Gas chromatograph for analysis of substances in mixtures of gases and/or vapors

 

(57) Abstract:

Gas chromatograph for analysis of substances in mixtures of gases and/or vapors contains a source of carrier gas, a device for introducing a metered quantity of the analyzed mixture into a stream of carrier gas, comprising a dosing tube with an internal volume, one end of which is connected to a source of carrier gas through a pipeline for supplying a carrier gas, which has managed the shut-off valve and pipeline for the supply of the sample mixture of substances, chromatographic column, the input of which is connected to the second end of the dosing tube with an internal volume, the pump gas flow connected to the second end of the tube and the detector. Chromatograph contains an additional pipeline for supplying a carrier gas, connecting a source of carrier gas to exit the chromatographic column. The device is equipped with three stops gas flow, one of which is installed in an additional pipeline, the second pipeline for the supply of the sample mixture of substances, and the third is connected to the pump flow. 3 C.p. f-crystals, 6 ill.

The invention relates to the field of analytical instrumentation and, in particular, to devices for x is Rania harmful pollutants volatile organic and inorganic substances, for example, impurities benzene, toluene and xylene at MPC in the atmospheric air. Known gas chromatograph for analysis of substances in the gas and/or steam mixtures containing a source of carrier gas, tap-dispenser, comprising a piece of a tube with a grooved inner volume, the pipeline for the supply of the sample mixture of substances, is connected to one of inputs of the tap-dispenser, chromatographic column connected to one of the outputs of the tap-dispenser, and a detector connected to the output of the chromatographic column (see U.S. patent N 3748833, NCI 55-197, 1973).

Feature known chromatograph, widely used to date for the purposes of the analysis of impurities in the gas and/or steam mixtures, is the need to use the tap-dispenser for selection of a metered quantity of the analyzed mixture and transfer samples to the input of the chromatographic column in a stream of carrier gas. This raises a number of disadvantages. First, tap-dispenser is a rather complex and expensive device. Reliability and service life of the tap-dispenser, especially when working at elevated temperatures (> 300oC), is very limited due to abrasion of the rubbing surfaces of the valve. Cruda on the elements of the crane and, in particular, the sealing elements. This leads to a distortion of the composition of the analyzed mixture and, as a consequence, errors in its analysis.

Closest to the proposed gas chromatograph the gas chromatograph for analysis of substances in mixtures of gases and/or vapors containing the source of carrier gas, a device for selecting and entering into the flow of carrier gas metered quantity of the analyzed mixture of substances, comprising a piece of a tube with metering internal volume, one end of which is connected to a source of carrier gas through a pipeline for supplying a carrier gas, which has managed switching valve, a pipe for supply of the sample mixture of substances, coupled with the end of the dosing tube with an internal volume associated with the source of the carrier gas chromatographic column, the entrance of which is connected to the end of the tube with a calibrated internal volume, opposite the place of its connection with the pipeline for the supply of the sample mixture of substances, booster gas flow, connected by pipeline with the inlet of the chromatographic column and the dosing tube with an internal volume, and a detector connected to the output of the chromatographic the AFA, taken as a prototype, is that the inlet and outlet tubes with grooved inner volume filled with particles of sorbent, installed cranes switches threads that essentially perform the role of tap-dispenser with elements which the analyte in contact with the transition from the pipeline for the supply of the sample mixture of substances into the dosing tube with internal displacement. This complicates the design of the chromatograph, reduces the reliability of his work and leads to distortion of the composition of the analyzed mixture and, as a consequence, errors in its analysis. In addition, in the known chromatograph are windproof gas volumes, filled with substance samples, which are formed at the junction of the pump flow from the inlet of the chromatographic column and the outlet of the dosing tube with internal displacement. This leads to additional errors in the analysis. Another disadvantage of the known chromatograph is that it does not provides cleaning of the pipeline for the supply of the sample mixture from the residue of the sample before each new analysis.

The objective of the invention was to eliminate the contact of the analyzed mixture with any switching device is in La chromatographic column and to provide treatment of the interior volume of the chromatograph from the residue of the sample before each new analysis.

This task is solved in that the proposed gas chromatograph for analysis of substances in mixtures of gases and/or vapors containing the source of carrier gas, a device for introducing a metered quantity of the analyzed mixture of substances in a stream of carrier gas, comprising a dosing tube with an internal volume, one end of which is connected to a source of carrier gas through a pipeline for supplying a carrier gas, which has managed the shut-off valve and pipeline for the supply of the sample mixture of substances, chromatographic column, the input of which is connected with the second end of the dosing tube with an internal volume, the pump flow rate, connected to a second end of the tube with metering internal volume and the detector, which according to the invention an additional pipeline to stop the flow of gas, one of which is installed in an additional pipeline for supplying a carrier gas, and the second is installed in the pipeline for the supply of the sample mixture of substances, and the third is connected stimulate consumption.

Because of the marked peculiarities of the proposed chromatograph completely eliminates the contact of the analyzed mixture of substances with any of perekljuchi the analyzed mixture in a chromatographic column. In addition, thanks to the implementation of the chromatograph completely excluded windproof volumes ("bags") in the path of flow of carrier gas into the chromatographic column. And finally, all the internal volumes of the chromatograph before each new analysis is purified from the residue samples by Stripping the flow of carrier gas. All this leads to improved accuracy and reproducibility of the analysis by excluding changes in the composition of the analyzed mixture used for dosing and transfer to the chromatographic column and increases reliability by eliminating the switching devices in contact with the sample at elevated temperatures.

In a preferred embodiment of the chromatograph it introduced the second chromatographic column is installed between the first chromatographic column and detector, and operated shut-off valve installed in an additional pipeline for supplying a carrier gas.

Another difference chromatograph is that the booster gas flow is made in the form of a cylindrical tank with installed inside with the possibility of reciprocating movement of the piston rod connected to the drive.

Among the Ares of the fluid, installed in the pipeline for the supply of carrier gas connected to the dosing tube with internal volume.

The invention is illustrated by drawings. In Fig. 1 and 2 presents a schematic diagram of the proposed chromatograph without preconcentration of the sample in two operating positions: Fig. 1 - at the time of sampling, Fig. 2 - at the time of analysis.

In Fig. 3 and 4 shows a schematic diagram of the proposed chromatograph with preliminary concentration in two operating positions: Fig. 3 - at the time of selection and concentration of the sample, Fig. 4 - at the time of analysis.

In Fig. 5 and 6 shows a schematic diagram of the preferred option run chromatograph in two operating positions.

Chromatograph (Fig. 1 and 2) contains the source 1 carrier gas, such as compressed gas (N2, He, H2and others), the output of which is a regulator 2 pressure gas. The output of regulator 2 pressure connected with two pipes 3 and 4 for supplying a carrier gas. The pipe 3 for supplying a carrier gas is connected to the end of the tube 5 with the metering internal volume and a pipe 6 for the supply of the sample mixture of gases and/or vapors. In the pipe 3 is installed managed constipation is Noah liquid or liquid-propellant. In the pipe 6 for the supply of the sample mixture has a limiter 9 thread, made for example in the form of a segment of a capillary tube of small cross section. Line 6 its output end 10 is connected to the source of the analyzed mixture of substances, for example, with atmospheric air. The second end of the tube 5 with the metering internal volume connected to the input of the chromatographic column 11, for example, the entrance of the capillary chromatographic column, and the input of the booster 12 gas flow, for example, a pump. In the outlet port 13 of the pump 12 of the gas flow has a limiter 14 of the gas flow is performed, for example, in the form of a segment of a capillary tube of small diameter. The output of the chromatographic column 11 is connected to the input of the detector 15, such as photoionization detector. To the input of the detector is connected and the pipe 4 for supplying a carrier gas, which features a limiter 16 flow of carrier gas, made in the form of a segment of a capillary tube of small cross section. Pneumatic resistance of the limiter 10 flow is chosen equal to the pneumatic resistance of the column 11. When used as a chromatographic column 11 capillary chromatographic column pneumatic resistance limiters 9 and 14 of the flow and 5 metering internal volume placed in thermostat 17 and 18, respectively (shown in Fig. 1 and 2, dashed lines). thermostat 17 and 18 can be separate units or they can be combined into a single unit.

The chromatograph is equipped with a computer 19, which controls the operation of valve 7 and thermostats 17 and 18.

Chromatograph operates as follows. During the selection of the analyzed mixture (Fig.1) operated shut-off valve 7 is closed and the flow of carrier gas from source 1 via line 4 through the limiter 16 stream is fed to the input of the detector 15. At the same time include a booster 12 gas flow, which begins to pump the analyzed mixture of gases and/or vapors from the source of the analyzed mixture (Fig. 1 not shown) via the pipeline 6 for the supply of the sample mixture through the tube 5 with the metering internal volume and the outlet nozzle 13 through the limiter 14 flow displays its contents in the atmosphere.

After filling the metering internal volume of the tube 5 of the analyzed mixture of substances under computer 19 controlled shut-off valve 7 is opened, turning the gas scheme chromatograph in the position shown in Fig. 2. In this position, the portion of the flow of carrier gas from source 1 via line 4 through the limiter 16 stream is fed to the input of the detector 15 will istubal to the connection pipe 6 for the supply of the sample mixture and the tube 5 with the metering internal volume, where it is divided into two parts. A large part of the flow of carrier gas through the pipeline 6 through the limiter 9 flow discharged into the source of the analyzed mixture (atmosphere or process piping), and a smaller portion of the flow of carrier gas enters the tube 5, displacing the metered quantity of the analyzed mixture of substances contained in the internal volume of the tube 5, and moving it to the entrance to the chromatographic column 11. At the entrance to the chromatographic column, the flow of gases and/or vapours from the tube 5, is divided into two parts, proportional pneumatic resistance of the column 11 and the stopper 14 of the thread. A smaller part of a measured amount of the analyzed mixture with a flow of carrier gas is transferred to the chromatographic column 11 where it chromatographic separation of the individual components of the mixture. A large part of the metered volume of the analyzed mixture with a flow of carrier gas through the booster 12 flow outlet 13 and the stopper 14 of the flow is discharged into the atmosphere. At the inlet of the chromatographic column 11 divided components of the analyzed mixture are detected by a detector 15. Shut-off valve 7 remains open until, until you exit the column 11 lastly is the temperature may rise for a given program with a thermostat 17 with adjustable temperature. While in column (11) is in the process of chromatographic separation of the administered dose of the analyzed mixture of substances, the internal volume of the pipes 6 and 13 with installed limiter 9 of the stream (line 6) and the booster 14 gas flow otdyvautsya flow of pure carrier gas, which cleans the inner surface of the pipes with specified elements from the remnants of the substances of the sample. To fully release the internal volume of the pipes 6 and 13, and the tube 5 from residue trials, it is advisable with the help of microspace in the evaporation chamber 8 to introduce a metered quantity of distilled water (0.1 ml). When the temperature of the evaporation chamber 8 support in the range of 120 - 150oC. Formed under these conditions, water vapor, high pressure effect, completely cleanse the internal volume of the chromatograph from the residue of the sample. When you are finished cleaning the interior volume of the chromatograph by the flow of carrier gas and water vapor, block valve 7 and the gas scheme chromatograph is switched to the position shown in Fig. 1. Then again by the above procedure carry out the sampling of the analyzed mixture and chromatographic analysis.

Another difference of this variant execution chromatograph is that the booster 12 gas flow is made in the form of a cylindrical tank with installed inside with the possibility of reciprocating movement of the piston 22 and rod 23 connected to the drive (Fig. not shown).

This embodiment of the chromatograph operates as follows. In the time preceding the sampling of the analyzed mixture (Fig. 3), the valve 7 is closed and valve 21 is opened. The piston 22 is in the down position in a cylindrical tank of booster 12 gas flow. When this position of the valves 7 and 21, the flow of carrier gas from source 1 via line 4 through the open valve 21 and the limiter 16 stream is directed to wher, manual) in the upper position. When moving the piston 22 in the upper position at the end of the tube 5 connected to the chromatographic column 11, a vacuum is created and analyzed a mixture of source (e.g., atmosphere) under the action of the vacuum on the pipe 6 for the supply of the sample mixture through the limiter 9 flow enters the tube 5, where the sorption of the mixture components on the particles 20 of the sorbent. By the time the piston 22 to its upper position in the internal volume of the tube 5 is partially or completely filled with a mixture of substances, most of which is in the adsorbed state in the layer of particles 20 of the sorbent. Note that in moving the piston 22 upward along with the fence of the analyzed mixture through the pipeline 6 into the tube 5 is drawn in air from the atmosphere through the limiter 14 flow into the inner volume of a cylindrical tank of booster 12 stream.

After filling the internal volume of the tube 5 of the analyzed mixture carry out the switching valve 7 and 21 into a new working position (Fig. 4), in which the valve 7 is open and the valve 21 is closed. When this position of the valves 7 and 21 include a thermostat 18 for effecting heating of the casing tube 5 is the current carrier gas, coming through the pipe 3 into the tube 5, the desorbed substances analyzed mixture is partially transferred from the tube 5 in the chromatographic column 11, where they chromatographic separation and subsequent detection of the separated components of the mixture at the outlet of the column 11 by detector 15. A large part of the analyzed substances by the flow of carrier gas from the tube 5 through the internal volume of the pump 12 of the flow is discharged into the atmosphere. To accelerate the analysis process after exit from the column 11 of the components of the mixture of interest for analysis (for example, benzene, toluene and xylene), on command from the computer 19 using thermostat 17 is the rise of the temperature of the column 11 for quick release column from the heavy components of the mixture that are not of interest for analysis. In Fig. 5 and 6 shows a schematic diagram of the preferred option run chromatograph. This option is run is different from that described above (Fig. 1 - 4) the fact that the chromatograph entered the second chromatographic column 24, one end of which is connected to the input of the first chromatographic column 11 and the other end connected to the detector 15. When the booster 12 gas flow is made in the form cilindros 23, coupled with the actuator (Fig. not shown).

The described embodiment of the chromatograph operates as follows. Before sampling valve 7 is closed and valve 21 is opened (Fig. 5). The piston 22 is installed in a cylindrical tank the pump 12 of the gas flow in the lowest position. The flow of carrier gas from source 1 through the additional pipe 4 through the open valve 21 and the stopper 16 of the flow supplied to the connection point of the first chromatographic column 11 and the second chromatographic column 24, passes through the second chromatographic column 24 and the detector 15 and is discharged into the atmosphere. When the sampling of the analyzed mixture of substances piston 22 through shaft 23 and drive (manual) move from extreme lower position in a cylindrical tank the pump 12 to flow in at the top. During this movement of the piston 22 at the ends of the tube 5 and the first column 11, connected to the booster 12 flow rate, vacuum is created, through which the inner space of the tube 5 through the pipe 6 through the stopper 9 of the gas flow begins to enter the analyzed mixture of gases and/or vapors from the source of this mixture (e.g., atmospheric air), which fills the interior of the dosing volume Proc. of the rum samples by creating a vacuum at the inlet of the booster 12 gas flow in the internal volume of a cylindrical tank the pump 12 begins to flow the carrier gas, coming through the pipe 4 to the exit of the chromatographic column 11, which is connected with the second end of the chromatographic column 24. Also in the internal volume of a cylindrical tank the pump 12 of the gas flow by creating a vacuum at its output is fed through a limiter 14 flow through the pipeline 13 atmospheric air. With this in mind, the internal volume of a cylindrical tank the pump 12 of the gas flow rate is chosen so that during movement of the piston 22 from extreme lower position to the upper end of the inner dosing volume tube 5 has been completely filled analyzed by a mixture of gases and/or vapors. For example, if the internal volume of the metering tube 5 is 1 ml, to perform the specified conditions of the internal volume of a cylindrical tank the pump 12 of the gas flow rate is chosen equal to 10 to 100 ml, depending on the ratio of the pneumatic resistance of the limiter 9, 14 and 16 of the gas flow and the chromatographic column 11.

After filling the metering internal volume of the tube 5 of the analyzed mixture of gases and/or vapors upon command from the computer 19 controlled shut-off valves 7 and 21 are transferred to the second working position (Fig. 6), in which the valve 21 is closed and valve 7 outcry is fed to the input of the tube 5, where it is divided into two parts. The majority (2/3) of the thread on the pipe 6 through the limiter 9 flow discharged into the source of the analyzed mixture (e.g., the atmosphere), Ottawa the internal volume of the pipeline 6 and the limiter 9 from residue samples. A smaller portion of the flow of carrier gas (1/3) enters the internal volume of the tube 5 and displaces it metered quantity of the substance in the sample to the input of the first chromatographic column 11. At the entrance to the first chromatographic column 11, the gas flow is again being divided into two parts. Most of the flow (9/10) through the internal volume of a cylindrical tank the pump 12 of the gas flow through the pipe 13 and the stopper 14 of the flow is discharged into the atmosphere. A smaller portion of the gas flow (1/10) together with the analyzed substance enters the first chromatographic column 11 and then the second column 24.

Analyte, moving with the flow of carrier gas through a chromatographic column 11 and 24, are split into separate components, which are detected at the column outlet 24 by means of the detector 15. Without waiting for the complete separation of substances in columns 11 and 24, when the heaviest components of the analyzed mixture,supplied shut-off valves 7 and 21 in the working position, is depicted in Fig. 5, in which the valve 7 is closed and valve 21 is opened. When this position of the valve the flow of carrier gas through the pipeline 4 through the open valve 21 and the stopper 16 of the flow output of the first chromatographic column 11, where it is divided into two parts. A smaller portion of the flow of carrier gas is supplied into the second chromatographic column 24 and continues the transfer received it the analyzed substances to its output and then to the detector 15. A large part of the flow of carrier gas enters the first chromatographic column 11, carrying her back blowing and blowing remaining substances through the limiters 9 and 14 flow into the atmosphere. The processes of separation of light components of the analyzed mixture of interest for analysis occurring in the second chromatographic column 24, and the process of Ottawa heavy components of a mixture, not of interest for analysis by the reverse flow of carrier gas from the column 11 are aligned in time. This allows to reduce the analysis time.

After completion of the analysis process, the piston 22 through shaft 23 and the drive is transferred to the lowest position in a cylindrical tank of booster 12 consumption and re-start of the Oia at the output of the tube 5 when moving the piston 22 from extreme lower position at the top.

It should be noted that in all possible variants of the proposed chromatograph (Fig. 1 - 6) when selecting a metered amount of sample analyzed is a mixture of gases and/or vapors and a flow of carrier gas in the separation chromatographic column 11 there is no contact of the substances of the sample with any switching device (crane-switch threads, tap-dispenser, etc ). This dosing volume tube 5 as close as possible to the entrance of the separation chromatographic column 11, which reduces the likelihood of chemical transformations of the analyzed substances on the path from the source of the analyzed compounds in the chromatographic column. Additionally, all the way samples analyzed substances from the source of the analyzed mixture to chromatographic separation column no windproof volumes, which would accumulate substances of the sample. All connecting piping, which could produce these volumes, blown by the flow of carrier gas in the process of transferring samples from the dosing volume 5 in the chromatographic column 11 and in the implementation of chromatographic separation of the analyzed substances in column 11. This increases technostar, in the proposed chromatograph switching the flow of gas in the metering and separation systems is one (Fig. 1 and 2) or two (Fig. 3 - 6) controlled shut-off valves installed in the piping at ambient temperature. This dramatically increases the reliability of the chromatograph.

1. Gas chromatograph for analysis of substances in mixtures of gases and/or vapors containing the source of carrier gas, a device for introducing a metered quantity of the analyzed mixture of substances in a stream of carrier gas, comprising a dosing tube with an internal volume, one end of which is connected to a source of carrier gas through a pipeline for supplying a carrier gas, which has managed the shut-off valve and pipeline for the supply of the sample mixture of substances, chromatographic column, the input of which is connected with the second end of the dosing tube with an internal volume, the pump gas flow, connected to a second end of the dosing tube with an internal volume, and a detector, characterized in that it introduced an additional pipeline for supplying a carrier gas, connecting a source of carrier gas from the outlet of the chromatographic column, and three flow limiter ha is Truboprovod for the supply of the sample mixture of substances, and the third is connected to the pump flow.

2. Chromatograph on p. 1, characterized in that it introduced the second chromatographic column is installed between the first chromatographic column and detector, and operated shut-off valve installed in an additional pipeline for supplying a carrier gas.

3. Chromatograph under item 1 or 2, characterized in that the pump flow is made in the form of a cylindrical tank with installed inside with the possibility of reciprocating movement of the piston rod connected to the drive.

4. Chromatograph on p. 1, or 2, or 3, characterized in that it introduced evaporation chamber to enter into the flow of carrier gas vapor liquid, installed in the pipeline for the supply of carrier gas connected to the dosing tube with internal displacement.

 

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