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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 %.

We present our findings on the use of diode laser spectroscopy (DLS) for monitoring СО2, Н2О, СН4, C2H2, C2H4, NH3, and other gas impurities during low-temperature fractional distillation purification of gaseous hydrides. We demonstrate a lineup of instruments and techniques for continuously monitoring impurities during purification of hydrides: NH3, AsH3, РН3, and SiH4. The IR sources used are distributed feedback diode lasers (DLs) having a single mode output fiber pigtail and covering the near-IR spectral region, from 0.7 to 2.0 μm, where overtone and combination absorption bands of the impurities of interest are located. The systems offer high sensitivity and speed in impurity concentration measurements. Owing to their small size and low energy consumption, they can readily be integrated into a process equipment (components of fractionation columns) and enable prolonged continuous monitoring of the purity of hydrides. We describe gas concentration measurement techniques that use conventional high-resolution differential absorption spectroscopy and new, modulation correlation approaches for monitoring a weak molecular absorption by an impurity of interest against a strong selective absorption background of a matrix substance (hydride under study). We present results of technological experiments concerned with the low-temperature fractional distillation of hydrides and the degree of impurity removal from them as monitored by DLS.

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 %

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.

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.

A method of chromato-mass spectrometry is used to study the impurity composition of 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 C 1 – C 3 , 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 homologues of monosilane, siloxanes, and alkylsilanes we used a column 25 m × 0.26 mm, d f = 0.25 μm with a polytrimethylsilylpropyne (PTMSP) sorbent. Identification of the impurities was performed 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 a low coincidence of the spectra identification was performed using data of mass spectra and retention time published in the literature. The impurities of permanent gases, carbon dioxide, hydrocarbons C 1 – C 3 , volatile inorganic hydrides, monosilane homologues, siloxanes, and alkylsilanes were identified in monosilane. Quantitative determination of the impurities was carried out in the mode of selective ion detection by the mass numbers having the maximum signal/noise ratio. Calculation of their concentrations was performed using a method of absolute calibration by the peak areas. The concentrations of the impurities in the lack of reference samples 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 confirmed by the method of sample size variation. The results of determination of the impurities in monosilane after synthesis, in that purified by low temperature rectification, and in the isolated fractions with concentrated higher- and lower-boiling impurities.

A pneumovacuum circuit of a Tsvet-800-2 gas chromatograph with a helium ionization detector (HID) in the ionization amplification mode is proposed for controlling limiting trace impurities in ammonia, arsine, monosilane, and phosphine of grade 6N4. The conditions for the preparation and reliable operation of the chromatograph with the HID are systematized. The effect of an additive of (0.0–17.6) × 10–4 mol % of hydrogen in the carrier gas of the detector on the polarity of its signal on the impurities of oxygen and nitrogen at a level of (0.5–20.0) × 10–5 mol % is studied. Methods are proposed for eliminating systematic errors in the determination of the concentration of oxygen and nitrogen in the range from 0.5 × 10–5 to 1 × 10–3 mol % in 6N4 volatile hydrides, caused by “counter” impurities in the carrier gas, the mechanism of the heteropolar sensitivity of the HID, and irreversible chemical reactions of oxygen traces with phosphine and products of its decomposition on a CaA–ShM zeolite in a separating column of a chromatograph. Gas chromatography analysis of ammonia, arsine, monosilane, and phosphine of grade 6N4 was carried out.