JPH11337525A - Gas analysis system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To equalize measurement conditions at the time of reference gas analysis for obtaining a correction coefficient to measurement conditions at the time of sample gas analysis, in a gas analysis system comprising a gas chromatograph and a mass spectrometer. SOLUTION: A carrier gas is sent with a fixed flow rate in a column 24. A reference gas or sample gas is introduced together with the carrier gas into the column 24. Gas is discharged selectively at the timing corresponding to the kind of gas from the column 24. Noted gas is introduced into a mass spectrometer 12 and mass spectrometry is executed. At that time, the gas quantity to be introduced is controlled by an introduction quantity controller 30. Besides, the ratio of the carrier gas to the noted gas in the gas to be introduced into the mass spectrometer 12 is controlled by supplementation of the carrier gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas analysis system, and more particularly, to a gas analysis system provided with a gas chromatograph and a mass spectrometer.

[0002]

2. Description of the Related Art According to recent studies on Helicobacter pylori (hereinafter, H. pylori), a stomach-carrying bacterium,
It has been pointed out that it may cause gastric ulcer and the like. Various attempts have been made to detect and quantify H. pylori.
One of them uses breath analysis. In this method, a urea reagent labeled with ¹³ C is orally administered to a patient, and the concentration ratio of ¹³ CO ₂ to ¹² CO ₂ (using the fact that ¹³ CO ₂ decomposed and generated by H. pylori appears in breath) is used. Isotope ratio)
To indirectly quantify H. pylori.

[0003] Exhaled air contains a large amount of CO ₂ , and a certain amount of ¹³ C isotope of ¹² C is present in nature. Quantifying ¹³ CO ₂ produced by H. pylori under such conditions requires a highly accurate measurement.

Conventionally, a system utilizing a gas chromatograph and a mass spectrometer has been used to measure such a concentration ratio. In such a system, a sample gas is introduced into the gas chromatograph together with a carrier gas. In a gas chromatograph, the retention time differs depending on the gas type, and as a result, each gas is discharged with a time lag for each gas type. Of the exhaust gas, CO ₂ gas is introduced into the mass spectrometer and the individual amounts or ratios of ¹³ C and ¹² C are measured for the sample gas. Meanwhile, the gas component and the ¹³ CO ^_2/12 CO ₂ isotope ratios known standard gas is also treated in the same manner as described above, individual amounts or ratios of ¹³ C and ¹² C are measured. The measurement result is used for correcting the measurement result of the sample gas.

[0005]

If a magnetic field type mass spectrometer is used as the above mass spectrometer, high sensitivity and high precision measurement can be expected, but the operation requires skill and the system cost increases. On the other hand, a quadrupole mass spectrometer, for example, has the advantage of simple operation and low cost. However, according to the experiments of the present invention, even if the gases have the same composition, the ionization efficiency is different if the introduced gas amount (gas pressure) or the gas component ratio (the ratio of the carrier gas to the CO ₂ gas) is different. Problem. That is, there is a problem that even if the same gas is used, the analysis result is different if the measurement conditions are different.

[0006] For this reason, various methods such as a method of cooling exhaled air and extracting only CO ₂ can be combined, but applying any of these methods increases the equipment cost and complicates the operation. There's a problem. The above problem can be pointed out even when a mass spectrometer other than the quadrupole mass spectrometer is used, and the same problem can be pointed out in analysis other than the breath analysis.

[0007] The present invention has been made in view of the above-mentioned conventional problems, and has as its object to perform gas analysis with a simple configuration and with high accuracy.

Another object of the present invention is to prevent a decrease in measurement accuracy due to a difference in gas pressure or gas component ratio in gas analysis using a gas chromatograph and a mass spectrometer.

[0009]

To achieve the above object, the present invention provides a gas chromatograph in which a sample gas containing a gas of interest is introduced together with a carrier gas, and the gas chromatograph selectively discharges the gas of interest. An exhaust gas discharged from the exhaust gas is introduced, and a gas analyzer for analyzing the gas of interest, and a gas analyzer for controlling the ratio of the gas of interest and the carrier gas in the exhaust gas to a predetermined value. And a replenishing means for replenishing the carrier gas, wherein an exhaust gas having a predetermined gas ratio is introduced into the gas analyzer.

According to the above configuration, the gas of interest (analysis gas) is selectively discharged from the sample gas in the gas chromatograph with time. In that case, the carrier gas is also constantly discharged. Therefore, the gas of interest is introduced into a gas analyzer (for example, a mass analyzer) together with the carrier gas,
At that time, the replenishing means replenishes the carrier gas, and the ratio between the gas amount of interest and the gas amount of the carrier gas is controlled to a predetermined value. That is, since the gas analysis conditions can be controlled to be constant by adjusting the ratio of the gas introduced into the gas analyzer, highly accurate measurement can be realized. For example, even if the amount of sample gas introduced into the gas chromatograph is constant, the proportion (amount) of the gas of interest in the sample gas varies. On the other hand, according to the present invention, the ratio between the gas of interest and the carrier gas can be adjusted prior to the gas analysis as described above.

In a preferred aspect of the present invention, the gas analyzer includes an introduction amount adjusting means for controlling a flow rate of the exhaust gas introduced into the gas analyzer to a constant value. Exhaust gas with a pressure is introduced.

As described above, by controlling not only the gas ratio but also the gas amount to a predetermined value, the conditions at the time of gas analysis can be fixed at all times, and more accurate analysis can be performed. In particular, if the measurement conditions can be the same between when measuring the standard gas and when measuring the sample gas, the analysis result of the target gas can be corrected with high accuracy.

In a preferred aspect of the present invention, based on the amount of the reference gas previously discharged from the gas chromatograph,
An estimating operation unit for estimating the amount of the gas of interest discharged thereafter, and a replenishing amount control means for controlling a replenishing amount of the carrier gas based on the estimated amount of the gas of interest.

In determining the replenishment amount of the carrier gas,
If possible, it is desirable to refer to the amount of the target gas itself. However, if it is difficult, the amount of some gas (reference gas) discharged prior to the target gas can be referred to. That is, the amount of the gas of interest in the sample gas can be estimated from, for example, the entire amount of the other gas, or based on any one of the gas amounts if the component ratio of each gas other than the gas of interest is known. It can be estimated.
Alternatively, the amount of each gas at the time of analyzing the standard gas may be further considered as described later. The replenishment amount of the carrier gas is determined based on the estimated amount of the gas of interest.

In a preferred aspect of the present invention, a sample gas analysis mode for analyzing a gas of interest in the sample gas;
A standard gas analysis mode for analyzing a standard gas having a known gas component by the same analysis processing as that for the sample gas in order to correct the result of the gas analysis of interest, and a preceding discharge from the gas chromatograph in the standard gas analysis mode. The amount β of the reference gas to be discharged and the amount α of the gas of interest subsequently discharged, and the amount β ′ of the reference gas previously discharged from the gas chromatograph in the sample gas analysis mode.
And an estimating operation unit for estimating the amount α ′ of the gas of interest discharged after the discharge of the reference gas in the sample gas analysis mode, based on the estimated amount α ′ of the gas of interest. Replenishing amount control means for controlling the replenishing amount of the carrier gas.

The standard gas is a reference gas having a gas component similar to that of the sample gas and having a known ratio of each gas. According to the above configuration, the correction coefficient is obtained using the standard gas. At this time, the amount β of the reference gas discharged from the gas chromatograph and the amount α of the gas of interest are detected. The target gas amount α ′ is estimated based on β and α and the reference gas amount β ′ during sample gas analysis, and the carrier gas replenishment amount is determined using the target gas amount α ′.

In a preferred aspect of the present invention, in the sample gas analysis mode and the standard gas analysis mode, a gas ratio of a carrier gas and a target gas in the exhaust gas introduced into the gas analyzer and a gas of the exhaust gas The quantities are made equal. Thus, the conditions for measuring the sample gas and the conditions for measuring the standard gas can be made the same, so that the correction coefficient can be obtained with high accuracy.

[0018] In a preferred aspect of the present invention, there is provided a correction means for correcting the target gas analysis result in the sample gas analysis mode using the analysis result in the standard gas analysis mode. Here, the correction means corrects the target gas analysis result using the above-described correction coefficient.

In a preferred aspect of the present invention, the apparatus includes a replenishing amount control means for controlling a replenishing amount of the carrier gas based on an amount of the gas of interest discharged from the gas chromatograph. For example, if there is a time margin between the timing at which the gas of interest is discharged from the gas chromatograph and the timing at which the gas of interest is introduced into the gas analyzer, the amount of the gas of interest itself is reduced as in the above configuration. The replenishment amount of the carrier gas may be adjusted based on this.

Preferably, the sample gas is exhaled gas, and the gas of interest is CO ₂ . Also, preferably,
The gas analyzer is a device for measuring the isotope ratio of ¹² CO ₂ and ¹³ CO ₂ . In this case, a mass spectrometer or an isotope ratio measuring device is used as the gas analyzer.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a preferred embodiment of a gas analysis system according to the present invention, and FIG. 1 is a conceptual diagram showing the entire configuration. This gas analysis system is a system that measures the isotope ratio of CO ₂ in breath.
Based on the magnitude of the isotope ratio, for example, the above-mentioned H. pylori quantification can be performed.

The gas analysis system shown in FIG. 1 is roughly divided into a gas chromatograph 10, a mass spectrometer 12,
It is composed of a calculation unit 14, a control unit 16, and a display unit 20.

The gas chromatograph 10 has a column 24 for selectively discharging the introduced gas for each component. When gas is introduced into the column 24, each gas is discharged from the column 24 after a lapse of a retention time corresponding to the type of each gas.

The carrier gas generator 22 is connected to the main gas passage 2
This is an apparatus for flowing a carrier gas at a constant flow rate with respect to 00. For example, He is used as the carrier gas. This carrier gas is introduced into the mass spectrometer 12 through the column 24.

A sample gas or a standard gas is introduced into the column 24 together with the carrier gas. here,
The sample gas is accommodated in the sample gas supply device 23B. The sample gas is exhaled air collected from the subject. A urea reagent labeled in advance with ¹³ C is orally administered to the subject, and exhaled air is collected from the subject after a lapse of a predetermined period after the administration. The exhaled air is stored in the sample gas supply device 23B.

When H. pylori is present in the stomach of the subject, urea is decomposed into CO ₂ by the urease activity of the H. pylori. Therefore, if labeled with the urea in ¹³ C, it is possible from the amount or isotope ratio ¹³ CO ^_2/12 CO ₂ of ¹³ CO ₂ contained in the breath perform quantification of H. pylori.

The standard gas is a reference gas having a component substantially equal to that of exhaled air. This standard gas is stored in the standard gas supply unit 23A. The composition of the standard gas, e.g. _{N 2: 79%, O 2} : 17%, Ar: 1%, CO 2: 3
%. Of course, the CO ₂ isotope ratio is the natural isotope ratio or is known. This standard gas is a gas used to correct the analysis result of the sample gas in the mass spectrometer 12.

In the gas chromatograph 10, an output detector 26 is provided downstream of the column 24. The output detector 26 is a device that detects the amount of gas other than the carrier gas in the gas discharged from the column 24. Of course, the control unit 16 that receives the output signal from the output detector 26 may exclude the signal component corresponding to the carrier gas included in the output signal by calculation.

In the system according to the present embodiment, a carrier gas replenishment path 202 is formed so as to bypass the column 24. That is, the carrier gas generator 22 and the subsequent stage of the output detector 26 are connected, and the amount of the carrier gas contained in the gas introduced into the latter stage of the column 24, that is, the preceding stage of the mass spectrometer 12 is adjusted. It is possible. The control of the replenishment amount is performed by the control unit 16.

The introduction amount adjuster 30 is a device for adjusting the amount of gas introduced into the mass spectrometer 12. In the present embodiment, the introduction amount adjuster 30 is connected to the gas flow meter 11.
6 and a leak valve 118. This introduction amount adjuster 30 is controlled by the control unit 16.

As shown in FIG. 1, the main gas passage 200
Is provided with an electromagnetic valve V1 and a gas flow meter 110, while the carrier gas replenishment path 202 is provided with an electromagnetic valve V1.
2 and a gas flow meter 114 are provided. The electromagnetic valves V1 and V2 are controlled by the control unit 16, and the flow rate values detected by the gas flow meters 110 and 114 are sent to the control unit 16.

In the present embodiment, the mass spectrometer 12
It is a quadrupole mass spectrometer. As described above, this analyzer has the property that the analysis accuracy changes in accordance with the amount of gas introduced and the ratio of gas components. Therefore, in the system according to the present embodiment, the above-described carrier gas replenishment path 202 is provided to adjust the ratio between the carrier gas and the CO ₂ to be analyzed, and the above-described system is used to adjust the amount of the introduced gas. The introduction amount adjuster 30 is provided.

As the mass spectrometer 12, an analyzer other than those described above can be used. Even in this case, high-precision measurement can be realized by replenishing the carrier gas and adjusting the introduction amount. is there.

In the mass spectrometer 12, ¹³ CO ₂ and ¹²
To measure the isotope ratio of CO ₂ ,
Is measured, and the measurement result is sent to the calculation unit 14. In the calculation unit 14, the isotope ratio ¹³ CO
Performs an operation of _^2/12 CO _2, it has sent the result to the display unit 20.

The memory 17 stores the value of each peak, which will be described later, as a parameter for determining the replenishment amount of the carrier gas. The memory 18 stores correction parameters described later.

Next, the operation of the system shown in FIG. 1 will be described with reference to FIGS.

In the operation of this system, the standard gas analysis mode is executed first, and then the sample gas analysis mode is executed.

In S101 shown in FIG. 3, the electromagnetic valve V1 is controlled by the control unit 16 and the carrier gas generator 22 is controlled.
, A constant flow rate of the carrier gas is introduced into the main gas passage 200. The flow rate of the carrier gas at that time is monitored by the gas flow meter 110. Here, the flow rate F _{1 of the} carrier gas is fixed, that is, a constant flow rate of the carrier gas is always introduced into the column 24.

In S102, the standard gas supply unit 23A is driven by the operation of the control unit 16 or by an artificial operation, whereby a predetermined amount (for example, 1 cc) of the standard gas is introduced into the main gas passage 200. Then, the standard gas is introduced into the column 24, and each gas is separated for each type of gas by the operation of the column 24, and selectively discharged.

FIG. 2A shows the result of detection by the output detector 26 in the standard gas analysis mode. In each graph in FIG. 2, a signal component corresponding to the carrier gas is not shown. Due to the difference in retention time in the column 24, each gas constituting the standard gas is discharged from the column 24 at different timings according to the type. In the present embodiment, a packed column of Polapack Q (trade name) is used as the column 24. When such a filler is used, as shown in FIG.
First, a peak (reference peak) corresponding to each of N ₂ , O ₂ , and Ar gas appears, and after several to several tens of seconds from the peak, CO 2
_Two gas peaks will appear. Of course, if another filler is used, other waveforms will be obtained, but the present invention can be applied to such a case.

Returning to FIG. 3, in step S103, the level β of the reference peak shown in FIG. 2 is detected. This will be detected by the output detector 26. In S105, the level α of the CO ₂ peak is detected by the output detector 26. Such peak prior to detection or in parallel therewith, replenishment carrier gas is passed through the carrier gas replenishment passage 202 in S104 at a constant flow rate F _2, it is replenished to the exhaust gas from the column 24. Incidentally, in the standard gas analysis mode, it is not always necessary to use the supplementary carrier gas.

In S106, CO ₂ gas is introduced into the mass spectrometer 12 together with the carrier gas (including the supplementary carrier gas). Prior to this, the amount of gas to be introduced is adjusted to a predetermined value A in the introduction amount adjuster 30. The partial pressure ratio B between the carrier gas and the CO ₂ gas in the introduced gas is also adjusted to a predetermined value by replenishment of the above-mentioned replenishment carrier gas.

[0044] In the mass spectrometer 12 to measure the ion current value for mass numbers 45 and 45 as described above, ¹³ CO
The respective amounts of ₂ and ¹² CO ₂ are measured. The measurement results are sent to the arithmetic unit 14, in the operation unit 14 isotope ratio ¹³ CO ^_2/12 CO ₂ is calculated. Then, in S107, the calculation unit 14 calculates the correction parameter C by dividing the actually measured isotope ratio by the known isotope ratio obtained in advance. The correction parameters are stored in the memory 18. Incidentally, various formulas can be applied as the calculation formula of the correction parameter C.

Each of the above steps is executed in the standard gas analysis mode, and after the execution of the mode is completed, the sample gas analysis mode described below is executed.

[0046] In S108, in the state in which the carrier gas in the main gas passage 200 is flowed at a constant flow rate F _1,
A fixed amount of sample gas is introduced into the main gas passage 200 using the sample gas supply device 23B. Here, the introduction amount of the sample gas is the same as the introduction amount of the standard gas described above.

In S109, the sample gas is separated for each component in the column 24.

FIG. 2B shows the output flow level detected by the output detector 26 in such a sample gas analysis mode. As shown, as in the case of the standard gas, a reference peak appears first, and then CO 2
_Two peaks appear. Here, the level of the reference peak is β ′, and the level of the CO ₂ peak is α ′.

Returning to FIG. 3, in S109, FIG.
Has been detected in advance. Then, in subsequent S110, the level α ′ of the CO ₂ peak that appears following the reference peak is predicted. Specifically, α ′ is estimated based on α, β, and β ′. Here, to explain this, since the amounts of the standard gas and the sample gas introduced are the same, first, the following (1)
An equation is derived.

Α + β = α ′ + β ′ (1) Therefore, by modifying the expression (1), α ′ can be predicted.

Α ′ = α + β−β ′ (2) As described above, α ′ is predicted in S110 by setting the replenishment amount of the replenishment carrier gas before the CO ₂ peak actually appears. According to such control, it is possible to directly guide the CO ₂ gas to the mass spectrometer 12 with appropriate replenishment of the carrier gas when the CO ₂ gas appears at the output of the column 24. .

Therefore, in S111, the flow rate F ₂ ′ of the supplementary carrier gas is determined using the predicted α ′. Here, this will be described below.

In order to accurately perform correction using the standard gas, it is necessary to make the measurement conditions in the mass spectrometer 12 the same both when analyzing the standard gas and when analyzing the sample gas. The amount of gas introduced into the mass spectrometer 12 is controlled by the introduction amount regulator 30, but the gas partial pressure ratio of the introduced gas is adjusted by replenishing the carrier gas.

The condition that the gas partial pressure ratio is the same for the standard gas and the sample gas can be expressed by the following equation (3).

Α / (F ₁ + F ₂ ) = α ′ / (F ₁ + F ₂ ′) (3) In the above equation (3), α ′ estimated in S110 (see equation (2)) By substituting, the following equation (4) can be derived.

F ₂ ′ = ((α + β−β ′) / α) × (F ₁ + F ₂ ) −F ₁ (4) That is, in S111, the carrier gas is replenished in accordance with the equation (4). The flow rate F ₂ ′ is determined.

Returning to FIG. 3, in S112, after the appropriate replenishment of the carrier gas is performed as described above,
_Two gases are introduced into the mass spectrometer 12 together with the carrier gas, and the isotope ratio is measured. In this case, S11
The measurement conditions in 2 and the measurement conditions in S106 are the same, that is, the same measurement conditions are constructed on both sides of the gas amount and the gas partial pressure ratio.

In S113, the isotope ratio obtained in S112 is corrected using the correction parameter C calculated in S107. In this case, since the measurement conditions are the same in determining the correction parameter C, the accuracy of the correction using the correction parameter C can be extremely increased.

According to the gas analysis method of the present invention as described above, the isotope ratio of ¹³ CO ₂ and ¹² CO ₂ contained in breath can be measured with high accuracy. Can be accurately determined.

Incidentally, in the above embodiment, FIG.
As described above, the replenishment amount of the carrier gas is determined using the peak of the output flow rate. However, the replenishment amount may be determined using, for example, an integrated value near the peak.
Further, in the above embodiment, gases such as N ₂ and O ₂ are simultaneously discharged from the column 24, thereby obtaining a lump of reference peaks. However, even when those peaks appear at different times, The present invention is applicable. In that case, the replenishment amount of the carrier gas may be determined by the same calculation method using all or a part of those peaks.

The replenishment of the carrier gas is also useful, for example, when only the sample gas analysis mode is executed, and the measurement conditions in the mass spectrometer 12 can be kept constant.

Although actual breath contains moisture,
In the column 24 used in the above embodiment, H ₂ O
Is separated a few minutes after the CO ₂ is separated, so that there is almost no effect on the actual measurement. However, when exhaled air is introduced into the gas chromatograph 10, the exhaled air may be passed through a desiccant or the like to remove moisture.

In the above embodiment, the measurement of the isotope ratio of CO ₂ is performed, but the present invention can be applied to other gas analysis.

In the above embodiment, as shown in FIG. 2, the CO ₂ peak of the sample gas was estimated based on a plurality of other peaks. In a case where the route to the path is long and has a margin in time, the replenishing amount of the carrier gas may be determined based on the CO ₂ peak itself of the sample gas. That is, at least when the CO ₂ gas is introduced into the mass spectrometer 12, the gas partial pressure value is set to a predetermined value.

In the above embodiment, an inexpensive and small quadrupole mass spectrometer is used as the mass spectrometer 12, but another mass spectrometer such as a magnetic field mass spectrometer may be used.

[0066]

As described above, according to the present invention,
Gas analysis can be performed with a simple configuration and with high accuracy. Further, according to the present invention, in gas analysis using a gas chromatograph and a mass spectrometer, it is possible to prevent a decrease in measurement accuracy due to a difference in gas pressure or gas component ratio.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a preferred embodiment of a gas analysis system according to the present invention.

FIG. 2 is a waveform chart showing an output flow rate of a column.

FIG. 3 is a flowchart showing an operation of the gas analysis system.

[Explanation of symbols]

10 gas chromatograph, 12 mass spectrometer, 14
Operation unit, 16 control unit, 22 carrier gas generator, 2
3A standard gas supply, 23B sample gas supply,
24 columns, 26 output detectors, 30 introduction amount regulator, 200 main gas passage, 202 carrier gas replenishment passage.

Claims (9)

[Claims] 1. A sample gas containing a gas of interest is introduced together with a carrier gas, a gas chromatograph for selectively discharging the gas of interest, and an exhaust gas discharged from the gas chromatograph are introduced to analyze the gas of interest. And a replenishing means for replenishing the exhaust gas with the carrier gas in order to control the ratio of the gas of interest and the carrier gas in the exhaust gas to a predetermined value. A gas analysis system, wherein an exhaust gas having a predetermined gas ratio is introduced into a gas analyzer. 2. The system according to claim 1, further comprising an introduction amount adjusting means for controlling a flow rate of the exhaust gas introduced into the gas analyzer to a constant value, wherein the gas analyzer has a predetermined gas ratio and A gas analysis system wherein exhaust gas having a gas amount is introduced. 3. The estimation system according to claim 1, wherein the estimation unit estimates an amount of the gas of interest to be subsequently discharged based on an amount of the reference gas previously discharged from the gas chromatograph. And a replenishing amount control means for controlling the replenishing amount of the carrier gas based on the amount of the noted gas. 4. The system according to claim 1, wherein a gas component is analyzed by a sample gas analysis mode for analyzing a gas of interest in the sample gas, and an analysis process similar to the sample gas for correcting a result of analysis of the gas of interest. A standard gas analysis mode for analyzing a known standard gas, and, in the standard gas analysis mode, an amount β of the reference gas previously discharged from the gas chromatograph and an amount α of the gas of interest subsequently discharged, Based on the amount β ′ of the reference gas previously discharged from the gas chromatograph in the sample gas analysis mode, the amount α ′ of the target gas discharged after the discharge of the reference gas in the sample gas analysis mode is estimated. An estimating operation unit, and a replenishment amount control unit that controls the replenishment amount of the carrier gas based on the estimated amount α ′ of the gas of interest. Gas analysis system comprising a and. 5. The system according to claim 4, wherein in the sample gas analysis mode and the standard gas analysis mode, a gas ratio of a carrier gas and a target gas in the exhaust gas introduced into the gas analyzer and the exhaust gas thereof. A gas analysis system characterized in that the amount of gas is made the same. 6. The apparatus according to claim 5, further comprising a correction unit configured to correct a target gas analysis result in the sample gas analysis mode using an analysis result in the standard gas analysis mode. Analysis system. 7. The gas analysis system according to claim 1, further comprising a replenishing amount control means for controlling a replenishing amount of the carrier gas based on an amount of the gas of interest discharged from the gas chromatograph. system. 8. The gas analysis system according to claim 1, wherein the sample gas is exhaled gas, and the gas of interest is CO ₂ . 9. The gas analysis system according to claim 8, wherein the gas analyzer is an apparatus for measuring an isotope ratio of ¹² CO ₂ and ¹³ CO ₂ .