5-Bromobarbituric Acid : A Mild and Selective Monobrominating Agent Employed in the Synthesis of the Gastrin Antagonist GR174152

5-Bromobarbituric acid (5) is a convenient reagent for the selective bromination of cyclic imine 3. A facile, in situ synthesis of this reagent involving a disproportionation reaction between barbituric acid and dibromobarbituric acid is described.     

Flow Injection Amperometric Determination of Hydrogen Peroxide at Low Level in Aqueous Solution

Abstract

A method is proposed for the flow-injection amperometric determination of hydrogen peroxide. Iodine is generated, by injecting hydrogen peroxide solution into an eluent 0.2 M in potassium iodide and 1 Min sulphuric acid and 5×10^?3M in Mo(VI) and is monitored at a platinum electrode that is being held at 0.1 V versus SCE. the rectilinearity range is from 10^?3?10^?6 M and the method is simple, accurate and compared favourably with the titrimetric method involving starch as indicator.     

A Sensitive Visible Spectrophotometric Method for Copper Using Bis-Substituted Thiocarbamoyl Trisulfides

Abstract

Bis-substituted thiocarbamoyl disulfides (thiuram disulfides) were investigated as chromogenic reagents for the analysis of copper in trichloroacetic acid solutions. It was found that hydrogen peroxide speeded color development, increased color stability and enhanced color intensity in a trichloroacetic acid-alcohol matrix. In the presence of hydrogen peroxide, all copper complexes had molar absorptivities exceeding 30,000. Bis-pentamethylene thiocarbamoyl disulfide was selected as the best commerically available reagent of those investigated. The procedure is almost interference free, silver and mercury being the most serious interference. The sensitivity is 6 × 10^?3 micrograms/cm².     

18-Crown-6-potassium Ferricyanide Complex as a Potentiometric Titrant

Abstract

An oxidimetric titrant, 18-Crown-6-potassium ferricyanide complex, has been prepared in acetonitrile. This reagent is proposed for redox titrations in aqueous - acetonitrile media of some reductant compounds. The general analytical conditions for using this complex and the procedures for potentiometric determinations of oxalate, arsenic (III), thiocyanate, nitrite, sulfite, thiosulphate and iodide ions, as well as hydrazine sulphate and hydrogen peroxide are presented.     

Colorlmetric Analysis of Malathion and Parathion Using Fluoboric Acid

Abstract

Monohydroxyfluoboric acid is described as a reagent for the determination of the organophosphorus compounds malathion and parathion. The reagent breaks the ether linkage to phosphorous to form a phosphoro-or phosphono-fluoridate which is then coloriraetrically determined by reaction with hydrogen peroxide and 2,7-diaroinofluorene. From 0.01 to 0.50 mg./ml. of the organophosphorus compounds can be determined.     

Diethylenetetra-ammonium sulphatocerate as volumetric reagent: Iodine monochloride method. Indirect determinations

In presence of 4N to N hydrochloric acid, diethylenetetra-ammnonium sulphatocerate was used as a volumetric reagent to determine indirectly potassium iodate, potassium metaperiodate, potassium dichromate, potassium bromate, ceric sulphate, hydrogen peroxide, lead dioxide and chloramine-B by the iodine monochloride method. An excess of potassium iodide added to each of the substances in the acid medium was, titrated back with a standard solution of diethylene-tetra-ammonium suphatocerate. Chloroform was used as an indicator. It was coloured violet owing to the liberation of iodine during the titralion and became very pale yellow at the end-point because of the formation of iodine monochloride.     

Photometric and Gas-Chromatographic Determination of Hydrogen Peroxide and Peroxybutanoic Acid in Oxidized Butanoic Acid

Procedures were developed for determining hydrogen peroxide and peroxy acids mixed with peroxide compounds of other classes in the oxidation products of butanoic acid with atmospheric oxygen and hydrogen peroxide. Conditions were found for the selective decomposition of hydrogen peroxide with catalase in the presence of an excess of the carboxylic acid deactivating the enzyme. The errors introduced by the acylation of hydrogen peroxide with the carboxylic acid in the course of sample treatment with the enzyme were eliminated by adding diphenyl sulfide or dimethyl sulfoxide, which selectively reduced the peroxy acids. The concentrations of hydrogen peroxide and the peroxy acid were found from the difference between the total concentration of the peroxide compounds before and after treating a sample with catalase and a sulfur-containing reagent by the photometric method using a reagent containing Fe²⁺ ions and N, N-dimethyl-p-phenylenediamine. Peroxy acids were determined by GLC from the yields of the oxidation products of diphenyl sulfide with the peroxy acid (diphenyl sulfoxide and diphenyl sulfones).     

Kinetics of the Decomposition of Hydrogen Peroxide in the Presence of Aqua-Pentacyanoferrate (II)

The decomposition of hydrogen peroxide has been studied in the presence of a large number of metal ions and their complexes^1,2). Interest in radiation chemistry of aqueous solutions where hydrogen peroxide is one of the products and the use of acidic ferrous sulphate solutions as dosimeter in these studies has particularly stimulated the investigation on the kinetics of decomposition of hydrogen peroxide in the presence of Fe⁺², Fe⁺³ and their complexes^1,2). Ferrous sulphate solution can be used as a dosimeter under acidic conditions only, as at higher pH the hydrolysis of Fe⁺² and Fe⁺³ interferes. Recent studies^3-6) have shown the possibility of using the aqueous solutions of ferro- and ferri-cyanides over a range of pH as dosimeter. In the studies of ferrocyanide and ferricyanide catalysed decomposition of hydrogen peroxide^7-11), it is suggested that the catalytic properties of hexacyano ferrates are through their hydrated products. The present study aims at studying the interaction of aquapentacyanoferrate¹¹) with hydrogen peroxide over a range of pH, concentration and temperature.     

Use of oxidation and reduction vapor generation for lowering the detection limits of iodine in biological samples by inductively coupled plasma atomic emission spectrometry

Procedures of microwave oxygen combustion and microwave acid digestion of biological samples were optimized for the subsequent determination of iodine. A new method was proposed for the generation of vapor iodine from periodate ions using hydrogen peroxide as a reductant. Procedures were developed for determining iodine in biological samples by inductively coupled plasma atomic emission spectrometry (ICP-AES) using oxidation and reduction vapor generation; these allowed the detection limit for iodine to be lowered by 3–4 orders of magnitude. The developed procedures were used to analyze certified reference materials of milk (Skim Milk Powder BCR 150) and seaweed (Sea Lettuce BCR 279) and a Supradyn vitamin complex.     

Synthesis of oxidized 1,2,3-thiadiazines by hydroperoxy-induced ring enlargement of 2-benzenesulfonylaminoisothiazolium salts

Oxidation of 2-benzenesulfonylaminoisothiazolium salts 1, 2 and their imines 3, 4 with hydrogen peroxide gave 1,2,3-thiadiazine 1-oxides 5, 6, which were converted into the corresponding 1,2,3-thiadiazine 1,1-dioxides 7, 8 using m-chloroperoxybenzoic acid. Oxidation of 5, 6 with hydrogen peroxide furnished isothiazol-3(2H)-one 1,1-dioxides 9, 10 as ring contraction products.     

HPLC Determination of Hepatic Cholesterol 7α-Hydroxylase Activity Using Immobilized Cholesterol Oxidase and Chemiluminescence Detection

Abstract

This paper describes an HPLC method for the determination of cholesterol 7α-hydroxylase activity, at high or low activity levels, that is sensitive and specific for 7α-hydroxycholesterol. The method relies on the generation of hydrogen peroxide by oxidation of 7α-hydroxycholesterol using the enzyme cholesterol oxidase which has been immobilized on porous glass beads. The hydrogen peroxide is subsequently detected by chemiluminescence generated by reaction of peroxide with bis-(2, 4, 6-trichlorophenyl)-oxalate (TCPO), a commonly used chemiluminescence reagent specific for peroxides. In the procedure, sample preparation is limited to extraction of the incubation mixture and injection of the concentrated extract.     

A Novel Fluorescent Reagent for Analysis of Hydrogen Peroxide

IntroductionTheoxidationofmanyclinicalsubstancesinbodyfluidsproducesaquantityofhydrogenperoxide ,sothedetermina tionoftracehydrogenperoxideisofconsiderableimportanceinclinicalchemistry .1Further,themonitoringofhydrogenperoxideisalsonecessarytoenvironmentalsciencesinceitisakeyspeciesinthereactionsofthetroposphere,beingin volvedinimportantreactionssuchasthecatalyzedoruncat alyzedaqueousphaseoxidationofSO2 andtheultraviolet en hancedaqueousphaseoxidationoforganicspecies.2 Uptonow ,variousmethods…     

Sodium hypochlorite as volumetric reagent

Summary In presence of 5 N to 6 N hydrochloric acid, ferrous ethylenediamine sulphate was used as a reducing agent to determine indirectly potassium chlorate, potassium bromate, potassium metaperiodate, potassium dichromate, potassium ferricyanide, potassium permanganate, potassium persulphate, hydrogen peroxide, ceric sulphate and chloramine-T. An excess of ferrous ethylenediamine sulphate added to each of the substances in the acid medium was titrated with a standard solution of sodium hypochlorite. Iodine monochloride was used as catalyst and preoxidizer and chloroform was used as an indicator. Chloroform was coloured violet owing to the liberation of iodine during the titration and became very pale yellow at the end-point because of the formation of iodine monochloride.Part I: See Z. analyt. Chem. 160, 429 (1958).     

A New Procedure for Highly Regio‐ and Stereoselective Iodoacetoxylation of Protected Glycals and α‐1,2‐Cyclopropanated Sugars

Protected glycals and α‐1,2‐cyclopropanated sugars were converted in high yields and selectivities in less than 2 h at low temperatures to 2‐deoxy‐2‐iodoglycosyl acetates or novel 2‐deoxy‐2‐iodomethylglycosyl acetates using the simple, inexpensive reagent mixture of ammonium iodide, hydrogen peroxide, and acetic anhydride/acetic acid in acetonitrile. The protected glycals gave rise to 2‐deoxy‐2‐bromoglycosyl acetates when ammonium bromide was used instead of the iodide, although longer reaction times were required and selectivities were inferior. Other simple olefins such as styrene and indene were also converted to their corresponding 1,2‐trans‐iodoacetates.     

The Use of μ-Oxo-ditrifluoroacetato-diphenyl-diiodine in Potentiometric Titrations

Abstract

The use of μ-oxo-ditrifluoroacetato-diphenyl-diiodine (μ-ODDD) in potentiometric titrations has been studied. This reagent is more powerful oxidizing agent and more stable than bis(trifluoroacetoxy) iodobenzene (BTIB). The general analytical conditions for using this oxidant and the procedures for potentiometric determinations of sulfite, thiosulphate, nitrite, selenocyanate, thiocyanate and iron(II)ions as well as hydrogen peroxide and hydrazine sulphate are described.

A simultaneous determination of hydrazine sulphate and nitrite ions and also of selôenocyanate and thiocyanate ions has been carried out.     

Localized surface plasmon resonance sensor for simultaneous kinetic determination of peroxyacetic acid and hydrogen peroxide

A new sensor for simultaneous determination of peroxyacetic acid and hydrogen peroxide using silver nanoparticles (Ag-NPs) as a chromogenic reagent is introduced. The silver nanoparticles have the catalytic ability for the decomposition of peroxyacetic acid and hydrogen peroxide; then the decomposition of them induces the degradation of silver nanoparticles. Hence, a remarkable change in the localized surface plasmon resonance absorbance strength could be observed. Spectra-kinetic approach and artificial neural network was applied for the simultaneous determination of peroxyacetic acid and hydrogen peroxide. Linear calibration graphs were obtained in the concentration range of (8.20 × 10⁻⁵ to 2.00 × 10⁻³ mol L⁻¹) for peroxyacetic acid and (2.00 × 10⁻⁵ to 4.80 × 10⁻³ mol L⁻¹) for hydrogen peroxide. The analytical performance of this sensor has been evaluated for the detection of simultaneous determination of peroxyacetic acid and hydrogen peroxide in real samples.     

Murexide reaction of caffeine with hydrogen peroxide and hydrochloric acid. II

In continuation of the study on the murexide reaction of caffeine with 3% hydrogen peroxide/hydrochloric acid and then with ammonia giving a purple coloration, we investigated the oxidation reaction of caffeine with 6% hydrogen peroxide/hydrochloric acid to isolate ten reaction products, 3-hydroxy-4,6-dimethyloxazolo[4,5-d]pyrimidine-2,5,7(3H,4H,6H)-trione 1 , 1,3-dimethylalloxan 2 , murexoin 3 , 1,3,7-trimethyl-2,6,8-trioxo-9-hydroxy-1H,3H,7H-xanthine 5 , 1,3,7-trimethyl-2,6,8-trioxo-1H,3H,7H-xanthine 6 , 1,3,7-trimethyl-2,6-dioxo-8-chloro-1H,3H,7H-xanthine 7, 5-(1,3-dimethyl-1,2,3,4,5,6-hexahydro-2,4,6-trioxopyrimidin-5-yl)-aminomethylene-1,3-dimethyl-1,2,3,4,5,6-hexahydro-2,4,6-trioxopyrimidine ammonium salt 9 , 1,3-dimethylpalabanic acid 10 , 1-methyl-2,4,5-trioxoimidazole 11 , 3-hydroxy-5,7-dimethyloxazolo[5,4-d]pyrimidine-2,4,6(3H,5H,7H)-trione 12 and 4,6,8-trimethyl-1,2,4-dioxazino[6,5-d]pyrimidine-3,5,7(4H,6H,8H)-trione 13 . The oxidation reaction using 6% hydrogen peroxide/hydrochloric acid was found to produce a similar purple coloration to that of the murexide reaction despite no subsequent addition of ammonia, indicating the liberation of ammonia by the oxidation of caffeine. Among the above compounds, the purple colored substance murexoin 3 and the yellow colored compound 9 were both ammonium salts, and compound 5 was the red colored substance. In the present investigation, these three compounds were found to contribute to the coloration.     

Study on the murexide reaction. V

Although the reaction of caffeine with hydrogen peroxide/hydrochloric acid or nitric acid and then with ammonia has been known to give a purple coloration (Murexide reaction), the use of hydrazine instead of ammonia is found to provide no purple coloration. The reaction of caffeine with hydrogen peroxide/hydrochloric acid and then with hydrazine hydrate afforded a yellow reaction mixture, from which 4-methyl-6-(N-methylcarbamoyl)-3,5-dioxo-2,3,4,5-tetrahydrotriazine 9 , oxalyl hydrazide 10 and hydroxylamine hydrochloride were isolated. The reaction of caffeine with nitric acid and then with hydrazine hydrate furnished a yellow reaction mixture, from which 8-amino-1,3,7-trimethyl-2,6-dioxo-1H,3H,7H-xanthine 11, 9 and hydroxylamine nitrate were isolated. Compound 9 was clarified to be produced from 3-hydroxy-4,6-dimethyloxazolo[4,5-d]pyrimidine-2,5,7(3H,4H,6H)-trione 3 and 1,3-dimethylalloxan 7 by the ring transformation with hydrazine.     

Elemental Analysis by Gas Chromatography-Atomic Emission Detection for the Control of a Deuterated Derivatization Reagent

Abstract

Methyl iodide is a derivatization reagent often used to methylate molecules with amine, hydroxyl or carboxylic groups before a gas chromatographic analysis. In order to improve the analytical qualities of quantitative determination by gas chromatography mass spectrometry, derivatization with reagents labelled with stable isotopes can be used. Deuteromethyliodide can be used instead of methyliodide to obtain labelled compounds easily detected, as far as the reagent is pure enough.

This paper illustrates the use of the gas chromatography atomic emission detection coupling (GC-AED) for the study of the purity of a reagent labelled with deuterium (IC²H3) used for the derivatization of a new immunoenhancer (sodium ditiocarb - lmuthiol^R) before the GC-MS determination of the parent drug and its methylated metabolite. The elements monitored simultaneously are: carbon (193.03 nm), hydrogen (656.3 nm), deuterium (656.04 nm), iodine (183.1 nm) and sulfur (180.7 nm). The chromatograms corresponding to these various elements obviously show the presence of compounds containing deuterium and I or hydrogen associated with iodine and make easier and faster the determination of the chemical pollution of the IC²H3 batch. The monitoring of the specific wavelength associated to the atomic emission of sulfur (180.7 nm) allows easy detection o f ditiocarb and its metabolite from the chromatogram made very complex by the reagent pollution.     

Analytical Studies Utilizing Steady State Hydrated Electron Conditions

Abstract

A steady state concentration of hydrated electrons, generated by a ⁶⁰Cobalt gamma source in a hydrogen saturated alkaline water solution, can be used as an analytical reagent in the determination of oxygen and hydrogen peroxide. The results are in good agreement with previous studies using pulse radiolysis.