JPS6375563A - Monolithic type multi-layered analyzing element for analyzing calcium - Google Patents

Abstract

PURPOSE:To decrease the influence of protein such as albumin and inorg. phosphorus by incorporating a fatty acid or the salt thereof or hydroxyl carboxylic acid or the salt thereof into at least one layer upper than a reagent layer. CONSTITUTION:A buffer agent capable of buffering the environmental pH value at which calcium ions and indicator bond to make an optically detectable change from about 8.0 to about 12.0, more preferably from about 9.0 to about 11.5 range; for example, a buffer agent contg. tris(hydroxymethyl)aminomethane, buffer agent contg. phosphate or the like is incorporated into at least one layer upper than the reagent layer of the monolithic type multi-layered analyzing element contg. the reagent layer contg. at least one kind of the indicator which can make the optically detectable change by bonding with the calcium ions and porous development layer in this order on a light transparent water impermeable base. The influence of the protein such as albumin and inorg. phosphorus is thereby eliminated and the quantitative determination of the calcium with high accuracy is permitted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an integrated multilayer analytical element for the analysis of calcium in aqueous liquid samples, and more particularly to biological fluids such as blood (whole blood, plasma, serum), bone marrow, etc. The present invention relates to a dry-operable integrated multilayer analytical element for the quantitative analysis of total calcium in aqueous liquid samples such as fluid, lymph, saliva, urine, etc., which is particularly useful for clinical diagnosis.

[Conventional technology]

One of the analytical methods for calcium is a colorimetric method using an indicator, which is widely used in clinical analysis. O-cresol phthalein complexone (o-CPC), which has an optimal coloring pH at pH 10 or higher, is generally used as an indicator.

However, calcium has the property of binding to proteins such as albumin and inorganic phosphorus (phosphate ions) in an aqueous solution. This property depends on pH, below pH 7, e.g. pH 4.
~5 is weak, and conversely, 9148 or higher, for example, PH10~11 is strong. In the manual method (solution method), since the sample is diluted to a high degree, the binding of calcium to proteins such as albumin and inorganic phosphorus does not pose much of a problem.

On the other hand, in dry analysis in which samples are not diluted in principle, errors due to binding to proteins pose a major problem.

As a means to prevent this error, Japanese Unexamined Patent Publication No. 54-2970
Publication No. 0 discloses a method of causing a color reaction with pi-(5 to 6) using indicators such as chlorophosphonashi (■) and arsenazo (2). A method for measuring total calcium at pH 4 to 5.5 using the method is disclosed.

[Problem that the invention seeks to solve]

The former integrated multilayer analytical element using chlorophosphorus pear (■) had a high absorbance blank value and had problems with measurement accuracy. In addition, the latter method has various problems due to the use of electrodes, and is not preferred as an integrated multilayer analytical element whose major advantage is simplicity.

The present invention aims to solve these problems and reduce the effects of proteins such as albumin and Ja-free phosphorus by simple means.

[Means for solving the problem] [The present invention has been made to achieve such an object. At least one indicator with possible changes
In an integrated multilayer analytical element for calcium analysis having a seed-containing reagent layer and a porous spreading layer in this order, at least one layer above the reagent layer contains a fatty acid or a salt thereof or a hydroxycarboxylic acid or a salt thereof. This objective has been achieved by the integrated multilayer analytical element for calcium analysis.

As the horizontally transparent support for the multilayer analytical element of the present invention, any horizontally transparent (transparent) support used in conventionally known multilayer analytical elements can be used. Specific examples include polymers such as polyethylene terephthalate, bisphenol A polycarbonate, polystyrene, and cellulose esters (e.g., cellulose diacetate, cellulose triacetate-1, cellulose acetate propionate, etc.) with a thickness of 50 μm or more. Approximately 1
1. A film (sheet) having a smooth surface that is preferably transparent in the range of about 80 μm to about 300 μm, that is, transmits at least part of the electromagnetic radiation in the wavelength range of about 200 nm to about 900 nm. Alternatively, a flat support can be used. In the support, titanium dioxide fine particles, barium sulfate fine particles,
Optical performance can be adjusted by dispersing carbon blank or the like. A known undercoat layer or adhesive layer may be provided on the surface of the support, if necessary, to strengthen the adhesion between the support and a water absorption layer, reagent layer, etc. provided on the support.

The reagent layer comprises a reagent composition containing at least one indicator that reacts with calcium ions to produce a detectable color change (preferably a color in the visible region) in a hydrophilic polymer as a polymeric binder. It is a water-absorbent and water-permeable layer that is dispersed in water.

The hydrophilic polymer used in the reagent layer has a swelling rate upon absorption of water in the range of about 150% to about 2000%, preferably about 250% to about 1500% at 30°C. Specific examples of hydrophilic polymers include gelatin such as acid-treated gelatin and deionized gelatin described in JP-A-59-171864 and JP-A-60-115859, gelatin derivatives such as phthalated gelatin, hydroxyacrylate graph 1-gelatin, JP-A-59-171864, JP-A-60-1.1
Examples include agarose, pullulan, pullulan derivatives, polyacrylamide, polyvinyl alcohol, polyvinylpyrrolidone, as described in Japanese Patent Application No. 171134/1987, and methallyl alcohol binary or ternary copolymers as described in Japanese Patent Application No. 171134/1983. These hydrophilic polymers can be used alone or in combination of two or more. The reagent layer typically contains gelatin or gelatin derivatives, polyacrylamide,
Preferably, polyvinyl alcohol or the like is used, and among these, gelatin (deionized gelatin) is most preferred. The dry thickness of the reagent layer is about 5 μm to about 50 μm,
Preferably in the range of about 7 μm to about 30 μm, with a coverage of about 5 g/rd to about 50 g/n (preferably about 7
g/n (in the range of about 30 g/+rl).

As a specific example of the indicator in the reagent composition contained in the reagent layer, 0-cresolphthalein complexone (3,3
'-bis[[di(carboxymethyl)amino]methyl]
-〇-cresol phthalein [2411-89-4),
The numbers in [ ] are for Chemical 8 bstrac.
Registry Number not shown), Eliofromvrasov T (1-(1-hydroxy-2-naphthylazo)-6-nitro-2-hydroxynaphthalene-4-
Sulfonic acid monosodium salt [1787-61-7],
Methylthymol blue complexone (3,3'-bis[[di(carboxymethyl)amino]methyl]thymolsulfonephthalein tetrasodium salt [1945-7
7-3), thymolphthalein conbrexon (3,
3'-bis[[di(carboxymethyl)amino]methyl]thymolphthalein (1913-93-5), arsenazo III (2,7-bis[(2-arsonophenyl)
Azo) 1. ．． 8-dihydroxynaphthalene-3,6-
disulfonic acid (1668-00-4) ), chlorophosphonacyl11 (2,7-bis[(4-chloro-2-phosphonophenyl)azo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid ( 1,914-99-4)
) and other indicators described in the ``Dotite Reagent General Catalog 12th Edition'' (Kumamoto Cloth, Dojindo Chemical Research Institute, published in 1980). Among these indicators, 0-cresolphthalein is preferred because it allows for the most accurate quantitative analysis of total calcium. Furthermore, if necessary, the reagent composition can be contained in two or more separate layers (for example, a reagent layer and a water absorption layer).

The multilayer analytical element of the present invention has an environmental pH value of about 8.0 to about 12.0, which causes an optically detectable change due to the binding of calcium ions and indicators (hereinafter simply referred to as environmental pH value). , preferably selected from known buffering agents capable of buffering to a desired value in the range of about 9.0 to about 11.5.

Buffers that can be used include the Chemical Society of Japan, "Chemical Handbook, Basic Edition" (Tokyo, Maruzen, published in 1966) 1312-
1320 pages, R, M, C, Dawson et
allJti rData forBiochem
ical Re5earchJ5thJrd
at theClarendon Press+ 1.
Published in 969) 476-508 True, rBiochemi
stryJ 5+ p. 467 et seq. (1966), “
^analytical biochemistry
104, pp. 300-310 (1,980).

A specific example of a pH buffering agent with a pH range of 8.0 to 12.0 is tris(hydroxymethyl)aminomethane (Tri
s); buffers containing phosphate; buffers containing borate; buffers containing carbonate; buffers containing glycine;
N,N-bis(2-hydroxyethyl)glycine (
Bicine) ; 3- (cyclohexylamino)
-1-propanesulfonic acid (CAPS) Na salt or salt; N-2-hydroxyethylpiperazine-N'-2-
Hydroxypropane-3-sulfonic acid (1+[!PP5
) Na salt or salt, etc.; N-2-hydroxyethylpiperazine-N'-3-sulfonic acid (EPPS) Na salt or salt, etc. -N-(1-lis(hydroxymethyl)methyl)-3-aminopropane Sulfonic acid (TAPS) Na
Salts, etc. -N-2-Hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) Na salts, etc.; and acids, alkalis, or salts that are optionally combined with any of these. Examples of preferred buffers include Tris-sodium borate;
ne; jlEPPs; IIEPPs thorium salt, EPPS, EPPS sodium salt; CAPS
, CAPS sodium salt, TAPS, TAPS sodium salt, etc.

When gelatin or gelatin derivatives are used as the hydrophilic binder polymer for the reagent layer, water absorption layer, or intermediate layer (described later), these layers can be appropriately crosslinked and cured with a vinyl sulfone structure-containing crosslinking agent, and these layers can be cured by coating. A pH buffer containing boric acid or sodium borate, or CAPS, from the viewpoint of being stably provided and enabling highly accurate quantitative analysis.
, CAPS sodium is preferred. The pH buffering agent may be contained in at least one layer between the support and the porous spreading layer described below, and may also be contained in the reagent layer, water absorption layer, etc. However, when developing it in a layer other than the reagent layer, it is desirable to contain it in a layer closer to the porous developing layer than the reagent layer.

The reagent layer can contain a known mordant, polymer mordant, or the like. It is preferable that the reagent layer and/or the water absorption layer be substantially transparent, but if necessary, a small amount of titanium dioxide fine particles, barium sulfate fine particles, carbon blank, etc. may be dispersed in the layer to adjust the optical performance. Can be done.

Examples of the porous spreading layer include woven fabric spreading layers (e.g., plain weave such as broad and boblin) described in JP-A-55-164356 and JP-A-57-66359, and JP-A-60-222769.
Knitted fabric development layer (e.g., tricot knit, double tricot knit, Milanese knit, etc.) described in JP-A-57-14825
A spreading layer made of paper containing organic polymer fiber pulp as described in No. 0, Japanese Patent Publication No. 53-21.677, U.S. Patent No. 3992
Non-fibrous isodirectionally porous spreading layers such as membrane filters (plush polymer single layer), polymer micropieces, glass microbeads, and diatomaceous earth held in a hydrophilic polymer binder as described in No. 158, etc., and continuous microvoid-containing porous layers; JP-A-55-90859 discloses a non-woven fabric consisting of a continuous microporous porous layer (three-dimensional lattice structure layer) in which polymer micropieces are bonded in point contact with a polymer adhesive that does not swell with water. A fibrous isotropic porous spread layer or the like can be used.

The woven fabric, knitted fabric, or paper used for the porous spreading layer may be subjected to physical activation treatment such as glow discharge treatment or corona discharge treatment described in JP-A-57-66359 on at least one side of the fabric. , or JP-A-55-1
64356. The fabric is made hydrophilic by washing and degreasing treatment described in JP-A-57-66359, hydrophilic treatment such as impregnation with a hydrophilic polymer, or by sequentially performing an appropriate combination of these treatment steps. It is possible to increase the adhesion force with the layer on the near side).

The present invention is characterized in that in such an integrated multilayer analytical element, at least one layer above the reagent layer contains a fatty acid.

Fatty acids have 1 to 3 carbon atoms and do not contain carboxyl groups.
The number is about 0, preferably about 6 to 21, and both straight chain fatty acids, monobranched fatty acids and cyclic fatty acids can be used. Moreover, this fatty acid may be either a saturated fatty acid or an unsaturated fatty acid.

The number of carboxyl groups is about 1 to 2, and usually 1. Examples of preferred fatty acids include lauric acid, myristic acid, valmitic acid, stearic acid, oleic acid,
Caprylic acid, succinic acid, glutaric acid, etc. can be mentioned.

The hydroxycarboxylic acid has about 3 to 6 carbon atoms, preferably about 4 to 6 carbon atoms, and does not contain a carboxyl group. The number of carboxyl groups is about 1 to 3, preferably 2 to 3, and the number of hydroxyl groups is about 1 to 5, preferably 1 to 2. This hydroxycarboxylic acid may be linear or monobranched. Examples of preferred hydroxycarboxylic acids include malic acid, tartaric acid, isocarboxylic acid, and isocarboxylic acid. Among these, restrictive acids and isodaki@acids are particularly preferred.

Both fatty acids and hydroxycarboxylic acids may be salts. The salt may be any salt of an inorganic acid or an organic acid. Examples of salts are sodium salts, potassium salts,
Examples include lithium salts.

Fatty acids, hydroxycarboxylic acids, and salts thereof may be water-soluble or soluble in any organic solvent. The organic solvent is generally a polar solvent with a boiling point of 100°C or lower, such as aliphatic alcohols (eg, methanol, ethanol, propatool).

butanol, isopropyl alcohol), dialkyl ketones (eg, acetone), dialkyl ethers (eg, dimethyl ether), fatty acid cyclic ethers (eg, tetrahydrofuran, dioxane), and the like are suitable. Among these, aliphatic alcohols are preferred, and considering the work environment etc., ethanol is preferred.

Alcohols with low toxicity to the human body, such as propatool, butanol, and isopropatool, are particularly desirable.

Two or more types of fatty acids, hydroxycarboxylic acids, and salts thereof may be used in combination, or both may be used in combination. The layer containing a fatty acid or a salt thereof or a hydroxycarboxylic acid or a salt thereof is preferably an upper layer; for example, a porous spreading layer is optimal. On the other hand, the above-mentioned fatty acids and the like can be contained not only in one layer but also in a plurality of layers.

The method for incorporating the fatty acids and the like may be to dissolve the fatty acids and the like in water or an organic solvent such as ethanol, and apply or spray the solution onto the layer. The content of fatty acids, salts thereof, hydroxycarboxylic acids or salts thereof is about 0.3 g/rrr to about 10 g/r
+(, preferably about 1 g/m to about 5 g/m).

The multilayer analytical element of the present invention can be provided with layers other than these. A water absorption layer can be provided between the support and the reagent layer. The water absorption layer is a layer mainly composed of a hydrophilic polymer that absorbs water and swells, and is a layer that can absorb water from the aqueous liquid sample that has reached or penetrated the interface of the water absorption layer.
When using a whole blood sample, it has the effect of promoting the penetration of plasma, which is an aqueous liquid component, into the reagent layer. The hydrophilic polymer used in the water absorption layer may be selected from those used in the reagent layer described above. Generally, it is preferable to use gelatin or a gelatin derivative, polyacrylamide, or polyvinyl alcohol, and among these, gelatin (deionized gelatin) is the most preferable.

The dry thickness of the water absorption layer ranges from about 3 μm to about 100 μm, preferably from about 5 μm to about 30 μm, and the coverage ranges from about 3 g/m to about 100 g/m, preferably about 5 g/m.
nf to about 30 g/rd.

The water absorption layer can contain a pH buffering agent, a known basic polymer, etc., which will be described later, to adjust the pH during use (when performing analysis operations). Furthermore, the water-absorbing layer may contain a known mordant, polymer mordant, or the like.

The multilayer analytical element of the present invention can also include a hydrophilic non-porous intermediate layer between the developing layer and the reagent layer, which does not allow any protein to pass through. This layer is made of a hydrophilic polymer binder or a crosslinked wood-philic polymer binder similar to that used in the polymer binder, and has a thickness that does not allow high molecular weight proteins, especially albumin and globulin, to pass through.A hydrophilic non-porous intermediate layer ( In general, it is preferable to use gelatin or a gelatin derivative, polyacrylamide, polyvinyl alcohol, etc. for the intermediate layer (hereinafter referred to as the intermediate layer), and among these, gelatin (deionized gelatin) is the most preferable.Drying of the intermediate layer The thickness is about 3 μm to about 20 μm, preferably about 5 μm.
m to approximately 15 μm. The intermediate layer has the aforementioned pH.
The pH during analytical operations can be adjusted by containing a buffer, a known basic polymer, or the like. Titanium dioxide fine particles, barium sulfate fine particles, etc. are dispersed in the intermediate layer within a range that does not impair the non-porous property, so that the light transmittance is approximately 10% to approximately 0.1.
%, preferably about 8.0% to 0.5%, can also function as a light shielding layer.

On the reagent layer or the intermediate layer, a known adhesive layer made of a hydrophilic polymer similar to that used in the water absorption layer, typified by gelatin, can be provided for the purpose of firmly adhering and integrating the spreading layer. The dry thickness of the adhesive layer ranges from about 0.5 μm to about 5 μm.

A surfactant can be contained in the reagent layer, water absorption layer, intermediate layer, adhesive layer, spreading layer, etc. Examples include nonionic surfactants. Specific examples of nonionic surfactants include p-octylphenoxypolyethoxyethanol, p-nonylphenoxypolyethoxyethanol, polyoxyethylene oleyl ether, polyoxyethylene sorbitan monolaurate, p-nonylphenoxypolyglycidol, octyl glucoside, etc. There is. By containing a nonionic surfactant in the spreading layer, the spreading action (metering action) of the aqueous liquid sample becomes better. By containing a nonionic surfactant in the reagent layer or the water absorption layer, water in the aqueous liquid sample is easily absorbed substantially uniformly into the reagent layer or the water absorption layer during analysis operations,
Also, liquid contact with the spreading layer is rapid and substantially uniform.

The multilayer analytical element of the present invention is first prepared by any of the known methods described in the aforementioned patent specifications, and then a solution containing polyhydric alcohol or polyhydric alcohol fatty acid ester is uniformly poured onto the developing layer. It can be applied or sprayed.

The multilayer analytical element of the present invention is cut into small pieces such as squares of approximately 15 fins on each side or circles of approximately the same size.
4, Japanese Patent Publication No. 57-63452, Utility Model Application No. 58-3235
0, it is possible to use it as a chemical analysis slide by placing it in the slide frame described in Japanese Patent Publication No. 58-501144 etc.
It is preferable from various viewpoints such as packaging, transportation, storage, and measurement operations.

Depending on the purpose of use, a long tape may be used as a cassette or 7
It can also be used by storing it in a magazine, or by pasting or storing a small piece into a card with an open EJ.

Analyzing a test component in a liquid sample using the multilayer analytical element of the present invention can be carried out by the operations described in the aforementioned patent specifications. In other words, from about 5μβ to about 30μ! , preferably 8
A droplet of an aqueous liquid sample such as whole blood, plasma, or serum in the range of 1 to 15 μl is spotted on the developing layer without pretreatment, and the sample droplet is placed at a temperature of about 20°C to about 40°C for 1 to 10 minutes. Inktion is carried out at a constant temperature, preferably at a substantially constant temperature around 37°C, and the optical density of the reagent layer or water absorption layer is determined using visible light (or near ultraviolet light) from the light-transmitting support side. The content of the test component (total calcium) in the liquid sample can be determined by reflection photometry and the principle of colorimetric measurement using a calibration curve prepared in advance. By keeping the amount of aqueous liquid sample deposited, incubation time, and temperature constant, quantitative analysis of the test component can be performed with high precision. This measurement operation is described in JP-A-56-77746, JP-A-58-
2]566, JP-A No. 58-161867, etc., it is possible to perform highly accurate measurements with extremely easy operation.

[For production]

In conventional integrated multilayer analytical elements, a color reaction is carried out in acidic conditions in order to quantify bound calcium bound to proteins such as albumin or inorganic phosphorus. In the integrated multilayer analytical element of the present invention, by contacting the spotted sample with a fatty acid or hydroxycarboxylic acid before causing a color reaction, it is possible to add to ionic calcium without causing a color reaction in an acidic environment. Bound calcium can also be quantified.

〔Example〕

Example I Colorless and transparent polyethylene terephthalate 1 with a thickness of 180 μm
-(PET) film (support) was coated with coating layers having the following composition by successively applying 1ζ using an aqueous solution and drying, and then laminated.

1 Yuko layer - Deionized gelatin 23.9 g/i Boric acid 1.11 g/rd Aqueous solution was adjusted to pH 10.0 with NaOH.

Aid 11 Deionized Seratin 1.46 g /
=Titanium dioxide fine particles 0.85g/
Next, water is supplied almost uniformly to the surface of the adhesive layer to moisten it, and on top of it, a 250 μm thick fabric made of PET spun yarn equivalent to 10O8 is applied with light pressure almost uniformly. It was laminated to provide a developing layer. Then, a fatty acid salt-containing polymer aqueous solution was applied onto the developing layer to the following coating amount and dried to prepare an integrated multilayer analytical element for calcium quantification.

Thinning Stage 1 Containing Seed Polymer Aqueous Coating Composition A 2.0 g/rd aqueous solution of sodium oleate was adjusted to pH 10.0.

Example 2 An integrated multilayer analytical element for quantifying calcium was prepared in the same manner as in Example 1, except that the following fatty acid salt-containing polymer aqueous solution was used.

Sodium polystyrene sulfonate 5.75 g /
rd nonylphenoxy polyethoxyethanol (containing 40 oxyethylene units on average) 6.2 g/m sodium oleate 1.0 g/% aqueous solution Na
The pH was adjusted to 10.0 with OII.

Comparative Example 1 An integrated multilayer analytical element for quantifying calcium was prepared in the same manner as in Example 1, except that the following aqueous solution was used in place of the fatty acid salt-containing polymer aqueous solution in Example 1.

Polystyrene sulfonic acid lithium 5.75 g
/=The aqueous solution was adjusted to pH 10.0 with NaOH.

Next, calcium chloride, human serum albumin (H3A)
was dissolved in physiological saline to prepare a calcium solution having a protein concentration of 10 μ/d1 as shown in the table below. When the calcium concentration of this solution was quantified using the above-mentioned integrated multilayer analysis element, the results shown in the table below were obtained.

Example 3 On a colorless and transparent polyethylene terephthalate (PET) film (support) having a thickness of 180 μm, coating layers were sequentially coated with an aqueous solution and dried to have the following composition and were laminated. .

A 16.8 g/% aqueous solution of deionized gelatin was adjusted to pH 10.6 with NaOH.

3.5g of deionized gelatin/Titanium dioxide 4. Og/r+ (The aqueous solution was adjusted to pH 10.6 with NaOIt.

Next, water is supplied almost uniformly to the surface of the adhesive layer to moisten it, and a tricot knitted fabric with a thickness of about 250 μm made of PET spun yarn equivalent to 10O8 is laminated thereon by applying light pressure almost uniformly. A development layer was provided. Next, an aqueous solution of a hydroxycarboxylic acid-containing polymer was coated on the developing layer to the following coating amount and dried to prepare an integrated multilayer analytical element for quantifying calcium.

A citric acid (hydrated) 0.6 g/a aqueous solution was adjusted to pH 1,0,6 with Na 011.

Comparative Example 2 An integrated multilayer analytical element for calcium determination was prepared in the same manner as in Example 3, using the following instead of the hydroxycarboxylic acid-containing polymer aqueous solution.

1. Lichloroacetic acid Dissolved in 1.0 g/iethanol and applied.

Comparative Example 3 Using the following as a trichloroacetic acid-containing polymer aqueous solution,
An integrated multilayer analytical element for calcium determination was prepared in the same manner as in Example 3.

A 1.0 g/a aqueous solution of trichloroacetic acid was adjusted to pH 10.5 with NaOtl.

Comparative Example 4 An integrated multilayer analytical element for calcium determination was prepared in the same manner as in Example 3 using the following development control composition.

It was dissolved in ethanol and applied.

Next, calcium chloride and calcium chloride and inorganic phosphorus were each dissolved in physiological saline to give a calcium concentration of 10 mg/
d7! So the inorganic phosphorus concentration is O or 1101I1/d7! A solution of calcium was prepared. When the calcium concentration of this solution was quantified using the above-mentioned integrated multilayer analysis element, the results shown in the table below were obtained.

Comparative Example 4 is one without any measures against inorganic phosphorus. In Comparative Example 2, the pH of the developing layer was lowered with trichloroacetic acid, which was sufficiently effective, but in Comparative Example 3, in which the pH of the developing layer was set to 10.5, there was no effect.

In Example 3, even when the pH of the developing layer was set to 10.5, sufficient effects were still obtained.

〔Effect of the invention〕

With the integrated multilayer analysis element of the present invention, calcium can be quantified with high precision by eliminating the influence of proteins such as albumin and inorganic phosphorus. This analytical element of the present invention has the advantage that it is easy to manufacture and inexpensive because it is simply made to contain a fatty acid, a hydroxycarboxylic acid, or a salt thereof in a conventional analytical element.

Patent applicant Fuji Photo Film Co., Ltd. Agent Patent attorney 1) Masa Hiroshi Naka (1 person)

Claims (1)

[Claims] (1) Calcium having, in this order, a reagent layer containing at least one indicator that can undergo an optically detectable change when bound to calcium ions and a porous spreading layer on a light-transparent horizontally transparent support. An integrated multilayer analytical element for calcium analysis, characterized in that at least one layer above the reagent layer contains a fatty acid or a salt thereof or a hydroxycarboxylic acid or a salt thereof.