ELECTROPHORESIS DEVICE

Abstract

An objective of the present invention is to provide an electrophoresis device that suppresses degradation of analytical performance and ensures a high degree of freedom in the selection of laser devices. To this end, the present invention provides an electrophoresis device that directs laser light from both ends of a capillary array consisting of several capillaries arranged in a row and detects the light from multiple capillaries. An optical isolator is located along an optical path from the laser light source to the capillary array. It is possible to suppress reflected light returning to the capillary array without directing the laser at an angle to the capillary axis, thus providing an electrophoresis device with high analytical performance.Transmitted and reflected returning light can be reliably suppressed, allowing for greater freedom in the selection of laser equipment.

Description

Technical area

[0001] The present invention relates to an electrophoresis device. Background of the invention

[0002] A multifocus capillary electrophoresis system irradiates both ends of a capillary array consisting of several capillaries arranged in a row with laser light to detect a uniform signal intensity from all capillaries. Such a multifocus system is likely to return reflected and transmitted light from the capillary to the laser unit as the light source, resulting in unstable laser oscillation and impairing analytical performance.

[0003] Patent Literature 1 describes an electrophoresis device that suppresses reflected and transmitted returning light. For example, Fig. 11 (sixth embodiment) of Patent Literature 1 discloses a technology that uses a polarizer and a half-wave plate to keep the laser light irradiated from both ends of a capillary array perpendicular to the capillary axis and suppress transmitted returning light. Fig. 12 (seventh embodiment) of Patent Literature 1 discloses a technology that irradiates the laser light at an angle not perpendicular to the capillary axis to suppress reflected returning light. Citation listPatent literature

[0004] Patent Literature 1: Unexamined US Patent Application, Publication No. 2003 / 0226756 Overview of the inventionTechnical task

[0005] If the laser light is emitted according to the Fig. 11 of Patent Literature 1, the light passes through the capillary array and disturbs the polarization state, causing fluctuations in the polarization angle after passing through the half-wave plate, and some components pass through the polarizer, making it difficult to completely shield the transmitted returning light. This technology barely suppresses the reflected returning light and requires the use of a laser unit resistant to the returning light, which limits the degree of freedom in selecting laser devices. Fig. The technology described in Patent Literature 12 irradiates the laser obliquely along the capillary axis, expanding the irradiation area of ​​the laser light, potentially generating false signals due to spectral shifts. The generation of false signals degrades the sample separation performance of an electrophoresis device.

[0006] An object of the present invention is to provide an electrophoresis device that suppresses the deterioration of analytical performance and ensures high freedom in selecting laser devices. Solution to the problem

[0007] To solve the above-mentioned problem, the present invention provides an electrophoresis device that irradiates laser light from both ends of a capillary array consisting of a plurality of capillaries arranged in a row and detects the light from the plurality of capillaries. An optical isolator is provided on an optical path from a light source of the laser light to the capillary array. Advantageous effects of the invention

[0008] The present invention can provide an electrophoresis device with high analytical performance because the reflected return light can be suppressed without irradiating the laser at an angle to the capillary axis. Transmitted and reflected return light can be reliably suppressed, allowing greater freedom in selecting laser devices. Short description of the drawings Fig. 1 is a schematic diagram illustrating an electrophoresis apparatus according to the present embodiments. Fig. Figure 2 is a diagram illustrating a state in which a DNA band separated by electrophoresis moves within the capillary. Fig. Figure 3 is a graph illustrating a change in the emission spectrum. Fig. 4 is a schematic diagram illustrating a laser light path in an irradiation optical system of an electrophoresis apparatus according to the first embodiment. Fig. Figure 5A is a diagram illustrating how laser light enters a polarization-dependent optical isolator in the forward direction. Fig. Figure 5B is a diagram illustrating how the returning light enters a polarization-dependent optical isolator in the backward direction. Fig. Figure 6 is a conceptual diagram illustrating transmitted and reflected returning light when laser light is irradiated onto a capillary array. Fig. Figure 7A is a diagram illustrating linear polarization states of the laser light and its transmitted returning light when the laser light enters the polarization-dependent optical isolator and is then irradiated onto the capillary array from below. Fig. Figure 7B is a diagram illustrating polarization states of the laser light and its transmitted returning light when the laser light enters the polarization-dependent optical isolator and is then irradiated onto the capillary array from above. Fig. 8A is a diagram illustrating an optical path of the laser light entering the polarization-independent optical isolator in the forward direction and the polarization direction at each position as viewed from the beam propagation direction. Fig. 8B is a diagram illustrating an optical path of the returning light entering the polarization-independent optical isolator in the reverse direction and the polarization direction at each position as viewed from the beam propagation direction. Fig. Figure 9A is a diagram illustrating linear polarization states of the laser light and its transmitted returning light when the laser light enters the polarization-independent optical isolator and is then irradiated onto the capillary array from below. Fig. Figure 9B is a diagram illustrating linear polarization states of the laser light and its transmitted returning light when the laser light enters the polarization-independent optical isolator and is then irradiated onto the capillary array from above. Description of the embodiments

[0009] The description below explains a configuration of the electrophoresis device according to an embodiment of the present invention with reference to Fig. 1. Fig. Figure 1 is a schematic diagram illustrating the electrophoresis apparatus according to the present embodiments. As shown in Fig. 1, the electrophoresis device 101 includes a capillary array 117 consisting of one or more capillaries 102, a thermostatic bath 118 to maintain the capillary 102 at a constant temperature, a high-voltage power supply 104 to apply a voltage to the capillary 102, a pumping mechanism 103 to inject a polymer into the capillary 102, and a transport mechanism 125. The transport mechanism 125 transports a buffer container 121, a wash container 122, a waste container 123, and a sample container 124 to a capillary cathode end 127.

[0010] The capillary array 117 includes a loading head 129 at one end, a capillary head 112 at the other, and a detection section 116 formed between the loading head 129 and the capillary head 112 for detecting a sample electrophoresed in the capillary 102. The capillary array 117 includes, for example, 24 capillaries 102 and is replaced with another one using a different capillary length when the measurement method is changed. Also, if the capillaries 102 are damaged or their quality deteriorates, they are replaced with a new capillary array 117.

[0011] The capillary 102 consists of a glass tube with an inner diameter of 50 µm and an outer diameter of 320 µm and is coated with polyimide on its surface to improve strength. The polyimide coating is spaced away from the detection section 116 of the capillary 102, where the laser light is irradiated, so that the light emitted from the inside can easily escape to the outside. The pumping mechanism 103 fills the interior of the capillary 102 with a separation medium to provide an electrophoretic difference during electrophoresis. The present embodiment uses a polymer, which is a highly viscous solution, as the separation medium.

[0012] Each capillary cathode end 127 is secured by a hollow metal electrode 126 such that the end of the capillary 102 protrudes from the hollow electrode 126 by approximately 0.5 mm. The hollow electrodes 126 provided for the capillaries 102 are all integrally mounted on the charging head 129. All hollow electrodes 126 are connected to the high-voltage power supply 104 mounted on the body of the device and function as cathode electrodes, for example, when voltage is applied for electrophoresis or sample introduction.

[0013] The capillary head 112 bundles and bonds the capillary ends opposite the cathode end 127 of the capillary together. The capillary head 112 is connected to the block 107 in a pressure-tight and airtight manner. The pump mechanism 103 fills the interior of the capillary 102 with new polymer. The polymer in the capillary 102 is refilled after each measurement to improve measurement performance.

[0014] The optical system includes a light irradiation mechanism 114 for irradiating the detection section 116, an array holder 105 for holding the detection section 116, a spectroscope 132 for dispersing the light emitted from the detection section 116 into each wavelength, and a 2D detector 115 for detecting the dispersed light. To detect a sample separated by electrophoresis in the capillary 102, the light irradiation mechanism 114 irradiates the detection section 116, the spectroscope 132 disperses the light emitted from the detection section 116, and the 2D detector 115 detects the dispersed light.

[0015] The thermostat bath 118 is covered with a thermally insulating material, and its interior is controlled to a constant temperature by a heating and cooling mechanism 120. A fan 119 circulates and moves the air in the thermostat bath 118 to maintain a uniform and constant temperature of the capillary array 117.

[0016] The pumping mechanism 103 includes a plunger pump 106, a block 107, a check valve 108, a motorized valve 113, a polymer reservoir 109, and an anode buffer reservoir 110. The block 107 includes a flow path connecting the plunger pump 106, the polymer reservoir 109, the anode buffer reservoir 110, and the capillary array 117. The flow path between the plunger pump 106 and the polymer reservoir 109 includes a check valve 108 to prevent backflow of the polymer. The flow path between block 107 and anode buffer reservoir 110 contains a motorized valve 113. Motorized valve 113 closes to prevent buffer solution from flowing out of anode buffer reservoir 110 when plunger pump 106 fills chamber 128 and capillary array 117 with polymer. During electrophoresis, motorized valve 113 opens to energize anode electrode 111 and capillary cathode end 127.

[0017] The transport mechanism 125 contains three electric motors and linear actuators (not shown) and can move in three axes: vertical, horizontal, and depth. One or more containers can be placed on the movable stage 130 of the transport mechanism 125. The movable stage 130 also contains an electric gripper 131 that can grip and release containers. The buffer container 121, the wash container 122, the waste container 123, and the sample container 124 can be transported to the loading head 129 as needed. Unused containers are stored in a designated storage space within the facility.

[0018] The description below outlines false signals due to spectral shifts. Fig. Figure 2 is a diagram illustrating a state in which a DNA band separated by electrophoresis moves within the capillary. Condensed laser light is irradiated onto the detection section 116 of the capillary 102 and includes an irradiation area 702 with a predetermined width. The signal detected by the 2D detector 115 changes as a DNA band 701 enters and leaves the laser light irradiation area 702. Since the migration direction is the same as the wavelength dispersion direction, the DNA band 701 moves in the wavelength dispersion direction while passing through the laser light irradiation area 702. The emission spectrum 703 of the signal detected by the 2D detector 115 obviously changes, as shown in Fig. 3 shown.

[0019] Fig. 3 is a diagram illustrating a change in the emission spectrum. The Fig. The spectral shift shown in Figure 3 produces the same effect as the time-dependent change in the wavelength of the emission spectrum 703 as the DNA band 701 passes through the laser light irradiation area 702. The electrophoresis uses multiple fluorescent dyes corresponding to four types of bases. An obvious change in the emission spectrum 703 prevents complete correspondence (matrix transformation) between the observed emission spectrum 703 and each fluorescent dye or base. The matrix transformation applied to each component of the emission spectrum 703 generates a false signal as a residual component that cannot be transformed. The false signal reduces the ability to identify fluorescent dyes or leads to misdiagnosis. An increase in the laser light irradiation area 702 increases the false signal due to spectral shifts. First embodiment

[0020] Fig. 4 is a schematic diagram illustrating a laser light path in an optical irradiation system of the electrophoresis device according to the first embodiment. The light irradiation mechanism 114 according to the present embodiment includes a laser unit 201 as a light source for oscillating a laser light 202, a beam splitter 205 for splitting the laser light 202 into two, a reflecting mirror 203 for changing the path of the laser light 202, and a condenser lens 206 for condensing the laser light 202. A polarization-dependent optical isolator 204 is inserted in the optical path between the laser unit 201 and the beam splitter 205. The reflecting mirror 203 guides one of the laser lights 202 split by the beam splitter 205 below the capillary array and the other above the capillary array.Each laser light 202 is condensed by the condenser lens 206 and then enters the capillary array from the top or bottom end. The 2D detector 115 detects the fluorescence emitted by the detection section 116 of each capillary 102.

[0021] While Fig. While FIG. 4 shows only five capillaries 102, the capillary array according to the present embodiment consists of 24 capillaries 102. Each capillary 102 is aligned and fixed to the reference base 207 in the detection section 116. Throughout the description, the capillary array plane refers to a virtual plane formed by the central axis (capillary axis) of each capillary on the reference base 207. The optical axis 208 refers to a virtual line belonging to the capillary array plane and perpendicular to each capillary axis. While the present embodiment configures the capillary array of 24 capillaries 102, the number of capillaries 102 is not limited to 24.

[0022] The description below explains the light-shielding principle of the polarization-dependent optical isolator 204 by referring to the Fig. 5A and Fig. 5B. Fig. Figure 5A is a diagram illustrating how laser light enters a polarization-dependent optical isolator in the forward direction, and Fig. 5B is a diagram illustrating how the returning light enters a polarization-dependent optical isolator in the reverse direction. The polarization-dependent optical isolator 204 includes a first polarizer 302a, a second polarizer 302b, and a Faraday rotator 301 disposed between the first polarizer 302a and the second polarizer 302b. The second polarizer 302b is installed by tilting the transmission axis 45° relative to the first polarizer 302a. The Faraday rotator 301 rotates the polarization direction 303 by a predetermined angle, regardless of the incident or polarization direction. The present embodiment uses the Faraday rotator 301, which rotates the polarization direction by 45°.The direction of rotation of the polarization direction 303 rotated by the Faraday rotator 301 based on forward incident light is opposite to that of the polarization direction 303 rotated by the Faraday rotator 301 based on backward incident light.

[0023] When the laser light, as in Fig. 5A, the laser light enters the polarization-dependent optical isolator 204 in the forward direction, passes through the first polarizer 302a, allows the polarization direction to be rotated by 45° by the Faraday rotator 301, and enters the second polarizer 302b. The laser light passes through the second polarizer 302b, whose transmission axis is tilted by 45°.

[0024] If the returning light, as in Fig. 5B, the returning light enters the polarization-dependent optical isolator 204 in the reverse direction, passes through the second polarizer 302b, allows the polarization direction to be rotated by 45° in the direction opposite to the forward direction by the Faraday rotator 301, and enters the first polarizer 302a. The polarization direction of the returning light at this time is perpendicular to the transmission axis of the first polarizer 302a, allowing the first polarizer 302a to shield the returning light.

[0025] The description below outlines the reflected returning light and the transmitted returning light by reference to Fig. 6. Fig. Figure 6 is a conceptual diagram showing the transmitted and reflected returning light when laser light is irradiated onto a capillary array. Fig. Figure 6 shows that the incident light on the capillary array is slightly tilted relative to the direction perpendicular to the capillary axis to facilitate understanding of the transmitted and reflected light from the capillary array.

[0026] The laser light 202 incident on the capillary array is reflected by the interface between the air and an outer wall of the capillary and the interface between an inner wall of the capillary and the gel. In particular, the former interface increases a refractive index and consequently increases the intensity of the reflected light. A capillary contains two interfaces between the air and the outer wall of the capillary. The capillary array consisting of 24 capillaries causes a total of 48 reflections to occur at the interface between the air and the outer wall of the capillary. When the reflected returning light 401 from the capillary array reaches the laser unit 201 as the light source, the laser unit 201 causes unstable laser oscillation.

[0027] The transmitted return light 402 passes through the capillary array and is emitted from the side opposite the incident side. Compared to the incident light, the transmitted return light 402 is attenuated by the amount of reflected light. When the transmitted return light 402 reaches the laser unit 201, the laser unit 201 causes unstable laser oscillation.

[0028] Fig. Figure 7A is a diagram illustrating the linear polarization states of the laser light and its transmitted return light when the laser light enters the polarization-dependent optical isolator and is then irradiated from below onto the capillary array. The xy planes in Fig. 7A are perpendicular to the direction of the laser light and illustrate linear polarization states at the corresponding positions (similar to the Fig. 7B, Fig. 9A and Fig. 9B). Fig. Figure 7 omits the mirrors and shows point A as the beam splitter position. The laser light emitted by the laser unit 201 enters the polarization-dependent optical isolator 204, maintaining the linear polarization state in the x-axis direction. The laser light enters the polarization-dependent optical isolator 204 in the forward direction and passes through it by rotating the linear polarization by 45°, as shown in Fig. 5A. The laser light passes straight through the beam splitter (point A) and enters the capillary array 117 from below, maintaining the polarization angle of 45°. The transmitted returning light passes through the capillary array 117, travels along the other laser path, re-enters the polarization-dependent optical isolator 204 in the reverse direction, and is shielded by the first polarizer 302a, as shown in Fig. 5B. Although in Fig. 7A, the reflected returning light follows the path of the incident light and enters the polarization-dependent optical isolator 204 with the same polarization angle and is thus shielded similarly to the transmitted returning light.

[0029] Fig. Figure 7B is a diagram illustrating the polarization states of the laser light and its transmitted return light when the laser light enters the polarization-dependent optical isolator and is then irradiated from above onto the capillary array. Similar to Fig. 7A, the laser light emitted by the laser unit 201 enters the polarization-dependent optical isolator 204 while maintaining the linear polarization state in the x-axis direction, and passes through the polarization-dependent optical isolator 204 by rotating the linear polarization by 45°. The laser light reflected by the beam splitter (point A) enters the capillary array 117 from above while maintaining the polarization angle of 45°. The transmitted returning light passes through the capillary array 117, follows the other laser path, then re-enters the polarization-dependent optical isolator 204, and is shielded by the first polarizer 302a, similar to the case in Fig. 7A. Although in Fig. 7B, the reflected returning light follows the path of the incident light, enters the optical isolator with the same polarization angle, and is consequently shielded similarly to the transmitted returning light.

[0030] Even if the laser light irradiated onto the capillary array disturbs the polarization state and changes the polarization angle of the returning light, only the linear polarization with a polarization angle of 45° passes through the second polarizer 302b and enters the Faraday rotator 301, as shown in Fig. 5B according to the present embodiment. The Faraday rotator 301 rotates the polarization direction of the returning light in the direction opposite to the forward direction, allowing the first polarizer 302a to shield the returning light. The polarization-dependent optical isolator according to the present embodiment reliably shields the returning light even if the laser light irradiated onto the capillary array disturbs the linear polarization state. It is possible to use laser units that are less resistant to returning light, increasing the degree of freedom in selecting laser devices. The laser light is irradiated from both ends of the capillary array along the same optical axis perpendicular to the capillary axis, thereby narrowing the irradiation area of ​​the laser light and reducing false signals due to spectral shifts.As a result, the performance of the electrophoresis device in sample separation is improved. Second embodiment

[0031] The description below explains the optical irradiation system of the electrophoresis apparatus according to the second embodiment by referring to the Fig. 8A to 9B. Unlike the first embodiment, the light irradiation mechanism 114 according to the present embodiment functions as an optical isolator and includes a polarization-independent optical isolator 801.

[0032] As in Fig. 8A and Fig. 8B, the polarization-independent optical isolator 801 includes a first birefringent crystal 803a, a second birefringent crystal 803b, the Faraday rotator 301 disposed between the first birefringent crystal 803a and the second birefringent crystal 803b, a half-wave plate 802 disposed between the first birefringent crystal 803a and the second birefringent crystal 803b, and a pinhole plate 804.

[0033] The present embodiment uses the half-wave plate 802 and the Faraday rotator 301, which is the same as the one used in the first embodiment. Like the Faraday rotator 301, the half-wave plate 802 rotates the polarization direction by 45°. Unlike the Faraday rotator 301, the direction of rotation of the polarization direction 303 rotated by the half-wave plate 802 based on forward incident light is the same as the polarization direction 303 rotated by the half-wave plate 802 based on backward incident light.

[0034] Fig. 8A is a diagram showing an optical path of the laser light entering the polarization-independent optical isolator in the forward direction and the polarization direction at each position as viewed from the beam propagation direction. The laser light 202 traveling in the forward direction passes through a pinhole of the pinhole plate 804 and enters the first birefringent crystal 803a. The first birefringent crystal 803a splits the laser light 202 into an ordinary beam 806 and an extraordinary beam 807, which differ in polarization directions by 90° due to refractive index differences in the respective axial directions. According to the present embodiment, the polarization of the ordinary beam 806 is perpendicular to the plane in Fig. 8A. The Faraday rotator 301 rotates the beams by 45°, which are then rotated by a further 45° in the same direction by the half-wave plate 802 to rotate the polarization direction by a total of 90°, and are recombined by the second birefringent crystal 803b.

[0035] Fig. 8B is a diagram showing an optical path of the returning light entering the polarization-independent optical isolator in the reverse direction and the polarization direction at each position as viewed from the beam propagation direction. The returning light 808 traveling in the reverse direction enters the second birefringent crystal 803b and is split into the ordinary beam 806 and the extraordinary beam 807. The half-wave plate 802 rotates the beams by 45°, which are then rotated another 45° in the reverse direction by the Faraday rotator 301 and enter the first birefringent crystal 803a, with the polarization direction remaining unchanged. The polarization direction of each beam in the first birefringent crystal 803a remains unchanged after passing through the second birefringent crystal 803b.The beams are not recombined, pass separately through the first birefringent crystal 803a and are shielded by the pinhole plate 804.

[0036] Fig. Figure 9A is a diagram showing the linear polarization states of the laser light and its transmitted return light when the laser light enters the polarization-independent optical isolator and is then irradiated from below onto the capillary array. The laser light enters and passes through the polarization-independent optical isolator 801 in the forward direction, as shown in Fig. 8A. The laser light passes straight through the beam splitter (point A) and then enters the capillary array 117 from below. The transmitted returning light passes through the capillary array 117, follows the other laser path, re-enters the polarization-independent optical isolator 801 in the reverse direction, and is shielded by the pinhole plate 804. Although in Fig. 9A, the reflected returning light follows the path of the incident light, then re-enters the polarization-independent optical isolator 801 and is shielded like the transmitted returning light.

[0037] Fig. Figure 9B is a diagram showing the linear polarization states of the laser light and its transmitted return light when the laser light enters the polarization-independent optical isolator and is then irradiated from above onto the capillary array. The laser light enters and passes through the polarization-independent optical isolator 801 similarly to Fig. 9A. The laser light reflected by the beam splitter (point A) enters the capillary array 117 from above. The transmitted returning light passes through the capillary array 117, follows the other laser path straight, re-enters the polarization-independent optical isolator 801, and is shielded by the pinhole plate 804. Although in Fig.9B, the reflected returning light follows the path of the incident light, then re-enters the polarization-independent optical isolator 801 and is shielded like the transmitted returning light.

[0038] The polarization-dependent optical isolator according to the first embodiment provides a high level of returning light suppression because the polarizer shields light other than that with a specific polarization angle despite changes in the returning light. The polarization-independent optical isolator according to the present embodiment can also be expected to provide a certain level of returning light suppression. The present embodiment can also use laser units that are less resistant to returning light, increasing the degree of freedom in selecting laser devices. The narrow irradiation area of ​​the laser light reduces false signals due to spectral shifts, improving the sample separation performance of the electrophoresis device.

[0039] The present invention is not limited to the above-described embodiments and further includes various modifications. For example, the above-described embodiments utilize an optical isolator on the optical path from the light source to the beam splitter. Alternatively, it may be advantageous to provide an optical isolator on each optical path after splitting by the beam splitter. List of reference symbols

[0040] 101: Electrophoresis device, 102: Capillary, 103: Pumping mechanism, 104: High-voltage power supply, 105: Array holder, 106: Plunger pump, 107: Block, 108: Check valve, 109: Polymer container, 110: Anode buffer container, 111: Anode electrode, 112: Capillary head, 113: Motorized valve, 114: Light irradiation mechanism, 115: 2D detector, 116: Detection section, 117: Capillary array, 118: Thermostatic bath, 119: Fan, 120: Heating and cooling mechanism, 121: Buffer container, 122: Wash container, 123: Waste container, 124: Sample container, 125: Transport mechanism, 126: hollow electrode, 127: capillary cathode end, 128: chamber, 129: loading head, 130: movable stage, 131: gripper, 201: laser unit, 202: laser light, 203: reflecting mirror, 204: polarization-dependent optical isolator, 205: beam splitter, 206: condenser lens, 207: reference base, 208: optical axis, 301: Faraday rotator, 302a: first polarizer, 302b: second polarizer, 303: polarization direction,401: reflected returning light, 402: transmitted returning light, 701: DNA band, 702: irradiation region, 703: emission spectrum, 801: polarization-independent optical isolator, 802: half-wave plate, 803a: first birefringent crystal, 803b: second birefringent crystal, 804: pinhole plate, 806: ordinary ray, 807: extraordinary ray, 808: returning light,

Claims

[1] An electrophoresis device that irradiates a laser light from both ends of a capillary array consisting of a plurality of capillaries arranged in a row and detects light from the capillaries, wherein an optical isolator is provided on an optical path from a light source of the laser light to the capillary array. [2] The electrophoresis device according to claim 1, wherein the laser light is irradiated from both ends of the capillary array along the same optical axis which is perpendicular to a capillary axis and parallel to an arrangement plane of the capillary array. [3] An electrophoresis device according to claim 1, comprising: a beam splitter that splits the laser light emitted by the laser light source; and a mirror that directs the split laser light to one side and to the other side of the capillary array, wherein the optical isolator is provided on an optical path from the light source to the beam splitter. [4] The electrophoresis device according to claim 1, wherein the optical isolator is a polarization-dependent optical isolator including a first polarizer, a second polarizer, and a Faraday rotator disposed between the first polarizer and the second polarizer. [5] The electrophoresis device according to claim 1, wherein the optical isolator is a polarization-independent optical isolator including a first birefringent crystal, a second birefringent crystal, a Faraday rotator disposed between the first birefringent crystal and the second birefringent crystal, and a half-wave plate disposed between the first birefringent crystal and the second birefringent crystal.

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