Showing papers on "Color reaction published in 1999"

A new rapid method of glycolate test by diethyl ether extraction, which is applicable to a small amount of bacterial cells of less than one milligram.

Abstract: The glycolate test is a method to discriminate N-acyl groups of muramyl residue in peptidoglycan of bacterial cell walls by color reaction without purification of the cell walls. The glycolyl residue presents red purple color by heating with 0.02% 2,7-dihydroxynaphthalene (DON) dissolved in concentrated H2SO4. Instead of the previous column methods for quantitative analysis, a qualitative method by solvent works was developed to simplify and to miniaturize the analysis. In this method, solvents played two roles, removal of interfering materials and extraction of glycolic acid from the cell hydrolysates. Of several solvent systems tested, diethyl ether was studied in detail on such properties as the efficiency of glycolic acid extraction under several conditions, the ability of removing various interfering compounds, and the advantage on evaporation procedure of the solvent from extracts. DON reaction of the second diethyl ether extract from cell hydrolysate of “Micromonospora nigra” JCM 3328 showed a clear red purple color of a strong absorbance at 530 nm, which is the same as that of authentic glycolic acid. The solvent method was applied to 20 strains of typical actinomycete species whose acyl types have already been known (Uchida and Seino, 1997). All glycolate test positive strains showed the clear red purple color mentioned above, whereas acetyl type strains revealed no apparent color by the same procedures. Additional experiments indicated that the glycolate test could be determined with less than 1 mg of actinomycete cells by using a smaller amount of DON reagent and ordinary polypropylene tubes. The new method was discussed for advantages in the identification of actinomycetes and for possible applications to other fields.

A Selective Colorimetric Method for the Determination of Penicillins and Cephalosporins with α-Aminoacyl Functions

Abstract: A simple, sensitive and selective colorimetric method is described for the assay of ampicillin, amoxicillin, cephalexin, cefadroxil and cefaclor in their pharmaceutical preparations. The method is based on measuring the color obtained when the alkaline degradation products of these agents are allowed to react with ascorbic acid. The factors affecting the color generation and determination were studied and optimized. The reaction is selective to β-lactam antibiotics having amino acid side-chains with free amino functions and thus allow interference-free quantitation of some preparations containing these agents in combination with other β-lactam agents. The procedure is also successfully adopted as stability-indicating method for cephalosporins. A tentative mechanism of the color reaction is proposed.

Spectrophotometric Determination of Imipramine-HCI in Pure and Pharmaceutical Preparations

Abstract: Imipramine-HCl reacts with ammonium vanadate in the presence of HCl to give a green colour having maximum absorbance at 400-410 nm. The reaction is selective for imipramine-HCl with 0.001 mg/ml as visual limit of quantitation and provides a basis for a new spectrophotometric determination. The colour reaction obeys Beer's law from 0.001 mg to 0.05 mg/ml of imipramine-HCl and the relative standard deviation is 1.1%. The quantitative assessment of the tolerable amount of other drugs is also studied. The method has been applied to pure drugs as well as to commercial preparations and is precise and reproducible.

Interference of thiol-compounds with dextrinizing activity assay of α-amylase by starch-iodine colour reaction: Modification of the method to eliminate this interference

Abstract: Interference of Luria broth and other bacteriological media with the starch–iodine colour assay of the dextrinizing activity of α-amylase (Fuwa's method) was observed, complete bleaching occurring with 0.4ml of the Luria broth. The interference was found to be due to the thiol groups present in the medium which compete with starch for iodine. Among the various metal salts tested for counteracting the interference, ZnSO4 was found to be the best which reverted the colour to about 73–85% of that of the blank. A combination of hydrogen peroxide (10 μl of 30% solution) and CuSO4 · 5H2O (50 μl of 0.1 M solution) completely protected the starch–iodine reaction in the presence of even 0.5 ml of Luria broth and a modified assay was developed based on this finding. The colour intensity, however, was almost double than that obtained for the same amount of starch and iodine in the absence of these protective agents. Nevertheless, with different concentrations of starch as well as with varying amounts of enzymes, the modified method showed perfect linearity and could be effectively used for estimation of dextrinizing activity of α-amylase in the presence of thiol groups.

Spectrophotometric Determination of Hydrogen Peroxide Using β-CD-Hemin as a Mimetic Enzyme of Peroxidase

Abstract: Various mimetic enzymes have been systematically studied concerning the color reaction for hydrogen peroxide oxidizing 4-aminoantipyrine (4-AAP) and N,N-diethylaniline (DEA) to yield a dye. The results have shown that β-CD-hemin is the best mimetic enzyme for peroxidase among those tested, and that DEA is a quite good substrate for β-CD-hemin. Meanwhile, the chromogenic reaction rate and sensitivity of 4-AAP-DEA-β-CD-hemin system for determination of hydrogen peroxide were investigated. Zero to 8.4×10-5 M hydrogen peroxide was determined with good accuracy and reproducibility. The molar-absorption coefficient of the chromogenic compound for hydrogen peroxide determined was found to be 1.65×104 mol l-1 cm-1.

Quantification of blood cell activity with ELISPOT-assay

Abstract: of EP0957359Determining the activity of human or animal cells, especially blood cells, comprises incubating the cells in the presence of cell reaction inducing foreign substances, using and ELISA spot method. The reactive cells release a substance, which results in a color reaction on the specific spots. The color reaction is used as a measure of the cell reactivity. Independent claims are also included for: (1) a microtitre plate, especially a 96 hole plate, where the floors of the holes have an area of less than 15 (especially less than 10) mm ; and (2) a kit comprising (1) and all the relevant agents, such as capture antibodies and antigens, and color reagents.

Method and kit for simply judging elution amount of component in sample

Abstract: PROBLEM TO BE SOLVED: To simply and speedily judge an elution amount of a predetermined component from many samples by setting a water-repellent plate, an aqueous solution for eluting a target component in the sample to be tested, an aqueous solution containing a color reagent making a color reaction to the target component and a separator for dropping the aqueous solution by every predetermined amount. SOLUTION: An elution aqueous solution 3 which contains a color reagent and can elute a target component is dropped on a sample 2 to be tested on a water-repellent plate 1. As a result, a drop of the aqueous solution in the shape of a pseudo ball is formed because of the water repellency of the plate 1, in which the sample 2 is enclosed. The target component in the sample 2 is eluted in the aqueous solution, and the eluted component and the color reagent progress a color reaction. Since the color reaction between the target component eluted from the sample 2 and the color reagent proceeds in the liquid drop 5 on the water-repellent plate 1, a concentration change of the target component can be recognized by visually judging a hue change of the liquid drop 5 by a naked eye 9.