JP7723963B2 - DETECTION MATERIAL, DETECTION SYSTEM AND DETECTION METHOD FOR DETECTING METAL COMPONENTS ON A SOLID SURFACE - Google Patents

Description

The present invention relates to a detection material, detection system, and detection method for detecting metal components on a solid surface.

An example of a conventional metal ion detection material is the detection material described in Patent Document 1. This is made of a thin film of nanoparticles of an organic colorimetric reagent that can detect metal ions. The organic colorimetric reagent is localized on the outermost surface, and because it is an independent solid phase and is in the form of nanoparticles, it is a detection material that is highly reactive to liquid samples. Another example is the analysis sheet for metal materials described in Patent Document 2. This is a transparent hydrogel that contains a color former and acid that reacts with metal components to produce color, allowing for easy analysis of the components of metal materials.

The inventors of the present invention have developed a detection material, such as that described in Non-Patent Document 1, to enable the detection of metal ions in solid samples using the detection material described in Patent Document 1.

Patent No. 4185982 JP 2010-14500 A

Proceedings of the 67th Annual Meeting of the Japan Society for Analytical Chemistry, Vol. 67, p. 241 (2018)

Although laboratory instrumental analysis is commonly used to detect metal components on the surface of solid samples, given the demand for routine on-site analysis, there is a need for a technology that can easily analyze metal components on solid surfaces on-site without relying on instrumental analysis.

However, to achieve this, they discovered the need for a highly sensitive analytical device that does not use surface analysis equipment. The detection material in Patent Document 1 only handles aqueous samples and detects only water-soluble ionic species, so it is unable to detect metal components on solid surfaces. Furthermore, the analytical sheet in Patent Document 2 involves attaching a gel sheet containing a color developer to the metal surface, which allows for qualitative analysis of metals on solid surfaces but makes quantitative analysis difficult. Furthermore, it is not possible to separate substances or signals from interfering components, making it less versatile for use with the wide variety of alloys that exist.

In view of the above-mentioned problems, the present invention aims to provide a detection material, a metal ion detection system, and a metal ion detection method that are capable of detecting metal components on solid surfaces with high sensitivity using a color signal generated by a color reaction.

The inventors of the present invention conducted extensive research into the above-mentioned problems and discovered that by combining a detection material in which organic colorimetric reagent microparticles are supported and attached to the surface of a porous body with a gel containing a component that ionizes metal components on a solid surface, and by bringing the gel into contact with the solid surface and using the detection material to flow a detection fluid in one direction due to capillary action, metal ions extracted from the solid surface diffuse from the gel into the layer of organic colorimetric reagent microparticles on the surface of the porous body, undergoing a color reaction and producing color, making it possible to detect and quantify metal components on the solid surface, leading to the completion of the present invention.

That is, the detection material according to one aspect of the present invention that solves the above problem is:
A detection material for detecting metal components on a solid surface, comprising a sheet-like porous body, a detection unit, a metal ion extraction unit, a metal ion supply unit, and a water supply unit, wherein the detection unit has organic colorimetric reagent microparticles and is arranged on the surface of the porous body, the metal ion extraction unit has a gel having an ionizing component that ionizes the metal components on the solid surface, the metal ion supply unit is arranged on the surface of the porous body so that at least a part of the detection unit is in contact with the detection unit, and the metal ion extraction unit is in contact with the upper surface of the metal ion supply unit, so that the metal ions ionized by the ionizing component come into contact with the detection fluid and the metal ion supply unit. The detection material is arranged so that a driving force is provided to supply metal ions from a metal ion extraction section to a metal ion supply section, and is arranged so that metal ions from the metal ion supply section are diffused to the detection section by a detection fluid that flows from the water supply section through the metal ion supply section to the detection section, the water supply section being arranged on one end side of the porous body, and the porous body has a structure in which the detection fluid flows through the porous body from the water supply section to the end opposite the water supply section by capillary action, and the metal ions diffused from the metal ion supply section to the detection section by the detection fluid undergo a color reaction with organic colorimetric reagent microparticles, resulting in color development.

A detection system according to another aspect of the present invention comprises:
This is a detection system for detecting metal components on a solid surface using the above-mentioned detection material, characterized by having a determination unit that can determine the type of metal ion and the amount of eluted metal ion based on the color developed by the color reaction.

A detection method according to another aspect of the present invention includes:
A method for detecting metal components on a solid surface, comprising: a detection unit having organic colorimetric reagent microparticles and arranged on the surface of a porous body; a metal ion extraction unit having a gel having an ionizing component that ionizes metal components on the solid surface; a metal ion supply unit arranged on the surface of the porous body so that at least a portion of the detection unit is in contact with the detection unit; a water supply unit arranged on one end side of the porous body , through which metal ions ionized by the ionizing component are supplied from the metal ion extraction unit to the metal ion supply unit ; and a detection material having a porous body having a structure in which a detection fluid flows through the porous body from the water supply unit to the end opposite the water supply unit by capillary action,
This detection method is characterized by comprising: a contact step of bringing a metal ion extraction unit into contact with a solid surface; a supply step of supplying metal ions to the metal ion supply unit using the driving force of bringing the metal ion extraction unit into contact with the upper surface of the metal ion supply unit and the contact between the detection fluid and the metal ion supply unit; a diffusion step of flowing detection fluid from the water supply unit and diffusing the metal ions from the metal ion supply unit to the detection unit using the detection fluid that flows from the water supply unit through the metal ion supply unit to the detection unit; a reaction step in which the metal ions react with organic colorimetric reagent microparticles to produce a color; and a determination step in which at least one of the type of metal ion and the amount of eluted metal ion is determined based on the color produced by the color reaction.

As described above, the present invention provides a detection material, a metal ion detection system, and a metal ion detection method that can detect metal components on solid surfaces with high sensitivity using a color signal generated by a color reaction.

1 shows an example of the structure of a metal component detecting material (embodiment 1: gel-integrated type) equipped with a gel as a metal ion extraction section. An example of the structure of a metal component detection material that does not contain gel (embodiment 2: gel separation type) is shown. An example of the structure of a detection material (embodiment 3: combined ion supply and water supply type) in which the metal ion supply section and the water supply section are arranged in the same location is shown. A conceptual diagram of detecting metal components using a detection material is shown. A conceptual diagram of a detection system using a detection material is shown. 1 shows a flow diagram for detecting metal components in a detection system. FIG. 10 is a graph showing the relationship between the contact time with metal and the coloration distance when the detection materials according to Examples 11 to 16 are used (TLC analysis). 1 is a graph showing the relationship between the contact time with metal and the colored area when the detection materials of Examples 11 to 16 are used (TLC analysis). 10 is a graph showing the relationship between the contact time with metal and the amount of detected metal when using the detection materials of Examples 11 to 16 (ICP-OES). FIG. 10 is a graph showing the relationship between the coloration distance and the amount of detected metal when using detection materials according to Comparative Example 10 and Examples 11 to 16 (ICP-OES). FIG. 10 is a graph showing the relationship between the colored area and the amount of detected metal when using detection materials according to Comparative Example 10 and Examples 11 to 16 (ICP-OES). This is a diagram showing the relationship between the contact time with metal and the coloration distance using the detection materials of Examples 41 to 45 (ImageJ analysis). This is a diagram showing the relationship between the contact time with metal and the colored area when using the detection materials of Examples 41 to 45 (ImageJ analysis). This is a diagram showing the relationship between the contact time with metal and the coloration distance using the detection materials of Examples 51 to 55 (ImageJ analysis). This is a diagram showing the relationship between the contact time with metal and the colored area when using the detection materials of Examples 51 to 55 (ImageJ analysis). This is a diagram showing the relationship between the contact time with metal and the coloration distance using the detection materials of Examples 61 to 65 (ImageJ analysis). This is a diagram showing the relationship between the contact time with metal and the colored area when using the detection materials of Examples 61 to 65 (ImageJ analysis). 10 is a diagram showing reflection absorption spectra before and after contact of a metal with a metal ion supply unit without a metal ion extraction unit. FIG. This is a diagram showing the relationship between the contact time with metal and the colored area when using the detection materials of Comparative Examples 121 to 124 (ImageJ analysis). Photograph of the touch test device of Example 131 and RGB analysis by ImageJ (surface) Photograph of the touch test device of Example 131 and RGB analysis by ImageJ (back side) Photograph of the impregnated filter paper of Comparative Example 130 and RGB analysis by ImageJ (surface) Photograph of the impregnated filter paper of Comparative Example 130 and RGB analysis by ImageJ (back side)

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the specific examples mentioned in the following embodiments and examples.

(Detection material composition and detection principle)
The detection material according to this embodiment comprises a sheet-like porous body 40, a detection unit 10, a metal ion extraction unit 50, a metal ion supply unit 20, and a water supply unit 30, as shown in Figures 1 to 3. Metal ions supplied from the metal ion extraction unit 50 via the metal ion supply unit 20 are diffused by the detection fluid flowing by capillary action through the porous body 40 and the detection unit 10 supported and attached on the surface of the porous body 40 from the water supply unit 30 toward the end opposite the water supply unit, and develop color through a color reaction with organic colorimetric reagent microparticles, thereby enabling detection of metal components on the solid surface.

(Porous body)
The porous body preferably has a structure that allows the detection fluid to flow through the porous body by capillary action from the water supply portion toward the opposite end of the porous body. Suitable materials for the porous body include nylon, nitrocellulose, cellulose acetate, mixed cellulose esters, polyethersulfone, polytetrafluoroethylene, polyvinylidene fluoride, polycarbonate, polyethylene, etc.

Therefore, known porous media such as membrane filters, immunomembranes made of backing materials such as nitrocellulose, cellulose acetate, mixed cellulose esters, and polyethylene terephthalate, inorganic filters such as alumina and silica, cellulose fiber filter paper, and glass filters can be used.

When a membrane filter is used as the porous body, the pore size of the membrane filter is preferably 0.005 μm or more and 10 μm or less. When an immunomembrane is used as the porous body, the immunomembrane preferably has a lateral flow absorption time of 50 seconds or more and 300 seconds or less per 40 mm. When filter paper or glass filter is used as the porous body, the retention particle size of the filter paper or glass filter is preferably 1 μm or more and 5 μm or less.

Also, as used herein, "lateral flow" refers to a state in which the detection fluid flows from one end to the other in the longitudinal direction along the surface of the porous body or detection portion.

The porous body preferably has a flat surface capable of supporting the detection unit (described below). From the perspective of manufacturing, a surface roughness Ra of 1 μm or less is suitable for surface flatness. The porous body preferably has a structure that allows the detection fluid (described below) to flow through the porous body due to capillary action, and is preferably shaped like a sheet. Using a sheet-like porous body that allows the detection fluid to flow due to capillary action results in a detection material with excellent detection speed and detection sensitivity.

(Detection unit)
The detection unit preferably has organic colorimetric reagent particles disposed on the surface of the porous body, and preferably includes a wetting agent.
The organic colorimetric reagent that constitutes the organic colorimetric reagent microparticles is a pigment or dye that reacts with the metal ions migrated from the metal ion extraction section to produce a color. In the case of a pigment, the particles are made up of the organic colorimetric reagent alone agglomerated. In the case of a dye, the particles are made up of the dye and a microparticle-forming agent in nanoparticle form.

Known substances can be used as pigments for organic colorimetric reagents. For example, reagents such as dithizone, diphenylcarbazide, porphyrin, pyridylazoresorcinol, thiazolylazonaphthol, calcein, nitrosonaphthol, nitrosophenol, phenanthroline, bathophenanthroline, bipyridine, tripyridyltriazine, phenylenediamine, phenylenedithiol, pyrocatechol, chromazole, xylenol orange, 8-quinolinol, curcumin, flavonol, flavone, anthocyanin, and alizarin can be used.

Known substances can be used as dyes for organic colorimetric reagents. Dyes are soluble in water or mixed solvents at a specific pH. Examples of reagents include anionic reagents containing one or more sulfonic acid groups, carboxyl groups, hydroxyl groups, thiol groups, or phosphate groups, and cationic reagents containing one or more amino groups, trialkylamino groups, dialkylamino groups, N-methylpyridyl groups, etc. In addition, the reagent group includes phenylfluorone, pyrocatechol biored, pyrogallol red, bromopyrogallol red, chromazol, tiron, cupferron, chromotropic acid, dinitronaphthalenediol, morin, alizarin red, stilbazo, ericrom black T, chalconecarboxylic acid, kargamite, hydroxynaphthol blue, gallion, spadons, beryllion II, calcichrome, magon, sipan, phenazo, arsenazo, chlorosulfonazo III, sulfonazo, dinitrosulfonazo III, arsenazo K, sulfochlorophenol S, sulfacezane, pyri Diazonaphthol, pyridylazoresorcinol, thiazolylazophenol, thiazolylazonaphthol, 5-bromo-PAPS, 5-bromo-PAPAP, 5-bromo-DMPAP, nitroso-PAPS, 5-chloro-PADAP, TAMB, BTMB, 3,5-dibromo-PAMB, TAMSMB, 5-chloro-PADAB, 5-bromo-PMDAB, 5-bromo-PADAB, 5-bromo-PSAA, 3,5-dibromo-PAESA, phthalein complex, thymolphthalein complex, calcein, methylcalcein, calcein blue, Quinn 2, Fura 2, Indo 1, Rod 2, Fluo 3, xylenol orange, methyl thymol blue, methyl xylenol blue, glycine cresol red, glycine thymol blue, sarcosine cresol red, alizarin complexone, 8-quinolinol, oxine-5-sulfonic acid, azomethine H, GHA, SAPH, SABF, 3-OH-PAA, zincon, murexide, 2-nitroso-1-naphthol-4-sulfonic acid, nitroso R acid, nitroso-DMAP, nitroso-ESAP, nitroso-PSAP, 2,2'-bipyridine, 1,10-phenanthroline, bathophenanthroline disulfonic acid, tripyridyl olioxalate Examples of suitable dyes that can be used include dimethylglyoxime, pyridyldiphenyltriazine, vasoproinedisulfonic acid, BCA, dimethylglyoxime, nioxime, DAB, DAN, o-phenylenediamine, 5-chloro-1,2-phenylenediamine, 5-nitro-1,2-phenylenediamine, TPPS, T(3-MPy)P, T(4-MPy)P, T(5-MPy)P, TTMAPP, dithizone, thioxine, DDTC, APDC, bismuthiol II, indigo carmine, 2,6-dichloroindophenol, neutral red, gallocyanine, methylene blue, variamine blue B, and 3,3'-dimethylnaphthidine.

To detect specific metal ions, 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol or α,β,γ,δ-tetrakis(1-methylpyridinium-4-yl)porphyrin are effective for detecting Cd.

For Pb, methylthymol blue or α,β,γ,δ-tetrakis(1-methylpyridinium-4-yl)porphyrin are effective.

The use of dithizone is effective against Hg.

For Ni, using 2-(3,5-dibromo-2-pyridylazo)-5-(diethylamino)phenol or 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol is effective.

Using Zincon is effective against Zn.

For Mn, using 2-(3,5-dibromo-2-pyridylazo)-5-(diethylamino)phenol or 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol is effective.

For Fe, using bathophenanthroline or sodium bathophenanthroline sulfonate is effective.

For F, using sodium flavonol-2'-sulfonate or flavonol, fisetin, or morin is effective.

For B, using chromotonous acid or curcumin is effective.

The microparticle-forming agent can be an organic polymer such as latex or polystyrene, or a metal oxide such as silica, alumina, or zirconium, and should be between 1 nm and 1000 nm in size, preferably between 3 nm and 500 nm, and capable of adsorbing a dye, which is an organic colorimetric reagent.

When a pigment-type organic colorimetric reagent is provided in particulate form, the average particle size is preferably 10 nm or more and 500 nm or less, more preferably 20 nm or more and 200 nm or less, and even more preferably 50 nm or more and 150 nm or less. This allows the organic colorimetric reagent to be sufficiently supported in the porous body, and the thickness of the detection section can be repeatedly adjusted with high accuracy. The average particle size can be determined by the arithmetic mean through observation with an electron microscope.

Dye-type organic colorimetric reagents induce aggregation of microparticles by being adsorbed onto the surface of a microparticle-forming agent. The aggregates formed are large enough to be supported on the surface of a porous material, allowing detection units to be repeatedly and accurately produced.

Organic colorimetric reagent microparticles are highly hydrophobic, and in order for the detection unit to have sufficient water permeability for the diffusion and detection of metal ions in the detection fluid, it is preferable that the detection unit contain a wetting agent for wetting with the detection fluid. Therefore, it is preferable to add at least one of the following wetting agents to the detection unit: a gelling agent, a water-soluble polymer, or a low-molecular-weight moisturizing agent, as described below.

Gelling agents that can be used include known substances that can contain aqueous solvents, such as gelatin, collagen hydrolysates, pectin, carrageenan, glucomannan, organic electrolyte oligomers, and interpenetrating polymer networks.

Water-soluble polymers that can be used include polyvinyl alcohol, polydiallyldimethylammonium salt, polyanethole sulfonate, and dendron.

Low molecular weight humectants include well-known compounds such as amino acids, urea, and glycerin, which can contain enough water for ionization, thereby stably retaining metal ions in the gel layer.

The ratio of organic colorimetric reagent microparticles to wetting agent may be 100:1 to 1:100,000 by weight, preferably 10:1 to 1:1,000, and more preferably 1:1 to 1:1,000.

From the perspective of semi-quantitative or quantitative analysis, the thickness of the detection area is preferably 100 nm or more and 20 μm or less, more preferably 200 nm or more and 3 μm or less, and even more preferably 400 nm or more and 1 μm or less. This ensures sufficient signal strength for the color reaction, and the diffusion of the detection fluid due to capillary action enables highly sensitive, highly accurate quantitative analysis with little variance and high reproducibility. The thickness of the detection area can be determined by observation with an electron microscope and a digital microscope.

(Method for producing the detection unit)
The detection unit can be fabricated directly on the surface of a porous material by suction filtering a dispersion of a particulate organic colorimetric reagent or a dispersion of a particle-forming agent and an aggregate of the organic colorimetric reagent. The thickness of the detection unit can be adjusted by changing the concentration of the dispersion. This fabrication method allows adjustment of the detection sensitivity of metal ions.

(Metal ion extraction section)
The metal ion extraction unit preferably includes a gel having an ionizing component that ionizes metal components on the solid surface. Specifically, the metal ion extraction unit preferably includes a gel that can ionize metal components on the solid surface and extract and retain the metal ions, and that, when in contact with the metal ion supply unit, allows the metal ions to migrate via the metal ion supply unit to the detection unit by the detection fluid.

The metal ion extraction unit may have a support frame that can hold the gel; if the gel itself is strong enough to maintain its shape, a support frame is not necessary; however, it is preferable that at least a portion of the gel be in direct contact with the surface of the solid sample.

It is preferable to use an extraction enhancer that contains water as the ionizable component.

The gel is preferably hydrophilic, and known substances capable of containing aqueous solvents, such as gelatin, collagen hydrolysate, agar, pectin, carrageenan, glucomannan, organic electrolyte oligomers, and interpenetrating polymer networks, can be used. This allows the gel to contain sufficient water to ionize the metal components, allowing the metal ions to be stably retained in the gel layer. The gel may also function as an extraction enhancer.

The extraction enhancer preferably contains at least one of an ionization agent, an extraction agent, an ionic strength adjuster, and a masking agent.

In order to ionize a sufficient amount of metal components for metal ion detection, it is preferable to include an ionizing agent in addition to water. Examples of ionizing agents include acids, alkalis, oxidizing agents, and reducing agents, and preferred examples include nitric acid, hydrochloric acid, sulfuric acid, perchloric acid, sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate.

For metals that are difficult to ionize with an ionizing agent, it is preferable to use an extractant appropriate for the target metal component. Examples of extractants that can be used include solvent extraction reagents, such as dithizone, diethyldithiocarbamate, xanthogenic acid, 8-quinolinol, α-dioxime, chloropene, β-diketone, acetylacetone, thenoyltrifluoroacetone, 1-nitroso-2-naphthol, 1-(2-pyridylazo)-2-naphthol, ethylenediaminetetraacetic acid, 1,10-phenanthroline, neocuproine, 2,2'-dipyridyl, tributyl phosphate, and crown ethers.

If components other than the target metal component ionize and interfere with detection, it is preferable to use a masking agent to remove the interfering components. Examples of masking agents include thiourea, ethylenediaminetetraacetic acid, potassium cyanide, triethanolamine, acetylacetone, 2,3-dimercaptopropanol, sodium diethyldithiocarbamate, 3-mercaptopropionic acid, 2-aminoethanethiol, thioglycolic acid, Unithiol, oxalic acid, tartaric acid, citric acid, salicylic acid, tiron, ascorbic acid, potassium iodide, sodium thiosulfate, sodium sulfide, ammonium fluoride, ammonium phosphate, hydroxylamine, 1,10-phenanthroline, and hydrogen peroxide. It is preferable to select and include a masking agent depending on the target metal component.

It is also preferable to include an ionic strength adjuster in the metal ion extraction section to stabilize the extraction rate of metal ions. Salts may be added as ionic strength adjusters. Examples of salts include sodium chloride, sodium perchlorate, sodium bromide, sodium fluoride, potassium chloride, potassium nitrate, potassium bromide, potassium iodide, potassium perchlorate, magnesium sulfate, and calcium sulfate, and it is preferable to select one that is appropriate for the purpose.

In the metal ion extraction section, substances suitable for detecting the target metal component are selected from ionizing agents, extractants, ion strength adjusters, and masking agents, and mixed at the appropriate concentration to actively dissolve and extract the target metal component, making it suitable for use in solid surface analysis. Alternatively, by combining components of an extraction enhancer, environmental exposure tests and stress tests can be performed on solid surfaces. For example, it can be used for environmental assessments of salt damage, predicting the impact of acid rain, investigating the dissolution of allergens, and safety studies of baby toys.

(Metal ion supply unit)
The metal ion supply unit is disposed so that at least a portion thereof is in contact with the detection unit. Metal ions ionized by the ionizable component are supplied from the metal ion extraction unit to the metal ion supply unit. That is, the metal ion supply unit is disposed so that a portion of the metal ion supply unit is in contact with the detection unit in order to supply the target metal component extracted by the metal ion extraction unit to the detection unit. Alternatively, it is preferable to use a portion of the detection unit as the metal ion supply unit, and it is most preferable that the metal ion supply unit be in contact with the detection unit on all sides.

The metal ion extraction unit may be in constant contact with the metal ion supply unit (gel-integrated type), or it may be in contact with the metal ion supply unit only when the metal ion supply unit is receiving a supply of metal ions (gel-separated type). Furthermore, the metal ions taken up in the metal ion extraction unit may be supplied to the metal ion supply unit via another substance such as a separate gel or ion-permeable sheet. The form is not important as long as the metal ions extracted from the solid surface and taken up in the metal ion extraction unit can be supplied to the metal ion supply unit.

(Water supply section)
The water supply section is preferably arranged at one end of the porous body. Alternatively, it is also preferable that the metal ion supply section and the water supply section are arranged in the same location. The water supply section is a section that supplies the detection fluid. One end of the porous body may be used as the water supply section. Alternatively, it may be configured by connecting another porous body, fiber, or the like. Alternatively, at least a part of the metal ion supply section may be used as the water supply section. The material that constitutes the water supply section is not particularly limited, but it is preferably the same material as the porous body.

(Detection fluid)
The detection fluid wets the metal ion supply section and flows unidirectionally through the porous body and the detection section from the water supply section to the opposite end of the water supply section. The driving force for the detection fluid flow is mainly the lateral flow of the detection fluid due to capillary action caused by the microstructure and volatilization of the porous body.

The components of the detection fluid are not particularly specified, but an aqueous solvent is advantageous for ionizing the target metal component, as it allows the ions to dissolve from the solid surface and remain stable.

Furthermore, it is preferable that the detection fluid contains a sensitivity enhancer. In other words, it is preferable to add a sensitivity enhancer to the detection fluid in order to promote or stabilize the movement of ions in the detection area, thereby extending the color-developing area described below and improving detection sensitivity.

Sensitivity enhancers include the aforementioned wetting agents and extraction enhancers, as well as pH buffer components and ion-pairing reagents.

(Color reaction)
In the detection section, metal ions diffused from the metal ion supply section to the detection section by the detection fluid react with the organic colorimetric reagent microparticles to produce a color. That is, metal ions eluted from the solid surface react with the organic colorimetric reagent microparticles, allowing the detection of metal ions. The area in the detection section that produces a color due to the color reaction is called the colored section.

(Embodiment 1: Extraction of metal components using a gel-integrated type)
Figure 1 shows an example of the structure of a gel-integrated metal component detection device, which uses gel as a metal ion extraction unit. With this type of detection device, metal components are extracted by grasping the porous body and contacting the metal ion extraction unit with the solid surface to be analyzed. This configuration allows the detection device to be directly contacted with the metal surface, making it highly portable. Additionally, contamination during the detection operation can be prevented, enabling accurate detection of metal components present on the metal surface.

(Embodiment 2: Extraction of metal components by gel separation)
Figure 2 shows an example of the structure of a gel-separation-type metal detection material that does not contain a gel. With this type of detection material, metal components are extracted by first contacting the metal ion extraction unit with the solid surface to be analyzed, and then contacting the metal ion supply unit. This configuration allows for detection of metal components on metal surfaces located in narrow spaces or on the back surfaces of holes using plastic tweezers or a non-metallic spatula, making it applicable to solid surfaces with complex shapes. Additionally, the gel-separation type eliminates concerns about the effects on the detection unit and dramatically increases the number of gel component options, making it possible to accommodate a wide variety of solid samples and suitable for environmental exposure tests and stress tests of solid surfaces. In particular, if the gel component has an effect on the organic colorimetric reagent microparticles, contact is limited to the detection period, minimizing the effect. Furthermore, the detection material can be stored appropriately until immediately before detection.

(Embodiment 3: Extraction of metal components by combined ion supply and water supply)
Figure 3 shows an example of the structure of a detection material in which the metal ion supply unit and the water supply unit are arranged in the same location. In the case of this type of detection material, by pre-soaking the gel in the metal ion extraction unit with a sufficient amount of detection fluid to diffuse the metal components into the detection unit, the detection fluid seeping out of the gel becomes a unidirectional lateral flow from one end of the detection unit to the other end, allowing the metal components to be detected. This configuration makes it possible to achieve a detection material that is simple and safe, without the need to prepare a separate detection fluid. Note that the metal ion extraction unit may be either embodiment 1 or 2.

The detection material for detecting metal components of the present invention is sometimes referred to as a touch test device in this specification.

(Detection of metal ions)
Figure 4 illustrates the concept of metal component detection in a lateral flow touch test device using a detection fluid after the gel has been brought into contact with a solid surface in both the gel-integrated and gel-separated types. The supply of detection fluid from the water supply unit is stopped at the solvent front 12 after the detection fluid has penetrated a certain distance, and the detection unit and color-developed unit are analyzed for color up to that point. In other words, the solvent front 12 located within the detection unit is a line that serves as a guide for stopping the flow of detection fluid, and its location varies depending on the target metal component.

The type and amount of metal ions extracted by the metal ion extraction section can be selected and controlled by the extraction enhancer contained in the gel in the extraction section. Metal ions are generally extracted using an acidic aqueous solution, but in this embodiment, metal ions are extracted using a solid gel, increasing the ease of use and versatility of this detection material. Compared to acidic solutions, the gel in this extraction section can hold a wider variety of extraction enhancers, and the polymers that make up the gel can also serve as extraction enhancers.

The metal ions extracted into the metal ion extraction section are gradually diffused through the detection section by the detection fluid, which flows from the water supply section through the metal ion supply section and into the detection section. Here, the detection fluid, flowing by lateral flow from the water supply section, washes away metal ions near the metal ion supply section. This drives the metal ions to diffuse from the metal ion extraction section to the supply section, where they are then washed away by the fluid. This process occurs continuously, resulting in the lateral flow of the detection fluid causing metal ions to continuously diffuse and be supplied from the metal ion extraction section to the detection section. Of the metal ions supplied to the detection section in this way, some react with nearby organic colorimetric reagent microparticles and stop diffusing, but unreacted metal ions continue to diffuse through the detection section by lateral flow, reacting with organic colorimetric reagent microparticles in other locations. This reaction is thought to occur repeatedly along the detection section from one end to the other due to lateral flow, expanding the area of the colored area and continuing until the lateral flow is stopped by an arbitrarily set solvent front.

The length and area of the colored area, as well as the absorbance, hue, brightness, and saturation of the colored area, and the differences in these values between the detection area and the colored area, are correlated with one or more factors and the amount of metal ions eluted from the solid surface, and it is believed that this enables qualitative or quantitative analysis of the target metal on the solid surface.

In conventional detection materials (e.g., Non-Patent Document 1 and Patent Document 2), the concentration of metal ions is determined by the color intensity of the colored area. This narrow sensitivity range allows for qualitative determination, but quantification is difficult and subject to the influence of interfering components. The detection material of this embodiment can remove interfering components using a metal ion extraction unit or detection fluid, and by developing the target component in one direction using lateral flow, it is possible to add factors such as the length and area of the colored area, absorbance, hue, brightness, and saturation to the material, resulting in high sensitivity and an expanded quantification range, enabling quantification over a wide range. Furthermore, the addition of factors such as length and area allows for highly accurate determination even by visual inspection and simplifies the analysis process, making it more suitable for use in on-site analysis than conventional detection materials.

(Detection System)
5 is a conceptual diagram of a metal ion detection system, which includes a determination unit 60 that can determine the type of metal ion and the amount of eluted metal ion based on the color developed by the color reaction in the detection unit 10.
The determination unit 60 can use known technology capable of detecting color. Specifically, the type of metal ion and the amount of eluted metal ion can be determined by visual inspection or by using an optical analyzer such as a colorimeter that can detect color, a camera, a scanner, a TLC scanner, an optical fiber spectrometer, or the like, and importing color data into a computer, mobile terminal, or the like. The determination can be made by appropriately analyzing the imported color data using color analysis software or spreadsheet software pre-installed on the computer or mobile terminal, or the like. In the case of visual inspection, the color, colored length, colored area, etc. can be compared with a previously prepared determination sample to make the determination.

(Detection method)
FIG. 6 is a diagram showing the procedure of a method for detecting metal on a solid surface using the touch test device of this embodiment.
The detection of metal ions includes a wetting step in which the gel provided in the metal ion extraction section is moistened by adding water to the gel; a contact step in which the metal ion extraction section is brought into contact with a solid surface; a supply step in which the metal ions are supplied to the metal ion supply section; a diffusion step in which a detection fluid is flowed from the water supply section to diffuse the metal ions into the detection section; a reaction step in which the metal ions react with organic colorimetric reagent microparticles to produce a color; and a determination step in which the type of metal ion and the amount of eluted metal ion are determined based on the color produced by the color reaction.

(Wetting steps: S1, S1')
The wetting step is a stage in which the gel provided in the metal ion extraction unit is moistened with water (S1 is a gel-integrated type, and S1' is a gel-separated type).

(Contacting steps: S2, S2')
The contacting step is a step in which a gel is brought into contact with a solid surface so that metal components on the solid surface can be ionized, the metal ions can be retained in the metal ion extraction section, and the metal ions can be transferred to the detection section by the detection fluid when the gel comes into contact with the metal ion contact section. If the gel is dry, it is moistened with an aqueous solvent as appropriate before contacting (S1 is a gel-integrated type, and S1' is a gel-separated type).

(Supply steps: S3, S3')
The supply step is a stage in which metal ions are moved to the metal ion supply unit. After appropriate contact in the contact step, in the gel-integrated type, an appropriate amount of metal ions can be supplied by separating the gel from the solid surface. Alternatively, the gel can be separated from the solid surface, and the metal ion supply unit can be supplied with the driving force of contact between the detection fluid from the water supply unit and the metal ion supply unit. In the gel-separated type, the gel is first brought into contact with the solid surface to elute the metal ions into the gel, and then the metal ion extraction unit is placed on the metal ion supply unit, thereby supplying an appropriate amount of metal ions. Alternatively, after the metal ion extraction unit is placed on the metal ion supply unit, the metal ions can be supplied with the driving force of contact between the detection fluid from the water supply unit and the metal ion supply unit.

(Diffusion step: S4)
The diffusion step is a step that occurs after the supply step, in which the detection fluid from the water supply section is provided by immersing the supply section or dripping it onto the supply section, or in the case of a combined ion supply-water supply type, by allowing a sufficient amount of detection fluid to be contained in a gel, and a lateral flow of detection fluid occurs in one direction toward the end opposite the water supply section, and this flow diffuses the metal ions from the metal ion supply section into the detection section.

(Reaction step: S5)
The reaction step is a stage in which the metal ions diffused into the detection unit in the diffusion step react with the organic colorimetric reagent particles in the detection unit to produce color. In the reaction step, the supply of detection fluid from the water supply unit is stopped when the detection fluid has penetrated and diffused up to the solvent front position.

(Determination step: S6)
In the determination step, the determination unit acquires color data from the detection unit and the color-development unit up to the time when the metal ions react with the organic colorimetric reagent microparticles in the reaction step. The color data can be acquired visually or using an optical analyzer such as a colorimeter that can detect color, a camera, a scanner, a TLC scanner, an optical fiber spectrometer, or the like, and the color data can be imported into a computer, mobile device, or the like. The data can also be read using color analysis software or spreadsheet software pre-installed on a computer or mobile device, and analyzed and detected as appropriate.

The detection material, metal ion detection system, and metal ion detection method according to the above embodiments will now be described in detail. Table 1 lists examples and comparative examples.

(Examples 11 to 16: Overview)
A contact analysis of solid metallic tin was carried out using a gel separation type of embodiment 2 using a touch test device (detection material) in which a dithizone nanofiber membrane was used as the detection section and a gel of alkali-treated bovine bone gelatin was used as the metal ion extraction section.

(Examples 11 to 16: Preparation of detection unit)
Dithizone, a pigment, was prepared by injecting 100 μl of a 2 mM dithizone acetone solution into 9.9 ml of 0.25 M L-ascorbic acid aqueous solution stirred at 1000 rpm using a microsyringe and allowing to stand for 2 minutes to produce a nanoparticle dispersion. A 10 ml solution containing 10 g/L of humectant collagen peptide and 3 mM 4-methoxyphenol, adjusted to pH 2.0 with hydrochloric acid, was separately prepared and poured into a filter equipped with a nylon membrane filter (pore size 0.20 μm) along with the dithizone nanoparticle dispersion, followed by vacuum filtration. Dithizone nanofibers were present on the membrane filter as a bluish-gray thin film. After drying, the sample was cut into approximately 30-40 mm long and 3 mm wide pieces to produce a touch test device with the dithizone nanofilm as a detection element and the nylon membrane filter as a porous material.

(Examples 11 to 16: Water supply section)
In this example, one end of the nylon membrane filter was used as the water supply part, and in all subsequent examples and comparative examples, one end of the porous body was also used as the water supply part.

(Examples 11 to 16: Preparation of metal ion extraction unit)
A 50 g/L bovine bone-derived gelatin solution was adjusted to pH 2.0 by adding hydrochloric acid, an ionizing agent. 10 ml of this solution was added to a plastic petri dish, cooled in a refrigerator, and cut into 3 x 3 mm pieces to prepare a gelatin gel. After wiping the gel with Kimwipes (manufactured by Nippon Paper Crecia Co., Ltd.), the pH was measured using an ISFET electrode (ion-sensitive field-effect transistor electrode). The pH of the gel was 2.024.

(Examples 11 to 16: Metal ion supply unit)
In this example, one end of the detection section was used as the metal ion supply section. In all subsequent examples and comparative examples, the same one end of the detection section was used as the metal ion supply section.

(Examples 11 to 16: Detection of metal ions)
The touch test device was attached and fixed to a plastic plate with double-sided tape. The cut gelatin was contacted with the metal tin for 10 to 600 seconds, and then placed on the metal ion supply unit (detection unit) so that the contacted surface was in contact with the detection unit. A pH 2.0 hydrochloric acid solution was applied as the detection fluid from the water supply unit, and the detection fluid was stopped when the solvent front reached a point 25 mm from the end of the metal ion supply unit. As a comparative example, the gelatin in the metal ion extraction unit was contacted with the metal ion supply unit without contacting the metal tin (Comparative Example 10). The detection fluid was supplied from the water supply unit, and the development time until the solvent front reached a point 25 mm from the end of the metal ion supply unit was 7 minutes 9 seconds, 7 minutes 5 seconds, 7 minutes 49 seconds, 8 minutes 27 seconds, and 7 minutes 21 seconds, with an average of 7 minutes 34 seconds ± 34 seconds. The detection unit turned pink.

(Examples 11 to 16: Determination of metal ions)
After development and color development, the touch test device was scanned with a 1 mm x 2 mm beam of 610 nm using a thin layer chromatography (TLC) scanner to measure the reflection absorbance. In addition, the gelatin and the touch test device were wet decomposed with concentrated nitric acid, and tin was quantified by inductively coupled plasma optical emission spectroscopy (ICP-OES).
The contact time and length of the colored portion (colored distance), the Rf value determined from the solvent front, and the colored area (area of the colored portion with reflection absorbance at 610 nm) determined from TLC are shown in Table 2. Rf = colored distance/distance from the upstream end of the metal ion supply portion to the solvent front.

Table 3 shows the amounts of tin in the gelatin and detection material in the metal ion extraction portion of the touch test device, as well as the total amount of these, as determined by ICP-OES analysis.

Figure 7 shows a plot of contact time and coloration distance from TLC analysis, and Figure 8 shows a plot of contact time and coloration area. Figure 9 shows a plot of contact time and the amount of eluted tin from ICP-OES. Figure 10 shows the relationship between coloration distance and the amount of eluted tin substance, and Figure 11 shows a plot of contact area and the amount of eluted tin substance.

TLC analysis confirmed that the color distance and Rf value increased and the colored area increased depending on the contact time between the gelatin gel and metallic tin, confirming a correlation (Table 2, Figures 7 and 8). ICP analysis confirmed that the amount of tin eluted increased depending on the contact time between the gelatin gel and metallic tin, confirming a correlation (Figure 9). Tin analysis using this touch test device allows quantitative analysis of tin from the colored distance and colored area, as shown in Figures 10 and 11. This example enables quantitative analysis of elution from a solid surface in the range of several nmol to several tens of nmol.

(Examples 21 to 23: Overview)
Using a touch test device having a dithizone nano-thin film as a detection unit prepared in accordance with Example 11, contact analysis of solid metallic tin was carried out in the gel-integrated type of embodiment 1.

(Examples 21 to 23: Preparation of touch test device (integrated with gel))
A 0.25 mm thick plastic plate with a 3 mm wide rectangular hole was placed on one end of the detection part of Example 11, and the same gelatin gel as in Example 11 was crushed with a spatula and screen coated.

(Examples 21 to 23: Detection of metal ions)
The touch test device was fixed in the same manner as in Example 11, and was kept in contact with the metal tin for 60, 180, and 300 seconds. After contact, a pH 2.0 hydrochloric acid solution was introduced as a detection fluid from the water supply section, and the detection fluid was stopped when the solvent front reached a point 25 mm from the end of the metal ion supply section. The detection section turned pink.

(Examples 21 to 23: Determination of metal ions)
The entire image of the detector was captured using a scanner, and the captured image was processed using ImageJ, an image processing software. RGB analysis was performed within a range of ±1 mm (2 mm wide) from the center line of the 3 mm wide device and the area surrounded by the length of the detector. Based on the difference between the blue-gray detection area and the pink colored area of the plots, the colored distance and colored area ( _SR , _SG , _SB ) were calculated and are shown in Table 4.

ImageJ analysis showed that, similar to the gel-separated type, the colored distance and Rf value increased and the colored area increased with contact time in the integrated gel touch test device, confirming a correlation.

(Examples 31 to 33: Overview)
Using a gel separation type touch test device having a dithizone nano-thin film as a detection section prepared in accordance with Example 11, solid metallic tin was analyzed by a combined ion supply and water supply method.

(Examples 31 to 33: Preparation of touch test device (combined ion supply and water supply type))
The porous body was cut and shaped so that the detection part was exposed at one end of the touch test device prepared in the preparation of the detection part of Example 11.

(Examples 31 to 33: Detection of metal ions)
A 3 x 3 mm piece of gelatin was brought into contact with metallic tin for 60, 180, and 600 seconds, and then the contacted surface of the gelatin was placed in contact with a metal ion supply unit (detection unit) provided at one end of the porous body and left for 20 minutes.

(Examples 31 to 33: Determination of metal ions)
The image of the entire detection material was scanned and analyzed as RGB values. After leaving it for 20 minutes, the solvent front distances were 2.850 cm, 2.850 cm, and 2.815 cm. The lateral flow repeatability was good.
Table 5 shows the color distances determined by ImageJ analysis, the Rf values determined from the solvent front, and the area intensities ( _SR , _SG , _SB ) for each of the R, G, and B components.

In the case of porous materials such as nylon membrane filters, where only a minute amount of water is required for lateral flow, if the gel in the metal ion detection section already contains more water than is necessary for lateral flow, that water can be used as the detection fluid, and the detection fluid seeping out of the gel will form a unidirectional lateral flow from one end of the detection section to the other, allowing metal components to be detected. Because no more detection fluid than the amount already contained is required, detection is possible simply by contacting the sample solid.

(Examples 41 to 45: Overview)
Using a touch test device having a dithizone nano-thin film as a detection section prepared in accordance with Example 11, the gel was brought into contact with an alloy containing tin to detect metal components.

(Examples 41 to 45: Touch Test Device)
The same touch test device as in Example 11 was used.

(Examples 41 to 45: Detection of metal ions)
As the alloy sample containing tin, 45% tin and 55% lead solder was used. 20 g of the alloy was placed in a heat-resistant container, melted at approximately 300° C. using a hot plate, and then allowed to cool and solidify.
A 3 x 3 mm piece of gelatin (pH 2.036) was brought into contact with the alloy sample for 10, 30, 60, 180, and 600 seconds, and then placed on the metal ion supply section (detection section) so that the contacted surface was in contact with the detection section. A pH 2.0 aqueous hydrochloric acid solution was introduced from the water supply section as the detection fluid, and the detection fluid was stopped when the solvent front reached a point 25 mm from the end of the metal ion supply section.

(Examples 41 to 45: Determination of metal ions)
The data was imported and analyzed as RGB values using ImageJ in the same manner as in Example 21. The colored distance, Rf value, and colored area ( _SR , _SG , _SB ) are shown in Table 6, and a plot of the contact time and colored distance from ImageJ analysis is shown in Figure 12, and a plot of the contact time and colored area _SR is shown in Figure 13.

This touch test device was found to be capable of detecting tin in alloy samples.

(Examples 51 to 55: Overview)
A touch test device with a 3,5-diBrPADAP nano-thin film in the detection section and a gel consisting of only water and gelatin in the metal ion extraction section was used to perform contact analysis of nickel from 100 yen coins.

(Examples 51 to 55: Preparation of detection unit)
The pigment 3,5-diBrPADAP was prepared by injecting 100 μl of a 2 mM 5-diBrPADAP acetone solution into 10 ml of ultrapure water stirred at 1,000 rpm using a microsyringe, then allowing it to stand for 2 minutes to form a nanoparticle dispersion. The 3,5-diBrPADAP nanoparticle dispersion was poured into a filter equipped with a nylon membrane filter (pore size 0.20 μm) and filtered under reduced pressure. The 3,5-diBrPADAP nanoparticles were present on the membrane filter as an orange thin film. After drying, the filter was cut to a width of 3 mm to produce a touch test device in which the 3,5-diBrPADAP nanofilm served as the detection element and the nylon membrane filter was used as the porous body.

(Examples 51 to 55: Preparation of metal ion extraction unit)
10 ml of a 50 g/L solution of bovine bone-derived gelatin dissolved in ultrapure water was added to a plastic dish, cooled in a refrigerator, and cut into 3 x 3 mm pieces to produce a gel consisting only of water and gelatin. After wiping the gel with a Kimwipe, the pH was measured using an ISFET electrode. The pH of the gel was 6.099.

(Examples 51 to 55: Detection of metal ions)
As in Example 11, the touch test device was attached and fixed to a plastic plate with double-sided tape. The cut gelatin was contacted with a 100-yen coin for 10 to 300 seconds, then placed on the metal ion supply unit (detection unit) so that the contacted surface was in contact with the detection unit. A 0.01 mol/kg borate buffer solution (pH 9.18) was introduced from the water supply unit as the detection fluid. The detection fluid was stopped when the solvent front reached a point 25 mm from the end of the metal ion supply unit. The colored area turned reddish purple.
The detection fluid was supplied from the water supply section, and the development time until the solvent front reached a point 25 mm from the end of the metal ion supply section was 2 minutes 12 seconds, 1 minute 56 seconds, 2 minutes 15 seconds, 2 minutes 5 seconds, and 2 minutes 19 seconds, with an average of 2 minutes 9 seconds ± 9 seconds.

(Examples 51 to 55: Determination of metal ions)
Data was scanned and analyzed as RGB values using Image J in the same manner as in Example 21. Based on the difference between the orange detection area and the reddish-purple colored area in these plots, the colored distance, Rf value, and colored area ( _SR , _SG , _SB ) are shown in Table 7. A plot of contact time and colored distance from Image J analysis is shown in Figure 14, and a plot of contact time and colored area _SB is shown in Figure 15.

It was found that metal ions can be extracted from solid surfaces using only water as the metal ion extraction agent.

(Examples 61 to 65: Overview)
Contact analysis of nickel from 100-yen coins was performed using a touch test device with a 3,5-diBrPADAP nanofilm in the detection section and a gel containing artificial sweat and thiourea as a masking agent in addition to water and gelatin in the metal ion extraction section.

(Examples 61 to 65: Preparation of touch test devices)
A 50 g/L bovine bone-derived gelatin solution was dissolved in ultrapure water to a concentration of 31 mM sodium chloride, 6.1 mM potassium chloride, 14.0 mM lactic acid, 10 mM urea, 5.3 mM ammonia, and 5.3 mM thiourea (a masking agent). The pH was then adjusted with aqueous sodium hydroxide solution to a pH of 5.5-5.7, which corresponds to the acidic sweat range. Sodium chloride acts as an ionic strength adjuster, lactic acid acts as a humectant, and urea, due to its high complex formation constant with nickel ions, also serves as an extraction enhancer. 10 ml of this solution was added to a plastic dish, cooled and hardened in the refrigerator, and cut into 3 x 3 mm pieces to produce a gel containing artificial sweat and a masking agent. After wiping the gel with a Kimwipe, the pH was measured using an ISFET electrode. The gel's pH was 5.442. As in Example 11, the touch test device was attached to a plastic plate with double-sided tape.

(Examples 61 to 65: Detection of metal ions)
The cut gelatin was contacted with a 100-yen coin for 10 to 300 seconds, then placed on the metal ion supply section (detection section) with the contacted surface facing the detection section. A 0.01 mol/kg borate buffer solution (pH 9.18) was introduced from the water supply section as the detection fluid, and the detection fluid was stopped when the solvent front reached a point 25 mm from the end of the metal ion supply section. The borate buffer solution is a sensitivity enhancer that ensures color development at the optimal pH. The colored section turned reddish purple.

(Examples 61 to 65: Determination of metal ions)
Data was scanned and analyzed as RGB values using Image J in the same manner as in Example 21. Based on the difference between the orange detection area and the reddish-purple colored area in these plots, the colored distance, Rf value, and colored area ( _SR , _SG , _SB ) are shown in Table 8. A plot of contact time and colored distance from Image J analysis is shown in Figure 16, and a plot of contact time and colored area _SB is shown in Figure 17.

Artificial sweat components can be reproduced in the metal ion extraction section, making this analysis a potential evaluation method for subjects with metal allergies. Furthermore, compared to Example 51, in which only water was used and no ionic strength adjusters, extraction enhancers, or wetting agents were used, the amount of extraction continued to increase until the contact time was extended to a certain extent.

(Examples 71 to 74: Overview)
The elution behavior of metal ions from solid metal surfaces was investigated using κ-carrageenan gel and agar gel, which can be used as metal ion extractors.

(Examples 71 and 72: Preparation of metal ion extraction part 1)
0.2 g of κ-carrageenan was dissolved in 19.98 ml of ultrapure water while heating on a hot plate. 20 μl of 1 M potassium chloride solution was added dropwise while stirring, and hydrochloric acid was added to adjust the pH to 1.5. 10 ml of this sol was placed in a plastic petri dish, cooled in a refrigerator, and gelled. The gelatin gel was then cut into 3 x 3 mm pieces. After wiping the gel with a Kimwipe, the pH was measured using an ISFET electrode. The pH of the gel was 1.543.

(Examples 71 and 72: Confirmation of Metal Ion Elution 1)
κ-carrageenan gel was contacted with metallic tin polished with a file for 30 and 180 seconds, and then wet-decomposed using concentrated nitric acid. As a comparative example, κ-carrageenan gel not contacted with metallic tin was also wet-decomposed using concentrated nitric acid (Comparative Example 70). After evaporating the concentrated nitric acid to near dryness, 20 ml of 1 M hydrochloric acid was added to prepare a sample solution, which was then analyzed for tin using ICP-OES. As a result, 3.34 × 10 ^-9 mol of tin was extracted into a 3 × 3 mm gel after 30 seconds of contact with metallic tin, and 5.91 × 10 ^-9 mol after 180 seconds of contact. No tin was detected in the gel that had not been contacted.

(Examples 73 and 74: Preparation of metal ion extraction part 2)
The agar was adjusted to a concentration of 20 g/L and a pH of 2. 10 ml of this sol was placed in a plastic petri dish, cooled in a refrigerator to gel, and cut into 3 x 3 mm pieces. The gelatin gel was wiped with a Kimwipe and then the pH was measured using an ISFET electrode. The pH of the gel was 2.00.

(Examples 73 and 74: Confirmation of Metal Ion Elution 2)
The gel was contacted with a 100-yen coin for 30 and 60 seconds and then subjected to wet decomposition using concentrated nitric acid. After evaporating the concentrated nitric acid until it was almost dry, 20 ml of a pH 2.0 nitric acid solution was added to prepare a sample solution, and the nickel contained in the 100-yen coin was analyzed using ICP-OES. As a result, 3.71 x ^10-10 mol of nickel was extracted into a 3 x 3 mm gel after 30 seconds of contact with the 100-yen coin, and 8.28 x ^10-10 mol after 60 seconds of contact.

It was found that carrageenan gel and agar gel (acidic aqueous gels) can dissolve and extract metal ions from solid surfaces, and can be used as the metal ion extraction portion of a touch test device.

(Examples 81 and 82: Overview)
Hydrogels with a network structure (Interpenetrating Polymer Network: IPN) in which different crosslinked polymers interpenetrate (IPN) (IPN hydrogels) have high water retention properties due to the ability to hold water in the network structure, forming a gel with high mechanical strength. Therefore, we investigated their behavior as metal ion extraction sites. The investigation was carried out on two hydrogels: a PVA-itaconic acid IPN hydrogel, in which polyvinyl alcohol (PVA) and itaconic acid polymerized with the crosslinker N,N'-methylenebisacrylamide and polymerization initiator ammonium persulfate were entangled, and a CMC-starch IPN hydrogel, in which carboxymethylcellulose (CMC) and starch crosslinked with calcium ions were entangled.

(Example 81: Preparation of touch test device 1)
0.15 g of PVA was dissolved in 5 ml of ultrapure water, and 2.07 g of itaconic acid and 0.16 g of MBA were added, followed by the addition of 0.02 g of ammonium persulfate and stirring. This solution was then dip-coated in the same manner as in Example 51 onto a detection material having 3,5-diBrPADAP nanoparticles as the detection unit, which was a porous cellulose membrane filter (pore size 0.10 μm). The material was then polymerized in an oven at 80°C to produce an integrated touch test device with an IPN hydrogel on top.

(Example 82: Preparation of touch test device 2)
CMC and sweet potato starch were dissolved in ultrapure water, stirred, and poured into a petri dish. The mixture was heated in an 80°C water bath for 1.5 minutes, then cooled in a water bath for 30 minutes. Calcium chloride solution was added and allowed to gel for 24 hours. The final concentrations were adjusted to 1.14 wt% CMC, 13.1 wt% sweet potato starch, 85.7 wt% ultrapure water, and 0.06 wt% calcium chloride. The solidified gel was cut out from the mold and placed on the detection material to create a gel-integrated touch test device.

(Comparative Example 80: Detecting material without metal ion extraction part)
A detection material without IPN hydrogel was used as a control, and the artificial sweat of Example 61 was impregnated into a detection material without IPN hydrogel, and the material was allowed to come into contact with a 100 yen coin for 3 minutes.

(Examples 81 and 82, Comparative Example 80: Detection of Metal Ions)
The detection materials with PVA-itaconic acid IPN hydrogel and CMC-starch IPN hydrogel in the metal ion extraction section showed a purple color in the detection area, but the control detection material without IPN hydrogel showed an orange color in the detection area and no color reaction occurred, indicating that the IPN hydrogel was functioning as a metal ion extraction section.

(Comparative Example 90: Overview)
To investigate the role of the metal ion extraction part, the detection behavior without gelatin gel was investigated in the contact analysis of solid metallic tin using a detection material with a dithizone nanofiber membrane as the detection part.

(Comparative Example 90: Preparation of detection unit)
It was produced in accordance with Example 11.

(Comparative Example 90: Contact with Metal Surface)
A part of the detection unit was used as a metal ion supply unit. The metal ion supply unit was directly contacted with metallic tin, wrapped in parafilm, and left for 30 minutes. The reflection/absorption spectrum of the metal ion supply unit was measured using a colorimeter before and after contact. The results are shown in Figure 18.

(Comparative Example 90: Detection of Metal Ions)
As shown in Figure 18, when there was no gel (metal ion extraction part), no color change was observed in the detection part when metal contacted the metal ion supply part. This indicates that tin ions were not eluted and therefore did not react with dithizone in the detection part.

(Examples 101 to 103: Overview)
Contact analysis of zinc was carried out on a 500 yen coin using a touch test device with pyridylazoresorcinol nanoparticles as the detection element.

(Examples 101 to 103: Preparation of touch test device)
An immunomembrane was used as the porous body. 100 μl of 3 mM pyridylazoresorcinol (PAN) pigment was injected into 10 ml of ultrapure water stirred at 1000 rpm and allowed to stand for 1 minute to produce a nanoparticle dispersion. A PAN nanoparticle thin film was formed on the immunomembrane. After drying, the PAN nanoparticle thin film was cut to a width of 3 mm to form a yellow detection area, and a touch test device was produced using the immunomembrane as a porous body. The gel was prepared in accordance with Example 11. The pH of the gelatin gel was 2.00.

(Examples 101 to 103: Detection of metal ions)
In the gel separation type, the gel was contacted with a 500-yen coin for 20 seconds, and then detection was performed using three detection fluids: 0.025 mol/kg neutral phosphate pH buffer solution (pH 6.86), 0.05 mol/kg phthalate pH buffer solution (pH 4.01), and 0.01 mol/kg borate pH buffer solution (pH 9.18). The detection fluid was stopped when the solvent front reached a point 25 mm from the end of the metal ion supply section.
The detection fluid was supplied from the water supply unit, and when the pH was 4.01, 6.86, and 9.18, the test times were 1 minute 31 seconds, 1 minute 30 seconds, and 1 minute 38 seconds, respectively, with an average of 1 minute 33 seconds.

(Examples 101 to 103: Determination of metal ions)
In the metal ion extraction section, extraction of zinc(II) ions from the 500 yen coin progressed, and a red color appeared due to the formation of a Zn(II)-PAN complex. The coloration distance was long at pH 6.86 and 9.18, and short at pH 4.01. This correlates with the pH at which the Zn(II)-PAN complex forms. Furthermore, the immunomembrane, which is a porous material, is a lateral flow material, with a distance of 25 mm taking approximately one and a half minutes, making detection possible even in this case.

(Examples 111 and 112, Comparative Example 110: Overview)
The contact analysis of an iron plate was carried out using a gel separation type touch test device in which organic colorimetric reagent particles consisting of a dye and a particle forming agent were used as the detection element.

(Examples 111 and 112, Comparative Example 110: Preparation of Detection Unit)
To 10 ml of ultrapure water, 100 μl of 2 mM bathophenanthroline disulfonic acid (Bath-s) dye and 100 μl of trimethylaminated latex nanoparticles (average 100 nm, 25 mg/ml) as a microparticle forming agent were added, and the mixture was shaken for 2 minutes. The anionic Bath-s was electrostatically adsorbed onto the positively charged latex nanoparticles, inducing aggregation and forming a Bath-s/LatexN(CH3)3 nanocomposite thin film on the immunomembrane. After drying, the Bath-s/LatexN(CH3)3 nanocomposite thin film was cut to a width of 3 mm, resulting in a colorless detection section, and a touch test device was fabricated using the immunomembrane as a porous body.

(Examples 111 and 112, Comparative Example 110: Preparation of Metal Ion Extraction Unit)
0.1 M of the ionizing agent L-ascorbic acid was dissolved in a 50 g/L solution of bovine bone-derived gelatin. 10 ml of this solution was added to a plastic petri dish, cooled in a refrigerator, and then cut into 3 x 3 mm pieces to produce a gel containing artificial sweat and thiourea as a masking agent. After wiping the gel with a Kimwipe, the pH was measured using an ISFET electrode. The pH of the gel was 3.557.

(Examples 111 and 112, Comparative Example 110: Detection of Metal Ions)
As in Example 11, the touch test device was attached and fixed to a plastic plate with double-sided tape. The cut gelatin was then brought into contact with an iron plate and placed on the metal ion supply unit (detection unit) so that the contacted surface was in contact with the detection unit. 0.1 M citrate buffer (pH 3.0) was applied from the water supply unit as the detection fluid. The contact time with the iron plate was 60 seconds (Comparative Example 110), 180 seconds (Example 111), and 600 seconds (Example 112). The citrate buffer is a sensitivity enhancer for color development at the optimal pH. Because an immunomembrane with a lateral flow time of 180 seconds was used to advance 40 mm, the time required to advance 25 mm from the end of the metal ion supply unit was 1 minute 30 seconds. Since the detection unit was transparent, the detection fluid was stopped after 1 minute 30 seconds of flowing the detection fluid, not the solvent front. The colored area turned red.

(Examples 111 and 112, Comparative Example 110: Determination of Metal Ions)
Data was scanned and analyzed as RGB values using ImageJ in the same manner as in Example 21. As a result, no coloration was observed at 60 seconds, the coloration distance was 0.41 cm at 180 seconds, S _R 1034, S _G 894, S _B 966, and at 600 seconds, S _R 1059, S _G 763, S _B 865.
Bath-s is known to react specifically with Fe(II) ions only, forming a red complex. The iron on the surface of the iron plate is oxidized, and by contacting this surface with the metal ion extraction unit, the Fe(II) ions are dissolved by the L-ascorbic acid, a reducing agent and acid contained in the iron plate, and are detected as a red Fe(II)-Bath-s complex in the detection unit of the Bath-s/LatexN( _CH3 ) ₃ nanocomposite thin film. However, because the surface of the iron plate is oxidized, a sufficient amount could not be extracted with 60 seconds of contact, and it is thought that the coloration distance did not increase. The red color became stronger as the contact time increased.

(Comparative Examples 121 to 124: Overview)
In order to compare with the flow pattern of the detection fluid, that is, the lateral flow, which is a unidirectional flow, the detection fluid was measured as a concentric flow.

(Comparative Examples 121 to 124: Preparation of Touch Test Devices)
Using a detection material in which a dithizone nano-thin film prepared in accordance with Example 11 was used as the detection portion and the porous body was formed into a circular shape rather than a rod shape, a detection fluid was supplied to a touch test device with a combined ion supply and water supply, and solid metallic tin was analyzed.

(Comparative Examples 121 to 124: Detection of Metal Ions)
The extraction and supply of metal ions using the touch test device was carried out in the same manner as in Example 11, and the extraction of metal ions was carried out using a gel separation method. The pH of the gel was 2.023.
After contacting the cut gelatin with the metal tin for 30, 60, 180, and 600 seconds, the gelatin was placed in the center of the circular detector so that the contacted surface was in contact with the metal ion supply unit (detection unit) and left for 10 minutes. After leaving the gel in the center for 10 minutes, a pink color spread concentrically from the gel in the center.

(Comparative Examples 121 to 124: Determination of Metal Ions)
The images were processed with ImageJ in accordance with Example 21. The radius r (colored distance) from the colored area of a circle, with the center of the gel set to 0, the solvent front, Rf value, and colored area ( _SR , _SG , _SB ) are shown in Table 9. The relationship between contact time and colored area _SR is also shown in Figure 19.

Table 9 and Figure 19 show that the colored distance and colored area decrease as the contact time increases. This phenomenon is not seen in Example 11, etc., and indicates a narrow measurable range (dynamic range).

(Example 131, Comparative Example 130: Overview)
In order to demonstrate the necessity of the detection unit being composed of organic colorimetric reagent particles and being placed on the surface of the porous body, a filter paper (impregnated filter paper) in which the organic colorimetric reagent was impregnated and dispersed as molecules in the porous body was prepared as a comparative example, and the detection characteristics were compared. The touch test device was prepared in accordance with Example 11.

(Comparative Example 130: Preparation of Impregnated Filter Paper)
The porous material impregnated with the organic colorimetric reagent was prepared by placing a 3 x 40 mm piece of filter paper (5C filter paper) on a plastic plate, absorbing 20 μl of 1.25 mM dithizone acetone solution in four separate aliquots (5 μl each) from one end of the filter paper to the other, and then drying the acetone. The amount of dithizone held in this impregnated filter paper was adjusted to be the same as that of the touch test device in Example 11.

(Example 131, Comparative Example 130: Preparation of metal ion extraction unit)
The gelatin for the metal ion extraction part was prepared in accordance with Example 11.

(Example 131, Comparative Example 130: Detection of Metal Ions)
After contacting gelatin (pH 2.036) with metal tin for 10 minutes, it was placed on the touch test device and impregnated filter paper, and then placed on the metal ion supply unit (detection unit) so that the contacting surface was in contact with the detection unit. A hydrochloric acid solution with a pH of 2.0 was introduced from the water supply unit as the detection fluid, and when the solvent flow had developed up to a 25 mm section, it was cut with ceramic scissors to stop the flow.

(Example 131, Comparative Example 130: Determination of Metal Ions)
After development and color development, the images were scanned and processed using the color analysis software imageJ. RGB analysis was performed on a rectangle measuring 2 x 35 mm.
A scanned photograph of the front surface of the touch test device and its analysis by ImageJ are shown in Figure 20, and a scanned photograph of the back surface and its analysis by ImageJ are shown in Figure 21. A scanned photograph of the impregnated filter paper and its analysis by ImageJ are shown in Figure 22, and a scanned photograph of the back surface and its analysis by ImageJ are shown in Figure 23.

Before detection, the touch test device and impregnated filter paper were a dark blue-gray color, with dithizone particles present only on the surface in a thin film, invisible from the back. The latter, however, was paler in color from above and the same color on the back, indicating that dithizone molecules were dispersed throughout the entire thickness of the filter paper. After detection, the touch test device displayed a clearly visible pink colored area only on the surface, similar to the detection area, with a clear increase in the R value (Figure 20). The color was invisible from the back (Figure 21). On the impregnated filter paper, color was present on both the surface (Figure 22) and back (Figure 23), and the signal was faint. The change in R value due to the pink coloration indicates that the touch test device had a clear and strong boundary between the detection and colored areas, making it easy to determine their length and area. On the other hand, the boundary on the impregnated filter paper was unclear, making it difficult to determine their length and area, demonstrating its unsuitability for metal analysis on solid surfaces. The colored length was also 21.7 mm for the touch test device and 7.7 mm for the impregnated filter paper. With impregnated filter paper, the reagents are dispersed molecularly in the thickness direction of the filter paper, which means the signal also disperses in the thickness direction, making quantification difficult. With the touch test device, all of the target metal ions are present in the thin film as fine particles, meaning that the signal does not disperse in the thickness direction, resulting in higher sensitivity and a wider quantification range.

The present invention is useful for rapid solid surface analysis without relying on instrumental analysis and can be used for routine on-site analysis of metal components on solid surfaces.

DESCRIPTION OF SYMBOLS 1. Detection material 2. Detection system 10. Detection section 11. Coloring section 12. Solvent front 20. Metal ion supply section 30. Water supply section 40. Porous body 50. Metal ion extraction section 60. Determination section

Claims (7)

A detection material for detecting metal components on a solid surface, comprising a sheet-like porous body, a detection unit, a metal ion extraction unit, a metal ion supply unit, and a water supply unit,
the detection unit has organic colorimetric reagent particles and is disposed on the surface of the porous body;
the metal ion extraction unit includes a gel having an ionization component that ionizes metal components on the solid surface;
the metal ion supply unit is disposed on the surface of the porous body so as to be at least partially in contact with the detection unit, and
the metal ion extraction unit is disposed in contact with an upper surface of the metal ion supply unit, and the metal ions ionized by the ionization component are supplied from the metal ion extraction unit to the metal ion supply unit by the driving force generated when the detection fluid contacts the metal ion supply unit ; and
the detection fluid flows from the water supply section through the metal ion supply section to the detection section, and the metal ions from the metal ion supply section are diffused into the detection section;
The water supply section is disposed on one end side of the porous body,
the porous body has a structure in which the detection fluid flows through the porous body from the water supply portion toward the end opposite the water supply portion by capillary action,
the metal ions diffused from the metal ion supply unit to the detection unit by the detection fluid react with the organic colorimetric reagent microparticles to produce a color;
A detection material characterized by: The detection unit includes a wetting agent.
The detecting material according to claim 1 . The metal ion extraction unit includes an extraction enhancer.
The detecting material according to claim 1 . The metal ion supply unit and the water supply unit are the same.
The detecting material according to claim 1 . the detection fluid includes a sensitivity enhancer;
The detecting material according to claim 1 . A detection system for detecting metal components on a solid surface using the detection material according to claim 1,
a determination unit capable of determining at least one of the type of the metal ion and the amount of elution of the metal ion based on the color developed by the color reaction,
A detection system comprising: A method for detecting metal components on a solid surface, comprising:
a detection unit having organic colorimetric reagent particles and disposed on the surface of the porous body;
a metal ion extraction unit including a gel having an ionization component that ionizes metal components on the solid surface;
a metal ion supply unit disposed on the surface of the porous body so as to be at least partially in contact with the detection unit;
The metal ions ionized by the ionization component are supplied from the metal ion extraction unit to a metal ion supply unit ,
A water supply section disposed on one end side of the porous body;
A detection material having a porous body having a structure in which a detection fluid flows through the porous body from the water supply portion toward the end opposite the water supply portion by capillary action,
a contacting step of contacting the metal ion extraction unit with the solid surface;
a supply step in which the metal ion extraction unit comes into contact with an upper surface of the metal ion supply unit, and the contact between the detection fluid and the metal ion supply unit serves as a driving force to supply the metal ions to the metal ion supply unit;
a diffusion step of flowing the detection fluid from the water supply unit and diffusing the metal ions from the metal ion supply unit to the detection unit by the detection fluid flowing from the water supply unit through the metal ion supply unit to the detection unit;
a reaction step in which the metal ions react with the organic colorimetric reagent microparticles to produce a color;
a determination step of determining at least one of the type of the metal ions and the amount of elution of the metal ions based on the color developed by the color reaction;
A detection method comprising: