzing ions further comprises the step of gradually changing at least one of the first axial force and the second axial force over time so that the trapped ions are driven to one of the first end and the second end of the ion channel in multiple separated ion fractions as a function of their differential mobility.

[0095] In another preferred embodiment, the method for analyzing ions further comprises the step of analyzing the separated ion fraction as a mobility-dependent function in a second ion mobility separator. Preferably, the second ion mobility separator is a trapping ion mobility separator constructed and operated to disperse ions according to ion mobility, preferably at a low field limit. The second ion mobility separator is located downstream of the first trapping ion mobility separator, wherein preferably the first trapping ion mobility separator and the second ion mobility separator are nestedly coupled, i.e., the first trapping ion mobility separator operates on a much larger time scale than the second ion mobility separator, so that the second ion mobility separator can analyze a single ion species separated by the first trapping ion mobility separator, or each fraction provided by the first trapping ion mobility separator.

[0096] In another preferred embodiment, the method for analyzing ions further comprises the step of deselecting a portion of ions consisting essentially of singly charged ion species.

[0097] The preferred embodiments described for the above-mentioned trapped ion mobility separator according to the present invention, or the preferred embodiments described for the above-mentioned mass spectrometry system are also preferred embodiments of the ion analysis method.

[0098] The previously disclosed principles may be combined, contextualized or implemented with one or more of the following aspects, in particular to provide a method for analyzing complex samples:

[0099] (a) An instrument is provided, comprising an ion source, a dTIMS according to the present disclosure, an ion mobility separator (IMS) and a mass analyser.

[0100] Preferably, IMS is a trapped ion mobility separator (TIMS). The mass analyzer can be one of the following: a quadrupole (Q) mass analyzer or a time-of-flight (TOF) mass analyzer. For example, the ion source can use spray ionization (e.g., electrospray (ESI) or thermal spray) to produce ions. Alternatively, the ion source can use desorption ionization (e.g., matrix-assisted laser / desorption ionization (MALDI) or secondary ionization (SIMS)) to produce ions. In another alternative, the ion source can use chemical ionization (CI), photoionization (PI), electron impact ionization (EI) or atmospheric pressure chemical ionization (APCI) to produce ions. In another alternative, the ion source can use gas discharge ionization to produce ions. Preferably, an additional separation mechanism is provided upstream of the ion source. The separation mechanism provided upstream of the ion source can be a separation mechanism suitable for performing one of the following methods: liquid chromatography (LC), gas chromatography (GC), capillary electrophoresis (CE). Preferably, the instrument includes a vacuum system. The vacuum system can occupy all components located downstream of the ion source.

[0101] (b) Perform liquid chromatography (LC) on the sample.

[0102] (c) Using an ion source (eg, ESI) to ionize sample material eluted from the LC (or another separation mechanism located upstream of the ion source), and introducing the ionized sample material (ions) into the vacuum system of the instrument.

[0103] (d) Ions are accumulated in an ion trap located upstream of the dTIMS.

[0104] (e) Ions are injected from the ion trap into the dTIMS located downstream of the ion trap.

[0105] (f) releasing ions from the dTIMS according to their differential mobility.

[0106] Preferably, the ions are released from the dTIMS in fractions. The ions may be released from the dTIMS as a single fraction or as multiple fractions, each fraction having a selected differential mobility range. The remaining ions that are not released may be eliminated.

[0107] (g) Perform parallel accumulation and continuous fragmentation (PASEF, see Florian Meier et al., J. Proteome Res. 2015, 14, 12, 5378-5387) of the ions released from the dTIMS using one of the following instruments located downstream of the dTIMS: ion mobility spectrometer (IMS), quadrupole (Q) mass analyzer, fragmentation unit, time-of-flight (TOF) mass analyzer, in particular a TOF analyzer using orthogonal acceleration.

[0108] Preferably, PASEF is one of DDA PASEF (DDA = data dependent analyses), DIA PASEF (DIA = data independent analysis), MIDIA PASEF (MIDIA = Maximizing Information content in DIA), synchronous PASEF or any other variant of PASEF. BRIEF DESCRIPTION OF THE DRAWINGS

[0109] The present invention may be better understood by reference to the following drawings, in which the elements are not necessarily drawn to scale, emphasis instead being placed upon illustrating the principles of the invention (generally schematically):

[0110] Figure 1a-1b shows a schematic perspective view of a first embodiment of a trapping ion mobility separator according to the present invention, Figure 1c shows a schematic longitudinal cross-sectional view of a first embodiment of a trapping ion mobility separator according to the present invention,

[0111] Figure 2 A graph showing the dispersion potential along the longitudinal direction of the ion channel,

[0112] Figure 3 A graph showing the dispersion field along the longitudinal direction of the ion channel is shown.

[0113] Figure 4a (Left) shows the Figure 2 The time curve of the dispersion potential shown in Figure 4b (right) shows the Figure 2 The time curve of the dispersion potential shown in

[0114] Figure 5 A graph showing the compensation potential along the longitudinal direction of the ion channel is shown.

[0115] Figure 6 shows a graph of the normalized compensation field along the longitudinal direction of the ion channel,

[0116] Figure 7a shows the simulation results summarizing the number of ions at different elution times according to their charge state Z. Figure 7b shows the simulation results, summarizing the ion elution probability at different elution times according to the charge state Z of the ion,

[0117] Figure 8a (Left) shows the simulation results, summarizing the ion mobility with elution time according to the charge state Z of the ion, Figure 8b (right) shows the simulation results, summarizing the differential mobility of ions with elution time according to their charge state Z.

[0118] Fig. 9 shows a schematic perspective view of a second embodiment of a trapping ion mobility separator according to the present invention,

[0119] FIG. 10 schematically shows the working principle of the second embodiment of the trapping ion mobility separator according to the present invention at different time points during the analysis process ( Fig.10a , Fig.10b , Fig.10c ),

[0120] Fig.11a shows a schematic longitudinal sectional view of a third embodiment of a trapping ion mobility separator according to the present invention, Fig.11b shows a schematic perspective view (cut away) of a third embodiment of a trapping ion mobility separator,

[0121] Fig.12 shows a schematic perspective view of a fourth embodiment of a trapping ion mobility separator according to the present invention,

[0122] FIG. 13 schematically shows the working principle of the fourth embodiment of the trapping ion mobility separator according to the present invention at different time points during the analysis process ( Fig.13a , Fig.13b , Fig.13c , Fig.13d , Fig.13e ),

[0123] Fig.14 shows a time graph of the dispersion potential applied to the first electrode, and

[0124] Fig.15 A schematic diagram of a mass spectrometry system according to the present invention is shown. DETAILED DESCRIPTION

[0125] While the invention has been shown and described with reference to several different embodiments thereof, it will be recognized by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the following claims.

[0126] Figure 1a-1b shows a schematic perspective view of a first embodiment of a trapping ion mobility separator 10 according to the present invention, Figure 1c A schematic longitudinal cross-sectional view of a first embodiment of a trapped ion mobility separator 10 is shown. The trapped ion mobility separator 10 is used to trap and separate ions according to their differential mobility. Therefore, the trapped ion mobility separator 10 is a differential trapped ion mobility separator (dTIMS). The trapped ion mobility separator 10 can be part of a mass spectrometry system 100.

[0127] The trapping ion mobility separator 10 includes an ion channel 12. The ion channel 12 has a first end 14. In addition, the ion channel 12 has a second end 16, which is away from the first end 14. In this embodiment, the first end 14 and the second end 16 are shaped to be tapered. The ion channel 12 can be provided by an external ion source 112 ( Fig.15 ) can move through the ion channel 12 between the first end 14 and the second end 16 of the ion channel 12 along the axis 18 shown by the dotted line in the figure. In this embodiment, the first end 14 represents the entrance area 15 of the ions. In particular, in this embodiment, the entrance area 15 is an entrance funnel. In this embodiment, the second end 16 represents the exit area 17 of the ions. In particular, in this embodiment, the exit area 17 is an exit funnel. The ion channel 12 contains a gas through which the ions pass.

[0128] The trapped ion mobility separator 10 comprises a first electrode 20 which is Figure 1a In addition, the ion channel 12 includes a second electrode 22, which is Figure 1a The first electrode 20 and the second electrode 22 are arranged spaced apart from each other along the axis 18 inside the ion channel 12 to define an ion separation region 24 therebetween. The first electrode 20 is shaped and arranged so that the first electrode 20 surrounds the separation region 24 in the ion channel 12 perpendicular to the axis 18. The second electrode 22 is shaped and arranged so that the second electrode 22 surrounds the separation region 24 in the ion channel 12 perpendicular to the axis 18.

[0129] The trapping ion mobility separator 10 includes a plurality of additional electrodes 26 ( Figure 1b , Figure 1c). In this embodiment, the ion channel 12 includes nineteen additional electrodes 26, of which only one of the additional electrodes is provided with a reference numeral for better overview. The additional electrode 26 has the same shape and arrangement as the first electrode 20 and the second electrode 22. The additional electrode 26 is located between the first electrode 20 and the second electrode 22 at the ion channel 12 along the axis 18. In particular, the additional electrodes 26 are spaced about 1 mm from each other and about 1 mm from the first electrode 20 and the second electrode 22, respectively. The additional electrodes 26 are connected by a resistor chain (not shown in the figure). An RF limiting voltage is provided to the additional electrode 26 to prevent ions from escaping the ion channel 12 laterally, i.e., in the x and y directions. The first electrode 20, the second electrode 22 and the additional electrode 26 together define the ion channel 12.

[0130] The trapping ion mobility separator 10 comprises a first generator 30 ( Fig.15 ). The first generator 30 generates a first axial force that should be applied to the ions along the axis 18. In order to generate the first axial force, the first generator 30 applies an alternating separation voltage to the first electrode 20 and the second electrode 22, which generates an alternating axial electric field. Through interaction with the gas, the first axial force has an effect on the ion motion, which is related to the differential mobility. In addition, the trapped ion mobility separator 10 includes a second generator 32 ( Fig.15 ). The second generator 32 generates a second axial force that should be applied to the ions along the axis 18. In this embodiment, to generate the second axial force, the second generator 32 applies a direct current (DC) voltage to the first electrode 20 and the second electrode 22, which generates an axial direct current field (DC field). The second axial force counteracts the first axial force. In particular, the second axial force temporarily counteracts the first axial force.

[0131] In addition, the trapping ion mobility separator 10 includes an electronic controller 34 ( Fig.15 ). The electrical controller 34 is in communication with the first generator 30 and the second generator 32. The electrical controller 34 is configured to vary at least one of the first axial force and the second axial force over time.

[0132] In this embodiment, the ion channel 12 has an elongated cross-sectional profile perpendicular to the axis 18, having a first dimension and a second dimension. In particular, the first dimension is longer than the second dimension. In an embodiment, the ion channel 12 has the following dimensions: along the longitudinal direction (z) along the axis 18, the ion channel 12 has a dimension of approximately 20 mm; in a first transverse direction (x) extending perpendicular to the longitudinal direction (z), the ion channel 12 has a dimension of 60 mm; and in a second transverse direction (y) also extending perpendicular to the longitudinal direction (z), the ion channel 12 has a dimension of 8 mm. This means that, in this embodiment, the extension of the ion channel 12 is much larger in one of the transverse directions than in the longitudinal direction, and the ions move along the longitudinal direction. In order to better spatially distribute the above-mentioned extension directions, in Figure 1a Draw the coordinate system in .

[0133] Next, the operation mode of the first embodiment of the trapping ion mobility separator 10 according to the present invention is described:

[0134] Ions are introduced into the ion channel 12. In particular, the ions are introduced into the ion channel 12 at the first end 14 (representing the inlet region 15) of the ion channel 12. Therefore, the ions are introduced (injected) into the ion channel 12 along the axis 18, along which they move between the first end 14 and the second end 16. In particular, this means that the ions are injected along the axis along which they will be separated. Subsequently, the ions are directed to the separation region 24. A first axial force applied to the ions along the axis 18 is generated by the first generator 30 by applying an alternating separation voltage to the first electrode 20 and the second electrode 22 to generate an alternating axial electric field. In this embodiment, in the first time interval, the generated alternating axial electric field is directed downstream in the separation region 24. In the second time interval, the generated alternating axial electric field is directed upstream in the separation region 24. Since the second time interval lasts longer than the first time interval, the generated alternating axial electric field generally generates a differential mobility drift directed upstream in the separation region 24, or in other words, generally, the ions experience a net displacement toward the first end 14 of the ion channel 12. This means that, in general, the first axial force causes the ions to move towards the first end 14 of the ion channel 12. Essentially at any time, in the separation region 24, the direction of the first axial force does not change along the axis 18. The potential of the first electrode 20 and the second electrode 22 is distributed to the additional electrode 26 via the resistor chain.

[0135] At the same time, by applying a compensation voltage to the first electrode 20 and the second electrode 22 to generate a compensation electric field, a second axial force is generated by the second generator 32 along the axis 18 that is applied to the ions and temporarily offsets the first axial force. In particular, in this embodiment, the second generator 32 applies a DC voltage to the first electrode 20 and the second electrode 22 to generate an axial direct current field (DC field). In this embodiment, the generated axial DC field is oriented downstream. This means that the generated axial DC field generates a downstream mobility drift (DC field drift), or in other words, the ion movement caused by the axial DC field is oriented toward the second end 16 of the ion channel 12. The compensation potential of the first electrode 20 and the second electrode 22 is distributed to the additional electrode 26 via a resistor chain.

[0136] At the same time, a radial confinement RF voltage is applied to the first electrode 20 , the second electrode 22 , and the additional electrode 26 for preventing ions from escaping laterally from the ion channel 12 .

[0137] The alternating separation voltage applied by the first generator 30 is applied so that for a first time interval, an electric field having a first field strength is generated, and for a second time interval after the first time interval, an opposite electric field having a second field strength is generated. Thus, the second field strength is lower in magnitude than the first field strength. The first time interval lasts for a shorter time span than the second time interval, so that the ions are trapped and separated along the axis 18 by a force balance of the first axial force and the second axial force.

[0138] In this embodiment, the first time interval corresponds to one third of one period of the alternating separation voltage and the second time interval corresponds to two thirds of one period of the alternating separation voltage. In particular, the first time interval lasts about 3.33 μs and the second time interval lasts about 6.66 μs.

[0139] In this embodiment, in the first time interval, the first generator 30 applies the alternating separation voltage so that the potential difference (voltage) between the first and second electrodes is 700 V. In the second time interval, the first generator 30 applies the alternating separation voltage so that the potential difference is -350 V. In particular, in the first time interval, a voltage of 350 V is applied to the first electrode 20, and a voltage of -350 V is applied to the second electrode 22. In particular, in the second time interval, a voltage of -175 V is applied to the first electrode 20, and a voltage of 175 V is applied to the second electrode 22.

[0140] In this embodiment, a rectangular voltage is applied as the separation voltage. In addition, in this embodiment, the applied alternating separation voltage has a frequency of 100 kHz. In this embodiment, the alternating axial electric field generated by the first generator 30 has an intensity of 200 Td, thus showing a ratio of electric field intensity to particle density, at which the ion mobility has a considerable nonlinear dependence on the electric field.

[0141] Thus, in this embodiment, the first axial force achieves ion motion related to the differential mobility of the ions, while the second axial force achieves ion motion related to the mobility of the ions. It should be mentioned at this point that, for example, a gas flow will cause ion motion that is independent of the mobility of the ions (or in other words, the speed of the ion motion caused by the gas flow is independent of the mobility of the ions).

[0142] At least one of the first axial force and the second axial force is changed over time by the electrical controller 34. In this embodiment, the first axial force or the second axial force is changed so that the second axial force increases relative to the first axial force. In this embodiment, the second axial force increases in several steps. By doing so, as a function of the differential mobility of the trapped ions, they are gradually driven to the second end 16 of the representative outlet region 17 of the ion channel 12. Therefore, the ions are eluted in the form of multiple fractions at the second end 16 of the ion channel 12, and each fraction includes a series of ion species with different differential mobilities.

[0143] In this embodiment, the trapping ion mobility separator 10 is operated at a gas pressure of 5 mbar.

[0144] Figure 2 A graph of the dispersion potential along the longitudinal direction (z) of the ion channel 12 is shown. The potential is related to the alternating separation voltage that causes the first axial force. For better overview, a geometric longitudinal cross-sectional view (yz view) of the ion channel 12 along the axis 18 is shown at the top of the graph, which starts at the first end 14 of the ion channel 12 and ends at the second end 16 of the ion channel 12, and presents the positions of the first electrode 20 and the second electrode 22 in the ion channel 12.

[0145] The dispersion potential (V) is shown on the ordinate, and the z coordinate (mm) is shown on the abscissa, which represents the extension of the ion channel 12 in the longitudinal direction. The solid line represents the potential (V) at the first electrode 20 and the second electrode 22 during the first time interval, and the dotted line represents the potential (V) at the first electrode 20 and the second electrode 22 during the second time interval. In fact, the second time interval is after the first time interval. However, since the potentials of the two time intervals are plotted simultaneously in the figure, or in other words, are independent of time, the unit of the ordinate is called "dispersion potential" instead of "potential".

[0146] As can be seen in the figure, in the first time interval (represented by the solid line), an electric field with a first field strength is generated, and for the second time interval (represented by the dotted line), an opposite electric field with a second field strength is generated, which is lower in magnitude than the first field strength. In particular, in this embodiment, in the first time interval, a voltage of 350V is applied to the first electrode 20, and a voltage of -350V is applied to the second electrode 22, and in the second time interval, a voltage of -175V is applied to the first electrode 20, and a voltage of 175V is applied to the second electrode 22.

[0147] Furthermore, as can be seen in the figure, in the first time interval (represented by the solid line), an electric field is generated, which is directed downstream in the separation region 24, and is directed upstream in the inlet region 15 and in the outlet region 17. In the second time interval (represented by the dotted line), an electric field is generated, which is directed upstream in the separation region 24, and is directed downstream in the inlet region 15 and in the outlet region 17.

[0148] Figure 3 A graph of a reduced dispersion field along the longitudinal direction (z) of ion channel 12 is shown. In principle, the dispersion field is the spatial derivative of the dispersion potential. In the context of the present disclosure, the term "dispersion field" should represent the above-mentioned alternating axial electric field. Therefore, the reduced dispersion field corresponds to the first axial force. Again, for better overview, a geometric longitudinal cross-sectional view (yz view) of ion channel 12 along axis 18 is shown at the top of the graph, which starts at the first end 14 of ion channel 12 and ends at the second end 16 of ion channel 12, and presents the positions of the first electrode 20 and the second electrode 22 at the ion channel 12.

[0149] The ordinate represents the reduced dispersion field (Td), and the abscissa represents the z coordinate (mm), which represents the extension of the ion channel 12 in the longitudinal direction. The alternating separation voltage applied to the first electrode 20 and the second electrode 22 generates a dispersion field Ed during the first time interval and the second time interval. The reduced dispersion field (Td) describes the ratio of electric field intensity and particle density. The solid line represents the reduced dispersion field (Td) during the first time interval, and the dotted line represents the reduced dispersion field (Td) during the second time interval. In fact, the second time interval is after the first time interval. However, since the reduced field applied for two time intervals is drawn in the figure at the same time, or in other words, it is independent of time, the unit of the ordinate is called "reduced dispersion field", rather than "reduced field". In addition, the mobility drift of the ions caused by the alternating electric field is shown in the figure.

[0150] As can be seen in the figure, the time-dependent dispersion field causes different differential mobility drifts (indicated by arrows) in the separation region 24 of the ion channel 12 and in the inlet region 15 or the outlet region 17 of the ion channel 12. The differential mobility drift in the separation region 24 points upstream. The differential drift in the inlet region 15 and the outlet region 17 points downstream.

[0151] The differential mobility drift velocity depends on the strength of the dispersion field Ed in a nonlinear manner. In the transition between the entrance region 15 of the ion channel 12 and the separation region 24 of the ion channel, the differential mobility drift velocity exhibits a gradient, which is used for spatial separation and trapping of ions. The dispersion field Ed is spatially constant in the middle of the separation region 24 of the ion channel 12, which forms a platform region of a "differential mobility barrier". From the first electrode 20 to the platform region between the first electrode 20 and the second electrode 22, the first axial force (dispersion field, differential mobility drift velocity) rises ( Figure 3 The second force (compensation field) is spatially uniform between the first electrode 20 and the second electrode 22 ( Figure 6 ). The differential mobility drift and the DC drift cause the ions to move towards the first electrode 20. One ion species is trapped at a location downstream of the first electrode 20 where the differential mobility drift velocity is equal to the DC field drift velocity.

[0152] Figure 4a (Left) shows Figure 2 FIG. 4 is a time curve diagram of the dispersion potential present at the first electrode 20. Figure 4b (right) shows Figure 2 FIG. 1 is a time curve diagram of the dispersion potential present at the second electrode 22. FIG.

[0153] exist Figure 4a In (left), the ordinate shows the dispersion potential (V) at the first electrode 20, and the abscissa shows the time (s). The first electrode 20 is assigned to the first end 14 of the ion channel 12, which represents the entrance area of ​​ions. Figure 4b In (right), the ordinate shows the dispersion potential (V) at the second electrode 22, and the abscissa shows the time (s). The second electrode 22 is assigned to the second end 16 of the ion channel 12, which represents the exit region of ions.

[0154] As shown, a rectangular voltage is applied to both the first electrode 20 and the second electrode 22. The solid line corresponds to one cycle of the alternating separation voltage. The dotted line corresponds to another cycle of the alternating separation voltage. The maximum potential at the first electrode 20 is about 350V. The minimum potential at the second electrode 22 is about -350V. In this embodiment, the applied alternating separation voltage has a frequency of 100kHz.

[0155] Figure 5A graph of the compensation potential along the longitudinal direction (z) of the ion channel 12 is shown. The potential is related to the compensation voltage that causes the second axial force. Again, for better overview, a geometric longitudinal cross-sectional view (yz view) of the ion channel 12 along the axis 18 is shown at the top of the graph, which starts at the first end 14 of the ion channel 12 and ends at the second end 16 of the ion channel 12, and presents the positions of the first electrode 20 and the second electrode 22 at the ion channel 12.

[0156] On the ordinate the compensation potential (V) is shown, and on the abscissa the z-coordinate (mm) is shown, which represents the extension in the longitudinal direction of the ion channel 12. In this embodiment, the compensation potential generates an axial direct current field.

[0157] As can be seen in the figure, an axial DC field is generated which is directed downstream over the entire length (z direction) of the ion channel 12 (including the separation region 24 and the inlet and outlet regions 15, 17).

[0158] Figure 6 A graph of a normalized compensation field along the longitudinal direction (z) of the ion channel 12 is shown. The normalized compensation field corresponds to a second axial force. Again, for better overview, a geometric longitudinal cross-sectional view (yz view) of the ion channel 12 along the axis 18 is shown at the top of the graph, which starts at the first end 14 of the ion channel 12 and ends at the second end 16 of the ion channel 12, and presents the positions of the first electrode 20 and the second electrode 22 at the ion channel 12.

[0159] The normalized reduced compensation field (Td) is shown on the ordinate, and the z coordinate (mm) is shown on the abscissa, which represents the extension of the ion channel 12 in the longitudinal direction. The compensation voltage applied to the first electrode 20 and the second electrode 22 generates the compensation field Ec. The reduced compensation field (Td) describes the ratio of the electric compensation field strength to the particle density. Here, the reduced dispersion field is normalized to 1Td. In this embodiment, the normalized reduced compensation field (Td) is the normalized reduced axial DC field.

[0160] As can be seen in the figure, the compensation field or the normalized reduced compensation field is spatially constant. In addition, the compensation field or the normalized reduced compensation field generates a downstream axial DC field drift (indicated by the arrow). This axial DC field drift cancels the upstream differential mobility drift ( Figure 3 ).

[0161] Figure 7a Simulation results are shown summarizing the number of ions at different elution times depending on the charge state Z of the ions. Figure 7b Simulation results are shown summarizing the probability of ion elution at different elution times depending on the charge state Z of the ion.

[0162] In the simulation, the motion of peptide ion species was calculated based on the data published in the ASMS poster (2013 Ridgeway et al., ASMS Mass Spectrometry Conference and Joint Theme: "Maximizing Gas Phase Peak Capacity While Minimizing Analyses Time Through"). The dispersion field ENd and compensation field ENc described above (as shown in Figures 1 to 2) were used. Figure 6 The simulation was performed as described above, while the compensation field ENc was increased in small steps during the scan time. The compensation field ENc was scanned from 1.8 Td to 5.0 Td in 250 ms. The data included low-field and high-field mobilities of 62 BSA digested peptides.

[0163] As shown in Figures (7a, 7b), ion species with charge state Z = 1 are eluted primarily in preference to ion species with higher charge states. Therefore, ion species with Z = 1 can be separated and eliminated from ion species with Z > 1 using dTIMS. The portion of ion species eluted before 100 ms includes 80% of ion species with Z = 1, but only 12% of ion species with Z > 1.

[0164] Figure 8a (Left) shows the simulation results summarizing the mobility of ions according to their charge state Z over elution time. Figure 8b (Right) shows the simulation results summarizing the differential mobility of ions according to their charge state Z over elution time.

[0165] The data provided here supplement Figure 7a , Figure 7b The simulation results are shown in . Figure 8a , Figure 8b As shown, there is no correlation between elution time and low field mobility, but there is a clear correlation between elution time and differential mobility (first nonlinear coefficient). This result shows that dTIMS adds an additional separation dimension compared to a trapped ion mobility separator that is constructed and operated to disperse ions according to ion mobility, preferably in the low field limit.

[0166] Fig. 9 A schematic perspective view of a second embodiment of a trapped ion mobility separator 36 according to the present invention is shown. The trapped ion mobility separator 36 is a differential trapped ion mobility separator (dTIMS). The trapped ion mobility separator 36 corresponds substantially to Figure 1a The invention relates to a trapped ion mobility separator 10 in FIG. Identical elements have the same reference numerals. In this respect, reference is also made to the previous description.

[0167] The trapped ion mobility separator 36 and Figure 1a The difference between the trapped ion mobility separator 10 in FIG. 1 is that the trapped ion mobility separator 36 includes an ion trap 38. The ion trap 38 is located upstream of the separation region 24 in the ion channel 12. In particular, the ion trap 38 is located upstream of the entrance region of the separation region 24 in the ion channel 12. The ion trap 38 is configured to store ions. In particular, a batch of ions can be accumulated in the ion trap 38 while another batch of ions is being separated in the separation region 24. The ion trap 38 has a first end 40. In addition, the ion trap 38 has a second end 42, which is away from the first end 40 and faces the entrance region 15 of the separation region 24.

[0168] In addition, the trapped ion mobility separator 36 includes a transfer region 44. The transfer region 44 is located at the second end 42 of the ion trap 38. In particular, the transfer region 44 is located between the ion trap 38 and the entrance region 15 of the separation region 24. The transfer region 44 provides a connection between the ion trap 38 and the separation region 24. In particular, the transfer region 44 is configured to transfer ions from the ion trap 38 to the separation region 24. The transfer region 44 is shaped to be tapered. Due to this tapering shape of the transfer region 44, the influence of the strong electric field of the trapped ion mobility separator 36 on the ion trap 38 located upstream is minimized.

[0169] Similar to the trapped ion mobility separator 10, the first generator causes a first axial force by applying the above-mentioned alternating separation voltage to the first electrode and the second electrode to generate the above-mentioned alternating axial electric field. The second axial force that temporarily offsets the first axial force is caused by the second generator by applying a DC voltage to the first electrode and the second electrode to generate an axial direct current field (DC field). In the trapped ion mobility separator 36, the first axial force includes a spatial gradient along the longitudinal direction (z). The second axial force is constant at the gradient of the first axial force.

[0170] In the longitudinal direction (z), the ion channel 12 of the trapping ion mobility separator 36 has a dimension of 40 mm. Figure 1a Compared to the trapped ion mobility separator 10 in FIG. 1 , this extension of size is caused by the additional, upstream ion trap 38. In a first transverse direction (x), the ion channel 12 has a dimension of 60 mm, and in a second transverse direction (y), the ion channel 12 has a dimension of 8 mm.

[0171] In this embodiment, a rectangular voltage is applied as the separation voltage. In addition, in this embodiment, the applied alternating separation voltage has a frequency of 100 kHz. The alternating axial electric field generated by the first generator 30 has a maximum strength of 200 Td. In this embodiment, the trapped ion mobility separator 36 is operated at a gas pressure of 5 mbar.

[0172] For a better overview, Fig. 9 Not shown are the second end 16 representing the exit region 17 for ions, the first electrode 20, the second electrode 22 and the additional electrode 26.

[0173] FIG. 10 schematically shows the working principle of the second embodiment of the trapping ion mobility separator 36 according to the present invention at different time points during the analysis process ( Fig.10a , 10b , 10c). On the left side of the corresponding figure, the position and distribution of ions in the ion channel are schematically shown for the corresponding time points; on the right side (top), the reduced dispersion field Ed (first axial force) generated along the longitudinal direction (z) of the separation region 24 is shown for the corresponding time points; on the right side (bottom), the compensation field Ec (second axial force) generated along the longitudinal direction (z) of the separation region 24 is shown for the corresponding time points.

[0174] The reduced scattered field Ed generated in the longitudinal direction (z) of the separation region 24 shown on the right (top) is only for overview, since the alternating axial electric field only changes as already indicated by the two lines of “scattered field”.

[0175] Fig.10a Relates to the first selected time point. Fig.10a As shown on the left, ions 200 (schematically represented as circles; for better overview, only one ion 200 has a reference number) are trapped and distributed in the ion trap 38, which is located upstream of the separation region 24 within the ion channel 12 of the trapped ion mobility separator 36. The ions 200 are trapped in the ion trap 38 by applying a DC voltage to the inlet and outlet of the ion trap 38. Fig.10a As shown on the right, the resulting compensation field Ec is at its maximum level.

[0176] Fig.10b relates to a second selected time point. Fig.10b As shown on the left, ions 200 (only one ion 200 has a reference mark for better overview) are transferred from the ion trap 38 to the separation region 24, which is located downstream of the ion trap 38 within the ion channel 12 of the trapped ion mobility separator 36. The ions 200 are transferred by switching the DC field in the ion trap 38. The downstream differential drift in the transfer region 44 assists the transfer of the ions 200. The ions 200 are trapped and separated in the separation region 24 according to their differential mobility. Fig.10b As shown on the right, the resulting compensation field Ec is at its lowest level.

[0177] Fig.10c relates to a third selected time point. Fig.10cAs shown on the left, new ions 200 (only one ion 200 has a reference mark for better overview) are trapped and distributed in the ion trap 38 of the trapped ion mobility separator 36. By gradually (or continuously) increasing the compensation field Ec to its maximum value, as Fig.10c As shown on the right, previously transferred ions 200 are ejected from the separation region 24 and across the trapped ion mobility separator 36 according to their differential mobility.

[0178] Fig.11a FIG. 4 is a schematic longitudinal cross-sectional view showing a third embodiment of a trapping ion mobility separator 46 according to the present invention, Fig.11b A schematic perspective view of a third embodiment of a trapped ion mobility separator is shown. The trapped ion mobility separator 46 is a differential trapped ion mobility separator (dTIMS). The trapped ion mobility separator 46 corresponds essentially to the trapped ion mobility separator 36 in terms of its structure and mode of operation. Identical elements have the same reference numerals. In this respect, reference is also made to the previous description. Fig.11b In the view of FIG. 5 , a portion of the ion channel is omitted so that the interior 54 of the trapped ion mobility separator 46 can be seen. For better understanding, the transparent Fig.11b .

[0179] The trapped ion mobility separator 46 and Fig. 9 The difference between the trapped ion mobility separator 36 in is that the ion channel 48 of the trapped ion mobility separator 46 has a circular cross-sectional profile along the axis 18. In this embodiment, the diameter of the ion channel 48 is 50 mm. The ion channel 48 has an outer wall 50. The outer wall 50 represents the outer radius of the ion channel 48. In addition, the ion channel 48 has an inner wall 52. The inner wall 52 represents the inner radius of the ion channel 48. Between the outer radius and the inner radius, a gap is provided. The gap constitutes a ring, which is the difference between the outer radius and the inner radius. The ring has a size of 8 mm, which represents the thickness of the ring. The ions are radially confined within the ring. Figure 1a The trapped ion mobility separator 10 and Fig. 9 By confining the ions within the ring, the trapped ion mobility separator 46 has an increased charge capacity compared to the already high charge capacity provided by the trapped ion mobility separator 36, as they extend in one of the transverse directions of the ion channel 12. In the longitudinal direction (z), the ion channel 48 has a dimension of 30 mm. A vacuum is maintained in the interior 54 of the inner wall 52.

[0180] The trapped ion mobility separator 46 includes an ion trap 38 within an ion channel 48, which is arranged in a manner similar to Fig. 9The ion trap 38 of the ion mobility separator 36 is captured in the ion trap 38. The ion trap 38 has a first end 40. In addition, the ion trap 38 has a second end 42, which is away from the first end 40 and faces the entrance region 15 of the separation region 24. The ion mobility separator 46 includes a transfer region 44. The transfer region 44 is located at the second end 42. The gap of the ion channel 48 is reduced in the transfer region 44 / entrance region 15. The above-mentioned elements have the same Fig. 9 The same reference numerals are used for the embodiments of the trapped ion mobility separator 36 in FIG. 1 because they correspond substantially in terms of the mode of operation to the corresponding elements of the trapped ion mobility separator 36. However, it is obvious to a person skilled in the art that they are adjusted in shape to match the shape of the ion channel 48 and the ring.

[0181] In addition, the trapped ion mobility separator 46 is different from the trapped ion mobility separator 36 in that it includes a funnel 56. In particular, the funnel 56 is an inlet funnel, constituting an inlet region for ions. The funnel 56 is located at the first end 40 of the ion trap 38. The shape of the funnel 56 is tapered.

[0182] and Fig. 9 Compared to the trapped ion mobility separator 36 of FIG. 4 , in the trapped ion mobility separator 46 , the first axial force comprises a spatial gradient in the longitudinal direction (z). The second axial force is constant at the gradient of the first axial force.

[0183] In this embodiment, a rectangular voltage is applied as the separation voltage. In addition, in this embodiment, the separation voltage applied has a frequency of 100 kHz. The alternating axial electric field generated by the first generator 30 has a maximum strength of 200 Td. In this embodiment, the trapped ion mobility separator 46 operates at a gas pressure of 5 mbar.

[0184] For a clearer overview, the first electrode 20, the second electrode 22 and the additional electrode 26 are not shown in FIG11. However, the shapes of the first electrode 20, the second electrode 22 and the additional electrode 26 are adapted to the circular cross-sectional profile of the ion channel 48.

[0185] Fig.12 A schematic perspective view of a fourth embodiment of a trapped ion mobility separator 58 according to the present invention is shown. The trapped ion mobility separator 58 is a differential trapped ion mobility separator (dTIMS). The trapped ion mobility separator 58 corresponds substantially to the Figure 1a The invention relates to a trapped ion mobility separator 10. Identical elements have the same reference numerals. In this respect, reference is also made to the previous description.

[0186] The trapped ion mobility separator 58 shown in the embodiment is preferably used to produce a small number of ion fractions, one of which consists essentially of ion species of the charge level Z=1.

[0187] The trapped ion mobility separator 58 and Figure 1a The difference between the trapped ion mobility separator 10 in FIG. 5 is that the inlet region for ions and the outlet region for ions are not allocated to two different ends and sides of the separation region in the trapped ion mobility separator 58. Instead, ions are injected and eluted on the same side of the separation region 60. This allows the separation region 60 to be bypassed in the transmission mode.

[0188] The separation region 60 has a first end 62. The separation region 60 also has a second end 64. The second end 64 of the separation region 60 is designed to be closed. The trapped ion mobility separator 58 includes an ion channel 66. The ion channel 66 includes the separation region 60. The ion channel 66 also includes a transfer region 68. The transfer region 68 is located at the first end 62 of the separation region 60. In addition, the trapped ion mobility separator 58 includes a funnel 70. The funnel 70 constitutes an inlet funnel for the ions. The funnel 70 is arranged adjacent to the transfer region 68. Therefore, the funnel 70 is arranged non-collinearly with the ion channel 66. In particular, the axis 72 ( Fig.13a ) and the axis 18 of the ion channel is substantially 90° ( Fig.13a exemplarily shown in FIG.

[0189] and Figure 1a The trapped ion mobility separator 10 is different from (and different from Fig. 9 The trapped ion mobility separator 36 and Fig.11a Unlike the trapped ion mobility separator 46, in the trapped ion mobility separator 58, the second axial force generated includes a spatial gradient in the longitudinal direction (z). The first axial force is constant at the gradient of the second axial force. In order to better spatially distribute the above directions, Fig.12 Draw the coordinate system in .

[0190] In this embodiment, a double sinusoidal voltage is applied as the separation voltage. In addition, in this embodiment, the separation voltage applied has a frequency of 100 kHz. The alternating axial electric field generated by the first generator 30 has a maximum strength of 200 Td. In this embodiment, the trapped ion mobility separator 58 operates at a gas pressure of 2.5 mbar.

[0191] For a better overview, in the Fig.12 The first electrode 20, the second electrode 22 and the additional electrode 26 are not shown.

[0192] In an alternative embodiment, the transition region 68 can be designed and operated as a low field mobility filter, where the first axial force is preferably the gas flow toward the transition region outlet, and the second force is the DC field barrier. This alternative embodiment constructs a tandem differential TIMS / TIMS device.

[0193] FIG. 13 schematically shows the different time points during the analysis ( Fig.13a , Fig.13b , Fig.13c , Fig.13d , Fig.13e ) A fourth embodiment of the trapping ion mobility separator according to the present invention ( Fig.12 ) working principle. On the left side of the corresponding figure, the ion position and distribution in the ion channel 66 at the corresponding time point are schematically shown; on the right side (top), the transfer field Ez generated along the longitudinal z direction of the ion channel 66 at the corresponding time point is shown; on the right side (middle), the reduced dispersion field Ed (first axial force) generated along the longitudinal z direction of the ion channel 66 at the corresponding time point is shown; on the right side (bottom), the compensation field Ec (second axial force) generated along the longitudinal z direction of the ion channel 66 at the corresponding time point is shown. The dotted lines on the right side of the figure represent different regions in the trapped ion mobility separator 58, namely the transfer region 68 and the separation region 60.

[0194] The transfer field Ez is configured to transfer ions from the transfer region 68 to the separation region 60. Therefore, the transfer field Ez is oriented along the z direction of the trapped ion mobility separator. Additionally, a transfer field Ex is generated, which is not shown on the right side of the figure. The additional transfer field Ex is configured to transfer ions, especially eluted ions from the separation region 60, to a component / device (not shown) located downstream. Therefore, the transfer field Ex is oriented along the x direction of the trapped ion mobility separator. In this embodiment, the transfer field Ex generated is a DC field. In addition, an RF limiting voltage (yz direction) is applied.

[0195] Fig.13a relates to a first selected point in time, in particular, Fig.13a Indicates the "transmission phase". Fig.13a As shown on the left, ions 200 (schematically represented as circles; for better overview, only one ion 200 has a reference number) flow through the inlet funnel 70 into the transfer region 68. The transfer field Ex is turned on to transfer the ions to components / devices located downstream (not shown in the figure). Fig.13a As shown on the right, the transfer field Ez is turned off to confine the ions 200 in the transfer region 68. The dispersion field Ed and the compensation field Ec used to separate the ions in the separation region 60 are also turned off because no ions are present in the separation region 60.

[0196] Fig.13b relates to a second selected point in time, in particular, Fig.13b Indicates the "injection phase". Fig.13b As shown on the left, further ions 200 (for a better overview, only one ion 200 has a reference number) flow through the inlet funnel 70 into the transfer region 68. At the same time, the ions 200 are transferred from the transfer region 68 into the separation region 60. Fig.13b As shown on the right, the transfer field Ez is turned on to transfer the ions 200 into the separation region 60. Since the ions 200 have just entered the separation region 60, the dispersion field Ed and the compensation field Ec for separating the ions in the separation region 60 are still turned off. In addition, a DC confinement field is generated at the exit of the separation region 60.

[0197] Fig.13c relates to a third selected point in time, in particular, Fig.13c Indicates "space separation stage". Fig.13c As can be seen in FIG. 1 , the inflow of ions through the inlet funnel 70 into the transfer region 68 is stopped. The ions 200 (only one ion 200 has a reference number for a better overview) are separated and trapped in the separation region 60. The transfer field Ex is switched on for transferring the ions 200 eluted from the separation region 60 to components / devices located downstream (not shown in the figure). Fig.13b As shown on the right, the transfer field Ez is turned off. The dispersion field is turned on, causing a differential mobility drift of the ions 200 toward the first end 62 of the separation region 60. The compensation field is turned on and is at a maximum level. Fig.12 As described, in this embodiment, the compensation field (representing a counteracting second axial force) includes a spatial gradient along the longitudinal direction (z) that extends into the plateau where the force is spatially constant. Due to this spatial variation, there are mobility-dependent positions along the axis where the net drift of the two opposite drifts vanishes and ions 200 separated according to their differential mobility are trapped along the axis.

[0198] Fig.13d Relating to a fourth selected point in time, in particular, Fig.13d Indicates the "elution phase". Fig.13d As shown, the ions 200 (for a better overview, only one ion 200 has a reference number) are still separated and trapped in the separation region 60, however, they move in a controlled manner towards the first end 62 of the separation region 60. Fig.13bAs shown on the right, the transfer field Ez is still off. The dispersion field is turned on, still causing a differential mobility drift of the ions 200 towards the first end 62 of the separation region 60. The compensation field is turned on, but at a reduced level to allow the separated ions 200 to move towards the first end 62 of the separation region 60.

[0199] Fig.13e relates to a fifth selected point in time, in particular, Fig.13e Indicates "transfer phase". Fig.13e As shown, separated ions 200 (for a better overview, only one ion 200 has a reference number) are eluted from the separation region 60 and enter the transfer region 68. The transfer field Ex is turned on to transfer the ions 200 eluted from the separation region 60 to components / devices located downstream (not shown in the figure). Fig.13b As shown on the right, the transfer field Ez is still off. The dispersion field is switched on, still causing a differential mobility shift of the ions 200. The compensation field is switched on, but at a further reduced level, to allow the separated ions 200 to eventually move back into the transfer region 68.

[0200] Fig.14 A time curve diagram showing the dispersion potential applied to the second electrode 22 is shown in FIG. Fig.12 The ordinate represents the dispersion potential (V) at the second electrode 22, and the abscissa represents the time (s). The second electrode 22 is assigned to the second end 64 of the ion channel 66.

[0201] As shown in the figure, a double sinusoidal voltage is applied to the second electrode 22. The maximum potential at the second electrode 22 is about 350V. The minimum potential at the second electrode 22 is about -175V. In this embodiment, the frequency of the applied alternating separation voltage is 100kHz. The first electrode 20 assigned to the first end 62 of the ion channel 66 has a potential of 0V, or in other words, the first electrode 20 is maintained at ground potential.

[0202] Fig.15 A schematic diagram of a mass spectrometry system 100 according to the present invention is shown. The mass spectrometry system 100 is used to analyze ions. The mass spectrometry system 100 includes a plurality of analysis devices, which will be described below.

[0203] The mass spectrometry system 100 includes a separation device (not shown) for separating a mixture of substances. In this embodiment, the separation device is a liquid chromatography device. Other separation devices (not shown) such as electrophoresis devices can be provided and can be coupled to the mass spectrometry system 100.

[0204] In addition, mass spectrometry system 100 includes ion generator 110. Ion generator 110 includes ion source 112. In this embodiment, ion source 112 is an electrospray ion source (ESI). Ion source 112 operates at atmospheric pressure. Other ion source types that can be used include, for example, 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 gas discharge ionization. In addition, ion generator 110 includes ion source chamber 114. Ion source chamber 114 remains at atmospheric pressure. In particular, ion source chamber 114 is combined with ion source 112. Ion generator 110 is located at the downstream of liquid chromatography device. In addition, transfer capillary 116 is provided. Transfer capillary 116 has a first end 118. The first end 118 of transfer capillary 116 is connected with ion source chamber 114. In addition, the transfer capillary 116 has a second end 120. The second end 120 of the transfer capillary 116 is connected to the vacuum chamber 124 of the first trapped ion mobility separator 122. In particular, the transfer capillary 116 is configured to introduce ions generated by the (ESI) ion source 112 into the vacuum chamber 124. In this embodiment, the transfer capillary 116 is a short wide bore capillary having an inner diameter of 1 mm or more and a length of 180 mm or less. Optionally, multiple capillaries or single / multiple aperture inlets can be used to transfer ions from the ion source chamber 114 to the vacuum chamber 124.

[0205] Furthermore, the mass spectrometry system 100 comprises a first trapped ion mobility separator 122. In this embodiment, the first trapped ion mobility separator is a differential trapped ion mobility separator (dTIMS) 122 according to the present invention. In particular, in this embodiment, the first trapped ion mobility separator 122 corresponds to Fig.11aThe trapped ion mobility separator 46 in the embodiment has a circular cross-sectional profile along the axis 18. In this regard, reference is also made to the previous description. The trapped ion mobility separator 122 is located downstream of the ion generator 110. The trapped ion mobility separator 122 includes a vacuum chamber 124. In this embodiment, the vacuum chamber 124 is maintained at an elevated pressure between 300Pa and 3000Pa. In another preferred embodiment, it is conceivable that the vacuum chamber includes an additional sub-ambient ESI ion source. In addition, the trapped ion mobility separator 122 includes a deflection electrode 126. It is conceivable that in another preferred embodiment, an additional MALDI source (not shown in the figure) can be set at the position of the deflection electrode. In addition, the trapped ion mobility separator 122 includes an inlet funnel 128. In particular, the inlet funnel 128 is an RF inlet funnel. In addition, the trapped ion mobility separator 122 includes an ion trap 130. The ion trap 130 is configured to trap ions, while a separation region 134 located downstream is operated to produce a plurality of fractions (e.g., 2 to 10 fractions) of ions, each fraction comprising a series of differential mobilities. In addition, the trapped ion mobility separator 122 includes a transfer region 132. The transfer region 132 is configured to transfer ions from the ion trap 130 to the separation region 134. In addition, the trapped ion mobility separator 122 includes a separation region 134. The separation region 134 is configured to separate ions. In addition, the trapped ion mobility separator 122 includes an outlet funnel 136. In this embodiment, the trapped ion mobility separator 122 operates at a pressure of 5 mbar. In addition, an inter-chamber orifice 138 is provided. Through the inter-chamber orifice 138, ions can be transferred from the vacuum chamber 124 to the vacuum chamber 142 of the second trapped ion mobility separator 140.

[0206] In addition, the mass spectrometry system 100 includes a second trapped ion mobility separator 140. In this embodiment, the second trapped ion mobility separator is a TIMS140, which is constructed and operated to disperse ions according to ion mobility, preferably within the low field limit (hereinafter referred to as traditional TIMS140). Alternatively, a dTIMS can be provided as a second trapped ion mobility separator. Traditional TIMS140 is constructed and operated to separate ions according to the mobility of ions. Traditional TIMS140 is located downstream of the differential trapped ion mobility separator 122. Traditional TIMS140 includes a vacuum chamber 142. In this embodiment, the vacuum chamber 142 is maintained at a pressure lower than the pressure of the upstream vacuum chamber 124, for example, at a pressure between 100Pa and 300Pa. In addition, the traditional TIMS140 includes a deflection electrode 144. In addition, the traditional TIMS140 includes an inlet funnel 146. In particular, the inlet funnel 146 is an RF inlet funnel. Furthermore, the conventional TIMS 140 includes a separation region 148. The separation region 148 is configured to separate ions.

[0207] Furthermore, in this embodiment, an additional ion trap (not shown) is located between the dTIMS 122 and the conventional TIMS 140. The additional ion trap may have the same storage capacity as the conventional TIMS 140.

[0208] In addition, the mass spectrometry system 100 includes an ion guide device 150. The ion guide device 150 is configured to guide ions. The ion guide device 150 is located downstream of the conventional TIMS 140. The ion guide device 150 includes an RF ion guide 152. In addition, the ion guide device 150 includes an ion guide chamber 154. The ion guide chamber 154 includes the RF ion guide 152. The ion guide chamber 154 serves as a pressure level between the medium vacuum and the high vacuum of the conventional TIMS 140, and a mass filter device 156 located downstream is operated under the high vacuum.

[0209] In addition, the mass spectrometry system 100 includes a mass filter device 156. The mass filter device 156 is configured to guide or select ions based on mass. The mass filter device 156 is located downstream of the ion guide device 150. The mass filter device 156 includes a mass filter 158. In this embodiment, the mass filter 158 is a quadrupole mass filter. In addition, the mass filter device 156 includes a mass filter chamber 160. The mass filter chamber 160 accommodates the quadrupole mass filter 158.

[0210] In addition, the mass spectrometry system 100 includes a fragmentation unit 162. The fragmentation unit 162 is configured to fragment larger ions to allow mass spectrometry of ion fragments. The fragmentation unit 162 is located downstream of the mass filter device 156. In this embodiment, collision induced dissociation (CID) is used for fragmentation. However, any other known type of fragmentation mode may also be used, including but not limited to infrared multiphoton dissociation (IRMPD) or ultraviolet light dissociation (UVPD), 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 fragmentation by reaction with highly excited or free radical neutral particles. The fragmentation unit 162 includes an electrode 164. In addition, the fragmentation unit 162 includes a fragmentation unit chamber 166. The fragmentation unit chamber 166 accommodates these electrodes 164. Fragmentation by CID can be switched on and off, controlled by instrument parameters such as the axial acceleration voltage.Precursor ions can be trapped in the fragmentation cell 162 without being fragmented, and fragment ions when fragmentation is enabled.

[0211] In addition, the mass spectrometry system 100 includes a mass analyzer 168. In this embodiment, the mass analyzer 168 is a time-of-flight analyzer (OTOF-MS) with orthogonal ion injection. Other possible mass analyzers include electrostatic ion traps, RF ion traps, ion cyclotron frequency ion traps, and quadrupole mass filters. The mass analyzer 168 is configured to analyze ions according to mass. The mass analyzer 168 is located downstream of the fragmentation unit 162. The mass analyzer 168 includes an accelerator 170 (or a pulse generator). In addition, the mass analyzer 168 includes a flight tube 172. In this embodiment, the flight tube 172 is field-free. In addition, the mass analyzer 168 includes a reflector 174. In addition, the mass analyzer 168 includes an ion detector 176. An additional reflector can be located between the accelerator 170 and the ion detector 176 so that the ions are reflected twice in the reflector 174 and move on a W-shaped trajectory instead of a V-shaped trajectory.

[0212] The basic operation mode of the mass spectrometry system 100 according to the present invention is described below:

[0213] The sample material is eluted from a liquid chromatography device (not shown in the figure). Ions are generated by an (ESI) ion source 112 using the sample material eluted from the liquid chromatography device. The generated ions are introduced into the first vacuum chamber 124 of the first trapped ion mobility separator dTIMS122 through a transfer capillary 116. Subsequently, the ions are deflected into the RF inlet funnel 128 of the dTIMS122 by the repulsive DC potential applied to the deflection electrode 126 of the dTIMS122. The RF inlet funnel 128 collects the ions and guides them to the ion trap 130 of the dTIMS122. In this embodiment, the dTIMS122 operates in a parallel collection mode. This means that ions are accumulated in the ion trap 130 before being transferred to the separation region 134, while other ions are separated downstream in the separation region 134. During the accumulation phase, in the separation region 134 of the dTIMS122, the ions are separated and trapped by the force balance of the first axial force and the second axial force. During a subsequent elution phase, the fraction of trapped ions is gradually driven to the exit funnel 136 as a function of their differential mobility by stepwise varying at least one of the first axial force and the second axial force over time.

[0214] Subsequently, the ions of these fractions are transferred from the vacuum chamber 124 of the dTIMS 122 to the vacuum chamber 142 of the conventional TIMS 140 through the inter-chamber orifice 138. Then in the conventional TIMS 140, the transferred ions are deflected into the RF entrance funnel 146 by the deflection electrode 144. The RF entrance funnel 146 collects the ions and guides them to the separation region 148 of the conventional TIMS 140. In the separation region 148 of the conventional TIMS 140, the ions are separated according to their mobility. In this embodiment, the conventional TIMS 140 uses a gas flow and a DC field barrier as two reaction forces. By extracting gas from the outlet of the conventional TIMS 140 through a suction port (not shown in the figure) and through an orifice (not shown in the figure) between the vacuum chamber 124 and the vacuum chamber 142, a gas flow in the conventional TIMS 140 is generated. In the accumulation phase, the two reaction forces are balanced so that for each ion species of interest, there is an equilibrium point of zero velocity in the conventional TIMS 140. In the subsequent elution stage, by continuously changing the DC field gradient, the ion species in the traditional TIMS140 are sequentially eluted according to their mobility K, and the trapped ion species are finally released from the traditional TIMS140. This relative change in the opposite axial force can be gradual, so that the ion species with increasing mobility K leave the traditional TIMS140 in sequence. In this embodiment, dTIMS122 and traditional TIMS140 are operated in parallel. This means that dTIMS122 produces multiple fractions, each of which is separated separately in the traditional TIMS140 located downstream, and then the next fraction is transferred to the traditional TIMS140.

[0215] Subsequently, the ions released from the conventional TIMS 140 enter the ion guide chamber 154 of the ion guide device 150, which is located downstream. The RF ion guide 152 guides the ions into the mass filter chamber 160 of the mass filter device 156, which is located further downstream, and the mass filter 158 is located therein. In the mass filter 158, the ions are guided or selected according to mass. Subsequently, the ions passing through the mass filter 158 are directed to the fragmentation cell 162, which is located downstream of the mass filter device 156 in the fragmentation cell chamber 166. In the fragmentation cell 162, the larger ions are dissociated into fragment ions to allow mass spectrometry of the ion fragments. A DC voltage is applied to the electrodes 164 of the fragmentation cell 162 to generate an axial DC field for ejecting the ion fragments into the mass analyzer 168, which is located downstream, where they are analyzed according to their mass.

[0216] While one fraction of ion species is being analyzed in other components of the mass spectrometry system 100, the remaining ions can be trapped in the dTIMS 122. In this embodiment, since the dTIMS 122 includes an upstream ion trap 130, ions generated by the ion source 112 can be trapped until all fractions are transferred to the conventional TIMS 140. In this embodiment, the dTIMS 122 is operated to transfer N fractions to the conventional TIMS 140, so the storage capacity of the dTIMS 122 and its ion trap 130 located upstream of the separation region 134 for parallel accumulation is N times higher than the storage capacity of the conventional TIMS 140 located downstream. In this embodiment, one scan of the conventional TIMS 140 lasts for a time span of 50 ms, so the dTIMS 122 and its upstream ion trap 130 have N times the storage capacity for trapping ions generated by the ion source 112 for 50 ms. Typically, N is equal to five.

[0217] In the above-described embodiment of the mass spectrometry system 100, the components are nested coupled. In particular, the sequentially arranged dTIMS and conventional TIMS are nested coupled to form a dTIMS / TIMS device in series. Accordingly, the multiple fractions produced by the dTIMS 122 are then analyzed separately by the conventional TIMS 140. In addition, in this embodiment, the liquid chromatography device and the time-of-flight mass analyzer 168 are nested coupled to the dTIMS / TIMS device in series. This nested coupling allows the execution of parallel accumulation continuous fragmentation (PASEF), which in the context of the present disclosure may be referred to as differential parallel accumulation continuous fragmentation (dPASEF) because dTIMS is included. In such a nested coupled system, different separation devices operate at different time ranges, which provides the advantage that the individual separation techniques do not have to wait for each other. However, the subsequent analysis should be fast enough to reproduce the peaks determined by the previous method. Typically, a liquid chromatography device can be run at a separation time of 30 minutes; a dTIMS coupled to a liquid chromatography device typically runs at a separation time of 1 second; a TIMS coupled to a dTIMS typically runs at a separation time of 100 milliseconds; and finally, a time-of-flight mass analyzer coupled to a TIMS typically runs at a separation time of 200 microseconds. This means that a dTIMS can fractionate components eluted from a liquid chromatography device in 1 second, and 10 fractions of the dTIMS can be analyzed by the TIMS in 1 second. Thus, by adding the additional separation dimension provided by dTIMS to a mass spectrometry system, the peak capacity can be increased by a factor of 10, thus constituting a significant advantage.

[0218] A preferred application of tandem dTIMS / TIMS or variants thereof (such as tandem dTIMS / dTIMS) as part of a mass spectrometry system may be, for example, bottom-up proteomics. Here, it may be used in an advantageous manner to add the knowledge about differential mobility obtained from dTIMS as orthogonal information to the conventional mobility measurements performed by conventional TIMS. This may be used to further differentiate peptide ions.

[0219] Typically, in bottom-up proteomics, digested peptides are separated in a liquid chromatography device and then ionized in an electrospray ion source. Typically, a conventional ion mobility separator constructed and operated to disperse ions according to ion mobility is used to additionally separate the separated peptide ions in the gas phase. The separated peptide ions are further separated according to mass-to-charge ratio in a mass filter and then fragmented in a fragmentation unit. The mass spectrum of the fragment ions, as well as the mass spectrum of the possible precursor ions, are obtained and used to identify peptide ions and related proteins. However, the information content of the fragment mass spectrum of singly charged peptide ions is typically limited. In addition, other singly charged background ion species, together with singly charged peptide ions, may impair the performance of a mass spectrometry system, such as the performance of a conventional ion mobility separator, fragmentation unit, or mass analyzer. Therefore, eliminating singly charged background ions and singly charged peptide ions from analysis is very interesting, especially because these singly charged ion species typically account for a significant number of all ion species.

[0220] The above-described tandem dTIMS / TIMS can be used in an advantageous manner here, since dTIMS can substantially separate ion species according to their charge state. In a preferred embodiment, the dTIMS can be operated so that multiple fractions containing mainly ion species with a charge state Z>1 are transferred to a downstream conventional TIMS, while the fraction containing mainly ion species with a charge state Z=1 is not transferred but discarded. Alternatively, it is conceivable that a portion containing mainly ion species with a charge state Z=1 can be transferred separately to a downstream conventional TIMS for analysis. Subsequently, the ion species of each portion can be separated in a separate scan of the conventional TIMS and further processed in a downstream component of the mass spectrometry system. Therefore, one advantage of this tandem dTIMS / TIMS device is that the conventional TIMS will not be overloaded by singly charged ion species, whose fragment spectra have no or very little information but consume a considerable amount of storage capacity of the conventional TIMS. In this way, by reducing useless singly charged ion species, the performance of the conventional TIMS remains high.

[0221] The present invention has been shown and described above with reference to a number of different embodiments of the present invention. However, it will be appreciated by those skilled in the art that various aspects or details of the present invention may be varied, or various aspects or details of different embodiments may be arbitrarily combined, without departing from the scope of the present invention, if feasible. In general, the foregoing description is intended for illustrative purposes only and not for limiting purposes of the present invention, which is limited only by the appended claims, including any equivalent embodiments as the case may be.

[0222] Description of Reference Numerals

[0223] 10 Trapped Ion Mobility Separator

[0224] 12 Ion channels

[0225] 14 The first end of the ion channel

[0226] 15 Entrance Area

[0227] 16 The second end of the ion channel

[0228] 17 Exit Area

[0229] 18 Axis (of ion channel)

[0230] 20 First electrode

[0231] 22. Second electrode

[0232] 24 Separation Area

[0233] 26 Additional Electrodes

[0234] 30 First Generator

[0235] 32 Second Generator

[0236] 34 Electric controller

[0237] 36 Trapped Ion Mobility Separator

[0238] 38 Ion Trap

[0239] 40 First end of the ion trap

[0240] 42 Second end of the ion trap

[0241] 44 Transfer Area

[0242] 46 Trapped Ion Mobility Separator

[0243] 48 Ion Channels

[0244] 50 outer wall

[0245] 52 Inner wall

[0246] 54 Internal

[0247] 56 Funnel

[0248] 58 Trapped Ion Mobility Separator

[0249] 60 Separation Area

[0250] 62 First end of separation region

[0251] 64 Second end of separation region

[0252] 66 Ion Channels

[0253] 68 Transfer Area

[0254] 70 Funnel

[0255] 72 axis (funnel)

[0256] 100 Mass Spectrometry System

[0257] 110 Ion Generator

[0258] 112 Ion Source

[0259] 114 Ion source housing

[0260] 116 Transfer Capillary

[0261] 118 First end of transfer capillary

[0262] 120 Second end of transfer capillary

[0263] 122 Trapped Ion Mobility Separator

[0264] 124 Vacuum Chamber

[0265] 126 Deflection Electrode

[0266] 128 Entrance Funnel

[0267] 130 Ion Trap

[0268] 132 Transfer Area

[0269] 134 Separation Area

[0270] 136 Exit Funnel

[0271] 138 Interventricular orifice

[0272] 140 Trapped Ion Mobility Separator

[0273] 142 Vacuum Chamber

[0274] 144 Deflection Electrode

[0275] 146 Entrance Funnel

[0276] 148 Separation Area

[0277] 150 Ion guide equipment

[0278] 152 RF ion guide

[0279] 154 Ion Guide Chamber

[0280] 156 Quality Filtration Equipment

[0281] 158 Quality Filter

[0282] 160 Mass Filter Chamber

[0283] 162 Fragmentation Unit

[0284] 164 Electrodes

[0285] 166 Fragmentation Unit Chamber

[0286] 168 Mass Analyzer

[0287] 170 Accelerator

[0288] 172 Flight Tube

[0289] 174 Reflector

[0290] 176 Ion Detector

[0291] 200 Ions

[0292] X The first lateral extension direction of the ion channel

[0293] Y The second lateral extension direction of the ion channel

[0294] Z is the longitudinal extension direction of the ion channel.

Claims

1. A trapping ion mobility separator (10, 36, 46, 58, 122), comprising: An ion channel (12, 48, 66) in which ions move along an axis (18) between a first end (14, 62) of the ion channel (12, 48, 66) and a second end (16, 64) of the ion channel (12, 48, 66), at which the ions are introduced into the ion channel (12, 48, 66), the ion channel (12, 48, 66) containing a gas through which the ions pass, wherein the ion channel (12, 48, 66) is supplied with a radial confinement voltage for preventing ions from escaping laterally from the ion channel (12, 48, 66), at least a first electrode (20) and a second electrode (22) arranged to be spaced apart from each other along the axis (18) of the ion channel (12, 48, 66) to define an ion separation region (24, 60) therebetween, a first generator (30) which generates an alternating axial electric field by applying separate voltages to the first electrode (20) and the second electrode (22), the first generator causing a first axial force to be applied to the ions along the axis (18), the first axial force having an effect on the motion of the ions due to interaction with the gas, the motion of the ions being related to differential mobility, wherein the separation voltage is an alternating voltage and is applied so that for a first time interval, an electric field having a first field strength is generated, and for a second time interval after the first time interval, an opposite electric field having a second field strength is generated, the second field strength being lower in magnitude than the first field strength, the first time interval lasting a shorter time span than the second time interval, a second generator (32) causing a second axial force to be applied to the ions along the axis (18), the second axial force at least temporarily counteracting the first axial force, wherein the first generator (30) and the second generator (32) are configured such that at least one of the axial forces varies in strength along the axis (18) to trap ions at mobility-dependent locations along the axis (18) at which a force balance of the first axial force and the second axial force exists for the ions, The trapped ion mobility separator further comprises: An electrical controller (34) in communication with the first generator (30) and the second generator (32) to vary at least one of the first axial force and the second axial force over time so that the trapped ions are progressively driven to one of the first end (14, 62) and the second end (16, 64) of the ion channel (12, 48, 66) as a function of the differential mobility of the trapped ions.

2. The trapped ion mobility separator (10, 36, 46, 58, 122) according to claim 1, wherein: The separation voltage is a substantially rectangular voltage or a double sinusoidal voltage.

3. The trapped ion mobility separator (10, 36, 46, 58, 122) according to claim 1 or 2, wherein: The frequency of the separation voltage applied is 50 kHz to 2 MHz, preferably 80 kHz to 120 kHz, most preferably 100 kHz.

4. The trapped ion mobility separator (10, 36, 46, 58, 122) according to any one of claims 1 to 3, wherein: The alternating axial electric field generated by the first generator (30) has a maximum intensity of 20Td to 500Td, preferably a maximum intensity of 150Td to 250Td, most preferably a maximum intensity of 200Td.

5. The trapped ion mobility separator (10, 36, 46, 58, 122) according to any one of claims 1 to 4, wherein: The second axial force is caused by the second generator (32) applying a compensation voltage to the first electrode (20) and the second electrode (22) to generate a compensation electric field, preferably by the second generator (32) applying a DC voltage or a transient DC voltage to the first electrode and the second electrode (20, 22) to generate an axial direct current field (DC field) or an axial transient DC electric field, or by the second generator (32) generating an axial airflow.

6. The trapped ion mobility separator (10, 36, 46, 58, 122) according to any one of claims 1 to 5, wherein: The first electrode (20) and the second electrode (22) are shaped and arranged such that the first electrode (20) and the second electrode (22) surround the separation region (24, 60) perpendicular to the axis (18) within the ion channel (12, 48, 66).

7. The trapped ion mobility separator (10, 36, 46, 58, 122) according to claim 6, wherein: The ion channel (12, 48, 66) comprises a plurality of additional electrodes (26) of the same shape and arrangement as the first electrode (20) and the second electrode (22), wherein the additional electrodes (26) are located between the first electrode (20) and the second electrode (22) along the axis (18) in the ion channel (12, 48, 66), preferably about 1 mm apart from each other, and / or the additional electrodes (26) are connected via a resistor chain or supplied with voltage using a separate voltage generator.

8. The trapped ion mobility separator (10, 36, 46, 58, 122) according to any one of claims 1 to 7, wherein: The ion channel (12, 48, 66) has an elongated cross-sectional profile perpendicular to the axis (18), has a first extension direction and a second extension direction, the first extension direction is longer than the second extension direction, or has a circular cross-sectional profile perpendicular to the axis (18).

9. A trapped ion mobility separator (10, 36, 46, 58, 122) according to any one of claims 1 to 8, wherein the trapped ion mobility separator is coupled to a vacuum system, and the vacuum system is designed and configured to operate the trapped ion mobility separator (10, 36, 46, 58, 122) at a gas pressure in the range of 0.5 mbar to 20 mbar, preferably 2 mbar to 10 mbar.

10. The trapped ion mobility separator (10, 36, 46, 58, 122) according to any one of claims 1 to 9, further comprising an ion trap (38) for storing ions, wherein the ion trap is located upstream of the separation region (24, 60) within the ion channel (12, 48, 66).

11. The trapping ion mobility separator (10, 36, 46, 58, 122) according to any one of claims 1 to 10, wherein: The first generator (30) and the second generator (32) are configured such that the effective axial force generated by the first axial force and the second axial force forms a potential barrier having a substantially constant plateau at which trapped ions leave the separation region (24, 60) and / or the ion channel (12, 48, 66).

12. The trapping ion mobility separator (10, 36, 46, 58, 122) according to any one of claims 1 to 11, wherein: The separation voltage applied by the first generator (30) is applied so that the potential applied to the first electrode (20) has an opposite polarity to the potential applied to the second electrode (22).

13. The trapped ion mobility separator (10, 36, 46, 58, 122) according to any one of claims 1 to 12, wherein: The first generator (30) and the second generator (32) are configured such that a change over time of at least one of the first axial force and the second axial force is gradual, thereby resulting in the release of multiple fractions, each fraction containing multiple ion species, or the change is substantially continuous.

14. A mass spectrometry system (100), comprising an ion source (112), a mass analyzer (168) having an ion detector (176), and at least a first trapped ion mobility separator (10, 36, 46, 58, 122) located downstream of the ion source and / or upstream of the mass analyzer, in, The first trapped ion mobility separator (10, 36, 46, 58, 122) comprises an ion channel (12, 48, 66) in which ions move along an axis (18) between a first end (14, 62) of the ion channel (12, 48, 66) and a second end (16, 64) of the ion channel (12, 48, 66), at the first end ions are introduced into the ion channel (12, 48, 66), the ion channel (12, 48, 66) containing a gas through which the ions pass, wherein the ion channel (12, 48, 66) is supplied with a radial confinement voltage for preventing ions from escaping laterally from the ion channel (12, 48, 66), at least a first electrode (20) and a second electrode (22) arranged to be spaced apart from each other along the axis (18) of the ion channel (12, 48, 66) to define an ion separation region (24, 60) therebetween, a first generator (30) which generates an alternating axial electric field by applying separate voltages to the first electrode (20) and the second electrode (22), the first generator causing a first axial force to be applied to the ions along the axis (18), the first axial force having an effect on the motion of the ions due to interaction with the gas, the motion of the ions being related to differential mobility, wherein the separation voltage is an alternating voltage and is applied so that for a first time interval, an electric field having a first field strength is generated, and for a second time interval after the first time interval, an opposite electric field having a second field strength is generated, the second field strength being lower in magnitude than the first field strength, the first time interval lasting a shorter time span than the second time interval, a second generator (32) causing a second axial force to be applied to the ions along the axis (18), the second axial force at least temporarily counteracting the first axial force, wherein the first generator (30) and the second generator (32) are configured such that at least one of the axial forces varies in strength along the axis (18) to trap ions at mobility-dependent locations along the axis (18) at which a force balance of the first axial force and the second axial force exists for the ions, Also included is an electrical controller (34) that communicates with the first generator (30) and the second generator (32) to vary at least one of the first axial force and the second axial force over time so that the trapped ions are gradually driven to one of the first end (14, 62) and the second end (16, 64) of the ion channel (12, 48, 66) as a function of the differential mobility of the trapped ions.

15. The mass spectrometry system (100) of claim 14, further comprising a fragmentation unit (162) located between the first trapped ion mobility separator (10, 36, 46, 58, 122) and the mass analyzer (168).

16. The mass spectrometry system (100) of claim 15, further comprising a mass filter (158) located between the first trapping ion mobility separator (10, 36, 46, 58, 122) and the fragmentation unit (162).

17. The mass spectrometry system according to any one of claims 14 to 16 further comprises a second ion mobility separator (140), preferably a trapping ion mobility separator constructed and operated to disperse ions according to ion mobility, and located downstream of the first trapping ion mobility separator (10, 36, 46, 58, 122), wherein preferably, the first trapping ion mobility separator (10, 36, 46, 58, 122) and the second ion mobility separator (140) are nested and coupled.

18. The mass spectrometry system according to claim 17 further includes a first shell (124) assigned to the first trapping ion mobility separator (122), and a second shell (142) assigned to the second ion mobility separator (140), wherein the first shell (124) and the second shell (142) contain gas, and the gas assigned to the first shell (124) is different from the gas assigned to the second shell (142).

19. The mass spectrometry system according to claim 17, further comprising an ion selector for selecting ions, which is located between the first trapping ion mobility separator (10, 36, 46, 58, 122) and the second ion mobility separator (140).

20. The mass spectrometry system according to claim 17 further comprises a first ion trap for storing ions located upstream of the first trapping ion mobility separator (10, 36, 46, 58, 122), and / or a second ion trap for storing ions located between the first trapping ion mobility separator (10, 36, 46, 58, 122) and the second ion mobility separator (140).

21. A method for analyzing ions, preferably in a mass spectrometry system (100), using a first trapped ion mobility separator (10, 36, 46, 58, 122), the method comprising the steps of: An ion channel (12, 48, 66) is provided in which ions move along an axis (18) between a first end (14, 62) of the ion channel (12, 48, 66) and a second end (16, 64) of the ion channel (12, 48, 66), at which the ions are introduced into the ion channel (12, 48, 66), the ion channel (12, 48, 66) containing a gas through which the ions pass, wherein the ion channel (12, 48, 66) is supplied with a radial confinement voltage for preventing ions from escaping laterally from the ion channel (12, 48, 66), providing at least a first electrode (20) and a second electrode (22) arranged to be spaced apart from each other along the axis (18) of the ion channel (12, 48, 66) to define an ion separation region (24, 60) therebetween, By applying an alternating separation voltage to the first electrode (20) and the second electrode (22) to generate an alternating axial electric field, a first axial force is generated along the axis (18) applied to the ions, and the first axial force has an effect on the movement of the ions due to the interaction with the gas, and the movement of the ions is related to the differential mobility, applying the alternating separation voltage so that for a first time interval an electric field having a first field strength is generated and for a second time interval following the first time interval an opposite electric field having a second field strength is generated, the second field strength being lower in magnitude than the first field strength, the first time interval lasting a shorter time span than the second time interval, generating a second axial force which is applied to the ions along the axis (18) and which at least temporarily counteracts the first axial force, varying at least one of the axial forces in strength along the axis (18) to trap ions at mobility-dependent locations along the axis (18) where a force balance of the first axial force and the second axial force exists for the ions, At least one of the first axial force and the second axial force is varied over time so that the trapped ions are gradually driven to one of the first end (14, 62) and the second end (16, 64) of the ion channel (12, 48, 66) as a function of the differential mobility of the trapped ions.

22. The method for analyzing ions according to claim 21, further comprising: The alternating axial electric field is generated with a maximum intensity of 20Td to 500Td, preferably 150Td to 250Td, most preferably 200Td.

23. The method for analyzing ions according to claim 21 or 22, further comprising: The separated ions are analyzed as a function of mobility in a second ion mobility separator located downstream of the first trapping ion mobility separator (10, 36, 46, 58, 122), preferably a trapping ion mobility separator (140) constructed and operated to disperse ions according to ion mobility.

24. The method for analyzing ions according to claim 23, further comprising: The separated ions are analyzed as a function of mass in a mass analyzer (168) located downstream of the second ion mobility separator (140), which is constructed and operated to disperse ions according to ion mobility.

25. The method for analyzing ions according to claim 21 or 22, further comprising: The separated ions are dissociated into fragment ions and the fragment ions are analyzed in a mass analyzer (168) located downstream of the first trapping ion mobility separator (10, 36, 46, 58, 122) and / or a second ion mobility separator (140), the second ion mobility separator being constructed and operated to disperse ions according to ion mobility and being located downstream of the first trapping ion mobility separator (10, 36, 46, 58, 122).

26. The method for analyzing ions according to claim 25, wherein: Prior to fragmentation, the separated ions are selected and / or filtered according to mass and / or according to their charge state.

27. The method for analyzing ions according to claim 21, further comprising: Ions from an ion source (112) are accumulated in an ion trap (130) located upstream of the first trapped ion mobility separator (10, 36, 46, 58, 122) while the ions are analyzed in the first trapped ion mobility separator (10, 36, 46, 58, 122).

28. The method for analyzing ions according to claim 27, further comprising: At least one of the first axial force and the second axial force is gradually varied over time so that the trapped ions are driven to one of the first end (14, 62) and the second end (16, 64) of the ion channel (12, 48, 66) in a plurality of separated ion fractions as a function of their differential mobility.

29. The method for analyzing ions according to claim 28, further comprising: The separated ion fraction is analyzed as a function of mobility in a second ion mobility separator located downstream of the first trapping ion mobility separator (10, 36, 46, 58, 122), the second ion mobility separator preferably being a trapping ion mobility separator (140) constructed and operated to disperse ions according to ion mobility, wherein preferably, the first trapping ion mobility separator (10, 36, 46, 58, 122) and the second ion mobility separator (140) are nested and coupled.

30. The method for analyzing ions according to claim 29, further comprising: Deselect the ion fraction consisting essentially of singly charged ion species.

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