SU450101A1 - Method for detecting mixture components in gas chromatography - Google Patents

Description

one

This invention relates to gas chromatography.

There is a known method for detecting gases by thermal conductivity, density, etc. or the component is changed, which causes the detector signal. Depending on the magnitude of this property for different components and on the concentration of the component in the carrier gas, the magnitude of the detector signal also varies.

The main disadvantage of the existing detection methods is that, with the same volumetric concentrations in the analyzed mixture, different components cause different magnitudes of the detector signals. This circumstance necessitates a preliminary determination of the correction factors for each detected component, which is reduced to the calibration of the detector for each component, which takes a lot of time and requires the use of expensive clean components. According to the known methods of gas detection, before determining the correction factors, it is necessary to carry out component identification, i.e., to determine which peak in the chromatogram corresponds to a particular component, which also requires the use of pure componeite.

In order to increase the stability of the measurements according to the proposed method, the measurement of the change in the concentration of the carrier gas is carried out after its diffusion through the porous partition into the flow of another carrier gas.

The drawing shows a diagram of the device that implements the proposed method.

Gases from the chromatographic column flow through chamber 1, which is separated from chamber 2 by a thin polystyrene membrane 3. Additional gas, for example air or nitrogen, is pumped through chamber 2. The stream coming out of chamber 2 enters the gas analyzer 4. When a pure carrier gas, for example hydrogen, flows through chamber 1, a part of the latter diffuses through polystyrene membrane 3 into chamber 2. At the same time, in a stream of air flowing through chamber 2, The concentration of hydrogen is measured by the magnitude of any physicochemical parameter by the gas analyzer 4. This signal level of the gas analyzer is taken as the initial one. When a component enters the column 1 with the carrier gas, the volume concentration of hydrogen in chamber 1 is reduced by the volume concentration of this component. This leads to the fact that the amount of hydrogen diffused through membrane 3 into chamber 2 is reduced proportionally. Thus, the concentration of hydrogen in the gas flow to the gas analyzer is reduced, as measured last. Moreover, this decrease in the concentration of hydrogen is proportional to the volume concentration of the leaked fluid, with the carrier gas through chamber 1 at the given time of the detected component. Since for all substances except hydrogen, the polystyrene membrane is practically impermeable, the various components at the same concentrations in the carrier gas cause the same changes in the concentration of hydrogen in chamber 2, and consequently, the same signals from the gas analyzer. Therefore, the method allows the detection of any components with the same radiation.

When calculating chromatograms obtained using devices that implement the described method of detection, there is no need to determine correction factors for the detected components, the need to use pure components to determine them, and it is possible to calculate chromatograms without first identifying all the components. The calculation of the volume concentration of any component is carried out according to the formula

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since all the coefficients of the relative sensitivity of the detector for the t-ro component are equal to one (Si is the peak area of the t-ro component).

The detection sensitivity is determined by the sensitivity of the gas analyzer used. Thermoconduction, densitometric, radiological, electrochemical, and other devices that are sensitive to hydrogen, oxygen, or nitrogen can be used as a gas analyzer.

Subject invention

A method for detecting mixture components in gas chromatography, based on measuring the change in carrier gas concentrate, characterized in that, in order to increase the stability of the measurements, the change in the carrier gas concentration is measured after diffusion through the porous barrier into the flow of another carrier gas.

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