Nondestructive and destructive determination of manganese in nickel- and iron-base alloys by neutron activation analysis

Nondestructive and destructive methods are described for the determination, by neutron activation, of small amounts (more than about 0.001%) of manganese in nickel- and iron-base alloys. In the destructive method, thenoyltrifluoroacetone (TTA) extraction has been applied to the separation of manganese after irradiation.     

Determination of boron in copper and copper-, nickel- and cobalt-base alloys

Summary A pyrohydrolytic method for the extraction of boron from coppper and copper-, nickel- and cobalt-base alloys has been developed. For concentrations higher than 0.1 %, boron is determined by an alkalimetric method in the presence of mannitol and phenolphthalein or by a potentiometric method. For samples containing less than 0.1% of boron, it is determined by spectrophotometry with azomethine H. Standard deviations are in the range of 0.008 to 0.15% B.

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Bestimmung von Bor in Kupfer sowie Legierungen auf Kupfer-, Nickel- und Kobaltbasis

Zusammenfassung Zur Extraktion von Bor aus diesen Proben wurde ein pyrohydrolytisches Verfahren ausgearbeitet. Die Borbestimmung erfolgt bei Gehalten >0,1% B alkalimetrisch in Gegenwart von Mannit und Phenolphthalein oder potentiometrisch, bei Gehalten <0,1% B durch Spektralphotometrie mit Azomethin H. Die Standardabweichungen liegen im Bereich von 0,008–0,15% B.

     

Comparison of chemical modifiers for selenium determination in soil aqua regia extracts by ZETAAS

The effect of various chemical modifiers 0.5 g l⁻¹ Pd, 1% (w/v) Ni, 0.5 g l⁻¹ Pd + 1% (w/v) Ni and 1.0 g l⁻¹ Pd on the measurement of selenium in soil aqua regia extracts, by ZETAAS, is described. Two Certified Reference Materials (CRMs) RTC-CRM 023-050 and RTC-CRM 025-050 were used for this study. Pyrolysis and atomization curves were obtained for each chemical modifier and their optimal values were assessed. By using standard addition as calibration method, accurate results were obtained for all the chemical modifiers studied. The precision was similar for both CRMs, with a maximum value of 7.5% R.S.D. The limits of detection and quantification for selenium in the soil extracts (n = 10) were 3.0 and 6.0 μg l⁻¹, respectively. The characteristic mass of selenium is assessed as 10 pg. The use of aqua regia as extractant gave quantitative results for selenium in the CRMs assayed.     

Spectrochemical determination of trace bismuth and lead in iron-base and high-temperature superalloys

A method is presented for determination of lead and bismuth in steels and superalloys, based on co-precipitation with manganese dioxide followed by optical-emission or atomic-absorption measurements. The limit of determination is about 0.0001% and the relative standard deviation is 4% at the 0.002% level.     

Gas-chromatographic determination of selenium

Selenium(IV) is reacted with 2,3-diaminonaphthalene at pH 2 to form the well established complex, which is extracted into hexane. An aliquot of the hexane layer is analyzed gas chromatographically with an electron-capture detector. As little as 510^?10 g of selenium could be detected; 0.01μg of selenium could be determined in a sample by extracting int 0.1 ml of hexane and injecting a 5-μl aliquot of the extract. The method was applied to the determination of physiological amounts of selenium in human blood and urine. Averages of 0.38 p.p.m. and 0.007 p.p.m. selenium were found in blood and urine. respectively. River water samples were also analyzed. Complete analysis time for a single sample is less than 3 h. including time for digestion of the sample and 2 h for formation of the complex.     

Microtrace determination in high-purity selenium

Summary A simple and rapid method is developed for the determination of traces of As, Sb and Sn in selenium of semiconductor grade purity. The limit of detection is 0.05 ppm, the relative standard deviation betwen 3 and 9%. The procedure may be applied to the determination of all trace elements which remain in solution during the reduction of selenium with hydrazine hydrate (As, Sb, Sn, Co, Cd, Mn, etc.).

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Mikrospurenbestimmung in hochreinem SelenIII. Elektrothermische AAS-Bestimmung von As, Sb und Sn nach Abtrennung der Matrix mit Hydrazin

     

化学蒸气发生-四通道原子荧光光谱法同时测定水样中的痕量砷、锑、硒和汞

应用自行设计的化学蒸气发生-四通道无色散原子荧光光谱仪,建立了同时测定水样中As、Sb、Se、Hg的新方法.在实验中优化了四元素同时化学蒸气发生条件和测定的最佳工作参数.在样品预处理阶段用HCl将Se6+还原为Se4+,然后用质量浓度5 g/L硫脲将As5+和Sb5+还原为As3+和Sb3+.在最佳条件下,方法对As、Sb、Se、Hg的检出限分别为0.05、0.03、0.05、0.01 ng/mL(3d);RSD分别为0.42%、0.74%、0.97%、1.0%(对5 ng/mL As、Sb、Se和0.5ng/mL Hg混合标准,n=7).用所建立的方法对不同类型水样中的As、Sb、Se、Hg进行了同时测定,测定结果与用标准方法测定所得结果之间无明显差异,各元素的加标回收率在93%～105%.     

Microtrace determination in high-purity selenium

Summary A method is developed for the determination of traces of Bi, Cd, Co, Cu, Fe, Mn, Pb, Te and Zn in selenium of approx. 99.99% purity. The traces are preconcentrated as chelate complexes on activated charcoal and are desorbed without destruction of the charcoal pores via competitive complexation with diethylenetriaminepentaacetic acid. The concentrate is analyzed by flame AAS-pulse aspiration. For increasing the sensitivity of the determination of Bi, Pb and Te a slotted quartz tube atom trap is attached to the burner. The atomization in the flame of metal chelates adsorbed on activated charcoal is discussed.

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Mikrospurenbestimmung in hochreinem SelenI. Anreicherung der Spuren auf Aktivkohle mit nachfolgender Flammen-AAS-Bestimmung

Zusammenfassung Ein Verfahren wurde entwickelt zur Bestimmung von Spuren Bi, Cd, Co, Cu, Fe, Mn, Pb, Te und Zn in Selen vom Reinheitsgrad 99,99%. Die Elementspuren werden als Chelatkomplexe auf Aktivkohle angereichert mit nachfolgender Desorption durch Konkurrenz-Komplexbildung mit Diethylenetriamin-pentaessigsäure. Das Konzentrat wird durch Flammen-AAS (Pulstechnik) analysiert. Die Empfindlichkeit der Bestimmung von Bi, Te und Pb wird mit Hilfe einer auf dem Brenner montierten doppelt geschlitzten Quarzröhre erhöht. Die Atomisierung von auf Aktivkohle adsorbierten Metallchelaten in der Flamme wird diskutiert.

     

The determination of selenium in urine

The selenium excreted in urine can be measured to assess the dietary status of selenium, an essential trace element in human nutrition. The objectives of this work were: 1) to develop a procedure, capable of high sample throughout, by which the major interferences can be reduced such that selenium concentrations can be measured in urine by Neutron Activation Analysis (NAA) using^77mSe (17.4 s; and 2) to apply the method to a human dietary selenium study in which several selenium monitors were compared. The method involves a pre-irradiation arsenic-coprecipitation separation of the selenium from urine in the presence of a high specific-activity⁷⁵Se tracer. The processed urine samples are analyzed using NAA. The procedure was applied to 58 urine specimens longitudinally collected from 12 subjects consuming three different levels of selenium. A dose-response relationship was observed in urine as well as a high correlations with both serum and whole blood selenium concentrations.     

Uncertainty estimation in chemical measurements: carbon dioxide determination at atmospheric concentration

The present work deals with the evaluation of measurement uncertainty in the determination of carbon dioxide (CO2) concentration in atmosphere, given the high relevance of this greenhouse gas that influences earth climate. In order to carry out CO2 measurements, non dispersive infrared (NDIR) analysers are usually employed as they are stable and scarcely affected by interferences from other air components or pollutants. Typical uncertainty sources are the resolution of the analyser, its time drift and the contributions due to instrument calibration, which is required in order to produce traceable measurement results. The calibration uncertainty takes into account the uncertainty of the composition of the calibration gas mixtures, the instrument repeatability and the possible or residual lack of fit of the adopted mathematical model.     

81mSe tracer for determination of the chemical yield in radiochemical neutron activation analysis of selenium

A radiotracer method is described for measurement of the chemical yield in radiochemical neutron activation analysis of selenium using the⁷⁵Se (120 d) induced nuclide. It is based on^81mSe (57 min) radioisotopic tracer, prepared immediately before its use in the radiochemical separation procedure, by neutron irradiation of highly enriched⁸⁰Se. The recovery of selenium is calculated from the 103 keV -peak of^81mSe in the separated selenium fraction used for quantitation of⁷⁵Se. The technique is illustrated by results for biological reference materials of good accuracy and reproducibility.     

紫外分光光度法测定硒氧化过程中二氧化硒

利用5-硝基-2,1,3-苯并苤硒脑对紫外光的吸收特性,用紫外分光光度计测定硒氧化过程中硒(Ⅳ)含量。研究了硒(Ⅳ)与4-硝基邻苯二胺(NPDA)生成5-硝基-2,1,3-苯并苤硒脑的衍生反应条件,验证了测定结果的准确性。结果表明:衍生反应适宜条件为pH2,反应温度60℃,反应时间10 min,NPDA试剂用量为硒(Ⅳ)的168倍。在0.002~0.02 g/L硒(Ⅳ)范围内,硒(Ⅳ)浓度与衍生产物5-硝基-2,1,3-苯并苤硒脑的吸光度线性关系良好。用该法测定硒氧化过程中二氧化硒含量,RSD为0.52%。硒(Ⅳ)的平均加标回收率为98.12%。本文建立的紫外分光光度法为硒含量较大的体系中硒(Ⅳ)定量分析提供了准确、便捷的测定方法,对于其它价态硒(Ⅵ价、Ⅱ价、0价)测定有借鉴作用。     

Thermodynamic properties of iron—selenium alloys

Selenium vapor pressures of iron-selenium alloys were determined by an isopiestic method between 700 and 1 200 K and 50 to 60 at%Se, and activities and partial molar enthalpies of selenium were calculated. ByGibbs-Duhem integration activities of iron, and integralGibbs energies were obtained. A theoretical model was successfully applied to interprete the thermodynamic properties of the hexagonal -phase with NiAs-structure. Assuming a random distribution of iron vacancies in every transition metal layer of the lattice excellent agreement with experimental data was found. The energy of interaction betwen iron vacancies was calculated to be 147.0 kJ/g-atom.

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Thermodynamische Eigenschaften von Eisen—Selen—Legierungen

Zusammenfassung Die Selendampfdrücke von Eisen-Selen-Legierungen wurden mit Hilfe einer isopiestischen Methode zwischen 700 und 1 200 K und zwischen 50 und 60 At%Se bestimmt. Daraus wurden die Aktivitäten und die partiellen molaren Enthalpien von Selen berechnet, und über eineGibbs-Duhem-Integration wurden die Eisen-Aktivitäten und die integralenGibbs'schen Energien erhalten. Ein theoretisches Modell wurde erfolgreich angewendet, um die thermodynamischen Eigenschaften in der hexagonalen NiAs-Phase zu interpretieren. Unter der Annahme einer statistischen Verteilung von Eisen-Leerstellen über sämtliche Übergangsmetall-Schichten wurde eine ausgezeichnete Übereinstimmung mit den experimentell gefundenen Daten festgestellt. Die Wechsel-wirkungsenergie zwischen diesen Leerstellen wurde zu 147,0 kJ/g-atom ermittelt.

     

Thermodynamic properties of nickel—selenium alloys

Vapor pressures of selenium in nickel—selenium alloys were determined by an isopiestic method between 450° and 1000°C and between 45 and 66.6 at% Se. Activities of selenium were evaluated according to three methods. For the NiAs-type Ni_1?x Se phase a statistical model was applied assuming random distribution of metal atoms and metal vacancies in the partially vacant (00 1/2) layers of the lattice. Good agreement between experimental and theoretical values was obtained. The interaction energy between nickel vacancies was found to be 8600 cal/g-atom.     

Simultaneous determination of arsenic, selenium and mercury in foodstuffs by chemical vapour generation inductively coupled plasma optical emission spectroscopy

A procedure for the simultaneous determination of arsenic, selenium and mercury in foodstuffs has been developed. After a two-step microwave-assisted wet digestion in closed vessels, using concentrated nitric acid and hydrogen peroxide, the solution was analysed by inductively coupled plasma multichannel-based emission spectrometry using chemical vapour generation as the sample introduction system. All steps of the procedure, such as solid sample dissolution, pre-reduction to the suitable oxidation state, vapor generation, transport and atomization have been designed and optimised taking into account the concomitant presence of all the analytes considered. Temporal variation of analytical signals as well as interfering effects due to transition elements were also studied. Under the optimised operating conditions, the achieved detection limits for the simultaneous determination of arsenic, selenium and mercury in foodstuffs were 0.006, 0.023 and 0.018 microg g(-1), respectively, allowing their determination in real samples. Precision of the analytical procedure was 6.8% for arsenic, 5.2% for selenium and 7.7% for mercury (n=7). The accuracy and reliability of the method was verified by the analysis of both standard reference materials (rice flour and spinach leaves) and real samples (natural and Se-enriched rice).     

Quantitative HPTLC determination of selenium

The present determination of selenium in biological matrices by HPTLC with in situ fluorimetric detection is an accurate alternative method, comparable to other established methods such as photometry, polarography, neutron activation, or X-ray fluorescence analysis, gas chromatography, and atomic absorption spectrometry. The excellent sensitivity of this procedure is proved by the detection limit of 250 fg of selenium per spot (using purified 2,3,1-naphthoselenodiazole). The oxidation of organic matrices, applying a novel digestion procedure, may be carried out with little instrumental expenditure. Sample preparation steps, such as the oxidation of selenium to Se (VI) and subsequent reduction to Se (IV) do not lead to significant random or systematic errors, nor does the digestion step, if an optimized procedure is used. A recovery rate of 103% and nearly parallel calibration curves for digested selenocysteine standards compared with spiked human serum samples demonstrate the accurate quantitative preparation of a biological matrix. Any interfering metal ions can be masked by addition of chelate-forming reagents.     

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.     

Species determination of selenium in natural waters

A method is described for the determination in natural waters of selenite, selenate, dimethyl selenide, and dimethyl diselenide. The detection limits are in the parts per trillion range. The volatile methyl species are removed from the sample with a stripping gas. The inorganic forms are selectively reduced to the hydride, and also stripped from the sample. A liquid nitrogen trap is used to collect both the selenides and the generated hydrides. Separation of the methyl species is accomplished by gas chromatography. All the species are detected by an atomic absorption spectrometer equipped with a quartz tube furnace.     

Titrimetric determination of selenium in anodic slimes

The determination of selenium in the presence of tellurium and copper has been studied, to allow analysis of anodic slimes from electrolytic copper refining. Three methods have been developed for the determination of selenium in these slimes. They are based on the extraction of selenium with sodium sulphite, reduction of selenite with sodium sulphite, and separation of selenium and tellurium by adjustment of pH. Selenium (10(-3)-10(-2)M) is determined in the presence of tellurium, copper, iron, silver and lead. The methods are fast and simple, do not need expensive reagents, and give satisfactory results.