Showing papers on "Color reaction published in 1997"

Spectrophotometric micro-method for the determination of ethanol in commercial beverages

Abstract: A sensitive spectrophotometric method for the determination of ethanol with potassium dichromate was developed Chromium(VI), in 7 mol L-1 perchloric acid, reacts quantitatively with ethanol to form chromium(III) and acetic acid The reaction is complete in about 15 min at room temperature and the chromium(VI) consumed may be determined by the decrease of the absorbance at 267 nm The analytical working parameters (such as acidity and ionic strength of the solution, temperature and time of the reaction, chromium(VI) concentration, matrix interferences) were optimized The apparent molar absorptivities of chromium(VI), in the monomer and dimer form, and the equilibrium quotient for the dimerization reaction were determined in 3 mol L-1 perchloric acid solution The method was applied to the analysis of micro samples of commercial beverages (beers, wines and spirits) without the previous distillation of ethanol

Spectrophotometric Determination of Chlorpromazine

Abstract: Chlorpromazine hydrochloride reacts with cerium ammonium nitrate to give a pink colour having maximum absorbance at 530 nm. The reaction is selective for chlorpromazine, 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 0.5 mg/ml of chlorpromazine. The standard deviation does not exceed 0.050. The method was successfully applied to pure and pharmaceutical dosage forms of chlorpromazine. The quantitative assessment of tolerable limits of other drugs was also studied.

Spectrophotometric Determination of Barbituric Acid

Abstract: Barbituric acid reacts with chloral hydrate in alkaline media, after heating for 1 min. at 100°C to give an orangish yellow colour having maximum absorbance at 450 nm. The reaction is selective for barbituric acid with 0.01 mg/ml as the visual limit of quantitation and provides a basis for a new spectrophotometric determination. The colour reaction obeys Beer's Law from 0.001 to 0.6 mg/ml and the relative standard deviation is 1.1%. The quantitative assessment of tolerable amounts of other drugs is also studied.

Spectrophotometric determination of some antipsychotic phenothiazines

Abstract: Thioridazine hydrochloride reacts with sodium nitrite and antimony(III) potassium tartrate in the presence of hydrogen peroxide to give a yellowish orange colour having maximum absorbance at 420 nm. The reaction is specific for antipsychotic phenothiazines with 1 μg/ml as visual limit of identification and provides a basis for a new Spectrophotometric determination. The colour reaction obeys Beer's Law from 0.01 to 1.25 mg/10ml thioridazine. The standard deviation does not exceed 0.050 mg/10 ml. The method is successfully applied to pure and pharmaceutical preparations of antipsychotic phenothiazines, as well as to urine samples. The quantitative assessment of tolerable amounts of other drugs is also studied.

Evaluation of healthiness of concrete and repairing of deteriorated concrete

Abstract: PROBLEM TO BE SOLVED: To simply and accurately measure the deterioration depth of concrete corroded by a sulfuric acid component by utilizing the color reaction of a reagent as a sulfuric acid ion judging method. SOLUTION: At first, a fragile part crumbling into decay is removed by the sulfuric acid component. Next, concrete from which a core is removed is measured on the spot. The presence of sulfuric ions is judged by utilizing the color reaction of a reagent. For example, when a 0.2% aq. sol.. of chloroforfonazo III is sprayed and a 2% barium chloride aq. soln. is sprayed, the impregnation part of sulfuric ions shows a green color and a not- impregnated part shows a redish-purple color when an 0.2% aq. soln. of dimethylsulfonazo III is sprayed and a 2% aq. soln. of barrium chloride soln. is sprayed, the impregnated part of sulfuric ions shows a redish-purple color and the non-impregnated part shows a bluish-green color.

Spectrophotometric determination of Isoproturon and Metoxuron in technical and formulation grade samples using citric acid-acetic anhydride reagent

Abstract: A spectrophotometric method for the determination of Isoproturon and Metoxuron in technical and formulation grade samples based on the reaction with citric acid-acetic anhydride reagent has been developed. The absorption maxima of the coloured compounds so formed are 408 and 409 nm and the molar absorptivities are 1.69 x 10 2 and 1.13 x 10 2 L mol -1 cm -1 respectively. The reaction variables have been optimized and the reaction mechanism is discussed. The method is simple, convenient and successfully applied for the determination of Isoproturon and Metoxuron in technical and formulation grade samples. The percent relative standard deviation is found to be in the range 0.6-1.55 for Isoproturon and 1.24-1.90 for Metoxuron.

9,9‘-Bis(fluorenylidene) and Tetra-n-heptylammonium Iodide for the Measurement of Ozone Concentrations in Organic Media

Abstract: The two title compounds were shown to be useful reagents for determination of ozone and peroxides in organic media and at temperatures as low as −78 °C. 9,9‘-Bis(fluorenylidene) is a highly colored hydrocarbon whose quantitative disappearance upon reaction with ozone can be followed spectrophotometrically. Tetra-n-heptylammonium iodide, a nonhygroscopic organic-soluble iodide, reacts quantitatively with ozone and peroxidic materials yielding iodine, which can be measured by the usual methods. Reaction and measurement conditions for both systems were also studied.