JPH029308B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas chromatography analysis method and an apparatus thereof.

When detecting trace components in gases such as gas, air, or inert gas during the air liquefaction separation process, a gas chromatography analyzer like the one shown in Figure 1 has been used until now, and detection has been carried out as follows. I was gone.

That is, first, a sample gas is injected from the sample inlet 1 and sent into the concentrating tube 2 filled with a fixative.
Therefore, the sample gas is fixed in a fixative and concentrated. The concentrating tube 2 is immersed in a cryogen 4 in a cryogen tank 3 to cool the sample gas and hold and fix it in the fixative in that state. Next, after the concentration is completed, the cooling of the concentrating tube 2 by the cryogen 4 is stopped and the concentrating tube 2 is heated appropriately. As a result, the liquefied sample instantaneously evaporates and expands, and a portion of it is discharged from the discharge port 5 as shown by arrow A. In this state, the carrier gas inlet pipe 6 and outlet pipe 7 form a closed circuit via the switching valve 8. After the pressure of the sample gas in the concentrator 2 and the pressure in the gas chromatograph analyzer (not shown) reach equilibrium, push up the switching knob 9 in the direction of arrow B in the figure, as shown in Figure 2. , a carrier gas inlet pipe 6 and an outlet pipe (connected to the gas chromatograph analyzer) 7
are connected to one end 2a and the other end 26 of the concentrating tube 2, respectively, so that the sample gas is sent to the gas chromatography analyzer by the carrier gas and analyzed. In this way, trace components in the sample gas were detected.

However, in this case, when the retention time of the trace component in the sample gas is close to the retention time of the main component gas that occupies most of the sample gas,
During gas chromatography analysis, trace components could not be detected because their peaks were hidden by the main component gas. In order to avoid this, the column of the gas chromato analyzer (filled with packing material) should be changed to a column that can expand the difference between the retention time of the main component gas and the retention time of the trace component. Instead, the peaks of trace components and the peaks of main component gases are separated. However, in this case, although it is possible to separate the peaks of trace components, the retention time of each component in the sample gas increases, making the peaks of each component lower, losing their sharpness, and making it difficult to confirm them. , and the analysis required a long time. Conventionally, after the completion of concentration, the high pressure of vaporization expansion of the concentrated liquefied sample caused by stopping cooling with the cryogen 4 and heating is reduced by discharging a part of the concentrated sample gas from the discharge port 5. After the pressure in the concentrating tube 2 and the pressure in the gas chromato analyzer reached equilibrium, the concentrated sample gas was sent to the gas chromato analyzer. Therefore, there was a risk that analysis errors would occur. In addition, it is troublesome to check whether the pressure has reached equilibrium and to adjust the pressure to equilibrium, and if the pressure is incorrectly adjusted and the high-pressure concentrated sample gas is sent to the gas chromatograph analyzer, the There was also the problem that the pressure exceeded the maximum working pressure of the analyzer, creating a dangerous situation.

This invention was made to solve all of these problems.A sample containing trace components is sent to a concentrator filled with a fixative, concentrated and held by the fixative, and a carrier gas is transferred into the concentrator. By supplying this concentrated sample, it is desorbed from the fixative and sent into a separation tube, and each component in the concentrated sample is separated and sequentially eluted using this separation tube, and this eluted component is detected by a detector. This is a gas chromatography analysis method in which the purified gas is cooled with a cryogen through a purified gas purification pipe filled with a fixative and cooled with a cryogen before supplying the carrier gas to the concentrator. The first gist is a gas chromatographic analysis method that is characterized by removing interfering components in the concentrated sample that interfere with the detection of the target component by desorbing it from a fixative by supplying it to a concentrator that is A gas chromatograph equipped with a concentrator that concentrates the sample, a separation tube that separates and sequentially elutes each component in the concentrated sample concentrated by the concentrator, and a detector that detects the components eluted from the separation tube. In the analyzer, a first cryogen tank that cools the concentrator, a purified gas supply source, a purified gas purifier that purifies the purified gas supplied from the purified gas supply source, and a purified gas purifier that cools the purified gas purifier. A gas chromatograph further comprising: a second cryogen tank, a supply pipe for supplying the purified gas purified by the purified gas purifier to the concentrator, and an on-off valve for opening and closing the supply pipe. The second gist is the analysis device.

That is, the present invention provides a purified gas supply source, a purified gas purifier that purifies the purified gas supplied from the purified gas supply source, and a purified gas purified by the purified gas purifier that supplies the purified gas to the concentrator. Using a gas chromatography analyzer equipped with a concentrator, which is equipped with a supply pipe and an on-off valve for the supply pipe, purification gas is supplied into the concentrator before the carrier gas is supplied into the concentrator, and the target components (usually trace components) are ) It removes interfering components in the sample that interfere with detection.

Next, this invention will be explained in detail.

This invention uses a purifying gas to desorb and remove interfering components that interfere with the detection of target components from a sample held and fixed in a concentrated state in a fixative of a concentrator, and then the remaining components are removed using a carrier gas. The target component is then separated into each component by being separated from the fixative and sent into a separation tube, and then sent to a detector to detect the target component. For example, when detecting carbon dioxide and methane in the air using a gas chromatography analyzer using conventional methods,
The peaks of carbon dioxide and methane, which are trace components, are hidden by the peak of air, which is the main component, and are impossible to detect. However, in such cases, if the air is removed from the sample in the concentrator using purified gas in advance and the remaining components are separated and detected, carbon dioxide and methane can be detected quickly and accurately. , and can be easily detected. Usually, the same type of gas as the carrier gas is used as the purifying gas. This is because if a purifying gas different from the carrier gas is used, its components may be retained in the fixative of the concentrator, which may impede detection of trace components or impair accuracy.

In order to desorb and remove only the interfering components from the fixative in the concentrator using purified gas, select a fixative that has a small holding power for the interfering components and a large holding power for other components. be able to. Further, it is also possible to desorb and remove only the interfering components from the fixative by utilizing the difference between the holding power of the fixative for the interfering components and the retaining power for other components at a certain temperature. In this case, the concentrator is usually cooled with a cryogen, and the difference in the holding power of the fixative for interfering components and other components at low temperatures is utilized.

According to the present invention, a large amount of interfering components are present in the sample gas, which appear as large peaks during gas chromatography analysis, and the target component (usually a trace component) is If the target component is hidden in a peak, the target component is detected after removing a large amount of interfering components with purification gas, making it possible to detect the target component with high accuracy and ease. . In addition, unlike conventional methods, there is no need to use a column that expands the peaks of the interfering component and the target component (increasing the retention time difference), so analysis time does not become long, and a large number of target components can be detected. The peak also appears sharp, making it easier to confirm. Furthermore, when interfering components are present in large quantities in the sample, they are removed by the purifying gas prior to gas chromatography analysis, so the pressure in the concentrator does not increase as much, and therefore the concentration inside the concentrator is reduced. There is no need to adjust the pressure inside the gas chromato analyzer. Moreover, the pressure inside the gas chromato analyzer does not exceed the maximum operating pressure, making it safe.

Next, an example of an analyzer that implements the gas chromatographic analysis method of the present invention will be described.

That is, as shown in FIG. 3, this analyzer is a known gas chromatography analyzer equipped with a concentrating tube 2 with a switching pot 9, and a switching device with a purified gas purification tube 10, a purified gas cylinder 11, and a switching pot 12. The valve 13 is further installed, and by operating the switching knob 12, the purified gas in the purified gas cylinder 11 is sent to the purified gas purification pipe 10 as shown by the arrow for purification, and then sent to the concentration pipe 2 via the switching valve 13 as shown by the arrow. I'm starting to send it. As mentioned above, this concentrating tube 2 is filled with the packing material used in ordinary gas chromatography analysis columns as a fixing agent, and is cooled by the cryogen 4 in the cryogen tank 3. There is. This cryogen tank 3 is movable,
The cooling of the concentrating tube 2 is stopped at a desired time. Furthermore, the purified gas purification pipe 10 is also filled with a filler and is cooled by the cryogen 15 in the cryogen tank 14.

To detect and quantify trace components coexisting with interfering components using this device, as shown in Figure 4,
First, operate the switching knob 12 to connect the purified gas cylinder 1.
The purified gas in 1 is sent to a concentrating tube 2 via a purified gas purification tube 10, and then released from a discharge port 5. By doing this, the purified gas has impurities removed in the purified gas purification tube 10 which is cooled by the cryogen 15, becomes almost pure, and is sent into the concentrating tube 2. 2
Clean inside. By continuing this state for several minutes, the inside of the concentrating tube 2 is purified. Usually, He gas is used as the purification gas, liquefied nitrogen is used as the cryogen 15, and molecular sieves are used as the filler in the purification gas purification pipe 10.

Next, from the state shown in FIG. 4, the concentrator 2 is gradually immersed in the cryogen 4 as shown in FIG. 5 to be cooled. In this case, if the concentrating tube 2 is suddenly immersed, the purified gas will no longer flow, so air will flow into the concentrating tube 2 from the discharge port 5.
into the interior and contaminate it. Next, with the concentrating tube 2 immersed in the cryogen 4, the switching knob 12 is operated to bring it into the state shown in the figure, and the sample is injected from the sample inlet 16 and sent into the concentrating tube 2 to be concentrated. By operating this switching knob 12, the purified gas cylinder 1
The purifying gas in 1 is released from the purifying gas discharge port 17. After concentrating a certain amount of the sample in this way, the switching pot 12 is immediately returned to its original state. As a result, as shown in FIG. 6, purified purified gas flows into the concentrating tube 2, desorbs interfering components held by the fixative in the concentrating tube 2, and is discharged from the discharge port 5. If this state continues for several minutes, most of the interfering components will be expelled, leaving a trace amount of components.

Next, in place of the cryogen tank 3 that used to cool the concentrating tube 2, a hot water tank 18 is arranged as shown in FIG. 7, and the concentrating tube 2 is immersed in hot water 19 to warm it. Simultaneously with this heating, the switching knob 9 is operated to flow the carrier gas from the carrier gas inlet pipe 6 into the concentrating tube 2, whereby trace components are separated from the fixative and sent to the gas chromatography analyzer. As a result, trace components are analyzed by a gas chromatography analyzer.

In this way, interfering components can be removed and only trace components can be easily separated and detected.

In the above description, manual switching tabs 9 and 12 are used, but electromagnetic valves may be used to automatically switch the switching tabs 9 and 12. Further, the type of the kettle may be a two-way valve or a multi-way valve.

As described above, according to this device, when a sample contains a large amount of interfering components, it is possible to separate trace components.
Even in cases where detection is difficult, interfering components can be removed and trace components can be easily separated and detected. In addition, this device removes interfering components in advance,
Since only trace components are sent to the separation tube and detector for separation and detection, unlike conventional methods, a large amount of interfering component gas is added to the carrier gas, and separation and detection are performed in that state.
The baseline of the gas chromatogram does not change due to detection.

In addition, since the purified gas for removing interfering components is purified and used in a state free of impurities, when the interfering components are removed by the purified gas, the impurities in the purified gas are fixed on the fixative, which is then used for analysis. There will be no such situation. In particular, by purifying and using a low-cost purification gas that contains some impurities, it becomes cheaper and easier to obtain than when using expensive pure gas as the purification gas.

Next, the following sample was analyzed using the gas chromatography apparatus shown in FIG. Details of the concentrating tube of the gas chromatometry device, the gas chromatograph analyzer, and measurement conditions in this case are shown below.

[Concentration tube]

Concentration tube: 6φ x 4φ x 300mm Fixing agent: Firebrick powder (60 to 80 mesh) Concentrating cryogen: Liquefied oxygen Purified gas: He, 50ml/min Purified gas purification tube: 6φ x 4φ x 1m Filling agent: Molekyu Rahshibus 5A (60~80
Cryogen for purified gas purification: Liquefied nitrogen [Gas chromatography analyzer] Column: Holapack T x 1m Constant temperature chamber: 80℃ Detector: 80℃ Carrier gas: He, 30ml/min Thermal conductivity detector (TCD): Bridge current 140mA Hydrogen flame detector (FID): Hydrogen gas 30ml/min: Air gas 900ml/min Recorder: Sensitivity 1mV x 1/1 Pen speed 30cm width/sec Z pen type (channel 1TCD, channel 2FID) Recording paper advance 1cm/min [Analysis example 1: Measurement of hydrocarbons and carbon dioxide in liquefied oxygen] Vaporize liquefied oxygen to create a vaporized gas sample,
100ml of this was sampled and analyzed by gas chromatography. In this case, the sensitivity of TCD is 1/1, the FID is 1/20,
I set it to 1/1. The results are shown in FIG. In the figure, curve A is a gas chromatogram by FID, and curve B is a gas chromatogram by TCD. In curve A, peak a is
CH ₄ , peak b is the shock when the sensitivity is switched from 1/20 to 1/2, peak c is the peak of C ₂ H ₆ , and peak d is the peak of C ₃ H ₈ . Further, in curve B, peak e is air and peak f is _CO2 . From these results, CH ₄ is about 100 p.pm, and C ₂ H ₆ is
It was quantified as 0.02ppm, C ₃ H ₈ as 0.01ppm, and Co ₂ as less than 1p.pm. In this case, the CO ₂ peak, which would be hidden by the air peak in conventional gas chromatography, was clearly detected.

[Analysis Example 2: Measurement of methane in argon] 100 ml of argon was collected and analyzed by gas chromatography. In this case, the sensitivities of TCD and FID were each set to 1/1. The results are shown in FIG. In the figure, curve C is a gas chromatogram by FID, and curve D is a gas chromatogram by TCD. In curve C, peak g
is the CH ₄ peak. In curve D, h is the air peak. From these results, CH ₄ is
It was determined to be 0.04ppm. When CO ₂ is present, its peak appears adjacent to the left side of the air peak, but this time no CO ₂ was observed.

[Analysis Example 3: Measurement of methane and carbon dioxide gas in air] 40 ml of air was sampled and analyzed by gas chromatography.

In this case, the sensitivity of TCD was set to 1/2, and the sensitivity of FID was set to 1/1. The results are shown in FIG. In the figure, curve E is a gas chromatogram by FID, and curve F is a gas chromatogram by TCD. In curve E, peak i is
is the peak of _CH4 , and in curve F, peak j
is the injection shock, peak k is air, and peak l is
This is the peak of _CO2 . From these results, CO ₂ is approximately
250 p.pm, and CH ₄ was determined to be approximately 1 p.pm.

[Analysis Example 4: Measurement of hydrocarbons and carbon dioxide in contaminated air] 40 ml of contaminated air was sampled and analyzed by gas chromatography. In this case, the sensitivities of TCD and FID were each set to 1/1. The result is the first
Shown in Figure 1. In the figure, curve G is a gas chromatogram by FID, and curve H is a gas chromatogram by TCD. In curve G, peak m is a CH ₄ peak, and peak n is a C ₂ H ₆ peak.
Furthermore, in curve H, peak o is the air peak, and peak p is the peak of _CO2 . As a result, CH ₄ is about 1 p.pm, C ₂ H ₆ is about 0.9 ppm, and CO ₂ is about 300 p.pm.
was quantified. In this case, the CO ₂ peak was completely separated from the air peak and clearly appeared.

[Comparative example: Measurement of hydrocarbons and carbon dioxide gas in contaminated air]

Using 40ml of contaminated air used in analysis example 4 as a sample,
Gas chromatographic analysis was performed in a conventional manner using conventional equipment. The results are shown in FIG. In the figure, the curve is a gas chromatogram by FID, and the curve J is a gas chromatogram by TCD. In the curve, peak q is a CH ₄ peak, and peak r is a C ₂ H ₆ peak. In curve J, peak s is the peak of air. These results
CH ₄ was determined to be about 1 p.pm, and C ₂ H ₆ was determined to be about 1.3 ppm. However, since the CO ₂ peak overlaps with the air peak s, it could not be detected or quantified.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are explanatory diagrams each explaining the drawbacks of the conventional example, FIG. 3 is a configuration diagram of an example of the gas chromatography analyzer of the present invention, and FIGS. 4 to 7 are explanatory diagrams, respectively, of its operating state. , Figures 8 to 11 are analysis example 1 using the apparatus shown in Figure 3, respectively.
Charts 4 to 4 and FIG. 12 are charts of comparative examples. 2...Concentration tube, 3...Cryogen tank, 4...Cryogen,
8, 13...Switching valve, 9,12...Switching valve,
10...Purified gas purification pipe, 11...Purified gas cylinder.

Claims (1)

[Scope of Claims] 1. A sample containing trace components is sent into a concentrator filled with a fixative, concentrated and held by the fixative, and a carrier gas is supplied into the concentrator, so that the concentrated sample is filled with a fixative. This is a gas chromatography analysis method in which the carrier gas is desorbed from the carrier gas and sent into a separation tube, and each component in the concentrated sample is separated and sequentially eluted using the separation tube, and the eluted components are detected by a detector. Before supplying the purified gas to the container, the purified gas is passed through the purified gas purification pipe, which is filled with a fixative and cooled with a cryogen, and then fed into the concentrator, which is cooled with a cryogen, to extract the target components. A gas chromatography analysis method characterized by removing interfering components in a concentrated sample that interfere with detection by detaching them from a fixative. 2. Equipped with a concentrator to concentrate the sample, a separation tube to separate and sequentially elute each component in the concentrated sample concentrated by the concentrator, and a detector to detect the components eluted from the separation tube. In the gas chromatography analyzer, a first cryogen tank that cools the concentrator, a purified gas supply source, a purified gas purifier that purifies the purified gas supplied from the purified gas supply source, and the purified gas purifier The method further includes a second cryogen tank for cooling the purified gas, a supply pipe for supplying the purified gas purified by the purified gas purifier to the concentrator, and an on-off valve for opening and closing the supply pipe. Gas chromatography analyzer.