JPH02124467A - Multilayered analyzing element - Google Patents

Abstract

PURPOSE:To make it possible to measure specified ions in a fluid specimen with good reproducibility by a colorimetric method by incorporating the fine particles of hydrophobic vehicle incorporating a reporter material wherein a reagent layer mutually reacts with ionophore and the complex of ionophore and ions and a detectable response is shown and an anion based surface active agent. CONSTITUTION:A reagent layer incorporating a hydrophilic binder is laminated on a supporting body. A porous developing layer is laminated thereon. As the supporting body, cellulose acetate is suitable. It is advantageous to use gelatin for the hydrophilic binder. Ionophore incorporates molecules which can form a complex selectively with specified ions. For example, valinomycin is bonded to K ions in solution and forms the cation complex. As an anion based surface active agent, fluoro-alkyl sulfonates are desirable. The method for introducing fine grains into the reagent layer is as follows: the grains are dissolved in the single solution or the mixed solution of an organic solvent whose boiling point is 175 deg.C for higher under 1 atmospheric pressure and an organic solvent whose boiling point is 50 - 160 deg.C; and thereafter the grains are finely dispersed in hydrophilic colloid under the presence of anion based surface active agent.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a multilayer analytical element for measuring ions, particularly ions in an aqueous solution, and further relates to a multilayer analytical element for measuring ions in biological fluids, such as blood (
The present invention relates to a multilayer analytical element that is particularly useful for clinical diagnosis and performs qualitative and routine analysis of ions in components of whole blood, plasma, serum), urine, etc.

BACKGROUND ART Conventionally, ions in aqueous solutions, particularly blood electrolytes, etc., have been measured by a flame method, a coulometric titration method, or an ion-selective electrode method. The flame method and coulometric titration method require troublesome equipment maintenance and post-measurement processing, making them unsuitable for constant or immediate testing.In the ion-selective three-electrode method, the ion-selective membrane deteriorates due to repeated use, making it difficult to test the sample. Both measurement methods had problems as immediate tests, such as a large dilution error when measuring after dilution. On the other hand, as described in JP-A-52-142584, a multilayer film using an ion-selective membrane uses a disposable dry ion-selective electrode, so the ion-selective membrane can be used repeatedly. There is no need to worry about deterioration due to Although this electrode film is improved in the speed and simplicity of measurement, it suffers from fluctuations in potential during measurement, is complicated in the design and manufacture of the electrode film, requires strict manufacturing control, and is therefore difficult and costly to manufacture. It gets expensive. In addition, in clinical chemistry tests, it is measured together with ions such as Ni+ and Na+ in serum and plasma, along with proteins, sugars, lipids, and enzymes that coexist, and a diagnosis is made from the comprehensive data thereof. However, for quantitative analysis of components other than ions, colorimetric analysis is used and a spectrophotometer is used. However, since the measurement principle is different in the quantitative analysis of ions using the dry ion-selective electrode, a dedicated separate measurement method is required. The problem was that it required a machine and was expensive.

JP-A No. 59-211864, No. 59-212456
No. 59-231452 discloses ionophores capable of forming complexes with ions, and detectable substances such as color or fluorescence changes that interact with ionophore-ion complexes. An aqueous carrier containing microspheres of a hydrophobic vehicle containing a reporter substance capable of producing a response.
A method for quantifying ions in an aqueous solution by colorimetric analysis is described.

[Problem to be solved by the invention]

In this method, ions in serum and plasma can be colorimetrically determined in the same manner as other components, but the ionophore and reporter substance often have low solubility in the hydrophobic vehicle. For this reason, it is difficult to obtain a uniform composition with the test device, and as a result, quantification of ions using this test device has problems in reproducibility and storage stability.

The purpose of the present invention is to be able to perform quantitative analysis using a colorimetric method, with high accuracy and
An object of the present invention is to provide a multilayer analytical element for measuring specific ions in a fluid sample with improved reproducibility and storage stability.

[Means to solve the problem]

To summarize the present invention, the present invention relates to a multilayer analytical element, in which a reagent layer containing a hydrophilic binder is laminated on a support, and a porous spreading layer is laminated above the reagent layer. The reagent layer contains (a) an ionophore capable of forming a complex with ions, (l) a reporter substance that interacts with the ionophore-ion complex and exhibits a detectable response, and (c) an anionic surfactant. It is characterized by containing fine particles of a hydrophobic vehicle.

The support according to the invention can be of any type as long as it is light-transparent and liquid-impermeable, but various polymeric materials, such as cellulose acetate, polyethylene terephthalate, polycarbonate or polystyrene, can be used for this purpose. suitable for

In addition to the polymer materials mentioned above, inorganic materials such as glass can be used as well.

Although the thickness of the support according to the present invention is arbitrary, it is preferably 50 to 250/Pm. Further, one side surface of the observation side of the support according to the present invention can be arbitrarily processed depending on the purpose. Furthermore, it is possible to improve the adhesion between the reagent layer and the support by using a light-transmitting undercoat layer on the side of the support on which the reagent layer is laminated, depending on the case.

The hydrophilic binder according to the present invention includes a substance that binds or absorbs water, and swells with water or forms a reversible gel, or is permeable to water. Specifically, gelatin is used as the hydrophilic binder. Although advantageous, other hydrophilic colloids can be used.

For example, proteins such as gelatin derivatives, graft polymers of gelatin and other polymers, albumin, and casein;
Cellulose derivatives such as hydroxyethylcellulose, carboxymethylcellulose, and cellulose sulfate esters; sugar derivatives such as sodium alginate and starch derivatives; polyvinyl alcohol, polyvinyl alcohol partial acetal, poly-N-vinylpyrrolidone, polyacrylic acid, and A wide variety of synthetic hydrophilic polymeric materials can be used, such as single or copolymers of methacrylic acid, polyacrylamide, polyvinylimidazole, polyvinylpyrazole, and the like.

Examples of gelatin include lime-processed gelatin, acid-processed gelatin, and gelatin.
Japan (But!

Enzyme-treated gelatin as described in Soc, Sci, Phot, Japan) No. 16, page 30 (191″J6) may be used, and gelatin hydrolysates and enzymatically decomposed products may also be used. As gelatin derivatives, various compounds such as acid halides, acid anhydrides, incyanates, bromoacetic acids, alkanesultones, vinyl sulfonamides, maleimide compounds, polyalkylene oxides, and epoxy compounds are reacted with gelatin. The one obtained by doing so is used.

The reagent layer of the present invention has 1-51 properties such as improved dimension stability.
It can contain a dispersion of a water-insoluble or sparingly soluble synthetic polymer. For example, alkyl (meth)acrylates, alkoxyalkyl (meth)acrylates, glycidyl (meth)acrylates, (meth)acrylamide', vinylcostyl (e.g. vinyl acetate), acrylonitrile, olefins, styrene, etc. alone or in combination, or these and acrylics. Acid, methacrylic acid, alpha.

A polymer containing a combination of β-unsaturated dicarboxylic acid, maleic anhydride, hydroxyalkyl (meth)acrylate, sulfoalkyl (meth)acrylate, styrene sulfonic acid, etc. as a monomer component can be used.

An inorganic or organic hardening agent may be included in the reagent comprising the hydrophilic colloid. Specific examples include chromium salts, aldehydes (formaldehyde, glyoxal, glutaraldehyde, etc.), and N-methylol compounds (dimethylol urea, etc.). Active halogen compound (2,4-dichloro-6-hydroxy-
1. 3. 5-1-IJ azine, etc.) and active vinyl compounds [1.3-bisvinylsulfonyl-2-
propatool, 1,2-bisvinylsulfonylacetamidoethane, ■,2-bis(vinylsulfonyl)conicne, or vinylsulfonyl≦11゛j.
vinyl polymers, etc.] are preferred because they quickly harden hydrophilic colloids such as gelatin. N-carbamoylpyridinium, salt Efi, and haloamidinium salts also have a fast curing speed.

Ionophores of the present invention include molecules capable of selectively forming complexes with specific ions to the substantial exclusion of other ions. For example, palinomycin, a cyclic polypeptide, selectively binds to potassium ions in solution to form a cationic complex. These also include crown ethers, cryptands and buttonds.

Coronalands are monocyclic compounds that contain donor atoms that are electron-rich or electron-deficient and, because of their specific structure, can form complexes with certain cations and anions. can. The coronand class has its monocyclic i
Crown needles in which 'a''i contains oxygen as a pentavalent atom are included.

Other coronands are compounds containing a combination of electron-rich atoms such as oxygen, sulfur, and nitrogen. Due to the unique size and geometry of certain coronands, they are applicable to complex formation with a variety of ions. In such complex formation, electron-rich atoms, such as oxygen in crown ethers, orient toward electron-poor protons. The carbon atom segments of the atomic chain simultaneously project outward from the ion.

The complex thus obtained has a charge in its center, but is hydrophobic at its periphery.

Cryptands are polycyclic analogs of coronands. They therefore include bicyclic and tricyclic polydentate compounds. In cryptands, the cyclic arrangement of the donor atoms is three-dimensional in space, as opposed to the substantially planar arrangement of coronands. Cryptands can virtually envelop ions in a three-dimensional manner and therefore can bind ions strongly in the formation of complexes.

As with coronands, donating atoms can include atoms such as oxygen, sulfur and nitrogen.

Buttonds are linear chains containing a regular series of atoms, such as oxygen, and are not completely different from coronands and cryptands, and have the ability to combine with positively charged ions to form complexes. have Buttons and other 2
The main structural difference between the two ionophores is their ring opening.

Therefore, buttoneds are classified into monobuttons, dibuttons, tributtons, etc.

Monobuttons are a single organic chain containing a donating atom, dibuttons are chains of two such atoms attached to a central atom or group of atoms, and can vary in spatial orientation; tributonds is a chain of three such atoms.

Examples of ionophores useful in the present invention are shown below.

palinomycin nonactin 1 Na + 12-crown-4 15-crown-5 18-crown-6 l Na", 1 K" dibenzo-18-crown-6K ÷ dicyclohexanor 18-crown-6 to 1 [Ryptofix is a product of E-Merck,
Darmstad Germany (B, Merck Darms-
tast, registered trademark of Gera+any)] Reporter substances of the present invention are those in which the ion of interest is present in the test solution and which exhibits a detectable response as a result of interaction with the ionophore/ion complex. .

The ionophore is preferably 5. OX 1 mouth 4-2, O
It is contained in the analytical element in an amount of 102mM/m2.

Reporter substances can range in composition from compounds such as chromogenic reactive ions to mixtures of opposite species that produce a detectable product when the opposite chain is induced by a complex. . Therefore, in the absence of the ion of interest, the reporter substance remains unchanged and no detectable response is observed.

If the reporter substance is a single compound, the reporter may include a salt or a dissociable compound, which upon dissociation produces a colored ionic species. Depending on the charge of the analyte ion,
Ionic reporters are selected such that the colored ions are of opposite charge to the analyte.

Dissociative compounds whose counterion to the analyte is fluorescent can also be used as reporter substances. Such chromophore and fluorophore reporter substances include, for example, 2,6-dichloroindophenol, fluorescein and its derivatives, 8-anilino-1-naphthalenesulfonic acid, 7-amino-4-trifluoromethylcoumarin, erythrosin 81 orange. ■v1 phloxine 81 and iosin Y are mentioned.

Furthermore, iodide ions, starch, and oxidizing agents may be used.

Preferred reporter substances include compounds represented by the following general formulas (1) and (II).

General formula (wherein, A substituent at the 2-position, 3-position, 5-position and/or 6-position selected from n=0 to 4.) General formula (■) 1B (wherein R1 is H or a lower alkyl group, R2 is I]
or an intermediate alkyl group, and X is a halogen or pseudohalogen) Pseudohalogen as used in the present invention refers to the electrophilicity of this ring system when bonded to an unsaturated or aromatic system in a manner similar to halogens. or a group of atoms that affects the nucleophilicity and/or influences the charge distribution by delocalization or resonance.

For example -CN, -3CN, -0CN, -N,
, -(:OR, -[:00RCU N II R, -C
F 3, -CC13, -NO2, -3O21: l bow, 5
r12C113 and -3O2Ca11. Groups such as Cl43 (wherein I is an alkyl or aryl group) are included. These compounds are disclosed in Japanese Patent Application Laid-Open No. 59-21245.
It is described in detail in Publication No. 6.

Reporter substances of preferred structure are compounds of general formula (n), which are resistant to interference caused by the presence of proteins such as serum albumin in the test solution.

A more preferred reporter substance of this type is R'
is methyl, R2 is n-decyl, and X is CI,
7-(n-decyl)-2-methyl, (3+5'-dichlorophen-4'-one) indonaphthol. These compounds are described in detail in JP-A-59-212456.

Hydrophobic vehicle according to the present invention means a substance that allows isolation of ionophore and reporter substance from a hydrophilic binder. The hydrophobic vehicle may be solid or liquid, or a combination thereof, as long as it has the ability to coexist the ionophore, ionophore/ion complex, and reporter substance in the microparticles. Preferably it is a liquid.

If solid, it can be comprised of hydrophobic materials such as organic polymers that are substantially non-porous and non-polar. Specifically, polyvinyl fluoride, polyvinyl chloride, vinyl chloride/vinyl acetate copolymer, vinyl chloride/i[2vinyl/
Examples include fine particles (spheres) of polyvinyl polymers such as vinyl alcohol terpolymers and vinylidene chloride/acrylonitrile copolymers.

In the case of a liquid, an organic solvent is preferable, and the ionophore and reporter substance are uniformly dissolved in the organic solvent and present as fine particles in the reagent layer. As a method for introducing the fine particles into the reagent layer, an oil droplet dispersion method in ice is preferred.

In the oil-in-ice dispersion method, the anionic system of the present invention is dissolved in either a high-boiling organic solvent with a boiling point of 175° C. or higher under 1 atm and a so-called auxiliary solvent with a low boiling point, either alone or in a mixture of the two. Finely dispersed in an aqueous medium such as a hydrophilic colloid in the presence of a surfactant.

Examples of high boiling point organic solvents are described in U.S. Pat. No. 2,322,027 and elsewhere. Dispersion may involve phase inversion, and is usually emulsified and dispersed using a dispersion means such as a stirrer, homogenizer, colloid mill, flow jet mixer, or ultrasonic device. At the same time as dispersion, the low boiling point organic solvent may be removed or reduced by distillation, noodle washing, or ultrafiltration before use for coating.

Specific examples of high-boiling organic solvents include phthalate esters (dibutyl phthalate, dicyclohexyl phthalate,
esters of phosphoric acid or phosphonic acid (triphenyl phosphate, tricresyl phosphate, 2-ethylhexyl phthalate, decyl phthalate, etc.)
Ethylhexyl diphenyl phosphate, tricyclohexyl phosphate, tri-2-ethylhexyl phosphate, tridodecyl phosphate, tributoxyethyl phosphate, tricyclohexyl phosphate,
di-2-ethylhexylphenylphosphonate, etc.),
Benzoic acid esters (2-ethylhexylbenzoate, dodecylbenzoate, 2-ethylhexyl-p-hydroxybenzoate, etc.) Amides (diethyldodecanamide, N-tetradecylpyrrolidone, etc.) Alcohols or phenols (isostearyl alcohol, etc.) , 2.4-di-tert-amylphenol, etc.), aliphatic carboxylic acid esters (dioctyl azelate, glycerol tributyrate, isostearyl lactate, trioctyl citrate, etc.), aniline derivatives (N,
N-dibutyl-2-butoxy-5-tert-octylaniline, etc.), hydrocarbons (halafine, dodecylbenzene, diisopropylnaphthalene, etc.), phenyl ethers (2-nitrophenyl octyl ether, 2-nitrophenylbutyl ether, etc.), etc. can be mentioned. Among these, phenyl ethers are preferred. In addition, as an auxiliary solvent, the boiling point at 1 atmosphere is 5
Organic solvents with a low boiling point of 0° C. to 160° C. can be used, and typical examples include ethyl acetate, butyl acetate, ethyl propionate, methyl ethyl ketone, cyclohexanone, 2-ethoxyethyl acetate, dimethylformamide, and the like. Among these, ethyl acetate is preferred.

Examples of the anionic surfactant of the present invention added during the emulsification and dispersion include higher alcohol (Ca-C22) sulfate ester salts [e.g., sodium salt of lauryl alcohol sulfate, sodium salt of octyl alcohol sulfate, lauryl alcohol Ammonium salts of sulfates, "T-Ball B-81J (trade name, Shell Chemical Co., Ltd.), disodium alkyl sulfate, etc.", fatty alcohol phosphate ester salts (e.g.,
sodium salt of heptyl alcohol phosphate, etc.)
Alkylaryl sulfonic acid salts (e.g., dodecylbenzenesulfonic acid sodium salt, isopropylnaphthalene sulfonic acid sodium salt, sinapthalenedisulfonic acid sodium salt, metanitrobenzene sulfonic acid sodium salt, etc.) Alkylamide sulfonate salts (e.g., C271t) -5CONCIlzCII-3O-Na, etc.), sulfonic acid salts of dibasic fatty acid C11゜Nisdel (e.g., sodium sulfosuccinate dioctyl ester, sodium sulfosuccinate dihexyl ester, etc.), alkyl sulfonates (e.g., tetraethylammonium salt of octanesulfonic acid) etc.) °r Delul phosphonate, alkyl phosphinate, alkyl phosphate ester salt, alkylphenyl ether phosphate ester salt, and the like.

Furthermore, fluorine-based surfactants in which some or all of the hydrogen atoms in the alkyl/tolu groups of the surfactants listed above are replaced with fluorine can also be used. Among these, sulfonate salts are preferred, and fluoroalkyl sulfonate salts are more preferred.

Fourthly, the anionic surfactant of the present invention is preferably a salt whose counter ion is an ion other than the same or similar ion species as the ion to be analyzed. For example, when the object to be analyzed is sodium ions, the ions are ions other than the four ions (for example, Ni'', Ill+, etc.) in alkali gold containing sodium.

Ammonium salts are preferred.

The anionic surfactant of the present invention has a ratio of 5% to the area of the support in the multilayer analytical element of the present invention. Ox l O-2g
/m' ~5. Preferably, the content is 0 g/m2. More preferably, 1. Ox 10-'g/m2~
It is 1.0g/m2.

When the reagent layer according to the present invention is coated on a support, it is preferable to adjust the coating solution to a pu5 to IO range with a buffer.

Suitable buffers include bis[2-hyI-' D =1-diethylkoimino-tris[hydroxymethylcomethane,
1.3 -Hydros[Tris (hydroni-1-dimethyl)]
Methyl(mino)propane, N,N-bis(2hydroxyethyl)glycine, tris(hydroxymethyl)aminomethane, N-C2-acetomido]-2-iminodiacetic acid, N-2-human[1xethyl piperazine-N13-
Included are propanesulfonic acid, ]-[N-)lis(hydroxymethyl)methylamino-2-hydroxypropanesulfonic acid, tetramethylammonium borate, and detramethylammonium phosphate.

The preferred pt+ range depends on the reporter substance, and thus the choice of buffer will be determined by the reporter substance used and, to some extent, by the desired detectable response.

The thickness of the reagent layer F is 5 to 100Fr8, preferably 1
0 to 60/, -. In addition, the reagent layer may have two layers depending on the case.
It can also consist of two layers.

The porous spreading layer according to the present invention is, for example,
A spread layer of a non-fibrous porous medium such as a plush polymer and microcrystalline cellulose described in JP-A No. 677, JP-A-5
5-1 (Developed layer of parent, water-treated fabrics described in I4356, 51-66359, etc., JP-A-57-371-658, JP-A-57-125847);
, No. 57197466 and No. 58-70161, etc., fiber structure development layer, 1S Kaisho 58-90
An example is the particle combination structure development layer described in Japanese Patent No. 167.

The thickness of the porous spreading layer according to the present invention should be determined by its porosity, but is preferably about 100 to about 6
00/Ml, more preferably about 150 to about 400. Further, the porosity is preferably about 20 to about 85%.

In addition, a surfactant can be added to the porous spreading layer according to the present invention to adjust the rate of penetration into the reagent layer when a fluid sample is applied to the multilayer analytical element according to the present invention.

As the surfactant, it is possible to use either ionic (anionic or cationic) or nonionic surfactants, but nonionic surfactants are effective. Examples of nonionic surfactants include polyoxyethylene alkylphenyl ether necks such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether, and polyoxyethylene alkylphenyl ether necks such as polyoxyethylene lauryl needle and polyoxyethylene oleyl needle. Examples include oxyethylene alkyl ethers, polyoxyethylene sorbitan fatty acid esters such as polio:1-diethylene sorbitan monolaurate, and alkylphenoxy polyglycidols such as nonylphenoxy polyglycidol.

The porous spreading layer has a metering function that (1) uniformly distributes a fixed volume of fluid sample into a fixed volume bottle per unit area within the reagent layer; ) (2) remove substances or factors that inhibit the analytical reaction in the fluid sample; (3) pass through the support in the gap for reflection spectrophotometric analysis;
It has a background function that reflects the transmitted measurement light.

It is also possible to separate these three functions as appropriate and use a separate layer for each function, or to separate two functions and one function and combine the layers. Also in this case, it is preferable to provide a layer having a metering function on the top layer.

The porous spreading layer of the present invention is directly or indirectly laminated on the reagent layer provided on the support as described in IYI.

In the analytical element of the present invention, a reagent layer and a porous development layer are laminated as essential layers on a support, but if necessary, functional layers having other functions (such as a light reflection layer, a filtration layer, A barrier layer, a masking layer, a migration prevention layer) or a structural auxiliary layer (for example, an adhesion auxiliary layer) may be included.

For each of the above-mentioned essential layers and other functional layers, various methods such as the commonly known dip coating method, blade coating method, hopper coating method, etc. can be appropriately selected and used depending on the purpose.

Liquid samples that can be used in the present invention include liquids in any form,
Mention may be made of colloidal solutions.

Preferred examples include biological and scientific liquid samples, such as blood, plasma, serum, spinal fluid, urine, sweat, and saliva.

〔Example〕

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

Example 1 A multilayer analytical element (A) was obtained by sequentially laminating layers having the following composition on a polyethylene terephthalate colorless transparent film support having a thickness t g OP that was subcoated with gelatin.

(Reagent layer) 0 deionized gelatin g/m2 (Adhesive layer) (Porous development layer) The above reagent layer is Apply the coating liquid to the bis- to Squirrel/Li hmm After adjusting the pH to 6.3 with an acid buffer, it was applied and provided.

Further, the porous development layer was coated using a xylene solvent.

The potassium ion concentration in serum was quantified using the thus obtained multilayer analytical element (A). That is, the potassium ion concentration is 2.96.4.95.8.05.12.73
A sample solution of 1 mmol/1 was prepared using fool serum, and each sample was placed on 4 pieces of the multilayer analysis element (A).
After incubation at 37° C. for 7 minutes, the concentration of the colored element was measured by reflection using a spectrophotometer at a wavelength of 600 nm. In order to examine reproducibility, potassium ion concentration was calculated using a calibration curve prepared in advance from the obtained reflection density, and this operation was repeated 10 times each to determine the coefficient of variation (%). .

In order to further examine the storage stability, the above multilayer analytical element (A)
was placed in a sealed container and stored at 30°C and 40°C for 3 days, respectively.
Using mmol/1 sample solution, the coefficient of variation (%) after storage was determined in the same manner as described above. The results are shown in Tables 1 and 2 below together with other examples.

Comparative Example 1 In Example 1, fluorotenside FT in the reagent layer
Except for -248, all other compositions were the same as in Example 1, and a multilayer analytical element (B) was obtained in the same manner. Regarding the multilayer analytical element (B), in the same manner as in Example 1,
Reproducibility and storage stability were investigated. The results are shown in Tables 1 and 2.
Shown below.

Comparative Example 2 In Example 1, fluorotenside FT in the reagent layer
-248, and instead the same amount of Triton X-100
All compositions were the same except that [Octylphenoxypolyethoxyethanol (Rohm and Haas)] was used.
A multilayer analytical element (C) was obtained in the same manner as in Example 1. Regarding the multilayer analytical element (C), in the same manner as in Example 1,
Reproducibility and storage stability were examined. The results are shown in Tables 1 and 2.
Shown below.

Example 2 Example on a support similar to Layer with the following composition By sequentially stacking the Multilayer analysis element (E) I got it.

(Reagent layer) 0 Deionized gelatin: 11 g/m2 Palinomycin 11.54 mM/m" (Adhesive layer) (Layer for porous dust) 0 Triton X-10010, 2 g/m 2 The above reagent layer is The coating solution was adjusted to pH 6.3 with a bis-Tris/phosphate buffer and then applied.The porous development layer was applied using a xylene solvent.Such a porous development layer (E) The potassium ion concentration in serum was measured using the same method as in Example 1, and the reproducibility and storage stability of the measured values were examined.The results are shown in Tables 3 and 4.

Table 4 (Reproducibility after storage) As is clear from the results in Tables 1 and 2, the multilayer analytical element (A) of the present invention has a color reaction element composed of ionophore γ and a reporter substance. By adding a surfactant, both same-day reproducibility and reproducibility after storage are excellent.

Moreover, from Tables 3 and 4, in the present invention, in the color reaction element to which an anionic surfactant is added, the ionophore shows excellent reproducibility even when the ionophore is something other than a crown compound, such as an antibiotic.

〔Effect of the invention〕

With the multilayer analytical element of the present invention, ions in a fluid sample can be easily and reproducibly measured using a colorimetric method. It also has excellent storage stability.

Claims (1)

[Claims] 1. A reagent layer containing a hydrophilic binder on a support;
In a multilayer analysis element in which a porous development layer is laminated above the reagent layer, the reagent layer interacts with (a) an ionophore that can form a complex with an ion, and (b) a complex between an ionophore and an ion, and is detected. A multilayer analytical element characterized in that it contains fine particles of a hydrophobic vehicle containing a reporter substance (c) an anionic surfactant exhibiting a possible response. 2. The hydrophobic vehicle has a boiling point of 175 at 1 atm.
High boiling point organic solvent of ℃ or higher, and boiling point of 50℃ to 160℃
2. The multilayer analytical element according to claim 1, wherein the multilayer analytical element is at least one organic solvent selected from the group consisting of low boiling point organic solvents. 3. The multilayer analytical element according to claim 1, wherein the content of the anionic surfactant on the support is from 5.0 x 10^-^2 to 5.0 g/m^2. 4. The multilayer analytical element according to claim 1, wherein the counter ion of the anionic surfactant is an ion different from the same or similar ion species as the ion to be analyzed.