Color reaction

About: Color reaction is a research topic. Over the lifetime, 1194 publications have been published within this topic receiving 19579 citations.

Spectrophotometric Determination of Trace Amounts of Iodide by Its Catalytic Effect on the Chlorpromazine-Hydrogen Peroxide Reaction

Abstract: A catalytic photometric method for the determination of trace amounts of iodide is proposed. In the presence of iodide, chlorpromazine is oxidized by hydrogen peroxide in a sulfuric acid solution to form a red intermediate, which is further oxidized to a colorless compound. The reaction is followed by measuring the increase in the absorbance at 525nm; the maximum absorbance is obtained on an absorbance-time curve at a given reaction time. Since the maximum value increases with an increase in the iodide concentration, this value is used as a parameter for the iodide determination. Under the optimum experimental conditions (1.0×10-3M chlorpromazine, 1.5M sulfuric acid, 2.0M hydrogen peroxide, 30°C), iodide in the range 0.2-10μg l-1 can be determined. The relative standard deviations are 0.8, 2.6 and 4.2% for 6.0, 2.0 and 0.6μg l-1 iodide, respectively. Although iodate shows the same catalytic effect as iodide at the same concentration as iodine, free iodine shows a somewhat lower catalytic effect. The procedure has been applied to the determination of iodide in natural water samples.

Microcapsules containing oils and soluble color reaction components, their manufacture and use in color reaction recording systems

Abstract: A process for microencapsulating hydrophobic oils with color reactants, dissolved therein, of color reaction systems by reacting a water-soluble non-ionic melamine/formaldehyde precondensate and a water-soluble polymer in an oil-in-water dispersion for forming the capsule envelope is described The special feature of this process is that, for stabilizing the oil-in-water dispersion, an aqueous solution of a cationic melamine/formaldehyde precondensate and the aqueous solution of a water-soluble polymer are mixed with vigorous stirring, a solid precipitating as a very fine suspension in the mixture, the mixture thus obtained and containing the very finely suspended solid is mixed with ther oil, containing the color reactant in solution, with vigorous stirring, the oil-in-water dispersion thus obtained in acidified and an aqueous solution of a water-soluble non-ionic melamine/formaldehyde precondensate is added with stirring, in order to form the capsule envelope The use of the cationic melamine/formaldehyde precondensate leads to the precipitation of a very finely suspended reaction product thereof, whereby all the reaction systems in the course of the process are stabilized Excellent capsules can be obtained without formation of agglomerates The invention also relates to the microcapsules obtainable by the above process and to their advantageous use in color reaction recording systems

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.

Rapid Extraction Spectrophotometric Determination of Platinum Using Anisaldehyde-4-Phenyl-3-Thiosemicarbazone as a Chromogenic Reagent

Abstract: The synthesis, spectral characteristics and analytical applications of anisaldehyde-4-phenyl-3-thiosemicarbazone (APT) are described. A simple, rapid, selective and sensitive spectrophotometric method for the determination of platinum was developed based on the colour reaction between platinum (IV) and anisaldehyde-4-phenyl-3-thio-semicarbazone (APT) in the pH range 1.7 - 3.0. The yellow coloured species has an absorption maximum at 360 nm. The complexation is complete within 1 min. A five-fold excess of the reagent is required for complete complex formation. Beer's law is obeyed over the concentration range 0.1 -20 ppm of Pt(IV). The mtilar absorptivity and Sandell's sensitivity are 1.58 × 104 l. mol−1 cm−1 and 0.0123 ug of Pt(IV) cm−2, respectively. The effects of pH, time concentration of reagent, order of addition of reagents and the interference from various ions were investigated. The method has been employed for the determination of platinum in synthetic mixtures whose composition correspo...

Method for detection of periodontal disease

Abstract: Improvements in methods for determining the presence of suprathreshold amounts of aspartate aminotransferase in an oral fluid sample by (1) incubation of aspartate aminotransferase substrate materials in a first reaction mixture with the sample to form a first reaction product and (2) detection of reaction product therein by incubation with an indicator substance in a second reaction mixture wherein a second colored reaction product is formed. The improvement comprises (a) utilizing a diazonium dyestuff as the indicator substance in the second reaction and (b) modifying reaction conditions within the first and second reaction mixtures such that no visually detectable colored reaction product will be formed in the second reaction mixture by subthreshold level of aspartate aminotransferase but wherein a visually detectable color reaction product will be formed in the reaction mixture when a selected suprathreshold concentration of aspartate aminotransferase is present in the first reaction mixture.