Abstract: The present invention provides a simple method for the stabilization of a peptide in a biological sample and a reagent for the stabilization, a simple method for the preservation of a biological sample comprising a peptide and a reagent for the preservation, and a method for the accurate measurement of a peptide in a biological sample and a reagent for the measurement. Addition of a saccharide to a biological sample enables the stabilization of a peptide in the biological sample, the preservation of the biological sample comprising a peptide in a stable condition and the accurate measurement of a peptide in the biological sample. As the present invention can stabilize a peptide in a biological sample collected in the clinical examination, the peptide as a marker in the biological sample can be measured accurately in the clinical examination.

Abstract: The present invention provides a simple method for the stabilization of a peptide in a biological sample and a reagent for the stabilization, a simple method for the preservation of a biological sample comprising a peptide and a reagent for the preservation, and a method for the accurate measurement of a peptide in a biological sample and a reagent for the measurement. Addition of a saccharide to a biological sample enables the stabilization of a peptide in the biological sample, the preservation of the biological sample comprising a peptide in a stable condition and the accurate measurement of a peptide in the biological sample. As the present invention can stabilize a peptide in a biological sample collected in the clinical examination, the peptide as a marker in the biological sample can be measured accurately in the clinical examination.

Abstract: A reagent, kit and method for the quantative determination of ascorbic acid in a sample uses ascorbate oxidase which catalyzes the reaction of reduced ascorbic acid to oxidized ascorbic acid and hydrogen peroxide. Ascorbic acid in the sample is reacted with oxygen in the presence of the ascorbate oxidase, chromogen and peroxidase. Absorbance is determined and compared with a known calibration curve.

Abstract: The present invention relates to a method for quantitatively determining a peroxidation-active substance, hydrogen peroxide or a coumarin derivative represented by formula (I) or (II): ##STR1## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are the same or different and each represents hydrogen, substituted or unsubstituted lower alkyl, substituted or unsubstituted aralkyl, substituted or unsubstituted aryl or halogen; the method comprising reacting the hydrogen peroxide with the coumarin derivative represented by formula (I) or (II) or its salt in the presence of the peroxidation-active substance, and determining the amount of the light emission or the light intensity from the reaction solution.

Abstract: The object of the invention is to provide a reagent for quantitatively determining creatine kinase with improved storability in liquid form as well as a method for quantitatively determining creatine kinase with stable measurements. Disclosed are a method for quantitatively determining creatine kinase, which comprises activating creatine kinase in a sample in an aqueous medium in coexistence with a trivalent phosphorus compound and a sulfhydryl-containing compound and then determining creatine kinase activity; a method for stabilizing a sulfhydryl-containing compound, which comprises allowing a trivalent phosphorus compound to coexist with a sulfhydryl-containing compound; and a reagent for quantitatively determining creatine kinase, which comprises a trivalent phosphorus compound, a sulfhydryl-containing compound, and a reaction substrate for creatine kinase.

Abstract: Disclosed is a chemiluminescent method of quantitatively determining one of peroxide, a peroxidation-active substance or a pyrazolopyridopyridazine derivative represented by the formula (I): ##STR1## wherein R.sup.1 represents hydrogen, lower alkyl, optionally substituted aryl, optionally substituted heterocyclic group, substituted sulfonyl, substituted sulfinyl, substituted thio etc.; R.sup.2 represents hydrogen, lower alkyl, optionally substituted aryl, etc., or a salt thereof; characterized by subjecting an unknown amount of one substance selected from the peroxide, peroxidation-active substance and pyrazolopyridopyridazine derivative to react with a known amount of the remaining two substances.

Abstract: Disclosed is a method for stably storing a liquid diagnostic reagent, comprising air-hermetically keeping the liquid diagnostic reagent in a closed container in the presence of a disoxidant therein. Preferably, at least one of the liquid diagnostic reagent and the disoxidant is covered with a separating container made of a material pervious to oxygen but not to solutions. The liquid diagnostic reagent may comprise an enzyme or an indicator.

Abstract: The present invention relates to a method of quantitative determination of sodium ions in a sample using .beta.-galactosidase, wherein the .beta.-galactosidase reaction is conducted in the presence of at least one chelating agent selected from of 1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid, ethylenediamine-tetraacetic acid, triethylenetetranine-hexaacetic acid, diethylenetriamine-N,N,N',N",N"-pentaacetic acid, 1,3 -diminopropan-2-ol-N,N',N'-tetraacetic acid, ethylenediamine-N,N'-dipropionic acid dihydrochloride, ethylenediamine-tetrakis(methylenesulfonic acid), iminodiacetic acid, hydroxyimino-diacetic acid and nitrilotriacetic acid.The method of quantitative determination of sodium ions of the present invention is useful in clinical examinations and the accuracy in the measurement by the method is high.

Abstract: A method for stabilizing urease in an assay reagent for determination of urea nitrogen in a sample and a method for accurately determining urea nitrogen in a sample are disclosed. After urea nitrogen in the sample is reacted with urease in the presence of an organic boron compound, the amount of ammonia formed by the reaction is determined.

Abstract: A method for quantitating accurately 1,5-anhydroglucitol, fructose or amylase in a sample that contains galactose using an enzymatic determination involves a pretreatment which removes galactose from the sample by an enzyme reaction in which galactose is a substrate.

Abstract: Glucose 6-phosphate dehydrogenase is stabilized in a clinical assay reagent with at least one stabilizer selected from among hydroxylamines, aldehyde scavengers dimethylthiocarbamoyl chloride, 2-(2-aminoethylamine) ethanol, and their salts. The reagent may be in liquid or lyophilized form.

Abstract: A method for determination of an analyte in a sample containing reducing substances is disclosed. After the decomposition of the reducing substances by reaction with hydrogen peroxide formed by enzymatic Redox reaction using a component in the sample which does not participate in another enzymatic Redox reaction using the analyte, the remaining hydrogen peroxide is decomposed, and then the analyte is subjected to enzymatic Redox reaction to form hydrogen peroxide which is then determined by a known method.

Abstract: The present invention provides a method for the determination of a compound having mercapto group which comprises reacting the compound with a chromogen represented by the following general formula (I): ##STR1## wherein Y is hydrogen or hydroxyl; R.sub.1, R.sub.2 and R.sub.3 may be the same or different, and are groups represented by the following general formula (II), (III) or (IV): ##STR2## wherein Z (which may be the same or different) is hydroxyl, amino, substituted amino, alkyl, substituted alkyl, alkenyl, aryl, substituted aryl, acyl, halogen, nitro, sulfo, carboxyl or alkoxy; n is 0, 1, 2, or 3; provided that at least one Z in R.sub.1, R.sub.2 and R.sub.3 is hydroxyl, amino, or substituted amino, in the presence of peroxidase or thiol oxide reductase, and determining the pigment thus formed.

Abstract: Disclosed is a method for the colorimetric determination of hydrogen peroxide in a sample by reacting a particular chromogen with the hydrogen perioxide in the presence of peroxidase and measuring the absorbancy of the reaction solution in the visible or near inflared ray region. Also disclosed is a test composition for carrying out the determination.

Abstract: The present invention provides a method for the determination of NAD(P)H which comprises reacting a chromogen represented by the following general formula (I): ##STR1## wherein Y is hydrogen or hydroxyl; R.sub.1, R.sub.2 and R.sub.3 may be the same or different, and are groups represented by the following general formula (II), (III) or (IV): ##STR2## wherein Z is hydrogen, hydroxyl, amino, substituted amino, alkyl, substituted alkyl, alkenyl, aryl, substituted aryl, acyl, halogen, nitro, sulfo, carboxyl or alkoxy; n is 1, 2, or 3; provided that at least one Z in R.sub.1, R.sub.2 and R.sub.3 is hydroxyl, amino, or substituted amino; and Z.sub.s in Z.sub.n may be the same or different, with NAD(P)H in the presence of (1) peroxidase or thiol oxide reductase and (2) diaphorase or an electron carrier, and determining the pigment thus formed.

Abstract: A method and test composition for colorimetrically determining hydrogen peroxide in a sample includes a chromogen of the formula: ##STR1## which is reacted with hydrogen peroxide in the sample in the presence of peroxidase. The absorbancy of the reaction solution is then measured.

Abstract: The present invention provides a method for the determination of bilirubin which comprises reacting the bilirubin with a compound represented by the formula ##STR1## and determing the pigment thus formed.