GB874742A - Improvements relating to vapour fractometer apparatus - Google Patents

Abstract

<PICT:0874742/III/1> An assembly of gas chromatography apparatus comprises a source of carrier gas (33) and a series of interconnectable units each comprising a column (30, 31, 32), a sample injection means (41, 42, 43 for liquids or 47, 48, for gases), a thermal conductivity assembly (44, 45, 46) comprising two cells, one connected to the source of carrier gas and the other to the outlet of the column and a vent (51, 55), each unit in said series of units except the last also including a coupling valve (49, 50) having two positions in the first of which it simultaneously connects the column to the vent and the adjacent column to the source of carrier gas and in the second of which it simultaneously connects the column effluent to the input of the adjacent column and the source of carrier gas to the restricted vent. In the apparatus shown in Fig. 2, to which the above numerals relate, there are also provided pressure regulators 35, 37, 38 and associated gauges for the carrier gas on the inlet side of the columns, and on the outlet side, valves 47, 48 for the introduction of gas samples into the subsequent column, and alternative flows governed by solenoid-operated valves 52, 56, 59 to flow meters 53, 57, 60 or sampling devices 54, 58, 60. The columns may be of different kinds (as many as six different substrates are mentioned) and may be enclosed in temperature controlled chambers, and usually these will be at progressivly lower temperatures: the third column can be refrigerated. In use, a liquid sample may be introduced through injection device 41 which vaporizes the sample which is carried into the column by a gas, e.g. helium from source 33. After partial separation in the column, the effluent passes through the thermal conductivity assembly and produces an electrical response which is recorded on a strip chart: in the position of the valve 49 shown, further resolution of the sample is effected by passage through column 31, but by rotating the valve through 90 degrees the effluent may be vented whilst pressure and flow conditions in column 31 remain undisturbed, since it is thereby connected to the carrier gas source. Similar considerations apply to column 32 and hence an initial separation may be effected in column 30, poorly resolved effluent passed into column 31 for further resolution, effluent remaining unresolved in column 31 being finally passed to column p 32. Meanwhile columns 30 and 31 continue to function normally and provide continuous charts of their respective effluents. Cyclic operation may be achieved by returning the effluent from column 32 to the inlet of column 31 by means of line 63 and associated valves 62, 64: procedural details are given. Mixtures mentioned are gasoline, reaction products and food flavours; and mixtures of C2-C7 hydrocarbons, of high-boiling glycols in low-boiling alcohols, of a mixture of saturated and unsaturated C3-C5 hydrocarbons, including separation of butene isomers, and of a mixture of O2, N2, CO2, ethane and propane. The invention is particularly suitable for analysis of low-boiling trace components in high-boiling substrates.