Magnetic field change device, sample analysis system, and sample analysis method

Abstract

In order to reduce the size of a sample analysis system, the present invention is provided with: a magnet (101) that applies a magnetic field to magnetic particles (P) bonded to a labeling substance; a magnetic flux guidance unit (120) composed of a soft magnetic material; and a magnetic field change unit (110) that changes a magnetic field around the magnet (101). The magnetic flux guidance unit (120) has a first surface facing the N-pole of the magnet (101) and a second surface facing the S-pole of the magnet (101). The first surface and the second surface are connected by a member of the magnetic flux guidance unit (120). The magnetic field change unit (110) changes the magnetic field by creating a state in which the N-pole faces the first surface and a state in which the S-pole faces the second surface.

Description

Magnetic field changing device, sample analysis system, and sample analysis method

[0001] The present invention relates to a magnetic field changing device, a sample analysis system, and a sample analysis method.

[0002] Sample analyzers used for immunological analysis, etc., use a magnetic field to capture magnetic particles bound to the substance (sample) to be measured, and then analyze the components in the sample by measuring the amount of light emitted by the chemiluminescent reaction. The photodetector that measures the amount of light emitted by the chemiluminescent reaction is affected by the magnetic field. Therefore, a large magnetic field (strong magnetic field) is required when capturing magnetic particles, and a small magnetic field (weak magnetic field) is required when measuring the amount of light emitted. For this reason, sample analyzers are equipped with a magnetic field switching device that switches the magnetic field on and off. A permanent magnet is used in the magnetic field switching device to generate the strong magnetic field. The magnetic field switching is achieved by a moving unit that moves the permanent magnet closer and further away.

[0003] For example, Patent Document 1 discloses a technique for such a sample analyzer. Patent Document 1 discloses an automatic analyzer comprising: a flow chamber through which a fluid containing magnetic particles bound to a labeling substance flows from a fluid inlet to a fluid outlet; magnetic trapping means for trapping the magnetic particles in the fluid introduced into the flow chamber, wherein the magnetic trapping means includes a magnet for applying a magnetic field; a working electrode and a counter electrode for applying a voltage to the magnetic particles trapped by the magnetic trapping means to cause them to emit light; a photodetector element for detecting the emission of light from the labeling substance on the magnetic particles trapped in the flow chamber; and restricting means for restricting the region in which the photodetector element detects the emission of light so as to detect the emission of light from the labeling substance on some of the magnetic particles trapped by the magnetic trapping means on the upstream side, the restricting means being a working electrode formed so as to be exposed to a portion of the upstream side of the inner wall of the flow chamber where the magnetic particles are trapped by the magnetic trapping means (see claim 1).

[0004] Patent No. 6239243

[0005] The photodetector that measures the amount of light emitted is subject to a decrease in sensitivity due to the influence of a magnetic field, so a low magnetic field environment is required when measuring the amount of light emitted. For this reason, the magnetic field switching device is equipped with an arm that increases the distance between the photodetector and the magnet.

[0006] However, in the conventional configuration, a large volume is required over the range of motion of the arm, which leads to an increase in the size of the detection unit and restrictions on the arrangement of the flow channels.

[0007] The present invention has been made in view of the above background, and an object of the present invention is to make a sample analysis system smaller.

[0008] In order to solve the above-mentioned problems, the present invention provides a magnet that applies a magnetic field to magnetic particles bound to a labeled substance, a magnetic flux guider made of a soft magnetic material, and a magnetic field changer that changes the magnetic field around the magnet, wherein the magnetic flux guider has a first surface facing the north pole of the magnet and a second surface facing the south pole of the magnet, the first surface and the second surface being connected by a member of the magnetic flux guider, and the magnetic field changer changes the magnetic field by bringing the north pole into a state facing the first surface and the south pole into a state facing the second surface. Other solutions will be described as appropriate in the embodiments.

[0009] According to the present invention, the sample analysis system can be made smaller.

[0010] 1 is a diagram showing a schematic configuration of a sample analysis system according to a first embodiment. FIG. 2 is an enlarged schematic view of a magnetic field change device and a detection unit. FIG. 3 is a functional block diagram showing the configuration of a controller used in the sample analysis system according to this embodiment. FIG. 4 is a schematic view showing a state in which a magnetic field is applied to a particle capture region. FIG. 5 is a schematic view showing a state in which a strong magnetic field is not applied to a particle capture region. FIG. 6 is a diagram showing the positional relationship between a magnetic flux guiding unit and a magnet in a magnetic field-on state. FIG. 7 is a diagram showing the distribution of the magnitude of the measured magnetic flux density (part 1). FIG. 8 is a diagram showing the positional relationship between a magnetic flux guiding unit and a magnet in a magnetic field-off state. FIG. 9 is a diagram showing the distribution of the magnitude of the measured magnetic flux density. FIG. 10 is a diagram showing analysis conditions. FIG. 11 is a diagram showing the relationship between the position of the magnet and the magnetic flux density. FIG. 12 is a diagram showing a specific example of a magnetic field change device according to the first embodiment. FIG. 13 is a diagram showing a specific example of a magnetic field change device according to the first embodiment. FIG. 14 is a diagram showing movement of the magnet by the magnetic field change device in a comparative example. FIG. 15 is a diagram showing movement of the magnet by the magnetic field change device in this embodiment. FIG. 16 is a flowchart showing the procedure of a sample analysis method performed by a sample analysis system. FIG. 17 is a diagram showing the configuration of a magnetic field change device in a second embodiment. FIG. 2 is a diagram (part 2) showing the configuration of a magnetic field change device in the second embodiment. FIG. 1 is a diagram (part 1) showing the configuration of a magnetic field change device in the third embodiment. FIG. 2 is a diagram (part 2) showing the configuration of a magnetic field change device in the third embodiment. FIG. 1 is a diagram (part 1) showing the configuration of a magnetic field change device in the fourth embodiment. FIG. 2 is a diagram (part 2) showing the configuration of a magnetic field change device in the fourth embodiment. FIG. 3 is a diagram (part 3) showing an example configuration of a magnetic flux change device in the first embodiment. FIG. 4 is a diagram (part 1) showing an example configuration of a magnetic flux change device in the first embodiment. FIG. 5 is a diagram (part 2) showing an example configuration of a magnetic flux change device in the fourth embodiment.

[0011] Next, a mode for carrying out the present invention (referred to as an "embodiment") will be described in detail with reference to the drawings as appropriate.

[0012] 1 is a diagram showing a schematic configuration of a sample analysis system 1 according to a first embodiment. FIG. 2 is an enlarged schematic view of a magnetic field change device 100 and a detection unit 200.

[0013] In this embodiment, an immunoanalyzer will be described as an example of a sample analysis system 1. This embodiment is not limited to immunoanalysis, and can be applied to any sample analysis system 1 that captures magnetic particles P by changing the magnitude of a magnetic field (distribution of magnetic flux density). In other words, the sample analysis system 1 shown in this embodiment can be used for analyzers for DNA, biochemistry, etc. Furthermore, the embodiments described below are not limited to shapes, dimensions, numbers, etc., and can be modified within the scope of the gist thereof. Multiple embodiments, including those described below, can be combined. Furthermore, part of the configuration of one embodiment can be replaced with the configuration of another embodiment.

[0014] In this embodiment, the magnitude of the magnetic field is expressed numerically using the term magnetic flux density.

[0015] The sample analysis system 1 includes a magnetic field change device 100 (see FIG. 2), a detection unit 200 (see FIG. 2), a controller 300, and a voltage application unit 401. The sample analysis system 1 further includes a sipper nozzle 411, a pump 412, an arm 415, a reaction unit 511, a suspension container 512, a washing liquid container 513, a buffer solution container 514, a washing unit 515, and a waste liquid container 516.

[0016] (Detection Unit 200) As shown in FIG. 2, the detection unit 200 is composed of a photodetector 201, a flow channel 210, a reaction field electrode 221, and a counter electrode 222. The flow channel 210 is formed by a flow channel top wall 211, a flow channel bottom wall 212, and a side wall 213 (see FIG. 9A). The flow channel 210 may be configured inside a flow cell (not shown). Magnetic particles P bound to a labeled substance flow through the flow channel 210. The flow channel top wall 211 is preferably made of a transparent material so that the photodetector 201 can detect the wavelength of light emitted by the labeled substance bound to the magnetic particles P around the reaction field electrode 221. The flow channel top wall 211 is preferably made of, for example, glass, plastic, or the like.

[0017] A reaction field electrode 221 is installed around the lower part of the flow channel 210. A counter electrode 222 is installed around the opposite side of the reaction field electrode 221, sandwiching the flow channel 210. Furthermore, the reaction field electrode 221 and the counter electrode 222 are connected to a voltage application unit 401 via signal lines L11 and L12. The voltage application unit 401 is connected to the controller 300 via a signal line L2.

[0018] The reaction field electrode 221 and the counter electrode 222 are made of materials such as gold, platinum, palladium, tungsten, iridium, nickel, alloys thereof, carbon materials, etc. Alternatively, the reaction field electrode 221 and the counter electrode 222 may be made of a base material such as titanium, on which the above-mentioned materials are deposited by plating, sputtering, or the like.

[0019] The reaction field electrode 221 is preferably planar for ease of luminescence measurement. Furthermore, it is desirable that the reaction field electrode 221 be provided on the bottom surface of the flow channel 210. However, the reaction field electrode 221 may be provided on other surfaces (surfaces other than the bottom surface) within the flow channel 210, or on multiple surfaces arranged three-dimensionally. Furthermore, the reaction field electrode 221 does not necessarily have to be planar as long as it is suitable for capturing magnetic particles P or for electrochemiluminescence of a labeled substance bound to the magnetic particles P. That is, the reaction field electrode 221 may be configured in a linear shape, or a combination of a linear shape and a planar shape. The counter electrode 222 may be configured in any position or shape that can generate a voltage in the flow channel 210 when combined with the reaction field electrode 221. That is, the counter electrode 222 may be configured in a linear shape, a planar shape, or a combination thereof.

[0020] (Magnetic Field Modification Device 100) As shown in FIG. 2, the magnetic field modification device 100 is composed of a magnet 101, a magnetic flux induction section 120 made of a soft magnetic material, and a magnetic field modification section 110.

[0021] The magnet 101, which is a permanent magnet, applies a magnetic field to the magnetic particles P. Specifically, the magnet 101 generates a magnetic field for attracting the magnetic particles P to a particle capture region 231 above the reaction field electrode 221. The reaction field electrode 221 and the counter electrode 222 are provided so that the particle capture region 231 is located directly below the photodetector 201. By using a permanent magnet for the magnet 101, the configuration of the magnetic field change device 100 can be simplified. In the following figures, the reference numeral for the magnetic field change device 100 may be omitted as appropriate.

[0022] The magnetic field change unit 110 changes the magnetic field around the magnet 101. Specifically, the magnetic field change unit 110 moves the magnet 101 to a position close to the flow channel 210 (referred to as the magnetic field on position) and a position away from the flow channel 210 (referred to as the magnetic field off position). The magnetic field change unit 110 is connected to the controller 300 via a signal line L6. That is, the controller 300 controls the magnetic field change unit 110. The magnetic flux induction unit 120 is disposed so as to surround the magnet 101 when the magnet 101 is in a position away from the flow channel 210 (the magnetic field off position). The magnetic flux induction unit 120 will be described later; the magnetic flux induction unit 120 changes the magnitude (distribution of magnetic flux density) of the magnetic field generated from the magnet 101 and affecting the magnetic particles P and the photodetector 201. The magnetic flux induction unit 120 is also made of any of iron, silicon steel, permalloy, permendur, a magnetic alloy, and soft ferrite.

[0023] In this manner, the magnet 101 is provided to keep the magnetic particles P directly below the photodetector 201 .

[0024] The voltage application unit 401 is controlled by the controller 300. In response to a command from the controller 300 to the voltage application unit 401, the voltage application unit 401 applies a voltage between the reaction field electrode 221 and the counter electrode 222 inside the flow channel 210. When a voltage is applied by the voltage application unit 401, the labeled substance bound to the magnetic particles P adsorbed to the upper part of the reaction field electrode 221 electrochemically emits light.

[0025] The photodetector 201 constituting the detection unit 200 detects light emitted by the labeled substance. Specifically, the photodetector 201 detects the wavelength of light emitted by the labeled substance bound to the magnetic particles P in the vicinity of the reaction field electrode 221. For example, a camera or a photomultiplier tube can be used as the photodetector 201. The photodetector 201 is operated by a signal transmitted from the controller 300.

[0026] Flow path 210 formed inside the flow cell is connected to sipper nozzle 411 and pump 412 through tubes T1 and T2. Sipper nozzle 411 is movable by arm 415, and suspension container 512 to cleaning unit 515 are installed within the range of movement of sipper nozzle 411.

[0027] A valve 413 is provided in a tube T2 connecting the flow path 210 and the pump 412. The pump 412 and the valve 413 are connected to the controller 300 via signal lines L5 and L3. Furthermore, the flow path 210 continues to a waste liquid container 516 via a valve 414 and a tube T3.

[0028] The controller 300 is connected to the photodetector 201, voltage application unit 401, valves 413 and 414, pump 412, magnetic field change unit 110, and arm 415 via independent signal lines L1 to L6, respectively. This allows the controller 300 to independently control each of the photodetector 201, voltage application unit 401, valves 413 and 414, pump 412, magnetic field change unit 110, and arm 415.

[0029] The sample to be analyzed is a substance derived from a living body, such as serum or urine. When the sample is serum, the specific component to be analyzed is, for example, a tumor marker, an antibody, an antigen-antibody complex, or a single protein. In the following description, the component to be identified by analysis (specific component) is assumed to be TSH (Thyroid Stimulating Hormone). However, substances other than TSH may also be used in the analysis.

[0030] In the reaction unit 511, as a pretreatment step, the sample to be analyzed is mixed with a bead solution and a reagent.

[0031] The suspension container 512 contains a sample to be analyzed, which is mixed with a bead solution and a reagent as a pretreatment step and then reacted at a constant temperature (e.g., 37°C) for a certain period of time. The bead solution is a solution in which magnetic particles P, consisting of particulate magnetic material embedded in a matrix material such as polystyrene, are dispersed in a buffer solution. Streptavidin, which can bind to biotin, is bound to the surface of the matrix material. The reagent contains a substance that binds the magnetic particles P to the specific component TSH in the sample. The reagent also contains an anti-TSH antibody with a biotin-treated end. Different reagents are used depending on the type of specific component to be analyzed; for example, immunoglobulins, antigens, antibodies, or other biological substances are used as reagents. The solution containing the magnetic particles P and the sample is referred to as a suspension.

[0032] The cleaning liquid container 513 contains a cleaning liquid for cleaning the flow path 210 and the inside of the tube T1.

[0033] The buffer solution container 514 contains a buffer solution.

[0034] The waste liquid container 516 contains the liquid discharged from the pump 412 .

[0035] The flow channel 210 near the photodetector 201 preferably has a flow channel shape with a rectangular cross section as shown in FIG. 1 to facilitate capture of the magnetic particles P. In this case, the shape of the flow channel 210 is defined by the length (path length) along the direction of the flow of the magnetic particles P (suspension), and the thickness (vertical direction) and width (horizontal direction) of the cross section perpendicular to the flow. The flow channel 210 near the photodetector 201 is preferably formed such that the path length is 2 to 20 times the greater of the thickness and width. Such a configuration of the flow channel 210 ensures a sufficient path for the magnetic particles P to flow. Furthermore, the above-described shape of the flow channel 210 allows the magnetic particles P in the fluid to spread within the flow channel 210. The magnetic particles P are then more easily adsorbed by the particle capture region 231 configured above the reaction field electrode 221 provided on the bottom surface of the flow channel 210.

[0036] The distribution of magnetic particles P adsorption inside the flow channel 210 is determined by the magnetic force from the magnet 101 installed near the flow channel 210 and the drag force caused by the fluid flow. The magnetic flux density inside the flow channel 210 is preferably about 0.1 to 0.5 T. The flow velocity of the fluid at that time is preferably about 0.05 to 0.10 m / s.

[0037] The particles used as the magnetic particles P are preferably the following particles: (A1) Particles that exhibit paramagnetic, superparamagnetic, ferromagnetic, or ferrimagnetic properties. (A2) Particles that exhibit paramagnetic, superparamagnetic, ferromagnetic, or ferrimagnetic properties and are encapsulated in materials such as synthetic polymer compounds (polystyrene, nylon, etc.), natural polymers (cellulose, agarose, etc.), inorganic compounds (silica, etc.).

[0038] Furthermore, the particle size of the magnetic particles P is preferably in the range of 0.01 to 200 μm, specifically in the range of 1 to 10 μm. The specific gravity of the magnetic particles P is preferably 1.3 to 1.5. By using magnetic particles P with such specifications, the magnetic particles P are less likely to settle in the liquid and are more likely to be suspended. Furthermore, a substance that has the property of specifically binding to the analyte (sample), for example, an antibody that has the property of specifically binding to an antigen, is bound to the surface of the magnetic particles P.

[0039] The labeling substance is preferably a substance as shown below. Specifically, when the labeling substance has an appropriate structure as shown below, the labeling substance specifically binds to the analyte (sample) and emits light due to the appropriate structure.

[0040] (B1) Labeling substances used in fluorescent immunoassays, such as antibodies labeled with fluorescein isothiocyanate. (B2) Labeling substances used in chemiluminescent immunoassays, such as antibodies labeled with acridinium esters. (B3) Labeling substances used in chemiluminescent enzyme immunoassays, such as antibodies labeled with chemiluminescent enzymes that use luminol or adamantyl derivatives as luminescent substrates.

[0041] The above is an example of the configuration of the sample analysis system 1.

[0042] (Controller 300) FIG. 3 is a functional block diagram showing the configuration of the controller 300 used in the sample analysis system 1 in this embodiment.

[0043] The controller 300 is configured by, for example, a PC (Personal Computer) etc. The controller 300 includes at least a memory 301, a calculation unit 302, a storage unit 303, and a communication unit 304.

[0044] The memory 301 is configured by a RAM (Random Access Memory) or the like.

[0045] The arithmetic unit 302 is configured with a CPU (Central Processing Unit), a GPU (Graphic Processing Unit), and the like.

[0046] The storage device 303 is configured by a hard disk drive (HDD), a solid state drive (SSD), or the like.

[0047] Then, the program stored in the storage device 303 is loaded into the memory 301. The loaded program is then executed by the arithmetic device 302. In this way, various functions of the controller 300 are realized.

[0048] The communication device 304 acquires information from the photodetector 201 , the voltage application unit 401 , the valves 413 and 414 , the pump 412 , the magnetic field change unit 110 , and the arm 415 , and transmits information.

[0049] (Change in Magnetic Field) Next, a change in the magnetic field around the particle capture region 231 will be described with reference to FIGS. 4A and 4B.

[0050] Fig. 4A is a schematic diagram showing a state (ON state) in which a magnetic field is applied to particle capture region 231, and Fig. 4B is a schematic diagram showing a state (OFF state) in which no strong magnetic field is applied to particle capture region 231. Note that the same components as those shown in Figs. 1 and 2 are denoted by the same reference numerals and descriptions thereof will be omitted.

[0051] The magnetic flux guide unit 120 is installed at a magnetic field off position, which is a predetermined distance away from the flow channel 210. When the magnet 101 is located close to the flow channel 210 (referred to as the magnetic field on position) as shown in Fig. 4A, the magnet 101 is located outside the magnetic flux guide unit 120, and therefore a large magnetic field acts on the flow channel 210. This allows the magnetic particles P flowing through the flow channel 210 to be captured by the magnetic field.

[0052] In this embodiment, the magnetization direction A2 of the magnet 101 is defined as the direction from the south pole 101b to the north pole 101a. As shown in Fig. 4A, the magnetization direction A2 of the magnet 101 is parallel to the bottom surface (flow path bottom wall 212) of the flow path where the magnetic particles P are captured by the magnetic field generated by the magnet 101. With this configuration, it is possible to capture a large number of magnetic particles P.

[0053] When detecting luminescence from the labeling substance using photodetector 201, magnetic field change unit 110 moves magnet 101 to the magnetic field off position as shown in FIG. 4B to avoid the influence of the magnetic field on photodetector 201. At this time, magnet 101 fits into magnetic flux guide unit 120. As a result, as shown in FIG. 4B, most of the magnetic flux MF (magnetic field) generated from magnet 101 passes through the soft magnetic material that makes up magnetic flux guide unit 120. Therefore, the magnitude of the magnetic field acting on photodetector 201 can be reduced.

[0054] In this way, magnetic flux guider 120, which guides magnetic flux MF, is arranged to cover the periphery of magnet 101 when magnet 101 is in the magnetic field-off position. Specifically, in the state of FIG. 4B , magnetic flux guider 120 has a first surface 122 (see FIG. 4A ) that faces north pole 101 a (see FIG. 4A ) of magnet 101. Magnetic flux guider 120 also has a second surface 123 (see FIG. 4A ) that faces south pole 101 b (see FIG. 4A ) of magnet 101. First surface 122 and second surface 123 are connected by a member of magnetic flux guider 120.

[0055] Supplementally, the magnetic flux guider 120 includes a first portion, a second portion facing the first portion, and a third portion (member) connecting the first portion and the second portion. The first portion has a first surface 122, and the second portion has a second surface 123 facing the first portion. In this embodiment, the magnetic flux guider 120 has a concave cross-sectional shape, and the third portion connecting the first portion and the second portion forms a magnetic path (the cross-sectional shape may be U-shaped, C-shaped, or the like).

[0056] With this configuration, when the magnet 101 is housed (FIG. 4B) in the housing 121 (see FIG. 4A), most of the magnetic flux MF generated from the magnet 101 passes through the soft magnetic material that constitutes the magnetic flux guider 120. As described above, the magnitude of the magnetic field acting on the photodetector 201 can be reduced. This makes it possible to change the magnitude of the magnetic field over a shorter travel distance than with conventional magnetic field change devices 100. This allows the configuration of the magnetic field change device 100 to be made more compact.

[0057] In this way, under the control of the controller 300, the magnetic field change unit 110 changes the magnetic field by switching the state in which the N pole 101a faces the first surface 122 and the S pole 101b faces the second surface 123. A first state is a state in which the N pole 101a faces the first surface 122 and the S pole 101b faces the second surface 123. A second state is a state in which the N pole 101a does not face the first surface 122 and the S pole 101b does not face the second surface 123. The magnetic field change unit 110 then switches between the first state and the second state, thereby changing the magnetic field around the magnet 101.

[0058] Next, the change in the magnetic field by the magnetic field change device 100 will be described with reference to FIGS. 5A to 8. FIG.

[0059] Fig. 5A is a diagram showing the positional relationship between magnetic flux induction unit 120 and magnet 101 in a magnetic field-on state. Fig. 5B is a diagram showing the distribution of the magnitude of magnetic flux density (state of magnetic field) analyzed in the state shown in Fig. 5A. Fig. 6A is a diagram showing the positional relationship between magnetic flux induction unit 120 and magnet 101 in a magnetic field-off state. Fig. 6B is a diagram showing the distribution of the magnitude of magnetic flux density (state of magnetic field) analyzed in the state shown in Fig. 6A.

[0060] The magnetic field on state refers to a state in which a strong magnetic field is applied to the flow channel 210 by the magnet 101. The magnetic field off state refers to a state in which a weaker magnetic field than that in the magnetic field on state is applied to the flow channel 210.

[0061] Furthermore, Fig. 7 is a diagram showing the analysis conditions. Note that the magnetic flux guide portion 120 in Fig. 7 shows the state of the magnetic flux guide portion 120 as viewed from the direction of the white arrow shown in Figs. 5A and 6A.

[0062] In this analysis, magnet 101 was made of N49M and measured 3 x 6 x 4 mm. The magnetization direction A2 of magnet 101 was the X-axis direction in Figure 7. The material of magnetic flux guide portion 120 was ferrite. The external dimensions of magnetic flux guide portion 120 were 24 x 20 x 12 mm.

[0063] As shown in FIG. 7 , in this analysis, the position 201a of the light incident surface of the photodetector 201 is set to 10 mm (reference symbol D1) above the top surface of the magnet 101 when the magnetic field is on. Furthermore, the distance (reference symbol D2) between the top surface position of the magnet 101 and the top surface position of the magnetic flux guider 120 when the magnetic field is on is 10 mm. Note that "upper" refers to the positive direction of the Z axis in FIG. 7 . In other words, as shown in FIG. 7 , the side of the photodetector 201 is defined as the upper side, and the side of the magnetic flux guider 120 is defined as the lower side. Note that the arrow A3 in FIG. 7 indicates the direction of movement of the magnet 101.

[0064] 5A and 6A, magnetic flux induction unit 120 has a U-shape. As shown in Fig. 5A, magnetic flux induction unit 120 has storage section 121, which is a space for storing magnet 101, inside.

[0065] As shown in Fig. 5A, in the magnetic field on state, the magnet 101 is not contained in the storage portion 121 of the magnetic flux guide portion 120. In this state, the magnetic field (distribution of the magnitude of the magnetic flux density) around the magnet 101 is as shown in Fig. 5B. Fig. 5B shows that a strong magnetic field is applied to the flow channel 210 (particle capture region 231), and furthermore, the magnetic field extends to the photodetector 201.

[0066] As shown in FIG. 6A, in the magnetic field off state, the magnet 101 is accommodated in the storage portion 121 (see FIG. 5A) of the magnetic flux induction unit 120. As a result, as described above, most of the magnetic flux MF (see FIGS. 4A and 4B) generated from the magnet 101 passes through the interior of the magnetic flux induction unit 120. In the magnetic field off state shown in FIG. 6A, the magnetic field (distribution of the magnitude of the magnetic flux density) around the magnet 101 is as shown in FIG. 6B. As shown in FIG. 6B, almost no magnetic field exists outside the magnetic flux induction unit 120. In particular, FIG. 6B shows that there is almost no influence of the magnetic field around the photodetector 201. The relationship between the gradation in FIG. 6B and the magnitude of the magnetic flux density is as shown in the legend in FIG. 5B.

[0067] 5A and 6A, the magnetic field change unit 110 moves the magnet 101 in and out of the storage portion 121 of the magnetic flux guide unit 120. With this configuration, the magnetic field generated by the magnet 101 can be changed with a simple configuration.

[0068] 8 is a diagram showing the relationship between the position of the magnet 101 and the magnetic flux density. Referring to FIG. 8, the movement distance of the magnet 101 in the vertical direction and the magnitude of the magnetic flux density at the position 201a on the light incident surface of the photodetector 201 are evaluated.

[0069] 8, the horizontal axis represents the distance traveled by magnet 101. The distance traveled by magnet 101 is defined as the distance traveled by the top surface of magnet 101, with the position in FIG. 7 being "0." The vertical axis in FIG. 8 represents the magnetic flux density (unit: T) at position 201a (see FIG. 7) on the light incident surface of photodetector 201.

[0070] In FIG. 8, the broken line B1 indicates the value of the magnetic flux density at which the photodetector 201 is not affected, and its magnitude is approximately 50 μT.

[0071] 8, curve C1 shows the change in magnetic flux density with the movement distance of the magnet 101 when the magnetic field change device 100 of this embodiment is used, and curve C2 shows the change in magnetic flux density with the movement distance of the magnet 101 when the magnetic field change device 100 of the comparative example is used. The comparative example is a magnetic field change device that is not provided with a magnetic flux induction unit 120.

[0072] As shown in Fig. 8 , in the comparative example (curve C2), the magnet 101 needs to move 42 mm or more around the photodetector 201 to reach a magnetic flux density (50 µT: dashed line B) at which the sensitivity of the photodetector 201 is not reduced. In contrast, in the present embodiment (curve C1), the magnetic flux density (50 µT: dashed line B) at which the sensitivity of the photodetector 201 is not reduced is reached with a movement distance of 15 mm or less. This is because, as described above, when the magnet 101 moves to the magnetic field off position, the magnet 101 fits into the storage portion 121 (see Fig. 5A ) of the magnetic flux guide portion 120, and most of the magnetic flux generated from the magnet 101 passes through the interior of the magnetic flux guide portion 120 and is not generated outside the magnetic flux guide portion 120.

[0073] (Specific Example of Magnetic Field Changer 100) Next, a specific example of the magnetic field changer 100 will be described with reference to FIGS. 9A and 9B.

[0074] 9A and 9B are diagrams showing a specific example of the magnetic field change device 100 according to the first embodiment. FIG. 9A shows a state in which the magnet 101 is positioned in the magnetic field-on position. FIG. 9B shows a state in which the magnet 101 is positioned in the magnetic field-off position. In FIGS. 9A and 9B, the same components as those in FIGS. 4A and 5B are denoted by the same reference numerals and will not be described. In FIGS. 9A and 9B, the magnetic particles P are assumed to flow from the back of the paper to the front of the paper.

[0075] 9A and 9B, the magnetic field change unit 110a includes an arm unit 111. The magnet 101 is provided at one end of the arm unit 111. The other end of the arm unit 111 is provided with a rotating unit 112 that rotates the arm unit 111. The rotating unit 112 rotates (as indicated by the double-headed arrow in FIGS. 9A and 9B), allowing the magnet 101 to move between the magnetic field-on position in FIG. 9A and the magnetic field-off position in FIG. 9B.

[0076] Next, with reference to FIGS. 10 and 11, the difference between the comparative example and this embodiment in the case where the magnetic field change part 110a has the arm part 111 as shown in FIGS. 9A and 9B will be described.

[0077] Fig. 10 is a diagram showing the movement of the magnet 101 by the magnetic field change unit 110a in a comparative example, and Fig. 11 is a diagram showing the movement of the magnet 101 by the magnetic field change unit 110a in this embodiment. Note that the length of the arm unit 111 is assumed to be the same in Fig. 10 and Fig. 11.

[0078] 10 and 11, the magnetic field change unit 110a has the same configuration as that shown in Fig. 9A and 9B. In Fig. 10 and 11, the dashed lines indicate the magnetic field on positions, and the solid lines indicate the magnetic field off positions.

[0079] In the example shown in FIG. 10, in order to prevent the photodetector 201 from being affected by the magnetic field of the magnet 101, the arm 111 needs to be rotated by approximately 90° by the rotating part 112.

[0080] In contrast, in the example shown in FIG. 11, the influence of the magnetic field on the photodetector 201 can be reduced by simply rotating it by approximately 11.8°.

[0081] (Flowchart) Next, a description will be given of the operation of the sample analysis system 1 of this embodiment. In operation, one analysis is considered to be one cycle, and the basic operating state of the device is to perform the cycle multiple times in succession.

[0082] Fig. 12 is a flowchart showing the steps of the sample analysis method performed by the sample analysis system 1. Figs. 1, 2 and 4A will be referenced as appropriate.

[0083] One cycle of sample analysis consists of a suspension aspiration period (S1), a magnetic particle capture period (S2), a detection period (S3), a washing period (S4), a reset period (S5), and a preliminary aspiration period (S6). One cycle starts when the suspension container 512 containing the suspension processed in the reaction unit 511 is set in a predetermined position.

[0084] During the suspension suction period (S1), controller 300 sets valve 413 to an open state and valve 414 to a closed state. Then, arm 415 is operated in response to a signal transmitted from controller 300. The operation of arm 415 causes sipper nozzle 411 to be inserted into suspension container 512. Subsequently, pump 412 performs a suction operation of a fixed amount in response to a signal transmitted from controller 300. This operation causes the suspension contained in suspension container 512 to be introduced into tube T1 via sipper nozzle 411.

[0085] Then, once the suspension is introduced into the inside of the tube T1, the controller 300 temporarily stops the pump 412. Then, the controller 300 operates the arm 415 to insert the shipper nozzle 411 into the cleaning unit 515. The shipper nozzle 411 is cleaned by passing through the cleaning unit 515. Incidentally, the cleaning of the shipper nozzle 411 is separate from the cleaning performed during the cleaning period described below.

[0086] During the magnetic particle capture period (S2), which is the magnetic particle capture step, the magnetic field change unit 110 is operated by a signal transmitted from the controller 300. As a result, the magnet 101 moves to the vicinity of the particle capture region 231 at the bottom of the flow channel 210 (magnetic field on position). Thereafter, the pump 412 is operated by a signal transmitted from the controller 300. At this time, the pump 412 sucks the suspension at a constant speed. As a result, the suspension present inside the tube T1 flows inside the flow channel 210. A magnetic field generated by the magnet 101 is present on the wall 11 of the flow channel 210 and the bottom wall 212 of the flow channel. Therefore, the magnetic particles P contained in the suspension are attracted toward the magnet 101 by the magnetic field and are captured (adsorbed) in the particle capture region 231.

[0087] During the magnetic particle capture period (S2), the magnetic particles P are captured by the magnetic field generated by the magnet 101.

[0088] After the magnetic particles P have been captured for a certain period of time, the controller 300 stops the pump 412 from sucking the suspension.

[0089] During the detection period (S3), which is the detection step, the controller 300 operates the magnetic field change unit 110 to move the magnet 101 to a position (magnetic field off position) away from the flow channel 210. Subsequently, a signal is sent from the controller 300 to operate the photodetector 201 and apply voltage to the reaction field electrode 221 and the counter electrode 222. As a result, with the magnetic particles P held above the reaction field electrode 221, the photodetector 201 receives light emitted from the labeled substance bound to the magnetic particles P.

[0090] In this way, in the detection period (S3), after the magnetic particle capture period (S2), the magnetic field change unit 110 causes the north pole 101a to face the first surface 122 and the south pole 101b to face the second surface 123. Then, detection is performed by the photodetector 201.

[0091] Since the pump 412 stops sucking the suspension before the detection period, the magnetic particles P continue to remain in the particle capture region 231 even if the magnetic field from the magnet 101 disappears (decreases).

[0092] In this way, the luminescence intensity from the labeling substance is measured. The detected luminescence intensity is sent to the controller 300 as a signal.

[0093] After the measurement has been performed for a certain period of time, the controller 300 stops the application of voltage to the reaction field electrode 221 and the counter electrode 222, and stops the operation of the photodetector 201. Furthermore, during the detection period, the controller 300 operates the arm 415 to insert the sipper nozzle 411 into the cleaning liquid container 513.

[0094] During the cleaning period (S4), the controller 300 uses the pump 412 to aspirate the cleaning liquid. As a result, the cleaning liquid aspirated from the cleaning liquid container 513 passes through the inside of the flow path 210. At this time, since the magnet 101 is away from the flow path 210 (located in the magnetic field off position), the magnetic particles P are not retained in the particle capture region 231 on the reaction field electrode 221 and are washed away together with the cleaning liquid.

[0095] In the reset period (S5), the controller 300 closes the valve 413, opens the valve 414, and causes the pump 412 to perform a discharge operation. As a result, the liquid inside the pump 412 is discharged into the waste liquid container 516.

[0096] During the preliminary suction period (S6), the controller 300 opens the valve 413 and closes the valve 414. Then, the controller 300 operates the arm 415 to move the sipper nozzle 411. As a result, the controller 300 inserts the sipper nozzle 411 into the buffer solution container 514. Thereafter, the controller 300 operates the pump 412 to aspirate the buffer solution from the buffer solution container 514. As a result, the inside of the tube T1 and the flow path 210 is filled with the buffer solution. After the preliminary suction period, the next cycle can be executed.

[0097] According to the first embodiment, the magnetic field change device 100 can be miniaturized without causing a decrease in the sensitivity of the photodetector 201. This makes it possible to miniaturize the unit configured by the magnetic field change device 100 and the detection section 200 and improve the degree of freedom in the configuration of the flow channel 210. By miniaturizing the unit configured by the magnetic field change device 100 and the detection section 200, the sample analysis system 1 can also be miniaturized.

[0098] Furthermore, by configuring the arm portion 111 to rotate by the rotating portion 112, the magnetic field change device 100 can be configured with a simple structure.

[0099] Furthermore, in the first embodiment, the magnetic field change unit 110 (110a) is configured to move the magnet 101 in a direction perpendicular to (i.e., up and down) the bottom surface of the flow channel (flow channel bottom wall 212) where the magnetic particles P are captured by the magnetic field generated by the magnet 101. The flow channel bottom surface is the surface of the flow channel bottom wall 212 that faces the flow channel 210, and corresponds to the lower surface of each of the surfaces that make up the flow channel 210. By adopting such a configuration, the magnetic field change device 100 can be configured simply.

[0100] [Second embodiment] Figures 13A and 13B are diagrams showing the configuration of a magnetic field change device 100 in a second embodiment. Figure 13A shows the case where the magnet 101 is in the magnetic field-on position, and Figure 13B shows the case where the magnet 101 is in the magnetic field-off position. In Figures 13A and 13B, the same components as those in Figures 4A and 4B are denoted by the same reference numerals and their description will be omitted. In Figures 13A and 13B, the flow path 210 and the magnetic flux guide 120 are shown as cross-sectional views.

[0101] The magnetic particles P move from the back side of the paper to the front side of the paper in the flow channel 210.

[0102] 13A and 13B includes an arm 111, one end of which is provided with a magnet 101. The other end of the arm 111 is provided with a solenoid 113 that moves the arm 111 using a solenoid. The arm 111 has an L-shape. The solenoid 113 moves the arm 111 in the up and down direction using a solenoid (electromagnet) (as indicated by the double-headed arrows in FIGS. 13A and 13B).

[0103] According to the example shown in FIGS. 13A and 13B, the arm portion 111 and the magnet 101 are moved by the solenoid (electromagnet) of the solenoid portion 113, so that the magnet 101 can be moved quickly.

[0104] Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. 14A and 14B.

[0105] 14A and 14B are diagrams showing the configuration of a magnetic field change device 100 according to the third embodiment.

[0106] In the first and second embodiments, an example is shown in which the magnet 101 moves in the vertical direction. The vertical direction means a direction perpendicular to the bottom surface of the flow channel (flow channel bottom wall 212) where the magnetic particles P are captured by the magnetic field generated by the magnet 101. In contrast, in the third embodiment, an example is shown in which the magnet 101 moves in the horizontal direction. Note that the horizontal direction means a direction parallel to the bottom surface of the flow channel (flow channel bottom wall 212) where the magnetic particles P are captured in the flow channel 210.

[0107] 14A and 14B, the same components as those in FIGS. 13A and 13B are denoted by the same reference numerals, and the description thereof will be omitted. Also, in FIGS. 14A and 14B, the magnetic particles P are assumed to flow through the flow channel 210 from the back of the page to the front of the page. Also, in FIGS. 14A and 14B, the flow channel 210 and the magnetic flux guide 120 are shown as cross-sectional views.

[0108] 14A and 14B, the magnet 101 is moved laterally (horizontally) by the solenoid unit 113. That is, the magnetic field change unit 110c moves the magnet 101 horizontally. The magnetic flux induction unit 120 is positioned laterally with respect to the particle capture region (displaced from directly below the particle capture region). That is, the magnetic field off position of the magnet 101 is located laterally with respect to the magnetic field on position.

[0109] In the example shown in FIGS. 14A and 14B, the magnet 101 moves laterally (horizontally) by the solenoid portion 113, so that the magnet 101 moves between the magnetic field on position and the magnetic field off position.

[0110] The magnetic field change device 100 according to the third embodiment can reduce the space in the vertical direction (the direction perpendicular to the channel bottom (channel bottom wall 212) where the magnetic particles P are captured by the magnetic field generated by the magnet 101) compared to the first and second embodiments. This allows the size of the sample analysis system 1 to be more compact than the first and second embodiments.

[0111] Fourth Embodiment Next, a fourth embodiment of the present invention will be described with reference to FIGS. 15A and 15B.

[0112] 15A and 15B are diagrams showing the configuration of a magnetic field change device 100 according to the fourth embodiment. FIG. 15A shows the case where the magnetic field is on, and FIG. 15B shows the case where the magnetic field is off. In addition, in FIGS. 15A and 15B, the same components as those in FIGS. 4A and 4B are denoted by the same reference numerals, and their description will be omitted. In the example shown in FIGS. 15A and 15B, magnetic particles P are assumed to flow in the horizontal direction of the page (X-axis direction: direction of arrow A1). In addition, in FIGS. 15A and 15B, the flow path 210, magnet 101, and magnetic flux induction unit 120A are shown as cross-sectional views.

[0113] 15A and 15B, the magnetic field change device 100 is configured such that the position of the magnet 101 is fixed, and the magnetic flux induction unit 120A is moved by the magnetic field change unit 110d. Specifically, the magnetic field change unit 110d is configured with an L-shaped arm unit 111 and a solenoid unit 113. The magnetic flux induction unit 120A is provided on one end of the arm unit 111, and the solenoid unit 113 is provided on the other end.

[0114] Then, the arm 111 is moved vertically (perpendicular to the bottom surface of the flow path (flow path bottom wall 212) where the magnetic particles P are captured by the magnetic field generated by the magnet 101) by the solenoid 113, thereby moving the magnetic flux induction unit 120A vertically. That is, in the magnetic field-on state, as shown in FIG. 15A , the magnetic flux induction unit 120A moves downward on the page (negative side in the Z-axis direction: toward the ground), exposing the magnet 101 to the outside of the magnetic flux induction unit 120A. As a result, a magnetic field for capturing the magnetic particles P can be applied to the particle capture region 231.

[0115] As described above, in the fourth embodiment, the magnetic field change unit 110d includes an arm unit 111. The magnetic flux induction unit 120A is provided at one end of the arm unit 111. Furthermore, the solenoid unit 113 that moves the arm unit 111 by a solenoid is provided at the other end of the arm unit 111.

[0116] 15B, in the magnetic field off state, magnetic flux induction unit 120A moves upward on the page (positive side in the Z-axis direction: opposite side from the ground), causing magnet 101 to fit into storage section 121 of magnetic flux induction unit 120A. As a result, most of the magnetic flux MF (see FIGS. 4A and 4B) generated from magnet 101 passes through the inside of magnetic flux induction unit 120A, reducing the strength of the magnetic field outside magnetic flux induction unit 120A. This reduces the effect of the magnetic field on photodetector 201.

[0117] In the first to third embodiments, the magnet 101 is configured to move between a magnetic field-on position and a magnetic field-off position. In contrast, in the fourth embodiment shown in Figures 15A and 15B, the magnetic flux guider 120A moves to switch between the magnetic field-on state and the magnetic field-off state.

[0118] Next, the effects of the fourth embodiment will be described with reference to FIGS. 16A and 16B.

[0119] Fig. 16A is a diagram showing the configuration of a magnetic flux guider 120 used in the first to third embodiments. Fig. 16B is a diagram showing the configuration of a magnetic flux guider 120A used in the fourth embodiment. Figs. 16A and 16B show the magnetic field-off state and are top perspective views of the magnetic flux guiders 120 and 120A.

[0120] 16A, the magnetic flux guider 120 used in the first to third embodiments is provided with a notch 124 through which the arm 111 (see FIG. 9A, etc.) passes. Therefore, one of the side surfaces of the magnet 101 stored in the storage section 121 is exposed.

[0121] In the fourth embodiment, as shown in FIG. 16B, it is not necessary to provide the magnetic flux induction unit 120A with the notch 124 (see FIG. 16A) for providing the arm 111 (see FIG. 9A, etc.). This allows the magnetic flux induction unit 120A to cover all surfaces of the magnet 101 except for the upper surface, as shown in FIG. 16B, in the magnetic field-off state. As a result, in the magnetic field-off state, it is possible to prevent the magnetic field generated by the magnet 101 from leaking outside the magnetic flux induction unit 120A. Therefore, according to the fourth embodiment, the influence of the magnetic field on the photodetector 201 can be reduced more than in the magnetic field change device 100 of the first to third embodiments.

[0122] (Configuration Example of Magnetic Flux Guiding Section 120) Next, configuration examples of the magnetic flux guiding section 120 will be shown with reference to FIGS. 17A to 18B.

[0123] 17A to 17C are diagrams showing examples of the configuration of the magnetic flux guide unit 120 used in the first to third embodiments. In Fig. 17A to 17C, top views of the magnetic flux guide unit 120 are shown.

[0124] 17A to 17C all have a notch 124 for passing the arm portion 111 (see FIG. 9A, etc.). In the example shown in FIG. 17A, the magnetic flux induction portion 120 has a U-shape, in the example shown in FIG. 17B, the magnetic flux induction portion 120 has a U-shape, and in the example shown in FIG. 17C, the magnetic flux induction portion 120 has a C-shape.

[0125] 18A and 18B are diagrams showing an example of the configuration of a magnetic flux guide unit 120A used in the fourth embodiment, in which top views of the magnetic flux guide unit 120A are shown.

[0126] 18A and 18B do not have the notch 124 (see FIGS. 17A to 17C) for passing the arm portion 111 (see FIG. 9A, etc.). Therefore, the surfaces of the magnet 101 other than the top surface are covered by the magnetic flux induction portion 120A. In the example shown in FIG. 18A, the top surface of the magnetic flux induction portion 120A has a rectangular shape, while in the example shown in FIG. 18B, the top surface of the magnetic flux induction portion 120A has an oval shape.

[0127] In a first embodiment of this embodiment, the magnet 101 moves up and down as the arm 111 rotates using the rotating unit 112. In a second embodiment, the magnet 101 moves up and down using the solenoid unit 113. In a third embodiment, the magnet 101 moves horizontally. In a fourth embodiment, the position of the magnet 101 is fixed, and the magnetic flux induction unit 120 moves up and down.

[0128] However, the magnetic field change device 100 is not limited to the forms of the first to fourth embodiments, as long as it is possible to have the N pole 101a facing the first surface 122 and the S pole 101b facing the second surface 123.

[0129] For example, the magnetic flux induction unit 120 may move in the horizontal direction, i.e., the magnet 101 and the magnetic flux induction unit 120 may be interchanged in the third embodiment. Alternatively, the magnetic flux induction unit 120 may rotate in the horizontal direction, thereby switching between a state in which the axis connecting the first surface 122 and the second surface 123 and the magnetization direction A2 are in the same direction and a state in which they are in different directions.

[0130] The magnet 101 can move to the outside of the magnetic flux guides 120 and 120A through the notch 124 or an opening provided in the magnetic flux guide 120A, or can be stored in the storage section 121 of the magnetic flux guides 120 and 120A.

[0131] Furthermore, although the magnet 101 is configured as a permanent magnet, it may also be configured as an electromagnet.

[0132] Note that the above-described configurations, functions, controller 300, storage unit, etc. may be partially or entirely implemented in hardware, for example, by designing them as integrated circuits. Also, as shown in FIG. 3 , the above-described configurations, functions, etc. may be implemented in software by a processor, such as a CPU, interpreting and executing programs that implement the respective functions. Information such as programs, tables, and files that implement the respective functions can be stored in a recording device, such as memory 301 or an SSD (Solid State Drive), or a recording medium, such as an IC (Integrated Circuit) card, an SD (Secure Digital) card, or a DVD (Digital Versatile Disc).

[0133] In addition, in each embodiment, the control lines and information lines shown are those that are considered necessary for explanation, and not all control lines and information lines in the product are necessarily shown. In reality, it can be considered that almost all components are interconnected.

[0134] 1 Sample analysis system 100 Magnetic field change device 101 Magnet 101a North pole 101b South pole 110 Magnetic field change unit 111 Arm unit 112 Rotating unit 113 Solenoid unit 120, 120A Magnetic flux induction unit 121 Storage unit 122 First surface 123 Second surface 124 Notch 200 Detection unit 201 Photodetector (detection unit) 210 Flow path 300 Controller A2 Magnetization direction MF Magnetic flux (magnetic field) P Magnetic particle (bound to labeling substance)

Claims

1. A magnetic field changing device comprising: a magnet that applies a magnetic field to magnetic particles bound to a labeled substance; a magnetic flux induction unit made of a soft magnetic material; and a magnetic field change unit that changes the magnetic field around the magnet, wherein the magnetic flux induction unit has a first surface facing the north pole of the magnet and a second surface facing the south pole of the magnet, the first surface and the second surface being connected by a member of the magnetic flux induction unit, and the magnetic field change unit changes the magnetic field by bringing the north pole into a state facing the first surface and the south pole into a state facing the second surface.

2. The magnetic field change device according to claim 1, characterized in that the magnetic flux induction unit has a storage section that is a space for storing the magnet, and the magnetic field change unit moves the magnet in and out of the storage section of the magnetic flux induction unit.

3. The magnetic field changing device according to claim 2, characterized in that the magnetic field changing unit moves the magnet in a direction perpendicular to the bottom surface of the flow channel where the magnetic particles are captured by the magnetic field generated by the magnet.

4. The magnetic field changing device according to claim 2, characterized in that the magnetic field changing unit moves the magnet in a direction parallel to the bottom surface of the flow channel where the magnetic particles are captured by the magnetic field generated by the magnet.

5. The magnetic field changing device according to claim 2, characterized in that the magnetic field changing section moves the magnetic flux induction section.

6. The magnetic field change device according to claim 1, characterized in that the magnetic field change unit has an arm unit, one end of which is provided with the magnet, and the other end of which is provided with a rotating unit for rotating the arm unit.

7. The magnetic field change device according to claim 1, characterized in that the magnetic field change unit has an arm unit, one end of which is provided with the magnet, and the other end of which is provided with a solenoid unit that moves the arm unit using a solenoid.

8. The magnetic field change device according to claim 1, characterized in that the magnetic field change unit has an arm unit, one end of which is provided with the magnetic flux induction unit, and the other end of which is provided with a solenoid unit that moves the arm unit using a solenoid.

9. The magnetic field changing device according to claim 1, characterized in that the magnetic flux induction portion is made of any one of iron, silicon steel, permalloy, permendur, magnetic alloy, and soft ferrite.

10. The magnetic field changing device according to claim 1, characterized in that the magnetization direction of the magnet is parallel to the bottom surface of the flow channel where the magnetic particles are captured by the magnetic field generated by the magnet.

11. The magnetic field changing device according to claim 1, wherein the magnet is a permanent magnet.

12. A sample analysis system comprising a magnetic field changing device having a magnet that applies a magnetic field to magnetic particles bound to a labeled substance, a magnetic flux induction unit made of a soft magnetic material, and a magnetic field change unit that changes the magnetic field around the magnet, as well as a detection unit that detects light emitted by the labeled substance, and a controller that controls the magnetic field change unit, wherein the magnetic flux induction unit has a first surface facing the north pole of the magnet and a second surface facing the south pole of the magnet, the first surface and the second surface being connected by a member of the magnetic flux induction unit, the magnetic field change unit changes the magnetic field by controlling the controller to bring the north pole into a state facing the first surface and the south pole into a state facing the second surface, and the detection unit detects the light with the north pole facing the first surface and the south pole facing the second surface.

13. A sample analysis method performed by a sample analysis system comprising a magnetic field changing device having a magnet that applies a magnetic field to magnetic particles bound to a labeled substance, a magnetic flux induction unit made of a soft magnetic material, and a magnetic field change unit that changes the magnetic field around the magnet, a detection unit that detects light emitted by the labeled substance, and a controller that controls the magnetic field change unit, wherein the magnetic flux induction unit has a first surface that faces the north pole of the magnet and a second surface that faces the south pole of the magnet, the first surface and the second surface being connected by a member of the magnetic flux induction unit, and the magnetic field change unit changes the magnetic field by bringing the north pole into a state facing the first surface and the south pole into a state facing the second surface under the control of the controller, and the sample analysis system comprises: a magnetic particle capture step of capturing the magnetic particles with the magnetic field generated by the magnet; a detection step in which, after the magnetic particle capture step, the magnetic field change unit causes the N pole to face the first surface and the S pole to face the second surface, and detection is performed by the detection unit.

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