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

     

The determination of selenium and other impurities in high-purity copper by flameless atomic-absorption spectrophotometry

Se, Te, Bi and Sb are co-precipitated with ferric hydroxide from a solution of 1 g of the copper. The precipitate is collected on a filter disc and punched samples are taken for flameless atomicabsorption analysis. Less than 0.5 ppm of the four elements can be rapidly determined.     

石墨炉原子吸收法测定高纯硒中痕量铁

研究了石墨炉原子吸收直接进样法和石墨炉内富集法测定高纯硒中痕量铁的条件,建立了石墨炉原子吸收法直接测定高纯硒中痕量铁的分析方法.直接进样法的检出限为0.008 μg/g,石墨炉内富集法的检出限为0.004 μg/g,相对标准偏差分别为:5.2%和4.6%,两种方法检测样品结果基本一致.测定含铁0.3 μg/g的高纯硒,测定值的RSD为4.6～5.2%.     

Spectrophotometric determination of selenium in concentrates and high-purity copper metal with 3,3'-diaminobenzidine after separation by xanthate extraction

A method for determining 0.0001-0.10% of selenium in copper, nickel, molybdenum, lead and zinc sulphide concentrates is described. After sample decomposition, selenium is reduced to the quadrivalent state by heating in a 4M hydrochloric acid-5M sulphuric acid medium, then extracted into chloroform as the xanthate, and ultimately determined spectrophotometrically with 3,3'-diaminobenzidine. Small amounts of iron, lead and copper, and an appreciable amount of molybdenum are co-extracted as xanthates but do not interfere. More than 5 mg of antimony will cause low results. The proposed method was developed primarily for concentrates, but it is also applicable to high-purity copper.     

Extraction-spectrophotometric determination of thallium in high-purity indium

Trace amounts of thallium in high-purity indium are separated from the matrix by extraction from 6M hydrochloric acid by di-isopropyl ether. On shaking the extract with Brilliant Green in 0.15M hydrochloric acid, an ion-association complex is formed in the organic phase. Interference of other elements is removed by their reduction with metallic copper and scrubbing. The proposed method permits determination of 10(-5)-10(-6)% thallium in high-purity indium with good precision and accuracy.     

Polarographic determination of impurities in high-purity phosphorus

Square-wave and radio-frequency polarographic techniques in phosphoric acid-potassium chloride media are applied to the simultaneous determination of copper, lead and cadmium in highpurity red phosphorus down to a level of 0.1 ppm. In addition ca. 0.01 ppm of cadmium is determined by R.F. polarography in potassium sulphate base electrolyte after cation-exchange separation.     

Gas-chromatographic determination of carbon-containing impurities in high-purity sulfur

A gas-chromatographic procedure was developed for the determination of carbon-containing impurities in sulfur with a detection limit of 6 x 10^-6%. Carbon-containing substances and elemental carbon can be effectively separated from sulfur samples as CO₂ and COS.     

Extraction-spectrometric determination of lead in high-purity aluminium salts

Trace amounts of lead were determined in high purity aluminium salts (especially in ammonium aluminium sulfate) using inductively coupled plasma-optical emission spectrometry (ICP-OES) after extractive pre-concentration and matrix separation. Metals were extracted from the aluminium matrix in the form of chelates with ammonium pyrolidine dithoocarbamate into methyl isobutyketone. The organic extract was digested with nitric acid and hydrogen peroxide. The limit of detection for the determination of lead in crystalline ammonium aluminium sulfate was ca. 0.044 mug g(-1). The relative expanded uncertainty of the lead determination was ca. 23% at the level of 0.2 mug g(-1) and ca. 16% at the level of 1.0 mug g(-1). The main uncertainty contribution was associated with repeatability of the whole analytical procedure.     

Gas chromatographic determination of benzothiophenes in high-purity sulfur

A procedure is developed for the determination of benzothiophene, dibenzothiophene, and 4,6-dimethyldibenzothiophene in high-purity sulfur, including liquid-phase microextraction preconcentration, identification by gas chromatography?mass spectrometry, and gas chromatographic determination with flame photometric detection. The rate of microextraction recovery was from 16 to 78%. The limits of detection were 8 × 10^–5 wt % for benzophiophene and 2 × 10^–5 wt % for dibenzothiophene and 4,6-dimethyldibenzothiophene.     

Spectrographic determination of the rare earths in high-purity graphite

A spectrographic method has been developed for determination of the rare-earth elements in graphite. The rare earths are concentrated from ignited graphite on a calcium base. The impurities (Fe, V, Mn, Al, Ti) associated with the rare earths are separated by precipitation of the rare earths as hydroxides in the presence of Fe as a carrier, followed by precipitation of the rare earths as oxalates in the presence of Ca carrier. The mixture of calcium and rare-earth oxides obtained after ignition of the corresponding oxalates is mixed with graphite in 1:1 ratio and excited in a 15-A d.c. arc, with Nd as internal standard. The concentration ranges of determination are as follows: 0.006-0.125 ppm for Eu, 0.006-0.25 ppm for Gd, 0.006-0.06 ppm for Dy, 0.06-0.5 ppm for Sm. This sensitivity is achieved with 35-g samples of graphite. Higher enrichment factors are needed in order to enhance the sensitivity of the method.     

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.     

Precise titrimetric determination of uranium in high-purity uranium compounds

A procedure has been developed for the very precise determination of uranium in high-purity uranium compounds. Uranium(VI) is reduced in a strong hydrochloric acid solution with aluminium in the presence of cadmium ions to uranium(III). It is oxidised to uranium(IV) in the presence of excess orthophosphoric acid and then quantitatively oxidised to uranium(VI) with potassium dichromate using a potentiometric end-point detection. The coefficient of variation based on 20 analyses is -/+ 0.003%.     

Interferences in the determination of trace elements in high-purity tin

Reactor neutron activation analysis of antimony, indium and cadmium in high-purity tin is interfered with by nuclear reactions on the tin matrix. For a number of interfering reactions the cross-sections were determined. The following results were obtained:¹²²Sn(n,γ)^123mSn:σ_th=0.145 barn, I=0.79 barn;¹²²Sn(n,γ)¹¹³Sn:σ_th=0.52, I=25.4 barn;¹¹²Sn(n, 2n)¹¹¹Sn: microbarn;¹¹⁸Sn(n, α)¹¹⁵Cd: microbarn; and¹¹⁴Sn(n, p)^114m1In: microbarn.     

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.     

阳离子交换富集/ICP-MS测定高纯硒中13种杂质

研究了阳离子交换富集预处理/ICP-MS法测定高纯硒中多种杂质,建立了高纯硒中Mg、Al、Ti等13种杂质的分析方法.测定下限达到0.02～0.2μg/g.测定高纯硒样品,相时标准偏差2.5％ ～22％;加标回收率为80％～110％.     

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。     

Separation and spectrophotometric determination of trace elements in high-purity cadmium

Zusammenfassung Die Spurenanalyse zur Bestimmung von Ag, Al, Bi, Co, Cu, Ga, Hg, In, Mn, Ni, Pb, Tl und Zn in reinstem Cadmium wurde ausgearbeitet. Nach dem vorgeschlagenen Schema werden einzelne Gruppen von Spurenelementen durch Extraktion bzw. Mitfällung getrennt und spektrophotometrisch mit Hilfe der folgenden organischen Reagenzien bestimmt: Dithizon, PAN, PAR, Rhodamin B, Brillantgrün, Chromazurol S, 1-Nitroso-2-naphthol und-Furildioxim. Durch die Analyse einer Cadmiumprobe mit dem Zusatz bekannter Mengen der zu bestimmenden Elemente wurden Genauigkeit und Präzision der vorgeschlagenen Methode erwiesen.     

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.