GB924094A - Improvements in or relating to gas-liquid or gas-solid chromatography - Google Patents

Abstract

<PICT:0924094/III/1> <PICT:0924094/III/2> <PICT:0924094/III/3> <PICT:0924094/III/4> In a gas chromatograph comprising a gas chromatographic column (3) with a solid or solid-supported liquid absorbent, a katharometer (5) having chambers (12, 13) with electrical heating elements for a carrier gas stream and the emergent gas stream, and a comparator circuit, the katharometer is housed in a chamber formed in a heat-conductive mass (1) having thermostatically-controlled heating means (6) encased therein. As shown in Fig. 1, to which the above numerals relate, the chromatographic column 3 and a reference column 2 are coiled around a sheath 1b between which and an inner cylinder 1a (which together form the heat-conductive mass) is an insulated heating coil 6 and a bare wire coil 6a to prevent inductive disturbances. A thermostat 8 is provided in cylinder 1a, close to the heating element. Gas to be analysed enters column 3 at 39 and passes via end 30 and capillary tubes 30a, 31 into the sensing chamber 13 of the katharometer, while the reference gas similarly enters chamber 12. The gases thereafter enter cross bores 17, 16 and are withdrawn through common outlet 32. The assembly is surrounded by a cylindrical casing 33 having a base 35 and lid 34 and the unoccupied space is packed with glass wool. In Fig. 5 is shown a flow sheet for the apparatus: carrier gas enters at 52, is dried, if necessary, in tube 54 and passes to a buffer volume 60 whence a reference gas stream passes to column 2 and the katharometer H and a part is taken through line 60a and column 3. Valves 89, 87 and 88 provide for alternative flow of the carrier gas directly to column 3 or via sample volume 69. Valves 85, 86 provide for the filling of volume 69 from gas pipeline 66 for the gas to be analysed. The valves are operated by means of device 79 (see Fig. 4). Compressed air is admitted to opening 84 and operates the above mentioned valves, which correspond to lines 89b, 87b, 88b, 85b and 86b respectively of device 79. Piston 81 driven by motor 82 opens the above mentioned lines to programme the taking of a sample. The result of the analysis is recorded as a chromatogram at R using an amplifier A for the output of a Wheatstone bridge aircuit. The apparatus may be used to purify UF vapours at sub-atmospheric pressure and elevated temperature using a column packed with ground solid polytrifluorochloroethane supporting polytrifluoro-chloroethylene oil.