Method quantitative gas chromatographic determination of water in gas mixtures

 

Use: analytical chemistry, gas chromatography analysis of water. The essence of the invention: first, carry out the drying of the measuring system before dosing the analyzed gas mixture and concentration of the sample by alternating purge the system with inert gas during heating and vacuum to control the degree of drying in the background peak water on the control chromatogram of the atmosphere of the measuring system to complete the removal of the specified peak. The concentration of the samples are from a closed tank sorbirovaniya sample when cooled to the temperature of liquid nitrogen with subsequent deformirovanie when heated to temperatures above the boiling point of water. Desorption is carried out in the device type of the trap, made in the form of a U-tube immersed first in a cooling environment, then in a warming environment. Determination of water content are direct gas chromatographic method with measurement of the analytical signal detector thermal conductivity on the basis of conducting calibration measurements with the preparation of the calibration samples. Calibration measurement is performed on the calibration air samples, each of which is characterized by successively increasing pressure, with the spirit from its content in the reference air sample, determined by the psychrometer, the dosing of the analyzed gas mixture in the measuring system is carried out by passing through a metal tube, optionally placed between the test container and the trap is equipped with a heater, and gas chromatographic determination of water content carried out using a column filled with polychrome-1 as a solid carrier, the treated liquid phase. Technical result: investigation closed containers under pressure below atmospheric, ensuring expressnet analysis, simplification by eliminating the time-consuming preparation phase liquid calibration mixtures of fixed composition, improving the reliability of the method by reduction to homogeneous phase condition and analyzed and calibration samples. 1 Il.

The invention relates to the field of analytical chemistry, and in particular to methods chromatographic determination of water content in gas mixtures.

There is a method of quantitative gas chromatographic determination of water in gas mixtures, including dynamic determination of moisture in a moving stream of a gas mixture (g. "Laboratory", M, ed, "the Metallurgists who jnarno set of closed containers, under low pressure contained in the gas mixture, as well as the complexity in performing a double concentration and the presence of the ultrasonic detector is used to measure water content.

Known as the closest to the technical essence and the technical result of the claimed method quantitative gas chromatographic determination of water in gas mixtures (J. "Laboratory", M, ed, "metallurgy", 1981, T. 47, 4, S. 18), including pre-dosing of the analyzed gas mixture in the measuring system, the concentration of the sample by sorbirovaniya last when cooled inert gas to the temperature of liquid nitrogen with subsequent deformirovanie when heated to temperatures above the boiling point of water, which is carried out in the device type of the trap, made in the form of a U-tube immersed in a heated environment, chromatographic determination of water content by measuring the analytical signal detector thermal conductivity, conducting calibration measurements with the preparation of the calibration samples. In the prototype samples are pumped from the dynamic flow of the gas mixture.

The disadvantages of the prototype relative to the gas mixture in them, low expressnet analysis, the relatively high complexity of the training phase liquid calibration mixtures of fixed composition, the low reliability of the method by different heterogeneous phase being analyzed and the calibration samples.

The task of the invention is to develop a simple and reliable method for direct gas chromatographic determination of water in gas mixtures contained in closed containers under an arbitrary pressure, including pressure below or above atmospheric.

A new technical result provided when using the proposed method, is to provide research opportunities closed containers filled with gas mixtures under pressure below atmospheric, in ensuring expressnet analysis, simplification by eliminating the time-consuming preparation phase liquid calibration mixtures of fixed composition, to improve the reliability of the method by reduction to homogeneous phase condition and analyzed and calibration samples.

These task and a new technical result is achieved by the fact that in the known method the quantitative gazokhromatograficheskaya system and the concentration of the sample by sorbirovaniya last when cooled inert gas to the temperature of liquid nitrogen with subsequent deformirovanie when heated to temperatures above the boiling point of water, which is carried out in the device type of the trap, made in the form of a U-tube immersed first in the cooling, and then heating media, direct gas chromatographic determination of water content by measuring the analytical signal detector thermal conductivity, conducting calibration measurements with the preparation of the calibration samples, in accordance with the proposed method, before the selection of the analyzed samples, which is carried out on the studied closed containers, carry out the drying of the measuring system by alternating purge the system with inert gas during heating and vacuum to control the degree of drying in the background peak water on the control chromatogram of the atmosphere of the measuring system to the complete removal of the latter, calibration measurement is performed on the calibration air samples, each of which is characterized by successively increasing pressure, with the construction of calibration graphs of dependence of the peak height of water in each of the next calibration sample of air from its content in the reference air sample, defined as the psychrometer, the dosing of the analyzed gas mixture in the measuring system is carried out by passing through a metal tube, will complement epicheskoe determination of water content is performed with the use of columns, filled with polychrome-1 as a solid carrier, the treated liquid phase (6% polyethylene glycol brand PEG-2000).

The proposed method is illustrated as follows.

The drawing shows a diagram of the measuring system, where 1 - valves; 2 - analyzed a closed container (glass bottle); 3 - heated metal tube; 4 - exemplary gauge; 5 - trap; 6 - capacity cooling or warming environment; 7 - faucet-spout; 8 - chromatograph; 9 - source inert environment;
10 - vacuum pump;
11 measuring system.

The measuring system (11) is purged with inert gas by heating (3) and vacuum (10) to the lack of moisture in the background peak water. From a closed container (2) is dosed samples in the measuring system (11) according to the pressure measured (4). Then of the entire measuring system (about 120 ml) freezes out or concentrated moisture trap (5), after which produce a desorption contents of the trap by heating on an oil bath (6) switching using tap-dispenser desorbed sample to the separation column chromatograph (8), where the water is recorded as a peak with a heat conductivity detector and a potentiometer.

We offer issleduemoi gas mixture in the measuring system.

Dosing the analyzed gas mixture in the measuring system is carried out by passing through a metal tube, optionally placed between the test container and the trap is equipped with a heater. Using the proposed method, a metal tube is provided for organizing hub, which includes "the trap". Most preferably the use of tubes made of stainless steel, because in this case there is minimal permeability and adsorption capacity with respect to water.

Heating of the metal tube, the proposed method is provided in the stage preceding measurements for reliable deformirovaniya all contained in the measuring system of moisture, which also ensures the elimination of the factor of error and increases the accuracy carried out in the method of measurement.

The location of the specified metal tube between the test container and the trap leads to a reduction of the time required to clean the system from moisture and to concentrate it on the trap that provides simplification, expressnet and accuracy of the method.

The measuring system is first subjected to drying by alternating purge the system with inert gas the atmosphere of the measuring system to the complete removal of the latter, which reduces the accuracy of subsequent measurements.

Then spend the concentration of the sample in the device type trap by sorbirovaniya inert gas water as a cooling medium by cooling to liquid nitrogen temperature, resulting in cooling of the sample. Then hold deformirovanie when heated to temperatures above the boiling point of water held in the trap, made in the form of a U-shaped tube and immersed in a heating medium, for example in an oil bath. This consolidation into a single system hub land dosing (metal tube), traps allows the concentration directly from the closed to the measured capacitance and the subsequent measurement of the water in the analyzed sample, and in this respect provides the function and role, and the measuring system in the aggregate. This simplifies the whole system compared to the prototype and reduces the time for preparatory operations.

Next, perform a calibration measurement with the preparation of the calibration samples of air, each of which is characterized by successively increasing pressure, which depends on the magnitude of the concentration of water in analiziruemoi on the value of ~10 GPA, and if the water content is more than 20 carries.%, respectively, and the pressure in each sample will increase until close to atmospheric.

Preparation of calibration graphs of dependence of the peak height of water (in mm) in each of the next calibration sample air from the absolute water content in the last (g) is carried out after determination of absolute water content (in g/m3in the reference air sample, defined as the psychrometer. To do this, first take an arbitrary reference air sample from the environment and subjecting it to analysis on the psychrometer. The measured value of the water content in the air is used to construct a calibration graph. Then prepare calibration gas samples taken from the air in the working space, and using calibration graphs. The reliability of the method, as experiments show, is significantly enhanced by reduction to homogeneous phase condition and analyzed and calibration samples.

So it is, when using the proposed method allows the study of closed containers filled with gas mixtures under pressure below atmospheric, increased expressnet analysis and simplification by eliminating trudem is no reduction to homogeneous phase condition and analyzed and calibration samples.

The possibility of industrial use of the proposed method is confirmed by the following example.

Example 1. In laboratory conditions the proposed method was tested on the pilot plant, made in the form shown schematically in the drawing.

The measuring system contains the initial heated tubular electric furnace dispenser (3) trap (5), made in the form of a U-shaped tube made of metal, vacuumer (4), faucet-spout (7) and cranes switch (1). Analyzed capacity (2) is selected in the form of a glass bottle, pre-cleaned of moisture, which fill the analyzed gas mixture. Analyzed three samples analyzed gas mixture containing water (according to data parallel proven by other methods), relates.%:
Sample 1 - 8,3
Sample 2 - 7,3
Sample 3 - 0,28
The same samples 1, 2 were analyzed by the method of indicator tubes, and sample 3 - method Ilova, relates.%:
Sample 1 - 10,0
Sample 2 - 7,0
Sample 3 - 0,306
Drying of the measuring system was carried out in a dry helium by flooding and subsequent download of the atmosphere while heating the steel tube. After drying of the measuring system was tested in the absence of moisture, for which it was pumped to use VoSKY in an environment with silicone oil 5 (St-5, GOST 13004-77) on the separation column. In the absence of background peak measuring system is ready for operation.

The analyzed gas is taken in a measuring system according to the gauge. For kontsentrirovanija down under the liquid nitrogen trap and open the valve on the pump. Then switch the tap-dispenser onto the column and defrost trap oil bath (120o(C) within 6 C. Application of a direct gas-liquid option chromatography (unlike the prototype) allowed to exclude the operation of drying the carrier gas and to improve the peak symmetry of the water and its separation from accompanying impurities and consequently increase the reliability of analysis results.

For sampling from remote from the main laboratory systems used glass bottles as closed containers that previously obzharivalas repeated washing by air when heated with subsequent release into the atmosphere.

Gas chromatographic determination of water content carried out using a column filled with polychrome-1 as a solid carrier, the treated liquid phase.

As the liquid phase for processing polychroma-1 was used the solution polietilen the detection Limit of the investigated water in the investigated gas mixtures 0,02 relates. % (0.004 g/m3) is obtained from a sample volume of ~40 ml In the range of concentrations of 0.2-80 carries.%, error definition is 11-17%.

So it is, when implementing the proposed method in laboratory conditions provided research opportunities closed containers filled with gas mixtures under pressure below atmospheric, increased expressnet analysis and simplification by eliminating the time-consuming preparation phase liquid calibration mixtures of fixed composition, as well as improving the reliability of the method.


Claims

Method quantitative gas chromatographic determination of water in gas mixtures, including the dosage of the analyzed gas mixture in the measuring system and the concentration of the sample by sorbirovaniya last when cooled to the temperature of liquid nitrogen with subsequent deformirovanie when heated to temperatures above the boiling point of water, which is carried out in the device type of the trap, made in the form of a U-shaped tube, dip first into the coolant, and then heating media, direct gas chromatographic determination of water content by measuring the analytical signal of the detector telopt selection of the analyzed samples, which is carried out on the studied closed containers, carry out the drying of the measuring system by alternating purge the system with inert gas during heating and vacuum to control the degree of drying in the background peak water on the control chromatogram of the atmosphere of the measuring system to remove the last calibration measurement is performed on the calibration air samples, each of which is characterized by successively increasing pressure, with the construction of calibration graphs of dependence of the peak height of water in each of the next calibration sample of air from its content in the reference air sample, defined as the psychrometer, the dosing of the analyzed gas mixture in the measuring system are passing through the metal tube, additionally placed between the studied closed tank and trap, equipped with a heater, and gas chromatographic determination of water content carried out using a column filled with polychrome-1 as a solid carrier, the treated liquid phase.

 

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FIELD: analytical instrumentation engineering; chromatographic analysis of composition of substances.

SUBSTANCE: proposed method includes delivery of carrier gas to evaporation chamber through gas supply line, introduction of sample into evaporation chamber, delivery of part of gas flow from evaporation chamber to chromatographic column and discharge of remaining of gas flow to atmosphere. Delivery of carrier gas to evaporation chamber is effected in direction opposite to motion of evaporated sample to chromatographic column. Device proposed for introducing the sample into chromatograph has sample introducing line, evaporation chamber, chromatographic column, carrier gas supply and carrier gas discharge line which are connected with evaporation chamber. Carrier gas discharge line is connected with evaporation chamber in area of introduction of sample and carrier gas supply line is connected with opposite end of evaporation chamber.

EFFECT: enhanced accuracy of dosing the sample; improved quality of separation of components; enhanced reliability; simplified construction.

11 cl, 3 dwg

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