JPS58202870A - Measurement of trace gas component by gas chromatograph - Google Patents

Abstract

PURPOSE:To enable a highly accurate estimation of trace gas component B by a method wherein a sample gas to containing a trace gas component B in a gas component A flows to first column and immediately before the outflow of the component B, a carrier gas is reversed to the first column and sent to the second column. CONSTITUTION:When first and second columns 2 and 3 are used to analyze a sample gas containing a trace gas component B in a gas component A, first, the sample gas 6 is introduced to the first column to release the component A previously flowing out until the time immediately before the component B is allowed to flow out. Then, a carrier gas is reversed to the column 2 from a tube 8 and introduced to the second column 3 from a pipe 9 so that the peak of the component B following the component A previously flowing is set at the valley 14. This enables clear separation and detection to improve the limit to the estimation of the trace component B to 2ppm from 10ppm.

Description

[Detailed Description of the Invention] The present invention relates to a measurement method capable of quantitatively analyzing trace gas component B contained in gas component A using a gas chromatograph. The method for measuring the species is carried out using a gas chromatograph a as shown in Fig. By momentarily injecting the sample gas f from the inlet e, the sample gas f can be introduced into the separation tube g filled with a selected filler by means of the carrier gas d.

The sample gas f introduced next is expanded by the carrier gas d in the separation tube g, and each component of the sample gas f is moved at different speeds due to differences in adsorption to the filling material. To be separated into each component＼
Then, this separated gas component is detected by a detector, and the detected electric signal emitted from the detector is introduced into the measurement circuit i, whereby qualitative and quantitative analysis of the gas component can be performed using known conventional methods. 3 in the figure is a constant temperature bath,
k is a recorder connected to the measuring circuit i.

However, when using the above-mentioned normal measurement method, the sample gas f
However, when gas component A, which is the main component, contains trace gas component B of PPM order, that is, when gas component A is much larger than trace gas component B, the two components are completely separated. The second one displayed on the recorder k
As is clear from the gas chromad glass shown in Fig. 1, the trace gas component B flows out as a superimposed accumulation behind the gas component A, making quantitative analysis of the trace gas component B impossible. It may be possible to make the separation tube g longer to ensure sufficient separation, but in this case not only would the analysis time become longer, but even this would not result in complete separation; ), the heights of the peaks of both gases are low and the width in the time T direction is large, and with such consideration it is not possible to measure the trace gas component B.

Therefore, in order to eliminate the deficiencies of the above-mentioned conventional method, a means called a pre-cut method has already been implemented.

As shown in Fig. 3, the method is as follows:
After introducing the sample gas f into the separation tube g, a large portion of the gas components flowing out from the separation tube g is transferred to the discharge tube t of the separation tube g.
Just before the trace gas component B begins to flow out together with the gas component, the release pipe t is closed, and the subsequent sample gas shown in m in the same figure flows out. In other words, it is introduced into the second separation tube g'.

By rubbing in this way, the amount of gas component A relative to trace gas component B in the subsequent sample gas m is certainly reduced, and as a result, the analysis efficiency can be improved. However, even in this case, the trace gas components that can be analyzed are If the amount is up to about 10 PPM, and the amount is smaller than the amount of foam, perform the separation test "1" shown in Figure 3, n.

Like a raw gas, the gas chromatograph detects the gas component A.
The trace gas component B is superimposed on the tailing of the gas, making it impossible to measure the same component B correctly.

In addition to the above-mentioned pre-cut method, the backflush method replaces the measurement means already in use.As shown in FIG. gas component B;
The above-mentioned Iryojuku is also a suitable measurement means to be adopted when the gas is mixed with the third gas component C, which has a slow passage speed.
In this case, after introducing the sample gas f into the separation tube g as described above, the trace gas component B flows out from the separation tube g in advance.
When a small amount of gas component A subsequently flows out,
The carrier gas flows in the opposite direction of the separation tube g from the reverse feed path 0, and is placed in the gas chromatograph λ shown at p in FIG.
The residual gas shown on the left side of the dashed line q, that is, a large portion of gas component A and a third portion of gas C, is released from the backflow discharge path r provided on the inlet side of the separation tube g.
Since only the portion shown on the right side of the dashed-dotted line, that is, S in the figure, is introduced into the second separation tube g', the sample gas introduced into the separation tube g' is equal to its trace gas component B. Although it is possible to completely separate gas component A into a small amount and quantitatively analyze component B, it is possible to improve the analysis efficiency by using the bank flush method for special components such as those mentioned above. The present invention was developed in view of the above-mentioned problems, and is only applicable to sample gases having a A part of the backflush method is adopted, but after releasing a large portion of the gas component by the pre-cut method, the backflush method is used without sending the residual gas in the separation tube to the second separation tube. In this way, the residual gas is caused to flow back, and instead of being released, the backflow gas is introduced into the second separation tube. The aim is to make measurements possible.

The present invention will be described in detail with reference to FIG. 5. Like the conventional example, the gas chromatograph (1) is equipped with a first separation tube (2) and a second separation tube (3). )
The sample gas (6) mixed with the carrier gas (5) is introduced into the sample introduction port (4) from the inlet side of the first separation tube (2), but the sample gas (6) mixed with the carrier gas (5) is introduced into the sample introduction port (4). Pipeline (7)
and a carrier gas backflow path (8), which is different from the gas chromatograph described above in that the backflow delivery path (9) provided on the inlet side of the first separation tube (2) is provided with a carrier gas backflow path (8). It is connected to the inlet side of the separation pipe (3).

To fully carry out the present invention using the above gas chromatograph (1), the sample gas (6) consisting of gas components and trace gas component B is placed in the first separation tube (2) as in the conventional example, and the carrier The gas (5) is introduced by quantitatively supplying the gas (5), and the
2) Gas component A flowing out in advance from the discharge pipe (
9).

1: In the gas chromatogram al shown in the figure, the gas component A on the right side of the dashed line I flows out, and the gas component A and trace gas component B on the left side are transferred to the first separation tube (2).
This continues until it is left behind as a residual gas.

That is, a large amount of gas component A is released from the first separation pipe (2), and the release pipe (7) is closed just before the trace gas component B starts to flow out together with gas component A.

Next, a carrier gas is sent from the gas reverse flow passage (8) and is caused to flow in the reverse flow direction of the first separation pipe (2), thereby removing the residual gas from the inlet side of the intermediate pipe (2) through the reverse flow. It is introduced into the second separation tube (3) by means of a delivery tube (9).

Through the above method, the residual gas is brought into a state where the trace gas component B appears on the right side of the almost vertical peak α3 of the gas component A, as shown in the gas chromatogram az in the figure, and the sample The gas passes through the second separation tube (3
), the gas component A and the trace gas component B of the preceding outflow are separated on the recorder, and the analysis results are displayed on the recorder, as shown in Figure 0CA4. This makes it possible to measure the trace gas component B.

As described above, in the present invention, a sample gas (6) containing a gas component A such as argon or oxygen and a trace gas component B such as nitrogen is transferred to the gas chromatograph (1) using a carrier gas (5). The gas component A is introduced into the first separation tube (2) and separated and discharged from the first separation tube (2) in advance,
After the trace gas component B is released until just before it is discharged, the gas components remaining in the first separation tube (2) and the trace gas component B are made to flow back through the second separation tube using a carrier gas. (3) to detect the slightly noble gas component B that flows out after the gas component A flows out from the second separation tube (3), so that the passage speed within the separation tube increases in the sample gas. Even if slow trace gas component B is included, gas component A and trace gas component can be separated, and the quantification limit, which was 10 PPM in conventional methods, can be reduced to 2 PPMt with five times the accuracy. We were able to confirm that it could be quantified.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a gas chromatograph, and Figure 2 shows a gas chromatograph analyzed using the conventional trace gas component measurement method. Figure 3 is a principle explanatory diagram showing the known pre-cut method, Figure 4 is a principle explanatory diagram showing the known pack flush method, and Figure 5 is a trace gas component measuring method according to the present invention. It is a principle explanatory diagram showing the following. +1) -... Gas chromatograph (2)... First separation tube (3)... Second separation tube (5) @... Carrier Gas (6)...Sample gas A...Gas component B...Trace gas component Patent applicant representative Patent attorney Makoto Ifuji

Claims (1)

[Claims] A sample gas containing trace gas component B in gas component A is introduced into a first separation tube of a paper gas chromatograph using a carrier gas, and gas component A is extracted from the first separation tube by one separation. is released until just before the trace gas component B flows out, and then the gas component A and the trace gas component B remaining in the first separation tube are reverse-flowed by a carrier gas to perform a second separation. A method for measuring a trace gas component using a gas chromatograph, characterized in that the trace gas component B is introduced into a second separation tube and flows out after the gas component A flows out from the second separation tube.