Abstract: A direct-read exposimeter for providing a visual, graded measurement of color variation corresponding to different ranges of dosage exposure to a polluting gas in the atmosphere over a given time period. The exposimeter includes a color-forming member and at least one gas-diffusion control member within an enclosure formed between a base and a cover. The cover has a number of openings exposed to the atmosphere in alignment with a number of separate diffusion zones formed in the gas-diffusion control member.

Abstract: An immunochromatographic assay device for the detection of an analyte in a liquid sample, the device including a housing that contains an opening for the application of the liquid sample and multiple liquid permeable materials located in the housing that are adapted to receive, treat and facilitate the movement of the sample through the housing; preferably, a first liquid permeable material is adapted to receive the liquid sample; a second liquid permeable material is positioned under the first liquid permeable material; a third liquid permeable material is positioned above the second liquid material; means are provided to prevent liquid communication between the first and third liquid permeable materials; a wicking material, in fluid contact with the third liquid permeable material receives the sample; and reagents are positioned in the housing that display the results of the immunoassay.

Abstract: A liquid transfer device of disposable one-time use form to conduct a biochemical diagnostic or other assay comprises two liquid flow channels (10,110,210; 20,120,220) leading from a respective pair of channel ends to a common site (30,130,230) and operable to deliver liquid to this site in sequentially timed manner following simultaneous application of such liquid to the channel ends. Typically respectively different reagents (11,111,211; 21,121,221) are incorporated in the two channels, and a third reagent (31,131,231) at the common site, whereby a sample to be assayed in respect of a particular content can be applied to the site, immobilized by the third reagent, subsequently subjected to one channel reagent to detect any of the content of interest, and finally subjected to the other channel reagent to exhibit for the user any detected content.

Abstract: A dry analytical element has been prepared for the assay of leucine aminopeptidase at a pH of 6.5 to 11. The element zone contains an aromatic substrate for the enzyme. This substrate provides an aromatic reactant which has a primary amino group on the aromatic ring in the ortho or para position to an electron donor group. The aromatic reactant is oxidized with an oxidizing compound (such as an oxidase) and the oxidized compound reacts with a ballasted color-forming coupler to provide a dye.

Abstract: An assay for determining the cholesterol level in a sample involving a bibulous strip comprising a transfer region for transporting a transport medium from a transport medium source, a sample receiving region in fluid communication with the transfer region, and a measurement region in fluid communication with the sample receiving region, and a detectable signal reagent system comprising a catalytic agent or enzyme, unbound conversion reagent and bound reagent wherein the conversion reagent reacts with cholesterol to form an intermediate product and wherein the bound reagent reacts with the intermediate product in the presence of the catalytic agent or enzyme to produce a detectable border, in which the conversion reagent is placed in the transfer region of the strip or in a region of the strip between the sample receiving and measurement regions and the signal reagent is non-diffusively bound to the strip in the measurement region, and which upon contact with the sample and the transport medium results in the

Abstract: A method for measuring an analyte using a dry analytical element composed of at least a hydrophilic polymer layer and a spreading layer laminated onto a water-impermeable support and to which a liquid sample of the analyte has been supplied, by supplying a measuring reagent solution to the analytical element. The measurement of the analytical element is carried out by optical means.

Abstract: A unitized multilayer dry reagent analytical chemistry test structure and device and method of fabricating such device is described. The device includes two or more contiguous layers of absorbent or porous paper or polymeric material, at least one of which is incorporated with a test reagent composition, the layers attached to each other with intermediate porous attachment layers by fusion bonding. When the device is contacted with the fluid being tested the attachment layers allow the free flow of such fluid from one layer to the next.

Abstract: A method for determining the amount of an analyte in a sample fluid utilizing an assay element which comprises at least one reagent layer. The assay method includes the steps of optically reading a signal producing species, e.g., a fluorescent label, a first time prior to depositing the sample fluid on the assay element and a second time, at the same wavelength and in the same location within the assay element after the sample fluid has been applied to the assay element and the sample analyte has interacted with the reagent(s) present in the assay element. The first, or dry, reading is corrected for relative humidity and/or temperature variations.

Abstract: Biologically active reagents are prepared from particles of copolymers having highly active succinimid groups. The reagents are prepared by covalently attaching biologically active substances, for example antibodies, to the particles, directly or indirectly through amide groups by displacement of highly active succinimid groups on the particle surface. These reagents are used to advantage in analytical elements, methods for the detection of specific binding ligands (such as immunological species) and immunoassays, and in purification methods such as affinity chromatography.

Abstract: A method for control or calibration in a chemical analytical determination using a dry analysis element comprising at least one color-producing reagent and a porous layer, wherein the method comprises applying an aqueous dispersion onto the porous layer and measuring the optical density of the color produced, wherein the aqueous dispersion comprises a substance which is the same as or similar to an analyte to be determined and water-insoluble particles dispersed therein, wherein the particles are particles of a homopolymer, a copolymer, phthalates, trimellitates, phosphates, benzoates, amides, phenols, aliphatic esters, hydrocarbons, halogenated hydrocarbons, adipates, sebacates and natural polymers.

Abstract: A device for colorimetric assay of at least one component in a liquid sample, which device comprises a support, a reagent layer formed on a part of one surface of the support and a sample-receiving layer which covers at least a part of the reagent layer and at least a part of the support surface, with which the timing of application of a sample on the device is automatically detected with accuracy.

Abstract: A test carrier for the determination of ions containing a test layer which has a liquid-resistant, organic phase which contains a hydrophobic polymer in a homogeneous mixture with a hydrophobic, organic liquid of low volatility and an ionophore, as well as a substance which changes its colour in the presence of the ion to be determined. The test carrier is characterized in that the test layer contains particles with an oil number of 80-200 and the ionophore is homogeneously dispersed in the hydrophobic, organic phase. A second test layer contains a buffer capable of maintaining the pH therein at a value of between 5-10.

Abstract: A synthetic substrate used for quantitative analysis of a trace enzyme. The substrate has a molecular structure (B)-(A)-(C) comprising at least one structure (A) catalytically affected by the enzyme to be analysed, at least one photographically active labelling structure (B) linked to the structure (A) and at least one specific adsorbing structure (C) linked to the structure (A). The substrate is used in a quantitative analysis of a trace enzyme, in which the structure (A) or the linkage between the structure (A) and the structure (C), or the linkage between the structure (B) and the structure (A) is cleaved by the action of the analyte enzyme. The reaction product of the enzymatic reaction is separated by allowing the same to contact with an adsorbent for the structure (C). The separated reaction product is developed photographically and then the optical density of the resultant developed silver and/or colored dye is measured.

Abstract: A dry analysis element which gives a calibration curve having a constant blank value for every lot and can be used without the need of correction of the internal calibration curve memorized in an analyzer. The dry analysis element including a water-permeable layer which contains: a reagent composition capable of producing an optically detectable substance in the presence of a predetermined analyte in an aqueous sample; and a fogging agent selected from the group consisting of the optically detectable substance and a material which is detectable by the same method for detecting the optically detectable substance. Also provided is a process for preparing the analysis element.

Abstract: A colorimetric assay for the determination of conjugated or unconjugated bilirubin in biological fluids can be carried out with an improved analytical element. The element includes a support having thereon a gelatin-free mordant layer with a positively-charged interactive mordant having at least one binding site for bilirubin, a radiation-blocking layer, and a porous spreading layer. The interactive mordant is dispersed in a binder material of crosslinkable copolymers which include a monomer capable of reaction with a crosslinking agent to crosslink the copolymer.

Abstract: An integral multilayer analytical element for the determination of ammonia or an ammonia-producing substance comprising a light-transmissive liquid-impermeable support, an indicator layer containing an indicator which produces a detectable change by gaseous ammonia, a liquid permeation barrier layer, a reagent layer containing an alkaline buffer and optionally a reagent capable of reacting with a substance to produce ammonia and a spreading layer laminated in this order, which is improved by that the indicator layer contains a polyvinyl alkyl ether, and/or which is improved by that the surface of said support facing toward the indicator layer is undercoated with a polyvinyl alkyl ether, a hydroxyalkyl cellulose, an alkyl cellulose, polystyrene, a polyalkyl methacrylate, polyviriylidene chloride, polyvinyl alcohol or polyvinyl pyrrolidone, substantially not containing ammonia and ammonium ion.

Abstract: A test carrier for the analysis of fluids has a test field which is held in a frame and a test application surface for the application of a sample fluid. Sometimes called an "analysis chip", such devices are suitable for accommodating a test layer pack which has a plurality of layers lying loosely on one another. These devices are thin and allow for low cost manufacturing and simple and efficient handling, and has a base body of a plastic material, with a trough-shaped depression for accommodating the test field therein. A retaining net of a plastic material spans above the depression and the test field.

Abstract: A layered device suitable for use in the analysis of blood samples which includes a first layer of a matrix material having dispersed therein a complex of copper and a polymer containing multiple pendant carboxyl groups which selectively combines with hemoglobin and bilirubin in fluid communication with a second layer which contains a reagent system which reacts with one or more predetermined analytes in the blood sample to provide a color change.

Abstract: A dry analytical element for the determination of serum cholinesterase (CHE) activity is disclosed. The element analyses undiluted body fluids and employs butyrylthiocholine as the substrate for CHE. Butyrylthiocholine is hydrolyzed by serum cholinesterase and liberates butyric acid and thiocholine. The thiocholine liberated then reduces ferricyanide to ferrocyanide and the rate of change is measured by reflectance densitometry.

Abstract: A device for separating plasma from blood is provided comprising a synthetic polymeric fibrous structure having a CWST in excess of 65 dynes/cm, the structure having a first region for receiving a blood sample and a second region for accumulating plasma.

Abstract: Non-instrumented assays are providing employing a flow-path with a moveable sample receiving pad, which moves from a sample receiving site to a bridging site between a transport element and a measurement region. A reagent transport solution is employed which comprises enzymes capable of reacting with the analyte to produce hydrogen peroxide, where horseradish peroxidase may catalyze a reaction resulting in the formation of a detectable boundary in the measurement region. The distance of the boundary is indicative of the amount of analyte in a sample.

Abstract: A self-contained assay device is provided, where an analyte may be detected or be quantitated by measuring the distance of a detectable signal from a predetermined site. The device employs two strips separated by a gap, where a flow path is completed by movement of a sample receiving pad into the gap. The movement of the sample receiving pad also results in release of a reagent solution which is then transported through the pad into the quantitation area where the amount of analyte may be determined. Various chemistries may be employed for providing a detectable signal.

Abstract: Test carrier for the analysis of fluids with a frame (2) consisting of at least two parts surrounding a test field opening (6) and with a test field disposed in the test field opening (6). In order to provide such a test carrier with frame with which it is possible to assemble the test field out of several test layers manufactured separately from one another, it is proposed that the test field be designed as a test layer package (7) with test layers (10, 11, 12) resting loosely on one another, the frame (2) comprise two shaped pieces of plastics material, one of which serves as base part (4) and comprises a seat (16) for accommodating the test layers (10, 11, 12), while the other serves as lid part (3) and comprises a bearing surface (17) resting on the topmost layer (10) of the test layer package (7).

Abstract: Disclosed is a dipstick test device for detecting an analyte in a liquid sample by treating the analyte with at least one liquid reagent to form a detectable reaction product. The device includes: a) an aqueous impermeable, aqueous insoluble reaction zone, adapted to retain the detectable reaction product; and b) a control absorbent above, and in liquid-transferring relation with, the reaction zone. The control absorbent has a predetermined, limited liquid-absorbing capacity, and the dipstick is sized and configured for insertion into a vessel containing the sample, with the control absorbent oriented above the reaction zone, so that the control absorbent fills to capacity with sample and the reaction zone incubates with the sample. The device may further include an absorbent reservoir which can be moved into liquid transferring contact with the reaction zone.

Abstract: The present invention deals with a process and device for the separation of a body fluid from particulate materials in the fluid to be used for a chemical analysis of the fluid components. The process and device are in particular suitable for the separation of plasma from whole blood. Furthermore the present invention relates to a testing kit for the above mentioned separation and analysis purposes. The device has a collector membrane of defined capacity which intimately contacts the small pore side of a separator membrane having asymmetric pores passing through it permitting the application of a body fluid to the large pore side of the separator membrane.

Abstract: Test carrier for the analytical determination of a constituent of a sample fluid by a specific binding reaction between two binding partners having biological affinity. A plurality of test layers is so disposed that they are wetted successively by the fluid and form a fluid transport path, in which one of the test layers is a fixing layer (18) which is a porous carrier matrix. The first of the two binding partners is fixed to the latter. The fluid containing the second binding partner flows through the fixing layer (18), at right angles to its surface, on the test carrier (10).A largely complete binding reaction in an extraordinarily short time is achieved during the flow through the preferably very thin fixing layer (18) by the fact that a microporous plastics layer with a pore size P of at least 0.

Abstract: A device for colorimetric assay of at least one component in a liquid sample, which device comprises a support having a through hole with an area of from 3 to 80 mm.sup.2, a transparent porous film which is provided on the support to cover the hole, a reagent layer provided on a surface of the porous film which is not contacted to the support, and a sample-holding layer which covers the reagent layer and a part of a surface of the support, whereby an amount or concentration of at least one component in the liquid sample may be easily and accurately measured.

Abstract: An analytical element for quantitatively assaying an analyte by measuring reflection density in the range 320 to 360 nm. The element comprises a reagent layer and a registration layer. One of such layers contains a dye which has a low absorbtivity band from 320 to 360 nm and a high absorbtivity band from 640 to 720 nm.

Abstract: A device for the rapid qualitative and quantitative determination of the presence of a reactive ligand in a fluid.This device comprises a first reaction zone in which there is an at least temporarily impermeable membrane designed to receive a sample of test fluid and to be associated with at least one labeled reagent; a second reaction zone which is bounded on the one hand by the said membrane and on the other by a second at least temporarily impermeable membrane comprising a solid phase containing a reference reagent; and a third reaction zone which contains means for developing the reaction.A method for the rapid qualitative and quantitative determination of the presence of a reactive ligand in a fluid.Applications to the detection of the presence, in a biological fluid, of antibodies or antigens in particular.

Abstract: High density lipoprotein-cholesterol determination is made employing a device which allows for removal of red blood cells, measurement of sample volume, removal of LDL and VLDL, and quantitation of HDL-cholesterol on a quantitation strip.

Abstract: An integral multilayer analytical element comprising a reagent layer containing an indicator reagent composition capable of producing a detectable change corresponding to an analyte and a porous spreading layer composed of a fibrous fabric superposed on the reagent layer, wherein the yarn of said fabric comprises fibers having roughed surface, and an integral multilayer analytical element comprising a water-absorptive layer containing a hydrophilic polymer and a porous spreading layer composed of a fibrous fabric containing an indicator reagent composition capable of producing a detectable change corresponding to an analyte superposed on the water-absorptive layer, wherein the yarn of said fabric comprises fibers having roughed surface.The rouging is carried out, for example, by alkali etching.

Abstract: For collecting a batch of liquid samples, such as in the laboratory testing of body fluids, there is provided a collecting sheet having an array of resiliently deflectable fingers formed in the sheet. The fingers can be deflected out of the plane of the sheet to dip into respective liquid containers such as wells in a microtiter plate so as to absorb liquid samples therefrom. When released, the fingers snap back into the plane of the sheet retaining the liquid samples therein.

Abstract: An improved method for measuring the concentration of HDL-associated cholesterol in a blood-fluid sample. The method includes (a) adding a volume of the sample to an absorptive matrix (i) formed of glass fibers and (ii) effective to separate soluble from precipitated blood through the matrix from a sample-application site to a sample-collection site in the matrix, (b) releasing into the matrix, dextran sulfate and magnesium ions in an amount effective to selectively precipitate LDL and VLDL in the fluid sample, and (c) assaying fluid sample which has migrated through the matrix for the presence of lipoprotein-bound cholesterol. The improvement in the method comprises treating the glass fibers by reaction with bis(hydroxyethyl)aminopropyltriethoxy silane or by coating the fibers with polyvinyl alcohol, thereby affording substantially 100% recovery of HDL applied to the matrix.

Abstract: The invention concerns a test carrier for the determination of ions containing a test layer which has a liquid-resistant, organic phase which contains a hydrophobic polymer in a homogeneous mixture with a hydrophobic, organic liquid of low volatility and an ionophore, as well as a substance which changes its colour in the presence of the ion to be determined. The test carrier is characterized in that the test layer contains particles with an oil number of 80-200 and the ionophore is homogeneously dispersed in the hydrophobic, organic phase.

Abstract: Improved self-contained automated assay devices are provided which allow for reliable release of eluent solution upon opening of a pouch with scoring teeth, so that the solution is transferred to a well for carrying out the assay. The improvements comprise using a bibulous member which is moved into the pouch to initiate eluent solution transport or providing for a sudden shock to the solution to initiate flow.

Abstract: A microassay card for a 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: An integral multilayer analytical element for the analysis of an ammonia-forming substrate comprising:(I) a light-transmissive, liquid-impermeable support:(II) an ammonia indicator layer containing a reagent capable of undergoing a detectable change by gaseous ammonia;(III) a liquid barrier layer which allows gaseous ammonia passing therethrough;(IV) an ammonia-forming substrate reaction layer containing a reagent capable of reacting with an ammonia-forming substrate to form gaseous ammonia;(V) an intrinsic ammonia trapping layer containing a reagent which acts on intrinsic ammonia to convert it into a form which can not reach said reaction layer; and(IV) a porous spreading layer, in a laminate form.

Abstract: A liquid transfer device of disposable one-time use form to conduct a biochemical diagnostic or other assay comprises two liquid flow channels (10,110,210; 20,120,220) leading from a respective pair of channel ends to a common site (30,130,230) and operable to deliver liquid to this site in sequentially timed manner following simultaneous application of such liquid to the channel ends. Typically respectively different reagents (11,111,211; 21,121,221) are incorporated in the two channels, and a third reagent (31,131,231) at the common site, whereby a sample to be assayed in respect of a particular content can be applied to the site, immobilized by the third reagent, subsequently subjected to one channel reagent to detect any of the content of interest, and finally subjected to the other channel reagent to exhibit for the user any detected content.

Abstract: Test carrier for analyzing a sample fluid with several test layers which form a sample fluid transport path and contain a reagent system which reacts with the sample fluid to produce a detectable signal. The test carrier includes a reservoir layer of absorbent material, a detection layer arranged in the fluid transport path downstream the reservoir layer, in which a detectable signal is formed, and a separating layer arranged between the reservoir layer and the detection layer. The separating layer makes a two-step process possible. Fluid contact between the reservoir layer and the detection layer arises only with pressure loading of the layer assembly of the reservoir layer, separating layer and detection layer. A more uniform optical detection signal, and consequently better accuracy, can be achieved because the separating layer is made up of a hydrophilic material, wich is in the form of a lattice-shaped structure, in which the mean width of the lattice openings is more than 0.

Abstract: A dry analysis element for the analysis of iron ions, which is improved in selectivity so that iron ions can be analyzed reliably at a high sensitivity without the interferences by the presence of hindering Cu.sup.2+ and/or Zn.sup.2+ ions. The analysis element comprises a detection reagent layer containing Nitro-PAPS acting as a chelating agent and a cationic compound, and a pre-treating layer containing a Cu.sup.2+ -specific chelating agent. The analysis element further includes a pH buffer for keeping the pH value of the detection reagent layer within the range of from pH 3.0 to 5.0. The pH adjusting buffer may be contained in either one of the detection reagent layer or the pre-treating layer, or may be contained in another layer. The detection reagent layer may be composed of a coloring reagent layer containing Nitro-PAPS acting as the chelating agent, and a diffusion-preventing layer laminated on the coloring reagent layer and containing the cationic compound.

Abstract: A test device having the following meritorious effects is obtained in accordance with the present invention by using at least one composition selected from the group consisting of ink compositions for detecting glucose, for detecting protein, for detecting urobilinogen, and for detecting occult blood in a body fluid, and for detecting the pH thereof:a) The test device is stable during storage in atmospheric air for a long period of time, presenting no discoloration phenomenon;b) The test device has high sensitivity coupled with excellent measurement performance;c) The regions for detecting glucose and the other body fluid ingredients and the pH can be formed directly on the surface of the test device by printing, allowing the test device to be formed by mass production and the process steps to be reduced; andd) The ink compositions for detecting glucose, etc. are stable, and can be handled easily.

Abstract: Test carrier for the analysis of fluids with a test field (7) held in a frame (2), in which the frame (2) comprises a top part (3) and a base part (4) and at least the top part (3) comprises a test field opening (6) through which a sample fluid can be applied to the surface (7a) of the test field. Simplified handling and improved analytical reliability are achieved by the fact that the base part (4) comprises a seat (16) for the test field (7) which is surrounded by positioning elements (15) which are higher than the test field (7). The test field opening (6) is greater than the test field (7), so that the rim (18) of the test field is visible. The top part (3) comprises pressure tongues resting on the surface (7a) of the test field (7) and projecting into the test field opening (7).

Abstract: The specification discloses a fecal occult blood test device capable of determining whether the blood found during the test originated in the upper or lower gastrointestinal track. A fecal sample is applied to a test medium charged to be differentially attractive to blood components originating in the upper and lower gastrointestinal track respectively. A solvent is applied to the test specimen to cause differential migration of the blood components and an indicator is then applied to indicate the presence of the blood components, if any.

Abstract: Water soluble polymers are useful in combination with cobalt(III) redox reagents. When incorporated with the polymers, the cobalt(III) reagents exhibit improved sensitivity compared to fresh solutions of the reagents. In preferred embodiments, the cobalt(III) reagents are coated on a support using the water soluble polymer as a binder. Small areas of the coated support are then cut out and placed in a buffer solution to provide a working reagent solution. The solution is particularly useful in the testing of urine for significant bacteriuria.

Abstract: A diagnostic test strip for chemically determining whole blood analytes comprises a support, a porous detection zone membrane affixed to the support, and an overlay membrane affixed to the support and in overlying and continuous contact with the detection zone membrane. The overlay membrane has a crenating agent for the exclusion of whole red blood cells from the pores of the detection zone membrane.

Abstract: Methods are disclosed for conducting assays. One such method comprises providing in combination a first bibulous member zone ("first zone") and a liquid medium containing a component. The first zone has non-diffusively bound thereto a reagent interreactive with the component. Conditions are selected wherein the liquid medium and at least a portion of the component contained therein traverse all of the first zone and migrate by capillary migration into a second bibulous member zone ("second zone"). The second zone is of a different composition than the first zone and is incapable of specifically binding the component except when an analyte is to be detected and the method further includes causing a reagent to become bound to the first bibulous member zone in relation to the amount of analyte present.

Abstract: Apparatus and method are provided for the production of pairs of visual signals indicative of the concentration of an analyte in a sample for analysis. The apparatus comprises pairs of analyte detection regions, each pair of detection regions comprising a region for performing sandwich-type immunoassays and a region for performing competition-type immunoassays. The intensity of the visual signal in the sandwich-type imunoassay analyte detection region increases with increasing analyte concentration, whereas the intensity of the visual signal in the competition-type immunoassay analyte detection region decreases with increasing analyte concentration.

Abstract: There is described an assay element suitable for use in an automated analytical test instrument for assaying a fluid sample. The element includes a thin porous member possessing a high degree of capillarity such as a fibrous mesh pad supported within a guide defined by surfaces contiguous the porous member. The dimensions of the porous member and its degree of capillarity are such as to provide for capillary transport of fluid through the member. A fluid dispenser and a fluid collecting chamber are disposed contiguous to opposed ends of the porous member. The fluid dispenser is formed as a well with a port at the bottom of the well, the port being contiguous the porous member and having a ridge extending along a perimeter of the port. The ridge protrudes into the porous member a distance sufficient for entraining fluid present in the well to propagate within the member rather than along an interface between a surface of the member and guide surfaces which hold it in place.

Abstract: Biologically active reagents are prepared from particles of copolymers having highly reactive carboxy or equivalent groups. The reagents are prepared by covalently attaching biologically active substances, for example antibodies, to the particles, directly or indirectly through highly reactive carboxy groups on the particle surface. These reagents are used to advantage in analytical elements, methods for the detection of specific binding ligands (such as immunological species) and immunoassays, and in purification methods as affinity chromatography reagents.

Abstract: Reagents and methods for the determination of analytes are disclosed, using water soluble cobalt(III) complexes and metallizable dyes to form cobalt(III) complexes of the metallizable dyes. Analytes which can be determined include enzymes, cells and biological reductants, such as NADH, NADPH and ascorbate. Amplification is provided since one equivalent of the analyte provides more than one equivalent of the detectable species.