JP4712745B2 - Flow cell for transmitted light measurement - Google Patents

Description

  The present invention relates to a flow cell for measuring optical properties.

  As light passes through the liquid, it is absorbed by the solute, and the light intensity decays as a function of the product of the solute concentration and the transmission distance (Lambert-Beer law). Therefore, the concentration of the solute in the liquid can be measured optically by measuring the intensity of transmitted light. Here, a calibration curve is obtained in advance, and the transmitted light intensity is measured to obtain the concentration of the solute.

  In an apparatus for measuring the light absorption of a liquid, the liquid is allowed to flow through the flow cell, and the attenuation of light intensity is measured for the light transmitted through the flow cell. The flow cell has a certain transmission distance (cell length).

In the present invention, an optical window having a stepped structure is used for the flow cell. As a result of searching the prior art for this, in the flow cell described in Japanese Patent Laid-Open No. 53-112785, in order to measure a sample with a high flow rate, a plurality of portions having different window plate intervals are formed in one flow cell. ing. This is to solve the problem that when the optical path length of the flow cell is shortened, the cross-sectional area of the flow path decreases and a problem arises in pressure resistance. In the sample analysis cell described in Japanese Utility Model Laid-Open No. 1-151240, the interval between two cell windows is widened outside the optical path, and a plurality of sample inlets are provided. In addition, in the sample analysis cell described in Japanese Patent Application Laid-Open No. 7-12713, in order to solve the problem that a pressure pump or the like is required when the cell length is short, an excess fluid is placed around the flow cell. In order to flow, a fluid passage having a cross-sectional area substantially equal to the cross-sectional area of the flow path of the piping is provided to reduce the pressure loss in the flow cell. In this flow cell, the light transmission part has, for example, a shape of a bottomed cylinder or a peeled cylindrical bar. Japanese Patent Application Laid-Open No. 7-12713 and Japanese Patent Application Laid-Open No. 8-68746 describe a flow cell used for measuring a highly corrosive chemical solution.
JP-A-53-112785 Japanese Utility Model Publication No. 1-151240 JP 7-12713 A JP-A-8-68746

Transmitted light measurement using a flow cell is applied to various liquids. Here, it is desired that measurement is possible even when a high-pressure fluid is used as a target.
An object of the present invention is to provide a flow cell that can be used in a high-pressure state.

  A transmitted light measurement flow cell according to the present invention is a pair of optical windows made of a light transmissive material, each including a first surface facing each other and a second surface wider than the first surface, and a peripheral portion of the second surface. A cell body made of a metal material provided with a pair of optical windows having a flange-shaped portion and a flow path for flowing a fluid to be measured, and a through hole is formed in the direction perpendicular to the flow path in the middle of the flow path. A cell main body provided with a stepped portion for supporting the flange-shaped portion of the pair of optical windows in the through hole, and a fixing member for airtightly fixing the pair of optical windows supported by the cell main body. . Here, the first surfaces of the pair of optical windows are in the flow path and are opposed to each other at a constant interval, and the surfaces of the pair of optical windows are the first in the portion that contacts the liquid to be measured. It is opaque except on the surface.

  In the transmitted light measurement flow cell, the portion in contact with the liquid to be measured includes a surface subjected to roughening (for example, blasting) other than the first surface.

  The transmitted light measurement flow cell preferably further includes a condensing optical system that condenses light on a flow path between the first surfaces of the pair of optical windows outside the cell main body.

  In the transmitted light measurement flow cell, for example, the distance between the pair of first surfaces is 1 mm or less, and the first surfaces are circular with a diameter of between 3 mm and 10 mm.

  The spectrophotometer includes a sampling unit including the flow cell, and a spectroscopic unit that generates light that passes through the flow cell and receives the light transmitted through the flow cell.

The liquid chromatography device according to the present invention generates a light that passes through the flow cell and receives the light that has passed through the flow cell, the column for liquid chromatography, the flow cell through which the liquid sample separated by the column flows. And a detector.

The flow cell can be used without being damaged even under high pressure.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a cross section of a flow cell that can be used in high temperature and high pressure conditions. The flow cell includes a cell body 10, a pair of light transmission members (optical windows) 16 and a window plate 18. The high temperature and high pressure state is, for example, a liquid temperature of 130 ° C. and a pressure of 0.4 MPa.

  The cell body 10 of the flow cell is made of a metal material (for example, stainless steel) that is not corroded by the liquid to be measured. Inside the elongated cell body 10, a flow path 12 is provided from one end to the other end in the longitudinal direction, and a connection structure capable of connecting the high-pressure joint 20 is provided at both ends of the flow path 12. The cell body 10 includes two outer surfaces parallel to each other, and a pair of through holes 14 are provided on the outer surfaces in the middle of the flow channel 12 so as to face each other in a direction perpendicular to the flow channel 12. It is done. The through hole 14 is provided with a bore portion 14 a having a shape into which the optical window 16 can be fitted. In the example shown in FIG. 1, two pairs of through holes are provided.

  The optical window 16 is made of a light transmitting material (quartz, sapphire, etc.) that is transparent at the measurement wavelength. The optical window 16 is thick and has pressure resistance. The optical window 16 includes a first surface 16a and a second surface 16b facing each other and a stepped portion 16c (see FIG. 2). The second surface 16b is wider than the first surface 16a, and the edge of the second surface 16b has a flange shape. The first surface 16a for transmitting light is optically polished. The structure of the optical window 16 shown in the figure is a shape in which two disks are stacked. However, the shape around the first surface 16a to be optically polished is not limited to the structure shown in the figure. For example, the shape may change in thickness in three stages.

  Since the optical window 16 has a large thickness (window thickness), extraneous light is incident around the first surface and has an adverse effect. Therefore, the portion of the optical window 16 that is in contact with the liquid to be measured other than the first surface 16a is subjected to roughening (for example, blasting) so as not to transmit light. Incidentally, in the conventional flow cell of Japanese Patent Laid-Open No. 53-112785 using the step-shaped light transmitting member, the portions having different cell lengths are adjacent to each other so that the light enters the desired cell length portion. Be controlled. There is no mention of the effects of stray light.

  A window plate 18 having a circular opening is screwed to the outer surface of the cell body 10 to hold the optical window 16 between the window plate 18 and the cell body 16. At this time, the inner side of the flange-shaped portion (peripheral brim shape) of the optical window 16 is brought into close contact with the bore portion 14a of the through hole 12, and the optical window 16 is attached to the cell body 10 using an O-ring, packing, or the like. Fix liquid tightly. The window plate 18 is an example of a fixing member that fixes the optical window 16 to the cell body 10 in a liquid-tight manner. The shape of the hole 14a and the characteristics such as the O-ring and packing are determined according to the state of use.

  In the flow cell configured as described above, the first surfaces 16a of the pair of optical windows 14 face each other at a constant interval (cell length), and the fluid to be measured introduced into the flow path 12 flows between them. The cell length is, for example, 1.0 to 0.5 mm, and the diameter of the first surface 16a is, for example, φ3 to 10, preferably φ5 to 10. When the cell length is as short as 1.0 mm or less, the mixing rate of air and the adhesion rate of dust increase. Therefore, by reducing the area with 10 mm as the upper limit, the adhesion rate is reduced. The lower limit depends on the optical path diameter used, but here it is 3 mm. The thickness of the optical window 14 is determined in consideration of the pressure resistance characteristics.

  As described above, the cell body 10 is made of a non-corrosive metal material, and the thickness of the optical window 16 is increased. For this reason, the flow cell can be used under high pressure. In addition, although a liquid flows into the side part of the optical window 16, this is not intended to compensate for the pressure loss in the flow cell, unlike the flow cell described in JP-A-7-12713. Moreover, since the cell body 10 and the optical window 16 are made of a material that can be used at high temperatures, they can be used at high temperatures. For example, this flow cell can be used without damaging an aqueous solution under a high temperature and a high pressure of, for example, a liquid temperature of 130 ° C. and a pressure of 0.4 MPa.

  As shown in FIG. 3A, a lens optical system (condensing optical system) 30 is preferably incorporated between optical fiber connectors 32 provided on both sides of the flow cell. The light introduced from the connector 32 through one optical fiber is condensed on the cell length portion of the flow cell by the lens optical system 30 to reduce light loss between the fibers. The light that has passed through the flow cell is collected by the other lens optical system 30, passes through the other connector 32, and is introduced into another optical fiber. Since incident light is focused on the cell length, dark samples and turbid samples that are difficult to transmit light can be measured. In addition, since light to the flow cell generated in the spectroscopic part of the measuring device is introduced via an optical fiber, changes in the cell part (such as temperature changes) affect the spectroscopic part located away from the cell part. do not do.

  As shown in FIG. 3B, when light is transmitted through a portion around the first surface 16a subjected to optical polishing in the optical measurement, the transmitted light (stray light) adversely affects the measurement. Therefore, in order to transmit light only to the first surface 16a, in the flow cell of FIG. 3A, the light bypass portion is blasted as described above. Thereby, since incident light passes only the 1st surface 16a in a flow path, the bad influence by the extraneous light and stray light which pass other than the 1st surface 16a can be prevented. For this reason, incident light is condensed with respect to the optical polishing surface 16a, whereby the transmitted light intensity is increased, and attenuation of light for entering the blasted portion can be reduced.

Table 1 shows optical changes with and without sandblasting (masking). The measurement sample is water. The measured values shown in Table 1 are measured values (light intensity) of the optical sensor when the same light is incident. A large value indicates that the detected light intensity is high. The increase in detected light intensity is due to stray light.

  Since this flow cell is a multistage cell, the cell length can be automatically changed. Therefore, measurements with different cell lengths can be performed. Further, different cell lengths can be measured continuously.

  FIG. 4 schematically shows a configuration of an example of a spectrophotometer in the infrared region, visible region, or ultraviolet region using the above-described flow cell. The spectrophotometer includes a spectroscopic unit 40, a sampling unit 60, and a data processing unit 70.

  In the spectroscopic unit 40, emitted light from a light source 42 made of, for example, a tungsten / halogen lamp is collected by a convex lens 44 and passes through a diaphragm 46 disposed at the focal position of the convex lens 44. The rotating disk 50 holds a plurality of interference filters 48 at equiangular intervals, and is rotated by a driving motor 52 at, for example, 1000 rpm. The transmission wavelength of the interference filter 48 of the rotating disk 50 may be determined according to the sample. The light transmitted through any one of the interference filters 48 is collected by the convex lens 44. The collected light is connected to the connector 32 through the optical fiber 64 in the sampling unit 60. As shown in FIG. 2, the sampling unit 60 includes a flow cell 62 directly connected to a part of the circulation line, a convex lens, and two optical fibers 64. The connector 32 is positioned so as to transmit light in a direction orthogonal to the flow of the sample via the convex lens 56 with the flow cell 62 interposed therebetween, and the optical fiber 64 is connected to the connector 32. Further, although not shown, the flow cell 62 is directly connected to a circulation line that supplies a high-pressure solution sample. The light transmitted through the flow cell 62 enters the light receiving element 58 through the convex lens 56 through the optical fiber 64 connected to the connector 32. The light receiving element 58 converts incident light into photocurrent.

  In the data processing unit 70, the amplifier 71 amplifies the transmitted light intensity signal corresponding to the intensity of the transmitted light of the flow cell 62 output as the photocurrent from the light receiving element 58, and the A / D converter 72 Convert the output to a digital signal. The data processing device 73 calculates the absorbance of light of a plurality of wavelengths from the transmitted light intensity signal input from the A / D converter 72, and calculates and stores the calculated absorbance of each wavelength of light and as described later. The concentration of the solute is calculated from the absorbance at each wavelength based on the calibration curve formula. The data processing device 73 includes, for example, a microprocessor 74 that performs concentration calculation, a RAM 75 that stores calibration curves and various data, a ROM 76 that stores programs for operating the microprocessor 74, data and various commands. An input device 57 such as a keyboard for inputting, an output device 78 such as a printer and a display for outputting the result of the data processing, and the like are included. The microprocessor 74 also generates a drive control signal for the drive motor 52 that rotates the rotating disk 50. For the data processing for concentration determination in the data processing unit 70, for example, a known method described in JP-A-6-265471 may be used.

The above-described flow cell can also be used in a liquid chromatography apparatus. FIG. 5 shows an example of a liquid chromatography apparatus. The solvent is sent to the column 84 by the liquid feed pump 80. On the other hand, the sample is injected into the solvent by the injector 82. In the column 84, the sample is separated for each component. Next, each component flows through the flow cell 86, and an optical characteristic (for example, absorbance) is detected by the detector 88. Thereafter, in the fraction collector, the separated fractions are collected in separate containers.

Cross section of flow cell Optical window illustration Flow cell with condensing optics Block diagram of a spectrophotometer with a flow cell Block diagram of a liquid chromatography apparatus equipped with a flow cell

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 cell main body, 12 flow path, 14 through-hole, 16 optical window, 16a 1st surface, 18 window plate, 20 high pressure joint, 30 lens optical system, 62 flow cell.

Claims (6)

A pair of optical windows made of a light transmitting material, each having a first surface facing each other and a second surface wider than the first surface, and a pair of optical windows having a flange-shaped peripheral portion of the second surface When,
A cell body made of a metal material provided with a flow path for flowing a fluid to be measured, comprising a through hole in a direction perpendicular to the flow path in the middle of the flow path, and the pair of optical windows in the through hole A cell body provided with a stepped portion for supporting the flange-shaped portion of
A fixing member that hermetically fixes the pair of optical windows supported by the cell body;
The first surfaces of the pair of optical windows are in the flow path and are opposed to each other at regular intervals,
The transmitted light measurement flow cell, wherein the surfaces of the pair of optical windows are opaque except for the first surface at a portion in contact with the liquid to be measured.   The transmitted light measurement flow cell according to claim 1, wherein the portion in contact with the liquid to be measured includes a roughened surface other than the first surface.   The transmitted light measurement flow cell according to claim 1, further comprising a condensing optical system that condenses light on a flow path between the first surfaces of the pair of optical windows on the outside of the cell body. Transmitted light measurement flow cell.   2. The transmitted light measurement flow cell according to claim 1, wherein an interval between the pair of first surfaces is 1 mm or less, and the first surface is a circle having a diameter of between 3 mm and 10 mm. A sampling unit comprising the flow cell according to any one of claims 1 to 4,
A spectrophotometer comprising: a spectroscopic unit that generates light that passes through the flow cell and receives the light that has passed through the flow cell. A column for liquid chromatography;
The flow cell according to any one of claims 1 to 4, wherein a liquid sample separated by the column is flowed;
A liquid chromatography apparatus comprising: a detector that generates light that passes through the flow cell and receives the light that has passed through the flow cell.

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