Method For Determination Of Oxygen Research Articles

Praseodymium oxides. Complete characterization by determining oxygen content

Praseodymium ions are available in many oxidation states, so they are capable to form a huge number of different oxides, which make them an interesting and versatile material in many industries, such as ceramics or optics.Although praseodymium oxides behavior has been studied, the information found in the literature is sometimes contradictory. The different conditions of experimentation have led to opposite results due to rapid praseodymium oxide transformations. Many authors have pointed out the high oxygen mobility upon phase transformations during heating and cooling processes.Four materials based on praseodymium oxide compounds were characterized by physicochemical analysis. Praseodymium concentration was determined by WD-XRF and oxygen content was determined by the elemental analyzer TC-436, while XRD gave crystalline phases information and thermal analysis was carried out to obtain information about phase transformations. The combination of these analytical techniques allowed to have the real and accurate praseodymium concentration of a determined product, as it was found out that, two products that intended to have the same praseodymium concentration, were actually different.PrO2 and Pr2O3 were the major phases identified in these materials by XRD, although Pr(OH)3, and Pr6O11 were also found as minor phases in the original materials. From the results obtained by WD-XRF, XRD and simultaneous thermal analysis; crystalline phases concentration was calculated, but the determination of oxygen content by the elemental analyzer TC-436 was the key to validate the results obtained from WD-XRF, XRD and simultaneous thermal analysis. The oxygen determination method was optimized by increasing a 400% the sample weight introduced into the piece of equipment, which resulted in a precision improvement.In addition, one sample underwent different thermal treatments at the temperatures of 500, 650, 760, 980 and 1040 °C and two different cooling processes (slow cooling and quenching), to study phase transformations at these temperatures by measuring the oxygen content and determine the crystalline phases by XRD. It was found that, when the sample was quenched, different phases were formed at different temperatures, such as Pr9O16 and Pr7O12, while cooling slowly the calcined sample was always giving Pr6O11 because the intermediate phases were not stable enough to be determined.Thus, the aim of this work was to devise an adequately robust test method and use it to expand the present knowledge base concerning the praseodymium oxide physicochemical characterization and its behavior across different heating and cooling processes.

The use of oxygen content determination method based on fluorescence quenching for rapeseed oil shelf-life assessment

The knowledge of the storage characteristics over the intended shelf-life period is in the interest of the manufacturing companies and it follows from the requirements of consumers, retailers and law regulations. The aim of the study was an attempt to use non-invasive oxygen determination method based on fluorescence quenching to evaluate the shelf-life of rapeseed oil.The subjects of investigation were refined rapeseed oil samples stored at different temperature conditions (20, 40, 50 and 60 °C) under ambient air and modified atmosphere (50 °C). The samples were analyzed periodically for hydroperoxides using the iodometric method and for the oxygen content in the headspace (with the use of OxySense® 325i system).The results show that lipid degradation during storage was accompanied by oxygen loss in the headspace. The relationship between peroxide value and oxygen concentration fitted the polynomial models. The fluorescence quenching method of oxygen determination may be a suitable and rapid tool for non-destructive shelf-life evaluation of edible oils. In packaging with pure nitrogen, oxygen indicators provide valuable information on the correctness of the packaging process.

Formation of CO x species during the carbothermal reduction of oxides of Zr, Si, Ti, Cr, W, and Mo

The formation of CO and CO 2 during the reduction of ZrO 2, SiO 2, TiO 2, Cr 2O 3, WO 3, and MoO 3 by carbon was studied using two methods: (1) the carrier-gas hot-extraction method for oxygen determination in solids with the dissolution of carbon in the melt just before reduction, and (2) the usual carbothermal reduction method for carbide synthesis starting from oxide/carbon powder mixtures. In both the cases, significant amounts of CO 2 were detected for WO 3 and especially for MoO 3, in contrast to the other oxides. The kinetics of the carbothermal reduction of ZrO 2, SiO 2, TiO 2, Cr 2O 3, WO 3, and MoO 3 were studied using a micro-scale method with the in situ analysis of the reaction gases CO and CO 2. The progress of the oxide reduction reaction can be qualitatively and quantitatively measured at each moment of the experiments. Most of the results can be interpreted using the literature about oxide-specific mechanisms. In some cases, new aspects regarding the role of both species CO 2 and CO were discussed.

A Quantitative Determination of Singlet Oxygen with Horseradish Peroxidase

A singlet oxygen determination method based on the formation of dimethyl-(2,5)-2-methoxy-5-hydroperoxydihydrofuran (DMFO2) followed by acid hydrolysis with 0.1 N H2SO4 is described. Hydrogen peroxide is formed thereby as a product of hydrolysis which is then determined by the horseradish peroxidase-catalyzed formation of the homovanillic acid dimer. Since DMFO2 is a crystalline compound with sufficient stability it can be used as a primary standard for the determination. The peroxidase-catalyzed hydrogen peroxide determination allows detection of singlet oxygen concentrations as low as 10−7 M.

The effect of halothane on the reduction of oxygen on gold A method for simultaneous determination of oxygen and halothane on a single working electrode

Results are presented of a rotating ring-disc electrode (RRDE) study of the oxygen reduction reaction on gold in the presence and absence of the common inhalation anaesthetic halothane (2-bromo-2-chloro-1,1,1-trifluoroethane). Halothane is itself reduced on gold (at potentials coinciding closely with the second reduction wave for oxygen in basic solution) and this causes some passivation of the electrode surface. The mechanism of oxygen reduction differs on this surface to that on the clean gold but appears to be unaffected by increasing concentrations of halothane in solution. Hence it is deduced that the ratio of the heights of the two waves due to oxygen reduction is independent of oxygen concentration but when halothane is present is proportional to halothane concentration. This hypothesis is then tested for mixtures of the two gases in the solution phase using cyclic voltammetry at microelectrodes and in the gas phase using a clark-type sensor.

Determination of Oxygen to Uranium Ratio in Uranium Dioxide Nuclear Fuel by Differential Pulse Polarography

AbstractA differential pulse polarographic method for determination of oxygen to uranium ratio in uranium oxides is fully described. An accuracy −2.62% to +4.35% was achieved by calibrating the method against standard U3O3, replicate test runs with UO2, gave a precision of ±4.59% or better. The method is now successfully used in routine analysis for UO2 fuel.

The determination of oxygen in powdered tungsten carbide by reducing fusion: Suppression of primary carbon dioxide, selection of working conditions and adsorbed-moisture effects

A method for the reducing fusion determination of oxygen in powdered tungsten carbide is described. It is shown that, as theory predicts, tungsten carbide may evolve its oxygen content not only as carbon monoxide but also as perceptible quantities of carbon dioxide. An easy suppression of this primary carbon dioxide, and thus of any error associated with it made when computing the sample oxygen content, is obtained by the simple expedient of dropping the samples into the crucible a few seconds after having started the instrument analytical cycle, i.e. when the crucible is already at very high temperature. Criteria followed in the selection of the sample fusion conditions and their possible application to the analysis of massive tungsten carbide samples are discussed. The very large effect of the adsorbed moisture content on the results is made evident, and practical means (preliminary water desorption from samples kept at 200° under high vacuum) to overcome it are suggested.

Micro and trace determination of oxygen in organic compounds

Samples are pyrolyzed over carbon in helium doped with chloropentane, which enhances the liberation of the oxygen. The carbon monoxide formed is determined by gas chromatography. A modification of a Carlo Erba CHN+O Elemental Analyzer is described, and results of micro and trace determinations in organic and inorganic compounds are reported. Basic reactions in this method for oxygen determination are discussed.

A Gas Chromatographic Method for the Determination of Oxygen Dissolved in Water Using an Electron Capture Detector

A rapid and accurate method for the routine determination of oxygen dissolved in water is described. A small sample (10 μl) is injected onto a column packed with Porapak T, which retains the water. Subsequently, oxygen is separated from other gases on a column packed with Molecular Sieve 5A and then detected with an electron capture detector. The use of two columns of Porapak T fitted to a backflush valve permits venting of the retained water vapour from one, while a subsequent sample is being analysed on the other. An analysis takes one minute and the coefficient of variation for the oxygen contained in water saturated with the ambient atmosphere is 0.33%.

Improvement of oxygen determination method in organic compounds through addition of chlorohydrocarbon vapor to carrier gas

The addition of chlorohydrocarbon vapor to the carrier gas enhances the quantitative conversion of oxygen to carbon monoxide in the pyrolytic oxygen determination method.

Short communications

The 3He activation method for oxygen determination was applied to chalcogenide materials such as Ge 28Sb 12Se 60 and Ge 33As 12Se 55. Attention was focused on the optimization of the 3He bombardment energy for non-destructive oxygen determination and the validity of the post-irradiation chemical etch used for removing surface oxygen contamination. The procedure developed was tested on a series of chalcogenide glasses. The detection limit for this non-destructive technique using ~6-MeV 3He is estimated at ~1 ppm of oxygen.

On the reduction of oxygen in aqueous solution by electrolytically precipitated cadmium

The reduction of oxygen in aqueous solution by electrolytically precipitated cadmium, used in a reductor column, has been studied in two ways. First, by analysis of the effluent for the hydrogen peroxide formed as a reaction intermediate, the conditions for quantitative reduction have been found. Attention is called to the fact that an effluent free from hydrogen peroxide also implies quantitative reduction of all dissolved oxygen. The practical consequences are pointed out. A comparison is also made with some other reductors. Secondly, the oxidation of electrolytically precipitated cadmium by hydrogen ion is strongly inhibited, so at pH 7 it is possible to determine oxygen as the equivalent amount of cadmium ion produced in the reductor column. The conditions of quantitative reduction of oxygen are determined and found to be in agreement with those obtained by the first method. From the results the solubility of oxygen in water in equilibrium with air is estimated and found to agree with a published result considered as reliable. An outline is given of a method for determination of oxygen in aqueous solution by measurement of the amount of cadmium ions produced.

764. Comparative evaluation of methods for determination of oxygen in steels using instruments PVP and EA-1: N N Timoshenko et al, Zavodsk Lab, 37 (9), 1971, 1054–1055 in Russian)

764. Comparative evaluation of methods for determination of oxygen in steels using instruments PVP and EA-1: N N Timoshenko et al, Zavodsk Lab, 37 (9), 1971, 1054–1055 in Russian)

Combined spectroscopic and isotope method for oxygen determination in refractory metal oxides and in metals forming thermostable oxides

Combined spectroscopic and isotope method for oxygen determination in refractory metal oxides and in metals forming thermostable oxides

Radiochemical determination of oxygen traces in selenium

A sensitive method for determination of oxygen in selenium is described. Oxygen is converted into the gaseous compound sulfur dioxide labelled with35S. The β-radiation of35S is measured by liquid scintillation counting. The detection limit is 0.02 ppm. The efficiency of vacuum distillation in the purification of selenium, and the influence of air, dry oxygen and water on the absorption of oxygen by selenium have been investigated.

A convenient isotopic dilution method for the direct determination of oxygen in fluorinated organic materials

A method is described for the microdetermination of oxygen in fluorinated organic compounds. The unknown material is pyrolyzed together with18O-containing succinic acid, in a sealed, evacuated, specially-purified copper tube. After equilibration at 850°C, the tube is punctured and the pyrolysis gases are admitted to a mass spectrometer. Comparison of the m/e-46/44 ratio (C16O18O/C16O16O) to the ratio obtained from similar pyrolysis of the oxygen-18 compound only, provides a means of calculating the oxygen content of the unknown.

Further development of the electrolytic method for the rapid determination of oxygen in liquid steels

Further development of the electrolytic method for the rapid determination of oxygen in liquid steels

Accuracy of Three Methods for Determination of Oxygen in Potassium at Concentrations Less than 20 p.p.m.

Accuracy of Three Methods for Determination of Oxygen in Potassium at Concentrations Less than 20 p.p.m.

The direct determination of oxygen in organic compounds: A study of various modifications

The Schütze method for the direct determination of oxygen in organic compounds has been modified by a number of investigators. It has not always been clear whether a particular modification offers any advantage. Several of these modifications have, therefore, been examined in turn and compared. In the course of this work the gases obtained by pyrolysis have been analysed in a mass spectrometer. As a result of this examination it is recommended that the organic oxygen-containing compound be pyrolysed over platinised carbon heated at 900°, that both reduced copper and soda asbestos be used to remove interfering gases, and that the determination be completed gravimetrically after conversion of carbon monoxide to carbon dioxide with Schütze reagent at room temperature. Alternative methods of determining carbon dioxide are discussed.

Oxidation of Beta-Eleostearic Acid and Its Methyl Ester with Organic Peracids

Beta-eleostearic acid and its methyl ester were oxidized with peracetic, perbenzoic or monoperphthalic acid at temperature below 30°C.The oxidation products were viscous, and their specific gravities were more than 1.It was considered that epoxy compound is not present in the oxidation products from the data of infra-red spectra and the result of hydrogenation with lithium aluminium hydride, although the products reacted with hydrogen bromide under the condition of Durbetaki's oxyrane oxygen determination method. From the data of infra-red and ultraviolet spectra and from the acid, saponification and hydroxyl values, the oxidation products were estimated as hydroxy-acyloxy compounds. Conjugated diene was found in some of products oxidized with perbenzoic or monoperphthalic acid, and conjugated triene was found in some of products oxidized with monoperphthalic acid from the data of infra-red and ultraviolet spectra.It was estimated that reactivity of peracids with eleostearic acid or its methyl ester was in the order; peracetic>perbenzoic>monoperphthalic acids.