JP5854621B2 - Long optical path length flow cell - Google Patents

Description

  The present invention relates to a flow cell for spectroscopic analysis of a sample, and more particularly to a flow cell for spectroscopic analysis used in a liquid analyzer.

  A device for spectroscopic analysis of samples with ultraviolet, visible, or infrared light, which is provided in a liquid analyzer such as a liquid chromatograph, is equipped with a flow cell, and the emission intensity represented by absorbance or fluorescence using the flow cell. Etc. are measured. In general, the longer the optical path length in the flow cell, the higher the analytical sensitivity. However, in a flow cell having a long optical path length, the position distribution of the sample is often expanded in the flow cell due to a hydrodynamic effect, so that the peak signal value obtained is smaller than the peak signal value that should be originally obtained, resulting in a decrease in sensitivity. . In the case of the purpose of separating and analyzing a plurality of sample components coexisting in a solution like a liquid chromatograph apparatus, the spread of the position distribution of the sample not only lowers the sensitivity but also lowers the resolution at the same time.

  A flow cell having a cylindrical flow path is often used because of its ease of processing and its theoretical handling. Its typical structure is as shown in FIGS. FIG. 1 is a schematic perspective view of a flow cell having a cylindrical flow path, and FIG. 2 is a cross-sectional view of a cross section 1009 passing through the center of the optical path in FIG. The flow cell body 1001 is provided with window materials 1002 and 1003, and the sample solution introduced from the fluid introduction unit 1005 passes through the cylindrical channel 1004 and is discharged from the fluid discharge unit 1006. Measuring light 1008 is incident on the cylindrical channel 1004 from a light source, and light absorption and light emission occur. In the flow cell 1000 having this cylindrical flow path, attempts have been made to reduce the flow path diameter in order to reduce the spread of the sample position distribution. However, the reduction in the diameter of the flow path not only leads to an increase in the amount of measurement light that is generally shielded from the incident surface of the flow cell, but the inner wall of the flow path in a cylindrical flow path having a long optical path length as shown in FIG. This leads to an increase in the amount of measurement light falling on the screen, resulting in a problem that the obtained signal value decreases or noise increases and sensitivity decreases. In particular, when the absorbance method is used as a principle, the measurement light striking the inner wall of the flow path often becomes disordered light reflection, light scattering, or light absorption, which often increases noise (Non-patent Document 1). That is, the refractive index fluctuation of the solution caused by external factors such as temperature fluctuation, pressure fluctuation, solution composition fluctuation, etc. fluctuates the ratio of these reflected light and scattered light to incident light, and apparent absorbance fluctuation, that is, noise Or the problem of being detected as drift is known. In particular, this effect is called a liquid lens effect because it is caused by a change in the refractive index of the solution inside the flow path (Non-patent Document 2). Therefore, in the cylindrical flow path, there is a trade-off relationship between the reduction in the spread of the position distribution of the sample and the improvement in sensitivity.

  In order to solve this problem, two types of methods have been devised. One is to reduce the amount of light that hits the inner wall of the flow channel by changing the flow channel structure, and the other is a method that totally reflects the measurement light on the inner wall of the flow channel by material contrivance. This is an attempt. As an example of the former, as shown in FIG. 3, it has been devised to use a frustoconical channel 1007 that is tapered from the entrance surface to the exit surface instead of the cylindrical channel ( Patent Document 1). As an example of the latter, it has been devised to use a glass capillary as a flow cell material and use a solvent having a higher refractive index than glass (Patent Document 2). In Patent Document 3, a fluorine-based polymer, particularly Teflon (registered trademark) AF, which is a material having a lower refractive index than water, which is a solvent having the highest refractive index among frequently used in spectroscopic analysis, is flown. A system has been devised that achieves total reflection of light by applying to the inner walls of the road. Further, in Patent Document 4, a double fused silica capillary is used for the flow cell, a measuring solvent is used for the inner capillary, and a solvent having a lower refractive index than that, particularly a perfluoro solvent, is used for the outer capillary. A system has been devised in which light is totally reflected by the arrangement.

U.S. Pat. No. 4,011,451 Japanese Patent No. 1662013 US Pat. No. 5,184,192 US Patent Publication No. 2009/0230028

J. Chromatogr. 465,227 (1989) J. Chromatogr. 503, 127 (1990)

  The flow path expanded in a taper shape increases the flow cell capacity and the sample expands more than the cylindrical flow path, so the time that the sample stays in the flow path increases and the spread of the position distribution of the sample increases. End up. On the other hand, in an attempt to improve the signal-to-noise ratio by totally reflecting the measurement light in the flow channel by material contrivance, the amount of light decreases when the measurement flow channel is not fully reflected due to foreign matter adhesion etc. And sensitivity will fall.

  The present invention provides a flow cell that can improve the sensitivity while reducing the spread of the position distribution of the sample by devising the channel structure.

  A flow cell of a representative form of the present invention includes a main body having a sample flow path through which measurement light passes, and window materials provided on the light incident side and the light output side of the main body, and the sample flow path is a fluid. It has the 1st cylindrical flow path connected to the introduction part, and the 2nd cylindrical flow path connected to the fluid discharge part. The first cylindrical channel and the second cylindrical channel have a shape in which a cross-sectional area perpendicular to the incident optical axis is constant or continuously increases along the traveling direction of the incident light. The cross-sectional area perpendicular to the incident optical axis at the light exit end of the cylindrical flow path is equal to or smaller than the cross-sectional area perpendicular to the incident optical axis at the light incident end of the second cylindrical flow path.

  Preferably, the flow passage cross-sectional area of the fluid discharge portion is larger than the flow passage cross-sectional area of the fluid introduction portion. The main body is made of a material that prevents reflection of light in the ultraviolet to infrared wavelength range, or the inner wall surfaces of the first and second channels prevent reflection of light in the ultraviolet to infrared wavelength range. It is preferably modified with a material having properties.

  In the liquid analyzer incorporating the flow cell of the present invention, it is desirable that the focal position of the incident light from the light source is located on the light source side with respect to the fluid discharge side of the first cylindrical channel.

By configuring the sample channel through which the measurement light passes by connecting two cylindrical channels, the amount of measurement light hitting the inner wall of the sample channel can be reduced and the sensitivity can be improved. In addition, the effect of rectifying the fluid is obtained by the first cylindrical channel, and the spread of the position distribution of the sample can be reduced because the sample flows quickly.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

Schematic which shows an example of the flow cell which has a cylindrical flow path. Sectional drawing which shows the mode of the light which permeate | transmits the inside of the flow cell which has a cylindrical flow path. Sectional drawing which shows the mode of the light which permeate | transmits the inside of the flow cell which has a truncated cone shaped flow path. Schematic which shows an example of the flow cell by this invention. Sectional drawing which shows an example of the flow cell by this invention. Sectional drawing which shows the mode of the transmitted light in the flow cell by this invention. Explanatory drawing which shows the mode of a time-dependent change of the flow in the flow cell by this invention. Sectional drawing which shows an example of the flow cell by this invention. Sectional drawing which shows an example of the flow cell by this invention. Sectional drawing which shows an example of the flow cell by this invention. Sectional drawing which shows an example of the flow cell by this invention. Sectional drawing which shows an example of the flow cell by this invention. Sectional drawing which shows an example of the flow cell which has a flow path with an elliptical cross section. Sectional drawing which shows an example of the flow cell which has a polygonal cross section. Sectional drawing which shows an example of the flow cell by this invention. Sectional drawing which shows an example of the flow cell by this invention. Sectional drawing which shows an example of the flow cell by this invention. Sectional drawing which shows an example of the flow cell by this invention. Sectional drawing which shows an example of the flow cell by this invention. Sectional drawing which shows the other example of a fluid discharge part. Sectional drawing which shows the other example of a fluid discharge part. Sectional drawing which shows the other example of a fluid discharge part. Schematic which shows an example of a liquid chromatography apparatus. Schematic which shows an example of a spectrophotometer. Schematic which shows an example of a spectrophotometer. The figure which shows a band expansion measurement result. The figure which shows a noise measurement result.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 4 is a schematic diagram of one embodiment of a flow cell according to the present invention. The flow cell 100 includes a flow cell body 101 and window materials 102 and 103 that transmit two pieces of light. Inside the flow cell body 101, the first cylindrical flow path 104 on the measurement light incident side, the second cylindrical flow path 105 on the measurement light emission side, the fluid introduction part 106 for introducing fluid into the flow cell 100, and the fluid are discharged A fluid discharge portion 107 is provided. As will be described later, when the flow cell 100 is incorporated into the liquid analyzer, the light source is disposed on the first cylindrical flow path 104 side, and the detector is disposed on the second cylindrical flow path 105 side. Measurement light enters from the channel 104. The measurement light that has passed through the first cylindrical channel 104 and the second cylindrical channel 105 is detected by a detector. The sample solution is introduced from the fluid introduction unit 106, and is discharged from the fluid discharge unit 107 through the first cylindrical channel 104 and the second cylindrical channel 105.

  The window members 102 and 103 may be optical parts that transmit light, and may be optical parts such as quartz glass and lenses. The flow cell body 101 may be any material that prevents reflection of light in the ultraviolet to infrared wavelength region. For example, black quartz is desirable, and a resin such as glass fiber reinforced polycarbonate mixed with carbon or a material such as carbon fiber may be used. In addition, the inner walls of the first cylindrical channel 104 and the second cylindrical channel 105 are modified by a method such as coating, plating, or vapor deposition with a material that prevents reflection of light in the ultraviolet to infrared wavelength region. May be. In that case, the flow cell body 101 may be a metal such as stainless steel or aluminum steel, a silicon oxide such as fused silica or quartz glass, or a resin such as polycarbonate. A material such as black quartz, zinc oxide, aluminum oxide, diamond-like carbon may be used.

  The outer shape of the flow cell shown in FIG. 4 has a shape obtained by cutting a part of a cylindrical shape for the convenience of installing a pipe for flowing a solution, but an important point is a cylindrical path through which fluid and measurement light pass. Therefore, it is not always necessary to have such a shape, for example, a simple cylindrical shape, a truncated cone shape, a rectangular tubular shape, a truncated cone shape, or a place where the flow cell should be placed based on these shapes. The shape processed in this way may be used. As a method of forming the flow cell body 101, a method of opening pores by drilling, a groove is formed in the cell body surface that has been divided in half in advance, and the surface is sufficiently polished by a chemical polishing method or the like, followed by optical bonding. There is a way to assemble the body. As a method for forming the entire flow cell, there are a method of mechanically pressing and a method of welding with heat.

  FIG. 5 is a cross-sectional view of the flow cell cut along a plane 408 passing through the flow path center of FIG. Two window members 102 and 103 are provided on both sides of the flow cell body 101, and a first cylindrical channel 104, a second cylindrical channel 105, and a first cylinder through which measurement light passes are provided inside the body. A fluid introduction part 106 for introducing a sample to the light incident end side of the cylindrical flow path 104 and a fluid discharge part 107 for discharging the sample from the light emission end side of the second cylindrical flow path are provided. In the present embodiment, the first cylindrical channel 104 has a cylindrical shape, and the second cylindrical channel 105 has a truncated cone shape whose cross-sectional area increases along the traveling direction of the measurement light emitted from the light source. It has the shape of The cross-sectional area of the light incident end of the second frustoconical channel 105 is equal to the cross-sectional area of the light exit end of the first cylindrical channel 104, and the focal position of light from the light source is the first cylindrical channel. 104 outside.

  More specifically, the diameter of the cylindrical flow path 104 is 0.3 mm or more and 1 mm or less, the total optical path length of the flow cell is 5 mm or more and 50 mm or less, and the cone angle of the truncated cone-shaped flow path 105 is 1 degree or more and 30 degrees. Hereinafter, the flow path diameters of the fluid introduction part 106 and the fluid discharge part 107 are the same and are preferably 0.2 mm or more and 0.5 mm or less. With this shape, as shown in FIG. 6, not only can the sensitivity be improved by reducing the amount of measurement light 608 that strikes the inner wall of the flow path, but also the spread of the sample position can be reduced by the rectification effect. Become. By selecting the material of the cell body or the material of the first and second flow path inner walls, even if a minute amount of measurement light is randomly reflected or scattered on the first or second flow path inner walls, the reflection / scattering Light is reduced by the material that prevents reflection of light in the ultraviolet to infrared wavelength region, which is adopted as a material for the entire flow cell or a modification material for the inner walls of the first and second channels, and can further improve sensitivity. . In FIG. 7, the conceptual diagram of the time-dependent change of a flow was shown. As shown in FIG. 7, the flow is adjusted by the first cylindrical flow path 104 acting as a fluid running section, and the sample does not expand in the second cylindrical flow path 105, so that the sample is quickly expanded. Since the residence time in the channel is reduced by flowing in the channel, it is possible to reduce the spread of the position distribution of the sample in the channel.

  FIGS. 8 to 12 show other embodiments of flow cells having various flow channel shapes in cross-sectional views at the same positions as in FIG. In each embodiment, the flow path diameters of the fluid introduction part 106 and the fluid discharge part 107 are preferably 0.2 mm or more and 0.5 mm or less.

  The embodiment shown in FIG. 8 includes two window members 102 and 103 on both sides of the flow cell body 101, and a first cylindrical channel 104 and a second truncated cone shape through which measurement light passes inside the body. A flow path 105, a fluid introduction part 106, and a fluid discharge part 107 are provided. In the embodiment shown in FIG. 8, the second cylindrical channel 105 has a truncated cone shape equivalent to that of FIG. 5, and the cross-sectional area of the light incident end thereof is the first cylindrical channel. This is an example that is larger than the cross-sectional area of the light emitting end. More specifically, the diameter of the cylindrical flow path 104 is 0.3 mm or more and 1 mm or less, the total optical path length of the flow cell is 5 mm or more and 50 mm or less, and the cone angle of the truncated cone-shaped flow path 105 is 1 degree or more and 30 degrees. The following is preferred.

  FIG. 9 shows an embodiment in which the second cylindrical channel 105 is a cylindrical channel having a cross-sectional area larger than that of the first cylindrical channel 104. More specifically, the diameter of the first cylindrical channel 104 is 0.3 mm or more and 1 mm or less, the diameter of the second cylindrical channel 105 is 0.4 mm or more and 10 mm or less, and the total optical path length of the flow cell is 5 mm or more and 50 mm or less are preferable.

  FIG. 10 shows a connection portion between the second cylindrical channel 105 and the first cylindrical channel 104 based on the cylindrical channel having a cross-sectional area larger than that of the first cylindrical channel 104. An embodiment is shown in which the cross-sectional area changes so as to continuously expand in the vicinity. More specifically, the diameter of the first cylindrical channel 104 is 0.3 mm or more and 1 mm or less, the diameter of the second cylindrical channel 105 is 0.4 mm or more and 10 mm or less, and the total optical path length of the flow cell is 5 mm or more and 50 mm or less, the length of the portion where the cross-sectional area of the second cylindrical flow path 105 continuously changes in the vicinity of the connecting portion with the first cylindrical flow path 104 is the first and second It is about 5-30% of the sum of the length of a cylindrical flow path.

  FIG. 11 shows an embodiment in which the cross-sectional area of the second cylindrical flow path 105 is changed so as to continuously expand along the streamline of the flow field inside the flow path. More specifically, the diameter of the first cylindrical flow path 104 is 0.3 mm or more and 1 mm or less, and the diameter of the light emitting end of the second cylindrical flow path 104 is 0.4 mm or more and 10 mm or less. The total optical path length is preferably 5 mm or more and 50 mm or less. In the present embodiment, as the shape of the second cylindrical flow path 105, a flow path in which the cross-sectional area of the entire flow path is continuously changing along the flow line of the flow field inside the flow path is taken as an example. The shape may be a parabolic shape or a hyperbolic shape, and a shape in which the cross-sectional area increases from the fluid introduction side to the fluid discharge side is desirable.

  By forming the flow channel shape as shown in FIG. 8 to FIG. 11, the measurement light quantity hitting the inner wall of the flow channel is reduced and the sensitivity is improved as in the case of FIG. And the spread of the position distribution of the sample inside the flow path can be reduced. The above-described cylindrical flow path has a rotationally symmetric shape with the central axis of the flow path as a rotation axis, but it does not necessarily have a rotationally symmetric shape, and an asymmetrical shape, for example, an asymmetric frustoconical flow It may be a road. In the examples given so far, the two flow paths having different shapes have been called the first cylindrical flow path and the second cylindrical flow path. The boundary of the cylindrical flow path can be defined as a position where the area of the cross section perpendicular to the incident optical axis or the increase rate of the area changes. For example, the boundary between two flow paths is defined at the position where the area changes, in the flow cell of the embodiment shown in FIGS. 8 and 9, and the boundary between the two flow paths at the position where the area increase rate changes. Is defined in the flow cell of the embodiment shown in FIGS. 5, 10, and 11.

  The above is an embodiment in which the first cylindrical channel is limited to a cylindrical channel having a constant cross-sectional area, but the first cylindrical channel may not have a constant cross-sectional area. For example, as shown in FIG. 12, the same effect can be obtained even if both the first cylindrical channel 104 and the second cylindrical channel 105 are frustoconical channels. In this case, the cross-sectional area of the light exit end of the first cylindrical channel 104 is the second cylindrical channel 105 in order to prevent the measurement light from hitting the inner wall of the channel while having the function of adjusting the flow. The first cylindrical flow path 104 is a cylindrical flow path whose cross-sectional area slightly increases from the fluid introduction side to the fluid discharge side, and the second cylindrical flow The channel 105 is preferably a cylindrical channel whose cross-sectional area increases from the fluid introduction side toward the fluid discharge side.

  As described with reference to FIGS. 5 to 12, there can be various shapes of flow channel structures that can achieve both reduction in the distribution of the position distribution of the sample and improvement in sensitivity, but the distribution of the position distribution of the sample due to the hydrodynamic effect can be increased. Considering the above, it is desirable that the first cylindrical channel is a cylindrical channel, and the second cylindrical channel is a truncated cone-shaped channel or a shape along the flow line of the flow field inside the channel.

  The cross section of the flow path perpendicular to the light traveling direction does not need to be circular, and the same effect can be obtained with an elliptical shape or a polygonal shape as shown in FIGS. 13A and 13B. 13A and 13B are schematic sectional views of the flow cell as viewed from the window member 102 side. In particular, when an elliptical channel cross section is used, when a light source such as a halogen lamp having an elliptical light spot is used, the amount of measurement light that strikes the inner wall of the channel can be reduced. In addition, the sensitivity can be further improved by adjusting the optical system of the liquid analyzer or changing the arrangement of the flow cell. That is, if the focal position of the measurement light from the light source is arranged closer to the light source than the fluid discharge side of the first cylindrical channel, the inner wall of the first cylindrical channel or the second cylindrical channel The measurement light hitting the inner wall can be reduced. FIG. 6 shows an example in which the focus position of the measurement light is arranged outside the flow cell. However, the focus position of the measurement light is inside the flow cell, that is, inside the first cylindrical channel 104 as shown in FIG. It may be arranged. At this time, the ratio of the optical path length of the first cylindrical channel 104 and the optical path length of the second cylindrical channel 105 to the total optical path length of the flow cell is limited by the focal position of the measurement light. It is desirable to optimize in view of the position expansion of the internal sample.

  It should be noted that the measurement light from the light source is preferably as narrow as possible and has a smaller incident angle. In order to further improve the sensitivity according to the present invention, a material that absorbs ultraviolet, visible, and infrared light is used for the flow cell body in order to prevent random scattering and absorption of the measurement light on the inner wall of the flow path. Is desirable. A cylindrical flow path is often used as the shape of the fluid introduction part and the fluid discharge part, and a Z shape (a shape that enters obliquely with respect to the optical path) or a crank shape is often used together with the optical path portion. . The above is an example in which the fluid introduction part, the fluid discharge part, and the flow path exist on the same plane, but the angle formed by the plane where the flow path / fluid introduction part exists and the plane where the flow path / fluid discharge part exists is defined. You may each arrange | position so that arbitrary angles may be formed.

  Moreover, in addition to the above-described problems when the optical path length is further increased, there is a concern that the absolute light quantity may be insufficient. To overcome this, the flow path of the entire flow cell is separated from three or more cylindrical flow paths. It may be configured. FIG. 15 shows an embodiment of a flow cell in which a third cylindrical channel is newly added to the first and second cylindrical channels on the light source side. Two window members 102 and 103 are provided on both sides of the flow cell body 101, and a truncated cone-shaped channel 108, which is a third channel through which measurement light passes, and a first cylindrical channel are provided inside the body. A cylindrical channel 104 and a truncated cone channel 105 which is a second cylindrical channel are continuously formed. A fluid introduction part 106 is connected to the light incident end of the third flow path 108, and a fluid discharge part 107 is connected to the light emission end of the second cylindrical flow path 105. This channel structure has a structure in which a truncated cone channel whose sectional area continuously decreases with respect to the traveling direction of the measurement light is newly added to the light source side of the channel structure shown in FIG. More specifically, the diameter of the cylindrical channel 104 is 0.3 mm or more and 1 mm or less, the total optical path length of the flow cell is 10 mm or more and 60 mm or less, and the cone angle of the frustoconical channels 105 and 108 is 1 degree or more. The flow path diameter of the fluid introduction part 106 and the fluid discharge part 107 is preferably 0.2 mm or more and 0.5 mm or less at 30 degrees or less. At this time, it is desirable that the focus position of the measurement light from the light source is arranged on the fluid introduction side rather than the fluid discharge side of the first cylindrical channel 104 as shown in FIG.

  With this configuration, even in a flow cell having a longer optical path length, it is possible to achieve both a reduction in the spread of the position distribution of the sample and an improvement in sensitivity by securing the same effect and absolute light quantity as those of the flow cell described in FIGS. it can. In addition, when the flow path through which the measurement light of the entire flow cell passes is composed of three or more cylindrical flow paths, in order to maximize the effects of the present invention, Starting from the site with the smallest cross-sectional area, the flow path on the fluid discharge side of the site has a shape in which the cross-sectional area continuously increases in the direction of travel of the measurement light. The flow path on the introduction side has a shape in which the cross-sectional area continuously decreases with respect to the traveling direction of the measurement light, and the focal position of the measurement light has the smallest cross-sectional area among the flow paths of the entire flow cell. It is desirable that the fluid is disposed on the fluid introduction side rather than the fluid discharge side of the part.

  Even with the channel structure described so far, it is possible to reduce the spread of the position distribution of the sample and improve the sensitivity as compared with the conventional tapered channel structure. However, in the structure already described, although the second cylindrical flow path 105 is expanded, the flow path diameter of the fluid discharge portion 107 remains narrow, so that it is difficult for the sample to flow in the vicinity of the fluid discharge portion 107. . Therefore, in order to further reduce the spread of the position distribution of the sample, it is desirable to increase the replacement efficiency of the fluid by devising the structure of the fluid discharge portion. FIG. 16 to FIG. 21 show an embodiment of a flow cell having various fluid discharge portions that enable such an effect, by a cross-sectional view at the same position as FIG.

  FIG. 16 shows an embodiment of a flow cell that has a flow path having the same shape as that of FIG. By increasing the cross-sectional area of the fluid discharge portion 107 in this way, it is possible to expedite replacement of the sample remaining in the flow path. Considering the law of conservation of mass, the ratio of the flow passage cross-sectional area of the fluid discharge portion 107 to the flow passage cross-sectional area of the fluid introduction portion 106 is the second cylinder with respect to the minimum cross-sectional area of the first cylindrical flow passage 104. It is desirable that the ratio is equal to or greater than the ratio of the maximum cross-sectional area of the channel 105. More specifically, the diameter of the cylindrical flow path 104 is 0.3 mm or more and 1 mm or less, the total optical path length of the flow cell is 5 mm or more and 50 mm or less, and the cone angle of the truncated cone-shaped flow path 105 is 1 degree or more and 30 degrees. Hereinafter, the flow path diameter of the fluid introduction part 106 is preferably 0.2 mm or more and 0.5 mm or less, and the flow path diameter of the fluid discharge part 107 is preferably 0.2 mm or more and 3.0 mm or less. The cross section of the fluid discharge unit 107 may be circular, elliptical, or polygonal. As shown in FIG. 17, this effect can also be obtained by expanding the cross-sectional area of only a part of the channel on the side connected to the second cylindrical channel 105 in the fluid discharge unit 107. In this way, the cross-sectional area is expanded only to a part of the flow path of the fluid discharge section, so that connection of piping and the like are facilitated.

  Moreover, this effect is achieved by providing not only one fluid discharge part but two or more. In other words, the total cross-sectional area of the plurality of fluid discharge portions may be larger than the cross-sectional area of the fluid introduction portion. In that case, in order to maximize the replacement efficiency of the fluid, it is desirable to arrange a plurality of fluid discharge portions having the same flow path diameter at symmetrical positions in a cross section perpendicular to the traveling direction of the measurement light. .

  FIG. 18 shows an embodiment of a flow cell having a flow path of the same shape as in FIG. 5 and having two fluid discharge portions, and shows a cross-sectional view at the same position as in FIG. FIG. 19 shows a view of the flow cell of this embodiment viewed from the window member 103 side, and the two fluid discharge portions 107a and 107b are arranged at positions symmetrical with respect to the axis of the flow path. FIG. 20 shows an embodiment of a flow cell having three fluid discharge portions 107a to 107c which have a flow channel having the same shape as that of FIG. 5 and are arranged at symmetrical positions with respect to the axis of the flow channel. It is the figure which showed the Example of the flow cell by which the fluid discharge parts 107a-107d are arrange | positioned in the mutually symmetrical position with respect to the axis | shaft of a flow path, and looked at the flow cell from the same direction as FIG. 18 to 21, specifically, the diameter of the cylindrical channel 104 is 0.3 mm or more and 1 mm or less, the total optical path length of the flow cell is 5 mm or more and 50 mm or less, and the cone angle of the frustoconical channel 105 is 1. The flow path diameter of the fluid introduction part 106 and each fluid discharge part 107 is preferably 0.2 mm or more and 3.0 mm or less.

  The above-described structure for increasing the fluid replacement efficiency is based on the flow channel structure shown in FIG. 5, but is based on the flow channel structure shown in FIGS. 8 to 12, 14, and 15. However, the same effect can be obtained. Further, the same effect can be obtained even if the cross-sectional area of the fluid discharge portion is made larger than the cross-sectional area of the fluid introduction portion based on the cylindrical flow passage or the flow passage having the whole flow passage tapered. Although the effects of the present invention can be exhibited even when combined with various flow channel structures in this way, in order to make the most of the effects of the present invention, the flow channel structure of FIG. 5 or FIG. 11 is used. It is desirable to make it.

  The flow cell according to the present invention is incorporated in a liquid analyzer represented by flow injection analysis, liquid chromatography, or the like, and is used for spectroscopic analysis of a sample by light absorption or light emission. FIG. 22 to FIG. 24 are explanatory diagrams when the flow cell according to the present invention is incorporated in a liquid analyzer. FIG. 22 shows a flow path system of the liquid chromatograph apparatus. The eluent is sent from the eluent tank 2201 by the pump 2202 and supplied to the separation column 2204 through the sample introduction unit 2203. A sample containing a test component is introduced from an injector 2205, separated by a separation column 2204, passed through a spectrophotometer 2206, and discharged into a waste liquid tank 2207. The spectrophotometer 2206 is connected to the control unit 2208. As the control unit 2208, for example, a personal computer (PC) as shown in FIG. 22 can be used. The PC includes a data display device 2209 and a data processing device 2210. The data processing device 2210 includes, for example, an arithmetic device 2211, a temporary storage device 2212, and a nonvolatile storage device 2213.

  FIG. 23 shows an optical system capable of single wavelength detection of the spectrophotometer 2206 in FIG. The flow cell 100 has the structure shown in FIG. 17, and has a light incident window 102 at one end of the flow cell body 101 and a light exit window 103 at the other end. The light from the light source 2301 passes through the condensing mirror 2302, and then is dispersed by the diffraction grating 2303, and a specific monochromatic light is irradiated to the first cylindrical flow path 104 in the flow cell 100 fixed by the jig 2304. . The solution containing the separated sample eluted from the separation column 2204 is supplied from the fluid introduction unit 106 to the flow cell 100, passes through the first cylindrical channel 104 and the second cylindrical channel 105, and then the fluid discharge unit. 107 is discharged. The light transmitted through the first cylindrical channel 104 and the second cylindrical channel 105 is received by the photodetector 2306, and the received light signal is converted into absorbance by the detection circuit 2307 connected to the control unit 2308. The As the light source 2301, an arbitrary light source that can provide light in an appropriate band including a deuterium lamp or a halogen lamp is used. As the photodetector 2306, a photodetector capable of detecting single wavelength light such as a silicon photodiode is used. In order to enhance the effect of the present invention, the optical system was adjusted so that the focus position of the measurement light emitted from the light source was set on the fluid introduction side rather than the fluid discharge side of the first cylindrical channel 104.

  FIG. 24 is a schematic diagram showing an optical system capable of multi-wavelength detection, which is an example of a liquid analyzer having another form of spectrophotometer. The flow cell 100 has the same configuration as that shown in FIG. 17, and has a light entrance window 102 at one end of the flow cell body 101 and a light exit window 103 at the other end. The light from the light source 2401 passes through the condensing mirror 2402 and then irradiates the first cylindrical flow path 104 in the flow cell 100 fixed by the jig 2403. The solution containing the separated sample eluted from the separation column 2204 is supplied to the flow cell 100 from the fluid introduction unit 106, passes through the first cylindrical channel 104 and the second cylindrical channel 105, and then the fluid discharge unit. 107 is discharged. The light transmitted through the first cylindrical flow path 104 and the second cylindrical flow path 105 passes through the condenser mirror 2405 and then is received by the photodetector 2407 via the diffraction grating 2406. It is converted into absorbance by a detection circuit 2408 connected to the control unit 2409. As the light source 2401, an arbitrary light source that can provide light in an appropriate band including a deuterium lamp or a halogen lamp is used. As the photodetector 2407, a photodetector capable of detecting multiple wavelengths such as a photodiode array is used. In order to enhance the effect of the present invention, the optical system was adjusted, and the focal position of the measurement light emitted from the light source was arranged on the fluid introduction side rather than the fluid discharge side of the first cylindrical channel 104.

  As an index of the position spread of a sample in liquid chromatography, band broadening (or called peak broadening or the like) which is a peak width on a chromatogram is known. The smaller the band broadening value, the lower the degree of overlapping of multiple peaks, and the higher the resolution in liquid chromatography. FIG. 25 shows experimental results comparing the band expansion of the flow cell based on the present invention and the flow cell having the conventional frustoconical channel structure. As the flow cell according to the present invention, the flow cell shown in FIGS. 5 and 17 was used. Further, as a comparative example, the flow cell having the conventional truncated cone cylindrical structure shown in FIG. 3 designed so that the optical path length and noise, that is, the sensitivity is the same as the flow cell shown in FIGS. 5 and 17 was used. . That is, in the flow cell of the comparative example, the diameter of the light incident end of the frustoconical channel 1007 shown in FIG. 3 is the same as the diameter of the light incident end of the first cylindrical channel 104 shown in FIGS. The diameter of the light exit end is the same as the diameter of the light exit end of the second frustoconical channel 105 shown in FIGS.

  Using the liquid chromatograph apparatus shown in FIG. 22 having the spectrophotometer shown in FIG. 24, the eluent is methanol, the flow rate is 1 mL / min, the measurement wavelength is 250 nm, and a benzene 0.01% methanol solution is added to the sample. Using, the band expansion of each flow cell was measured. The band spread of each flow cell was expressed as a relative value, assuming that the band spread at the flow rate of the flow cell of the comparative example was 0.5 mL / min. As is clear from FIG. 25, the band expansion of the flow cell of the embodiment shown in FIG. 5 is smaller than that of the comparative flow cell having a frustoconical channel structure designed to have the same sensitivity. It was. Therefore, the conventional cylindrical flow path is changed to a flow path structure including a first cylindrical flow path and a second cylindrical flow path, and the second cylindrical flow path is perpendicular to the incident optical axis. The cross-sectional area is constant or increases continuously in the traveling direction of incident light, and the cross-sectional area perpendicular to the incident optical axis at the light exit end of the first cylindrical flow path is the second cylindrical flow By setting the cross-sectional area to be equal to or smaller than the incident optical axis at the light incident end of the path, it is possible to reduce the band spread while maintaining the sensitivity. Further, when the flow cells shown in FIGS. 8 to 12, 14 and 15 were used instead of the flow cell shown in FIG. 5, it was confirmed that the same effect was obtained.

  Further, from FIG. 25, in addition to the flow channel structure of FIG. 5 as shown in FIG. 17, if a flow cell having a fluid discharge section with a large cross-sectional area is used, the time for the sample to stay in the flow channel is reduced, and the band is expanded. It was found that can be further reduced. Further, instead of the flow cell shown in FIG. 17, the flow cell shown in FIG. 16 and the flow cell having a plurality of fluid discharge portions shown in FIGS. As a result, it was confirmed that the same effect as the flow cell shown in FIG. 17 was obtained.

  FIG. 26 shows the experimental results of noise comparison between the flow cell according to the present invention and the flow cell having the cylindrical flow path structure of the comparative example. The flow cell shown in FIG. 17 was used as the flow cell according to the present invention. Further, as a comparative example, a flow cell having the conventional cylindrical flow channel shown in FIG. 2 designed so that the optical path length and the band spread are the same was used. That is, a flow cell in which the diameter of the cylindrical channel 1004 shown in FIG. 2 is the same as the diameter of the light incident end of the first cylindrical channel 104 shown in FIG. 17 was used. Using the liquid chromatography apparatus shown in FIG. 22 having the spectrophotometer shown in FIG. 24, the eluent was methanol, and noise at a wavelength of 250 nm at a flow rate of 1 mL / min was examined using each flow cell.

  As is clear from FIG. 26, the flow cell according to the present invention has a reduced noise due to a reduction in the amount of light that hits the inner wall of the flow channel, compared with the flow cell having the cylindrical flow channel structure of the comparative example. Moreover, it experimented on the same conditions using the flow cell by this invention shown in FIG.5, FIG.8-12, FIG.14-16, and FIG.18-21 instead of the flow cell shown in FIG. However, the same effect was confirmed. Therefore, it has been confirmed by experiments that the use of the flow path structure shown in the present invention can achieve both reduction in the position expansion of the sample and improvement in sensitivity.

  The results shown in FIGS. 25 and 26 are similar to those obtained when the experiment was performed under the same conditions using the liquid chromatography apparatus shown in FIG. 22 having the spectrophotometer shown in FIG. It was confirmed that it was obtained.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 100 Flow cell 101 Flow cell body 102,103 Window material 104 1st cylindrical flow path 105 2nd cylindrical flow path 106 Fluid introduction part 107 Fluid discharge part 108 3rd flow path

Claims (10)

A main body having a sample channel through which measurement light passes, and a window material provided on the light incident side and the light emission side of the main body,
The sample channel has a first cylindrical channel connected to the fluid introduction part and a second cylindrical channel connected to the fluid discharge part,
The first cylindrical flow path is a cylindrical flow path having a constant cross-sectional area perpendicular to the incident optical axis, and the second cylindrical flow path has a cross-sectional area perpendicular to the incident optical axis in the traveling direction of the incident light. The cross-sectional area perpendicular to the incident optical axis at the light exit end of the first cylindrical channel is a frustoconical channel that continuously increases along the second cylindrical channel. A flow cell having a cross-sectional area perpendicular to an incident optical axis at a light incident end.   2. The flow cell according to claim 1, wherein the main body is made of a material that prevents reflection of light in an ultraviolet to infrared wavelength range, or the first cylindrical flow path and the second cylindrical shape. A flow cell characterized in that the surface of the flow path has a property of preventing reflection of light in an ultraviolet to infrared wavelength region.   2. The flow cell according to claim 1, wherein the main body is made of a resin containing black quartz or carbon fiber, or the surfaces of the first cylindrical flow path and the second cylindrical flow path are black quartz. Alternatively, a flow cell modified with diamond-like carbon, zinc oxide, or aluminum oxide.   2. The flow cell according to claim 1, wherein a total cross-sectional area of the fluid discharge section provided singly or in plurality is larger than a cross-sectional area of the flow path of the fluid introduction section. 5. The flow cell according to claim 4 , wherein a ratio of a total cross-sectional area of the fluid discharge unit to a cross-sectional area of the fluid introduction unit is a cross section perpendicular to the incident optical axis of the first cylindrical flow channel. A flow cell characterized by being equal to or greater than a ratio of a maximum cross-sectional area of a cross section perpendicular to the incident optical axis of the second cylindrical flow path to a minimum cross-sectional area. A light source for generating measurement light, a flow cell for flowing a sample, and a photodetector for detecting measurement light transmitted through the flow cell;
The flow cell includes a main body having a sample flow path through which the measurement light passes, and window materials provided on the light incident side and the light output side of the main body, and the sample flow path is connected to a fluid introducing portion. A first cylindrical flow path and a second cylindrical flow path connected to the fluid discharge portion, wherein the first cylindrical flow path has a constant cross-sectional area perpendicular to the incident optical axis. a flow passage, said second cylindrical passage is frustoconical flow path cross-sectional area perpendicular to the incident optical axis is increasing continuously along the traveling direction of the incident light, the first cross-sectional area perpendicular to the incident optical axis in the light emitting end of the tubular passage, Ri cross-sectional area perpendicular der following the incident optical axis in the light incident end of said second tubular flow channel,
The liquid analyzer is characterized in that the focal position of incident light from the light source is set closer to the light source than to the fluid discharge side of the first cylindrical channel . 7. The liquid analyzer according to claim 6 , wherein the flow cell is made of a material that prevents the main body from reflecting light in an ultraviolet to infrared wavelength range, or the first cylindrical flow path and A liquid analyzer characterized in that the surface of the second cylindrical channel has a property of preventing reflection of light in the ultraviolet to infrared wavelength region. 7. The liquid analyzer according to claim 6 , wherein the flow cell has the main body made of a resin containing black quartz or carbon fiber, or the first cylindrical flow path and the second cylindrical flow. A liquid analyzer characterized in that the surface of the path is modified with black quartz, diamond-like carbon, zinc oxide or aluminum oxide. 7. The liquid analysis apparatus according to claim 6 , wherein the flow cell has a total cross-sectional area of the fluid discharge section provided singly or in plurality, which is larger than a cross-sectional area of the flow path of the fluid introduction section. apparatus. 7. The liquid analyzer according to claim 6 , wherein the flow cell has a ratio of a flow path cross-sectional area of the fluid discharge unit to a flow path cross-sectional area of the fluid introduction part, the incident optical axis of the first cylindrical flow path. A liquid analyzer characterized by having a ratio equal to or greater than a ratio of a maximum cross-sectional area of a cross section perpendicular to the incident optical axis of the second cylindrical flow path to a minimum cross-sectional area of a cross section perpendicular to the vertical axis.

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