Abstract: A solid state electrode for use in determining ion concentration in an aqueous solution comprising an electrically conductive element; a first lipophilic-hydrophobic (hereinafter referred to as LH) layer in intimate contact with the element; and a second LH layer in intimate contact with the first layer. The first LH layer comprises an adhesive, LH polymer having an intrinsic viscosity of from about 0.4 to about 0.9 ml/g; and an LH plasticizer. The second LH layer comprises a LH polymer having an intrinsic viscosity of from about 1 to about 1.5 ml/g; an LH plasticizer, and an LH ion-selective ligand of the ion to be determined.Preferably, the first LH layer further comprises an LH charge carrier.As used herein, the term "lipophilic-hydrophobic (LH)" denotes an organic solvent soluble-water insoluble substance.

Abstract: A method and apparatus for determining the wavelength of a light beam wherein the light beam is directed through a liquid crystal cell functioning as a variable retarder, wherein the voltage applied to the cell is ramped to vary the retardation of the cell between maximum and minimum values, wherein the light from the beam passing through the cell is detected, wherein the intensity of the detected light is monitored, which intensity alternately passes through maximum and minimum values as the retardation of the cell is varied between its maximum and minimum values, and wherein the number of times the intensity alternates between its maximum and minimum values is determined to provide an indication of the wavelength of the light beam.

Abstract: A membrane for use in the determination of calcium ion concentration in an aqueous solution, the membrane being of the type comprising a calcium ion selective component and a carrier material.

Abstract: In a system which measures a parameter of a sample and displays information relating thereto, a circuit including the component elements of the system for testing signal levels at test points within the system and for displaying the test signal levels. Switching means places the system in either a transducing mode for measuring the parameter or in a combined transducing/self-testing mode for simultaneous testing during transducing operation. The testing circuit includes an operator manipulated probe for contacting any of the test points and an analog multiplexer input of the system for multiplexing the probe test signal and the transducing signal. The multiplexed signals are converted to digital form and processed by the system's computer for display. In the combined transducing/self-testing mode, the probe test signal information is outputted to the system display while the transducing output thereto is inhibited.

Abstract: A method of determining the concentration of antigen in a rate nephelometric immunochemical analysis wherein an observed maximum rate of change of a nephelometric signal is used to determine the antigen concentration by employing a mathematical expression derived on a semi-empirical basis.

Abstract: A liquid junction structure for an electrochemical reference electrode or a reference portion of an electrochemical combination electrode comprising an element of capillary material restrained between first and second plastic shrink tubes.

Abstract: In a system for analyzing the elemental or molecular composition of a sample where the sample components are excited through collision with an active metastable gaseous species, the excited sample components emitting a characteristic wavelength of light which may be detected, the system including a microwave cavity through which the gaseous species flows and a microwave source coupled to the cavity, the microwave discharge exciting the gaseous species, there is disclosed an improved gas and sample introduction system wherein a liquid sample and a water soluble compound are mixed with a diluent and aspirated into the flow, upstream of the microwave cavity, onto a heated filament, the compound being capable of releasing nitrogen or some other suitable gas molecules at high temperature and low pressure whereupon formation of nitrogen and vaporization of the sample occur simultaneously.

Abstract: An electrophoretic technique for assaying the relative distribution of lactate dehydrogenase (LD) isoenzymes characterized in that the electrophoretic and/or substrate buffer employed therein comprises a first and second moiety wherein the first moiety is selected from a group consisting of alkali metal 5,5-diethylbarbiturate, ammonium 5,5-diethylbarbiturate, and mixtures thereof, and wherein the second moiety is selected from a group consisting of bicine (N,N-bis(2-hydroxyethyl)glycine), tricine (N-tris(hydroxymethyl)methylglycine), and glycylglycine. The buffer has a pH of from about 7 to about 9 at 25.degree. C.Preferably, the buffer further comprises a solid organic water soluble acid and either 2-amino-2-methyl-1,3-propanediol (AMPD) or 2-amino-2-hydroxymethyl-1,3-propanediol (Tris) or mixtures thereof.Buffers within the scope of the instant invention, when compared to prior art buffers, increase the relative percentage of LD.sub.

Abstract: A sample vial guide for scintillation spectrometers or other sample handling systems in which sample vials are moved in a horizontal path to a first operating station, transferred vertically therefrom to a second station such as a radiation measuring chamber, and returned along the vertical path to the first station for continued movement along the horizontal path away from the first station. The sample vial guide includes first and second opposing jaws at the first station on opposite sides of the horizontal path and having opposing interior surfaces which surround and define a constrained area at the first station for a sample vial. The jaws are hinged to pivot laterally away from the horizontal path and include cam surfaces on each jaw for engaging a sample vial as it moves along the horizontal path to or from the first station to move the jaws to an open position to accommodate such horizontal movement of the vial.

Abstract: Improved means for expelling sample carriers which have been automatically elevated to the sample measuring chamber of a radiation measuring apparatus, from the measuring chamber. The means are collapsible within the instrument housing, as to remain therein as a sample carrier is elevated toward the measuring chamber. Additionally, the means comprise a disposable contamination member which can be removed and discarded in the event of contamination.

Abstract: Titration apparatus for measuring chloride electrolyte in blood samples including a pair of coulometric generating electrodes (anode and cathode) for titrating the chloride with silver ions to precipitate silver chloride and a pair of amperometric detecting electrodes for detecting uncombined silver ions following complete titration of the chloride and hence for signaling the endpoint of the chloride titration. A predetermined potential difference is applied across the amperometric electrodes, and an operating condition of zero current flow is established through one of the amperometric electrodes. Current flow between the amperometric electrode and the coulometric anode is monitored to indicate the presence of uncombined silver ions and thereby the titration endpoint.

Abstract: Photometric analysis apparatus in which a sample to be optically measured is stirred by a rotating magnetic stirring element within a container holding the sample. An optical path through the container and through the sample therein intersects the rotational path of the stirring element and is hence obstructed by the stirring element in one or more rotational positions. Rotation of the stirring element is controlled in a manner which stops rotation thereof in a position out of the optical path thereby allowing optical measurement of the sample material unobstructed by the stirring element.

Abstract: In a system for analyzing the elemental or molecular composition of a sample wherein the sample components are excited through collision with an active metastable gaseous species, the excited sample components emitting a characteristic wavelength of light which may be detected, the system including a microwave cavity through which the gaseous species flows and a microwave source coupled to the cavity, the microwave discharge exciting the gaseous species, there is disclosed an improved liquid sample introduction system which causes complete vaporization and disassociation of the sample. The sample is preferably aspirated directly into the microwave discharge within which the active gas is generated. A novel sample and gas injection probe is also disclosed.

Abstract: A method of flameless atomic absorption analysis in which an element in a sample is measured by vaporizing the sample in a graphite crucible or cuvette and measuring the absorbance of the atomic vapor at a wavelength characteristic of the element. The method includes the steps of (1) successively introducing a preselected number of aliquots of the same sample into the graphite cuvette, (2) thermally pretreating each sample aliquot upon introduction to remove volatile or decomposable substances therefrom, and (3) vaporizing sample remaining in the cuvette for measurement only after performing the predetermined successive number of sample introduction and thermal pretreatment cycles.

Abstract: Pipetting and diluting apparatus including an interchangeable syringe pump of predetermined volume capacity and a stepper motor for driving the syringe piston at a selected speed for dosing a selected volume of fluid. The piston stroke is calculated from the syringe volume capacity and the volume of fluid to be dosed. Control means controls the acceleration and deceleration characteristic of the piston in accordance with an exponential function dependent upon the selected piston speed and the syringe volume capacity.

Abstract: Apparatus for conveying a blood sample through a flow cell which measures characteristics such as pH, PCO.sub.2, and PO.sub.2 of the sample and for pumping a wash solution through the cell between samples. The flow cell inlet is selectively connected (1) to a sample-filled syringe for driving sample through the flow cell or (2) to a reservoir of the wash solution. The flow cell outlet is connected by a conduit to a waste receptacle. A rotor of a combined peristaltic pump and valve coacts with an elastomeric tubular section of the conduit. The rotor and the elastomeric section are movable in a transverse direction relative to each other between (1) a first or pumping position wherein the rotor compressively engages the section for pumping fluid wash solution through the cell and the conduit and (2) a second or relaxed position wherein the rotor is released from the section to provide an open unrestricted channel for the flow of sample driven by the syringe through the cell.

Abstract: An enzymatic reagent is provided for use in the kinetic measurement of the concentration of an enzyme substrate present in a sample and possessing the Michaelis-Menten relationship between reaction rate and substrate concentration. The reagent includes an enzyme such as glucose oxidase, uricase or urease for reacting with corresponding enzyme substrates such as glucose, uric acid or urea. In addition, the reagent includes a nonreacting competitive inhibitor of the enzyme. The inhibitor is present in an amount sufficient to improve the linearity of the reaction rate-concentration relationship associated with the enzyme substrate reaction at concentrations which are low relative to the Michaelis-Menten constant, Km, for the particular enzyme substrate reaction. The improved linearity, in turn, improves the accuracy of the kinetic measurements of substrate concentration made by linear output analyzers especially in an upper portion of the predetermined range where the relationship is particularly nonlinear.

Abstract: A short path liquid junction structure is defined through a porous ceramic layer coated circumferentially on an electrochemical electrode glass body by an elastomeric O-ring sealing member circumferentially engaging the ceramic layer in an annular line contact seal. The length of the liquid junction path is the short distance through the porous ceramic layer around and past the line contact seal.

Abstract: There is disclosed a circuit for generating an error voltage which is proportional to the difference between a desired value of a physical parameter and the actual value of the physical parameter. The circuit operates by alternately switching the current from a source through a fixed reference resistor and a variable resistor, the resistance value of which changes as a function of the physical parameter to be controlled. The current is switched between the two resistors so that the average voltage generated across the variable resistor would be equal to the average voltage generated across the fixed resistor if the physical parameter had the desired value. By determining the difference between the average voltages across the resistors, the error voltage can be generated for controlling the physical parameter.

Abstract: A method of determining the need for post-addition of antigen or antibody to an antigen-antibody reaction to ascertain whether the reaction is in an antigen excess or an antibody excess condition. The time rate of change of a nephelometric signal developed from the reaction is monitored to generate a rate signal having a peak value providing a measure of antigen concentration. The post-addition step is performed only if the peak rate value is ambiguous--, i.e. if it indicates one antigen concentration value for a reaction in antigen excess but another value for a reaction in antibody excess. The need for the post-addition step is determined from measured qualities of the rate signal including one or more of (1) the peak rate value, (2) the elapsed time from the start of the reaction to the peak rate, and (3) the product of the peak rate and the elapsed time. When required, the post-addition step may be performed during progress of the antigen-antibody reaction after measurement of the peak rate value.