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The impurity composition of arsine is studied by gas chromatography–mass-spectrometry. Impu-rities of permanent gases; carbon dioxide; hydrides; saturated, unsaturated, and aromatic hydrocarbons C1–C6; halogenated hydrocarbons; sulfur compounds; and arsine and diarsine alkyl derivatives are determined. The impurity level of high-purity arsine is 10–6–10–5 vol %. Impurity concentrations in arsine after synthesis and in the fractions extracted in the course of its rectification are rather high and lie in the range 10–6–0.1 vol %. The limits of detection for impurities are 2 × 10–7–2 × 10–4 vol %. [ABSTRACT FROM AUTHOR]

The procedure for gas-chromatographic determination of hydrocarbons and sulfur tetrafluoride in germanium tetrafluoride of natural and isotopically enriched composition was characterized. For improving the efficiency of the chromatographic determination of impurities, it was proposed that the major compound be removed from the test sample with the subsequent cryofocusing of impurity hydrocarbons. The detection limits of C1–C4 and sulfur hexafluoride content were achieved with a plasma ionization detector and electron-capture detector, respectively. They amounted to (2–6) × 106 vol % and 8 × 106 vol %, respectively. The sensitivity of the electron-capture detector is no less than 5 × 105 times higher toward SF6 than that toward hydrocarbons, while the plasma ionization detector is 104 times more sensitive toward hydrocarbons than toward SF6. [ABSTRACT FROM AUTHOR]

A method of chromatography–mass spectrometry is used to study the impurity composition of arsine synthesized by the reaction of arsenic chloride with sodium borohydride. Capillary adsorption columns with adsorbents modified silica and polytrimethylsilylpropine is used for the separation of impurities. Impurities are identified by comparing their mass spectra with the NIST database, published data, as well as by reconstructing their structures from fragment ions. Impurities of permanent gases; saturated and unsaturated hydrocarbons C1–C6; chlorinated, oxygenated, and aromatic hydrocarbons; volatile inorganic hydrides; and alkyl derivatives of arsine, trimethyl fluorosilane, carbon sulfur dioxide, and dimethyl sulfide are identified in arsine. Mass spectra of C2H3AsH2, CH3AsHC2H5, and C2H5As2H3 impurities are obtained for the first time. [ABSTRACT FROM AUTHOR]

This review is devoted to the consideration of prospects and directions for the development of methods and approaches to the analysis of high-purity industrial gases and volatile hydrides, chlorides, fluorides, and organoelement compounds with natural and isotopically enriched compositions. The currently known capabilities for the determination of impurities in them using mass spectrometry, IR spectroscopy, gas chromatography, and chromatography–mass spectrometry are analyzed. [ABSTRACT FROM AUTHOR]

The review is devoted to the capabilities of gas chromatography–mass spectrometry in the analysis of high-purity volatile hydrides of naturally occurring and isotopically enriched compositions. Problems related to experimental techniques, chromatographic separation, identification, and quantitative determination of impurities are discussed. The application of this method has significantly expanded data coverage on the nature, number, and limiting possibilities of the determination of impurities in volatile inorganic hydrides. The identified impurities are compounds of various classes. Among them are atmospheric gases; saturated, unsaturated, and aromatic C1–C9 hydrocarbons; chlorine- and fluorine-containing C1–C4 hydrocarbons; homologues and alkyl derivatives of hydrides; Si2–Si4 siloxanes; fluorosiloxanes; oxygen-containing hydrocarbons; sulfur-containing substances; and hydrides of other elements. Gas chromatography–mass spectrometry analysis made it possible to detect the presence of impurities in isotopically enriched silicon and germanium hydrides, which are their molecular isobars. The use of gas chromatography–mass spectrometry in the analysis of high-purity inorganic hydrides makes it possible to reach the detection limits of impurities of 10–8–10–5 mol %. [ABSTRACT FROM AUTHOR]

The impurity composition of natural and isotopically enriched silane obtained from magnesium silicide and silicon tetrafluoride is studied by gas chromatography–mass-spectrometry. The impurities characteristic of silane with natural and isotopically enriched composition are atmospheric gases; carbon dioxide; hydrides; saturated, unsaturated, and aromatic hydrocarbons; halogenated hydrocarbons; alkyl derivatives and silane homologues, siloxanes. The impurity content of high-purity silane does not exceed 10–7–10–5 mol % After synthesis, the concentrations of impurities in the silane and fractions isolated by its distillation purification lie in the range n × 10–6 − n × 10 mol % The limits of detection for impurities are 1 × 10–8–9 × 10–4 mol % [ABSTRACT FROM AUTHOR]

The method of chromatography–mass spectrometry is used to study the impurity composition in monosilane obtained in the reaction of magnesium silicide with ammonium chloride in liquid ammonia. To improve the reliability of the impurity identification, along with the study of pure monosilane samples, we analyzed monosilane fractions isolated upon purification by low temperature rectification. To separate the impurities of permanent gases, hydrocarbons C1–C3, volatile inorganic hydrides, disilane, and alkylsilanes, we used an adsorption capillary column GS-GasPro 60 m × 0.32 mm with a modified silica gel. To separate the homologs of monosilane, siloxanes, and alkylsilanes, we used a column 25 m × 0.26 mm, df = 0.25 μm with a polytrimethylsilylpropyne (PTMSP) sorbent. The impurities were identified by comparison of their experimental mass spectra with the NIST database. In the absence of the mass spectra of analytes in the NIST electronic database or in the case of their low coincidence with the database spectra, the identification was performed using mass spectra and retention times published in the literature. The impurities of permanent gases, carbon dioxide, hydrocarbons C1–C3, volatile inorganic hydrides, monosilane homologies, siloxanes, and alkyl silanes were identified in monosilane. Quantitative determination of the impurities was carried out in the mode of selective ion detection using the mass numbers for which the signal-to-noise ratio was maximal. Their concentrations were calculated using a method of absolute calibration by the peak areas; in the case where reference samples were absent, the concentrations were determined using the dependence of the sensitivity coefficients of their detection on the magnitude of the total ionization cross sections. The detection limits of the impurities range within 1 × 10–5–2 × 10–7 mol %. The accuracy of the analysis was verified by the method of sample size variation. The results of determination of the impurities in monosilane after synthesis, as well as in monosilane purified by low temperature rectification and in the isolated fractions with concentrated higher and lower boiling impurities, are reported. [ABSTRACT FROM AUTHOR]

Chromatography-mass-spectrometry was used to examine the stability of admixtures of C1−C7 hydrocarbons, fluorine and chlorinated derivatives of hydrocarbons, alkyl derivatives of silane, homologs of monosilane, and siloxanes in monosilane in its storage in molybdenum-glass ampules and stainless-steel cylinders. It was found that, in the case of storage in glass ampules, the concentration of ethylene and tetrafluoroethylene admixtures decreases and that of ethyl silane and disilane increases. When monosilane is stored in a stainless steel cylinder, the concentration of the acetylene admixture it contains changes. [ABSTRACT FROM AUTHOR]

This paper examines sources of carbon impurities in polycrystalline monoisotopic 28Si prepared by a hydride method. Analytical data on the concentrations of carbon-containing impurities in volatile silicon compounds (28SiH4 and 28SiH4), process gases (Ar and H2), and polycrystalline 28Si are used to identify the major sources of carbon in the polycrystalline 28Si prepared by the hydride method. These are the starting 28SiH4 and calcium hydride used in 28SiH4 conversion into 28SiH4. The rate of carbon intake into polycrystalline silicon from the apparatus material during the monosilane pyrolysis process does not exceed 9 × 1011 cm-2 h-1. Polycrystalline silicon has been precipitated from monosilane with different concentrations of hydrocarbon impurities. At hydrocarbon concentrations in the range 10-4 to 10-3 mol %, the carbon concentration in the monosilane correlates with that in the silicon obtained from it. High-purity monosilane has been used to prepare polycrystalline 28Si samples with concentrations of carbon impurities in the range (0.8-2.3) × 1015 cm-3. Based on calculations of the carbon impurity distribution along the length of a zone-refined ingot, we examine the effect of the initial carbon concentration in the starting polycrystal on the yield of single-crystal monoisotopic 28Si. Requirements are formulated for the carbon concentration in polycrystalline 28Si which ensure a high yield of single crystals with parameters suitable for metrological applications. [ABSTRACT FROM AUTHOR]

Using high-resolution Fourier-transform IR spectroscopy and gas chromatography, we have identified more than 20 impurity species, in concentrations from 10 to 10 vol %, in GeF samples of different isotopic compositions. The germanium tetrafluoride samples are shown to contain C-C hydrocarbons; hydrogen, carbon, silicon, and sulfur fluorides; fluorogermanes; fluorosilanes; and carbon and nitrogen oxides. [ABSTRACT FROM AUTHOR]

We have developed analytical techniques for the determination of impurities in isotopically enriched 28SiH4 and 28SiF4. The impurities in SiF4 were first determined by IR spectroscopy, and those in SiH4, by gas chromatography/mass spectrometry. High-sensitivity determination of organic impurities in SiH4 and SiF4 was performed by gas chromatography. SiF4 was found to contain C1–C4 hydrocarbons, hexafluorodisiloxane (Si2F6O), hydrogen fluoride, trifluorosilanol (SiF3OH), fluorosilanes, water, and carbon oxides. The impurities identified in SiH4 include C1–C4 hydrocarbons, disilane (Si2H6), inorganic hydrides, Si2H6O, alkylsilanes, and fluorinated and chlorinated organics. The detection limits of IR spectroscopy were 3 × 10−3 to 5 × 10−5 mol %, those of gas chromatography/mass spectrometry were 8 × 10−6 to 10−8 mol %, and those of gas chromatography were 6 × 10-6 to 2 × 10−7 mol %. [ABSTRACT FROM AUTHOR]