Abstract: Apparatus and method are provided for determining the concentration of an analyte in a fluid test sample by applying the fluid test sample to the surface of a working electrode which is electrochemically connected to a reference electrode which surface bears a composition comprising an enzyme specific for the analyte. A mediator is reduced in response to a reaction between the analyte and the enzyme. An oxidizing potential is applied between the electrodes to return at least a portion of the mediator back to its oxidized form before determining the concentration of the analyte to thereby increase the accuracy of the analyte determination. Following this initially applied potential, the circuit is switched to an open circuit or to a potential that substantially reduces the current to minimize the rate of electrochemical potential at the working electrode. A second potential is applied between the electrodes and the current generated in the fluid test sample is measured to determine analyte concentration.

Abstract: Disclosed is a method for the determination of urinary protein and creatinine in a single reaction vessel using a continuous process. The method involves adjusting the pH to a level suitable for carrying out an immuno assay for the protein and making such a determination by an immuno agglutination technique. Raising the pH to a level suitable for determining the creatinine quickly dissipates the cloudiness caused by the agglutination reaction, so that the creatinine determination can be carried out without delay.

Abstract: Disclosed are a method and device for performing sequential analytical reactions involving a first dry reagent and a second dry reagent comprised of two or more components having different rates of solubilization. The invention enables one to fully solubilize the components of the second reagent before they are brought into contact with each other to thereby avoid interference with the reaction kinetics which result when one or both of the components are not fully dissolved prior to their being brought into contact. The invention is especially useful in conjunction with immunoassay formats involving latex bound antibodies and polymeric agglutinators.

Abstract: An immobilized hapten reagent for use in a specific binding assay for the determination of a hapten or binding analog thereof in a liquid test sample and methods for preparing and using the immobilized hapten reagent. The immobilized hapten reagent comprises a hapten moiety covalenty linked substantially only to the external surface of a gel particle. The immobilized hapten reagent is prepared by forming a reaction mixture comprising the hapten moiety and the carrier material in a nonswelling solvent wherein the gel particle is substantially impervious to the hapten moiety and wherein an analytically insignificant amount of the hapten moiety is nonspecifically bound to the gel particle. The immobilized hapten reagent is characterized by being substantially stable in aqueous solutions and exhibits an insignificant amount of leakage of the hapten moiety into a liquid test medium.

Abstract: An analytical method for determining the relative amount of a particular hemoglobin derivative, e.g., glycated hemoglobin, in a blood sample wherein the amounts of both total hemoglobin and the hemoglobin derivative are measured and related mathematically, e.g., as a percentage. The blood sample is treated with the combination of a thiocyanate salt and an oxidant to denature the hemoglobin in the sample and to convert hemoglobin to met-hemoglobin. Met-hemoglobin is measured spectrophotometrically to give the amount of total hemoglobin present, and the denatured hemoglobin derivative can be distinguished and measured by immunoassay. The presence of the oxidant in the denaturant solution has been found to increase the rate of enaturation of hemoglobin thereby reducing the overall assay time and improving the reliability of the determination.

Abstract: A method for chemically coupling a controllable number of ligands, e.g., haptens, to a polymeric material by derivatization of the polymer with an activating agent to introduce a couplable functional group. The derivatization is performed in the presence of a blocking agent which is reactive with the same functionality on the polymer as the activating agent. By reacting the polymer with a mixture of a predetermined ratio of excess amounts of the activating and blocking agents, a controllable number of couplable functional groups are introduced to the polymer for subsequent linkage to the desired ligand. The resulting polymer-ligand conjugates are useful as reagents in immunoassays, particularly immunoturbidimetric assays.

Abstract: A latex agglutination immunoassay method for determining an analyte in a blood sample in which the pH of the reaction mixture is maintained at about 8.5 or greater in order to overcome nonspecific agglutination of latex particles by hemoglobin present in the sample. The method is particularly applicable to the determination of glycated hemoglobin, e.g., Hb Alc. In another embodiment, native hemoglobin (Ao) can be determined based on its ability to cause agglutination of latex particles suspended in an aqueous solution having a pH of about 8 or below.

Abstract: An immobilized hapten reagent for use in a specific binding assay for the determination of a hapten or binding analog thereof in a liquid test sample and methods for preparing and using the immobilized hapten reagent. The immobilized hapten reagent comprises a hapten moiety covalently linked substantially only to the external surface of a polyacrylamide gel particle. The immobilized hapten reagent is prepared by forming a reaction mixture comprising the hapten moiety and the carrier material in a nonswelling solvent wherein the gel particle is substantially impervious to the hapten moiety and wherein an analytically insignificant amount of the hapten moiety is nonspecifically bound to the gel particle. The immobilized hapten reagent is characterized by being substantially stable in aqueous solutions and exhibits an insignificant amount of leakage of the hapten moiety into a liquid test medium.

Abstract: A novel compound useful in detecting leukocytes, esterase and protease in a test sample. The compound has the structure ##STR1## in which: A is an acid residue, R is lower alkyl, aryl, carboxyl, carboxyl ester, amido or cyano, R* is H or lower alkyl, and X is O, S, or NR', in which R' is H, lower alkyl or aryl.

Abstract: A method for preparing an ester having the structure ##STR1## in which A is an acid residue; R, same or different is H, lower alkyl, aryl, or in which both R together form a ring structure and R' is H, lower alkyl or aryl. The method comprises combining a first compound having the structure ##STR2## and a second compound which is an acyl halide corresponding to A, said combining being performed in the presence of an organic acid.

Abstract: A novel compound useful in detecting leukocytes, esterase and protease in a test sample. The compound has the structure ##STR1## in which: A is an acid residue, R is lower alkyl, aryl, carboxyl, carboxyl ester, amido or cyano, R* is H or lower alkyl, and X is O, S, or NR', in which R' is H, lower alkyl or aryl.

Abstract: Disclosed is a novel, 2 component Giemsa stain. The stain comprises a first component which is an aqueous solution of methylene blue, Azure B and a preservative and a second component which is an acetone/dimethyl formamide/water solvent system containing the sodium salt of eosin Y and a buffer. The Giemsa stain effect is obtained by first fixing a blood slide with methanol and then applying the freshly mixed first and second components of the stain. The slide is then rinsed and dried to prepare it for examination.

Abstract: A novel compound is disclosed having the structure ##STR1## in which R is H or lower alkyl, R* is intermediate alkyl, and X is halogen or pseudohalogen. Also disclosed is a method for preparing the compound, the method including the steps of reacting (intermediate alkyl)benzene (I) with succinic anhydride to form (intermediate alkyl)-benzoylpropionic acid (II), successively reducing and dehydrating (II) to form 7-(intermediate alkyl)-1-tetralone (III), alkylating (III) to form 2-hydroxy(lower alkylidene)-7-(intermediate alkyl)-1-tetralone (IV), acrylating (IV) to form 2-acyloxy(lower alkylidene)-7-(intermediate alkyl)-1-tetralone (V), reacting (V) in the presence of an cycloalkene to form 7(intermediate alkyl)-2-(lower alkyl)-1-naphthol (VI), reacting (VI) with a 2,6-dihaloquinone-4-haloimide to form the compound (I), and isolating it.

Abstract: Disclosed is a Romanowsky stain having improved stability characteristics which comprises a methanol solution of Methylene Blue, an azure dye and the free acid of Eosin Y.