Measurement probe, measurement probe unit, measurement device, and measurement method

Abstract

Provided is a measurement probe for realizing a measurement device capable of measuring characteristic values of biopolymers, such as protein, in real time at a lower concentration than conventional devices. The measurement probe is used by being connected to a light source and a detector by means of an optical fiber, and comprises: a cylindrical housing having a first port and a second port formed at one end, the first port introducing light from a first optical fiber and outputting light to the first optical fiber, and the second port outputting light to a second optical fiber; a reflective member that is located inside the housing, is provided at an end of the housing on the opposite side to the end at which the first port and the second port are formed, and reflects and refracts light introduced from the first port toward the second port; and a measurement target liquid accommodating portion formed between two window members that are disposed on an output optical path passing between the reflective member and the second port.

Description

Measurement probe, measurement probe unit, measurement device and measurement method

[0001] The present invention relates to a measuring probe used in a measuring device or a measuring method for calculating characteristic values ​​of, for example, biopolymers.

[0002] For example, in the manufacturing process of biopharmaceuticals, accurate real-time measurement of the characteristic values ​​of low concentrations of biopolymers contained in the culture medium at the early stage of culture is required to appropriately control the production status of biologically derived high molecular weight compounds (biopolymers) such as antibodies.

[0003] While Raman spectroscopy is the mainstream of conventional measurement methods, fluorescence spectroscopy can further reduce the measurement range by 3 to 4 orders of magnitude. In particular, absorbance-transmittance-fluorescence excitation-emission matrix spectroscopy (A-TEEM), which simultaneously acquires absorbance, transmittance, and fluorescence excitation-emission matrix, can measure antibodies at concentrations of less than 1 μg / ml.

[0004] However, the measurement device used in the A-TEEM method described above is a stationary type, so it is difficult to measure the liquid to be measured immediately after it is collected. Instead, the collected liquid to be measured must be carried to a laboratory where the measurement device is installed, which makes it difficult to measure in real time.

[0005] Patent No. 6643333

[0006] The present invention has been made in consideration of these problems, and its main purpose is to provide a measurement probe for realizing a measurement device that can measure the characteristic values ​​of biopolymers such as proteins at lower concentrations than conventional methods in real time.

[0007] That is, the measurement probe according to the present invention is a measurement probe that is used by being connected to a light source and a detector by optical fibers, and comprises: a cylindrical housing having a first port at one end thereof for introducing light from a light source from a first optical fiber and guiding the light to the first optical fiber, and a second port for guiding the light to a second optical fiber; a reflecting member inside the housing, provided at the end opposite to the end of the housing where the first port and the second port are formed, for reflecting and refracting the light introduced from the first port toward the second port; and a measurement target liquid storage section formed between two window members arranged on the guiding light path that passes between the reflecting member and the second port.

[0008] According to this measurement probe, the measurement probe includes a first port, a second port, a reflecting member, and a measurement target liquid storage portion formed on the output light path, so that absorbance and transmittance are measured using light that travels from the inlet port through the reflecting member to the output port, and fluorescence is emitted from the measurement target liquid storage portion toward the reflecting member and extracted from the inlet port, thereby simultaneously obtaining absorbance, transmittance, and a fluorescence excitation-emission matrix. By measuring transmitted light along with fluorescence and scattered light in this way, the effects of the degree of light absorption by the sample liquid, such as absorption of excitation light (primary inner filter effect) and re-absorption of fluorescence (secondary inner filter effect), can be removed by correction, but the accuracy of this correction depends on the accuracy of detection of transmitted light. As described above, with the measurement probe according to the present invention, absorbance and transmittance are measured using light that travels from the inlet port through the reflecting member to the outlet port, and fluorescence emitted from the measurement target liquid storage portion toward the reflecting member can be extracted from the inlet port. Therefore, even if it is desired to place an optical element suitable for measuring fluorescence and scattered light on the light path, it is possible to configure the measurement probe so that no optical element is placed on the light path from which the transmitted light is extracted, thereby enabling the transmitted light to be detected as accurately as possible. As a result, the measurement results of fluorescence and scattered light can be corrected as accurately as possible using the detection results of transmitted light.

[0009] If a light-shielding member is further provided between the inlet light path from the first port to the reflecting member and the outlet light path from the reflecting member to the second port, the light returning directly from the measurement target liquid storage section to the first port can be reduced, thereby improving the accuracy of fluorescence measurement.

[0010] In a specific embodiment of the present invention, the first optical fiber is a bifurcated optical fiber bundle.

[0011] It is preferable to further provide a focusing optical system that collimates and / or parallelizes the light from the light source, the fluorescence, and the transmitted light, because this allows the light from the light source to be collimated or focused and irradiated inside the measurement target liquid storage section, and also allows the light from the measurement target liquid storage section to be collimated or focused and directed toward the first port or the second port.

[0012] If a polarizing plate disposed on the introduction light path is further provided, more combinations of measurement methods can be increased to obtain detailed information about biopolymers.

[0013] The present invention also includes a measurement device equipped with the measurement probe described above. This measurement device includes a measurement probe unit equipped with the measurement probe according to the present invention and an optical fiber, a light source, a detector, and an information processing unit that calculates a characteristic value of the liquid to be measured based on a signal from the detector.

[0014] It is preferable that the light source emits the excitation light of a plurality of wavelengths, specifically, wavelengths of 250 nm or more and 450 nm or less, and it is more preferable that the polarizing plate is compatible with all of the plurality of wavelengths.

[0015] According to the present invention, it is possible to provide a measuring device that is capable of measuring the characteristic values ​​of biopolymers such as proteins at lower concentrations than conventionally possible in real time.

[0016] 1 is a schematic diagram of an overall fluorescence measuring device according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of a fluorescence measuring probe according to an embodiment of the present invention.

[0017] An embodiment of the present invention will be described below with reference to the drawings.

[0018] The measuring device 100 according to this embodiment is used to measure the characteristic values ​​of biologically derived polymeric compounds (biopolymers), such as antibodies, contained in a measurement target liquid S, such as a culture medium supernatant, an antibody purified solution, or an active ingredient or biopharmaceutical formulation of a biopharmaceutical, including an antibody drug, using absorbance-transmitted light-fluorescence excitation emission matrix spectroscopy (A-TEEM).

[0019] The biopolymers are biologically derived polymeric compounds such as peptides, hormones, antibodies, and other proteins, viral vectors, and extracellular vesicles such as exosomes. The characteristic values ​​are values ​​that represent, for example, concentration, molecular weight, the state of association of the biopolymer, the molecular structure of the biopolymer (at least one of differences in the amino acid sequences constituting the biopolymer, the presence or absence of post-translational modifications, and the type of post-translational modifications), the presence or absence of impurities, and the amount of impurities. As shown in FIG. 1, the measuring device 100 includes a measuring device main body 1 equipped with a light source, a detector, and an information processing unit, and a measuring probe unit 2 equipped with a measuring probe connected to the measuring device main body 1 and immersed in the liquid S to be measured.

[0020] The light source 11 is not particularly limited as long as it can emit light that is irradiated onto the measurement target liquid to measure transmitted light, fluorescence, and scattered light. However, it is preferable that the light source 11 be capable of dispersing and emitting light with wavelengths of 250 nm to 450 nm. Specific examples include a light source equipped with a Xe lamp and a spectroscopic unit, or a combination of LEDs with different center wavelengths. The spectroscopic unit may be, for example, a monochromator, a filter wheel equipped with multiple bandpass filters, or a linear variable filter. A method for combining multiple types of LEDs may be, for example, a fiber bundle or a fiber multiplexer.

[0021] The detector 12 detects fluorescence and scattered light from the measurement target liquid S excited by excitation light from the light source, and is not particularly limited as long as it is used in absorbance-transmitted light-fluorescence excitation-emission matrix spectroscopy (A-TEEM). In this embodiment, the detector 12 includes two detectors: a detector 12a for detecting fluorescence and scattered light, and a detector 12b for detecting transmitted light. In order to perform spectrum measurement in a short time, it is desirable to use a one-dimensional or two-dimensional image sensor as the light-receiving element included in each detector.

[0022] The information processing unit 13, for example, calculates the characteristic values ​​of the liquid S to be measured based on information regarding the fluorescence, scattered light, and transmitted light output from the detector 12, and is configured to function as the information processing unit 13 by, for example, a so-called general-purpose computer equipped with a CPU, memory, input / output interface, etc., through cooperation of the CPU and its peripheral devices based on various application software (hereinafter referred to as programs) stored in the memory.

[0023] The probe unit 2 includes the above-mentioned measuring probe 21 and an optical fiber 22 that connects the measuring probe 21 to the measuring device main body 1 .

[0024] 1, the measurement probe 21 is connected to the light source 11 and the detector 12 provided in the measurement device main body 1 via the optical fiber 22, and is used by immersing its tip in the measurement target liquid S. As shown in Fig. 2, for example, the measurement probe 21 includes a cylindrical housing 211 connected to the optical fiber 22 to form an optical path therein, and a reflecting member 212 provided inside the housing 211 to refract light introduced from the optical fiber 22 into the housing 211 so as to return the light to the side from which the light was introduced, and direct the light toward the end of the housing 211 from which the light was introduced.

[0025] The optical fiber 22 includes, for example, a first optical fiber 221 that guides light from the light source 11 into the housing 211 and guides fluorescence and scattered light from the measurement target liquid S from the housing 211 to the detector 12, and a second optical fiber 222 that guides transmitted light that has passed through the measurement target liquid S from the housing 211 to the transmitted light detector 12b. Note that, as the first optical fiber, it is preferable to use a bifurcated optical fiber bundle in which the ends connected to the light source 11 and the detector 12 are bifurcated.

[0026] The housing 211 has a rectangular parallelepiped shape made of, for example, a metal or resin that does not transmit light, and is provided at one end in the longitudinal direction with a first port 211a that introduces light from the first optical fiber 221 and outputs the light to the first optical fiber 221, and a second port 211b that outputs the light to the second optical fiber 222. Although the case where the shape of the housing 211 is cylindrical is described here, it may have another shape, such as a rectangular parallelepiped.

[0027] The reflecting member 212 is not particularly limited as long as it can reflect light introduced into the housing 211 from the first port 211a toward the second port 211b. In this embodiment, the reflecting member 212 is a retroreflector formed of, for example, a mirror or a corner cube. In this embodiment, as shown in FIG. 2, the reflecting member 212 has two reflecting surfaces that are arranged to face each other and form a 90° angle between them. With this configuration, in this embodiment, light introduced into the housing from the first port is refracted twice by these two reflecting surfaces and directed toward the second port. Light from a light source introduced into the housing from the first port is directed toward the reflecting member through an introduction optical path L1, is reflected and refracted by the reflecting member, and then directed toward the second port through an extraction optical path L2.

[0028] The measuring probe 21 according to this embodiment further includes a light-shielding member 213. This light-shielding member is, for example, a light-shielding plate that separates the aforementioned introduced light path L1 and the extracted light path L2 and blocks light. It is desirable that the light-shielding plate be subjected to anodizing treatment or the like in order to reduce stray light.

[0029] Two window members 214a, 214b are disposed on the output light path L2 formed between the reflecting member 212 and the optical fiber 22, and a measurement target liquid storage section 214 is formed between these two window members 214a, 214b. The measurement target liquid storage section 214 is a recess formed inward from the side peripheral surface of the housing 211. For example, the window members 214a, 214b are disposed so as to abut the light-shielding member 213 disposed inside the housing 211 from an opening formed in the side peripheral surface of the housing 211, and these two window members 214a, 214b and the light-shielding member 213 partition the space inside the housing 211 so that the measurement target liquid S does not enter. In this embodiment, the two window members 214a, 214b are disposed parallel to each other, i.e., perpendicular to the output light path L2.

[0030] It is preferable that the light-shielding member 213 is provided so as to stand from the end of the housing 211 on the side where the first port 211a and the second port 211b are formed toward the end where the reflecting member 212 is disposed, so as to prevent fluorescence or scattered light generated in the measurement target liquid storage section 214 from directly entering the first port 211a, and is disposed at a position as close as possible to the reflecting member 212 than the end of the measurement target liquid storage section 214 on the reflecting member 212 side, and extends to a position that does not interfere with the refraction of light by the reflecting member 212. It is more preferable that a part of the end of the light-shielding member 213 on the side closest to the reflecting member 212 is disposed between the two reflecting surfaces.

[0031] With this configuration, transmitted light is detected as light that is introduced from the first port, passes through the measurement target liquid storage section 214, and is extracted from the second port 211b, and fluorescent light and scattered light are detected as light that is emitted from the measurement target liquid storage section 214 toward the reflecting member 212, and is reflected by the reflecting member 212 to be returned to the first port 211a and extracted from the first port 211a.

[0032] The measurement probe 21 according to this embodiment further includes a focusing optical system 215 that collimates and / or focuses the light, fluorescence, scattered light, and transmitted light from the light source 11, and a polarizing plate 216 that transmits the light, fluorescence, and scattered light from the light source.

[0033] The focusing optical system 215 includes, for example, a collimator that collimates the light introduced into the housing 211 from the first port 211a and / or a lens that focuses the fluorescence, scattered light, and transmitted light from the measurement target liquid S. For example, an aluminum reflective collimator can be used as the collimator. A wide range of lenses can be used as the lens, including plano-convex lenses, aspherical lenses, and achromatic doublet lenses. For the lens, it is preferable to use fused silica or calcium fluoride, which has a relatively high transmittance and is relatively stable even against UV light, in case ultraviolet light is used as the excitation light.

[0034] The polarizing plate 216 is not particularly limited as long as it is compatible with the wavelengths of the light, fluorescence, and scattered light from the light source 11, but it is preferable to use a wire grid polarizing plate, for example, because it can be used without any problems even with UV light and can control the polarization of light regardless of the direction of incidence of the light on the polarizing plate 216. It is preferable that this polarizing plate 216 is compatible with light of all wavelengths included in the light emitted from the light source 11.

[0035] In this embodiment, the measurement probe 21 further includes a connection housing 217 that connects the optical fiber 22 and the housing 211. The connection housing 217 is connected to the first optical fiber 221 and the second optical fiber 222, and forms therein a connection introduction optical path L3 through which light introduced from the first optical fiber 221 into the housing 211 and light derived from the housing 211 to the first optical fiber 221 passes, and a connection extraction optical path L4 through which light derived from the housing 211 to the second optical fiber 222 passes.

[0036] 2, the connection housing 217 is cylindrical and made of an opaque material such as metal or resin, and has a diameter larger than that of the housing 211. The connection housing 217 has, for example, a first connection port 217a for connecting to the first optical fiber 221 and a second connection port 217bt for connecting to the second optical fiber 222 at one end, and an opening 217c for inserting and connecting the housing 211 at the other end. The inner diameter of this opening 217c is configured to exactly fit the outer diameter of the housing 211, and by inserting the end of the housing 211 where the first port 211a and the second port 211b are formed, the housing 211 can be fixed so that the connection inlet optical path L3 and the inlet optical path L1 are connected in a straight line via the first port 211a, and the connection outlet optical path L4 and the outlet optical path L2 are connected in a straight line via the second port 211b.

[0037] In this embodiment, a collimator attached to the position of the first connection port 217a of the connection housing 217 and window members 214a, 214b forming the measurement target liquid storage portion 214 are lenses, and these collimator and lenses constitute the above-mentioned light collecting optical system 215. Also, in this embodiment, the polarizing plate 216 is disposed on the connection introduction light path L3 inside the connection housing 217 and perpendicular to the connection introduction light path L3.

[0038] A method for measuring biopolymers using the measurement probe 21 and measurement device 100 according to this embodiment is, for example, as follows: The housing 211 is attached to the tip of the connection housing 217 of the measurement probe 21. With the measurement probe 21 positioned so that the tip of the attached housing 211 comes into contact with the measurement target liquid S, light in a predetermined wavelength range (e.g., 250 nm or more and 450 nm or less) is emitted from the light source 11. The light source 11 sequentially emits light within a predetermined wavelength range, changing the wavelength by one wavelength at a time.

[0039] Light from the light source 11, which is guided into the connection housing 217 via the optical fiber 22 and the first connection port 217a, is collimated by the collimator, passes through the polarizing plate 216, and is introduced into the housing 211 from the first port 211a and directed toward the reflecting member 212. The light from the light source 11, which is reflected and refracted by the reflecting member 212, is collected by a window member 214a and irradiated onto the measurement target liquid S in the measurement target liquid storage section 214. Of the fluorescence and scattered light emitted from the measurement target liquid S, the fluorescence and scattered light emitted toward the reflecting member 212 is collected by the window member 214a and then directed toward the first port 211a by the reflecting member 212. On the other hand, the transmitted light that has passed through the measurement target liquid S is collected by a window member 214b and then travels straight toward the second port 211b. The light that enters the connection housing 217 from the first port 211a passes through the polarizer 216 and the collimator, is output from the first connection port 217a to the first optical fiber 221, and is guided to the detectors 12a and 12b via the first optical fiber 221. The light that enters the connection housing 217 from the second port 211b is output from the second connection port 217b to the second optical fiber 222, and is guided to the detector 12b via the second optical fiber 222.

[0040] Information such as the wavelength and intensity of the fluorescence, scattered light, and transmitted light for each wavelength of light from the light source 11 detected by the detector 12 is sent from the detector 12 to the information processing unit 13, and the information processing unit 13 receives this information and performs analysis using the A-TEEM method based on the wavelength of the light from the light source and the wavelength and intensity of the fluorescence and transmitted light detected by the detector 12.

[0041] Furthermore, the information processing unit 13 estimates characteristic values ​​such as the size of the biopolymer based on information such as the wavelength and intensity of the scattered light detected by the detector 12, and the amount of change in intensity over time.

[0042] Thereafter, the information processing unit 13 may combine information about the characteristic values ​​of the biopolymer calculated by the A-TEEM method and information about the biopolymer estimated based on the scattered light, and output the combined information to a display unit (not shown). When the measurement of one sample liquid S is completed, the housing 211 is removed from the connecting housing 217. When the next sample liquid S is to be measured, the same procedure may be repeated from the beginning using a new housing 211, or the next measurement may be performed after cleaning the housing 211 without removing it.

[0043] <Effects of the present embodiment> According to the measurement probe 21 and measurement device 100 configured in this manner, the measurement probe 21 includes a reflecting member 212 that is provided at the end of the housing 211 opposite to the end where the first port 211a and the second port 211b are formed, and that reflects and refracts light introduced from the first port 211a toward the second port 211b, and a measurement target liquid storage portion 214 that is formed between two window members 214a, 214b that are arranged on an output light path L2 that passes between the reflecting member 212 and the second port 211b. Therefore, it is possible to provide a measurement device that includes a tabletop measurement device main body that can perform analysis by the A-TEEM method using a measurement probe that has the same shape as the housing of a general-purpose measurement probe that is conventionally used in Raman spectroscopy, etc.

[0044] Furthermore, not only is the measurement device main body 1 made smaller, but the measurement probe 21 connected to the light source 11 and detector 12 by an optical fiber 22 can be immersed in the measurement target liquid S contained in a container for measurement, and therefore, according to the measurement device 100 equipped with the measurement probe 21 of this embodiment, it is possible to measure characteristic values ​​such as the concentration of biopolymers contained in the measurement target liquid S in real time, without the need to take a portion of the measurement target liquid S and set it in the measurement device 100.

[0045] Furthermore, the measuring device 100 according to the embodiment actively measures scattered light, which has traditionally been removed or corrected as noise during fluorescence measurement, and can also measure transmitted light. Therefore, as described above, fluorescence, scattered light, and transmitted light can be measured in real time to perform analysis using the A-TEEM method. As a result, various information can be obtained in a single measurement, including not only the biopolymer concentration but also the molecular weight, the state of association or aggregation, the molecular structure of the biopolymer (at least one of differences in the amino acid sequence constituting the biopolymer, the presence or absence of post-translational modifications, and the type of post-translational modifications), the presence or absence of impurities, and the amount of impurities. Furthermore, by measuring transmitted light, the effects of light absorption by the sample solution, such as absorption of excitation light (primary inner filter effect) and re-absorption of fluorescence (secondary inner filter effect), can be corrected, thereby enabling more accurate measurement of biopolymer characteristic values. Regarding the handling of characteristic values ​​before and after correction, only the corrected characteristic values ​​may be presented to the user, or both the corrected and corrected characteristic values ​​may be presented.

[0046] Since the light source 11 emits light with a wavelength of 250 nm or more and 450 nm or less as excitation light, this measurement method is particularly suitable for measuring the concentration of peptides, proteins, and the like.

[0047] Since a two-branch optical fiber bundle is used as the first optical fiber 221, the number of components in the measurement probe 21 can be reduced as much as possible, making the measurement probe 21 as small as possible, compared to when three or more optical fibers are connected to the measurement probe 21.

[0048] Since the measurement probe 21 is equipped with a connection housing 217, there is no need to worry about the relatively expensive polarizing plate 216 etc. coming into direct contact with the liquid S to be measured, and if necessary, only the housing 211 can be removed and replaced, which is economical.

[0049] Since the first connection port 217a also functions as a collimator and the window members 214a and 214b are lenses, the light from the light source 11 can be adjusted to a state suitable for measurement or to a state that is easily transmitted by the optical fiber 22, thereby further improving measurement accuracy.

[0050] Since the measurement probe 21 according to this embodiment further includes the polarizing plate 216, it can also be used in a polarization-fluorescence matrix measurement method.

[0051] The present invention is not limited to the above-described embodiment. For example, the above-described components such as the focusing optical system and polarizing plate are not essential, and each component may be combined as needed. The above-described window member does not need to be a lens, and may be any transparent member that can transmit light. The connection housing may not be provided, and optical fibers may be directly connected to the first port and the second port of the housing.

[0052] It goes without saying that the above-described embodiments and modified embodiments may be combined in part or in whole as appropriate, and various modifications are possible within the scope of the spirit thereof.

[0053] According to the present invention, it is possible to provide a measurement probe for realizing a measurement device capable of measuring in real time the characteristic values ​​of biopolymers such as proteins at concentrations lower than conventionally possible.

[0054] REFERENCE SIGNS LIST 100 Measuring device 1 Measuring device main body 11 Light source 12 Detector 13 Information processing unit 2 Measuring probe unit 21 Measuring probe 211 Housing 212 Reflecting member 213 Light blocking member 214 Measurement target liquid storage section L1 Introduced light path L2 Ejected light path 22 Optical fiber 221 First optical fiber 222 Second optical fiber S Measurement target liquid

Claims

1. The measurement probe is a measurement probe that is used by being connected to a light source and a detector by optical fibers, and comprises: a cylindrical housing having a first port at one end for introducing light from a first optical fiber and guiding the light to the first optical fiber, and a second port for guiding the light to a second optical fiber; a reflecting member inside the housing, provided at the end opposite to the end of the housing where the first port and the second port are formed, for reflecting and refracting the light introduced from the first port toward the second port; and a measurement target liquid storage section formed between two window members arranged on the guiding light path passing between the reflecting member and the second port.

2. A measurement probe as described in claim 1, further comprising a light blocking member disposed between an inlet light path from said first port to said reflecting member and an outlet light path from said reflecting member to said second port.

3. A measurement probe as claimed in claim 1 or 2, wherein the first optical fibre is a two-branch optical fibre bundle.

4. A measurement probe according to any one of claims 1 to 3, further comprising a focusing optical system for collimating and / or parallelizing the light from the light source, the fluorescent light and the transmitted light.

5. A measurement probe according to any one of claims 1 to 4, further comprising a polarizing plate disposed on the introduction light path.

6. A measurement probe unit comprising: a measurement probe according to any one of claims 1 to 4; and an optical fiber connected to the measurement probe.

7. A measuring device comprising: a light source that emits the excitation light; a measurement probe unit according to any one of claims 1 to 6; a detector that detects the fluorescence and the transmitted light; and an information processing unit that calculates a characteristic value of the liquid to be measured based on the fluorescence and the transmitted light detected by the detector.

8. The measuring device according to claim 7, wherein said detector detects scattered light from said liquid to be measured.

9. The measuring device according to claim 7 or 8, wherein the light source emits the excitation light of a plurality of wavelengths.

10. The measuring device according to any one of claims 7 to 9, wherein the light source emits light with a wavelength of 250 nm or more and 450 nm or less.

11. A measurement method using a light source which irradiates light onto a liquid to be measured, a detector which detects light emitted from the light source and transmitted through the liquid to be measured and fluorescence generated from the liquid to be measured by the light from the light source, and a measurement probe which is connected to the light source and the detector by optical fibers, wherein the measurement probe comprises a cylindrical housing having a first port at one end which introduces light from a first optical fiber and outputs light to the first optical fiber, and a second port which outputs light to a second optical fiber, a reflecting member inside the housing and provided at the end opposite to the end of the housing where the first port and the second port are formed, which reflects and refracts the light introduced from the first port towards the second port, and a measurement liquid storage section formed between two window members arranged on an output light path passing between the reflecting member and the second port.

12. The method according to claim 11, wherein the liquid to be measured contains a biopolymer.

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