WO2021048962A1 - Light-scattering detection device - Google Patents

Abstract

The present invention provides a light-scattering detection device 100 for detecting fine particles in a liquid sample, comprising: a sample cell 17 that has a flow path for holding the liquid sample and an external cross-sectional shape that is circular; a light source 1 for emitting laser light toward the flow path from a direction perpendicular to the axis of the sample cell 17; and a plurality of photodetectors 9 that are arranged along a prescribed circle E that is within a plane perpendicular to the axis, is centered on the axis, and is outside the sample cell 17. Of the lateral surfaces of the flow path, a lateral surface facing at least one of the plurality of photodetectors 9 is a flat surface.

Description

Light scattering detector

The present invention relates to a light scattering detection device.

Size exclusion chromatography (SEC) and gel filtration chromatography (GPC) are known as methods for separating fine particles having a relatively large molecular weight such as proteins and polymers dispersed in a liquid sample. One of the detectors for fine particles separated by these methods is a multi-angle light scattering detector (hereinafter referred to as a MALS detector).

The MALS detector includes a cell that holds a liquid sample introduced from a liquid chromatograph such as SEC or GPC, a light source that irradiates the liquid sample held in the cell with a laser beam, and a plurality of detectors. .. A cylindrical cell is usually used in a MALS detector, and a liquid sample held in the cell is irradiated with light from a light source from a direction perpendicular to the central axis of the cell. When the light from the light source passes through the liquid sample, the light is radiated with a scattering cross section depending on the fine particles contained in the liquid sample in the passage path, and exits from the cell. A plurality of detectors are arranged so as to surround the center of the cell so that the light emitted from the liquid sample (cell) in a plurality of directions can be detected at the same time. Then, the relationship between the scattering angle and the scattering cross section is obtained from the intensity of the scattered light obtained by the plurality of detectors, and the molecular weight and size (turning radius) of the unknown substance in the liquid sample are calculated from this relationship. ..

There are roughly two types of cells used in the MALS detector. In the first type of cell, a through hole for holding a liquid sample is formed in the radial direction of the cylindrical cell, and the light from the light source is emitted from one end to the other end of the through hole. The cell is irradiated so as to pass through the through hole toward the (see Patent Document 1). On the other hand, in the second type cell, a through hole for holding a liquid sample is formed in the direction of the central axis of the cylindrical cell, and the light from the light source is formed in the cell so as to cross the through hole. It is irradiated (see Patent Document 2).

The first type cell functions as a cylindrical lens with respect to the light scattered by the liquid sample (fine particles contained in the liquid sample) in the path of the irradiation light. Therefore, in the MALS detection device using this cell, various angular components (angle components) of the scattered light are collected by the cell. Since the detector is arranged at the condensing position of each angle component, the intensity of each angle component can be detected by the corresponding detector.

However, since the first type cell allows light from the light source to pass along the through hole, the flow path for introducing the liquid sample from the chromatograph into the through hole does not interfere spatially with the light source, and the penetration thereof. In order to prevent the scattered light from the flow path for discharging the liquid sample from the hole from becoming unnecessary noise light, it is necessary to provide a bending portion that bends at a right angle in the vicinity of both ends of the through hole in the introduction flow path and the discharge flow path. At the bending site, the conductance of the liquid sample flowing through the flow path is greatly modulated. Such conductance modulation reduces the measurement accuracy of the chromatograph.

Further, in the first type cell, since the scattered light generation region corresponds to the diameter of the cell, the spherical aberration is large. When the scattered light of the angular component having a large aberration is added to the scattered light of the angular component in the vicinity as noise, there is a problem that the angular resolution is reduced.

On the other hand, in the MALS detection device using the second type cell, the light from the light source irradiates the cell so as to cross the through hole, so that the introduction flow paths provided on both ends of the through hole of the cell are provided. And the discharge channel does not interfere with the light from the light source. The second type cell has a circular outer and inner circumference (that is, the side surface of the through hole), and the interface between the liquid sample flowing through the through hole and the cell and the interface between the cell and air are optically formed. The function as a cylindrical lens is the same as that of the first type. However, since the light emitting region is limited to a narrow region near the center of the cell, the problem of spherical aberration is much smaller when the second type cell is used. Therefore, a MALS detector using a second type cell is useful as a detector for chromatographically separated fine particles.

Japanese Patent Application Laid-Open No. 07-072068 Japanese Unexamined Patent Publication No. 2008-032548

Normally, quartz glass, which is a general material for optical members, is used as the cell material. Since the refractive index (1.46) of quartz glass is larger than the refractive index (1.0) of air, the interface between the cell and air always has a converging action. On the other hand, since various kinds of solvents are used as mobile phases in chromatography, the refractive index of the solvent of the liquid sample introduced from the chromatograph is wide. Therefore, depending on the magnitude relationship between the refractive index of the liquid sample (solvent) and the refractive index of the cell, the interface between the liquid sample and the cell has a high refractive index / low refractive index interface having a converging action and a low refractive index / having a divergent action. It can be any of the high index interfaces. That is, whether the interface between the liquid sample and the cell has a converging action or a dispersing action depends on the refractive index of the solvent of the liquid sample.

When the interface between the liquid sample and the cell has a divergent action, the scattered light generated in the liquid sample can be taken out from the cell as parallel light by canceling the convergence action at the interface between the cell and the air. On the other hand, when the interface between the liquid sample and the cell has a converging action, the scattered light is more strongly converged by being superimposed on the converging action of the interface between the cell and the air, and a focal point is formed in the immediate vicinity of the cell. Since the scattered light after passing through the focal point continues to diverge, it cannot be made into parallel light. If an imaging element such as a lens, a diffractive element, or a curved mirror is placed between the sample cell and the detector, the emitted light can be condensed to some extent, but if the difference in refractive index between the solvent and the cell becomes large, the imaging element It becomes difficult for some children to collect light at a desired position.

An object to be solved by the present invention is to enable a light scattering detection device to detect the intensity of scattered light generated in a liquid sample regardless of the refractive index of the solvent of the liquid sample.

The present invention made to solve the above problems
A light scattering detector for detecting fine particles in a liquid sample.
A sample cell having a circular outer cross-sectional shape and having a flow path for holding a liquid sample,
A light source that irradiates a laser beam from a direction perpendicular to the axis of the sample cell toward the flow path,
A plurality of photodetectors arranged on a predetermined circumference outside the sample cell centered on the axis in a plane perpendicular to the axis are provided.
The present invention relates to a light scattering detection device in which a side surface of the flow path facing at least one of the plurality of photodetectors is a flat surface.

In the light scattering detection device according to the present invention, when the laser light from the light source is irradiated toward the flow path in the sample cell, the laser light is oriented in various directions due to the fine particles contained in the liquid sample in the flow path. It is scattered and radiated from the sample cell. The various angular components (angle components) of the scattered light generated in the flow path are the interface between the solvent of the liquid sample and the sample cell, and the external space between the sample cell and the sample cell before coming out of the sample cell. Pass through the interface with.

In the present invention, since the side surface of the flow path facing at least one of the plurality of detectors is a plane, the angular component of the scattered light generated in the flow path that passes through this side surface (plane side surface) is determined. Although it is refracted on the plane side surface, it heads toward the interface between the sample cell and the external space as parallel light while maintaining the wave plane of the plane wave. Generally, the refractive index of the sample cell is larger than the refractive index of the external space (air), and in the present invention, the cross-sectional shape of the outer shape of the sample cell is circular, so that the interface between the sample cell and the external space is Has a convergence effect. Therefore, the angular component of the scattered light that has passed through the plane side surface of the flow path and directed toward the interface between the sample cell and the external space as parallel light is centered on the axis of the sample cell regardless of the refractive index of the liquid sample solvent. Focus on a predetermined circumference. Since a plurality of photodetectors are arranged on the predetermined circumference, the light that faces the angular component of the scattered light that has passed through the plane side surface regardless of the refractive index of the solvent of the liquid sample. It can be detected by a detector.

In addition, "the plane side surface faces at least one of a plurality of photodetectors" is not limited to the case where the plane side surface and the photodetector face each other, and the flow with at least one of the plurality of photodetectors. It means that the plane side surface is in a position that contributes to the detection by the detector between the scattered light generation region in the road. That is, it is sufficient that at least one of the plurality of photodetectors is arranged at a position where the angular component of the scattered light generated in the scattered light generation region in the flow path and passed through the plane side surface can be detected.

A schematic overall configuration diagram of a multi-angle light scattering detection device, which is a form of a conventional light scattering detection device. The figure which shows the positional relationship of a beam splitter, a sample cell, an imaging optical system, and a detector in a conventional multi-angle light scattering detection apparatus. Explanatory drawing of the generation area of scattered light when parallel light is incident on a liquid sample. Explanatory drawing of the parallel component of the scattered light emitted from the generation area of scattered light. Scattered light emitted in the normal direction from each generation region of scattered light of a liquid sample in which the refractive index n0 of the solvent is (a) 1.26, (b) 1.36, (c) 1.46, (d) 1.56, and (e) 1.66. Ray diagram. The schematic whole block diagram of the multi-angle light scattering detection apparatus which is one Embodiment of this invention. The cross-sectional shape of the through hole is (a) a ray diagram of each angle component of scattered light when a sample cell having a rectangular shape is irradiated with laser light, and (b) scattering when a sample cell having a square shape is irradiated with laser light. A ray diagram of each angle component of light. (C) A ray diagram of each angle component of the forward scattered light and (d) a ray diagram of each angle component of the back scattered light when a sample cell having an isosceles triangle cross-sectional shape is irradiated with laser light. The figure which shows the angular component of the scattered light passing through three planes of a through hole whose cross-sectional shape is an equilateral triangle. A ray diagram of each angle component when a sample cell having an equilateral triangular cross-sectional shape of the through hole is irradiated with laser light (solvent refractive index 1.33). FIG. 9 is a spot diagram for evaluating the angular resolution of the photodetector when an angular component having a scattering angle of 90 °, which is shown in FIG. 9, is detected by the photodetector. A ray diagram (solvent refractive index 1.66) showing a noise component generated when a sample cell having an equilateral triangular cross-sectional shape of the through hole is irradiated with a laser beam. The figure which shows the name of the interface used when explaining the behavior of the angular component of the scattered light at the solvent / cell interface when the cross-sectional shape of a through hole is an equilateral triangle. The figure which shows the optical path of the scattered light generated in the light emitting region when a laser beam passes through the midpoint of the upper left side and the lower left side of an equilateral triangle. The figure which shows the optical path of the scattered light generated in the light emitting region when a laser beam passes near the right side of an equilateral triangle. The figure which shows the contribution ratio of the noise component when a laser beam passes through the midpoint of the upper left side and the lower left side of an equilateral triangle. The figure which shows the contribution ratio of the noise component when a laser beam passes through the center of gravity of an equilateral triangle. The angle measurement diagram (a) and the general angle measurement diagram (b) used in the present specification. A ray diagram showing a state in which noise components are removed by providing slits at appropriate locations between the sample cell and the photodetector when the solvent refractive index is 1.66. Explanatory drawing of the ratio of the light flux width of the signal light and the noise component reflected by the lower left side of the through hole whose cross-sectional shape is an equilateral triangle when the refractive index of the solvent is small (a) and large (b). An explanatory diagram of the ratio of the noise component reflected forward at the upper left side of the through hole whose cross-sectional shape is an equilateral triangle and the luminous flux width of the signal light when the refractive index of the solvent is small (a) and large (b). Explanatory drawing of the ratio of the light flux width of the signal light and the noise component reflected rearward at the upper left side of the through hole whose cross-sectional shape is an equilateral triangle when the refractive index of the solvent is small (a) and large (b). Example of preparation of sample cell. Example of preparation of sample cell. Examples (a) to (c) of sample cells having through holes having different cross-sectional shapes of the through holes.

First, the conventional configuration of the light scattering detection device according to the present invention will be described by taking as an example a multi-angle light scattering detection device (MALS detection device), which is a form of the light scattering detection device.

<1. Conventional MALS detector>
<1.1 Overall configuration>
FIG. 1 shows a conventional general schematic configuration of a MALS detection device. The MALS detection device 100P surrounds the sample cell 7 at a predetermined angle θ on the cylindrical transparent sample cell 7 in which the liquid sample 71 is housed and the circumference E centered on the sample cell 7. It includes a plurality of arranged light detectors 8 and 9, and a laser light source 1 and an incoherent light source 2 that irradiate the sample cell 7 with light. Laser light, which is coherent light, is emitted from the laser light source 1, and incoherent light or partial coherent light is emitted from the incoherent light source 2.

The laser light emitted from the laser light source 1 and traveling along the optical path L1 and the incoherent light emitted from the incoherent light source 2 and traveling along the optical path L2 are alternately selected by the sector mirror 3 in the sample cell 7. It is sent to an optical path L3 having the same optical axis toward it. The sector mirror 3 is composed of, for example, a rotating plate in which reflecting portions and transmitting portions are alternately arranged. The rotating plate is rotationally driven in the same direction at a predetermined speed by a drive mechanism 4 such as a motor, and laser light is sent to the optical path L3 at the timing when the transmitting portion comes at the intersection of the optical paths L1 and L2, and in at the timing when the reflecting portion comes. Coherent light is sent to the optical path L3. In both the laser light and the incoherent light, the direction perpendicular to the same plane in which the photodetectors 8 and 9 are arranged is the polarization direction of the electric vector.

A beam splitter 5 is arranged on the optical path L3, and a part of the light radiated to the sample cell 7 is split and reflected by the beam splitter 5 and introduced into the intensity monitor detector 6. The detection signal of the intensity monitor detector 6 is input to the data processing unit 11 and used to correct fluctuations in the emission intensity of the light sources 1 and 2.

Of the plurality of photodetectors arranged on the circumference E, the photodetector 8 arranged on the extension of the optical path L3 in a plan view is a detector for measuring the transmitted absorbance, and all the other photodetectors 9 are. It is a detector for multi-angle scattering measurement. The detection signal by the photodetector 8 is input to the concentration calculation unit 13 included as a function in the data processing unit 11, while the detection signal by the plurality of photodetectors 9 is a particle information calculation unit included as a function in the data processing unit 11. It is input to 12.

<1.2 Operation of MALS detector>
In the MALS detection device 100P having the above configuration, the laser light emitted from the light source 1 travels along the optical path L1, and the incoherent light emitted from the light source 2 travels along the optical path L2. Since these light fluxes are periodically and alternately selected by the sector mirror 3 and sent to the optical path L3, the liquid sample 71 in the sample cell 7 is alternately irradiated with the laser beam and the incoherent light. The drive mechanism 4 that drives the sector mirror 3 is controlled by the control unit 10. The control unit 10 sends a timing control signal indicating which of the laser beam and the incoherent light is the period during which the sample 71 is irradiated to the data processing unit 11 in synchronization with the rotation position of the sector mirror 3.

When the sample cell 7 is irradiated with incoherent light, the intensity of the transmitted light reflects the absorption by the sample 71. Therefore, the data processing unit 11 reads the detection signal of the photodetector 8 during the period in which the incoherent light is irradiated. The concentration calculation unit 13 calculates the absorbance of the sample 71 based on this detection signal, and calculates the concentration of the fine particles in the sample 71. The calculated concentration value is sent to the particle information calculation unit 12.

On the other hand, when the sample cell 7 is irradiated with the laser beam, when the laser beam passes through the liquid sample 71, it is scattered by the fine particles contained in the liquid sample 71 with different angular distributions and comes out of the sample cell 7. Therefore, the data processing unit 11 simultaneously reads the detection signals of the plurality of photodetectors 9 during the period in which the sample 71 is irradiated with the laser beam. The particle information calculation unit 12 calculates the scattered light intensity at each angular position based on these detection signals. The particle information calculation unit 12 calculates the molecular weight, turning radius, and the like of the fine particles contained in the sample 71 based on the scattered light intensity at each angular position and the concentration value of the fine particles in the sample.

<1.3 Positional relationship between beam splitter, sample cell and photodetector>
FIG. 2 is a schematic view showing the positional relationship between the beam splitter 5, the sample cell 7, and the photodetector 9 in the MALS detector 100P. In FIG. 2, since it is a side view, it seems that the photodetector 9 is located on the extension of the optical path L3, but in reality, all of the plurality of detectors 9 are located outside the extension of the optical path L3. is there.

As shown in FIG. 2, an imaging optical system 20 composed of a slit plate 21 having a slit for limiting scattered light and a plano-convex lens 22 is arranged between the sample cell 7 and the photodetector 9. The slit of the slit plate 21 has a vertically long rectangular shape in order to limit the scattering angle in the horizontal direction and to take in a large amount of light flux in the vertical direction.

In the MALS detection device 100P, the sample cell 7 and the imaging optics so that the components (angle components) of the scattered light emitted from the sample cell 7 in various angular directions are focused on the light receiving surface of the corresponding photodetector 9. The arrangement of the system 20 and the photodetector 9 is set. In order for each angle component of the scattered light emitted from the sample cell 7 to be focused on the light receiving surface of the photodetector 9 after passing through the imaging optical system 20, each angle component should be as close to parallel light as possible. It is desirable that the light is incident on the imaging optical system 20.

The sample cell 7 has a through hole having a circular cross section formed along the central axis thereof, and the liquid sample 71 is housed in the through hole. Therefore, the through hole corresponds to the flow path of the present invention. The laser beam emitted to the sample cell 7 is scattered by the fine particles contained in the liquid sample 71 when crossing the through hole, and is scattered at the interface between the liquid sample 71 (solvent) and the sample cell 7, and the sample cell 7 and its outside ( Generally, after passing through the interface with air), the sample cell 7 emits light. Whether or not each angular component of the scattered light generated in the liquid sample 71 is emitted from the sample cell 7 as parallel light depends on the optical function of these interfaces. The optical function of the interface of the sample cell 7 in the conventional MALS detection device 100P is as follows.

<1.4 Optical function of the interface of the sample cell>
FIG. 3 shows a laser having a wavelength of 660 nm and a width of 50 μm from a semiconductor laser light source for a cylindrical sample cell 7 made of synthetic quartz (refractive index n1 = 1.46) having an outer diameter of 8 mm and an inner diameter of 1.6 mm. FIG. 5 is a light ray diagram when light (parallel light) is incident so as to penetrate the center of the sample cell 7. The sample cell 7 on the left side of FIG. 3 holds a liquid sample 71 having a solvent refractive index n0 of 1.26, and the sample cell 7 on the right side holds a liquid sample 71 having a solvent refractive index n0 of 1.66. ..

From FIG. 3, the light beam incident on the liquid sample 71 from the sample cell 7 is large regardless of whether the refractive index n0 of the solvent is smaller than the refractive index n1 of the sample cell 7 (left side) or larger (right side). It can be seen that the sample passes through the liquid sample 71 in a state of being substantially parallel without being converged or diverged. Born approximation is established from the width of the light beam and the ratio of the inner diameter to the outer diameter of the sample cell 7 and from the intensity ratio of the laser light and the scattered light, and the influence of multiple scattering can be excluded. Therefore, a region in which scattered light is generated when a laser beam is incident on the liquid sample 71 housed in the through hole of the sample cell 7 is formed by a line segment having a length corresponding to the inner diameter of the sample cell 8 and having no width. It can be approximated as a light emitting region).

<1.5 Convergence and divergence at the inner and outer interfaces of the sample cell>
Scattered light is emitted from the above-mentioned light emitting region in various directions. Here, as shown in FIG. 4, the azimuth of the laser light incident on the sample cell 7 is 0 ° from one side of the light emitting region. If the azimuth angle of scattered light is defined as θ0, consider parallel scattered light emitted at equal intervals (direction where θ0 = 90 °). Then, after such scattered light passed through each interface, the optical path until it was emitted from the sample cell 7 was traced. In the following description, for convenience, only half of the scattered light emitted in the normal direction will be dealt with.

In FIG. 5, the refractive index n0 of the solvent is 1.26 ((a), for example, fluorescent solvent), 1.36 ((b), for example, ethanol), 1.46 ((c), for example, fluorobenzene), 1.56 ((d), for example, nitrobenzene). ), 1.66 ((e), for example, quinoline) is a ray diagram of scattered light emitted in the normal direction from the light emitting region of the liquid sample 71. Hereinafter, unless otherwise specified, air exists in the external space of the sample cell 7, and its refractive index n2 is 1.0. At the interface between the liquid sample 71 and the sample cell 7 (hereinafter referred to as the "solvent / cell interface"), when n0 <n1 (when FIGS. 5A and 5B), the lens functions as a divergent lens, and n0> n1. When ((d), (e)), it functions as a focusing lens. When n0 = n1 (when (c)), the light beam travels straight without being refracted at the solvent / cell interface.

On the other hand, since the relationship between the refractive index n1 of the sample cell 7 and the refractive index n2 of the external space is always n1> n2, the interface between the sample cell 7 and the external space (hereinafter referred to as “cell / air interface”) is always a convergent lens. Functions as. Therefore, as shown in FIG. 5, in the cases (a) and (b) where the solvent / cell interface functions as a divergence lens, the divergence and convergence cancel each other out, and in the case of (b) in particular, the parallel components of the scattered light. Most of them are emitted from the sample cell 7 as substantially parallel rays.

On the other hand, when the solvent / cell interface does not function as a lens (c), the cell / air interface converges, and the solvent / cell interface functions as a condensing lens (d) and (e). In the case, the light emitted from the sample cell 7 is focused on a predetermined focal point by superimposing the convergence action. However, in the case of (e), which has a strong convergence effect, the focus is focused in the immediate vicinity of the sample cell 7, and the divergence continues after that.

In this way, whether the light emitted from the sample cell 7 is divergent light, parallel light, or convergent light, and where the focal point is located in the case of convergent light, depends on the refractive index n0 of the solvent and the refraction of the sample cell. It depends on the magnitude relationship of the rate n1.

This means that the conventional MALS detector cannot accurately measure the scattered light intensity or cannot measure it at all depending on the refractive index of the solvent of the liquid sample to be measured. In order to be able to measure the scattered light intensity regardless of the refractive index of the solvent, the sample cells with different refractive indexes are replaced according to the refractive index of the solvent of the liquid sample, or the position of the light receiving surface of the light detector is changed. It is conceivable to change or arrange a condensing optical system having an appropriate configuration between the sample cell and the detector. However, in a MALS detector for measuring a liquid sample having a wide range of refractive index of a solvent, such as a liquid sample introduced from a chromatograph, the sample cell may be replaced according to the refractive index of the solvent, or the detector may be replaced. It is almost impractical to change the arrangement or the configuration of the condensing optical system.

Of the interfaces through which scattered light generated in the light emitting region passes before exiting from the sample cell, the refractive index of the solvent contributes only to the solvent / cell interface. In other words, the reason why the scattered light emitted from the sample cell becomes divergent light, parallel light, or convergent light is that the scattered light crosses the solvent / cell interface depending on the refractive index of the solvent of the liquid sample. This is because the behavior when passing is different.

The angular component of the scattered light generated in the light emitting region has a plane wave surface. When a plane wave ray passes through a planar interface, the ray is refracted at the interface, but its wave surface is retained. That is, if the solvent / cell interface is made flat, all the angular components of the scattered light are parallel light and go from the solvent / cell interface to the cell / air interface. Since the cell / air interface has a converging effect, it is expected that the individual angular components of the scattered light will be focused on the circumference centered on the axis of the sample cell 7, regardless of the refractive index of the solvent. The present invention has been made based on such findings.
Hereinafter, the light scattering detector according to the present invention will be described by taking as an example a multi-angle light scattering detection device (MALS detection device) which is an embodiment thereof.

[Embodiment]
<1. Configuration of MALS detector>
FIG. 6 is a schematic overall configuration diagram of the MALS detection device 100 of the present embodiment. The MALS detection device 100 has substantially the same configuration as the conventional MALS detection device 100P shown in FIG. Therefore, in the configuration of the MALS detection device 100, the same or corresponding parts as the MALS detection device 100P are designated by the same reference numerals, the description thereof will be omitted, and the different parts will be mainly described.

The MALS detection device 100 of the present embodiment has a different configuration of through holes in the sample cell 17 from the sample cell 7. Specifically, the sample cell 17 has a flat side surface facing at least one of the photodetectors 9 among the side surfaces of the through hole. Such a flat side surface (flat side surface) can be obtained, for example, by forming a through hole having a circular cross-sectional shape inside the sample cell and processing a part of the side surface, but at least a part of the side surface is straight. A through hole having a closed curve may be formed inside the sample cell 17. In this configuration, the side surface of the plane is formed in the entire axial direction of the sample cell 17. Examples of closed curves include, but are not limited to, polygons, sectors, and shapes surrounded by strings and arcs with the same end points. However, the through hole of the conventional sample cell 7 having a circular cross-sectional shape and all the side surfaces having a curved surface is excluded. When the cross-sectional shape is polygonal, all the side surfaces of the through hole are composed of a plurality of plane side surfaces. Further, the MALS detection device 100 does not include an imaging optical system arranged between the sample cell 7 and the photodetector 9 in the conventional MALS detection device 100P.

<2. Behavior of scattered light in a sample cell with a polygonal cross-sectional shape of the through hole>
For the sake of simplicity, the behavior of individual angular components of scattered light when the sample cell 17 having a polygonal cross-sectional shape of the through hole of the sample cell 17 is irradiated with the laser beam will be described. In FIGS. 7A and 7B, the material of the sample cell 17 is synthetic quartz (refractive index n1 = 1.46), the solvent is water (refractive index n0 = 1.333), the outer diameter (radius) of the sample cell 17 is 4 mm, and the cross section of the through hole. The shape is a rectangle (a), a square (b), and an isosceles triangle (c), (d) with an area approximately equal to a circle with a radius of 0.8 mm, and the laser beam is emitted from the bottom to the top of the paper surface. It is a ray diagram of the angular component of the scattered light when penetrating the center of 17.
Unless otherwise specified, the material of the sample cell 17 is synthetic quartz (refractive index n1 = 1.46) in the following description.

Since the rectangle and the square have a symmetry having a two-fold rotation axis and a four-fold rotation axis, respectively, in the sample cell 17 having a rectangular and square cross-sectional shape of the through hole ((a) and (b) in FIG. 7A), the right side. Only the angular component of the forward scattering (scattering angle is 10 ° interval from 10 ° to 90 °) is shown. Further, since the isosceles triangle has different modes of forward scattering and backscatter due to its symmetry, in the sample cell 17 ((c), (d) of FIG. 7B) in which the cross-sectional shape of the through hole is an isosceles triangle, Only the angular components of the right scattering (scattering angles are 10 ° intervals from 10 ° to 170 °) of the forward scattering and the backscatter are shown.

As shown in FIGS. 7A and 7B, regardless of whether the cross-sectional shape of the through hole is rectangular, square, or isosceles triangle, all the angular components of the scattered light emitted from the light emitting region in various directions are regarded as parallel light. From the solvent / cell interface to the cell / air interface. Then, the focusing action of the cell / air interface focuses on the circumference centered on the central axis of the sample cell. When the outer diameter (radius) of the sample cell 17 is 4 mm, the radius of the circumference is 12.7 mm. Therefore, in the examples shown in FIGS. 7A and 7B, by arranging the photodetector 9 at a position on the circumference E having a radius of 12.7 mm and where each angle component of the scattered light is focused, each angle component can be obtained. The light intensity can be determined.

When the cross-sectional shape of the through hole is polygonal, the solvent / cell interface is composed of a plurality of planes. Depending on the angular component of the scattered light, it is incident across a plurality of planes constituting the solvent / cell interface of the through hole, and splits when passing through the planes. In the examples shown in (a) and (b) of FIG. 7A and (d) of FIG. 7B, it was confirmed that some angular components of the scattered light were split in two directions by passing through the two planes. To. In this case, for a specific angle component incident on the two planes, the intensity distribution ratio in the two planes is calculated, and only the angle component having the larger intensity distribution ratio among the two planes is used as the measurement target for photodetection. It is preferable to perform weighting correction by detecting with the device 9 and multiplying the detection result by the inverse of the intensity distribution ratio. By the above method, the scattered light intensity of the entire angle component incident on the two planes can be obtained. By using the above method, even if the cross-sectional shape of the through hole is a polygon other than the triangle and the quadrangle shown in FIG. 7, in principle, the light intensity of all the angular components of the scattered light can be obtained. it can.

However, if the number of planes on which a certain angular component of scattered light is incident increases, even if the angular component has a large intensity distribution ratio, the light intensity becomes small, so that there is a concern that the SN ratio may deteriorate. In order to reduce the number of planes in which the individual angular components of the scattered light are involved, a triangle having the smallest number of line segments constituting the polygon may be selected as the cross-sectional shape of the through hole. For example, FIG. 8 shows an angular component of scattered light passing through three plane side surfaces of a through hole having an equilateral triangular cross section. If the differential cross-sectional area (scattering intensity) of the angular component of scattered light is defined as "σ (θ)" (θ is the scattering angle), σ (0) to σ (-θ1) and σ (θ1) to σ (θ2) , And the angular components from σ (-θ1) to σ (-π) pass only through the plane side of the through hole, which corresponds to the upper left, right and lower left sides of the triangle, respectively. Since σ (-θ) = σ (θ), it is possible to measure all the angular components of scattered light while avoiding splitting.

FIG. 9 is a ray diagram of each angle component of scattered light when the solvent flowing through the through hole of the sample cell 17 having an equilateral triangular cross-sectional shape is water (refractive index = 1.333). From FIG. 9, the angle component from 0 ° to -60 ° is borne by the plane side surface corresponding to the upper left side, and the angle component from 60 ° to 90 ° is borne by the plane side surface corresponding to the right side. It is recognized that the components are not divided. Note that FIG. 9 is a ray diagram of forward scattering, and when this is inverted upside down, a ray diagram of backscattering is obtained.

<3. Angle resolution>
FIG. 10 is a light intensity distribution depending on the detection position obtained by tracing a light ray having an angular component of 90 ° in two dimensions. The horizontal axis of FIG. 10 is the detection position coordinates, and each spectrum corresponds to a different Δθ0 when the emission angle from the sample cell 17 is θ0 and θ0 is expressed by the following equation (1).
θ0 ＝ 90 ° －Δθ0 ・ ・ ・ (1)

FIG. 10 shows the peaks when three of 0 °, 0.02 °, and 0.04 ° are selected as Δθ0. As can be seen from FIG. 10, all the peaks in which Δθ0 is 0 °, 0.02 ° and 0.04 ° can be clearly discriminated. From this, the angular resolution of the photodetector 9 can be estimated to be 0.02 °. Since the angle of 0.02 ° corresponds to the length of 4 μm on the circumference with a radius of 12.7 mm, tentatively, a one-dimensional photodiode array detector with a pixel width of 4 μm is placed on the circumference E without any gap. In principle, all angular components of scattered light can be measured with an angular resolution of 0.02 ° if they can be arranged over the same.

Since the scattering component of θ0 = 90 ° has the widest luminous flux width, the influence of spherical aberration at the cell / air interface is the largest. Therefore, in the angle region other than θ0 = 90 °, the spherical aberration is smaller than the scattering component of θ0 = 90 °, and the resolution should be high. Moreover, the solvent refractive index dependence of the resolution is extremely low in any angle region.

<4. Noise component>
<4.1 Noise component generation>
FIG. 11 is a ray diagram of each angle component of scattered light when the solvent of the liquid sample flowing through the through hole of the sample cell 17 having an equilateral triangular cross-sectional shape is quinoline. The index of refraction of water (1.333) is smaller than the index of refraction of the sample cell (1.46), whereas the index of refraction of quinoline is 1.66, which is larger than the index of refraction of the sample cell (1.46).

As can be seen from the comparison with the ray diagram of FIG. 9, when the solvent of the liquid sample flowing through the through hole of the sample cell 17 is changed from water to quinoline, the focal points of two different angular components are concentrated in one place. Can be seen. In FIG. 11, the points circled by three circles indicate the points where the focal points of the two different angular components are concentrated. In this way, when the focal points of two different angular components are concentrated in one place, the light intensity of each angular component cannot be detected unless the two angular components can be separated.

The focal positions of scattered light in different directions match because the refractive index ratio (n1 / n0) of the solvent and the sample cell 17 is large, and the cross-sectional shape of the through hole is an equilateral triangle. The reason will be described with reference to FIGS. 12 to 14B. As shown in FIG. 12, for the sake of simplicity, the three plane side surfaces of the through holes constituting the solvent / cell interface are designated by the names of the sides of the equilateral triangle (right side, upper left side, lower left side), respectively. I will call it. In addition, the upper left side and the lower left side are divided into a right part and a left part, respectively, with the position where the laser beam crosses the upper left side and the lower left side as a boundary. Sometimes called a club.

Generally, the larger the refractive index ratio of two media sandwiching a flat interface, the higher the reflectance of light. Especially when light is incident from a high refractive index medium to a low refractive index medium, total reflection occurs at a certain angle of incidence. , The incident angle (critical incident angle) becomes smaller as the refractive index ratio is larger. Since the angle of incidence is defined by the angle of inclination of the incident light with respect to the normal of the interface, a smaller critical angle of incidence means closer to vertical incidence.

13A and 13B show a luminous flux that is emitted from the scattered light generation region (light emitting region) in the through hole in a certain direction and directly passes through the upper left side or the right side, and is emitted from the light emitting region in a direction different from the light flux. Then, after reflecting on any side of the equilateral triangle, the path of the luminous flux passing through the upper left side or the right side is shown. In this description, "reflection" includes reflections other than total internal reflection. The region indicated by reference numeral 101 in FIGS. 13A and 13B is a light emitting region. Further, in FIG. 13A, the laser light passes through the midpoints of the upper left side and the lower left side, and in FIG. 13B, the laser light passes closer to the right side than the midpoints of the upper left side and the lower left side. ..

In FIGS. 13A and 13B, a luminous flux (direct luminous flux 110, indicated by a solid line) that emits light from the light emitting region 101 in a certain direction on the left side and directly passes through the upper left side, and a direction on the left side different from the direct luminous flux 110. The light flux emitted from the light emitting region 101, reflected at the left portion of the lower left side, and passed through the upper left side (indirect luminous flux 120, indicated by a two-point chain line) is depicted in the same direction. Further, in FIG. 13A, a luminous flux (direct luminous flux 111, indicated by a solid line) that emits light from the light emitting region 101 in a certain direction on the right side and directly passes through the right side, and emits light in a direction on the right side different from the direct luminous flux 111. A state in which the directions of the luminous flux (indirect luminous flux 121, indicated by a broken line) emitted from the region 101, reflected at the right portion of the upper left side and passing through the right side is drawn. Further, in FIG. 13B, the directions of the light flux (indirect light flux 122, indicated by a broken line) that is emitted from the light emitting region 101 in a certain direction on the right side, is reflected on the right side and passes through the upper left side, and the above-mentioned direct light flux 110. Is drawn to be the same.

Of these luminous fluxes 110, 111, 120, 121, 122, the luminous flux to be detected is only the direct luminous flux 110, 111, and the luminous flux 110, 111 is the signal light. Since the indirect luminous fluxes 120, 121, and 122 have different scattering angles from the signal light, they become noise components. The upper left side and the right side of FIG. 13A and the upper left side of FIG. 13B show a region 310 through which signal light passes and a region 320 and 322 through which noise components pass, respectively, with thick arrows.

As can be seen from FIGS. 13A and 13B, the direct luminous flux 110 and the indirect luminous flux 120, and the direct luminous flux 111 and the indirect luminous flux 121 all have the same direction, but the regions passing through the upper left side and the right side do not overlap. That is, the signal light and the noise component pass through the upper left side or the right side without overlapping. Since the discrimination between the signal light and the noise component is maintained outside the sample cell, the noise component can be completely removed by providing an appropriate light-shielding plate or slit between the sample cell and the photodetector.

On the other hand, as shown in FIG. 13B, in the direct luminous flux 110 and the indirect luminous flux 122, the regions passing through the upper left side overlap, and spatial superposition occurs between the signal light and the noise component. The noise component that does not overlap with the signal light can be removed, but the noise component that overlaps cannot be removed.

The "degree" such as whether or not an irremovable noise component is generated and the ratio of the irremovable noise component to the light emitted from the light emitting region 101 in a certain direction is the refractive index ratio between the solvent and the sample cell and the through hole. Cross-sectional shape (equilateral triangle), the part where the laser light passes through the through hole (for example, the midpoint of the upper left and lower left sides of the equilateral triangle, the center of gravity, or the vicinity of the right side It depends on. The more the light emitting region 101 is located on the left side of the equilateral triangle, the narrower the incident angle range with respect to the right side. As an extreme example, when the excitation laser passes through the left apex of an equilateral triangle, the angle of incidence with respect to the right side is in the range of -30 ° to 30 °, assuming that the normal orientation on the right side of the light emitting region 101 is 0 °. .. On the contrary, when the laser beam passes by the right side of the equilateral triangle, the incident angle range with respect to the right side is in the range of −90 ° to 90 °. That is, since the range of the incident angle is widened as the light emitting region 101 is located to the right, the components having high reflectance increase and total reflection is likely to occur.

<4.2 Light intensity of noise component>
Next, the ratio of the noise component to all the scattered light (a certain angle component of the scattered light) emitted from the light emitting region 101 in a certain direction was quantified by converting it into light intensity. Here, the ratio converted into light intensity is referred to as "contribution rate of noise component".

The light intensity of the noise component is determined by two factors. One is the ratio of the noise light generation region to which the reference numerals 220, 221 and 222 are attached to FIGS. 13A and 13B to the light emitting region 101. Not all specific angular components of scattered light become noise components, and it is the luminous flux emitted from the noise light generation regions 220, 221 and 222 that is reflected at the sides (interfaces) of the equilateral triangle and superimposed on the signal light. Limited to.
Another factor is the reflectance at the interface of the noise component.
From the above, the value obtained by multiplying "the length of the noise light generation region / the length of the light emitting region" by the reflectance at the interface of the noise light becomes an index of the light intensity of the noise component. This index is called "normalized strength". The value obtained by multiplying the light intensity of a specific angle component by the normalized intensity is the light intensity of the noise component. Therefore, for example, when the normalized intensity is 0.4 and the total scattering intensity in the direction of the noise light is Inoise, 0.4 × Inoise of Inoise is added to the signal to be detected.

Figures 14A and 14B show the relationship between the normalized intensity of the noise component and the scattering angle. However, in FIGS. 14A and 14B, in order to facilitate understanding, the scattering angle is limitedly represented by using the angle metric shown in FIG. 15A. Conventionally, the angle metric shown in FIG. 15B has been used for the measurement of the scattering angle, but at this coordinate, the axis of symmetry of the forward scattering and the backscatter is the axis of 90 ° or -90 °, and the right side. The sign is inverted on the left. In order to avoid this, the angle measurement shown in FIG. 15A is used here.

14A and 14B correspond to the case where the laser beam penetrates the midpoint of the upper left lower side of the equilateral triangle and the case where it penetrates the center of gravity of the equilateral triangle, respectively. The horizontal axis of FIGS. 14A and 14B is the scattering angle θ0 [degree] in the solvent, and represents the direction of emission from the light emitting region 101. The vertical axis of FIGS. 14A and 14B is the normalized intensity of the noise component that follows the signal light emitted at the scattering angle θ0, and is indicated as the noise contribution rate in the figure. Since the noise contribution rate depends on the refractive index of the solvent, the refractive indexes shown in FIGS. 14A and 14B are 1.26 (fluorescent solvent), 1.333 (water), 1.492 (toluene), 1.56 (Nitrobenzene) and 1.66 (Quinoline). The noise contribution rate at the time is shown.

Further, in FIGS. 14A and 14B, the numerical values shown together with the horizontal arrows indicate the scattering angles of the noise components following the signal light of the scattering angle θ shown on the horizontal axis corresponding to the arrows as local coordinates. For example, the scattering angle of the noise component that follows the signal light with a scattering angle θ0 = 2 ° is 58 °. Further, the scattering angle of the noise component that follows the signal light with the scattering angle θ0 = 125 ° is 175 °. Furthermore, the curve representing the contribution rate of the noise component reflected on the right side is displayed with the zero point based up to 0.5 in order to avoid overlapping with other noise contribution rate curves.

From FIG. 14A, the refractive index of the solvent is 1.66, and the noise contribution rate when the scattering angle θ0 = 2 ° is about 0.89. This is because the angular component of the scattering angle θ0 = 58 ° is reflected in the right part of the upper left side (the area indicated by the red line on the equilateral triangle) with respect to the signal light with the scattering angle θ0 = 2 °, and the scattering angle θ0 = This means that the light intensity of the component that follows / mixes with the 2 ° signal light is about 89% of the light intensity of the entire angle component with a scattering angle of θ0 = 58 °.

Also, from FIG. 14B, the refractive index of the solvent is 1.66, and the noise contribution rate when the scattering angle θ0 = 118 ° is about 0.44. This is because the angular component of θ0 = 62 ° is reflected on the right side (the area indicated by the red line on the equilateral triangle) with respect to the signal light with a scattering angle of θ0 = 118 °, and the signal light with a scattering angle of θ0 = 118 °. It means that the component that follows / mixes with is about 44% of the total light intensity of the angle component having a scattering angle of θ0 = 62 °. 14A and 14B show all noise components that follow the signal light of the forward scattering component. The noise component that follows the signal light of the backscattering component has a profile in which FIGS. 14A and 14B are horizontally inverted at an angle θ0 = 180 ° and the sign of the numerical value of the local coordinates indicated by the arrow is negative.

As described above, all the noise components reflected on the upper left side and the lower left side can be discriminated from the signal light and removed. On the other hand, a part of the noise component reflected on the right side can be excluded, but the rest cannot be excluded. However, as shown in FIG. 14A, when the laser beam penetrates the midpoint of the lower left side of the equilateral triangle, the noise contribution rate of the noise component reflected on the right side is almost zero regardless of the refractive index of the solvent and is ignored. can do. On the other hand, as shown in FIG. 14B, when the laser beam penetrates the center of gravity of an equilateral triangle, the noise contribution rate increases in the angle range of 110 ° to 120 ° when the solvent has a high refractive index. Some cannot be ignored. In such a case, the photodetector 9 may not be installed in the above angle range. In addition, when the laser beam penetrates the midpoint of the lower left side of the equilateral triangle and when it penetrates the center of gravity, the noise contribution rate becomes remarkable when the solvent has a high refractive index, but when the solvent has a low refractive index. It can be seen that has a small noise contribution rate and has little effect on the detection of the light intensity of the signal light.

From the geometrical consideration, it was shown in FIGS. 13A and 13B that the noise component reflected on the upper left side and the lower left side can be removed. On the other hand, FIG. 16 is a ray diagram showing that when the solvent is quinoline (n0 = 1.66), the noise component can be removed by providing a slit at an appropriate position between the sample cell 17 and the photodetector 9. Is. In FIG. 16, the scattering angle is represented by the conventional angle measurement. The angle component with a scattering angle of 70 ° (shown in pink) has an angle component with a scattering angle of 50 ° (shown in light blue), and the angle component with a scattering angle of -50 ° (shown in purple) has a scattering angle. The -70 ° angle component (shown in green) follows as a noise component. From FIG. 16, it is clear that these noise components are completely removed by the slits, which supports the geometrical consideration.

<4.3 Factors that depend on the refractive index of the solvent>
<4.3.1 Relationship between the orientation of the photodetector and the angular component of the scattered light>
The scattering angle of the angular component reaching the photodetector 9 arranged on the circumference depends on the refractive index of the solvent. Therefore, when designing an actual optical system, the angle component to be detected is selected according to a specific refractive index. For example, the upper part of Table 1 shows the scattering angle of the angular component when the solvent is water (refractive index n0 = 1.333) and the photodetector arranged on the circumference to detect the angular component of that angle. It shows the relationship with the orientation. In Table 1, the angle component and the direction (degree) of the detection position are angles represented by the angle measurement shown in FIG. 15 (a). For reference, the scattering angle represented by the conventional customary angle measurement of FIG. 15B is shown in the upper part (conventional scattering angle) of Table 1.

From Table 1, the orientations of the photodetector 9 for detecting the angular components with scattering angles of 0 °, 20 °, 140 °, 120 ° and 100 ° are 0 °, 18.25 °, 138.25 °, 120 ° and 120 °, respectively. It becomes 101.75 °. The angle components with angles of 0 ° and 120 ° are vertically incident on the interface, so there is no refraction. Therefore, the scattering angle and the orientation of the photodetector 9 match. Since the other angular components are obliquely incident on the interface, the orientation of the photodetector 9 depends on the refractive index of the solvent. That is, the orientation of the photodetector 9 for detecting the angular component of the scattered light to be measured varies depending on the refractive index of the solvent, but there is only a slight difference and it is not a particularly big problem. Table 1 shows the orientation of the photodetector 9 for detecting the angular components having scattering angles of 0 °, 20 °, 140 °, 120 ° and 100 ° for each refractive index of the solvent.

Further, since the laser light is refracted at the interface between the sample cell 17 and the solvent, in order for the laser light to penetrate the flow path parallel to the right side, the direction of incident on the through hole is adjusted according to the refractive index of the solvent. Must. For example, when the solvent is water (refractive index n0 = 1.333), it is necessary to inject the laser beam at an angle of 27.24 ° with respect to the lower left side (the normal direction with respect to the lower left side is zero). Under this condition, the directional shift Δθin due to the refraction of the laser beam as shown in Table 2 occurs at the interface on the lower left side according to the refractive index n0 of the solvent. Decrease by shift Δθin.

<4.3.2 Ratio of luminous flux width between signal light and noise component>
The ratio of the luminous flux width of the signal light to the noise component also depends on the solvent refractive index. FIG. 17A is a diagram showing the relationship between the luminous flux width of the noise component reflected on the lower left side of the triangle and the solvent refractive index. For simplicity, FIG. 17A shows only forward-scattered signal light.
Consider the luminous flux of the signal light that travels in the sample cell 17 at the azimuth angle θ1 (emission angle with respect to the upper left side) after passing through the solvent. When the azimuth θ1 is fixed and the azimuth θ0 (incident angle with respect to the upper left side) in the solvent is considered in a back-light tracking manner, the smaller (larger) the refractive index of the solvent, the larger (smaller) the azimuth θ0. Therefore, the passing region with respect to the upper left side of the signal light becomes wider (narrower), and the luminous flux width ratio of the noise component (luminous flux width of the noise component / luminous flux width of the signal light) becomes smaller.

On the other hand, the luminous flux width ratio of the noise component reflected at the right part of the upper left side of the triangle differs depending on the direction θnoise of the scattered light that is the noise component. When θnoise = 60 °, the noise component reflected on the right part of the upper left side becomes perpendicular to the right side, but this is the boundary. As shown in FIG. 17B, when 30 ° <θnoise <60 °, the azimuth angle θ1 of the signal light on which the noise component reflected by the right part of the upper left side of the triangle is superimposed is in the range of 30 ° to 0 ° and is a positive value. have. On the other hand, as shown in FIG. 17C, when 60 ° <θnoise <90 °, the azimuth angle θ1 of the signal light on which the noise component reflected by the right part of the upper left side of the triangle is superimposed is in the range of 0 ° to -30 °. Has a negative value.

Consider the luminous flux of the signal light that travels in the sample cell 17 at the azimuth angle θ1 (emission angle with respect to the upper left side) after passing through the solvent. In either case, the larger the θnoise, the larger the luminous flux width of the noise component. When 30 ° <θnoise <60 °, the smaller the refractive index of the solvent, the smaller the θnoise, and the smaller the luminous flux width of the noise component. On the other hand, when 60 ° <θnoise <90 °, the smaller the refractive index of the solvent, the larger θnoise, which has the opposite correlation.

In this way, the luminous flux width ratio of the noise component depends on the refractive index of the solvent. Therefore, if the slit width for removing the noise component with respect to each angle component of the scattered light is designed according to the refractive index of the solvent. good. Table 1 above shows the optimum value of the slit width for removing the noise component when the refractive index of the solvent is 1.56. When the refractive index of the solvent is 1.66, the noise light cannot be completely removed by the slits having the widths shown in Table 1, but the noise component that cannot be removed is small and the influence on the detection of the signal light is small. ..

<5. Preparation of sample cell>
18A and 18B show a production example of the sample cell 17 having a triangular cross-sectional shape of the through hole. FIG. 18A is an example in which a sample cell 17 is prepared by joining two semi-cylindrical materials 171 and 172 having a groove having a V-shaped cross section. The two semi-cylindrical materials 171 and 172 can be produced by cutting a quartz cylinder in half.

FIG. 18B is an example in which a sample cell 17 is prepared by joining one semi-cylindrical material 173 having a V-shaped cross section and one semi-cylindrical material 174 having no groove. When the sample cell is produced by the method shown in FIG. 18B, there is no joint portion on each plane constituting the side surface of the through hole, and no step is generated. Therefore, the light (signal light) generated in the scattering region can be emitted into the sample cell 17 from the solvent / cell interface through a path avoiding the joint surface.

In the above, when the cross-sectional shape of the through hole is polygonal, the sample cell 17 having a regular triangular cross-sectional shape has been described. In addition to this, for example, a sample having a through hole having a cross-sectional shape as shown in FIG. A cell can be used.

Although the embodiments of the present invention have been described in detail with reference to the drawings, those skilled in the art will understand that the embodiments are specific examples of the following embodiments.

(Item 1) The light scattering detection device according to item 1 is
It is for detecting fine particles in a liquid sample.
A sample cell having a circular outer cross-sectional shape and having a flow path for holding a liquid sample,
A light source that irradiates a laser beam from a direction perpendicular to the axis of the sample cell toward the flow path,
A plurality of photodetectors arranged on a predetermined circumference outside the sample cell centered on the axis in a plane perpendicular to the axis are provided.
Of the side surfaces of the flow path, the side surface facing at least one of the plurality of photodetectors is a flat surface.

In the light scattering detection device of the first term, since the side surface of the flow path facing at least one of the plurality of detectors is a plane, this side surface (plane side surface) of the scattered light generated in the flow path. Although the angular component passing through the plane is refracted on the plane side surface, it goes toward the interface between the sample cell and the external space as parallel light while maintaining the wave plane of the plane wave. Generally, the refractive index of the sample cell is larger than the refractive index of the external space (air), and in this light scattering detection device, the external cross-sectional shape of the sample cell is circular, so that the sample cell and the external space The interface of is convergent. Therefore, the angular component of the scattered light that has passed through the plane side surface of the flow path and is directed toward the interface between the sample cell and the external space as parallel light is focused on a predetermined circumference centered on the axis of the sample cell. .. Since a plurality of photodetectors are arranged on the predetermined circumference, the light that faces the angular component of the scattered light that has passed through the plane side surface regardless of the refractive index of the solvent of the liquid sample. It can be detected by a detector.

(Item 2) In the light scattering detection device of item 1,
The laser beam emitted from the light source passes through a region of the flow path facing the plane side surface.

According to the light scattering detection device of the second term, among the scattered light generated by the laser light passing through the liquid sample, the angular component in the direction perpendicular to the axis of the sample cell (normal direction) is the plane. Can be passed through the sides.

(Item 3) In the light scattering detection device of item 1,
The cross-sectional shape of the flow path is a closed curve having at least a part of a straight line.

In the light scattering detection device of the third item, since the plane side surface of the flow path is formed in the entire axial direction of the sample cell, the degree of freedom in arranging the light source and the photodetector is widened.

(Item 4) In the light scattering detection device of item 3,
The cross-sectional shape of the flow path is polygonal.

The light scattering detection device of the fourth item facilitates the preparation of a sample cell.

(Item 5) In the light scattering detection device of item 4,
A light scattering detection device having a triangular cross-sectional shape of the flow path.

(Section 6) In the light scattering detection device of Section 4,
The cross-sectional shape of the flow path is an equilateral triangle.

In the light scattering detection devices of the fifth and sixth paragraphs, the number of plane side surfaces in which individual angular components of scattered light generated in the flow path are involved can be reduced.

1 ... Laser light source 2 ... Incoherent light source 8, 9 ... Photodetector 17 ... Sample cell 100 ... MALS detector

Claims (6)

1. A light scattering detector for detecting fine particles in a liquid sample.
   A sample cell having a circular outer cross-sectional shape and having a flow path for holding a liquid sample,
   A light source that irradiates a laser beam from a direction perpendicular to the axis of the sample cell toward the flow path,
   A plurality of photodetectors arranged on a predetermined circumference outside the sample cell centered on the axis in a plane perpendicular to the axis are provided.
   A light scattering detection device in which a side surface of the flow path facing at least one of the plurality of photodetectors is a flat surface.
2. In the light scattering detection device according to claim 1,
   A light scattering detection device in which a laser beam emitted from the light source passes through a region of the flow path facing the side surface, which is a plane.
3. In the light scattering detection device according to claim 1,
   A light scattering detection device in which the cross-sectional shape of the flow path is a closed curve having at least a part of a straight line.
4. In the light scattering detection device according to claim 3,
   A light scattering detection device having a polygonal cross-sectional shape of the flow path.
5. In the light scattering detection device according to claim 4,
   A light scattering detection device having a triangular cross-sectional shape of the flow path.
6. In the light scattering detection device according to claim 4,
   A light scattering detection device in which the cross-sectional shape of the flow path is an equilateral triangle.

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