Abstract: Sensor cartridges include a fluid constituent-selective sensor membrane in direct sealing contact with a face of a flow-through sample cell in surrounding relationship to a sensor port. The sensor membrane has sufficiently large surface area so as to entirely cover the sensor port and establish an annular region in surrounding relationship thereto. It is this annular region which is in direct contact with a corresponding region of the sample cell face so as to provide self-sealing capabilities. The sensor cartridge most preferably includes a flow-through sample cell having a zig-zag or serpentine flow channel so as to provide a series of sensor ports on both of the opposed cell faces. The faces of the sample cell are most preferably provided with recessed regions which define a series of land surfaces each of which surrounds a respective one of the sensor ports.

Abstract: A system for analyzing a biological fluid or the like for a constituent of interest comprises structure defining a sample inlet port, structure defining an analysis region, a measuring system connected in sensing relation to the analysis region, and structure defining a reaction chamber that has an immobilized enzyme capable of modifying the constituent of interest. Control means operates liquid flow means in a unidirectional sample flow mode to initially flow a sample of material to be analyzed from the sample inlet port to the reaction chamber and to the analysis region for a measurement of unmodified sample material, and then operates the liquid flow means in a bidirectional sample flow mode to oscillate the sample material in the reaction chamber and facilitate modification by the immobilized enzyme of the constituent of material in the sample.

Abstract: A system for analyzing a biological fluid or the like for a constituent of interest comprises structure defining a sample inlet port, structure defining an analysis region, a measuring system connected in sensing relation to the analysis region, and structure defining a reaction chamber that has an immobilized enzyme capable of modifying the constituent of interest. Control means operates liquid flow means in a unidirectional sample flow mode to initially flow a sample of material to be analyzed from the sample inlet port to the reaction chamber and to the analysis region for a measurement of unmodified sample material, and then operates the liquid flow means in a bidirectional sample flow mode to oscillate the sample material in the reaction chamber and facilitate modification by the immobilized enzyme of the constituent of material in the sample.

Abstract: A method for determining the concentrations of total calcium and at least one monovalent ion in a sample includes the steps of mixing the sample with a diluent that has a pH within the range pH 6.5 to 7.0 and includes 2-amino-2-hydroxymethyl-1,3-propanediol phosphate and is free of the monovalent ion. An aliquot of the diluted sample is concurrently contacted with a calcium-specific ion selective electrode and an ion selective electrode specifically responsive to the monovalent ion, the response of the calcium-specific ion selective electrode is measured as an indication of the concentration of total calcium in the sample, and the response of the monovalent ion specific ion selective electrode is measured as an indication of the concentration of the monovalent ion in the sample.

Abstract: In a method for colorimetric determination of calcium, the sample to be analyzed is mixed with a dye reagent of pH value at which that reagent does not produce a predetermined change when complexed with calcium ions; a first colorimetric measurement is made on the mixture of the sample and dye reagent; a second reagent is added to the mixture of the sample and dye reagent to shift the pH and activate the dye reagent producing the predetermined change; and then a second colorimetric measurement is made on the resulting mixture, the difference between the two colorimetric measurements being a measure of calcium in the sample.