Flow-injection determination of acetone with diazotized anthranilic acid through a fluorescent reaction intermediate

Acetone and diazotized anthranilic acid react in alkaline solution, giving a fluorescent intermediate that can be measured at excitation and emission wavelengths of 305 and 395 nm, respectively. Based on this, a fluorimetric flow-injection method is proposed for the determination of acetone in aqueous solution. Under the proposed conditions, acetone can be detected at concentrations higher than 8 × 10⁻⁷ M, with a linear application range from 1 × 10⁻⁶ to 2 × 10⁻⁴ M and an R.S.D. of 2.7% (1.0 × 10⁻⁵ M, n = 10). A sampling frequency of 24 h⁻¹ is achieved. Some potentially interfering species are investigated.     

Determination of certain phenothiazine drugs with diazotized p-nitroaniline

A colorimetric method for the determination of 7 phenothiazine drugs by interaction with diazotized p-nitroaniline has been developed. Neither the degradation products of the drugs nor the common excipients in pharmaceutical preparations interfere.     

Photometric determination of alpha-ketoglutaric acid with diazotized sulphanilic acid

A new photometric method for the determination of alpha-ketoglutaric acid is presented. It is based on the colour reaction of alpha-ketoglutaric acid in sodium hydroxide solution with diazotized sulphanilic acid in the presence of sodium sulphite and sodium hypophosphite. This method is highly sensitive and fairly selective for alpha-ketoglutaric acid, and may be suitable for the determination of the acid in complex samples.     

Colorimetric determination of theophylline and aminophylline with diazotized p-nitroaniline

The reactions of theophylline and aminophylline with diazotized p-nitroaniline in alkaline medium have been studied and developed into a sensitive assay for both drugs. The yellow azo-dyes formed with theophylline and aminophylline show maximum absorption at 440 and 410 nm respectively. Beer's law is valid within the concentration range 2–16 μg/ml for theophylline and 1–8 μg/ml for aminophylline. All variables which affect the reactions were studied and optimized. The proposed method has been successfully applied to determination of the drugs in their commercially available dosage forms. Statistical analysis of the results revealed that the proposed method is as precise and accurate as the official USP procedure.     

Kinetics of coupling of diazotized sulfanilamid with 1-naphthylamine

In this study, the coupling kinetics of sulfanilamid diazonium salt with 1-naphthylamine has been studied by spectrophotometric method. In the experiments conducted at constant temperature, 25°C, pH has been varied between 2.2?3.4, reactant concentration between 1.25 × 10^?5 ? 5 × 10^?5 M, and ionic strength between 0.1?1 M. The reaction has been confirmed to be of second-order and rate constants and the dissociation constant of 1-naphthylamine have been calculated. © 1993 John Wiley & Sons, Inc.     

Some products of the coupling of gossypol with diazotized amines

Summary A series of products of the coupling of gossypol with diazotized amines has been obtained. It has been established that they are monoadducts. The possibility of using them as dyes for cotton fabric has been shown.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 607–609, September–October, 1976.     

Flow-injection spectrophotometric determination of phenolic drugs and carbamate pesticides by coupling with diazotized 2,4,6-trimethylaniline.

A flow-injection (FI) spectrophotometric system is proposed for the determination of phenols and carbamates. In the FI manifolds, the solutions of phenols or carbamates (the latter after hydrolysis with NaOH) were injected into a diazonium ion carrier stream at pH 9.5 (buffered with tetrahydroborate), which was formed by mixing 2,4,6-trimethylaniline (TMA) with nitrate in a sodium dodecyl sulfate aqueous micellar medium. Absorbance was measured at 550 nm. The system combines the advantages derived from the use of TMA for the coupling of phenols in basic micellar media, because of the inhibition of the self-coupling reaction of the reagent, with the precision and speed of the FI procedures. Other diazotized reagents produced excessive blank signals. The procedures were successfully applied to the determination of phenolic drugs (epinephrine, acetaminophen, and gualacol) in pharmaceuticals and carbamates (bendiocarb, benfuracarb, carbaryl, carbofuran, methiocarb, promecarb, and propoxur) in pesticide products and water samples.     

Structure and spectra of diazotized o-aminonaphthols and their isomeric monosulfonic derivatives

The structure and behavior of o-naphthoquinonediazides and their monosulfonic acids in media of different acidity were studied by means of UV and IR spectra. In neutral, weakly acid and weakly alkaline solutions the diazo compounds of 1,2- and 2,1- aminonaphthols and their sulfonic acids exist in equilibrium as the diazonium and quinonediazide forms. The sulfonic acids, and also their metal salts, possess an ionic structure; the sulfonyl chlorides of the quinonediazides are not ionized. It was shown that of the two extreme equilibrium forms of the diazo compounds the quinone diazide was the more photosensitive. The nature of the phototransformation products of 2,1-naphthoquinonediazide depends to a considerable degree on the medium which causes a shift into one or the other of the diazo forms.     

Spectrophotometric determination of aniline in aqueous solution by azo-dye formation with diazotized p-nitroaniline

A simple, sensitive, and rapid Spectrophotometric method for the trace determination of aniline in aqueous solution is described. The method is based on coupling aniline with diazotizedp-nitroaniline in the presence of ethanol and sodium hydroxide to form an intense red water-soluble azo-dye which shows maximum absorption at 505 nm and greater stability and sensitivity in the presence of cetyltrimethylammonium bromide. Beer's law is obeyed over the aniline concentration range 0.2–2.4g/ml in the solution measured; the molar absorptivity is 3.46×10⁴l· mole^–1·cm^–1, and the relative standard deviation 1–2%, depending on the aniline concentration.     

Reaction of 1,3-diphenylbarbituric and 1,3 -diphenyl-2-thiobarbituric acids with diazotized sulfanilamides

The reaction of 1,3-diphenylbarbituric and 1,3-diphenyl-2-thiobarbituric acids with diazotized sulfaniiimides gives 1,3-diphenylalloxan and 1,3-diphenyl-2-thioalloxan phenylhydrazones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1276–1279, September, 1971.     

A simple method for labelling proteins with211At via diazotized aromatic diamine

A simple and rapid method for labelling proteins with²¹¹At by means of a 1,4-diaminobenzene link is described. 1,4-diaminobenzene is transformed into the diazonium salt and subsequently reactions of both²¹¹At and proteins with the diazonium salt take place simultaneously. For possibly high yields of astatized protein an appropriate temperature of 273 K was found. The results demonstrate the difference between the reaction mechanisms of iodine and astatine with proteins.     

Photometric assay of 1-naphthylamine by azo dye formation with diazotized sulfisomidine - application to waters

A simple and sensitive photometric method for the trace determination of 1-naphthylamine has been worked out. The method is based on the coupling reaction of the determinand in acidic medium with diazotized sulfisomidine, to form a purplish violet water-soluble mono azo dye that shows maximum absorption at 540 nm with a molar absorptivity of 4.47 x 10(4) l mol(-1) cm(-1). Beer's law is obeyed over the concentration range 5-70 mug of 1-naphthylamine in a final volume of 25 ml, i.e. 0.2-2.8 p.p.m. with a relative error of -0.7 to +1.7% and a relative standard deviation of 0.35-4.2%, depending on the concentration level. Moreover, the method does not require either temperature control or solvent extraction. Interferences due to foreign species have been examined. The developed method has been applied to the determination of 1-naphthylamine in river water and sea water.     

Theory of reversible associative-dissociative diffusion-influenced chemical reaction. I. Geminate reaction

A many-particle, in the general case, inhomogeneous reacting system of independent pairs of reactants, where geminate reversible reaction A+B?C takes place, is considered in the framework of the kinetic theory approach. The kinetic equations in the thermodynamic limit are obtained, and important relations between kinetic coefficients characterizing the reaction course are established, as well as the relations between the kinetic dependencies under different initial conditions including the relations that extend the familiar literature results to the case of rather realistic model of the reacting system. Universal long-term kinetic laws of the reaction course are determined.     

Automatic determination of reaction mappings and reaction center information. 2. Validation on a biochemical reaction database

The correct identification of the reacting bonds and atoms is a prerequisite for the analysis of the reaction mechanism. We have recently developed a method based on the Imaginary Transition State Energy Minimization approach for automatically determining the reaction center information and the atom-atom mapping numbers. We test here the accuracy of this ITSE approach by comparing the predictions of the method against more than 1500 manually annotated reactions from BioPath, a comprehensive database of biochemical reactions. The results show high agreement between manually annotated mappings and computational predictions (98.4%), with significant discrepancies in only 24 cases out of 1542 (1.6%). This result validates both the computational prediction and the database, at the same time, as the results of the former agree with expert knowledge and the latter appears largely self-consistent, and consistent with a simple principle. In 10 of the discrepant cases, simple chemical arguments or independent literature studies support the predicted reaction center. In five reaction instances the differences in the automatically and manually annotated mappings are described in detail. Finally, in approximately 200 cases the algorithm finds alternate reaction centers, which need to be studied on a case by case basis, as the exact choice of the alternative may depend on the enzyme catalyzing the reaction.     

Using a digital camera and computer data processing for the determination of organic substances with diazotized polyurethane foams

The possibility of using a digital camera and computer software for the estimation of the color intensity of polymeric azo compounds synthesized by the reaction of the azo coupling of diazotized polyurethane foams (PUFs) with different organic substances was studied. The method is based on photographing colored polyurethane foams with a digital camera followed by the computer processing of the color images. It was found that calibration equations are described by a descending exponent of the first order. The advantages of the proposed method are its high sensitivity due to the chemisorption concentration of substances, simplicity, and low cost. In combination with a high efficiency, compactness, and the availability of digital cameras, this allows us to recommend it for field analysis. It is shown by the example azo coupling reactions involving diazotized PUF that, using digital cameras as detectors and computer data processing, one can determine substances with a sensitivity equal to that of diffuse reflection spectroscopy.