Mass spectroscope

Abstract

To simplify the composition of a power supply device that drives a linear ion trap and carry out mass scanning of ejection in the axial direction.SOLUTION: A mass spectroscope comprises: a linear ion trap unit (2) including multiple rod electrodes (20) arranged so as to enclose a center axis (C), an auxiliary electrode (21) provided on the outside of an ion emission-side edge of one of these or projecting from the ion emission-side end, and an extraction electrode (23) located on the outside of the auxiliary electrode; a RF voltage generation unit (50) for applying a RF voltage to the multiple rod electrodes and the auxiliary electrode; an extraction voltage generation unit (52) for applying a DC voltage to the extraction electrode so that a DC electric field for ion extraction extends an ion capture space; and a control unit (4) for changing at least one of the RF voltage and the DC voltage while an ion is trapped in the ion capture space, causing the ion to be ejected in a direction extending along the center axis in correspondence with m / z.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a mass spectrometer.

Background Art

[0002] A mass spectrometer using an ion trap that spatially confines ions by the action of an electric field has been conventionally known. Such ion traps are roughly classified into a linear ion trap and a three-dimensional quadrupole type ion trap (also called a Paul trap). The linear ion trap has advantages such as a relatively simple electrode shape and easy manufacturing compared to the three-dimensional quadrupole type ion trap, a large capacity of the ion capture space, and the ability to hold a larger amount of ions.

[0003] In an ion trap, not only can ions be simply held, but also a mass separation (or mass selection) function can be provided to separate the held ions according to the mass-to-charge ratio (m / z) and release them outside the trap. In mass separation in an ion trap, generally, resonance excitation ejection is used (see Patent Document 1, etc.). In resonance excitation ejection in a linear ion trap, in addition to applying an RF voltage for confining ions in the ion capture space to each rod electrode, an alternating current (AC) voltage for ion excitation that resonates ions having a specific m / z is applied to a specific rod electrode. As a result, among various ions captured in the ion capture space by the action of the RF electric field, only the ions having that specific m / z selectively vibrate greatly and are released outside through the openings formed in the rod electrodes.

[0004] The mass spectrometer described in Patent Document 1 is an orthogonal ejection type linear ion trap that ejects ions held in the linear ion trap in a direction orthogonal to the ion optical axis of the linear ion trap. However, as described in Patent Document 2, an axial ejection type linear ion trap that ejects ions in the same direction as the ion optical axis, that is, in the axial direction, using resonance excitation ejection is also known. The axial ejection type linear ion trap has an advantage that, for example, the ion optical axis thereof can be made coaxial with the ion optical axis of an ion optical element such as a multipole ion guide or a mass filter arranged in the subsequent stage, which facilitates the arrangement of such ion optical elements.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] In resonance excitation ejection, ion mass separation can be realized with a relatively high mass resolution. However, in resonance excitation ejection, it is necessary to apply an AC voltage for ion excitation to the rod electrodes in addition to the RF voltage. Therefore, for example, as described in Patent Document 3, the configuration of the power supply device for applying a voltage to the rod electrodes is complicated. As a result, there are problems such as the device becoming large and heavy, and the cost of the power supply becoming high.

[0007] The present invention has been made to solve such problems, and one of its objects is to provide a mass spectrometer equipped with a linear ion trap that can perform axial ejection while performing mass scanning while simplifying the configuration of a power supply device.

Means for Solving the Problems

[0008] One aspect of the mass spectrometer according to the present invention made to solve the above problems is a plurality of rod electrodes arranged so as to surround a central axis, an auxiliary electrode provided outside or protruding from one ion emission side end of the plurality of rod electrodes and surrounding or sandwiching the central axis, and a drawing electrode arranged further outside the auxiliary electrode, including a linear ion trap section; an RF voltage generator that applies an RF voltage to the plurality of rod electrodes and the auxiliary electrode to form an RF electric field in an ion capture space surrounded by the plurality of rod electrodes and the auxiliary electrode; a draw voltage generator that applies a DC voltage to the draw electrode so that a DC electric field for ion extraction reaches the ion capture space; a control unit that controls the RF voltage generator and the draw voltage generator, and discharges the ions from the ion capture space in a direction along the central axis according to the mass-to-charge ratio by changing at least one of the RF voltage or the DC voltage in a state where the ions are confined in the ion capture space; It is provided with.

Effects of the Invention

[0009] In the above aspect of the mass spectrometer according to the present invention, it is not necessary to superimpose two different alternating voltages, such as an RF voltage and an AC voltage, and apply them to the rod electrodes, like in resonance excitation ejection. Therefore, according to the above aspect of the mass spectrometer according to the present invention, while realizing a mass scan that axially ejects ions from the linear ion trap in the order of mass-to-charge ratio, the configuration of the power supply device that drives the linear ion trap can be simplified. As a result, the power supply device can be made smaller and lighter, and its cost can also be reduced. Also, since ions are ejected axially from the linear ion trap, when arranging ion optical elements such as a quadrupole mass filter or a multipole type ion guide at the subsequent stage, both ion optical axes can be made coaxial, facilitating the arrangement of the ion optical elements.

Brief Description of the Drawings

[0010]

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[0011] Hereinafter, embodiments of a mass spectrometer according to the present invention and a linear ion trap used therein will be described in detail with reference to the accompanying drawings.

[0012] [Schematic Configuration of Mass Spectrometer] FIG. 4 is a schematic configuration diagram of an example of a mass spectrometer according to the present invention. For convenience of explanation, in FIG. 4 and other figures, three axes X, Y, and Z orthogonal to each other are defined in space. This mass spectrometer includes an ion supply unit 1, a linear ion trap 2, a mass analysis / detection unit 3, a control unit 4, and a power supply unit 5. Although not shown, the ion supply unit 1, the linear ion trap 2, and the mass analysis / detection unit 3 can be arranged inside a vacuum chamber or the like.

[0013] The ion supply unit 1 includes an ion source and the like, ionizes various components contained in the sample, and supplies ions to the linear ion trap 2 in a direction generally along the ion optical axis C (Z-axis direction). The linear ion trap 2 includes a plurality (only 4 are depicted in FIG. 4, but actually 6) of rod electrodes 201 to 206, temporarily holds ions in the internal space (ion trapping space) 200 surrounded by the rod electrodes 201 to 206, and discharges the held ions in the direction along the ion optical axis C in descending order of m / z. That is, the linear ion trap 2 is an axially discharging type linear ion trap capable of mass scanning.

[0014] The power supply unit 5 applies voltages to the respective electrodes included in the linear ion trap 2 under the control of the control unit 4. The mass spectrometry / detection unit 3 has a configuration including one or more mass separators and a detector, or a configuration including only a detector. In the former case, the mass spectrometry / detection unit 3 further separates the ions discharged from the linear ion trap 2 according to m / z and then detects them. On the other hand, in the latter case, the mass spectrometry / detection unit 3 directly detects the ions discharged from the linear ion trap 2. The specific configuration of the mass spectrometry / detection unit 3 is shown in the configuration examples described later. The control unit 4 generally has a configuration including a CPU, a ROM, a RAM, etc., and outputs control signals to respective units such as the power supply unit 5 according to a preset control program to execute an analysis operation.

[0015] [Configuration of Linear Ion Trap] FIG. 3 is a diagram for explaining in detail the electrode structure of the linear ion trap 2 in FIG. 4, (A) is a schematic front longitudinal sectional view, (B) is a cross-sectional view taken along the line A-AA in (A), and (C) is a cross-sectional view taken along the line B-BB in (A). FIG. 1 is a schematic perspective view showing the structure of the rod electrode, and FIG. 2 is an auxiliary diagram for explaining the structure of this rod electrode.

[0016] As shown in FIG. 3, the linear ion trap 2 includes a rod electrode group 20 composed of six rod electrodes 201, 202, 203, 204, 205, and 206 arranged to surround a linear ion optical axis C extending in the Z-axis direction; a three-dimensional ion trap partial electrode 21 provided continuously (electrically connected) to the end of the rod electrode group 20 on the ion emission side (the right side in this figure); an entrance side end cap electrode 22 having a substantially disk shape with a circular opening 22a at the center, arranged outside the end of the rod electrode group 20 on the ion incident side (the left side in this figure); and a disk-shaped extraction electrode 23 having a substantially circular opening 23a, arranged outside the three-dimensional ion trap partial electrode 21. The extraction electrode 23 also serves as the exit side end cap electrode in a general linear ion trap.

[0017] As shown in FIG. 3(B), the six rod electrodes 201 to 206 are circumscribed about a circle (shown by a dashed line in the figure) centered on the ion optical axis C and are arranged at equal angular intervals (60°) around the ion optical axis C. On the other hand, the three-dimensional ion trap partial electrode 21 is composed of a part of two ring-shaped electrodes 212 and 213 and two spherical electrodes 211 and 214 that sandwich them, which form a six-pole three-dimensional ion trap as shown in FIG. 2. Specifically, it is an electrode obtained by dividing those electrodes exactly in half in the X-Y plane perpendicular to the ion optical axis C (Z-axis). Here, the four electrodes constituting the three-dimensional ion trap partial electrode 21 are given the same reference numerals as the ring-shaped electrode and the spherical electrode shown in FIG. 2 to clarify the correspondence.

[0018] The diameters of the spherical electrodes 211 and 214 are equal to the diameters of the rod electrodes 201 and 204, and the diameters of the ring electrodes 212 and 213 are equal to the diameters of the rod electrodes 202, 203, 204, and 205. Therefore, the rod electrode 201 and the spherical electrode 211, the rod electrode 204 and the spherical electrode 214, the rod electrodes 202, 206 and the ring electrode 212, and the rod electrodes 203, 205 and the ring electrode 213 are connected without steps and integrated. That is, the rod electrodes 202, 206 and the ring electrode 212, and the rod electrodes 203, 205 and the ring electrode 213 are each U-shaped electrodes in a plan view. Also, the rod electrode 201 and the spherical electrode 211, and the rod electrode 204 and the spherical electrode 214 are each linear electrodes with one end being spherical.

[0019] However, as shown in FIG. 3(C), in the two ring electrodes 212 and 213 sandwiching the ion optical axis C, the portions directed toward the ion optical axis C are formed as cutout portions 212a and 213a having a cylindrical shape with the ion optical axis C as the central axis. These cutout portions 212a and 213a, together with the gap between the original (i.e., the state without the cutout portions) two ring electrodes 212 and 213, can function as an ion extraction aperture 210 through which the DC electric field formed by the extraction electrode 23 enters the ion capture space 200 and ions are extracted by the electric field, as will be described later.

[0020] As shown in FIG. 4, a predetermined DC voltage can be applied to the inlet-side end cap electrode 22 from the inlet-side electrode DC power supply unit 51 included in the power supply unit 5. A predetermined DC voltage is applied to the extraction electrode 23 from the extraction electrode DC power supply unit 52. Predetermined RF voltages are applied to each of the rod electrodes 201 to 206 included in the rod electrode group 20 and each of the electrodes 211 to 214 included in the three-dimensional ion trap partial electrode 21 from the RF power supply unit 50, respectively. Specifically, the RF voltages applied to the six rod electrodes 201 to 206 have the same amplitude and frequency, and the polarities are inverted (that is, the phases are shifted by 180°) between two adjacent rod electrodes in the circumferential direction. Here, since the two rod electrodes 202 and 206 are connected via the ring-shaped electrode 212 and the other two rod electrodes 203 and 205 are connected via the ring-shaped electrode 213, by applying RF voltages to the four rod electrodes 201, 202, 203, and 204 shown in FIG. 4, respectively, the necessary RF voltages can be applied to all the electrodes included in the rod electrode group 20 and the three-dimensional ion trap partial electrode 21.

[0021] [Operation of Linear Ion Trap] Next, an example of the basic operation of the linear ion trap 2 will be described. FIG. 6 is an example of the change in the applied voltage when driving the linear ion trap 2, and is a timing diagram in the case of performing mass scanning by changing the RF voltage. FIG. 7 is another example of the change in the applied voltage when driving the linear ion trap 2, and is a timing diagram in the case of performing mass scanning by changing the extraction DC voltage.

[0022] In FIG. 4, the ion supply unit 1 sends various ions derived from a sample to be analyzed generally in the direction along the ion optical axis C. The inlet side electrode DC power supply unit 51 receives the ions supplied from the ion supply unit 1 for a predetermined period, and forms a DC electric field that blocks the ions in front of the inlet side end cap electrode 22 when that period has passed, by applying a DC voltage that changes at a predetermined timing to the inlet side end cap electrode 22. Further, the RF power supply unit 50 applies a predetermined RF voltage to each of the rod electrodes 201 to 206, thereby forming a multipole RF electric field in the ion trapping space 200 that traps various ions introduced into the ion trapping space 200 through the opening 22a of the inlet side end cap electrode 22. The extraction electrode DC power supply unit 52 applies a DC voltage to the extraction electrode 23 that can form a DC electric field that pushes the ions back so that the ions do not leak out of the ion trapping space 200.

[0023] The multipole RF electric field generates an RF pseudo-potential that has the effect of confining ions. In a linear ion trap, characteristics such as the mass dependence of the ion confinement ability and the converging force that collects ions near the central axis change according to the number of rod electrodes, that is, the number of poles. Generally, as the number of poles increases, the mass dependence of the confinement ability decreases (it becomes possible to confine ions with a wider m / z), but the converging force also decreases. Therefore, here a six-pole configuration is used as the linear ion trap, but according to the desired characteristics, a number of poles other than six may be selected. Specifically, theoretically, a configuration of an N-pole where N = 6 + 4M (where M is 0, 1, 2,...) can be adopted. In any case, due to the action of the RF pseudo-potential by the multipole RF electric field, various ions derived from the sample are confined in the ion trapping space 200.

[0024] Although not shown in the drawings, an inert gas such as helium or argon can be introduced into the linear ion trap 2 through an inert gas introduction pipe. The various ions captured in the ion capture space 200 come into contact with the inert gas and lose their kinetic energy. That is, the various ions are cooled in the ion capture space 200, whereby the spread of the ions in the longitudinal direction (Z-axis direction) is suppressed and they tend to exist near the ion optical axis C.

[0025] For example, when the target ion is a positive ion, the polarity of the DC voltage applied to the extraction electrode 23 during ion accumulation and cooling is the same polarity as the ion, that is, the positive polarity, as shown in FIG. 6. The combination of the confinement action by the RF pseudo-potential and the confinement action by the electric field formed by the DC voltages applied to the inlet-side end-cap electrode 22 and the extraction electrode 23 respectively confines the ions well in the ion capture space 200.

[0026] After the ion cooling has been performed for a predetermined time, as shown in FIG. 6, the extraction DC voltage applied to the extraction electrode 23 is switched to the opposite polarity to the ion polarity (negative polarity in this case). The electric field formed by this negative-polarity DC voltage has the effect of attracting the ions and reaches the ion capture space 200 through the ion extraction opening 210 including the defective portions 212a and 213a. Therefore, when ions are captured in the ion capture space 200 by the multipole RF electric field as described above, a force due to the DC electric field also acts on the ions. However, at this time, since the confinement action by the RF pseudo-potential is greater than the force acting on the ions due to the DC electric field, the ions can remain in the ion capture space 200.

[0027] As described above, simultaneously with or immediately after switching the polarity of the extraction DC voltage, the RF power supply unit 50 changes the amplitude of the RF voltage applied to the rod electrodes 201 to 206 so as to gradually decrease it. The strength of the ion confinement effect by the RF pseudo-potential inside the linear ion trap is inversely proportional to the mass of the ions. That is, the larger the m / z value of the ions, the smaller the confinement effect by the RF pseudo-potential, and the easier it is for the ions to escape from the ion capture space 200. Therefore, when the amplitude of the RF voltage applied to the rod electrodes 201 to 206 is gradually decreased, the binding force on the ions becomes weaker in the direction of decreasing m / z in order from the ions with relatively large m / z. On the other hand, the extraction DC electric field generated by the extraction electrode 23 acts uniformly on the ions regardless of the mass of the ions. Therefore, the ions are attracted by the extraction DC electric field in order from the ions whose binding force by the RF pseudo-potential has weakened, that is, in order from the ions with large m / z, and are drawn out generally in the Z-axis direction (along the ion optical axis C) through the ion extraction aperture 210 and the aperture 23a of the extraction electrode 23.

[0028] As shown in FIG. 6, when the amplitude of the RF voltage is gradually decreased while maintaining the extraction DC voltage at a constant value, the ions captured in the ion capture space 200 of the linear ion trap 2 are discharged in order from the ones with high m / z values through the ion extraction aperture 210 and the aperture 23a. That is, a mass scan in the direction of decreasing m / z of the ions drawn out from the linear ion trap 2 is achieved.

[0029] Instead of gradually decreasing the amplitude of the RF voltage as described above, as shown in FIG. 7, while maintaining the amplitude of the RF voltage at a constant value, that is, while maintaining the ion confinement effect by the RF pseudo-potential constant, the voltage value of the DC voltage applied to the extraction electrode 23 may be changed so as to gradually strengthen the extraction DC electric field. Also by this, similar to the case of changing the amplitude of the RF voltage as described above, a mass scan in the direction of decreasing m / z value of the ions drawn out from the ion capture space 200 can be performed.

[0030] However, as in the example of FIG. 7, when the extraction DC voltage is gradually changed for mass scanning, the energy of the ions after passing through the extraction electrode 23 changes accordingly. Therefore, this control method may be used when this energy change does not pose a problem. On the other hand, as will be described later, when the linear ion trap is arranged in the collision cell in a Q-TOF type mass spectrometer, etc., it is desirable to keep the kinetic energy of the ions ejected from the linear ion trap constant regardless of the m / z value. Therefore, in that case, as shown in FIG. 6, a control method may be adopted in which mass scanning is performed by changing the amplitude of the RF voltage instead of the extraction DC voltage.

[0031] FIG. 5 is an example of the result of simulating the trajectory of ions from the time they are introduced into the ion capture space 200 of the linear ion trap 2 until they are extracted outward. Here, only the trajectory of one ion is drawn in order to make the ion trajectory easy to understand.

[0032] As can be seen from FIG. 5, ions enter through the opening 22a of the entrance-side end cap electrode 22 and are accumulated in the ion capture space 200 while being cooled by collision with the gas present in the ion capture space 200. At this time, a DC voltage equivalent to that of the entrance-side end cap electrode 22 is applied to the extraction electrode 23. At the timing of extracting the ions, the polarity of the DC voltage applied to the extraction electrode 23 is switched, and the extraction DC voltage is increased so that the extraction electric field gradually increases, or the RF voltage is gradually decreased, then the ions are axially extracted outward through the opening 23a in the order of increasing m / z.

[0033] FIGS. 8 and 9 are diagrams showing the results of simulation calculations of the ion extraction efficiency from the linear ion trap 2. FIG. 8 is a diagram showing the relationship between the amplitude value of the RF voltage and the ion extraction efficiency when the extraction DC voltage is kept constant at -20V. Here, only one type of ion with m / z 400 is used as the target ion. FIG. 9 is a diagram showing the relationship between the m / z value of the ions and the extraction efficiency when the amplitude of the RF voltage and the extraction DC voltage are kept constant.

[0034] In FIGS. 8 and 9, an ion extraction efficiency of 0% means a state in which ions are stably present and confined in the ion capture space 200. On the other hand, an ion extraction efficiency of 100% means a state in which ions cannot stably exist in the ion capture space 200 and all ions are extracted. From FIG. 8, it can be seen that in the state where the amplitude of the RF voltage is 120V while keeping the extraction DC voltage constant at -20V, ions with m / z 400 are not extracted. Then, as the amplitude of the RF voltage is gradually decreased from about 115V, ions with m / z 400 are gradually extracted, and when the amplitude of the RF voltage is reduced to about 100V or less, almost all ions with m / z 400 are extracted, that is, discharged.

[0035] Also, as described above, the ion confinement ability by the RF pseudo-potential is inversely proportional to the mass of the ions. From FIG. 9, when the voltage conditions are constant, it can be confirmed that higher mass ions are more easily discharged, and the action as a high-pass filter regarding mass is obtained as expected. Under the voltage conditions shown in FIG. 9, mass selectivity is shown such that most ions with m / z 400 or more can be discharged while generally leaving ions with m / z 300 or less in the ion capture space 200. This mass selectivity can be improved by optimizing the gas pressure (which affects ion cooling), the amplitude of the RF voltage, the extraction DC voltage, etc.

[0036] In FIG. 9, the decreasing trend in the extraction efficiency of ions with m / z 500 or more is due to the influence of ion loss during accumulation in the ion capture space 200, which can be presumed to be caused by the fact that the ion confinement force by the RF pseudo-potential becomes weaker as the m / z increases. To improve the ion confinement force, it is effective to increase the number of poles of the multipole field. Therefore, especially when it is necessary to increase the supply amount of high m / z ions, it is advisable to increase the number of poles of the linear ion trap, that is, the number of rod electrodes.

[0037] Thus, in the linear ion trap 2 described above, parameters such as gas pressure, the number of poles of the multipole field, the amplitude of the RF voltage, and the extraction DC voltage affect the performance. Depending on how these parameter values are combined and changed, flexible ion operations according to the purpose can be performed, which is also one of the characteristics of this linear ion trap.

[0038] [Configuration Example 1 of Mass Spectrometer] A specific configuration example of the above mass spectrometer will be described. There are various types of mass separators used in mass spectrometers. Currently, the most widely used is the quadrupole mass filter. In tandem mass spectrometers, in addition to triple quadrupole mass spectrometers, quadrupole - time - of - flight mass spectrometers, quadrupole - Fourier transform mass spectrometers, etc., quadrupole mass filters are used. Although the quadrupole mass filter is an easy - to - use mass separator, since it selectively passes only ions having a specific m / z (or a certain m / z range), there is a problem that many ions having other m / z that cannot pass are wasted. That is, the ion utilization efficiency in the quadrupole mass filter is not necessarily high.

[0039] To solve this problem, the above - described linear ion trap can be used. FIG. 10 is a schematic configuration diagram of a mass spectrometer according to Configuration Example 1. In this mass spectrometer, the mass analysis / detection unit 3 includes a quadrupole mass filter 31 and an ion detector 32. A linear ion trap 2 having the above - described configuration is arranged in front of the quadrupole mass filter 31. Also, the ion supply unit 1 includes an ion source 10 and a pole - number conversion ion guide 11, and the ions emitted from the pole - number conversion ion guide 11 are introduced into the linear ion trap 2. Here, the ion optical axes C of the pole - number conversion ion guide 11, the linear ion trap 2, and the quadrupole mass filter 31 coincide, that is, they are located on a straight line.

[0040] The pole number conversion ion guide 11 is a multipole ion guide described in Patent Document 4, for example. By arranging at least some of the rod electrodes at an angle with respect to the linear ion optical axis C, it is an ion guide in which the number of poles at the ion inlet end and the number of poles at the ion outlet end are different. Here, ten rod electrodes are used. At the ion inlet end, a decapole arrangement is adopted in which the ten rod electrodes are arranged at substantially equal angular intervals so as to surround the ion optical axis C. At the ion outlet end, a hexapole arrangement is adopted in which only six of the ten rod electrodes are arranged at substantially equal angular intervals so as to surround the ion optical axis C.

[0041] Similar to the linear ion trap 2 described above, in a multipole ion guide, the greater the number of poles, the stronger the ion confinement force. Therefore, by adopting an arrangement with a large number of poles at the ion inlet end, ions arriving while spreading from the previous stage (ion source 10 in FIG. 10) can be efficiently collected and taken into the internal space of the pole number conversion ion guide 11. On the other hand, since the ion focusing effect is stronger when the number of poles is small, by adopting an arrangement with a relatively small number of poles at the ion outlet end, the ions can be focused near the ion optical axis C and sent to the subsequent stage (linear ion trap 2 in FIG. 10) without waste. Also, in the pole number conversion ion guide 11, an axial electric field for transporting (i.e., accelerating) ions in the traveling direction can be generated by the DC voltage applied to each rod electrode.

[0042] In this configuration, the ion outlet end of the pole number conversion ion guide 11 is arranged in a hexapole configuration in order to make the number of poles at the ion outlet end of the pole number conversion ion guide 11 the same as the number of poles of the linear ion trap 2 for the purpose of aligning the mass selectivity of the multipole RF electric field. However, this is not essential.

[0043] Referring to the timing diagram shown in FIG. 11, the typical operation of this mass spectrometer will be described. Ions derived from sample components generated by the ion source 10 are introduced into the pole-changing ion guide 11. As described above, since an axial electric field and a multipole RF electric field in the direction of ion travel are formed in the internal space of the pole-changing ion guide 11, the ions travel toward the exit while being converged by this electric field. A DC voltage that usually acts as a barrier for the ions is applied to the inlet-side end-cap electrode 22 of the linear ion trap 2. Therefore, the ions that reach the exit region of the pole-changing ion guide 11 are blocked in front of the inlet-side end-cap electrode 22 and accumulated in the exit region of the pole-changing ion guide 11.

[0044] As shown in FIG. 11, when the voltage applied to the inlet-side end-cap electrode 22 is temporarily lowered at a predetermined timing, the potential barrier disappears only at that time, so that the ions accumulated in the exit region of the pole-changing ion guide 11 are introduced into the ion trapping space 200 of the linear ion trap 2 through the aperture 22a. That is, the transfer of ions from the pole-changing ion guide 11 to the linear ion trap 2 is carried out in packets. After the accumulated ions are transferred and the applied voltage to the inlet-side end-cap electrode 22 is raised again, ions begin to accumulate in the exit region of the pole-changing ion guide 11. By accumulating ions in the exit region of the pole-changing ion guide 11 in this way, even when the period during which ions can be introduced into the linear ion trap 2 is limited, it is possible to avoid loss of ions continuously fed from the ion source 10 and introduce ions into the linear ion trap 2 with high efficiency.

[0045] As described above, the ions introduced into the ion capture space 200 are sufficiently captured while being cooled by contact with the gas, and then, as the amplitude of the RF voltage applied to the rod electrode group 20 is gradually decreased, they are drawn out along the ion optical axis C through the opening 23a of the extraction electrode 23 in descending order of m / z. At this time, the ions having a predetermined m / z discharged from the linear ion trap 2 are selected by the quadrupole mass filter 31 in the subsequent stage. That is, the scanning of the RF voltage applied to the rod electrode group 20 of the linear ion trap 2 is controlled synchronously with the scanning of the voltage (a voltage obtained by superimposing an RF voltage and a DC voltage) applied to the quadrupole mass filter 31 so as to match the m / z of the ions passing through the quadrupole mass filter 31.

[0046] In a conventional quadrupole type mass spectrometer using a quadrupole mass filter as a mass separator, when mass scanning is performed by the quadrupole mass filter, ions other than those passing through the quadrupole mass filter are discarded, so the ion utilization efficiency is not necessarily high. In contrast, in the mass spectrometer of the above-described configuration example 1, among the ions accumulated in the linear ion trap 2, only the ions having an m / z that can generally pass through the quadrupole mass filter 31 are selectively discharged from the linear ion trap 2 and sent to the quadrupole mass filter 31. Therefore, ions that would be lost by the quadrupole mass filter in the past can be effectively utilized. As a result, higher sensitivity can be achieved compared to a conventional quadrupole type mass spectrometer. In addition, since most of the ions derived from the sample components generated by the ion source 10 can be subjected to mass spectrometry, even when ions having a specific m / z are temporarily generated, it is difficult to miss such ions, which is useful for comprehensively grasping the ions derived from the sample components.

[0047] Although the above Configuration Example 1 is a single-type quadrupole mass spectrometer, the linear ion trap 2 described above may be arranged in front of the first-stage quadrupole mass filter in a triple quadrupole mass spectrometer capable of MS / MS analysis. In this case, for example, when performing mass scanning with the first-stage quadrupole mass filter, such as precursor ion scan measurement or neutral ion scan measurement, the linear ion trap 2 and the first-stage quadrupole mass filter may be synchronously controlled so that the m / z of the ions ejected from the linear ion trap 2 is approximately the same as the m / z of the ions passing through the first-stage quadrupole mass filter.

[0048] [Configuration Example 2 of Mass Spectrometer] In a Q-TOF mass spectrometer in which a collision cell is arranged between a quadrupole mass filter and an orthogonal acceleration time-of-flight mass separator, various product ions can be generated from a single type of precursor ion in the collision cell. However, the time required for the ions ejected almost simultaneously from the collision cell to reach the orthogonal acceleration section varies depending on the m / z of the ions. Therefore, when accelerating the ions pulsedly in the orthogonal acceleration section, only the product ions included in a limited m / z range among the various m / z product ions derived from a single type of precursor ion may be accelerated. In that case, there is a problem that the observable m / z range of the product ions is limited and an accurate product ion spectrum cannot be obtained.

[0049] The mass spectrometer according to Configuration Example 2 uses the linear ion trap 2 described above to solve the above problems. FIG. 12 is a schematic configuration diagram of the mass spectrometer according to Configuration Example 2. In this mass spectrometer, the mass spectrometry and detection unit 3 includes a quadrupole mass filter 33, an orthogonal acceleration time-of-flight mass separator 34, and an ion detector 32. The linear ion trap 2 with the above configuration is arranged inside a collision cell (not shown) between the quadrupole mass filter 33 and the orthogonal acceleration time-of-flight mass separator 34. Note that in FIG. 12, the description of the components corresponding to the ion supply unit 1 is omitted. The orthogonal acceleration time-of-flight mass separator 34 includes an orthogonal acceleration unit 341 including a pair of extrusion electrodes 341A and pull-in electrodes 341B, an acceleration electrode 342, a flight tube 343, and a reflection electrode 344.

[0050] The quadrupole mass filter 33 selectively passes ions having a specific m / z among the ions supplied from an ion supply unit (not shown). These ions are introduced into the ion capture space 200 of the linear ion trap 2, come into contact with the collision gas supplied to the ion capture space 200, and dissociation occurs, generating various product ions. The generated product ions are captured in the ion capture space 200 by an RF electric field. Then, while maintaining the extraction DC voltage constant, by changing the RF voltage applied to the rod electrode group 20, the product ions captured in the ion capture space 200 are discharged in descending order of m / z through the ion extraction aperture 210 and the aperture 23a. The discharged ions generally travel along the ion optical axis C and reach the orthogonal acceleration unit 341.

[0051] While maintaining the extraction DC voltage at a constant value, a certain energy is imparted to each ion regardless of m / z to the ions discharged from the linear ion trap 2 by the action of the extraction DC electric field formed by this voltage. Therefore, ions with a relatively small m / z that are discharged later in time have a higher moving speed than ions with a relatively large m / z that are discharged earlier in time. Thus, by appropriately controlling the change in the RF voltage, it is possible to make all ions with different m / z values discharged from the linear ion trap 2 at different times reach a predetermined position inside the orthogonal acceleration unit 341 almost simultaneously.

[0052] In the orthogonal acceleration time-of-flight mass separator 34, ions are introduced into the orthogonal acceleration section 341 in the Z-axis direction along the ion optical axis C. As described above, at the timing when various ions with different m / z values enter the orthogonal acceleration section 341 almost simultaneously, a predetermined pulsed DC voltage is applied to the push-out electrode 341A and the pull-in electrode 341B, respectively. Then, the ions having various m / z values that had passed through the orthogonal acceleration section 341 at that time are pushed out in the Y-axis direction through the slit of the pull-in electrode 341B, and then accelerated by the acceleration electrode 342 and ejected into the flight tube 343.

[0053] The ions fly inside the flight tube 343, are folded back by the electric field formed by the reflection electrode 344, and then fly inside the flight tube 343 again. The ions that have flown along the folded-back orbit C1 finally reach the ion detector 32 and are detected. Since the ions ejected almost simultaneously from the orthogonal acceleration section 341 fly with flight times corresponding to their respective m / z values, they are separated according to their m / z values during flight, and the ions with smaller m / z values reach the ion detector 32 in order.

[0054] Thus, in the mass spectrometer of this Configuration Example 2, ions with a wide range of m / z values supplied from the linear ion trap 2 can be sent into the flight space without waste and mass spectrometry can be performed. Thereby, product ions with a wide range of m / z values can be detected with high sensitivity. In this mass spectrometer, as described above, in order to make all the ions discharged from the linear ion trap 2 toward the orthogonal acceleration section 341 reach a predetermined position in the orthogonal acceleration section 341 almost simultaneously, the extraction of ions from the linear ion trap 2 may be controlled under the following conditions.

[0055] Now, as shown in FIG. 12, let the distance from the extraction electrode 23 to the orthogonal acceleration section 341 be L, and the length of the ion passage region of the orthogonal acceleration section 341 be D. Also, assume that the space from the extraction electrode 23 to the orthogonal acceleration section 341 is at the same potential. Further, assume that the energy of the ions extracted from the linear ion trap 2 is accelerated by the extraction DC voltage V E from the state where the ions are sufficiently cooled, and is eV E . Assuming that the ions do not collide with neutral particles between the extraction electrode 23 and the orthogonal acceleration section 341, in the prior art where all ions are extracted from the ion trap substantially simultaneously, the time t for the ions with the lightest mass m1 to reach the outlet of the orthogonal acceleration section 341 is expressed by the following equation (1). t = (D + L)√(m1 / 2eV E ) …(1) The maximum mass m2 that can be observed simultaneously is such that it can reach the inlet of the orthogonal acceleration section 341 at the same time, and its arrival time t is given by the following equation (2). t = D√(m2 / 2eV E ) …(2) Therefore, the observable mass range is expressed by the following equation (3). m2 / m1 = {(D + L) / D} 2 …(3)

[0056] On the other hand, by using the linear ion trap 2 that discharges ions in descending order of m / z as described above, ions with heavy masses can be sent out first. Therefore, it is possible to control so that these heavy-mass ions and the light ions sent out later reach a certain position in the orthogonal acceleration section 341 at the same time. Considering the case where ions of all masses reach the center of the orthogonal acceleration section 341 simultaneously, the arrival time of the ions with the maximum mass m2 is t = {D + (L / 2)}√(m2 / 2eV E ) …(4) and the delay time t D required for RF voltage control so that these ions and the ions with the minimum mass m1 reach simultaneously is t D = {D + (L / 2)}{(√m2 - √m1) / √(2eVE )} …(5) is.

[0057] That is, by performing a scan of the RF voltage so as to provide the above-mentioned delay time t D to extract ions from the linear ion trap 2, it is possible to cause all ions in the target mass range to reach the same position in the orthogonal acceleration section 341 almost simultaneously. As a result, not only is the mass range of the ions to be observed expanded compared to the prior art, but also the variation in the initial positions of the ions in the orthogonal acceleration section 341 is reduced, thereby achieving an improvement in detection sensitivity and mass resolution. Further, in this Configuration Example 2, in order to make the energy of the ions extracted from the linear ion trap 2 constant as described above, it is preferable to scan the RF voltage instead of the extraction DC voltage so that the ions are extracted in descending order of m / z.

[0058] [Configuration Example 3 of Mass Spectrometer] FIG. 13 is a configuration diagram of a main part of a mass spectrometer according to Configuration Example 3. In the mass spectrometer of this Configuration Example 3, the above-mentioned linear ion trap 2 is combined in front of the multi-turn Fourier transform type mass separation section 36. In this configuration, the ions discharged from the linear ion trap 2 are introduced into the multi-turn Fourier transform type mass separation section 36 through the ion incident section 35 and fly along the circular orbit C2. The voltage applied to the electrodes constituting the ion incident section 35 is switched so as to form an incident electric field for placing the ions arriving from the linear ion trap 2 on the circular orbit C2 during the period when the ions are incident, and to form a circular electric field for the ions to fly along the circular orbit C2 during the period when the ions are orbiting.

[0059] In a conventional mass spectrometer of this type, since it is necessary to place ions ejected from the ion trap almost simultaneously on the circular orbit C2 almost simultaneously, it is necessary to limit the m / z range of the ions to be mass-analyzed simultaneously to a narrow range. On the other hand, in the mass spectrometer of this Configuration Example 3, similar to Configuration Example 2, ions with a large m / z and a relatively slow flight speed are first ejected from the linear ion trap 2, and the ions are gradually ejected in descending order of m / z and placed on the circular orbit C2, so that ions of all m / z can reach an arbitrary position on the circular orbit C2 almost simultaneously. Thereby, the m / z range of the ions to be observed can be widened. Also, it is necessary to switch the applied voltage to the ion injection section 35 until the ion that makes one revolution the fastest among the ions introduced into the circular orbit C2 via the ion injection section 35 returns to the ion injection section 35. However, since ions with a small m / z are introduced into the circular orbit C2 later than ions with a large m / z, the period during which the ions are placed on the circular orbit C2 at the ion injection section 35 can be lengthened, and more ions can be used for mass spectrometry. Thereby, the detection sensitivity can also be improved.

[0060] In this case, when calculating the delay time t using Equation (5), L may be the flight length of the ion injection section 35, and D may be the flight length to the point where the ions reach simultaneously on the circular orbit C2. D

[0061] [Modification Example of Linear Ion Trap] In the linear ion trap 2 described with reference to FIGS. 1, 3, etc., the three-dimensional ion trap partial electrode 21 is for enhancing the ion confinement action by the multipole RF electric field at the end of the rod electrode group 20 located on the side of the extraction electrode 23, and corresponds to the auxiliary electrode in the present invention. When there is no such auxiliary electrode (that is, when there is no RF electric field by the auxiliary electrode), when an extraction DC voltage is applied to the extraction electrode 23, ions with a relatively small m / z that are not sufficiently trapped by the RF electric field may leak out simultaneously with ions having a relatively large m / z. Therefore, it is necessary to arrange an auxiliary electrode for forming an RF electric field for preventing ion leakage between the end of the rod electrode group 20 and the extraction electrode 23. However, the configuration and shape of this auxiliary electrode are not limited to those described above.

[0062] Specifically, in the above linear ion trap 2, each electrode of the rod electrode group 20 and the three-dimensional ion trap partial electrode 21 was integrated, but they may be separate. That is, as shown in FIG. 14, the three-dimensional ion trap partial electrode 21A having the same configuration and shape as the above three-dimensional ion trap partial electrode 21 may be arranged with a predetermined gap (a gap of length d in this example) from the end of the rod electrode group 20. Of course, also in this case, the same RF voltage as in the above example is applied to each electrode constituting the three-dimensional ion trap partial electrode 21. Further, in this case, since it is possible to apply different voltages to each electrode of the rod electrode group 20 and each electrode of the three-dimensional ion trap partial electrode 21, by scanning (changing) only the RF voltage applied to each electrode of the three-dimensional ion trap partial electrode 21 while keeping the RF voltage applied to each electrode of the rod electrode group 20 constant, ion ejection according to m / z can also be performed.

[0063] Alternatively, instead of the three-dimensional ion trap partial electrodes 21 and 21A as the auxiliary electrodes, an RF gate electrode 21B formed by combining two semi-annular electrodes in a plan view as shown in Fig. 15 can also be used. This RF gate electrode 21B is disposed inside an annular electrode to which an appropriate DC voltage is applied, and RF voltages with inverted phases are applied to the two electrodes constituting the RF gate electrode 21B. By applying such an RF voltage, an axial dipole RF electric field is formed in the space inside the RF gate electrode 21B. This dipole RF electric field functions as an RF pseudo-potential barrier for the ions trapped in the ion trapping space 200, and when the amplitude of the applied RF voltage is large, it prevents the ions from leaking out to the side of the extraction electrode 23.

[0064] Fig. 16 is an example of a timing diagram of the change in the applied voltage when driving the linear ion trap shown in Fig. 15. In this configuration, when extracting ions from the ion trapping space 200 in descending order of m / z, both the extraction DC voltage applied to the extraction electrode 23 and the amplitude of the RF voltage applied to each of the rod electrodes 201 to 206 are maintained constant. Then, only the amplitude of the RF voltage applied to the RF gate electrode 21B is gradually decreased. The RF pseudo-potential barrier formed by the RF gate electrode 21B has different heights depending on the mass of the ions, and the larger the mass of the ions, the easier it is to overcome the RF pseudo-potential barrier. Therefore, when the amplitude of the RF voltage applied to the RF gate electrode 21B is gradually decreased, similar to the linear ion trap in the above example, ions are discharged through the aperture 23a in order from the ions with a large m / z, and axial discharge according to m / z is achieved.

[0065] Fig. 17 is an example of the result of simulating the trajectory of ions from when they are introduced into the ion trapping space until they are pulled out to the outside in the linear ion trap shown in Fig. 15. In this case, different from the example shown in Fig. 5, a hexapole electric field is not formed in the axial direction, and an RF pseudo-potential barrier is formed near the RF gate electrode 21B. Therefore, the ions are trapped near the RF gate electrode 21B, and for example, as the RF voltage is decreased, the ions are axially pulled out to the outside in order of decreasing m / z.

[0066] Note that the above-described embodiments and configuration examples are merely examples of the present invention, and it is natural that even if modifications, additions, or corrections are appropriately made within the scope of the gist of the present invention, they are included in the scope of the claims of this patent.

[0067] [Various aspects] Those skilled in the art will understand that the above-described exemplary embodiments are specific examples of the following aspects.

[0068] (Item 1) One aspect of the mass spectrometer according to the present invention is a linear ion trap unit including a plurality of rod electrodes arranged so as to surround a central axis, an auxiliary electrode provided outside or protruding from one ion emission side end of the plurality of rod electrodes and surrounding or sandwiching the central axis, and an extraction electrode arranged further outside the auxiliary electrode; an RF voltage generation unit that applies an RF voltage to the plurality of rod electrodes and the auxiliary electrode to form an RF electric field in an ion capture space surrounded by the plurality of rod electrodes and the auxiliary electrode; an extraction voltage generation unit that applies a DC voltage to the extraction electrode so that a DC electric field for ion extraction reaches the ion capture space; a control unit that controls the RF voltage generation unit and the extraction voltage generation unit, and discharges the ions from the ion capture space in a direction along the central axis according to the mass-to-charge ratio by changing at least one of the RF voltage or the DC voltage in a state where the ions are confined in the ion capture space; and includes.

[0069] In the mass spectrometer according to the first aspect, when extracting ions from the linear ion trap in the order of m / z, the voltage to be scanned may be either the RF voltage applied to the rod electrodes or the DC voltage applied to the extraction electrodes. Therefore, unlike the conventional resonance excitation ejection, it is not necessary to apply two different AC voltages, namely the RF voltage and the AC voltage, to the rod electrodes in a superimposed manner. Thus, according to the mass spectrometer described in the first aspect, while realizing a mass scan for releasing ions from the linear ion trap in the order of m / z, the configuration of the power supply device for driving the linear ion trap can be simplified. As a result, the power supply device can be made smaller and lighter, and its cost can also be reduced. Further, since ions are ejected in the axial direction of the linear ion trap, when arranging ion optical elements such as a quadrupole mass filter or a multipole type ion guide at the subsequent stage, both ion optical axes can be made coaxial, facilitating the arrangement of the ion optical elements.

[0070] (Second aspect) In the mass spectrometer according to the first aspect, the auxiliary electrode may be a multipole three-dimensional ion trap partial electrode obtained by cutting out a part of the electrodes constituting a multipole three-dimensional ion trap having the same number of poles as the ion trap composed of the plurality of rod electrodes.

[0071] That is, when the linear ion trap has a hexapole structure, a hexapole three-dimensional ion trap partial electrode may be used as the auxiliary electrode. By using such a multipole three-dimensional ion trap partial electrode, the action of the RF electric field formed at the ion emission side end of the rod electrodes is enhanced, reducing the leakage of ions other than the target m / z when ejecting ions according to m / z, and achieving a good mass scan.

[0072] (Third aspect) In the mass spectrometer according to the second aspect, the auxiliary electrode may be such that a missing portion is formed by hollowing out around the central axis in the multipole three-dimensional ion trap partial electrode.

[0073] For example, when using a hexapole 3D ion trap partial electrode as an auxiliary electrode, in principle, although it is possible to extract ions through the gap between two ring-shaped electrodes sandwiching the central axis, the size of the gap is not sufficient to allow a DC electric field of sufficient intensity to penetrate the ion capture space. On the other hand, according to the mass spectrometer described in Item 3, an opening of sufficient size can be provided between the two ring-shaped electrodes, so that a DC electric field of sufficient intensity can penetrate the ion capture space through the opening, and ions can be satisfactorily extracted outward from the ion capture space. Thereby, the ion extraction efficiency can be improved.

[0074] (Item 4) In the mass spectrometer according to any one of Items 1 to 3, the control unit can be configured to keep the DC electric field constant and change the RF electric field to sequentially discharge the ions captured in the ion capture space in the direction of decreasing mass-to-charge ratio.

[0075] To extract ions in order of mass-to-charge ratio, either the DC electric field or the RF electric field can be changed. However, since the energy imparted when ions are extracted is provided by the DC electric field, changing the DC electric field will cause the energy of the ions to vary depending on the mass-to-charge ratio. This is disadvantageous, for example, when it is desired to make ions discharged from a linear ion trap at different times reach a certain position simultaneously, as will be described later. On the other hand, according to the mass spectrometer described in Item 4, since the energy of the extracted ions is constant, the moving speed of the ions depends on the mass-to-charge ratio, which is convenient for adjusting the arrival position of the ions.

[0076] (Item 5) In the mass spectrometer according to any one of Items 1 to 4, a mass filter is arranged at the next stage of the linear ion trap section, The control unit can synchronously control the RF voltage and / or the DC voltage and the voltage applied to the mass filter so that the mass-to-charge ratio of the ions discharged from the ion capture space matches the mass-to-charge ratio of the ions passing through the mass filter.

[0077] In the mass spectrometer according to claim 5, ions with an m / z that can pass through the mass filter are discharged from the previous linear ion trap and introduced into the mass filter. In other words, ions with an m / z that cannot pass through the mass filter are retained in the linear ion trap until the time when the ions can pass through the mass filter. Therefore, according to the mass spectrometer according to claim 5, the ions excluded by the mass filter can be reduced, and the detection sensitivity can be increased by effectively using the generated ions.

[0078] (Claim 6) In the mass spectrometer according to any one of claims 1 to 4, the linear ion trap unit includes an inlet-side end cap electrode outside the ion-incident-side end opposite to the ion-emitting-side end of the plurality of rod electrodes. An inlet-side voltage generation unit that applies a voltage that allows ions to pass and a voltage that blocks the passage of ions to the inlet-side end cap electrode in a switchable manner. A pole number conversion type ion guide arranged in front of the linear ion trap unit, where the number of poles of the multipole field is different at the ion inlet end and the ion outlet end. Furthermore, during the period when the inlet-side voltage generation unit applies a voltage that blocks the passage of ions to the inlet-side end cap electrode, ions can be accumulated in the outlet region of the pole number conversion type ion guide.

[0079] In the mass spectrometer according to claim 6, although the introduction period during which ions can be introduced from the pole-changing type ion guide into the linear ion trap is limited, ions that have been transported by the pole-changing type ion guide during a period other than the introduction period are accumulated in the exit region of the ion guide and introduced into the linear ion guide during the next introduction period. Therefore, even when ions are continuously transported by the pole-changing type ion guide, the ions can be surely introduced into the linear ion trap without being discarded. As a result, the amount of ions used for mass spectrometry can be increased and the detection sensitivity can be improved. Also, it is less likely to miss the detection of ions that are generated only temporarily, and accurate analysis is possible.

[0080] (Claim 7) In the mass spectrometer according to any one of claims 1 to 4, the control unit adjusts the speed at which the RF voltage and / or the DC voltage is changed or the time required for the change so that all of the ions discharged from the linear ion trap unit or ions within a predetermined mass-to-charge ratio range among the discharged ions reach a predetermined position that is separated from the linear ion trap unit by a predetermined distance at the same time.

[0081] When ions are discharged from the linear ion trap in descending order of m / z, if the energy applied to the ions is the same, the ions with a larger m / z have a lower speed. Therefore, the relatively smaller m / z ions discharged later catch up with the relatively larger m / z ions discharged earlier. Thus, for example, if the DC voltage for ion extraction is kept constant and the speed of change of the RF voltage and the time required for the change are adjusted so that the RF electric field changes appropriately, all the ions can reach a certain position almost simultaneously. This is convenient when it is desired to start various ions with different m / z from substantially the same position. Specifically, it is convenient when injecting ions from the orthogonal acceleration section in an orthogonal acceleration time-of-flight mass separator or when it is desired to make ions start simultaneously from a certain position on the circular orbit in a Fourier transform mass separator.

[0082] (Item 8) In the mass spectrometer according to Item 7, an orthogonal acceleration time-of-flight mass separator is arranged at the subsequent stage of the linear ion trap unit, and the predetermined position can be a predetermined position within the orthogonal acceleration unit of the orthogonal acceleration time-of-flight mass separator.

[0083] According to the mass spectrometer described in Item 8, ions with a wide range of m / z can be ejected from the orthogonal acceleration unit almost simultaneously, so that the m / z range of the ions to be observed can be widened. In addition, the detection sensitivity can be improved by subjecting more ions to mass spectrometry.

[0084] (Item 9) In the mass spectrometer according to Item 7, a Fourier transform mass separator is arranged at the subsequent stage of the linear ion trap unit, and the predetermined position can be a predetermined position on the ion trajectory in the Fourier transform mass separator.

[0085] According to the mass spectrometer described in Item 9, ions with a wide range of m / z can be introduced into the Fourier transform mass separator, so that the m / z range of the ions to be observed can be widened. In addition, the detection sensitivity can be improved by subjecting more ions to mass spectrometry.

Explanation of Reference Numerals

[0086] 1... Ion supply unit 10... Ion source 11... Pole number conversion ion guide 2... Linear ion trap 20... Rod electrode group 200... Ion capture space 201, 202, 203, 204, 205, 206... Rod electrodes 21, 21A... 3D ion trap partial electrodes 210... Ion extraction aperture 211, 214... Ball-shaped electrodes 212, 213... Ring-shaped electrodes 212a, 213a... Defective parts 21B... RF gate electrode 22…Inlet-side end cap electrode 22a, 23a…Openings 23…Extraction electrode 3…Mass spectrometry and detection unit 31, 33…Quadrupole mass filter 32…Ion detector 34…Orthogonal acceleration time-of-flight mass separator 341…Orthogonal acceleration section 342…Acceleration electrode 343…Flight tube 344…Reflection electrode 35…Ion incident section 36…Multi-turn Fourier transform mass separation section 4…Control unit 5…Power supply unit 50…RF power supply unit 51…Inlet-side electrode DC power supply unit 52…Extraction electrode DC power supply unit C, C1…Ion optical axis C2…Orbit

Claims

1. A linear ion trap section including a plurality of rod electrodes arranged so as to surround a central axis, an auxiliary electrode provided outside or protruding from one ion-emitting side end of the plurality of rod electrodes and surrounding or sandwiching the central axis, and a draw electrode arranged further outside the auxiliary electrode; an RF voltage generator that applies an RF voltage to the plurality of rod electrodes and the auxiliary electrode to form an RF electric field in an ion trapping space surrounded by the plurality of rod electrodes and the auxiliary electrode; a draw voltage generator that applies a DC voltage to the draw electrode so that a DC electric field for ion extraction reaches the ion trapping space; a control unit that controls the RF voltage generator and the draw voltage generator, and discharges the ions from the ion trapping space in a direction along the central axis according to the mass-to-charge ratio by changing at least one of the RF voltage or the DC voltage in a state where the ions are confined in the ion trapping space; A mass spectrometer comprising the above.

2. The mass spectrometer according to claim 1, wherein the auxiliary electrode is a multipole three-dimensional ion trap partial electrode obtained by cutting out a part of the electrodes constituting a multipole three-dimensional ion trap having the same number of poles as a linear ion trap composed of the plurality of rod electrodes.

3. The mass spectrometer according to claim 2, wherein the auxiliary electrode has a cutout portion formed by cutting out around the central axis in the multipole three-dimensional ion trap partial electrode.

4. The mass spectrometer according to claim 1, wherein the control unit keeps the DC electric field constant and changes the multipole RF electric field to sequentially discharge the ions captured in the ion trapping space in a direction in which the mass-to-charge ratio decreases.

5. A mass filter is arranged at the next stage of the linear ion trap section, and the control unit synchronously controls the RF voltage and / or the DC voltage and the voltage applied to the mass filter so that the mass-to-charge ratio of the ions discharged from the ion trapping space matches the mass-to-charge ratio of the ions passing through the mass filter. The mass spectrometer according to claim 1.

6. The linear ion trap section includes an inlet-side end cap electrode outside the ion-incident side end opposite to the ion-emitting side end of the plurality of rod electrodes. An entrance - side voltage generation unit that applies a voltage that allows ions to pass through and a voltage that blocks ion passage to the entrance - side end - cap electrode in a switchable manner; An ion guide of a pole - number conversion type, arranged in front of the linear ion trap unit, having different numbers of poles of the multipole field at the ion entrance end and the ion exit end; The mass spectrometer according to claim 1, further comprising the above, and accumulating ions in the exit region of the pole - number conversion type ion guide during the period when the entrance - side voltage generation unit applies a voltage that blocks ion passage to the entrance - side end - cap electrode.

7. The control unit adjusts the speed at which the RF voltage and / or the DC voltage is changed or the time required for the change so that all of the ions discharged from the linear ion trap unit or ions within a predetermined mass - to - charge ratio range among the discharged ions reach a predetermined position that is a predetermined distance away from the linear ion trap unit simultaneously. The mass spectrometer according to claim 1.

8. A orthogonal acceleration time - of - flight mass separator is arranged at the subsequent stage of the linear ion trap unit; The mass spectrometer according to claim 7, wherein the predetermined position is a predetermined position within the orthogonal acceleration section of the orthogonal acceleration time - of - flight mass separator.

9. A Fourier - transform type mass separator is arranged at the subsequent stage of the linear ion trap unit; The mass spectrometer according to claim 7, wherein the predetermined position is a predetermined position on the ion trajectory in the Fourier - transform type mass separator.

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