Neutron activation analysis of high purity Selenium: Determination of Bromine

Neutron activation analysis for 2–0.8 p.p.m. bromine in selenium was performed by irradiating i-g samples for 2 h at a neutron flux of 4.10¹¹ n/cm²/sec. The bromine was separated by a double precipitation technique as silver bromide to obtain adequate decontamination and the isotope ⁸²Br (T_{$\text{1}\text{2}$}=35.87 h) measured. Errors due to self-shielding in the standards and flux-depression in the selenium were calculated. Measurements on 2 different photopeaks were made to avoid errors from interfering isotopes.     

A simple method for carrier-free separation of77Br from metallic selenium

A simple method was developed for separation of bromine from metallic selenium. This method enables easy preparation of⁷⁷Br by proton bombardment of metallic selenium (enriched⁷⁷Se or⁷⁸Se). The method consists of heating the metallic selenium with H₂O to 300°C in a small autoclave for about three hours. The⁷⁷Br is distilled from the obtained solution after the addition of H₂SO₄+K₂Cr₂O₇. The step also removes the arsenic produced together with the selenium.     

Millimeter-wave rotational spectrum and molecular constants of diatomic gallium bromide

Gas-phase spectra of four isotopic species of GaBr have been detected in the millimeter wavelength region. The molecules were produced by a flame reaction of gallium and bromine at 1000° C. From the rotational spectra molecular constants have been determined for ⁶⁹Ga⁷⁹Br,⁶⁹Ga⁸¹Br,⁷¹Ga⁷⁹Br,⁷¹Ga⁸¹Br. The equilibrium internuclear distance is r_e = 2.3524907(82).     

The application of activation analysis for the control of bromide accumulation in vegetable

Soil desinfestation with methyl bromide increases the uptake of bromine by plants. According to the tolerance regulations in the FRG only 30–50 ppm Br are allowed. The bromine uptake by plants depends on: (a) the fumigation technique (applied amounts, reaction time, date of cultivation); (b) the growing conditions (soil type, climate and irrigation); (c) the plants (species, rotation, harvesting time etc.). The INAA is a simple and rapid method to analyse bromine in vegetables within a wide range using⁸⁰Br and⁸²Br. Since several years this method was also used to control imported crops.     

The determination of bromine in dry biological material by instrumental neutron activation analysis

Procedures for the determination of bromine by the reactions⁸¹Br(n, γ)⁸²Br (T=35.4 h) and⁷⁹Br(n, γ)^80mBr (T=4.4 h). In the case of⁸²Br a flat coaxial Ge(Li) crystal is used to measure the 619 keV photopeak. For^80mBr a planar Ge(Li) detector is applied to measure the 39 keV γ-ray. The agreement between the data obtained with both techniques for some Standard Reference Materials is satisfactory.     

Investigation of nitroxide radical coupling reaction in wide temperature range and different catalyst system

The effect of temperature, catalyst system, and the structure of bromine connected groups on the nitroxide radical coupling (NRC) reaction is investigated in details. A series of polymers with different bromine connected groups as poly (tert‐butyl acrylate) (PtBA‐Br), polystyrene (PS‐Br), and poly (methyl methacrylate) (PMMA‐Br) are prepared by atom transfer radical polymerization first, then the bromine‐containing polymers were coupled with 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy‐containing poly(ε‐caprolactone) (PCL‐TEMPO) in different catalyst systems as CuBr/PMDETA, Cu⁰/PMDETA and CuBr/Cu⁰/PMDETA in the temperature range from 90 °C to 25 °C. The result shows that the catalyst system of CuBr/Cu⁰/PMDETA is the best one for NRC reaction, in which the NRC reaction could be conducted in high efficiency in the wide temperature range from room temperature to high temperature. The efficiency of NRC reaction between PtBA‐Br and PCL‐TEMPO is more than 85% in the temperature range from 25 to 75 °C, the efficiency between PS‐Br and PCL‐TEMPO is more than 90% from 25 to 90 °C, and the efficiency between PMMA‐Br and PCL‐TEMPO is more than 90% only at the room temperature. The effect of bromine connected groups on the NRC reaction is discussed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2991–2999, 2010     

Calibration of alkyl-substituted fluorocyclopropanes on gas chromatographic columns by radioactive tracer techniques

A new method utilizing a radio-gas chromatographic system, for the calibration of various gas chromatographic columns with less than 10⁻¹²M of tritium-labelled samples is described. The minimum detectable level of³H,³⁸Cl,¹⁸F,^80mBr,⁸²Br,³⁵S and¹⁴C labelled compounds employed for column calibration is discussed. In addition, the relative retention times of nine previously unpublished alkyl-substituted fluorocyclopropanes on five gas chromatographic columns are given.     

The applicability of radiotracers for the investigation of the distillation of hydrocarbons

The use of radioactive tracers provide valuable methods for the investigation of distillation processes and have been applied to determine the characteristics of material streams, the dynamics of flowing phases and the compositions in various parts of the distillation equipment. A method is proposed for testing individual radiotracers employed for the investigation of the distillation of hydrocarbons. The method consists in laboratory-scale distillation of a tracer together with a multicomponent hydrocarbon mixture, namely a gasoline fraction. The purification efficiency, distillation characteristics, and effective radiochemical purity of several tracers (reactor activated bromobenzene and synthesized C₃H₇ ⁸²Br, C₄H₉ ⁸²Br, C₅H₁₁ ⁸²Br) have been investigated. The distillation characteristics of bromohydrocarbons labelled with⁸²Br and selected hydrocarbons tagged with¹⁴C (benzene and cumene) have been compared. The radiotracers investigated were employed for the determination of the hydrodynamic parameters of hydrocarbon distillation in laboratory packed columns and a commercial distillation tower.     

Chemical characterization of short-lived selenium and their daughter isotopes from thermal neutron induced fission of 235U at a gas-jet facility

Selenium nuclides are available from thermal neutron induced nuclear fission of ²³⁵U at the gas-jet facility at the Swiss spallation neutron source (SINQ) at Paul Scherrer Institute, Switzerland. The formation of stable selenium compounds, their transport yields using the gas-jet system and their relative thermal decomposition temperature were investigated under oxidizing and reducing conditions in the target chamber. Using O₂, H₂, CO, and propene as additional gases, the selenium isotopes are suggested to form H₂SeO₃, H₂Se, COSe, and C₃H₆Se, respectively, with overall ⁸⁴Se yields of 1.5%, 4.7%, 6.3%, and 21.9%, respectively. Adsorption enthalpy, vapour pressure, solubility and acidity data for these species were collected from the literature or estimated from other known thermochemical properties. Carrier free bromine isotopes (⁸⁴Br, ⁸⁶Br) in the form of HOBr were obtained by thermally decomposing H₂SeO₃ and retaining elemental Se under oxygen rich conditions on quartz at 400 K.     

Cluster mechanism of the atmosphere ozone destruction by bromine ions

Interaction of bromine ions absorbed by water cluster with adsorbed oxygen and ozone molecules has been investigated by the molecular dynamics method. It was shown that the part of O₂ molecules was removed from the system by evaporating Br⁻ ions, while all O₃ molecules and Br ions were kept in the system during 25 ps. The increase the concentration of the Br⁻ ions in the clusters resulted in a reduction of the absorption intensity and emission in IR spectra at the presence of oxygen, whereas the absorption intensity in the appropriate IR spectra of ozone-containing systems increased with the growth of a number of the Br⁻ ions. Raman spectra of oxygen-containing systems were poorly sensitive to the concentration of the Br⁻ ions but the absorption intensity of Raman spectra for systems with ozone considerably decreased with the growth of a number of bromine ions.     

Resonance activation analysis of iodine

Resonance neutron activation and gamma-ray spectrometry were used to determine traces of iodine in biological materials. The method developed is purely instrumental and fairly rapid. The major interfering activities of²⁴Na,³⁸Cl,³⁶Mn and⁸²Br were significantly reduced by irradiating the samples inside a shield of Cd, NaCl, MnBr₂ and MnO₂. Neutrons with energies close to the resonances of Na, Cl, Mn and Br were absorbed in the shield and did not activate the sample while neutrons with energies close to the resonances of iodine were not absorbed appreciably. Thus the activity of¹²⁸I was enhanced relative to the interfering activities. The 442 keV gamma of¹²⁸I (T=25 min) was measured using a high-resolution Ge(Li) detector and a multichannel analyzer. Sensitivity of 0.05 ppm was obtained.     

Feasibility of ultra-trace determination of bromine and iodine in honey by ICP-MS using high sample mass in microwave-induced combustion

This work demonstrates the feasibility of ultra-trace determination of halogens in biological samples by inductively coupled plasma mass spectrometry (ICP-MS) after decomposition by microwave-induced combustion (MIC). The conventional MIC method was improved to allow the combustion of samples with mass higher than that used in previous works in order to achieve better limits of detection (LODs). The applicability of the proposed method for ultra-trace determination of bromine and iodine in organic samples was demonstrated here using honey. It was possible to decompose up to 1000 mg of honey using microcrystalline cellulose as a combustion aid and polyethylene film for sample wrapping. After combustion, analytes were absorbed using 50 mmol L^?1 NH₄OH and recoveries for Br and I were between 99 and 104 %, and relative standard deviations were lower than 5 %. Microwave-assisted alkaline dissolution (MA-AD) was also evaluated for honey sample preparation using NH₄OH or tetramethylammonium hydroxide solutions. However, the LODs for the MA-AD method were unsuitable because the high carbon content in digests required a dilution step prior to the analysis by ICP-MS. The LODs obtained by MIC were improved from 1143 to 34 ng g^?1 for Br and from 571 to 6.0 ng g^?1 for I, when compared to the MA-AD method. Furthermore, it was possible to decompose up to eight samples simultaneously in 30 min (including the cooling step) with very low reagent consumption and consequently lower generation of effluents, making MIC method well suited for routine ultra-trace determination of Br and I in honey.

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Graphical Abstract A high mass of honey was efficiently digested by MIC for subsequent Br and I determination by ICP-MS

     

Cyclotron isotopes and radiopharmaceuticals XXVI. A carrier-free separation of77Br from se

A silver chloride co-precipitation and ion exchange separation method is described for the carrier-free isolation of⁷⁷Br bromide from isotopically enriched⁷⁷Se targets following dissolution of the irradiated⁷⁷Se in nitric acid. A cation exchange procedure has been devised to remove the silver and yield a dilute hydrochloric acid solution containing ≈90% of the precipitated⁷⁷Br as bromide. The radiochemical and chemical composition of several preparations have been analyzed. A method for the quantitative recovery of the isotopically enriched selenium is described. Research carried out under contract with the U.S. Department of Energy and supported by its Division of Basic Energy Sciences. Supported in part by the Massachusetts Heart Association and by NIH Grant No. HL 18487-01. All inquiries should be directed to R. M. Lambrecht. For earlier papers in this series see Ref.¹²     

Neutron activation analysis correction for the calculation of bromine concentrations via the79Br(n, γ)80Br reaction

Bromine can be determined by neutron activation analysis (NNA) through either the activation of⁷⁹Br (50.69% naturally abundant) or⁸¹Br (49.31% naturally abundant). When⁷⁹Br is activated, both^80mBr and⁸⁰Br are produced.^80mBr (4.42 h) decays to⁸⁰Br (17.66 m) which then beta decays to either⁸⁰Se or⁸⁰Kr. If one would like to determine bromine concentrations with short lived NAA, special equations must be used to account for the parent daughter relationship between^80mBr after their simultaneous production. The development of the equations needed to calculate bromine concentrations with short-lived NAA is described including variations on irradiation times, decay times, and count times.     

Neutron activation analysis of iodine in blood serum or other biological materials by substoichiometric precipitation of iodine as silver iodide

Several modifications are proposed of the established methods of iodine determination in serum. Prior to the actual analysis, the serum is lyophilized. This preliminary treatment permits the use of large samples. Through lyophilization human blood serum samples can easily be reduced to one-tenth of the original weight. Reduction is even more dramatic with materials from other than human origin. After irradiation the samples are subjected to chemical treatment in the presence of an iodine carrier and¹³¹I-labelled thyoxine. This procedure has been adopted for the determination of the iodine content and the chemical yield in one and the same radioactive measurement. The analysis technique itself consists of an open system Schöniger combustion. The open combustion allows the use of large samples; the gases evolved are absorbed upon their subsequent passage through potassium hydroxide and hydrochloric acid; the mineralization requires less than two minutes. After the addition of a substochiometric amount of silver nitrate, silver iodide is precipitated from an ammoniacal solution as a flat sample, which has been found ideally suited for high efficiency counting with a Ge(Li) detector. The spectrum gives evidence of an excellent decontamination from the³⁸Cl,⁸⁰Br and⁸²Br activities. The iodine content can be calculated from the ratio of the photopeak areas at 364.5 keV and 442.7 keV corresponding to¹³¹I and¹²⁸I, respectively. The chemical procedure requires a mere 15 min, and the recording of the γ-ray spectrum takes no longer than 30 min. The technique is not limited to serum only. It proved well suited for the analysis of many other types of biological material, e.g. human skin tissues.     

Determination of selenium in biological tissue samples rich in phosphorus using electrothermal atomization with Zeeman-effect background correction and (NH4)3RhCl6+citric acid as a mixed chemical modifier

Spectral interferences from phosphorus on the determination of selenium in biological tissue materials were not observed when a Zeeman-effect background correction was used with rhodium as a chemical modifier. A suppression effect on the selenium signal resulted when the concentration of phosphorus present was greater than 1.0 mg ml⁻¹. Rhodium was found to be more effective than palladium in overcoming the phosphate interference. Analytical procedures for the direct determination of trace selenium in standard reference materials by graphite furnace atomic absorption spectrometry following sample dissolution in nitric acid and hydrogen peroxide using a microwave oven has been described. The results obtained agreed favourably with the certified values.     

Determination of molybdenum in hair and wool by neutron activation analysis

Neutron activation analysis was applied to the determination of molybdenum in hair and wool. Ashed samples of hair and wool were irradiated for 15 min at a flux of 5·10¹³ n/cm²/sec to produce ¹⁰¹Mo. An acid solution of the ash was first boiled in the presence of sodium bromide and bromate to volatilize bromine (⁸⁰Br and ⁸²Br radioisotopes interfere) and then extracted with 0.1% α-benzoinoxime in chloroform to remove ¹⁰¹Mo from other interfering radionuclides. The ¹⁰¹Tc daughter from ¹⁰¹Mo was measured over the 0.31-MeV γ-ray photopeak after allowing the separated ¹⁰¹Mo to decay for 15 min. The molybdenum concentration in hair varied from 0.02 to 0.13μg/g while wool was found to contain 0.04–0.58 μg/g.     

A novel and facile one‐pot synthesis of pyridylselenium compounds through selective bromine–magnesium exchange with isopropylmagnesium halide

One‐pot synthesis of various unsymmetrical 2‐bromo‐5‐pyridylselenium compounds has been carried out under non‐cryogenic conditions by selective single bromine–magnesium exchange of 2,5‐dibromopyridine using isopropylmagnesium chloride. This exchange gives 2‐bromo‐5‐pyridylmagnesium chloride, which upon the insertion of elemental selenium followed by the treatment with alkyl halide gives the title compounds in good yield. This exchange has also been extended towards bromine–magnesium exchange of 2‐bromopyridine for the improved synthesis of 2‐pyridylselenium compounds. The molecular structure of 2‐bromo‐5‐selenopyridyltribromomethane has been examined by single crystal X‐ray diffraction. This compound crystallizes in the monoclinic space group P2₁/n. From the molecular structure it was found that intermolecular BrBr, NSe and SeBr interactions control its crystal packing. Copyright © 2005 John Wiley & Sons, Ltd.     

Mikro-Brombestimmung in Halbleiterselen

Zusammenfassung Für die Beurteilung von Leitfähigkeitsmessungen an Halbleiterselen ist besonders die Kenntnis des Halogengehaltes der Selenproben von Wichtigkeit. Es werden zwei Verfahren zur Mikrobestimmung des Broms in reinem Selen beschrieben, die sich zur Bestimmung eines Halogengehaltes von 0,1–0,2% bzw. von 10^–3% eignen. Diese Verfahren können besonders zur Betriebsanalyse in Halbleiter- bzw. Gleichrichterwerken angewandt werden.

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Summary In the examination of selenium samples for semi-conductors the halide content is an important criterion for the estimation of electric conductivity. For the micro-determination of bromine in pure selenium two methods are described suitable for the range of halide content from 0.1 to 0.20% and 10^–3%, respectively. These methods are especially applicable to analysis in plants of the semi-conductor and rectifier production.

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Herrn Prof. Dr. C. F. Weiss danken wir für die Unterstützung bei der Durchführung der Arbeit.     

The heterogeneous interaction of Br(2P3/2) and Br(2P1/2) with surfaces of Teflon™ and polycrystalline nickel

Pulses of Br(²P_3/2) and Br(²P_1/2) (=Brast;) have been exposed to Teflon (PTFE) and to polycrystalline Ni surfaces in a Knudsen cell. The Br and Br* atom densities have been measured as a function of time using [3 + 2] Resonance Enhanced Multiphoton Ionization (REMPI) at 461.9 and 459.1 nm, respectively, and an absolute calibration of the sum of the density of Br and Br* on Teflon at ambient temperature has been measured to result in identical values within experimental error for both Br and Br*, namely γ(Br) = (5.6 ± 1.5) · 10^?5, if an appropriate correction for the radiative lifetime of Br* of 0.77 s^?1 is applied. The uptake coefficients for Br and Br* on polycrystalline Ni seem to be identical: γ(Br) = γ(Br*) = (5.6 ± 1.8) · 10^?3 and independent of temperature in the range 295 to 500 K. A possible exception is the value for γ(Br*) of 2.3 · 10^?3 at T = 295 K which seems to be significantly lower than the remainder of the uptake data. In the temperature range 500 to 700 K the uptake coefficients for both Br and Br* can be expressed as . The system has a small positive activation energy in the range 3.3 to 4.5 kcal/mol. Br* seems to be less reactive than Cl* with respect to surface deactivation on poly Ni by a factor of six. In analogy to Cl the present system is characterized by kinetic complications in conjunction with the reversible surface poisoning of bromine, both atomic and molecular, on surfaces of Teflon (PTFE) and poly Ni that leads to the decrease of Br and Br* uptake with increasing exposure. © 1995 John Wiley & Sons, Inc.