SU940052A1 - Gas chromatograph for analyzing air for micro-impurities - Google Patents

Description

(54} GAS CHROMATOGRAPH FOR ANALYSIS OF AIR ON MICROPRIMES

The invention relates to analytical gas chromatographs, the action of which is based on the combination of a preliminary thermo-adsorption enrichment of a sample with its subsequent chromatographic separation. A gas chromatograph is known, containing three parallel columns in a common thermostat with three detectors, designed to detect trace impurities in air LI. However, the high sensitivity, which is not consistent with the selectivity of the column system, limits the possibility of using such a device only in those cases where the number of recorded impurities does not exceed 20-30. A gas chromatograph is known for analyzing air on micronutrients containing a carrier gas preparation unit, a gas flow switching unit, parallelly included analytical columns, the total output of which is connected through a gas flow switching unit to a carrier gas preparation unit, a detector connected to a common output of analytical columns, a cumulative column with a heater, connected through a gas flow switch unit with a common input of analytical columns, a metering pump connected to a cumulative column minutes, and a control unit 2. The chromatograph apparatus Disadvantages: sorption at cryogenic temperature is substantially not selective, that in a significant number of the impurities separation is difficult; the chromatograph needs an external booster and flow detector for sampling; the regeneration system with a continuous flow of gas carrier is associated with a high flow rate of the carrier gas. This reduces the sensitivity and selectivity of the analysis. The purpose of the invention is to increase the sensitivity and selectivity of the analysis. This goal is ensured by the fact that a gas chromatograph for analyzing air on microimpurities, containing a carrier gas preparation unit, a gas flow switching unit, parallel-connected analytical columns, the total input of which is connected to the gas-carrier preparation units via the gas flow switching unit, the ctector connected with a common input of analytical columns, a cumulative column with a heater, connected through a gas flow switch unit with a common input of analytical columns, a metering pump, connected with the accumulator column and the chromatograph control unit, equipped with individual heaters of analytical columns connected to individual temperature programmers, entered into the control unit, and a carrier gas accumulator connected to the carrier gas preparation unit and through the additionally controllable shut-off valve - with the end of the cumulative column, which is connected with the dosing pump The drawing shows a circuit diagram of the proposed chromatograph. The chromatograph contains a carrier gas supply nozzle 1, a carrier gas preparation unit 2, a thermostat 3, a flow switching unit 4 with a throttle 5. The chromatograph also has a sampling nozzle 6, a balancing choke 7, an analytical column 8, an electronic processing unit 9 signal, heaters 1O Colono 8, detector 11 and fitting 12 for collecting gas and gas. In addition, it is equipped with a heater 13, a control unit 14 including temperature charts, one knee 15, a metering pump 16, a sample vent 17, a carrier gas accumulator 18 and shut-off valves 19-26. The chromatograph works as follows. When the mode is reached, the basic temperatures of the heaters 10 and 13 and the thermostat 3 and a stable flow of carrier gas from the carrier gas preparation unit 2 are established through valve 19, parallel / junior analytical columns 8, detector II and open valve 26. Then (at the command of the unit 14), a pump doser 16 passes a certain volume of the sample through fitting 6, valve 23, accumulator 15 and valve 24. Such a direction of movement of the sample excludes the influence of volumes and surfaces; Dose Dose To01. 16 and associated valves and communications for representativeness of the sample. In the accumulation column 15, filled with selective sorbents, at a temperature close to the ambient temperature, there is a selective absorption of trace contaminants from the air. Then the sample is isolated in the accumulation column 15 and the heater 13 is turned on. In this case, micro-admixtures desorb and increase: their concentration in the gas phase, equal to ε ft - the volume deviation. The gas phase and sorbent are in the cumulative column, and G. and D are the Henry coefficients of the ith component at the sorption and desorption temperatures, respectively. After establishing a new sorption equilibrium, the carrier gas carries the sample into parallel analytical columns 8, the heaters 10 of which allow control of the movement of the sample zones in each of them in such a way that the time of peak output from each column 8 does not coincide. The selectivity achieved by the mode of sampling and sample entry is complemented by the separate programming of the temperature of the columns 8 and the possibility of using different sorbents in them. The sample exhaust from the metering pump 16 can be carried out during the analysis through the valve 25. At that time, the sorbent regenerates in the Accumulation Column 15. The regeneration proceeds as follows. The isolated storage column 15 is at a maximum temperature for a time sufficient for the sorption equilibrium to occur, after which valves 22 and 23 open briefly. A small volume of carrier gas from the accumulator 18, a little larger than the free volume of the storage column 15, carries out the degassed components into the environment. After this, column 15 is again isolated at the same temperature for the time of the settling of the new equilibrium and the repetition purge pulse. Thus, the volume of carrier gas i is equal to nV, where n is the number of pulses, the free volume of the storage column and the communications connected with it, are expended on the regeneration. Practically, p i 10. The proposed chromatograph makes it possible to increase the sensitivity of the analysis and the selectivity of the determination of microimpurities by 50%.

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A gas chromatograph for the analysis of air on microimpurities, containing a carrier gas preparation unit, a gas flow switching unit, parallel connected analytical columns, whose common input is connected to a carrier gas preparation unit through a gas flow switching unit, a detector connected to an optical input columns, a cumulative column with a heater connected through a gas flow switch unit with a common inlet of analytical columns, a pump-aaaagor connected to the cumulative column, and a control unit detecting chromatograph, differing ide - and u and in that, in order to increase the selectivity and 5gvstvitelnosti analysis, it is provided with individual heaters E 95

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Analytical columns, connected with individual IBM programmers of the controller, entered into the control unit, and a carrier gas accumulator, co-connected with the preparatory unit {carrier gas) through the additionally controlled shut-off valve - with the end of the accumulator plate, which is connected dosing pump.

Sources of information taken into account in the examination

1. Lem D. Application of a gas chromatograph in a spacecraft with a man on board. Aerospace Medicine, 1967, p. 1110-1117.

2. Micro-2 chromatograph (technical description and operating instructions 5 E 1.550.O53.TO). Dzerzhinsky gas analysis equipment plant, 1974, (prototype).

Claims (1)

Claim A gas chromatograph for analysis of air on microimpurities, containing a carrier gas preparation unit, a gas flow switching unit, analytic columns connected in parallel, whose common input is connected through a gas flow switching unit to a carrier gas preparation unit, a detector connected to 10 the input of the analytical columns, the storage column with a heater connected through the gas flow switching unit to the common input of the analytical columns, a metering pump connected 15 to the storage column, and the unit It is noteworthy that, in order to increase the sensitivity and selectivity of the analysis, it is equipped with individual heater-> qm analytical knees connected to individual temperature programmers inserted into the control unit and a carrier gas accumulator, connected to the preparation of the carrier gas through an additionally introduced controlled shut-off valve with the end of the accumulation elbow, which is connected to the metering pump.