Abstract: The present invention provides a creatinine sensor material having a first layer of a protonated pH sensitive fluorophore immobilized in a hydrophobic polymer, wherein the fluorophore can react quantitatively with ammonia and the transducing moiety of the fluorophore is neutrally charged when deprotonated; a second layer of creatinine deiminase and a polymer; and a third layer of a polymer. The present invention also provides a method for detecting creatinine using the creatinine sensor material and optical sensing devices that incorporate the creatinine sensor material.

Abstract: A strip for testing for the presence of an analyte generally comprises a support member which contains a spreading layer and a reagent layer, and a capillary tube in communication with the support layer and spreading layer for transporting a sample of body fluid thereto. A method of testing a fluid for the presence or concentration of an analyte is also provided which generally includes providing a test strip with a support member, a spreading layer, and a reagent layer on the spreading layer. A capillary tube is provided on the support member whereby a fluid containing an analyte to be tested is introduced into the tube and flows through the tube to the spreading layer and contacts the reagent layer.

Abstract: The present invention provides a urea sensor material having a first layer of a protonated pH sensitive fluorophore immobilized in a hydrophobic polymer, wherein the fluorophore can react quantitatively with ammonia and the transducing moiety of the fluorophore is neutrally charged when deprotonated; a second layer of urease and a polymer; and a third layer of a polymer. The present invention also provides a method for detecting urea using the urea sensor material and optical sensing devices that incorporate the urea sensor material.

Abstract: A chemical analysis film chip is prepared by integrally laminating a reagent layer and a spreading layer on a support sheet in this order, or by integrally laminating a water absorbing layer having a hydrophilic polymer as a major component and a porous outermost layer containing therein a reagent on a support sheet in this order, or by superposing a porous layer containing therein a reagent on a support sheet.

Abstract: Disclosed is an improvement to a sandwich type immunoassay in which there is immobilized to a solid support an antibody which is specific to an epitope of the analyte whose presence or concentration is being sought and a first labeled antibody which is specific to another epitope of the analyte. The improvement involves providing a second labeled antibody which is specific to the first labeled antibody to thereby form a chain of two or more labeled antibodies which results in amplification of the signal generated upon formation of the sandwich.

Abstract: A method and apparatus for the quantitative analysis of sample liquids. A sample is dried and irradiated with visible and/or infrared light. Light that is diffusely or specularly reflected from the sample and sample carrier is detected. and analysed.

Abstract: A lawn assay is described for determining compounds that affect enzyme activity or that bind to target molecules. Compounds to be screened are cleaved, and diffused from solid supports into a colloidal matrix. Enzymatic catalysis or binding to target molecules by the compounds is carried out in the matrix. Active compounds are found by monitoring a photometrically detectable change in a substrate, coenzyme, or cofactor involved in the enzymatic reaction, or in a labeled ligand bound to the target molecule, that produces a zone of activity associated with the compounds.

Abstract: The invention concerns a diagnostic test carrier (1) containing a supporting layer (2) with a detection layer (3) arranged thereon containing reagents required for the determination of an analyte in a liquid sample and an inert layer (4) covering the detection layer (3) wherein the inert layer (4) is arranged at such a distance (5) from the detection layer to enable a capillary active liquid transport between the detection layer and inert layer (3,4), characterized in that the inert layer (4) extends beyond the detection layer and wherein the area (10) that extends beyond the detection layer is attached to the supporting layer (2) in such a way that a continuous capillary active liquid transport between the inert layer and detection layer (4,3) and between the inert layer and supporting layer (4,2) is possible and in addition the inert layer (4) contains several holes (7) in the area of the detection layer (3) through which the sample to be examined and the components contained therein can be applied to the d

Abstract: The present invention concerns a diagnostic test carrier (1) containing a supporting layer (2) with a detection layer (3) arranged thereon containing the reagents required to determine analyte in a liquid sample and a network (4) covering the detection layer (3) which is larger than the detection layer (3) and which is attached to the supporting layer (2), which is characterized in that the network (4) is hydrophilic but not capillary active on its own and an inert cover (5) made of sample-impermeable material is arranged over the areas (6) of the network that extend beyond the detection layer in such a way that a sample application site (7) remains free on the region of the network (4) covering the detection layer as well as the use of such a test carrier for the determination of analyte in a liquid. In addition the invention concerns a method for the determination of an analyte in a liquid sample with the aid of a test carrier according to the invention.

Abstract: A multilayer reagent test strip measures the concentration of analyte in a liquid sample that is applied to it. The sample is guided to a number of assay areas arrayed along the strip, where the analyte can react with a reagent to cause a color change. Each assay area also includes an inhibitor for the color-change reaction. The inhibitor concentration increases in successive assay areas; thus, the number of areas that change color is a measure of the analyte concentration. The test strip is particularly adapted for measuring glucose in a whole blood sample. In a preferred embodiment, the sample is guided to the assay areas along a path formed by crushing selected areas of a membrane, and the assay areas are uncrushed areas of the membrane.

Abstract: A device 10 detects the presence of occult blood in feces by employing a sheet 12 of brittle material in which are formed a plurality of chambers 18 holding a liquid reagent solution juxtaposed to an absorbant material 14 impregnated with a guaiac material. The individual chambers 18 provide individual liquid tight enclosures that have thin walls that rupture to release the reagent solution when the device 10 is used to wipe feces from the rectum. The reagent solution reacts with the guaiac material to produce a blue color in the presence of occult blood in the feces.

Abstract: Two absorbent layer materials for a sample liquid are connected with one another in such a way that the sample liquid can pass through from one layer into the other layer through the connecting surface between the layers a hot melt adhesive is applied to the first layer material in the form of a discontinuous coating and the second layer material is pressed on while the melt adhesive is still sufficiently hot. The amount of the melt adhesive and the pressing-on force are adjusted to one another with regard to the surface properties in such a manner that, even after the application and pressing on of the second layer material, a continuous liquid-permeable melt adhesive layer does not result.

Abstract: A sample application zone and detection zone are arranged on a pile-like complex made of a fleece and a porous membrane which are in a direct or indirect contact that enables passage of liquid through the contact area and the membrane is a polyamide, polyvinylidene difluoride, polyether sulfone or polysulfone membrane which transports liquid significantly slower over the area than the fleece.

Abstract: A dry analysis element for the quantitative analysis of an analyte contained in whole blood comprises a layer exhibiting volume filtration function and a detection layer. The layer exhibiting volume filtration function is made of a cloth selected from microfibrous cloths each having an average fiber diameter of from 0.1 to 10 .mu.m or a napped cloth having an average of from 1 to 30 .mu.m. In a first preferred embodiment, the layer exhibiting volume filtration function is composed of a non-woven cloth having a density of from 0.01 to 0.2 g/cm.sup.3 and made of fibers each having an average fiber diameter of from 0.2 to 10 .mu.m. In a second preferred embodiment, the layer exhibiting volume filtration function is composed of a napped cloth having a fiber density per cm.sup.2 of from 7.0.times.10.sup.3 to 8.2.times.10.sup.6, each of the napped fibers having an average diameter of from 1 to 30 microns and an average nap length of 0.5 to 5.0 mm.

Abstract: An integral multi-layer analytical element for analyzing bile acid sulfate comprising a support member, a reagent layer on said support member and a porous developing layer on said reagent layer, at least one of the reagent layer and developing layer containing bile acid sulfate sulfatase, 3.beta.-hydroxysteroid dehydrogenase and a combination of thio-NAD.sup.+ and reduced NAD or reduced NADP, in which the reagent layer contains a water-soluble polymer, a buffer and at least one component selected from the group consisting of sugar alcohols and Mn.sup.2+, which element suppresses the increase of blank values and prevents agglomeration of the enzyme during the preparation of a solution for forming the reagent layer.

Abstract: The present invention relates to a method and to a device for separating plasma from whole blood. The method and device utilize a permeable non-glass fiber matrix containing a polyol which is capable of clumping red blood cells. The matrix, in the absence of such a polyol, would otherwise be porous to red blood cells. The polyol-containing matrix has a first surface and a second surface such that a whole blood sample which is applied to the first surface flows directionally toward the second surface. Plasma separated from whole blood becomes available at the second surface of the matrix and can be tested for the presence of a particular analyte, such as glucose or fructosamine, as provided by multi-layer test devices of the present invention.

Abstract: A dry, removable analytical element can be used to detect chemiluminescent signals produced from the reaction of peroxidase and a chemiluminescent detection system. The analytical element contains at least two layers, the outer layer being non-tacky and water-soluble or water-permeable, and used to contact a gel plate or transblotting membrane in which multiple analytes are located. The resulting signal can be recorded using a photosensitive element. Test kits include the various packaged components needed to use the analytical element for analyte detection. Within the element are critical amounts of oxidase and an oxidase substrate for highly sensitive analyte detection.

Abstract: A chemical timer for a direct-reading reagent test strip changes color a predetermined time after a biological fluid is applied to the strip. The strip measures the concentration of an analyte in the fluid. The timer is a dry coating of an indicator, an enzyme-containing reagent that when hydrated can react with glucose to change the color of the indicator, an inhibitor to inhibit the change in color of the indicator, glucose, and optionally, an aldose that does not react with the enzyme in the reagent. Preferably, the reagent and glucose are present in excess in the coating, and the time it takes for the timer color to change can be controlled by the inhibitor concentration. The aldose provides timer stability, probably by interfering with glycosylation by the glucose in the dry state.

Abstract: A dry immunoassay analytical element, for assaying a ligand is disclosed. The element comprises, in the following order, (a) a layer containing a labeled ligand, (b) a bead spreading layer, c) a cross-linked hydrophilic polymer layer and d) a support; wherein(i) a fixed concentration of an immobilized receptor for the labeled ligand is located in a zone at the interface of layers (b) and (c); and(ii) the receptors are immobilized by being covalently bonded to polymeric beads that are smaller than the beads in layer (c).

Abstract: The present invention relates to an optical solid-phase biosensor for the detection of molecules which can be labelled with a fluorescent dye for the identification of substances in solution, for which there exists a biomolecule (receptor) which specifically recognises these and is chemically bonded to the uppermost layer of one or more layers of polyions on the surface of the sensor, by measurement of the Forster transfer between another dye molecule which is bonded in one of the uppermost layers of the sensor, and the said dye molecule.

Abstract: The present invention is directed to a new assay procedure and improved solid phase assay devices for use with a so-called physical developer. The invention provides a new assay procedure for detecting the presence of an analyte in a fluid sample using a tracer having a metal label which signal is enhanced by applying a physical developer. The assay is performed with a device having a support for a test area and having attached thereto a binder specific for the analyte to be detected. The assay comprises the steps of directing the fluid sample and the tracer through a porous medium into contact with the test area at a controlled flow rate to allow binding of the analyte with the binder and the tracer to the analyte, directing a physical developer through said porous medium to amplify the signal generated by the tracer, and separating the device to allow the test area to be read. The invention further relates to devices and immunoassay test kits for carrying out the improved immunoassay procedure.

Abstract: Subject matter of the invention are protein-containing interference-reducing agents for immunoassays consisting of protein aggregates that are acylated with --CO--R groups, wherein R is a branched or non-branched C1-C4 alkyl residue which can be substituted with hydroxy, carboxy, SO.sub.3 H or PO.sub.3 H.sub.2 groups. These interference-reducing substances can be used together with a buffer as an interference-reducing agent or together with an immunological binding partner as a binding reagent to reduce non-specific interactions in immunoassays. Another subject matter of the invention is an immunological testing method wherein said interference-reducing substances are used.

Abstract: A dry, removable analytical element can be used to detect chemiluminescent signals produced from the reaction of peroxidase and a chemiluminescent detection system. The analytical element contains at least two layers, the outer layer being non-tacky and water-soluble or water-permeable, and used to contact a gel plate or transblotting membrane in which multiple analytes are located. The resulting signal can be recorded using a photosensitive element. Test kits include the various packaged components needed to use the analytical element for analyte detection. Within the element are critical amounts of oxidase and an oxidase substrate for highly sensitive analyte detection.

Abstract: A reagent strip for measuring glucose concentration in a biological fluid containing red blood cells has reduced interference of hematocrit with the glucose measurement. When a biological fluid contacts the strip, it causes, in a reagent impregnated in the strip, a color change which is a measure of the glucose concentration in the fluid. However, the color change is also affected by the red blood cell concentration (hematocrit), thereby reducing the accuracy of the glucose measurement. The hematocrit effect is reduced by adding to the reagent a component, such as imidazole or imidazole and N-acetylglucosamine, for minimizing side reactions of the glucose, or its reaction products, with the fluid.

Abstract: An assay device for detection and/or determination of an analyte in a test sample uses a barrier containing an aperture to control the application of reagents to the device for greater reproducibility of results. In its simplest form, the device comprises: (1) a chromatographic medium having a first end, a second end, and first and second surfaces, and having a specific binding partner for the analyte immobilized thereto in a detection zone; (2) at least one absorber in operable contact with at least one of the first and second ends; and (3) a substantially fluid-impermeable barrier adjacent to the first surface of the chromatographic medium, the barrier having at least one aperture therethrough for application of liquid to the chromatographic medium, the barrier at least partially blocking application of liquid to the chromatographic medium.

Abstract: The invention concerns a method for the quantitative analysis of sample liquids. A sample is dried and irradiated with visible and/or infrared light. Light that is diffusely or specularly reflected from the sample and sample carrier is detected and analysed. Furthermore the invention concerns a system for carrying out the method according to the invention and a sample carrier having a diffusely or specularly reflecting surface.

Abstract: A multilayer analytical element for assaying fructosamine having a liquid-impermeable support, a dried buffer-containing layer which contains a buffer having pH of 8 to 12 formed on the support, and a tetrazolium salt-containing layer which is laminated on the buffer-containing layer, which element assays fructosamine in a short time with good accuracy.

Abstract: A simplified measuring apparatus for use in the qualitative or quantitative measurement of substances to be assayed in test samples, such as proteins, antibodies and the like, in a small amount of test samples by a simple and easy operation without requiring a B/F separation step comprises: (a) a liquid permeable porous reaction membrane whose surface having at least one reaction area to which an affinity substance capable of directly or indirectly capturing a substance to be assayed or a soluble agent is immobilized; (b) a porous body arranged on the upper part of the porous reaction membrane, to which a soluble agent capable of being solubilized by the addition of a test sample is adhered in a releasable manner; (c) an absorption member arranged on the lower part of the porous reaction membrane, which contacts with a periphery, excluding the reaction area, of the porous reaction membrane via a liquid non-permeable sheet; (d) a liquid non-permeable transparent cover arranged on the lower part of the absorpti

Abstract: A delivering member for filtering and delivering a sample to a test assay surface includes a prefilter having a sample receiving surface and a surface for delivering a sample to a test assay surface. The prefilter includes a diffusing material on its receiving surface for rapidly and evenly diffusing a sample across the prefilter receiving surface. In this way, a sample may be rapidly and evenly delivered to a test assay surface. A test assay solid phase has a surface including an area carrying an immobilized species and an area free of immobilized species. When a sample is applied to the surface, followed by application of a labeled species, the evenness of distribution of the labeled species is indicative of the evenness of application of the sample. A kit includes a delivering member and an assay surface.

Abstract: The present invention relates to a device for performing biochemical diagnostic assays. The device, which is preferably provided in a self-contained disposable form for use in extra-laboratory conditions, comprises two liquid flow channels of porous material which transfer liquid by capillary flow to a common site in sequentially timed manner following simultaneous application of the liquid to the ends of the channels. The channels interconnect at a certain point and then both continue in an arrangement analogous to an electrical bridge circuit. By selecting the hydraulic resistances of the arms of this circuit the flow can be controlled across the bridge. Balancing the circuit will produce null flow across the bridge and prevent the flow from one channel from dominating that from the other when the channels are saturated. Alternatively the arrangement can be such as to produce oscillating flow across the interconnection.

Abstract: A multilayer analytical element for measuring enzyme activity in a liquid sample such as a body fluid which is less affected by intrinsic pyruvic acid contained in the liquid sample is disclosed. The analytical element comprises a support, a reagent layer, an optionally provided other layer, and a porous spreading layer. The reagent layer and/or the optionally provided other layer contain pyruvic acid oxidase. The characteristic feature of the analytical element lies in that the spreading layer has a specific void volume in the range of 3-15 .mu.l/cm.sup.2.

Abstract: The present invention relates to a membrane suitable for use as the support for one or more test reagents for testing a material applied to the membrane, which membrane is characterized in that it is initially an open pored porous material and in that at least part of the length the pores therein are blinded so that cell wall fragments from the material applied to the membrane are substantially prevented from passage through the membrane. Preferably, the pores are totally blinded by a gelatin matix containing one or more reagents which react with a fluid applied to one surface of the membrane to give a color which can be observed from a second surface of the membrane.

Abstract: A sample holder for use in infrared spectrophotometric analysis. The holder comprises a microporous sheet and is particularly useful for analysis of solutions, colloids, small particle solids, flowable solids, solvents, and viscous fluids. The microporous sheet preferably has a low absorbance (high spectral transmittance) in infrared wavelengths. The sample holder is especially useful for the analysis of aqueous based samples. Also, a method for using such sample holders for infrared spectrophotometric analysis.

Abstract: A method for reading and analyzing a diffusion-cell colorimetric exposimeter for making a quantitative determination of the time-weighted average (TWA) exposure to airborne gases or vapors. The diffusion cell is optically scanned to form color video signal data representative of the primary color components of the image formed from the reaction of the chromophoric reagent and pollutant. The data is converted to digital data and processed to compute exposure for a given pollutant gas as a function of color intensity for at least one of the primary color components.

Abstract: An analytical element for whole blood which comprises a blood cell-separating layer having a volume smaller than the upper limit of the diffused volume of a whole blood sample having a hematocrit value of 70% provided on a porous layer, and a method of measuring an analyte which comprises spotting a whole blood sample onto the above analytical element removing the blood cell-separating layer after blood plasma portion of the sample is diffused into the porous layer, supplying a fixed amount of measuring reagent solution having a diffused area smaller than the diffused area of the blood plasma to measure the analyte. According to the invention, the analytical error caused by scattering of hematocrit values is removed, and analysis can be conducted in a high accuracy.

Abstract: An improved device and method of a) separating the cellular components of whole blood from plasma or serum, b) separating the low density lipoprotein (LDL) fraction and the very low density lipoprotein (VLDL) fraction from the plasma or serum, then c) assaying the plasma or serum for cholesterol present in the high density lipoprotein (HDL) fraction are disclosed. The device includes a separation area that separates the cellular components of whole blood from the serum or plasma and separates the LDL and VLDL fractions from the serum or plasma, and a test area that assays the serum or plasma for the concentration of the HDL cholesterol. The method includes introducing a whole blood sample to a test device including a separation area comprising a first zone that separates the cellular components of the whole blood from the plasma or serum; and a second zone that separates the LDL and the VLDL fractions from the plasma or serum.

Abstract: A support for biological molecules comprising a porous inorganic matrix and particles of a water-insoluble polymer, and a biologically active support comprising a porous inorganic matrix and particles of a water-insoluble polymer "sensitized" by biological molecules. The supports are prepared by bringing the matrix into contact with an aqueous dispersion of optionally "sensitized" polymer particles, and the use of such supports in biological application.

Abstract: A method of assaying analytes using a rate procedure is described where the change in density over time has a variable rate. The method features the steps of depositing the sample onto a dried slide-like test element, making an initial rate reading during an early time window, using the initial rate readings in a comparison study with rates from known low and high concentration results to predict whether the sample rate will be sufficiently low as to be ascertainable during a later time window or not, and then calculating a rate of reaction and concentration during either the early time window or the early time window with a portion of the later time window, respectively.

Abstract: The present invention is directed to a new assay procedure and improved solid phase assay devices for use with a so-called physical developer. The invention provides a new assay procedure for detecting the presence of an analyte in a fluid sample using a tracer having a metal label which signal is enhanced by applying a physical developer. The assay is performed with a device having a support for a test area and having attached thereto a binder specific for the analyte to be detected. The assay comprises the steps of directing the fluid sample and the tracer through a porous medium into contact with the test area at a controlled flow rate to allow binding of the analyte with the binder and the tracer to the analyte, directing a physical developer through said porous medium to amplify the signal generated by the tracer, and separating the device to allow the test area to be read. The invention further relates to devices and immunoassay test kits for carrying out the improved immunoassay procedure.

Abstract: A light transmittance type analytical system for the rapid quantitation of minute amounts of an analyte in a fluid sample and an optical component and test device useful therein are; disclosed. The analytical system employs an assay in which the presence of the analyte in the assayed sample is productive of an insoluble substantially opaque, light absorptive colored end product. In the preferred use of the analytical system, the end product is formed in contact with a light and fluid permeable optical component in the form of a matrix of compacted substantially water insoluble granules of reflective material which has a light scattering coefficient of at least about 80 and is substantially nonabsorptive of light.

Abstract: The invention relates to an apparatus and a method useful in separating non-high density lipoproteins, referred to as "non-HDLs", from biological fluids containing them. A porous carrier is provided which contains a non-HDL precipitating agent. One need only contact the sample of interest to the carrier for one minute or less, after which the precipitated non-HDLs are no longer present in the sample being tested. The applications of the method include the ability to determine high density lipoproteins in the sample without interference from non-HDLs.

Abstract: A multilayer analytical element has been prepared for accurate and rapid colorimetric determination of ethanol in aqueous specimens using alcohol dehydogenase and an oxidized nicotinamide coenzyme. The element includes three reagent layers beneath a porous spreading layer. The middle reagent layer has a crosslinked hydrophilic binder, while the other two reagent layers have uncrosslinked binders. In addition, both uncrosslinked reagent layers include a relatively high amount of a buffer having a primary amine, which buffer maintains the layer pH at from about 8 to about 10. Alcohol dehydrogenase is in the reagent layer next to the porous spreading layer.

Abstract: A laminated assay device for use in determining the presence or amount of an analyte in a sample involving a bibulous assay strip having a sample application zone, a reagent zone and a pair of liquid impervious barriers defining a measurement zone extending from and in fluid communication with the application zone. The measurement zone has a volume measuring the amount of sample required for the assay. A substantially nonabsorbent first supporting film extends across and is laminated to the front surface of the assay strip, while a substantially nonabsorbent second supporting film extends across and is laminated to the back surface of the assay strip. The assay strip is impregnated with the members of a signal producing system which, upon reaction with a component in the sample, produce a detectable signal.

Abstract: A dry phase device separates high density lipoprotein (HDL) from a blood (serum or plasma) sample. The device contains a fluid permeable material having dispersed therein finely divided, porous silica or silicate particles as selective absorbant for HDL. By combining the device with a second layer designed to remove very low density lipoproteins/chylomicrons from the blood, and a third layer containing means for quantitative cholesterol detection, there is provided a test device for the direct determination of low density lipoproteins cholesterol.

Abstract: An integral test element for analysis of liquids comprising: a) a spreading layer for uniformly spreading within itself at least a substance of a liquid sample applied to the element; b) a reagent layer in fluid contact with the spreading layer and permeable to a substance spreadable within the spreading layer or to a reaction product of such a substance, the reagent layer having a chemically interactive material which, in the presence of the substance or of the reaction product of the substance, produces a detectable change in the element; and c) a radiation upconversion phosphor layer or crystal for producing an upconverted radiation when excited by visible or infrared excitation radiation from an independent source.

Abstract: An integral multilayer analytical element in which a first fibrous porous layer, a nonfibrous porous layer, and a second fibrous porous layer superposed in this order on a water-impermeable light-transmissive support the first fibrous porous-layer having a larger pore size than the nonfibrous porous layer. The above three porous layers are integrally laminated to each other substantially closely by an adhesive discontinuously disposed so as to form microspaces continuing through from one layer to the next so as not to interfere with the approximately uniform permeation of liquid. A reagent composition which produces an optically detectable change in the presence of an analyte is incorporated in at least one of said three porous layers. When a nonporous reagent layer is incorporated on the support in the above analytical element, the reagent composition is incorporated in the nonporous reagent layer.

Abstract: The invention provides a method for supplying an enzyme substrate to a membrane-based, enzyme-linked reaction, comprising providing an open pore, high liquid retention capacity material impregnated with a predetermined amount of a substrate for the enzyme; and contacting the material with a membrane containing the enzyme-linked reaction under conditions which permit diffusion of the enzyme substrate to sites on the membrane containing the enzyme linked reaction.

Abstract: A multi-layer blood culture sensor includes two matrices. The first matrix is a polymer that is permeable to carbon dioxide and water, but impermeable to protons. A pH sensitive absorbance based dye is encapsulated or isolated in the polymer. The second matrix is a polymer with a pH insensitive fluorescent dye encapsulated or isolated in the polymer. The matrices are spectrally coupled and are useful for the determination of microorganisms in a blood culture bottle.

Abstract: A microassay card includes an upper layer containing wells for receiving a liquid sample. A second layer of the card, beneath the first layer, includes a supporting surface bound to a reactive species. A third layer includes a superabsorbent support impregnated with an indicator. Typically, the indicator is a substrate for an enzyme, such as a reduced dye precursor and a source of hydrogen peroxide necessary for the action of the enzyme upon the substrate to cause a spectral change in the absorbent layer. By selecting the structure of the first and second layers, the card can be formatted for a displacement assay or a competitive assay. The microassay card of the present invention is particularly useful for drug testing.

Abstract: A multilayer analytical element for assaying fructosamine, having a liquid-impermeable support, a buffer-containing layer which contains a buffer having pH of 8 to 12 formed on the support, a tetrazolium salt containing layer which is formed on the buffer-containing layer and, optionally, an intermediate layer interposed between the buffer-containing layer and the tetrazolium salt-containing layer to prevent contact of these two layers, which element assays fructosamine in a short time with good accuracy.