WO2024042756A1

WO2024042756A1 - Reagent for measuring fluorine ion concentration, method for measuring fluorine ion concentration, and device for measuring fluorine ion concentration

Info

Publication number: WO2024042756A1
Application number: PCT/JP2023/011011
Authority: WO
Inventors: エウヘニオヘルナンオタル; マヌエラレティシアキム; 睦木村
Original assignee: 国立大学法人信州大学
Priority date: 2022-08-23
Filing date: 2023-03-20
Publication date: 2024-02-29

Abstract

Provided is a reagent for measuring fluorine ion concentration, which makes it possible to measure fluorine ion concentration by using visible light.　The present invention provides a reagent for measuring fluorine ion concentration, including a metal organic framework and pigment molecules that can absorb visible light, wherein the pigment molecules are coordinate-bonded to the metal organic framework, and the reagent is composed such that when the reagent is mixed with an aqueous sample that may contain fluorine ions, the fluorine ions become coordinated with the metal in the metal organic framework, and the pigment molecules become released from the metal organic framework.

Description

Fluoride ion concentration measurement reagent, fluoride ion concentration measurement method, fluoride ion concentration measurement device

The present invention relates to reagents, methods, and devices used to measure fluorine ion concentrations in water.

Volcanic rocks containing high concentrations of fluorine are distributed in eastern Africa due to alkaline volcanic activity. In Tanzania in particular, groundwater and river water that has passed through the ground containing high concentrations of fluorine is used as fresh water resources. These freshwater resources contain high concentrations of fluorine.

When freshwater resources containing fluorine are used for domestic or agricultural purposes, fluoride accumulates in the human body. However, fluoride has the aspect of being a toxic substance with acute or chronic effects. Fluoride has strong chronic toxicity, and fluoride poisoning has occurred in countries such as Africa and other countries due to fluoride contamination of drinking water. Symptoms of fluoride toxicity include mottled teeth and bone sclerosis. Treatment of fluoride poisoning is difficult, and cases of severe acute poisoning may result in death.

On the other hand, the use of freshwater resources is required due to geographical or economic water shortages. When utilizing freshwater resources, a method for measuring the fluorine concentration contained in freshwater resources is required.

Patent Document 1 discloses a method of measuring fluorine ion concentration by irradiating a test solution with ultraviolet rays and measuring the intensity of the generated fluorescence.

Patent No. 7033818

However, in order to perform measurements more cheaply and safely, it is desirable to measure fluorine ion concentration using visible light rather than ultraviolet light.

The present invention has been made in view of the above circumstances, and provides a reagent for measuring fluorine ion concentration that makes it possible to measure fluorine ion concentration using visible light.

According to the present invention, the following inventions are provided. [1] A reagent for measuring fluorine ion concentration, comprising a metal-organic structure and a dye molecule capable of absorbing visible light, wherein the dye molecule is coordinately bonded to the metal-organic structure, and the dye molecule is coordinately bonded to the metal-organic structure. is such that when sample water that may contain fluorine ions and the reagent are mixed, the fluorine ions are coordinated to the metal of the metal-organic structure and the dye molecules are liberated from the metal-organic structure. consisting of reagents.
[2] The reagent according to [1], wherein the dye molecule has a carboxyl group.
[3] The reagent according to [1], wherein the dye molecule is excited by the visible light and can emit fluorescence.
[4] The reagent according to [1], wherein the dye molecule is a xanthene dye molecule, an azo dye, or a phthalein dye having a carboxyl group.
[5] The reagent according to [4], wherein the dye molecule is the xanthene dye molecule, and the xanthene dye molecule is rose bengal, erythrosin, eosin Y, fluorescein, rhodamine, or calcein. reagent.
[6] The reagent according to [1], wherein the metal of the metal-organic structure contains iron, zirconium, aluminum, yttrium, or a lanthanoid rare earth metal element.
[7] The reagent according to [1], wherein the metal-organic structure has a periodic structure in which secondary structural units constituted by metal polynuclear clusters are bonded to each other by polydentate organic ligands. has a reagent.
[8] The reagent according to [7], wherein the metal polynuclear cluster is a metal hexanuclear cluster.
[9] The reagent according to [1], wherein the metal organic framework is MOF76, MOF199, UiO-66, UiO-67, isoreticular series of UiO-66, MIL-53, MIL- 67, or MIL-101.
[10] The reagent according to any one of [1] to [9], wherein the metal organic structure is supported on carrier particles.
[11] The reagent according to [10], wherein the carrier particles are composed of an inorganic oxide.
[12] The reagent according to [11], where the average particle size of the inorganic oxide is D1, and the average particle size of the particles obtained by supporting the metal-organic structure on the inorganic oxide is D2. , D2/D1 is 1.5 or less.
[13] A method for measuring fluorine ion concentration, comprising a sample preparation step, a measurement step, and a concentration determination step, wherein in the sample preparation, the reagent according to any one of [1] to [12], A measurement sample is prepared by mixing sample water that may contain fluorine ions, and in the measurement step, a physical quantity correlated with the concentration of the dye molecules in the measurement sample is measured using visible light, and the concentration determination step Here, a method for determining the fluorine ion concentration of the sample water based on the physical quantity.
[14] The method according to [13], wherein the fluorine ion concentration in the sample water is 20 ppm or less.
[15] The method according to [13], wherein the concentration of the reagent in the measurement sample is 0.05 to 1 mg/mL.
[16] The method according to [13], wherein the physical quantity is the transmitted light intensity of the visible light or the intensity of fluorescence emitted when the dye molecule is excited by the visible light.
[17] The method according to any one of [13] to [16], wherein the metal organic structure is supported on carrier particles, and in the measurement step, visible light is applied to the measurement sample. In the irradiated state, an image of the measurement sample is taken using an image sensor having a plurality of light receiving elements, and in the density determination step, a representative value obtained for the gradation value of at least one color component in the image is taken. A method for determining the fluorine ion concentration of the sample water based on.
[18] A fluorine ion concentration measuring device comprising a sample holding section, a measuring section, and a concentration determining section, wherein the sample holding section contains the reagent according to any one of [1] to [12]. , holds a measurement sample prepared by mixing sample water that may contain fluorine ions, and the measurement section measures a physical quantity correlated with the concentration of the dye molecules in the measurement sample using visible light, The concentration determining unit is a device that determines the fluorine ion concentration of the sample water based on the physical quantity.
[19] The device according to [18], wherein the device includes an information processing device and an adapter that can be communicatively connected to the information processing device, and the information processing device includes the concentration determining section. , wherein the adapter includes the sample holding section and the measuring section.
[20] The device according to [19], wherein the measuring section of the adapter is configured to be operable by being supplied with power from the information processing device.
[21] The device according to [19], wherein the information processing device includes a positioning section, a storage section, and a superimposed display section, and the positioning section acquires current position data at the time of the measurement. The storage unit stores the fluorine ion concentration and the current position data in association with each other as measurement data, and the superimposition display unit displays the measurement data read from the storage unit in a superimposed manner on a map. .

In the reagent of the present invention, fluorine ions (F ^- , also referred to as "fluoride ions") coordinate with the metal of a metal organic framework (MOF, also referred to as metal organic framework), so that the dye molecules The dye molecules are configured to be liberated from the metal-organic framework, and the dye molecules are configured to be able to absorb visible light. For this reason, it is possible to prepare a measurement sample by mixing the reagent of the present invention and sample water that may contain fluorine ions, and to measure the physical quantity correlated with the concentration of the dye molecules in the measurement sample using visible light. can. Moreover, by determining the correlation between this physical quantity and the fluorine ion concentration in advance, the fluorine ion concentration of the sample water can be determined based on the measured physical quantity.

FIG. 2 is a conceptual diagram showing the principle of detection of fluorine ion concentration in the present invention. 2A is a perspective view of the reagent 4 contained in the container 3, FIG. 2B is a perspective view of the container 3 filled with sample water 5, and FIG. 2C is a perspective view of the container 3 with a lid. 2 is a perspective view of a state after a measurement sample 6 is created by attaching and shaking the test sample 2. FIG. FIG. 3A is a perspective view after the measurement sample 6 is attached to the sample holding part 7a of the adapter 7, and FIG. 3B is a perspective view after the adapter 7 is attached with the lid 7d and the terminal 7b is inserted into the terminal insertion port of the information processing device 9. FIG. 1 is a configuration diagram of a fluorine ion concentration measuring device 1. FIG. It is a graph showing the relationship between fluorine ion concentration and physical quantity. Shows the state in which measurement data is superimposed and displayed on a map. 7A shows a secondary structural unit 4d, FIG. 7B shows a metal-organic structure 4a composed of secondary structural units 4d bonded to each other by an organic ligand 4c, and FIG. 7C shows a secondary structural unit 4d. A schematic representation is shown. FIGS. 8A to 8B show TGA measurement results for UiO-66 _ND and UiO-66 ₀₀ , respectively. 9A-9B show the TGA measurement results for UiO-66 ₀₆ and UiO-66 ₁₂ , respectively. The TGA measurement results for UiO-66 ₂₄ are shown. The number of defects per ₆ units of Zr calculated based on TGA measurement results is shown. 12A and 12B are electron micrographs of Al-BDC _ND and Al-BDC ₀₀ , respectively. FIG. 13A shows the XRD patterns of UiO-66 made by various methods, and FIG. 13B shows the XRD patterns of Al-BDC made by various methods. FIG. 14A shows the Abs ^F- , Abs ^MQ , and figure of merit of UiO-66 prepared by various methods, and FIG. 14B shows the Abs ^F- , Abs ^MQ , and figure of merit of Al-BDC prepared by various methods. show. 15A to 15B are graphs showing changes in fluorescence intensity over time, and FIGS. 15A and 15B show the results for UiO-66 ₀₀ and Al-BDC ₃₀ , respectively. 16A to 16B are graphs showing the relationship between fluorine ion concentration _and fluorescence intensity when various amounts of reagent 4 are used, and FIGS. 16A and 16B are graphs showing the relationship between fluorine ion concentration and fluorescence intensity, respectively The results for ₃₀ are shown. 17A to 17B are graphs showing the recovery rate of fluorescence intensity when various accompanying ions coexist, and FIGS. 17A and 17B show the results for UiO-66 ₀₀ and Al-BDC ₃₀ , respectively. show. 18A to 18B are graphs showing the difference in the recovery rate of fluorescence intensity in the presence and absence of a buffer when the accompanying ion is HCO ₃ ⁻ or HPO ₄ ²⁻ , and FIGS. 18A and 18B are Results for UiO-66 ₀₀ and Al-BDC ₃₀ are shown. 2 is a graph showing the relationship between fluorine ion concentration and orange channel output of AS7262 for UiO-66 ₀₀ and Al-BDC ₃₀ . An example of an image used for determining fluorine ion concentration by image analysis is shown. FIG. 21A is a graph showing the relationship between rhodamine B concentration and magenta intensity for two color filters 14 and 15 and five measurement samples 6. FIG. 21B is a graph showing the relationship between the concentration of rhodamine B and the magenta intensity, which was obtained by changing the spectrum of ambient light and the concentration of rhodamine B in measurement sample 6. FIG. 22A is a graph showing the relationship between fluorine ion concentration and absorbance at 523 nm for measurement sample 6 prepared using reagent A. FIG. 22B is a graph showing the relationship between fluorine ion concentration and magenta intensity for measurement sample 6 prepared using reagent A. FIG. 23A shows the particle size distribution of the alumina particles used in "10. Preparation of metal-organic structure 4a supported on carrier". FIG. 23B shows the particle size distribution of particles obtained by supporting the metal-organic structure 4a on the alumina particles of FIG. 23A.

Hereinafter, embodiments of the present invention will be described. Various features shown in the embodiments described below can be combined with each other. Further, the invention can be realized independently for each feature. "ppm" in the following description means "mg/L".

1. Fluorine Ion Concentration Measuring Method and Apparatus First, a fluorine ion concentration measuring method according to an embodiment of the present invention will be described using FIGS. 1 to 6. An apparatus capable of implementing this method will also be described. Although a specific example will be used to explain the present invention, it is also possible to implement the present invention by means other than the method and apparatus described here.

(1) Sample Preparation Step In the sample preparation step, first, as shown in FIG. 2A, a reagent 4 contained in a container 3 with a lid 2 is prepared. A mark 3a is attached to the container 3 to indicate the position at which the injection of sample water is stopped. As shown in FIG. 1, the reagent 4 includes a metal-organic structure 4a and a dye molecule 4b capable of absorbing visible light. The dye molecules 4b are coordinately bonded to the metal-organic framework 4a. Details of reagent 4 will be described later.

The amount of reagent 4 contained in container 3 is, for example, 0.1 to 10 mg, preferably 0.5 to 2 mg. In this embodiment, in addition to the small amount of reagent 4 required for measurement, the reagent 4 can be manufactured relatively inexpensively, so the cost required for the reagent 4 can be suppressed. Specifically, the amount of reagent 4 is, for example, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mg, and the It may be within a range between any two values.

Next, as shown in FIG. 2B, open the lid 2, inject the sample water 5 into the container 3, and stop the injection of the sample water 5 when the water surface of the sample water 5 reaches the position of the mark 3a. . This makes it easy to inject a certain amount of sample water 5. Note that a certain amount of sample water 5 may be injected by another means without providing the mark 3a.

The sample water 5 is water whose fluorine ion concentration is to be measured, and examples thereof include freshwater resources such as river water, lake water, ground water, or well water. In this embodiment, samples collected from rivers, lakes, groundwater, or well water are used as sample water as they are. According to this embodiment, since steps such as pretreatment of the sample water 5 are not necessary, the fluorine ion concentration can be measured at the site where the sample water 5 is collected.

The amount of sample water 5 used for measurement is, for example, 1 to 100 mL, preferably 10 to 50 mL, and specifically, for example, 1, 3, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 mL, and may be within a range between any two of the numerical values exemplified here. In the method of this embodiment, the fluorine ion concentration can be measured using such a small amount of sample water 5.

The sample water 5 may contain fluorine ions, and may not contain fluorine ions. The fluorine ion concentration of the sample water 5 is, for example, preferably 20 ppm or less, more preferably 15 ppm or less. In this case, the measurement accuracy of fluorine ion concentration becomes particularly high. This fluorine ion concentration is, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 ppm, and may be within a range between any two of the numerical values exemplified here. Note that even if the fluorine ion concentration in the sample water 5 exceeds 20 ppm, it is possible to qualitatively measure whether the fluorine ion concentration in the sample water 5 is higher than the standard value. The ion concentration is not particularly limited.

The sample water 5 may contain accompanying ions other than fluorine ions. The accompanying ions include Cl ⁻ , SO ₄ ²⁻ , Ca ²⁺ , Mg ²⁺ , HCO ₃ ⁻ , HPO ₄ ²⁻ and the like. If the concentration of these ions is too high, it may adversely affect the measurement accuracy of fluorine ions, so the concentration of each of these ions is preferably 100 ppm or less, and more preferably 50 ppm or less. HCO ₃ ⁻ , HPO ₄ ²⁻
Although these ions tend to affect measurement accuracy, the influence of these ions can be reduced by adjusting the pH using a buffer. The pH after addition of the buffer is, for example, preferably 8.0 or less, more preferably 7.5 or less, and even more preferably 7 or less. This pH is, for example, 2.0 to 8.0, and specifically, for example, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5. , 7, 7.5, and 8, and may be within the range between any two of the numerical values exemplified here or below any one thereof. As a buffer, for example, a tertiary tertiary material having a pH adjusting function within the above pH range and containing an N-substituent so large as to be sterically inaccessible to the formation of a complex with the metal cluster forming the metal-organic framework 4a. Amine-based ones are preferred; for example, a solution containing tris(hydroxymethyl)aminomethane and hydrochloric acid can be used. Other buffers include PIPES, PIPPS, PIBS, DEPP, DESPEN, MES, TEEN, Bis-Tris, lloADA, ACES, MOPSO, Bis-Tris Propane, BES, MOPS, TES, HEPES, and the like.

The concentration of the buffer is preferably set so that the buffer capacity (number of moles of added acid or base/change in pH) is 0.01 to 0.1. Specifically, the buffering capacity is, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10. Yes, it may be within the range between any two of the numerical values exemplified here.

Next, as shown in FIG. 2C, by closing the lid 2 and shaking the container 3, the reagent 4 and the sample water 5 are mixed to obtain a measurement sample 6. When the sample water 5 and the reagent 4 are mixed, the reagent 4 becomes a suspension dispersed in the sample water 5, and as shown in FIG. The dye molecules 4b are liberated from the metal-organic framework 4a.

The higher the fluorine ion concentration of the sample water 5, the greater the amount of free dye molecules 4b. Therefore, the fluorine ion concentration of the sample water 5 can be measured by measuring a physical quantity that correlates with the amount of free dye molecules 4b. It is possible. In addition, when the dye molecule 4b is in a free state than when it is coordinated to the metal-organic structure 4a, the transmitted light intensity of visible light is smaller, and the dye molecule 4b is excited by visible light and emitted. The intensity of the fluorescence emitted increases. As the transmitted light intensity decreases, the absorbance calculated by Equation 1 increases. Therefore, it becomes possible to determine the fluorine ion concentration of the sample water 5 based on the absorbance or fluorescence intensity.
(Formula 1) Absorbance = -log ₁₀ (I/I ₀ ) (where I is the transmitted light intensity and I ₀ is the incident light intensity)

The concentration of reagent 4 in measurement sample 6 is preferably 0.05 to 1 mg/mL, preferably 0.1 to 0.5 mg/mL. The lower the concentration, the higher the sensitivity, but the narrower the concentration range in which the physical quantity and the fluorine ion concentration have a linear relationship. Specifically, the concentration of the reagent 4 in the measurement sample 6 is, for example, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0. .8, 0.9, and 1.0 mg/mL, and may be within the range between any two of the numerical values exemplified here.

(2) Measurement process In the measurement process, first, as shown in FIG. 3A, the measurement sample 6 is placed in the sample holding section 7a of the adapter 7.

Next, as shown in FIG. 3B, the lid 7d is attached to the adapter 7, and the terminal 7b of the adapter 7 is inserted into the terminal insertion port (not shown) of the information processing device 9. Thereby, as shown in FIG. 4, the adapter 7 and the information processing device 9 are communicably connected through the communication units 7c and 9g. The information processing device 9 is preferably a portable terminal such as a smartphone, a tablet terminal, or a notebook PC. The adapter 7 and the information processing device 9 constitute a fluorine ion concentration measuring device 1.

As shown in FIG. 4, the information processing device 9 includes a display section 9a, a measurement control section 9b, a concentration determination section 9c, a positioning section 9d, a storage section 9e, a superimposition display section 9f, and a communication section 9g. have Various programs are stored in the storage unit 9e, and various functions necessary for the operation of the information processing device 9 are realized by the CPU provided in the information processing device 9 executing the various programs. The storage unit 9e also stores an application program for measuring fluorine ion concentration (hereinafter referred to as "measurement application"), and when the CPU executes this program, various functions necessary for measuring fluorine ion concentration are realized. be done.

The adapter 7 is provided with a measurement section 10 that can measure physical quantities correlated with the concentration of dye molecules in the measurement sample 6 using visible light. controls the measurement unit 10 to measure the above-mentioned physical quantities.

More specifically, as shown in FIG. 4, the measuring section 10 includes a light projecting section 10a such as an LED, and a light receiving section 10b, and irradiates the measurement sample 6 with visible light 12 from the light projecting section 10a. At the same time, in the light receiving section 10b, the intensity of the visible light 12 not absorbed by the measurement sample 6 or the fluorescence 13 emitted when dye molecules in the measurement sample 6 are excited by the visible light 12 is measured.

The measurement unit 10 is configured to be operable by being supplied with power from the information processing device 9. Therefore, since it is not necessary to provide a power source such as a battery to the adapter 7, the configuration of the adapter 7 is simplified and the cost of the adapter 7 is reduced. Furthermore, the visible light projecting section 10a and the light receiving section 10b are cheaper than those for ultraviolet light, which leads to a reduction in the cost of the adapter 7 in this respect. Furthermore, since visible light is safer than ultraviolet light, even if measuring light leaks from the adapter 7, the risk of exposing the user to danger is reduced.

The time from creating the measurement sample 6 to performing the measurement is preferably 120 seconds or more, more preferably 150 seconds or more, and even more preferably 200 seconds or more. If this time is too short, the release of the dye molecules 4b will be insufficient and measurement accuracy will decrease. Further, this time is preferably 1800 seconds or less, more preferably 1200 seconds or less, even more preferably 600 seconds or less, even more preferably 500 seconds or less, and even more preferably 400 seconds or less. If this time is too long, the measurement accuracy will decrease because the dye molecules 4b will re-adhere to the metal-organic structure 4a. Specifically, this time is, for example, 120, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 1200, 1800 seconds, and is between any two of the numerical values exemplified here. may be within the range of

(3) Concentration determination step In the concentration determination step, the fluorine ion concentration of the sample water 5 is determined based on the physical quantity. The storage unit 9e stores information indicating the correlation between the physical quantity measured by the measurement unit 10 and the fluorine ion concentration. Examples of this information include tables and mathematical formulas showing the above-mentioned correlations. The correlation is preferably a linear relationship. Upon receiving the physical quantity measured by the measuring section 10, the concentration determining section 9c determines the fluorine ion concentration of the sample water 5 based on the above correlation.

The above correlation can be determined using multiple types of test water whose fluoride ion concentrations are known and whose fluoride ion concentrations differ. By measuring the physical quantity for each test water using the method described above, the relationship between the physical quantity and the fluorine ion concentration can be obtained for each fluorine ion concentration. For example, as shown in the graph of FIG. 5, if the physical quantities obtained for test water having three fluorine ion concentrations c1, c2, and c3 are p1, p2, and p3, then the point determined by the fluorine ion concentration and the physical quantity When a1, a2, and a3 are aligned in a straight line, it can be said that there is a linear relationship between the physical quantities and the fluorine ion concentration within the ranges of physical quantities p1 to p3 and concentrations c1 to c3, and any physical quantity between physical quantities p1 to p3 The corresponding fluorine ion concentration can be determined. Even if the fluorine ion concentration and the physical quantity do not have a linear relationship, for example, an approximate expression showing the relationship between the fluorine ion concentration and the physical quantity is determined, and based on this approximate expression, the fluorine ion concentration corresponding to an arbitrary physical quantity is determined. be able to.

In one example, the measuring step and the concentration determining step may be performed by image analysis. In this case, in the measurement step, an image of the measurement sample 6 is photographed using an image sensor having a plurality of light receiving elements while the measurement sample 6 is irradiated with visible light, and in the concentration determination step, at least one of the images is The fluorine ion concentration of the sample water 5 can be determined based on the representative values obtained for the gradation values of the two color components. When the information processing device 9 has a camera, the image sensor of this camera can be used as the light receiving section 10b. In this case, since there is no need to separately provide the light receiving section 10b, it is possible to reduce the device cost.

An image captured using an image sensor includes tone values corresponding to outputs corresponding to the intensity of light received by each of the plurality of light receiving elements included in the image sensor. These gradation values are values that correlate with the concentration of dye molecules in the measurement sample 6, and also with the fluorine ion concentration of the sample water 5. Therefore, the fluorine ion concentration of the sample water 5 can be determined based on the representative value calculated from these gradation values.

The representative value may be any value that represents a plurality of gradation values, for example, an average value, but may also be a maximum value, minimum value, mode value, etc. Each pixel usually includes an R component, a G component, and a B component, and the calculation of the representative value can be performed using one, two, or three of these components. . For example, if a dye molecule 4b with high absorbance in the wavelength range of the G component is used, the gradation value of the G component changes more than other components depending on the concentration of the dye molecule 4b. It is preferable to calculate the representative value using only the gradation values.

By the way, the concentration may be determined qualitatively. For example, by preparing a reference sample and comparing the physical quantity measured for the reference sample with the physical quantity measured for the measurement sample 6, the fluorine ion concentration contained in the measurement sample 6 can be relatively determined. For example, if the fluoride ion concentration of the reference sample is at an acceptable upper limit, it is sufficient to know that the fluoride ion concentration of the measurement sample 6 is lower than the fluoride ion concentration of the reference sample; The fluorine ion concentration of the measurement sample 6 can be determined qualitatively, such that the fluorine ion concentration is lower than the fluorine ion concentration of the reference sample.

The reference sample may be an authentic reference sample prepared by mixing test water with a known fluorine ion concentration with reagent 4, or it may be a pseudo reference sample that has an absorption spectrum equivalent to that of the authentic reference sample. The pseudo reference sample may be liquid or solid, and is preferably solid from the viewpoint of ease of handling. Solid state pseudo reference samples include color filters. Color filters with various absorption spectra are commercially available, and by employing a color filter corresponding to a desired authentic reference sample as a pseudo reference sample, measurement sample 6 can be measured without preparing an authentic reference sample. Fluoride ion concentration can be determined.

For example, if the dye molecule 4b has a maximum absorption wavelength near 550 nm (e.g. Rhodamine B), a color filter having a maximum absorption wavelength near 550 nm can be employed as the pseudo reference sample.

Two reference samples corresponding to mutually different fluorine ion concentrations may be used. In this case, by comparing the physical quantities measured for the measurement sample 6 and the physical quantities measured for each of the two reference samples, the fluorine ion concentration contained in the measurement sample 6 is determined to be between the fluorine ion concentrations of the two reference samples. It is possible to determine whether the value is

When determining concentration using a reference sample, the visible light used for measurement may be environmental light such as natural light or illumination light. In this case, since there is no need to separately provide a light projecting section for use in measurement, it is possible to reduce the cost of the device. The spectrum (intensity for each wavelength) of environmental light may change, and when the spectrum of environmental light changes, the physical quantity measured for measurement sample 6 will also change, but the physical quantity measured for the reference sample will also change. Even if the environmental light changes, the fluorine ion concentration can be specified based on the physical quantity measured for the measurement sample 6.

When the visible light used for measurement is environmental light, the light receiving section 10b can be configured with an image sensor such as a CCD or CMOS, for example.

Even when the visible light is environmental light, the measurement step and concentration determination step can be performed by image analysis using the reference sample and measurement sample 6. In this case, in the measurement step, the reference sample corresponding to a specific fluorine ion concentration and the measurement sample 6 are both irradiated with the visible light, and an image sensor having a plurality of light receiving elements is used to irradiate the reference sample and the measurement sample 6. An image of the measurement sample is photographed, and in the concentration determination step, the fluorine content of the sample water 5 is determined based on the representative value obtained for the gradation value of at least one color component in the images of the reference sample and the measurement sample. Ion concentration can be determined.

As mentioned above, if a reference sample is used, the fluorine ion concentration can be determined even when the visible light is environmental light.

In one example, when the environmental light is light containing a green component and the dye molecules 4b can absorb the green component, an image of the measurement sample 6 and the reference sample in the container 3 is photographed, and the The fluorine ion concentration can be specified based on the representative value (for example, the average value of the gradation values) of the gradation values of the G component of each pixel. When the environmental light is white light, the measurement sample 6 and the reference sample are magenta (reddish-purple), which is a complementary color to green. The higher the concentration of the dye molecules 4b in the measurement sample 6, the more the green component in the ambient light is absorbed, the smaller the gradation value of the green component in the image, and the deeper the magenta color becomes. Therefore, the fluorine ion concentration of the measurement sample 6 is determined by comparing the colors of the images of the measurement sample 6 and the reference sample, and by calculating a representative value based on the gradation value of the G component in these images. be able to.

(4) Superimposed Display Step The positioning unit 9d of the information processing device 9 is capable of acquiring current position data at the time of the above measurement. The positioning unit 9d is, for example, a GPS receiver. The storage unit 9e stores the fluorine ion concentration determined by the concentration determination unit 9c and the current position data acquired by the positioning unit 9d in association with each other as measurement data. This makes it possible to compare the fluorine ion concentrations at each measurement point.

Furthermore, as shown in FIG. 6, the superimposition display section 9f can display the measurement data retrieved from the storage section 9e in a superimposed manner on the map. This makes it easy to intuitively understand the distribution of fluorine ion concentration. Furthermore, since it becomes easy to identify areas with low fluoride ion concentrations, it becomes easy to obtain safe water with low fluoride ion concentrations. Note that the storage unit 9e may be provided outside the information processing device 9. In this case, data can be exchanged with the externally provided storage section 9e by communication via the communication section 9g.

(5) Data sharing Obtained measurement data can be shared with others using Internet services such as email and SNS. This makes it easier to disseminate information about the availability of safe water.

2. Reagent for measuring fluorine ion concentration The details of reagent 4 will be explained. As described above, the reagent 4 includes a metal organic structure 4a and a dye molecule 4b that can absorb visible light.

It is preferable that the dye molecule 4b has a carboxyl group. In this case, the dye molecules 4b are likely to coordinately bond to the metal-organic structure 4a. The number of carboxyl groups contained in the dye molecule 4b is preferably one. When the dye molecule 4b has a plurality of carboxyl groups, it becomes difficult for the dye molecule 4b to be released from the metal-organic structure 4a.

The dye molecules 4b are preferably capable of emitting fluorescence when excited by visible light. In this case, it becomes possible to measure the concentration of fluorine ions by measuring the intensity of fluorescence.

The dye molecule 4b has a value of [absorbance in a free state]/[absorbance in a state arranged in a metal-organic structure 4a] as A, and a value of [fluorescence intensity in a free state]/[a metal-organic structure]. [Fluorescence intensity when placed on the body 4a] is B, A and B are each larger than 1, preferably 2 or more, more preferably 5 or more, and even more preferably 10 or more. In this case, the measurement accuracy of the fluorine ion concentration based on the physical quantity correlated to the release of the dye molecules 4b is improved.

The dye molecule 4b preferably has a maximum absorption wavelength of 450 to 650 nm, more preferably 500 to 600 nm. Further, the absorption fluorescence wavelength of the dye molecule 4b is preferably 480 to 680 nm, more preferably 530 to 630 nm.

The dye molecule 4b is preferably a xanthene dye molecule having a carboxyl group. A xanthene dye molecule is a dye molecule having a xanthene skeleton, such as rose bengal, erythrosin, eosin Y, fluorescein, rhodamine, or calcein. Rhodamine is preferably Rhodamine B. The dye molecule 4b may be a dye molecule other than the xanthene dye molecule, for example, an azo dye (methyl red, alizarin yellow R), a phthalein dye (phenolphthalein, o-cresol phthalein, thymol phthalein). It may also be a dye molecule having a carboxyl group such as. Such dye molecules 4b can be purchased or manufactured at relatively low cost, and thus contribute to reducing the manufacturing cost of the reagent 4.

As shown in FIGS. 7A to 7C, the metal-organic structure 4a is a structure having a periodic structure formed by periodic coordination bonds between metal atoms M and organic ligands 4c. The metal-organic structure 4a is preferably one in which at least a portion of the dye molecules 4b coordinately bonded to the metal-organic structure 4a can be replaced with fluorine ions. In this case, the dye molecules 4b are rapidly liberated in the presence of fluorine ions and can be detected. The metal-organic structure 4a is porous, and water can quickly penetrate into the metal-organic structure 4a. Therefore, the substitution reaction between the dye molecules 4b and fluorine ions occurs quickly, so that the fluorine ion concentration can be measured quickly.

The metal of the metal-organic structure 4a is not particularly limited, but iron, zirconium, aluminum, or a lanthanoid rare earth metal element is preferable. In this case, the metal-organic framework tends to become stable in water. Lanthanoid rare earth metal elements include terbium, europium, yttrium, cerium, dysprosium, neodymium, erbium, thulium, and ytterbium.

The organic ligand 4c includes a polydentate organic ligand. The polydentate organic ligand preferably has a plurality of bonding sites, and preferably has a plurality of carboxyl groups. The polydentate organic ligand is preferably a bidentate organic ligand, more preferably has a terephthalic acid skeleton, and even more preferably terephthalic acid.

The metal-organic structure 4a preferably has a secondary structural unit 4d composed of a metal polynuclear cluster, as shown in FIG. 7A, and as shown in FIG. 7B, the secondary structural units 4d are organic It is preferable that a periodic structure is formed by bonding through the ligands 4c, and it is preferable that the secondary structural units 4d are arranged so as to form a face-centered cubic lattice. As shown in FIG. 7A, when the secondary structural unit 4d is represented by a polyhedron 4d1 and the organic ligand 4c is represented by a band 4c1, the metal-organic structure 4a in FIG. 7B can be schematically expressed as shown in FIG. 7C. can be expressed.

The metal polynuclear cluster preferably has a structure in which a plurality of metal atoms M are bonded to each other via oxygen atoms. The metal polynuclear cluster is preferably a metal hexanuclear cluster. In this case, a structure in which six metal atoms M are arranged at the vertices of an octahedron is preferable. In FIGS. 7A to 7C, when the metal atom M is zirconium, the metal-organic structure 4a becomes a structure called UiO-66.

As the metal-organic structure 4a that can be used in this embodiment, an MOF (for example, MOF76 (LnBTC, Ln:Y, lanthanide), MOF199) having a unique open metal site (hereinafter referred to as "OMP"), or a synthetically modified (synthetic modulation) such as UiO-66, UiO-67, isoreticular series of UiO-66, MIL-53, MIL-67, MIL-101, etc. It will be done. Such a metal-organic structure 4a can be purchased or manufactured at relatively low cost, and thus contributes to reducing the manufacturing cost of the reagent 4. The open metal site means a binding site on a metal atom to which the dye molecule 4b can coordinately bond. Note that ZrOCl ₂ or ZrCl ₄ can be used to prepare the iso-reticular series of UiO-66.

By the way, the metal-organic structure 4a is a crystalline structure, and there is a chemical interaction between the carboxyl group of the dye molecule 4b and the metal cluster of the metal-organic structure 4a, which constitutes a reagent. The dye molecules 4b are included in the crystal lattice of the metal-organic structure 4a. On the other hand, in the metal-organic structure 4a, the number of binding sites to which the dye molecules 4b can coordinately bond may be insufficient. In such a case, the coordination bond of the dye molecules 4b can be promoted by intentionally introducing defects into the metal-organic structure 4a.

Examples of methods for introducing defects include increasing the specific surface area of the metal-organic structure 4a and introducing monodentate organic ligands.

Since the crystal structure collapses on the surface of the metal-organic structure 4a, the larger the specific surface area, the larger the area of the surface where the crystal structure collapses, increasing the number of binding sites where the dye molecules 4b can coordinate. In order to increase the specific surface area, the average particle diameter of the metal-organic structure 4a may be decreased. A method for reducing the average particle diameter of the metal-organic structure 4a includes increasing the rate of crystallization of the metal-organic structure 4a.

The monodentate organic ligand preferably has one bonding site and one carboxyl group. As the monodentate organic ligand, a monovalent aliphatic carboxylic acid is preferable, and examples include acetic acid (eg, trifluoroacetic acid) in which the hydrogen atom of the methyl group may be substituted with a halogen, and formic acid. A binding site for the dye molecule 4b can be created by placing a monodentate organic ligand at a site where a polydentate organic ligand should be placed in the crystal structure of the metal-organic structure 4a.

When the metal-organic framework 4a is UiO-66, the number of defects per Zr hexanuclear cluster (hereinafter referred to as "Zr ₆ unit") is preferably 0.2 or more, and more preferably 0.5 or more. preferable. The number of defects per ₆ units of Zr is, for example, 0.2 to 2.0, and specifically, for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7. , 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2 .0, and may be in the range between any two of the numerical values exemplified here.

Incidentally, the metal-organic structure 4a may not easily settle in the measurement sample 6, and in this case, the measurement sample 6 becomes a suspension. When the measurement sample 6 becomes a suspension, the accuracy of measurement may be reduced due to the floating metal-organic structures 4a. For this reason, it is preferable that the metal-organic structure 4a is capable of settling quickly. In order to increase the sedimentation rate of the metal-organic structure 4a, the metal-organic structure 4a is preferably supported on carrier particles. These carrier particles have a higher sedimentation rate than the metal-organic structure 4a. By supporting the metal-organic structure 4a on the carrier particles, the sedimentation rate of the metal-organic structure 4a can be increased.

When the sedimentation rate of the metal-organic structure 4a becomes high, a substantially transparent supernatant can be obtained by simply leaving the suspension for a while without centrifugation, and this supernatant can be used to Since it is possible to measure a physical quantity that correlates with the concentration of dye molecules 4b in the measurement sample 6, measurement accuracy can be improved. The physical quantity to be measured is preferably the transmitted light intensity of visible light irradiated onto the measurement sample 6. Measurement of the transmitted light intensity of visible light is easily affected by suspended particles, so if the measurement sample 6 is a suspension, highly accurate measurement is difficult. By obtaining a substantially transparent supernatant liquid, it becomes possible to measure the transmitted light intensity of visible light with high accuracy.

In addition, since the dye molecules 4b non-specifically adsorbed to the metal-organic structure 4a cause a decrease in measurement accuracy, it is preferable to remove them as much as possible. As shown in ``Coordination of molecule 4b'', it is necessary to repeat the process of adding a solvent (e.g. ethanol) → shaking → centrifuging → removing the supernatant liquid many times, and repeating this process requires a large amount of solvent. This is necessary and takes a very long time and a lot of effort. If the metal-organic structure 4a is difficult to sediment, such a process is unavoidable, but by supporting the metal-organic structure 4a on a carrier and increasing the sedimentation rate, it is possible to do so without centrifugation. The metal-organic structure 4a can now be precipitated, and the above process can be simplified.

Further, when the metal-organic structure 4a is supported on a carrier, the non-specifically adsorbed dye molecules 4b can be removed using a Soxhlet extractor. In a Soxhlet extractor, a predetermined amount of solvent is refluxed and used repeatedly, so it is possible to dramatically reduce the amount of solvent used, and because it requires less manual work, it can also dramatically reduce labor. .

Any carrier particles that can support the metal-organic structure 4a and increase the sedimentation rate of the metal-organic structure 4a can be used as the carrier particles. The carrier particles are preferably composed of an inorganic oxide from the viewpoint of specific gravity and ease of handling. Examples of inorganic oxides include alumina and silica. The inorganic oxide preferably has a particle size (45 to 150 μm) of 90% or more. The larger the particle size of the inorganic oxide, the higher the sedimentation rate. The average particle size of the inorganic oxide is, for example, 20 to 500 μm, specifically, for example, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150. , 160, 170, 180, 190, 200, 250, 300, 350, 400, 450, 500 μm, and the range may be between any two of the numerical values exemplified here. The coefficient of variation of particle diameter (=standard deviation/average particle diameter) is, for example, 80% or less, preferably 50% or less, and more preferably 30% or less. This variation coefficient is, for example, 0 to 80%, and specifically, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 , 80%, and may be in the range between any two of the numerical values exemplified here. The average particle diameter is determined by taking a SEM image of the inorganic oxide particles at a magnification of 80 times, measuring the particle diameters of 30 or more particles in the obtained SEM image, and taking the arithmetic average of the particle diameters. It can be carried out.

When the average particle size of the inorganic oxide is D1 and the average particle size D2 of the particles obtained by supporting the metal-organic structure 4a on the inorganic oxide, D2/D1 is, for example, 1.5 or less, and 1 .2 or less is more preferable. This value is, for example, 1 to 1.5, and specifically, for example, 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1. 07, 1.08, 1.09, 1.1, 1.2, 1.3, 1.4, 1.5, and in the range between any two of the numerical values exemplified here or below any one. There may be.

The metal-organic structure 4a can be supported on the carrier particles by mixing and stirring the metal-organic structure 4a and the carrier particles. The dye molecules 4b may be coordinated to the metal-organic structure 4a when the metal-organic structure 4a is supported on the carrier particles, and the dye molecules 4b may be coordinated with the metal-organic structure 4a before or after the metal-organic structure 4a is supported on the carrier particles. It may be coordinated to

1. Preparation of metal organic framework 4a 1-1. UiO-66
UiO-66 was prepared by the method shown below. First, ZrOCl _2.8H ₂ O, terephthalic acid (BDC) and trifluoroacetic acid (TFA) were dissolved in dimethylformamide (DMF) at room temperature in an ultrasonic bath and heated to 120 °C in a glass bottle for 72 hours. . Samples were isolated by centrifugation and washed three times with DMF for 3 hours at 70°C, once with DMF and twice with ethanol at 60°C overnight at the same temperature. Samples were dried at 80°C. The molar ratios and amounts used for sample preparation are shown in Table 1.

A defect-free sample, UiO-66 _ND , was prepared by the method shown below. First, 3.781 g of ZrOCl ₂ (16.22 mmol), 2.865 ml of 35% HCl (32.45 mmol), 5.391 g of BDC (32.45 mmol), and 97.40 ml of N,N'-dimethylformamide (1258 mmol) were mixed. The resulting mixture was stirred with gentle heating (approximately 70° C.) until complete dissolution. Once all samples were dissolved, the solution was transferred to a Teflon liner and transferred to an oven preheated to 220°C. After 24 hours of reaction, the solids were collected by centrifugation.

-TGA measurement The obtained sample was subjected to thermogravimetric measurement (TGA measurement). This measurement was performed using Seiko Instruments EXSTAR TG/DTA6200 under nitrogen gas flow at a scan rate of 5° C./min up to 850° C. α-alumina was used as a standard. For each UiO-66 sample, 2 mg of sample was weighed on a microbalance and placed in an open alumina pan for measurements. The results are shown in FIGS. 8 to 10.

- Defect analysis From the results of TGA measurement, the number of defects per ₆ units of Zr in the UiO-66 cell was calculated. The results are shown in FIG. The number of defects was calculated by the method described in the supplementary information of Non-Patent Document 1.

As shown in FIG. 11, in the case of UiO-66 _NDs , no noticeable defects were observed, and the number of ligands was 6 per ₆ units of Zr. Although UiO-66 ₀₀ did not contain TFA, it was composed of finer particles than UiO-66 _NDs , so it had more defects than UiO-66 _NDs . In addition, in the samples to which TFA, which is a monodentate organic ligand, was added (UiO-66 ₀₆ , UiO-66 ₁₂ , UiO-66 ₂₄ ), the number of defects increased as the amount of TFA added increased, and Zr ₆ The number of ligands per unit was reduced. Under the present test conditions, the maximum number of defects was reached at TFA/Zr=24.

1-2. Al-BDC
Al-BDC samples were prepared by the method shown below. First, AlCl ₃ .9H ₂ O and BDC were dissolved in DMF for 60 minutes using an ultrasonic bath. After completely dissolving the metal and ligand according to Table 2, formic acid was added. The glass reactor was then maintained at 120°C for 24 hours. Samples were isolated by centrifugation and washed with DMF for 3 hours at 70°C, overnight with DMF at 70°C, 3 hours at room temperature with butanone, and again overnight with butanone. Samples were dried at 80°C.

The defect-free sample Al-BDC _ND was prepared by hydrothermal synthesis method by mixing _Al2O3 and _BDC in 60 mL deionized water, transferring it to a Teflon-covered hydrothermal reactor, and adding 200 mL under self-generating pressure. It was kept at ℃ for 72 hours. The resulting powder was washed with DMF at 130° C. for 4 hours and overnight, and the procedure was repeated three times using EtOH at room temperature. Samples were dried at 80°C.

Electron micrographs of Al-BDC _ND and Al-BDC ₀₀ are shown in FIG. The Al-BDC _ND shown in FIG. 12A was a prismatic crystal with sharp surfaces. On the other hand, the crystals of Al-BDC ₀₀ were more rounded and aggregated, and the particle size was more uniform.

2. Coordination of Dye Molecule 4b A sample of metal-organic framework 4a was dispersed in a saturated ethanol solution of Rhodamine B in an ultrasonic bath for 20 minutes and shaken overnight. The solid was centrifuged, dried at 80°C, powdered and kept at 140°C for 60 hours. The samples were dispersed in ethanol with the help of an ultrasound bath, shaken for at least 6 hours, and centrifuged. This process was repeated until the absorbance of the supernatant solution became constant, which was usually achieved after 8 cycles.

3. X-ray Diffraction Samples of the metal-organic framework 4a before and after the coordination of the dye molecules 4b were analyzed by X-ray diffraction (XRD) in the Bragg-Brentano configuration of the ADD model. The results are shown in FIG. In FIG. 13, the dotted line shows the pattern before the dye molecule 4b is coordinated, and the solid line shows the pattern after the dye molecule 4b is coordinated.

For UiO-66, the peak broadened as the amount of trifluoroacetic acid (TFA) decreased. This indicates a decrease in particle size. Moreover, the XRD pattern did not change before and after coordination of the dye molecule 4b.

In the samples prepared under solvothermal conditions (Al-BDCx, x=0, 30, 100), the MIL-53-it phase was dominant when the dye molecule 4b was not coordinated. When dye molecule 4b was placed on this, a MIL-53-ht phase was observed together with a MIL-53-it phase. In addition, in the case of the sample Al-BDC _ND obtained under hydrothermal conditions, a mixture of the MIL-53-it phase and the MIL-53-ht phase was observed, and when the dye molecule 4b was placed, the MIL-53-ht phase The proportion of

4. Optimization of synthesis conditions In order to evaluate the background signal, nonspecific adsorption, total adsorption, and maximum absorbance, a suspension of the metal-organic framework 4a (hereinafter referred to as “MOF suspension”) coordinated with the dye molecule 4b was prepared. ) (10 mg/mL) was prepared and dispersed for 60 minutes using ultrasonic bath assistance. Non-specific adsorption was evaluated by adding 50 μL of MOF suspension to 5 mL of deionized water. Total adsorption was evaluated using a solution with a fluoride ion concentration of 1000 ppm.

All MOF suspensions were shaken on an orbital shaker for 90 min, centrifuged at 6000 RPM for 3 min, and the supernatants were measured at 523 nm (Ocean Optics Flame Uv-Vis spectrometer). The performance of the solids was evaluated using the figure of merit (Abs ^F --Abs ^MQ )/Abs ^MQ . Here, Abs ^MQ is the absorbance of a solution obtained using deionized water, and Abs ^F- is the absorbance obtained using a solution with a fluorine ion concentration of 1000 ppm.

Abs ^F- , Abs ^MQ , and figure of merit were determined for each sample. The results are shown in FIGS. 14A and 14B. As shown in these figures, for UiO-66, UiO-66 ₀₀ had the highest figure of merit, and for Al-BDC, Al-BDC ₃₀ had the highest figure of merit.

The figure of merit is preferably 2 or more, more preferably 5 or more, and even more preferably 10 or more. The figure of merit is, for example, 2 to 50, specifically, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 30, 40, 50, and may be within a range between any two of the numerical values exemplified here or more than any one.

5. Reaction Rate The reaction rate of the reaction for liberating the dye molecule 4b from the metal-organic structure 4a to which the dye molecule 4b was coordinated was measured. Reaction rates were measured on an Ocean Optics Flame Uv-Vis spectrometer using a commercially available green LED for bottom illumination at 90° to the detector. The metal-organic framework 4a to which the dye molecules 4b were coordinated was kept in suspension using a magnetic stirrer and a 3 mm stirring bar.

The results obtained for UiO-66 ₀₀ and Al-BDC ₃₀ are shown in FIG. UiO- ₆₆₀₀ has a faster signal rise than Al-BDC ₃₀ , and the signal is higher at the same mass. The signal strength reached its maximum at about 200 seconds in both cases, and then gradually decreased. It is believed that the attenuation is due to the dye molecules 4b reattaching to the metal-organic structure 4a.

6. Calibration Curve A fluoride ion solution with a fluoride ion concentration of 1000 ppm was diluted with double deionized water to create a standard solution with a fluoride ion concentration in the range of 0 to 20 ppm. A calibration curve was created using 10 mg/mL MOF suspension and 3 mL of standard solution. Measurements were performed in fluorescence mode using a laboratory device as described below. The standardized time of signal sampling was 1500 seconds for Al-BDC and 200 seconds for UiO-66. The obtained results are shown in FIG. 16. For both UiO-66 ₀₀ and Al-BDC ₃₀ , as the amount of MOF suspension used increased, the sensitivity decreased and the concentration range in which the calibration curve became linear expanded.

7. Influence of interference of accompanying ions. In order to verify the specificity of the analytical method developed using the metal-organic framework 4a on which the dye molecule 4b is placed, we investigated it in the presence of accompanying ions commonly found in natural waters. A signal recovery test was conducted using a 5 ppm fluoride ion solution. UiO- ₆₆₀₀ and Al-BDC ₃₀ were used as the metal-organic structure 4a.

For the interference of accompanying ions, a 5 ppm fluoride ion solution containing one of Cl ⁻ , SO ₄ ²⁻ , Ca ²⁺ , Mg ²⁺ , HCO ₃ ⁻ , and HPO ₄ ²⁻ at a concentration ranging from 5 to 100 ppm was used. I tested it. Measurements were performed in fluorescence mode using the same laboratory device used for the calibration curve. For HCO ₃ ⁻ , HPO ₄ ²⁻ , a buffer using TRIS/HCl 0.1M pH=7.5 was also tested. A 0.1 M buffer was prepared by dissolving 12.1 g of tris(hydroxymethyl)aminomethane (PA, Wako, Japan) in 80 mL of double deionized water. Using a pH meter, the pH was adjusted to 7.5 using HCl(c) (36.5-38.0%, Wako) and the final volume was adjusted. An appropriate amount of this buffer was then added to the solution containing the satellite ions and fluoride ions to give a final buffer concentration of 0.1M.

The test results are shown in FIGS. 17 and 18. The six bar graphs for each accompanying ion concentration in FIG. 17 show the results for Cl ⁻ , SO ₄ ²⁻ , Ca ²⁺ , Mg ²⁺ , HCO ₃ ⁻ , and HPO ₄ ²⁻ in order from the left. Among these, the results for HCO ₃ ⁻ and HPO ₄ ²⁻ are obtained with the addition of buffer. The four bar graphs for each accompanying ion concentration in FIG. 18 are, from left to right, HCO ₃ ⁻ (without buffer), HPO ₄ ²⁻ (without buffer), HCO ₃ ⁻ (with buffer), and HPO ₄ ²⁻ The results for (with buffer) are shown.

For UiO- ₆₆₀₀ , all ions with concentrations below 100 ppm showed no significant difference in recovery with the pure fluoride ion solution, as shown in Figure 17A. The main interferences occurred with carbonate and phosphate (related species at natural pH) above 10 ppm, as shown in Figure 18A; By doing so, I was able to overcome it.

On the other hand, Al-BDC ₃₀ showed complete recovery of the fluorine ion signal even at 100 ppm of concomitant ions, as shown in FIG. 17B. The main interference occurred at concentrations of carbonate and phosphate (related species at natural pH) above 10 ppm, as shown in Figure 18B. However, these interferences could be overcome by using a buffer, as shown in Figure 18B. Thus, no significant difference in recovery was observed under the optimized conditions.

The effect of improving the recovery rate by using a buffer will be explained. When HCO ₃ ⁻ or HPO ₄ ²⁻ is present in a sample at high concentrations, the pH of the sample changes toward basic pH. This pH change may change the solubility of the metal-organic structure 4a and the charge of the released dye molecules 4b, leading to a change in the emission spectrum. By using a buffer, the pH of the sample is suppressed by changing, resulting in improved recovery.

8. Lab Device The device for fluorescence measurements was constructed using an AS7262 6-channel detector, a commercially available green LED (530 nm), and an Arduino UNO with an SD card shield. The device for field applications was built using the same detectors and LEDs and using SeeduinoXIAO and SeeedunoXIAO expansion boards. These members are relatively inexpensive, and according to this embodiment, it is possible to construct the device at low cost.

The orange channel of AS7262 outputs light intensity in the range of center wavelength 600 nm and FWHM 40 nm. A calibration curve was created using the output from this channel. The results are shown in FIG. The three points are lined up on a straight line, and it can be seen that the output from the channel exhibits linearity with respect to the fluorine ion concentration.

9. Determination of fluorine ion concentration by image analysis Figure 20 shows images taken under natural light. Although this image is actually a color image, it is displayed here in black and white for convenience. In FIG. 20, a sample holder 16 holds two commercially available color filters (pseudo reference samples) 14 and 15 and five measurement samples 6. The background of the sample holder 16 is a blue sky with scattered white clouds. The image 14a of the color filter 14 is a light magenta color, and the image 15a of the color filter 15 is a dark magenta color. In the five measurement samples 6, the concentration of rhodamine B gradually increases from left to right, and the magenta color of the image 6a of the measurement samples 6 gradually increases from left to right. Therefore, the depth of magenta color corresponds to the concentration of Rhodamine B. Rhodamine B concentration can be related to fluoride ion concentration. The image file in FIG. 20 includes R, G, and B gradation values of each pixel included in images 14a, 15a, and 6a, and among these, the G gradation value changes depending on the concentration of rhodamine B. is large, the average value of the G gradation values was taken as the average intensity of the magenta color of each sample (hereinafter referred to as magenta intensity). This image analysis was performed using Matlab.

FIG. 21A is a graph showing the relationship between rhodamine B concentration and magenta intensity for two color filters 14 and 15 and five measurement samples 6. Looking at the plots for the five measurement samples 6, it can be seen that the concentration of Rhodamine B and the magenta intensity change linearly. This average intensity changes in response to changes in the spectrum of environmental light, and cannot be directly converted into a fluorine ion concentration. However, the two color filters 14 and 15 are each associated with a known fluorine ion concentration, and the magenta intensity of each measurement sample 6 is determined by using the relationship between the magenta intensity and the fluorine ion concentration for these filters. can be converted to fluorine ion concentration.

FIG. 21B is a graph showing the relationship between rhodamine B concentration and magenta intensity for two color filters 14 and 15 and five measurement samples 6, and the rhodamine B concentration of five measurement samples 6 is different from that in FIG. 21A. It's different. The color filters 14 and 15 are the same as in FIG. 21A, but the spectrum of the ambient light is different from that in FIG. 21A, so the magenta intensity is different. In FIG. 21B, the range of rhodamine B concentration is wider than in FIG. 21A, but similarly to FIG. 21A, the rhodamine B concentration and magenta intensity change linearly.

When the concentration of Rhodamine B becomes higher, the concentration of Rhodamine B and the magenta intensity may not have a linear relationship. When measuring in such a concentration range, it is preferable to shorten the optical path length. In other words, the linear range can be changed by changing the optical path length. For example, if the inner surface shape of the container 3 is a shape (e.g. rectangular parallelepiped) that changes depending on the rotation (e.g. 90 degree rotation) of the container 3, the optical path length can be changed by rotating the container 3. . In this case, two types of sensitivity can be achieved with one device.

In this example, the maximum absorption wavelength of rhodamine B is approximately 550 nm, so the G component in the image was used for image analysis, but the component used for image analysis was determined according to the absorption spectrum of the dye molecule 4b used. It can be changed as appropriate. For example, if the dye molecule 4b used has a maximum absorption wavelength in the red region, it is preferable to use the R component in the image for image analysis.

10. Preparation of metal-organic framework 4a supported on carrier ZrOCl _2.8H ₂ O (1.19 g, 3.7 mmol) and terephthalic acid (BDC) (0.615 g, 3.7 mmol) were placed in an ultrasonic bath. It was dissolved in dimethylformamide (DMF) (100 ml) at room temperature and heated to 120° C. for 72 hours in a glass bottle to form a gel. The resulting gel was homogenized by ultrasonication and washed with DMF using solvent exchange twice at 100° C. for 3 hours and twice at room temperature for 3 hours. The sample was also homogenized with an ultrasonic homogenizer during washing.

Next, 11.2 g of the homogenized sample and 2.2 g of alumina (Al ₂ O ₃ ) (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., activated alumina, particle size (45-150 μm) of 90% or more) were mixed. To this was added 20 ml of a saturated Rhodamine B solution and mechanically homogenized using a laboratory glass stir bar. The resulting mixture was dried with constant stirring using a laboratory glass stir bar and dried using a hot plate to obtain the composite. After drying this complex overnight at 140°C, excess rhodamine B was removed using a Soxhlet extractor, and reagent A in which rhodamine B was coordinated to the metal-organic framework 4a supported on alumina was obtained. Obtained.

11. Creation of a calibration curve for reagent A A fluoride ion solution with a fluoride ion concentration of 1000 ppm was diluted with double deionized water to create a standard solution with a fluorine ion concentration in the range of 0 to 15 ppm. A plastic conical tube with a cap was then used to weigh out 10 mg of Reagent A using an analytical balance. Next, 5 mL of the standard solution was added to the plastic tube containing Reagent A, the lid was closed, and the tube was stirred for 1 to 5 minutes at 100 rpm using a rotary shaker. Reagent A was then decanted by gravity, and the supernatant was collected using a disposable plastic pipette (v: 3 mL) and placed in a cuvette with an optical path length of 10 mm. Measurements were then performed on this solution using a UV-VIS spectrometer in absorbance mode at wavelength = 525 nm. Next, absorbance values were recorded and a calibration curve was created. The results are shown in FIG. 22A.

In addition, for the supernatant liquid collected in the same manner, image analysis was performed in the same manner as in "9. Determination of fluorine ion concentration by image analysis" to calculate magenta intensity. The results are shown in FIG. 22B.

In both FIGS. 22A and 22B, it can be seen that the absorbance or magenta intensity has a linear relationship with the fluorine ion concentration. This result shows that the accuracy of determining fluorine ion concentration by image analysis is almost equivalent to the accuracy of determining fluorine ion concentration using a spectrometer.

12. Measurement of particle diameter Using SEM images of the alumina particles used in "10. Preparation of metal-organic structure 4a supported on carrier" and particles obtained by supporting metal-organic structure 4a on these alumina particles. The particle size was measured. This particle diameter measurement was performed on a large number of particles in a SEM image obtained at a magnification of 80 times. The resulting particle size distribution is shown in FIG. FIG. 23A shows the results obtained for alumina particles (Al ₂ O ₃ ), and FIG. 23B shows the results obtained for alumina particles (Al ₂ O ₃ +MOF) supporting the metal-organic framework 4a. The alumina particles had an average particle diameter of 102 μm, a standard deviation of 20 μm, and the number of measured particles was 71. The alumina particles supporting the metal-organic structure 4a had an average particle diameter of 103 μm, a standard deviation of 32 μm, and the number of measured particles was 77. This result shows that the particle diameter of the alumina particles hardly changes due to the support of the metal-organic structure 4a. This also indicates that the particle size of the metal-organic structure 4a is much smaller than the particle size of the alumina particles.

1: Fluorine ion concentration measuring device, 2: Lid, 3: Container, 3a: Mark, 4: Reagent, 4a: Metal-organic structure, 4b: Dye molecule, 4c: Organic ligand, 4c1: Band, 4d: Two Next structural unit, 4d1: polyhedron, 5: sample water, 6: measurement sample, 6a: image, 7: adapter, 7a: sample holding section, 7b: terminal, 7: communication section, 7d: lid, 9: information processing device , 9a: display section, 9b: measurement control section, 9c: concentration determination section, 9d: positioning section, 9e: storage section, 9f: superimposition display section, 9g: communication section, 10: measurement section, 10a: light projection section, 10b: Light receiving section, 12: Visible light, 13: Fluorescence, 14, 15: Color filter, 14a, 15a: Image

Claims

A reagent for measuring fluorine ion concentration, comprising a metal-organic structure and a dye molecule capable of absorbing visible light,
the dye molecule is coordinately bonded to the metal-organic framework;
When the reagent is mixed with sample water that may contain fluorine ions, the fluorine ions are coordinated to the metal of the metal-organic structure, and the dye molecules are liberated from the metal-organic structure. A reagent composed of:
The reagent according to claim 1,
The dye molecule has a carboxyl group.
The reagent according to claim 1,
The dye molecule is capable of emitting fluorescence upon being excited by the visible light.
The reagent according to claim 1,
The reagent, wherein the dye molecule is a xanthene dye molecule, an azo dye, or a phthalein dye having a carboxyl group.
5. The reagent according to claim 4,
The dye molecule is the xanthene dye molecule,
The reagent, wherein the xanthene dye molecule is rose bengal, erythrosin, eosin Y, fluorescein, rhodamine, or calcein.
The reagent according to claim 1,
The metal of the metal-organic framework includes iron, zirconium, aluminum, yttrium, or a lanthanoid rare earth metal element.
The reagent according to claim 1,
The metal-organic framework is a reagent having a periodic structure in which secondary structural units constituted by metal polynuclear clusters are bonded to each other by polydentate organic ligands.
8. The reagent according to claim 7,
The reagent, wherein the metal polynuclear cluster is a metal hexanuclear cluster.
The reagent according to claim 1,
The reagent, wherein the metal-organic framework is MOF76, MOF199, UiO-66, UiO-67, isoreticular series of UiO-66, MIL-53, MIL-67, or MIL-101.
The reagent according to claim 1,
A reagent, wherein the metal-organic framework is supported on carrier particles.
The reagent according to claim 10,
The reagent, wherein the carrier particles are composed of an inorganic oxide.
12. The reagent according to claim 11,
A reagent in which D2/D1 is 1.5 or less, where D1 is the average particle diameter of the inorganic oxide and D2 is the average particle diameter of particles obtained by supporting the metal-organic structure on the inorganic oxide.
A method for measuring fluorine ion concentration, comprising a sample preparation step, a measurement step, and a concentration determination step,
In the sample preparation, a measurement sample is prepared by mixing the reagent according to any one of claims 1 to 12 and sample water that may contain fluorine ions,
In the measurement step, a physical quantity correlated with the concentration of the dye molecules in the measurement sample is measured using visible light,
In the concentration determining step, the fluorine ion concentration of the sample water is determined based on the physical quantity.
14. The method according to claim 13,
The method, wherein the fluorine ion concentration in the sample water is 20 ppm or less.
14. The method according to claim 13,
The method, wherein the concentration of the reagent in the measurement sample is 0.05 to 1 mg/mL.
14. The method according to claim 13,
The method, wherein the physical quantity is the transmitted light intensity of the visible light or the intensity of fluorescence emitted when the dye molecules are excited by the visible light.
14. The method according to claim 13,
The metal organic framework is supported on carrier particles,
In the measurement step, an image of the measurement sample is taken using an image sensor having a plurality of light receiving elements while the measurement sample is irradiated with visible light;
In the concentration determining step, the fluorine ion concentration of the sample water is determined based on a representative value obtained for the gradation value of at least one color component in the image.
A fluorine ion concentration measuring device comprising a sample holding section, a measuring section, and a concentration determining section,
The sample holding unit holds a measurement sample prepared by mixing the reagent according to any one of claims 1 to 12 and sample water that may contain fluorine ions,
The measurement unit measures a physical quantity correlated with the concentration of the dye molecule in the measurement sample using visible light,
The concentration determination unit is a device that determines the fluorine ion concentration of the sample water based on the physical quantity.
19. The device according to claim 18,
The device includes an information processing device and an adapter that can be communicatively connected to the information processing device,
The information processing device includes the concentration determining section,
The adapter includes the sample holding section and the measuring section.
20. The device according to claim 19,
The measurement unit of the adapter is configured to be operable by being supplied with power from the information processing device.
20. The device according to claim 19,
The information processing device includes a positioning unit, a storage unit, and a superimposed display unit,
The positioning unit acquires current position data at the time of the measurement,
The storage unit stores the fluorine ion concentration and the current position data in association with each other as measurement data,
The superimposition display section is a device that displays the measurement data read from the storage section in a superimposed manner on a map.