Showing papers on "Color reaction published in 1998"

Improving the Berthelot Reaction for Determining Ammonium in Soil Extracts and Water

Abstract: Colorimetric methods based on the Berthelot reaction are used widely for quantitative determination of NH 4 -N in biological and environmental samples. Studies to evaluate phenol and salicylate, the most commonly used chromogenic substrates, revealed minor interferences by metallic cations, whereas up to a threefold shift in absorbance was observed with 38 diverse N-containing organic compounds. Interferences differed markedly between phenol and salicylate. The possibility of a simple correction was precluded by the fact that interferences were both positive and negative, and depended on the temperature during color development and the concentration of NH 4 -N. Fourteen compounds were evaluated as alternatives to phenol and salicylate, of which the Na salt of 2-phenylphenol (PPS) proved to be the most promising. Using PPS, macro- and microscale batch methods and an automated flow-injection method were developed. These methods are simple, convenient, and sensitive. Using the PPS microscale method, for which the limit of detection is 0.17 mg NH 4 -N L -1 , recovery of NH 4 -N added to soil extracts ranged from 98 to 104%, with a coefficient of variation of 1.4 to 2.7%. As with phenol and salicylate, precipitation of metal hydroxides was observed. Precipitation was controlled by chelation with citrate rather than ethylenediaminetetraacetic acid (EDTA), which suppressed color development by preventing monochloramine formation. Compared with Berthelot methods that use phenol or salicylate, interference by amino acids was decreased by up to 10-fold. Interference by other organic N compounds was virtually eliminated.

Rapid urinary iodide test.

Abstract: Assessment of iodine deficiency and monitoring of iodine supplementation programs demand rapid, simple, and cost-effective methods for the determination of urinary iodide concentrations. We propose a semiquantitative rapid test, based on the iodide-catalyzed oxidation of 3,3′,5,5′-tetramethylbenzidine by peracetic acid/H2O2, to yield colored products. The color of the chemical reaction is compared with color categories of a pictogram corresponding to three ranges: 300μ g/L ( 2.36 μmol/L) of iodide concentrations. The test is very easy to perform and does not require any instrumentation or apparatus. Sample preparation is simple and consists of the removal of interfering substances by disposable columns, 65 × 10.5 mm, packed with purified activated charcoal. For comparison with a reference method for measuring urinary iodide, by high-performance liquid chromatography, we determined the iodide concentrations of 370 random (untimed) urine samples from consecutive pat...

Spectrophotometric Determination of Methyldopa in Pure and Pharmaceutical Preparations

Abstract: Methyldopa reacts with barbituric acid to give a red colour having maximum absorbance at 540 nm. The reaction is selective for methyldopa with 0.01 mg/ml as visual limit of quantitation and provides a basis for a new spectrophotometric determination. The colour reaction obeys Beer's Law from 0.1 mg to 2.5 mg/10 ml of methyldopa and the relative standard deviation is 1.1%. The quantitative assessment of tolerable amount of other drugs is also studied.

Compound 460b, its production, food additive, processing of sporozoa-parasitizing fish meat, and production of minced fish and boiled marine paste products

Abstract: PROBLEM TO BE SOLVED: To produce a new compound, 460B, which is obtained from a culture of microorganisms of Aspergillus sp., has inhibitory activity on proteolytic enzymes which decompose thiol-based proteins, a good preventive effect on jelly meat formation, and is useful as an additive for processing fish having jelly meat to minced fish meat. SOLUTION: This new compound, 460B, is produced by culturing microorganisms of Aspergirus sp. which has ability to produce the compound of the formula, 460B (for example, Aspergirus oryzae ATCC 20386), and extracting the compound 460B out of the culture. This compound is preferably added to protein to be processed in a quantity of 0.001-0.01 pts.-wt. to 100 pts.wt. of the protein. This compound has the following properties: appearance: white powder; molecular formula: C20 H30 N4 O5 ; molecular weight: 406.48; solubility: easily soluble in water, methanol, etc., insoluble in ethyl acetate and chloroform; color reaction: positive to ReydonSmith reaction and ninhydrin reaction, negative to Sakaguchi reaction and Anthron reaction; amino acid analysis: phenylalanine is detected as a result of hydrolysis with 6N hydrochloric acid.

New antiviral active substance

Abstract: PROBLEM TO BE SOLVED: To obtain the subject new substance having porphyrin-like skeleton and useful as a therapeutic agent, etc., for viral infectious diseases having antiviral activity to coat virus such as AIDS virus or herpes virus by isolating and purifying from excrement, etc., of silkworm. SOLUTION: This new compound comprises porphyrins having the following physicochemical properties: molecular weight, about 530 [FAB-MS; m/zc 144]; absorption wavelength spectrum λmax (CH3 COCH3 ), 408 and 663(nm); solubility, readily soluble in chloroform, slightly soluble in ethanol and dimethylsulfoxide and insoluble in water; color reaction, positive in iodine vapor reaction and negative in molybdenum reagent reaction, anthrone reagent reaction, naphthol reagent reaction, ninhydrin reagent reaction and sulfuric acid-acetic acid reagent reaction, etc. The compound has an antiviral activity to coat virus such as AIDS virus, herpes virus or hemagglutinating virus of Japan and is useful as a therapeutic agent for infectious diseases, etc. The substance is obtained by isolating and purifying by means of fractional precipitation, chromatography, TLC, etc., from excrement of silkworm.