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Capillary chromatograph has found wide application for determining environmental pollutants. The success of this method in determining "genetic" impurities in gas-phase high-purity substances, such as inorganic hydrides, is much humbler. This is due to the limited number of adsorbents for the capillary chromatography of hydrides and the difficulties with the injection of large amounts of poorly adsorbed substances into a capillary column [1].It is known that the total dispersion of a chromatographic peak is given by the sum of dispersions at the steps of dosing, ; chromatographic separation, ; and detection, [2]:The injection of large samples into a capillary column results in the formation of a very broad total chromatographic band of the matrix and impurities, so that one cannot attain the low absolute detection limits for impurities typical of capillary chromatography.We have performed a study using capillary chromatography for analyzing high-purity silane. We used a 2D method, in which the major component was separated from the impurities in a packed column and the impurities after cryofocusing were separated in a capillary column. EXPERIMENTALThe study was conducted on the setup shown in Fig. 1; the setup was assembled on the basis of a Tsvet-500 chromatograph with a flame-ionization detector. Thesetup was equipped with an evacuated flow sample dosing system, a system for additionally purifying helium carrier gas, a packed forecolumn for separating silane, and a capillary column with a flow dividing valve for extracting impurity hydrocarbons from the sample and their cryofocusing.All drawn gas lines between the purification system and the separation column were made of molybdenum (borosilicate) glass. A fused-silica capillary column and splitters of the carrier gas flow were connected with metallic threaded joints sealed with silicone rubber and attached to glass tubes with an epoxy resin.Silane samples were injected through the evacuated system [3] with a calibrated volume of 8.2 cm 3 , which included oil-free valves made of molybdenum glass and fluoroplastic. The pressure in the injection system was controlled with mercury manometer 16 .Quality B helium (TU 51-940-80) used as the carrier gas was additionally purified of water and hydrocarbons. Water vapors were removed by filtering the carrier gas through Petryanov cloth at 77 K. The residual moisture content was no more than 1 × 10 -5 mol % [4]; it was periodically controlled by measuring dew-point temperature. The carrier gas was then passed through 1 m × 4 mm coiled column 4 made of molybdenum glass; the column was filled with SKT activated charcoal 0.25-0.5 mm mesh and cooled with liquid nitrogen. In this column, helium was purified of hydrocarbons to residual concentrations lower than 2 × 10 -7 vol %. The concentration of impurities was controlled by gas chromatography using impurity accumulation in U-shaped glass trap 9 (5 cm in length and 3 mm in inner diameter) filled with silanized N-AW-HMDS ChromaAbstract -A procedure was proposed for the 2D gas-...