Determination of iodine in organic compounds employing oxygen flask combustion and mercurimetric titration

Iodine in iodine-containing organic compounds is determined by oxygen flask combustion followed by mercurimetric titration. The method is the same as that used in a collaborative study on the determination of bromine and chlorine with the exception that hydrazine is used as the reducing agent instead of alkaline peroxide and the type of buret to be used for the titration is specified. Accuracy and precision are well within the acceptable limits.     

氯化炭黑中氯的分析方法

提出了改性炭黑－氯化碳黑的分析方法,即样品在管式炉中通氧灰化,使结合在炭黑有机官能团上的氯转化为可测定的无机氯,用吸收液吸收后,汞量法测定氯含量,方法简便快速,准确度高,回收率在９６．８％－１０１．７％,精密度好,相对标准偏差为１．１７％,不需用特殊仪器,适合工业生产中的监控分析。     

Simple and specific microdetermination of organoiodine via oxygen flask combustion

A rapid, simple, and reliable procedure for specific microdetermination of organoiodine is described. This procedure consists of oxygen flask combustion followed by an argentimetric titration with an iodide ion-selective electrode as indicator. Some advantages of this procedure over mercurimetric titration currently used in an AOAC method are detailed.     

Iodometric microdetermination of chlorine and bromine in some highly halogenated organic compounds

Summary Highly halogenated organic compounds are combusted in a oxygen flask using water as absorbant in the case of chlorine and 0.05% hydrogen peroxide in the case of bromine. The halogenide ion formed is determined by an iodometric procedure. Results showed an average error of ± 0.1% for Cl and ± 0.2% for Br. They are in close agreement with those obtained by a mercurimetric titration. The iodometric titration is to be preferred because of simplicity and rapidity

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Jodometrische Mikrobestimmung von Chlor und Brom in einigen hochhalogenisierten organischen Verbindungen

Zusammenfassung Die Verbindung wird im Sauerstoffkolben verbrannt, wobei Wasser (Cl) bzw. 0,05%ige Wasserstoffperoxidlösung (Br) als Absorptionsmittel verwendet werden. Die gebildeten Halogenide werden jodometrisch bestimmt. Der durchschnittliche Fehler beträgt ± 0,1% (Cl) bzw. ± 0,2% (Br). Die Ergebnisse stimmen gut mit mercurimetrisch erhaltenen überein. Die jodometrische Titration ist wegen der einfachen und schnellen Durchführbarkeit vorzuziehen.

     

Submicro methods for analysis of organic compounds : The determination of thiol groups

Several methods are described for the determination of thiol groups in organic samples weighing only 50 μg. Iodimetric methods were not widely applicable but the mercurimetric method of fritz and palmer in which thio-Michler's ketone serves as indicator was readily scaled down and gave excellent results (error ± 0.5% absolute) for all compounds tested. Diphenylcarbazone was also tried as the indicator; the procedure was satisfactory for most materials, but some anomalous results were obtained.     

Quantitative determination of amoxicillin and its decomposition products by high-performance liquid chromatography

Amoxicillin, amoxicilloates, amoxicillin oligomers and amoxicillin piperazine-2,5-dione are separated by reversed-phase (C8) high-performance liquid chromatography with gradient elution. Quantitative results are reported for a number of samples. Amoxicillin trihydrate samples mostly contain amoxicilloate as the main impurity. Samples of the sodium salt also contain the piperazine-2,5-dione and the dimer. Higher oligomers such as the trimer and tetramer were not present in significant amounts. Several samples were also analysed by a mercurimetric titration method.     

Mercurimetric Potentiometric Determination of Barbiturates Using a Solid-State Iodide Ion-Selective Electrode

Abstract

A simple potentiometric method is described for mercurimetric titration of barbiturates using a solid-state iodide ion-selective electrode. The optimum titration conditions involve the use of a borate buffer of pH 9–10 as a medium and mercury(II) perchlorate of pH 1.7–1.9 as a titrant. Under these conditions, titration curves with two sharp consecutive inflection breaks are obtained. The first inflection corresponds to quantitative and stoichiometric reaction of barbiturates with mercury(II) and the second break is due to the reaction of the buffer with the titrant. No interferences are caused by Cl^?, Br^?, PO₄ ^3- and many excipients and diluents commonly used in the drug formulations. Determination of barbiturates in various pharmaceutical preparations gives reproducible results with an average recovery of 99.1% of the nominal (st.dev. 0.3 %) and the method offers significant advantages over the titrimetric method of the British Pharmacopoeia.     

Determination of hydrogen peroxide by xenon trioxide oxidation

Aqueous xenon trioxide solution has been used as the oxidizing agent in three precise methods of analysis for hydrogen peroxide. A catalytic method, which utilizes hydrogen peroxide to initiate the reaction between t-butanol and xenon trioxide, is described for determining amounts of hydrogen peroxide as low as 0.9 microg or 36 parts per milliard (ppM). A direct spectrophotometric titration was found to have a lower limit of about 50 microg, or 20 ppM. An indirect titrimetric method was also used to determine hydrogen peroxide in amounts as low as 50 microg with a relative standard deviation of 4% which decreased to 1 % for amounts over 200 microg.     

过氧化钙制备实验的改进 ——以鸡蛋壳为原料

Instead of calcium chloride, we used egg shells as material in the experiment for synthesis of calcium peroxide. This could help to improve students' environmental consciousness and stimulate students' interest in experiment. We designed procedures for egg shells pre-treatment and the synthesis of calcium peroxide, which were suitable for students. The amount of hydrogen peroxide and ammonia was optimized. The yield of anhydrous calcium peroxide was about 70% with a great than 75% purity.     

过氧化脲在氧化反应中的应用研究进展

氧化反应是重要的有机合成单元反应,常采用H2O2或过氧酸等为氧化剂.近年来,过氧化脲作为一种清洁环保的固态H2O2,以其性质稳定、H2O2含量高(36.2%)且释放可控等优点,在众多氧化反应中得到了广泛应用.对过氧化脲在氧化反应中的应用进行了总结和概述,重点介绍了环氧化、Baeyer-Villiger氧化、N-氧化、硫醚氧化成砜和亚砜、氧化卤化等反应.     

Quantitative analysis of hydrogen peroxide by <Superscript>1</Superscript>H NMR spectroscopy

A technique utilizing ¹H NMR spectroscopy has been developed to measure the concentration of hydrogen peroxide from 10^–3 to 10 M. Hydrogen peroxide produces a peak at around 10–11 ppm, depending upon the interaction between solvent molecules and hydrogen peroxide molecules. The intensity of this peak can be monitored once every 30 s, enabling the measurement of changes in hydrogen peroxide concentration as a function of time. ¹H NMR has several advantages over other techniques: (1) applicability to a broad range of solvents, (2) ability to quantify hydrogen peroxide rapidly, and (3) ability to follow reactions forming and/or consuming hydrogen peroxide as a function of time. As an example, this analytical technique has been used to measure the concentration of hydrogen peroxide as a function of time in a study of hydrogen peroxide decomposition catalyzed by iron(III) tetrakispentafluorophenyl porphyrin.Electronic Supplementary Material Supplementary material is available for this article at     

Gas-sensing internal enzyme fiber optic biosensor for hydrogen peroxide

Feasibility is demonstrated for a novel gas-sensing, internal enzyme biosensing scheme for the selective measurement of hydrogen peroxide. Two horseradish peroxidase catalysed reactions are evaluated for the detection of hydrogen peroxide as it crosses a microporous Teflon membrane at 37 degrees C. The rate at which hydrogen peroxide crosses the membrane is determined by either a fluorescence or chemiluminescence measurement and this rate is related to the concentration of hydrogen peroxide in the sample solution. Detection limits of 0.7 mM and 10 muM are estimated for the fluorescence and chemiluminescence methods, respectively. Selectivity is demonstrated for hydrogen peroxide over ascorbic acid, uric acid and tyrosine.     

Comparison of isothermal and non-isothermal chemiluminescence and differential scanning calorimetry experiments with benzoyl peroxide

Difference in the kinetics of chemiluminescence (CL) and differential scanning calorimetry records for decomposition of originally solid benzoyl peroxide continuing as a melt reaction was outlined. While the main portion of heat measured by DSC is released in the spontaneous decomposition of benzoyl peroxide starting as a homolytic scission of peroxidic bonds, the CL light emission in oxygen comes presumably from the subsequent disproportionation reaction of polyphenyl peroxyl radicals and monitors the induced decomposition of peroxide. Thermogravimetry revealed that oxygen remains partially bound to the products of benzoyl peroxide decomposition.     

Parallel Lipid Peroxide Accumulation Strategy Based on Bimetal–Organic Frameworks for Enhanced Ferrotherapy

Ferroptosis, a nonapoptotic cell-death pathway, is commonly regulated by ether lipid peroxide generation or glutathione consumption. In this work, a parallel lipid peroxide accumulation strategy was designed based on catalytic metal–organic frameworks (MOFs) for enhanced ferrotherapy. The bimetallic MOF was synthesized with iron porphyrin as a linker and cupric ion as a metal node, and erastin, a ferroptosis inducer, was sandwiched between the MOF layers with 4,4′-dipyridyl disulfide as spacers. In a tumor microenvironment, erastin was released from the layered MOFs through glutathione-responsive cleavage. The exfoliated MOFs served as a dual Fenton reaction inducer to generate numerous hydroxyl radicals for the accumulation of lipid peroxide, while erastin-aggravated glutathione depletion down-regulated glutathione peroxidase 4; this then inhibited the consumption of lipid peroxide. Therefore, a parallel lipid peroxide accumulation strategy was established for enhanced ferrotherapy that effectively inhibited tumor growth in live mice, opening up new opportunities to treat apoptosis-insensitive tumors.     

Fluorometric determination of hydrogen peroxide using resorufin and peroxidase

A fluorometric method for the determination of hydrogen peroxide using resorufin as a substrate for peroxidase is described. Two procedures were developed for the determination of hydrogen peroxide. One involves the addition of hydrogen peroxide sample to a solution of peroxidase and resorufin in phosphate buffer, pH 6.4. Fluorescence measurements are performed before and after hydrogen peroxide addition. The within-run CVs for final concentrations of hydrogen peroxide of 200 and 40 nmol/liter were 1.7 and 7.6%, respectively, and the limit of quantitation was 9 nmol/liter. The second procedure, in which the initial reaction of hydrogen peroxide with resorufin is performed in citrate buffer at pH 4.5, and then the fluorescence is measured after the pH is adjusted to 9.2 with borate buffer, has a limit of quantitation of 4.4 nmol/liter with a within-run CV of 6.5% for a final hydrogen peroxide concentration of 20 nmol/liter. The method is linear at least up to 1 μmol/liter.     

Complications in photochemistry of organic peroxides

In spite of much active work in the photochemistry of organic peroxides particularly as photoinitiators, mechanisms for several processes are still unclear. This article discusses the following mechanistic complications in this area. These include a mechanism leading to the cleavage of the peroxide bond in the excited peroxide molecules, singlet sensitization leading to homolytic cleavage of the peroxide bond in spite of negative free energy change estimated for the sensitization as an electron transfer process, and triplet sensitization.     

Stereoselective oxy-functionalization of gamma-silyl allylic alcohols with ozone: a facile synthesis of silyl peroxide and its reactions

A reaction of gamma-silyl allylic alcohol and its ether with ozone provides synthetically versatile alpha-formyl silyl peroxide in good yield without normal fission of carbon-carbon double bond. Thus, the provided silyl peroxide serves as a good precursor for the stereochemically defined triol derivative via alkylation and reduction of peroxide moiety.     

Potentiometric determination of hydrogen peroxide with permanganate in presence of fluoride, with iron as a catalyst: Application to the titanium-fluoride-peroxide mixed complex

A potentiometric permanganate titration has been developed for the determination of hydrogen peroxide in the presence of fluoride, as well as of the peroxide content in the titanium—fluoride—peroxide mixed complex. It is based on the stabilization of manganese(III) with an excess of fluoride in a moderately acidic medium (pH close to 3) and on the use of iron(III) as catalyst. Errors are less than 0.5%.     

Development of a highly sensitive fluorescence probe for hydrogen peroxide

Hydrogen peroxide is believed to play a role in cellular signal transduction by reversible oxidation of proteins. Here, we report the design and synthesis of a novel fluorescence probe for hydrogen peroxide, utilizing a photoinduced electron transfer strategy based on benzil chemistry to control the fluorescence. The practical value of this highly sensitive and selective fluorescence probe, NBzF, was confirmed by its application to imaging of hydrogen peroxide generation in live RAW 264.7 macrophages. NBzF was also employed for live cell imaging of hydrogen peroxide generated as a signaling molecule in A431 human epidermoid carcinoma cells.