Ion guidance and the mass spectrometer using it

Abstract

The present invention comprises a multipole ion guide comprising a plurality of multipole electrodes (21, 22) grouped into a first group and a second group forming a pseudopotential and a DC potential; and an RF power supply (303) applying an RF voltage to each of the plurality of multipole electrodes, and a DC power supply (302) applying different offset DC voltages to the multipole electrodes of the first group and the multipole electrodes of the second group, wherein only multipole electrodes of the first group are arranged in a first plane orthogonal to a central axis of the multipole ion guide (4), wherein the RF voltage and the different offset DC voltages are applied to the multipole electrodes (21, 22) such that the pseudopotential has a local minimum point in a second plane.in the multipole electrodes of both the first group and the second group are arranged and which is parallel to the first plane, wherein the local minimum point of the pseudopotential formed by the multipole electrodes of the first group and the local minimum point of the pseudopotential formed by the multipole electrodes of the second group are the same, and wherein in the second plane a synthetic potential of the pseudopotential and the DC potential has a local minimum point in a position that differs from a position of the local minimum point of the pseudopotential.

Description

Technical field

[0001] The present invention relates to an ion guide and a mass spectrometer in which this is used. State of the art

[0002] Ion guidance is widely used for transporting ions in mass spectrometers. Patent reference 1 discloses a multipole ion guidance system constructed from parallel rod electrodes of a multipole (quadrupole, hexapole, octupole, or the like). Patent reference 2 discloses an ion guidance system in which ions move between the ion guidance systems by overcoming a pseudopotential barrier between two ion guidance systems through a DC voltage potential. Patent reference 3 discloses an ion guidance system that forms a multipole ion guidance system by combining two independent multipole ion guidance systems. Furthermore, patent reference 4 describes an arrangement of rod electrodes in which several ion paths are formed that can be transitioned into one another. List of references to patent literature Patent Literature 1: US 7,256,395 B2 Patent literature 2: US 8,581,182 B2 Patent literature 3: US 2010 / 0176295 A1 Patent literature 4: US 2014 / 191 123 A1 Summary of the invention: Technical problem

[0003] The ion guidance described in patent literature 1 presents a problem in that the ions and the airflow cannot be separated from each other, since the airflow and the center of a pseudopotential of the ion guidance are essentially coaxial with each other.

[0004] In the ion guidance system described in patent literature 2, a pseudopotential barrier exists between the axes of two ion guides. Therefore, when moving ions from one ion guide to the other, it is necessary to apply a DC electric field that is sufficiently higher than the pseudopotential barrier. However, when a strong DC electric field is applied, the kinetic energy of the ions increases after overcoming the pseudopotential barrier, and ions are released towards the outer edge of the ion guide. This results in a low transmission efficiency for the ion guidance system. Furthermore, while the method described in patent literature 2 can be implemented in a high-order multipole ion guide or a ring-stack type ion guide, it is difficult to use the method in a low-order multipole, such as a quadrupole.Therefore, in comparison to a lower-order multipole ion guidance system, such as quadrupole ion guidance, there is also a problem in that the ability of the ions to converge is weak.

[0005] Patent literature 3 does not describe a process under the condition that an airflow is present. Furthermore, patent literature 3 does not describe the application of a DC voltage, which differs from that of another rod electrode, to a rod of a part of the rod electrode that forms the ion guide, and there is a problem in that the ions distribute themselves near a minimum point of the pseudopotential.

[0006] The present invention provides an ion guidance system that can separate an airflow and ions from each other and has a high ion transmission efficiency. Solution to the problem

[0007] The problem is solved by a multipole ion guidance system with the features of claim 1 and a mass spectrometer with the features of claim 3. Advantageous further developments and embodiments are specified in the dependent claims.

[0008] According to one aspect of the present invention, the first rod electrode set and the second rod electrode set are quadrupoles, and the single multipole ion guide is a hexapole.

[0009] Furthermore, according to another aspect of the present invention, the first rod electrode set and the second rod electrode set are quadrupoles, and the single multipole ion guide is an octupole. Advantageous effects of the invention

[0010] According to the present invention, it is possible to implement an ion guidance system that can separate the airflow and the ions from each other and has a high ion transmission efficiency.

[0011] In addition to the above description, problems, arrangements and effects will now be explained by means of the following description of the embodiments. Brief description of the drawings Fig. Figure 1 is a schematic sectional view illustrating an example arrangement of a mass spectrometer in which an ion guide of the present invention is used. Fig. Figure 2 is a schematic view of an airflow introduced through a fine bore. Fig. Figure 3 is a schematic view of the airflow introduced through a fine tube. Fig. Figure 4 is a schematic perspective view illustrating the entire ion guidance. Fig. Figure 5 is a schematic view showing the ion guidance in a Y-axis direction. Fig. Figure 6 is a schematic sectional view in a radial direction (YZ plane) of the ion guidance. Fig. Figure 7 is a schematic sectional view of a rod electrode. Fig. Figure 8 is a schematic view illustrating an example of an ion-guided power supply. Fig. Figure 9 is a view that illustrates a potential generated by the ion guidance. Fig. Figure 10 is a view illustrating the potential generated by the ion guidance. Fig. Figure 11 is a view illustrating the potential generated by the ion guidance. Fig. Figure 12 is a view that illustrates a synthetic potential. Fig. Figure 13 is a view illustrating a result of an ion trajectory simulation, taking into account the influence of the airflow. Fig. Figure 14 is a view illustrating a result of an ion trajectory simulation, taking into account the influence of the airflow. Fig. Figure 15 is a view illustrating the relationship between a mass spectrum of ions, an offset DC voltage, and an ion signal intensity. Fig. Figure 16 is a schematic perspective view illustrating the entire ion guidance. Fig. Figure 17 is a schematic view showing the ion guidance in the Y-axis direction. Fig. Figure 18 is a view illustrating an example of a segment DC voltage. Fig. Figure 19 is a view illustrating a sum of the segment DC voltage and the offset DC voltage. Fig. Figure 20 is a schematic perspective view illustrating the entire ion guidance. Fig. Figure 21 is a schematic view showing the ion guidance in the Y-axis direction. Fig. Figure 22 is a schematic sectional view in the radial direction (YZ plane) of the ion guidance. Fig. Figure 23 is a schematic perspective view illustrating the entire ion guidance. Fig. Figure 24 is a schematic view showing the ion guidance in the Y-axis direction. Fig. Figure 25 is a schematic sectional view in the radial direction (YZ plane) of the ion guidance. Description of embodiments

[0012] The embodiments of the present invention are described below with reference to the drawings. [Example 1]

[0013] Fig. Figure 1 is a schematic sectional view illustrating an example arrangement of a mass spectrometer in which an ion guide of the present invention is used.

[0014] Ions generated by an ion source 14, such as an electrospray ion source, an atmospheric pressure chemical ion source, an atmospheric pressure photoion source, or an atmospheric pressure matrix-assisted laser-desorbed ion source, are introduced into a vacuum chamber of the mass spectrometer by passing them through a fine bore 18 along with an airflow. The ions can be introduced directly from the fine bore 18 into a differential outlet section 12, or they can be introduced from a fine bore 10 via an intermediate vacuum chamber 17 into the differential outlet section 12, as shown in Fig. Figure 1 shows the following. An ion guide 4 is installed in the differential outlet section 12 for transporting the ions, and the ions are pumped out by a vacuum pump 15. The voltages are applied to the ion guide 4 by an ion guide power supply 300. As will be described later, ions 100 separated from the airflow 101 are introduced into a mass spectrometry section 13 via the ion guide 4, passing through a fine bore 11. The mass spectrometry section 13 is emptied by a vacuum pump 16. The pressure at which the ion guide of this example is operated is approximately 10,000 Pa to 10 -3 Pa. In particular, at 10,000 Pa to 10 Pa it is possible to effectively converge the ions, since the kinetic energy of the ions is cooled by the collision with neutral gaseous molecules.

[0015] Fig. Figure 2 is a schematic view of the airflow introduced through a fine bore 203 into a chamber 209 with a pressure p1 from a chamber 208 with a pressure p0, wherein in one case of a fine bore the thickness is sufficiently small with respect to a bore diameter d. As indicated by arrows in Fig. As shown in Figure 2, the direction of incidence 202 of the airflow corresponds to a perpendicular direction with respect to a flat surface provided with the fine bore 203. A barrel shock front 200 or a Mach disk 201 forms in accordance with a pressure difference before and after the fine bore 203, and the airflow proceeds in a straight line after the Mach disk with a diameter that is essentially the same as that of the Mach disk. A diameter D jet The Mach disk 201 is given by the following equation. DJst=0.412×d×p0p1

[0016] Fig. Figure 3 is a schematic view of the airflow introduced from chamber 208 at pressure p0 into chamber 209 via a fine tube 204, where, in one case of a fine tube, the thickness is sufficiently large relative to the bore diameter d. In this case, the Mach disk 201 is designed similarly to that used in the fine bore, and the airflow travels in a straight line after the Mach disk with a diameter that is essentially the same as that of the Mach disk. In this case, the direction 202 of the airflow corresponds to the central axis direction of the fine tube 204.

[0017] The Fig. Figures 4 to 7 are schematic views illustrating an example of the arrangement of the ion guidance of the example. Fig. Figure 4 is a schematic perspective view showing the entire ion guidance. Fig. Figure 5 is a schematic view showing the ion guidance in the Y-axis direction. Fig. Figure 6 is a schematic sectional view in a radial direction (YZ plane) of positions located in Fig. 4 are illustrated by (i), (ii) and (iii), and Fig. Figure 7 is a schematic sectional view of an XY plane of part of rod electrodes 21a and 21d and rod electrodes 22b and 22c.

[0018] A group 21 of rod electrodes on a side where the ions and airflow are introduced is defined as rod electrode set 1, and a group 22 of rod electrodes on a side from which the ions are released is defined as rod electrode set 2. In the example, rod electrode set 1 is formed from four rod electrodes 21a, 21b, 21c, and 21d, and rod electrode set 2 is formed from four rod electrodes 22a, 22b, 22c, and 22d. Furthermore, an end on a side where the ions and airflow 26 are introduced into rod electrode set 1 is defined as an ion guide inlet 24, and an end on a side from which the ions are released in rod electrode set 2 is defined as an ion guide outlet 25. The shape of the rod electrode can be a column-like shape, as shown in Fig. Figure 4 illustrates this, and it can be in the shape of a prism or a polygon. The rod electrodes 21d, 22c, 21a, and 22b have a shape such as a semicircular column, so that the group of rod electrodes 21d and 22c and the group of rod electrodes 21a and 22b approximately form a column or a prism. The distances between the rod electrode 21d and the rod electrode 22c, as well as between the adjacent rod electrodes 21a and 22b, are approximately 0.1 mm to 2 mm.

[0019] The central axis of electrode set 1 and the central axis of electrode set 2 are parallel to each other, but offset by a specific distance in the Z-axis direction. Furthermore, electrode set 1 and electrode set 2 overlap in the longitudinal direction over a portion of their area, and in the area where the sets overlap, as shown in Fig. Figure 6 illustrates that the rod electrodes of rod electrode set 1 and rod electrode set 2 are combined, forming a single multipole ion guide.

[0020] The symbols “+” and “-” in Fig. Figure 6 indicates the phase of an RF voltage applied to the rod electrode by the ion-guide power supply 300. RF voltages with the same phase, amplitude, and frequency are applied to rod electrodes with the same reference numbers. Within the same set of rod electrodes, the RF voltages are applied such that the opposing rod electrodes have the same phase and the adjacent rod electrodes have opposite phases. Furthermore, in different sets of rod electrodes, RF voltages with the same phase, amplitude, and frequency are applied to rod electrodes 21d and 22c, as well as to rod electrodes 21a and 22b, which are adjacent to each other.In this way, applying the voltages does not create a potential difference of the RF voltage between the rod electrodes 21d and 22c - where the distance between the electrodes is small - and the rod electrodes 21a and 22b, and an electrical discharge can be prevented.

[0021] In addition to the RF voltages, the electrode array is also subjected to offset DC voltages. The same offset DC voltages are applied to the electrode in the same array. These offset DC voltages are applied in such a way as to create an electric field that moves the ions of the sample being measured from electrode array 1 to electrode array 2. In other words, when measuring positive ions, an offset DC voltage with a higher potential than that of electrode array 2 is applied to electrode array 1, and when measuring negative ions, an offset voltage with a lower potential than that of electrode array 2 is applied to electrode array 1.If the difference in DC voltage offset between electrode set 1 and electrode set 2 is set to 0.1 V to 100 V, it is possible to efficiently move the ions from the side of electrode set 1 to the side of electrode set 2.

[0022] As in Fig. As illustrated in Figure 5, a neutralizing electrode 23 is arranged at a terminal end on the ion guide inlet side of the rod electrode set 2, and here it is also possible to reduce ion loss when applying the DC voltages that push the ions to the ion guide outlet 25. When the positive ions are measured, the voltages applied to the neutralizing electrode 23 are set higher than the offset DC voltages applied to the rod electrode set 2, and when the negative ions are measured, they are set lower than the offset DC voltages applied to the rod electrode set 2.

[0023] Fig. Figure 8 is a schematic view illustrating an example of the ion guidance power supply. The ion guidance power supply 300 is formed from a DC power supply 301, which generates the offset voltages of the rod electrode set 1, a DC power supply 302, which generates the offset voltages of the rod electrode set 2, and an RF power supply 303, which generates two-phase RF voltages that are 180 degrees out of phase with each other, and applies the offset voltages or RF voltages to each of the rod electrodes.

[0024] As in the Fig. 4 and Fig. As illustrated in Figure 5, the ion guidance of the example is divided into three areas 1 to 3. The positional relationship in the radial direction (YZ plane) of groups 21 and 22 of the rod electrodes is different in each of the areas, and the resulting pseudopotential is also different in each case.

[0025] In region 1, four rod electrodes from rod electrode set 1 are arranged in a position near a vertex of a true square, forming a quadrupole ion guide. The pseudopotential in the radial direction (YZ plane) is generated by the RF voltages applied to the four rod electrodes of rod electrode set 1.

[0026] The pseudopotential is obtained via the following equation as the potential that yields a force acting on the ions as a time average in a case where an electric field is applied that changes at a speed that the motion of the ions cannot follow. Φ'=Ze4mΩ2E¯2

[0027] Here, m represents the mass of the ions, Z represents the ion valence, e is the amount of electricity, Ω represents the frequency of the RF voltages, and E denotes an electric field.

[0028] Fig. Figure 9 is a view illustrating the potential generated by the ion guidance, and Fig. Figure 9(A) is a view illustrating a pseudopotential in the radial direction (YZ plane) of region 1. Additionally, Fig. 9B a view in which the height of the potential is plotted in relation to the position in the Z-direction on the axis shown in Fig. Figure 9(A) is illustrated by a wavy line. The pseudopotential of the quadrupole is a quadratic function, where the minimum point is considered to be the point at which the electric field generated by the RF voltages has its minimum. The central axis of the ion guidance is defined by a line connecting the minimum points 50 of the pseudopotential in the radial direction (YZ plane). In region 1, the ions cannot move between the rod electrode sets because a pseudopotential barrier exists between rod electrode set 1 and rod electrode set 2.

[0029] In area 2, the rod electrode set 1 and the rod electrode set 2 overlap each other. Furthermore, it widens, as shown in Fig. Figure 7 illustrates the distance between the group of rod electrodes 21a and 22b and the group of rod electrodes 21d and 22c from the position of area 1 and area 3, as shown in Fig. As illustrated in Figure 6, a hexapol-ion configuration is formed in which the group of rod electrodes 21a and 22b, the rod electrode 21b, the rod electrode 21c, the group of rod electrodes 21d and 22c, the rod electrode 22d, and the rod electrode 22a are arranged at the apex positions of a substantially regular hexagon. Since the RF voltages with the same phase, amplitude, and frequency are applied to the group of rod electrodes 21d and 22c and the group of rod electrodes 21a and 22b respectively, it is possible, taking the pseudopotential into account, to consider the group of rod electrodes 21a and 22b and the group of rod electrodes 21d and 22c as single electrodes.

[0030] Fig. Figure 10 is a view that represents the potential generated by the ion guidance, and Fig. Figure 10(A) is a view showing the pseudopotential in the radial direction (YZ plane) of region 2. Additionally, Fig. 10(B) a view in which the height of the potential is plotted with respect to the Z-coordinate on the axis defined by the wavy line in Fig. Figure 10(A) illustrates this. When the hexapole is formed by combining rod electrode set 1 and rod electrode set 2, the single pseudopotential is formed with the minimum point near the center of the area surrounded by the rods. As can be seen from Fig. 10(B) can detect that there is no pseudopotential barrier between the rod electrode set 1 and the rod electrode set 2, and the ions can move freely.

[0031] The DC potential in the radial direction (YZ plane) is formed by the difference in the offset DC voltage applied to the rod electrode set 1 and the rod electrode set 2. Fig. Figure 11 is a view illustrating the potential generated by the ion guidance, and Fig. Figure 11(A) is a view illustrating the DC potential in the radial direction (YZ plane) of region 2. Furthermore, Fig. 11 (B) a view in which the height of the potential is shown in relation to the position in the Z-direction in the axis defined by a wavy line in Fig. Figure 11(A) illustrates this. The DC potential exerts a force that moves the ions in the Z-direction (from electrode set 1 to electrode set 2). In this example of ion guidance, the DC potential can be efficiently generated by applying different offset DC voltages to electrode set 1 and electrode set 2. As described in patent literature 3, the DC potential has little influence on the interior of the ion guidance system because the DC potential generated by an electrode other than the electrode, for example, an electrode inserted into a void within the electrode, is blocked by the electrode. Furthermore, this potential can also lead to ion loss, as the potential is disturbed near the electrode.

[0032] Fig. Figure 12 is a view illustrating a synthetic potential where the pseudopotential and the DC potential are added together by the RF voltages. Fig. Figure 12(A) illustrates the synthetic potential in the YZ plane, and Fig. Figure 12(B) illustrates the synthetic potential along the Z-axis. A minimum point 51 of the synthetic potential lies further on the side of the rod electrode set 2 than the minimum point of the pseudopotential. Furthermore, the minimum point 51 of the synthetic potential is located further on the side of the rod electrode set 2 than an incidence position 52 of the ions in region 2 of the ion guidance system and acts such that the ions guided by the rod electrode set 1 in region 1 are moved in region 2 towards the side of the rod electrode set 2.

[0033] A connecting element between region 2 and regions 1 and 3 can be designed to be curved at a slight angle, even in an arrangement that is curved at approximately 90 degrees. In the case of a slight angle of curvature, the potential in the radial direction of the connecting element changes continuously from the potential of a connection source to the potential of a connection tip. Furthermore, as described in the Fig. 4 and Fig. Figure 5 illustrates that when the rod electrode of the rod electrode set 1 is located at the inlet of region 3, an electric field is created in which the ions are moved from region 2 to region 3, so that the ions can be efficiently transported from region 2 to region 3.

[0034] In region 3, the distance between the group of rod electrodes 21a and 22b and the group of rod electrodes 21d and 22c narrows from the position of region 2, and four rod electrodes of rod electrode set 2 are arranged in positions near the tips of a true square. Similar to region 1, the pseudopotential is formed by four rod electrodes of rod electrode set 2, and the ions converge at the central axis of rod electrode set 2 in region 3. In a case of the pseudopotential formed by the quadrupole, as in Fig. As illustrated in Figure 9(B), the effect of ion convergence along the axis is high because the potential slope near the minimum point is greater than in high-order multipole ion guides or ring-stacked ion guides. As the effect of ion convergence increases, the effect of ions flowing out through the fine bore 11 at a rear end of the ion guide is amplified, and a measurement with high sensitivity becomes possible.

[0035] The Fig. 13 and Fig. Figure 14 shows the result of an ion trajectory simulation, taking into account the influence of the airflow in relation to the flow of ions in the ion guidance of the example. Fig. Figure 13(A) illustrates a trajectory 30 of the ions with a viewing direction in the Y-axis direction, and Fig. Figure 13(B) illustrates a flow of 31 neutral particles contained in the airflow, viewed along the Y-axis. Furthermore, it illustrates Fig. 14(A) the trajectory of the ions with a viewing direction in the X-axis direction, and Fig. Figure 14(B) illustrates a distribution area of ​​the ions and the neutral particles at the outlet of the ion guide.

[0036] The ions are introduced through the fine bore or the fine tube into the differential outlet chamber 12, in which the ion guide 4 is installed. At the outlet of the fine bore or the fine tube, the Fig. 2 or Fig. The airflow shown in Figure 3 is generated. The ions are introduced along the airflow for ion guidance (Figure 4). The airflow enters region 1 essentially coaxially with the central axis of the rod electrode set 1. Since the ions enter region 1 coaxially with the central axis of the rod electrode set 1, the ions flow towards the vicinity of the central axis 50 of the pseudopotential of Fig. 9(A), and the ions can be efficiently introduced into the ion guide 4. Furthermore, if the Mach disk of is affected by the force that causes the ions to converge at the central axis of the ion guide, Fig. 2 on the inside of the pseudopotential of the rod electrode set 1 of Fig. When 4 is generated, the loss caused by diffusion near the Mach disk is prevented, and the transmission efficiency of the ion guidance is improved. The ions converge at the central axis of the quadrupole ion guidance formed by the rod electrode set 1.

[0037] The ions move along the airflow from area 1 to area 2. As in Fig. As illustrated in Figure 12, position 52, where the ions enter region 2, lies near a line of extension of the central axis of the quadrupole ion guidance formed by the rod electrode set 1 in region 1. The ions move towards the side of the rod electrode set 2 where the minimum point 51 of the Fig. The synthetic potential shown in 12 is present, as in Fig. 13(A) and Fig. 14(A) illustrates this by the difference in the offset DC voltage of rod electrode set 1 and rod electrode set 2. Comparing the DC potential and "Equation 2" of the pseudopotential, the DC potential has a greater force transmitted to the ions at the same applied voltages. Therefore, using the DC potential, it is possible to efficiently remove the ions from the airflow, even at low applied voltages. Since the neutral particles or liquid droplets in the airflow are unlikely to be influenced by the electric field, they move in a straight line along the x-axis, as shown in Fig. Figure 13(B) illustrates this. In this way, by using the DC potential formed by the difference in the offset DC voltage of rod electrode set 1 and rod electrode set 2, it is possible to separate the distribution of the neutral particles contained in the ions and the airflow from each other.

[0038] In region 2, the ions moving towards the side of the rod electrode set 2 are introduced into the quadrupole ion guide formed by the rod electrode set 2 of region 3. In region 3, there is no influence on the convergence caused by ion diffusion through the airflow and the high ion density in the airflow, as the airflow and the ions are separated. Therefore, the ions are expected to converge along the central axis of the ion guide. If the ions converge in a narrow region at the outlet of the ion guide, the permeability of the fine bore 11 increases, resulting in high sensitivity.

[0039] Fig. Figure 14(B) shows a distribution 34 of neutral particles and a distribution 33 of ions contained in the airflow 25 at the outlet 25 of the ion guide. Since the airflow enters the area 1 of the rod electrode set 1 essentially coaxially with the central axis, the neutral particles contained in the airflow are distributed along the extension line of the central axis of the rod electrode set 1. The ions are distributed near the central axis of the rod electrode set 2. Therefore, by using the ion guide of the example, it is possible to separate the ions such that the distribution 34 of neutral particles and the distribution 33 of ions contained in the airflow at the ion guide outlet 25 do not overlap.

[0040] Fig. Figure 15(A) illustrates a mass spectrum of reserpine (m / z = 609) measured using the ion guidance of the example. Furthermore, Fig. 15(B) A view in which the ion signal intensity of reserpine is plotted against the difference in the offset DC voltage of rod electrode set 1 and rod electrode set 2. In a case where the difference in the offset DC voltage of rod electrode set 1 and rod electrode set 2 is 0 V, the ions are almost not observed. This is presumably because the ions along the Fig. Figure 13(B) illustrates that the airflow is linear. The ion signal intensity gradually increases as the difference in the DC offset voltage between electrode set 1 and electrode set 2 increases, and becomes substantially constant when the voltage is greater than or equal to 4 V. This illustrates that, when the DC offset voltage is greater than or equal to 4 V, essentially all ions move towards electrode set 2 and are carried out along the central axis of electrode set 2.

[0041] By separating the airflow and the ion distribution using the ion guide of the example, and by introducing the ions to the mass spectrometry section by removing only the components within the ion distribution area, the flow rate of the gas introduced to the mass spectrometry section via the ion guide decreases, and the load on the vacuum pump is reduced. Consequently, it is possible to use a vacuum pump with a lower delivery rate, smaller size, and lower cost. Furthermore, this prevents neutral particles and liquid droplets contained in the airflow from entering the ion path of the mass spectrometry section, thus improving the robustness of the instrument.Since the liquid droplets cause noise, the signal-to-noise ratio (S / N) is also improved by preventing the liquid droplets from entering. [Example 2]

[0042] Both Fig. 16 and Fig. Figure 17 shows arrangement views illustrating another example of the ion guidance of the present invention. Fig. Figure 16 is a schematic perspective view illustrating the entire ion guidance, and Fig. Figure 17 is a schematic view showing the ion guidance in the Y-axis direction.

[0043] The ion guidance in this example differs from that in Example 1 in that group 21 and group 22 of the rod electrodes are subdivided into multiple segments along the longitudinal (X-axis) direction of the ion guidance. Each of the rod electrodes in a first and a second set of rod electrodes is subdivided into multiple segments, using the same position along the longitudinal direction as the subdivision point, and the segments are electrically isolated from each other. One method of electrical isolation can be to provide a void while separating adjacent segments, or it can be to insert the insulating material, such as a segment, between the adjacent segments.The drawings illustrate an example where groups 21 and 22 of the rod electrodes are each divided into four segments, although the number of segments may be two or more.

[0044] Group 21 of the rod electrodes and group 22 of the rod electrodes are subdivided by the YZ plane at the same X-coordinate, and only the rod electrode contained in the same segment lies on the YZ plane at any X-coordinate. In addition to the RF voltage and the offset DC voltage, a segment DC voltage is applied independently to each of the segments with respect to group 21 of the rod electrodes and group 22 of the rod electrodes. Fig. Figure 18 is a view illustrating an example of segmented DC voltage. The same segmented DC voltage is applied to each rod electrode contained in the same segment. When measuring the positive ions, if the segmented DC voltage is set to gradually decrease as it approaches the ion guide outlet from the ion guide inlet, an electric field is generated in which the ions are accelerated in the X-axis direction, and, provided the pressure is high, the ions can be prevented from remaining inside the ion guide.

[0045] The RF voltage and the offset DC voltage are applied similarly to Example 1. In other words, the RF voltages are applied with the same phase, amplitude, and frequency to all segments with reference to the rod electrode, which have the same reference numbers as those of the Fig. 6. In addition, the same offset DC voltages are applied to the group of rod electrodes contained in the same rod electrode sets. Fig. Figure 19 is a view illustrating the sum of the segment DC voltage and the offset DC voltage. Fig. 19 is the DC voltage applied to each of the segments of the rod electrode set 1, 62 is the DC voltage applied to each of the segments of the rod electrode set 2, and 60 is a difference of the offset DC voltage.

[0046] Here, the relative potential when viewed from the minimum point of the pseudopotential on the YZ plane of each region is the same as that of Example 1. Therefore, similar to Example 1, in region 1 the ions converge at the central axis of electrode set 1, in region 2 the ions are separated from the airflow and moved from the side of electrode set 1 to the side of electrode set 2, and in region 3 the ions can converge at the central axis of electrode set 2. In this way, it is possible to obtain practically the same functions as those of Example 1, even in a case where the electrodes are divided into segments.Accordingly, even in the arrangement where the rod electrodes are divided into segments in the longitudinal direction (X-axis direction) of the ion guidance, as described in the example, the electrodes of the segments that run continuously in the longitudinal direction can be referred to as a single rod electrode. [Example 3]

[0047] Both Fig. Figures 20 to 22 are arrangement views illustrating a further example of the ion guidance of the present invention. Fig. Figure 20 is a schematic perspective view illustrating the entire ion guidance. Fig. Figure 21 is a perspective view showing the ion guidance in the Y-axis direction, and Fig. Figure 22 is a sectional view in the radial direction (YZ plane) of the positions shown in Fig. 20 are illustrated by (i), (ii) and (iii). The shape of the rod electrode can be, as shown in Fig. Figure 20 illustrates a shape that is similar to a column, as well as the shape of a prism or a polygon.

[0048] Group 21 of the rod electrodes is defined as rod electrode set 1 on the side where the ions and airflow are introduced, and group 22 of the rod electrodes is defined as rod electrode set 2 on the side where the ions are discharged. The same offset DC voltage is applied to the rod electrodes contained in the same rod electrode set. The symbols “+” and “-” in Fig. 22 specify the phase of the RF voltage, and the RF voltages with the same phase, amplitude and frequency are applied to the rod electrodes that have the same reference numbers.

[0049] In region 1, the quadrupole ion guidance is formed by four rod electrodes 21a, 21b, 21c, and 21d of rod electrode set 1. In region 2, the distance between rod electrodes 21a and 21d of rod electrode set 1 and rod electrodes 22b and 22c of rod electrode set 2 widens from the position of region 1, and the rod electrodes each approach the positions of the apex of a substantially regular octagon, as shown in Fig. Figure 22 illustrates this. By combining rod electrode set 1 and rod electrode set 2 to form the octupole, a single pseudopotential is created with its minimum point near the center of the area surrounded by the rods. There is no pseudopotential barrier between rod electrode set 1 and rod electrode set 2, and the ions can move freely. When the offset DC voltage is applied such that an electric field is created in which the ions of the sample being measured are moved from rod electrode set 1 to rod electrode set 2, it is possible that in area 2 the ions are removed from the airflow and moved from the side of rod electrode set 1 to the side of rod electrode set 2. The ions that have moved to the side of rod electrode set 2 are introduced into area 3.In region 3, the quadrupole ion guide is formed from four rod electrodes 22a, 22b, 22c, and 22d of rod electrode set 2, and the ions converge at the central axis of the quadrupole ion guide. This example describes an octupole, but a multipole with more than 8 poles, such as 10, 12, 16, or 20, can also be used.

[0050] In this example, the price is lower compared to that of Example 1 because it is also possible to use inexpensive, column-shaped rod electrodes 21a, 21d, 22b, and 22c, which are easy to process. In a high-order multipole, such as an octupole, the gradient near the center of the pseudopotential is weak, so the ions are distributed over a wide area in the radial direction, and an ion loss is likely to occur at modification sites from the multipole to the quadrupole. [Example 4]

[0051] The Fig. Figures 23 to 25 are arrangement views illustrating a further example of the ion guidance of the present invention. Fig. Figure 23 is a schematic perspective view showing the entire ion guidance. Fig. Figure 24 is a schematic view showing the ion guidance in the Y-axis direction and Fig. Figure 25 is a sectional view in the radial direction (YZ plane) of the positions shown in Fig. 23 are illustrated by (ii) and (iii).

[0052] In the ion guidance of this example, there is no part that corresponds to area 1 of example 1, and as in Fig. As illustrated in Figure 25, the airflow 26 containing the ions enters parallel to the central axis of region 2 of the ion guide, within the area surrounded by the rod electrodes 21a, 21b, 21c, and 21d of the rod electrode set 1 of region 2. The arrangement, the applied voltage, and the behavior of the ions and the airflow in regions 2 and 3 are similar to those of Example 1.

[0053] In this example, the setup is advantageous because it is simpler and less expensive compared to the setup in Example 1. However, the transmission efficiency of the ion guidance is inherently lower than that of the setup in Example 1, since there is no part of region 1 in which the ions converge. Aspects of registration

[0054] A first aspect concerns an ion guide comprising: a first set of rod electrodes having a first central axis into which ions and an air stream are introduced; a second set of rod electrodes having a second central axis located at a distance from the first central axis, from which the ions are emitted; and a power supply applying voltages to the first set of rod electrodes and the second set of rod electrodes, wherein the first set of rod electrodes and the second set of rod electrodes have a region in which the sets overlap longitudinally and form a single multipole ion guide by being combined in the region in which the sets overlap, wherein the first set of rod electrodes and the second set of rod electrodes are connected to the first set of rod electrodes and the second set of rod electrodes respectively.The second set of rod electrodes is supplied with different offset DC voltages from the power supply, and the offset DC voltage forms a DC potential to move the ions to the second set of rod electrodes into the area where the sets overlap, guided by the ions from the first set of rod electrodes.

[0055] A second aspect concerns ion guidance according to the first aspect, wherein in the single multipole ion guidance, a distance between rod electrodes of a part of the first rod electrode set becomes wider than the side into which the ions and the airflow are introduced, and a distance between rod electrodes of a part of the second rod electrode set becomes wider than the side from which the ions are emitted.

[0056] A third aspect concerns an ion guidance according to the first aspect, wherein the first set of rod electrodes and the second set of rod electrodes are quadrupoles, and the single multipole ion guidance is a hexapole.

[0057] A fourth aspect concerns an ion guidance according to the first aspect, wherein the first set of rod electrodes and the second set of rod electrodes are quadrupoles, and the single multipole ion guidance is an octupole.

[0058] A fifth aspect concerns ion guidance according to the first aspect, wherein the distribution center of neutral particles contained in the airflow and the distribution center of ions at an outlet of the ion guidance are different.

[0059] A sixth aspect concerns ion guidance according to the first aspect, wherein the difference in the offset DC voltage of the first set of stick electrodes and the second set of stick electrodes is 0.1 V to 100 V.

[0060] A seventh aspect concerns an ion guidance according to the first aspect, wherein the first rod electrode set and second rod electrode set are divided into several segments, with the same position in the longitudinal direction being considered as the subdivision point, and in each of the segments a segment DC voltage is applied by the power supply, which generates an electric field in which the ions are accelerated in an outlet direction.

[0061] An eighth aspect concerns a mass spectrometer, comprising: an ion source that generates ions; a mass spectrometry section that performs mass spectrometry with respect to the ions; an ion guide that transports the ions generated by the ion source to the mass spectrometry section; and the ion guide according to the first aspect as ion guide. Reference symbol list 4 ion guide 10, 11 Fine drilling 12 Differential outlet section 13 Mass Spectrometry Section 14 ion source 17 intermediate vacuum chambers 18 Fine drilling 21 to 22 rod electrode set 23 Neutralizing electrode 24 ion guidance entry 25 ion guide outlet 27 Release position of the ions 30 ion trajectory 33 Distribution area of ​​the ions 50 Central axis of the quadrupole ion guidance 51 Minimum point of the synthetic potential 91 Distribution of ions 100 ions 101 Airflow 200 Barrel Shock Front 201 Mach disc 203 Direction of airflow 204 fine tube 300 ion-guided power supply

Claims

[1] Multipole ion guidance (4) comprising: a plurality of multipole electrodes (21a, 21b, 21c, 21d, 22a, 22b, 22c, 22d) grouped into a first group (21) and a second group (22) forming a pseudopotential and a DC potential; and an RF power supply (303) that applies an RF voltage to each of the plurality of multipole electrodes (21a, 21b, 21c, 21d, 22a, 22b, 22c, 22d), and a DC power supply (301, 302) that applies different offset DC voltages to the multipole electrodes (21a, 21b, 21c, 21d) of the first group (21) and the multipole electrodes (22a, 22b, 22c, 22d) of the second group (22), wherein only multipole electrodes (21a, 21b, 21c, 21d) of the first group (21) are arranged in a first plane orthogonal to a central axis of the multipole ion guide (4) and form a pseudopotential there, wherein in a second plane, which is parallel to a first plane and in which multipole electrodes (21a, 21b, 21c, 21d, 22a, 22b, 22c, 22d) of both the first group (21) and the second group (22) are arranged, the RF voltage is applied to the multipole electrodes (21a, 21b, 21c, 21d, 22a, 22b, 22c, 22d) such that they together form a single pseudopotential with a local minimum point, wherein in the second plane a DC potential is generated by the different offset DC voltages, which is superimposed on the pseudopotential, such that a resulting synthetic potential has a local minimum point (51) in a position which is shifted relative to the local minimum point of the pseudopotential solely in the direction of the second group (22) of multipole electrodes (22a, 22b, 22c, 22d), and wherein only multipole electrodes (22a, 22b, 22c, 22d) of the second group (22) are arranged in a third plane orthogonal to a central axis of the multipole ion guide (4) and form a pseudopotential there. [2] Multipole ion guidance (4) according to claim 1, wherein at least two electrodes (21a, 21d) of the first group (21) and at least two electrodes (22b, 22c) of the second group (22) have a semicircular shape in cross-section, and wherein the semicircular electrodes (21a, 21d) of the first group (21) are oriented towards the semicircular electrodes (22b, 22c) of the second group (22) in a second area (2) encompassing the second plane, in order to form essentially column-shaped electrodes there. [3] Mass spectrometer, comprising: an ion source (14) for generating ions; a mass spectrometry section (13) for performing mass spectrometry with respect to the ions; an ion guide (4) for transporting the ions generated by the ion source (14) to the mass spectrometry section (13); and the multipole ion guidance (4) according to one of claims 1 to 2 as ion guidance (4).

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