IDENTIFICATION OF IMPURITIES IN SPECIAL PURITY SELENIUM USING THE GAS CHROMATOGRAPHY-MASS SPECTROMETRY METHOD
The molecular composition of impurities in special purity selenium was studied for the first time using the gas chromatography-mass spectrometry method. The concentrate of impurities with boiling points below that of the selenium was obtained by its vacuum distillation. The impurities were condensed and frozen from the vapor phase beyond the zone of the complete condensation of selenium vapors. The analysis of the obtained samples was performed using an Agilent 6890 / 5973N gas chromatography-mass spectrometer with a quadrupole mass analyzer. The samples’ input into the analytical device was carried out using a vacuum system made of stainless steel tubes. For the separation of impurities, GS-GasPro 60 m × 0.32 mm capillary adsorption columns with a silica gel sorbent and a 25 m × 0.26 mm polytrimethylsilylpropine (PTMSP) sorbent were used to separate the substances with low and quite high boiling temperatures. Their combined use made it possible to determine a wider range of impurities in selenium. The impurities were identified by comparing the experimental mass spectra with the data from the NIST database. In the absence of mass spectra of the detected substances in this library, their identification was carried out by restoring the composition with the fragment ions. Thus, the mass spectrum of the COSe impurity, which was not found in the literature, was decoded and described. In selenium, impurities of constant gases, carbon dioxide, C2 - C6 hydrocarbons, aromatic hydrocarbons, carbonyl sulphide, some chlorinated hydrocarbons, cyan, selenium compounds, and ethers were identified.