Abstract: A method for indicating the concentration of a substance in solution includes passing an alternating voltage between a first electrode structure having coated thereon a polymer and a second separate counter electrode in the solution. The polymer is in one of an oxidized and a reduced state, between which states its conductivity varies. Changes in the conductivity of the polymer coating are measured, the measurement being representative of the state of the polymer and thereby of the concentration of the substance in the solution. Electrodes for use in this method are also described.

Abstract: A sensor system that detects a current representative of a compound in a liquid mixture features a two-electrode strip adapted for releasable attachment to signal readout circuitry. The strip comprises an elongated support (preferably flat) adapted for releasable attachment to the readout circuitry; a first conductor and a second conductor each extend along the support and comprise means for connection to the circuitry. An active electrode, positioned to contact the liquid mixture and the first conductor, comprises a single layer deposit of an enzyme capable of catalyzing a reaction involving the compound, a conductive material, and an electron mediator, capable of transferring electrons between the enzyme-catalyzed reaction and the first conductor. A reference electrode is positioned to contact the mixture and the second conductor. The system includes circuitry adapted to provide an electrical signal representative of the current. The two-electrode strip is manufactured, e.g.

Abstract: Half-sandwich complexes of transition metals having a single .pi.-ligand with delocalised .pi. bonding are of use in mediating electron transfer between an electrode and a redox protein, for example an oxidoreductase enzyme such as in an amperometric enzyme sensor. Suitable compounds include complexes of the general formula:(.pi.-ligand)M(not-.pi.-ligand).sub.nwherein the complex is charged or neutral, .pi.-ligand represents the single .pi.-bonded ligand, M represents the transition metal atom, n is the number of ligands which are not .pi.-ligands, and the n not-.pi.-ligands are the same or different, are univalent or multivalent, and serve to satisfy the valency of the transitional metal M.

Abstract: A sensor system that detects a current representative of a compound in a liquid mixture features a two-electrode strip adapted for releasable attachment to signal readout circuitry. The strip comprises an elongated support (preferably flat) adapted for releasable attachment to the readout circuitry; a first conductor and a second conductor each extend along the support and comprise means for connection to the circuitry. An active electrode, positioned to contact the liquid mixture and the first conductor, comprises a deposit of an enzyme capable of catalyzing a reaction involving the compound and (preferably) an electron mediator, capable of transferring electrons between the enzyme-catalyzed reaction and the first conductor. A reference electrode is positioned to contact the mixture and the second conductor. The system includes circuitry adapted to provide an electrical signal representative of the current. The two-electrode strip is manufactured, e.g.

Abstract: Erythrocyte exclusion membranes suited for test strips of electrochemical sensors have a porous matrix and a mobile erythrocyte aggregating agent. The membranes typically comprise a water-insoluble hydrophobic polymer incorporating a hydrophilic polymer and with the erythrocyte aggregating agent. Such membranes can have a pore size which is several times larger than the diameter of erythrocytes, and allow rapid passage of plasma by holding back the erythrocytes as rouleaux at the surface of the membrane. The membranes are preferably made by forming in situ on a test strip using spray casting.

Abstract: An electrode strip for use in an electrochemical sensor for measuring a compound in a sample is provided, including an electrode support, a reference or counter electrode disposed on the support, a working electrode spaced from the reference or counter electrode on the support, a covering layer defining an enclosed space over the reference and working electrodes and having an aperture for receiving a sample into the enclosed space, and a plurality of mesh layers interposed in the enclosed space between the covering layer and the support, the covering layer having a sample application aperture spaced from said electrodes and said reference electrode spaced from said working electrode at a position remote from and on the opposite side of said working electrode from said aperture.

Abstract: A sensor system that detects a current representative of a compound in a liquid mixture features a two-electrode strip adapted for releasable attachment to signal readout circuitry. The strip comprises an elongated support (preferably flat) adapted for releasable attachment to the readout circuitry; a first conductor and a second conductor each extend along the support and comprise means for connection to the circuitry. An active electrode, positioned to contact the liquid mixture and the first conductor, comprises a deposit of an enzyme capable of catalyzing a reaction involving the compound and (preferably) an electron mediator, capable of transferring electrons between the enzyme-catalyzed reaction and the first conductor. A reference electrode is positioned to contact the mixture and the second conductor. The system includes circuitry adapted to provide an electrical signal representative of the current. The two-electrode strip is manufactured, e.g.

Abstract: An amperometric sensor comprises a working electrode, a reference electrode, an enzyme whose catalytic activity on a substrate results in electroactivity, and an enhancer compound which enhances the detected electroactivity.

Abstract: A disposable element is provided for use in analytical equipment for electrochemical determination of biological cells. The disposable element comprises a working electrode, a reference electrode, and a filter for retention of solids in the vicinity of the electrodes. The analytical equipment with disposable elements can be used for respiratory assays, enzyme assays or immunoassays, among other uses.In a variation, the disposable element comprises a reference electrode, working electrode and fusible link.

Abstract: A dry strip element for use in an electrochemical assay for determining theophylline in a sample, the test element carrying a working electrode and a reference electrode and separately carrying at the working electrode an alkaline phosphatase and an electroinactive phosphate ester which is a substrate for the alkaline phosphatase and from which an electroactive compound can be released by catalytic activity of the alkaline phosphatase.

Abstract: An aryl acylamidase is produced by a process which comprises culturing in a culture medium an aryl acylamidase-producing bacterial strain selected from Rhodococcus erythropolis NCIB 12273 and aryl acylamidase-producing mutants or variants thereof, and collecting aryl acylamidase-containing material.

Abstract: The present invention is concerned with a chemical sensor, more specifically with a chemical sensor which is capable of detecting the presence of, measuring a quantity of or monitoring the level of N-acetyl primary aromatic amines, such as paracetamol, in whole blood.The specification relates to a method of assay of the type in which an electrode poised at a suitable potential is contacted with a system comprising;(a) a sample suspected to contain paracetamol or a derivative thereof, and(b) an enzyme capable of catalyzing the hydrolysis of an N-acylated primary aromatic amine or a derivative thereof, and,wherein the current flowing in the electrode is a measure of the quantity of hydrolysis products formed and thereby of the concentration of N-acylated primary aromatic amine or derivatives thereof in the sample.

Abstract: A method of assay for the presence of .alpha.-amylase in a sample employs a derivatized .alpha.-oligosaccharide which can be hydrolyzed by an enzyme mix including .alpha.-amylase to yield an electroactive compound, and at least one other enzyme which with .alpha.-amylase gives an enzyme mix capable of hydrolyzing the derivatized .alpha.-oligosaccharide. The sample is contacted with the derivatized .alpha.-oligosaccharide and with the other enzyme to permit hydrolysis of the derivatized .alpha.-oligosaccharide and to allow formation of the electroactive compound. An electrode is poised at a potential at which the derivatized .alpha.-oligosaccharide is not electochemically active, the potential being one at which the electroactive compound is electochemically active. Any current arising from electrochemical activity of the electroactive compound is detected.

Abstract: A method for the assay of haemoglobin in blood is provided in which the blood is contacted with a sufficient amount of a ferricyanide and the haemoglobin is electrochemically assayed by monitoring the current changes produced on reduction of the ferricyanide by the haemoglobin.

Abstract: Hydrogen peroxide can be detected using a pyrolytic graphite edge electrode when cytochrome c peroxidase and an aminoglycoside are both present in the system.

Abstract: The present invention discloses an assay for nucleic acid which comprises the steps of;(a) providing a probe material comprising;(i) a sequence of nucleic acids complementary to a given target sequence and,(ii) a first ligand chemically linked thereto and capable of a specific binding reaction with an antiligand;(b) contacting the said probe material with an assay system comprising:(i) a suitable mediator, enzyme, substrate system capable of transferring charge to an electrode surface when the enzyme is catalytically active, and;(ii) a second ligand chemically linked to one of said mediator, enzyme or substrate, wherein the second ligand is capable of a competitive binding reaction with the antiligand, and;(iii) the said antiligand, Whereby the said first ligand competes with the said second ligand in a specific binding reaction with the antiligand, and;(c) contacting the above system with a solution suspected of containing the said target sequence whereby the binding of any of the said target sequence presen

Abstract: An electrode has a graphite surface at least part of which is an edge-plane graphite surface to which Cr(III) complexes are attached by surface C--O groups. The graphite can be polished pyrolytic graphite. The complex coverage can be 5-20%. The complex may comprise proteins, enzyme substrates, specific binding agents, intermediate metabolites or the like, e.g. the protein plastocyanin, so that direct unmediated electrochemistry is possible at the electrode.

Abstract: Electrochemical detection of mediator level is employed in a method of assay using a redox enzyme and redox substrate to detect conversion to an effective mediator by an assay enzyme label of a compound which is non-mediating under the assay conditions.