Gas analysis method and gas analysis apparatus

Abstract

This invention provides a gas analysis method and analytical apparatus that can analyze target gases with high accuracy by suppressing the effects of differences in extraction time and the spread of extraction time. [Solution] The gas analysis method comprises a gas extraction step of heating a sample in a gas extraction furnace 10 to extract elements contained in the sample as gas; a sampling step of transporting the gas extracted from the extraction furnace 10 by a carrier gas and sampling the gas flow transported by the carrier gas into a sample storage unit 24 of a predetermined capacity at a sampling time which is after a predetermined time has elapsed from an arbitrary time; and a gas chromatography analysis step of introducing the sampled gas into a gas chromatograph 30 to quantify the gas to be analyzed.

Description

Technical Field

[0001] The present disclosure relates to a gas analysis method and a gas analysis apparatus.

Background Art

[0002] An oxygen-nitrogen analyzer (ON meter) can rapidly and skill-freely analyze the nitrogen content, oxygen content, and hydrogen content from a mixed gas obtained by heating a steel sample. To analyze the nitrogen content in a steel sample, it was sufficient to remove oxygen and hydrogen contained in the steel sample as carbon dioxide and water, and detect and quantify the remaining gas with a nitrogen detector.

[0003] However, when quantifying nitrogen in a sample with a high oxygen content, oxygen that cannot be completely removed mixes into the nitrogen detector, making it impossible to perform correct measurement of the nitrogen content. Accordingly, a technique for performing analysis by connecting a column to the extraction furnace of an oxygen-nitrogen analyzer has been disclosed (see Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, firstly, the mixed gas from the sample is continuously generated within the oxygen-nitrogen analyzer, and each gas component is extracted at different timings (differences in extraction time) and with a temporal spread (spread of extraction time). In other words, the extraction of each gas component is affected by both the difference in extraction time and the spread of extraction time. Furthermore, the retention time in the gas chromatograph differs for each gas component (differences in retention time), and also results in a peak structure with a temporal width (spread of retention time). That is, the final signal obtained is a superposition of the difference in extraction time and retention time, as well as the spread of extraction time and the spread of retention time. Retention time is important for component determination in gas chromatography, and if differences in extraction time overlap, peak positions may shift, peaks may become close together, or peak positions may even be reversed. Also, when the spread of extraction time and the spread of retention time overlap, the temporal width of the peak widens, and the signal intensity becomes relatively weaker. Due to these effects, component determination becomes difficult, separation accuracy and the limit of quantification deteriorate, and the reliability of the measurement may be compromised.

[0006] Furthermore, the crucible used for extraction inevitably adsorbs oxygen and other substances, and as part of the experimental procedure, degassing of the crucible is performed before the main measurement. In the method disclosed in Non-Patent Literature 1, the degassed crucible can accumulate in the column and elute, which can increase the blank level during the main measurement, leading to a problem of deterioration of the detection limit. The method disclosed in Non-Patent Literature 1 attempts to improve this by increasing the degassing time, but it is difficult to completely suppress the effect on the blank level, and there is also the problem that the measurement time increases by the amount of the degassing time.

[0007] Therefore, the present invention has been made to solve the above problems, and aims to provide a gas analysis method and analytical apparatus that can analyze a target gas with high accuracy by suppressing the effects of differences in extraction time and the spread of extraction time of the target gas. [Means for solving the problem]

[0008] In view of the above-mentioned problems, the inventors have diligently studied and found a method for performing highly accurate and rapid measurements by combining a gas sampling mechanism (cutting section) between the gas extraction furnace and the detection unit (gas chromatograph and TCD).

[0009] The gist of this disclosure is as follows:

[0010] (1) A gas extraction step in which the sample is heated in a gas extraction furnace to extract the elements contained in the sample as gas, A sampling step in which the gas extracted from the gas extraction furnace is transported by a carrier gas, and at a sampling time which is a predetermined time after a predetermined time has elapsed from an arbitrary time, the gas flow transported by the carrier gas is sampled in a sample storage unit of a predetermined capacity, The gas chromatographic analysis step involves introducing the sampled gas into a gas chromatograph and quantifying the target gas, A gas analysis method having the following characteristics.

[0011] (2) The gas analysis method according to (1) above, wherein the sampling time is selected from among the multiple different candidate sampling times based on the gas chromatography analysis results obtained by performing the sampling step and the gas chromatography analysis step for multiple different candidate sampling times.

[0012] (3) The gas analysis method according to (1) above, wherein the sampling time is selected from among the multiple different candidate sampling times, by sampling the gas flow carried by the carrier gas into multiple sample storage units of predetermined capacity at multiple different candidate sampling times, introducing the gas sampled in each of the multiple sample storage units into the gas chromatograph to obtain a gas chromatogram, and selecting from among the multiple different candidate sampling times based on the gas chromatogram. (4) The gas analysis method according to (2) or (3) above, wherein the sampling time is selected based on the degree of interference of the detection intensity of gases other than the gas to be analyzed with respect to the detection intensity of the gas to be analyzed.

[0013] (5) The gas analysis method according to any one of (1) to (3) above, wherein the arbitrary time is the timing for dropping the sample into the gas extraction furnace heated to a predetermined temperature.

[0014] (6) A gas extraction step in which the sample is heated in a gas extraction furnace to extract the elements contained in the sample as gas, A sampling step in which the gas extracted from the gas extraction furnace is transported by a carrier gas, and the gas flow transported by the carrier gas is sequentially sampled in a plurality of sample storage units of a predetermined capacity, The gas chromatography analysis step involves introducing each of the sampled gases into a gas chromatograph and quantifying the multiple target gases, A gas analysis method having the following characteristics.

[0015] (7) The gas analysis method according to (6) above, wherein the sampling step involves sampling the gas flow carried by the carrier gas at multiple sampling times, which are predetermined time intervals from any given time, in multiple sample storage units of predetermined capacity.

[0016] (8) The gas analysis method according to (7) above, wherein the sampling time is selected from among the multiple different candidate sampling times based on the gas chromatogram obtained by performing the sampling step and the gas chromatography analysis step for a plurality of different candidate sampling times.

[0017] (9) The gas analysis method according to (7) above, wherein the sampling time is selected from among the multiple different candidate sampling times, by sampling the gas flow carried by the carrier gas into multiple sample storage units of predetermined capacity at multiple different candidate sampling times, introducing the gas sampled in each of the multiple sample storage units into the gas chromatograph to obtain a gas chromatogram, and selecting from among the multiple different candidate sampling times based on the gas chromatogram. (10) The sampling time is selected based on the degree of interference of the detection intensity of a gas other than the target gas to be analyzed with respect to the detection intensity of the target gas to be analyzed, according to any one of the above (7) to (9).

[0018] (11) The arbitrary time is the timing at which the sample is dropped into the gas extraction furnace heated to a predetermined temperature, according to any one of the above (6) to (9).

[0019] (12) An extraction furnace that heats a sample to extract an element contained in the sample as a gas; and a sampling unit that samples the gas flow conveyed by the carrier gas at a sampling time that is after a predetermined time has elapsed from an arbitrary time; a gas chromatograph that quantifies the sampled gas; A gas analysis apparatus comprising: [Effect of the Invention]

[0020] According to the present invention, it is possible to provide a gas analysis method and an analysis apparatus capable of analyzing a target gas to be analyzed with high accuracy while suppressing the influence of differences in the extraction time of the target gas to be analyzed and the spread of the extraction time. [Brief Description of the Drawings]

[0021] [Figure 1] It is a diagram showing a configuration example of a gas analysis apparatus according to an embodiment of the present disclosure. [Figure 2] It is a diagram showing the relationship between the extraction time from the extraction furnace (horizontal axis) and the output of the gas chromatograph (vertical axis). [Figure 3] It is a diagram showing the first aspect, the second aspect, and the third aspect of the gas analysis apparatus of the present invention. [Figure 4] It is a gas chromatogram showing the TCD detection intensity in each case of the method of the present invention and the comparative method. [Figure 5]This is a characteristic diagram showing the measurement results, illustrating the relationship between the holding time (horizontal axis) and the output intensity (horizontal axis) for each timing when the extraction timing is changed. [Modes for carrying out the invention]

[0022] Several embodiments relating to this disclosure will be described below with reference to the drawings. However, these descriptions are intended to be merely illustrative of preferred embodiments of this disclosure and are not intended to limit this disclosure to such specific embodiments. In the following description, similar components will be given the same reference numerals.

[0023] This disclosure relates to a gas analysis method and a gas analyzer for heating a sample in a gas extraction furnace, extracting elements contained in the sample as gases, and accurately and rapidly measuring the amount of nitrogen and other elements in the sample using a chromatograph. Figure 1 shows an example of the configuration of a gas analyzer 100 according to one embodiment of this disclosure. The gas analyzer 100 comprises an extraction furnace 10, a sampling unit 20, and a gas chromatograph (column + TCD detector) 30. In this embodiment, as shown in Figure 1, the gas in the sample extracted from the extraction furnace 10 is sampled in the sampling unit 20 and analyzed by the gas chromatograph 30. The following describes in detail each step in one embodiment of the present invention.

[0024] <Gas extraction process> In the gas extraction process, the sample is heated in a gas extraction furnace 10 to extract the elements contained in the sample as gases. The extraction furnace 10 consists of a crucible and a heating means. A graphite crucible can be used as an example of the crucible. As the heating means, electrostatic heating of the crucible or high-frequency induction heating can be applied. The heating temperature is preferably set to the temperature at which the sample melts. When a graphite crucible is used, for example, oxygen in a metal sample is extracted as CO or CO2, nitrogen as N2, and hydrogen as H2. The extraction furnace 10 is covered so as not to be exposed to the outside air and is equipped with an inlet port and an outlet port for a carrier gas. An inert gas is preferred as the carrier gas, and it is more preferable to use a noble gas such as Ar or He. The flow rate of the inert gas is not particularly limited, but for example it can be 1 to 1000 mL / min, preferably 100 to 700 mL / min, and more preferably 200 to 500 mL / min. The gas extracted from the sample is transported by the inert gas flow and flows out from the outlet port.

[0025] <Sampling Process> In the sampling process, the gas extracted from the gas extraction furnace 10 is transported by a carrier gas, and at the sampling time (t=t_s), which is a predetermined time after an arbitrary time (t=0), the gas flow transported by the carrier gas is sampled into a sample storage unit 24 of a predetermined capacity. The capacity of the sample storage unit 24 is not particularly limited, but is appropriately determined according to the gas chromatograph used. The capacity of the sample storage unit 24 is, for example, 1 μL to 10 mL. The gas extracted from the sample in the extraction furnace 10 is transported by a carrier gas. The sampling unit 20 samples the carrier gas flow containing the gas extracted from the sample at a predetermined timing. The sampling unit 20 includes a dispensing unit 22 (for example, a six-way valve) and a sample storage unit 24. Here, the starting point of time (t=0) can be set arbitrarily. The starting point of time can be, for example, the timing when the sample is dropped into the extraction furnace 10 (crucible) heated to a predetermined temperature. Alternatively, if the sample is placed in a crucible beforehand and the crucible is heated from room temperature, the starting point of the time may be the moment when the temperature of the crucible reaches a predetermined temperature. The sampling time (t=t_s) is selected from among several different candidate sampling times based on the analysis results obtained by performing the gas extraction step, sampling step, and gas chromatography analysis step at several different candidate sampling times. It is not necessary to perform the gas extraction step at several different candidate sampling times, but if, for example, the time interval between candidate sampling times is short and sampling cannot keep up, the process may start with the gas extraction step. In this case, the sampling time is selected considering the degree of interference between the detection intensity of the analyte gas and the detection intensity of other gases. The sampling time is selected so as to minimize the interference between the detection intensity of the analyte gas and the detection intensity of other gases. Here, the degree of interference may be expressed, for example, as the ratio of the peak height of the analyte gas to the peak height of the other gases in the gas chromatogram. The sampling time can be determined so as to maximize this ratio of peak heights. Another way to determine that the degree of interference is minimized is to select a peak where the overlap between the tails of the analyte gas and the other peaks is as small as possible.

[0026] Sampling is performed by operating the cutting section 22, for example as shown in Figure 1, to retain the carrier gas flow in the sample storage section 24. The sample storage section 24 is not particularly limited, but as an example, it may be a SUS pipe formed in a loop shape (sample loop).

[0027] <Gas chromatography analysis process> In the gas chromatography analysis process, the sampled gas is introduced into the gas chromatograph 30 to quantify the target gas. The sampled gas is transported to the gas chromatograph 30 by the operation of the cutting unit 22. It is preferable to use the same gas as the gas used in the gas extraction process as the carrier gas for transporting to the gas chromatograph 30. The gas detector is not particularly limited, but one example is a TCD( T Hermal C onductivity D An analyzer (thermal conductivity type detector) can be applied. The column packing material for the gas chromatograph 30 is appropriately selected depending on the gas to be analyzed, for example, molecular sieves.

[0028] In gas chromatography analysis, the resulting chart (gas chromatogram) measures peaks separated by differences in retention time (the time each gas species is retained in the column packing material). However, when other gases with similar retention times are sampled simultaneously, the peaks of the other gases overlap with the peak of the target gas, making it difficult to accurately measure the peak intensity of the target gas. This problem becomes particularly pronounced when the concentrations of other gases are significantly higher than those of the target gas.

[0029] On the other hand, if the gasification and extraction time differs depending on the type of gas during the heating and melting process of a solid sample, the timing when only the target gas is delivered can be used as the gas sampling time. In this case, the column of the gas chromatograph 30 is not necessarily required.

[0030] If there are multiple gas species to be analyzed, the sampling time can be set to the timing when only each gas species is sampled. If the gasification and extraction times of the gas to be analyzed and other gases cannot be completely separated, the sampling time may be set to the timing when the influence of other gases on the gas to be analyzed is minimized. Furthermore, the separation of gasification and extraction times can be improved by controlling the heating rate during the heating of the crucible on which the sample is placed. Note that when separation and quantification are performed by gas chromatograph 30, the sampled gas sample may contain multiple gas species to be analyzed.

[0031] The sampling time and duration affect the measurement sensitivity, the correlation coefficient of the calibration curve, the repeatability of the measurement, and the feasibility of simultaneous measurement of gases with different extraction times. Therefore, they can be selected according to the conditions required by the operator. Figure 2 shows the relationship between the extraction time from the extraction furnace 10 (horizontal axis) and the output of the gas chromatograph 30 (vertical axis). Figure 2 shows the extraction times of gas A and gas B. In Figure 2, T1 indicates the moment when the proportion of the analyte gas is highest. T2 indicates the time when the analyte gas is present in complete quantities. T3 and T4 indicate the time when gases other than the analyte gas are also present, respectively.

[0032] For example, the analyzer may select only the moment (T1) when the proportion of the gas to be analyzed is highest as the sampling time and time interval. The sampling time and time interval may include the entire time during which the gas to be analyzed is extracted, as shown in T2 in Figure 2. Alternatively, the sampling time and time interval may include the time during which gases other than the gas to be analyzed are also extracted, as shown in T3 in Figure 2.

[0033] In one embodiment of the present invention, the sampling time and time width are determined from gas chromatography charts obtained by sampling the same sample at different sampling times and time widths, such that the influence of peaks of other gas species on the peak of the gas species to be analyzed is minimized.

[0034] According to the gas analysis method described above, even when a large amount of gas other than the target gas is gasified and extracted, analytical results that are not affected by this can be obtained, and highly accurate quantitative values ​​can be obtained with high precision.

[0035] Next, the gas analyzer according to the present invention will be described. Figure 3(a) shows a first embodiment of the gas analyzer of the present invention. The gas analyzer 100 of this embodiment consists of an extraction furnace 10, a sampling unit 20, and a gas chromatograph 30. The extraction furnace 10 includes a crucible, a heating means, a gas inlet port, a gas outlet port, and a housing capable of shielding the crucible from the outside air. As described above, a graphite crucible can be used as an example of the crucible, and as the heating means, electric heating of the crucible or high-frequency induction heating can be applied. The extraction furnace 10 may further be equipped with a flow meter or flow control meter at least one of the gas inlet port and the gas outlet port. Furthermore, it is preferable that the extraction furnace 10 is equipped with a crucible temperature measuring sensor and a temperature display unit that displays the temperature measured by this sensor. The extraction furnace 10 may also be equipped with a temperature and heating rate control unit. Furthermore, the extraction furnace 10 may be equipped with a sample input unit into which a sample can be introduced into the crucible.

[0036] The sampling unit 20 consists of a cutting unit 22 and a sample storage unit 24. The cutting unit 22 has the function of cutting out a portion of the mixed gas continuously generated from the extraction furnace 10 in time intervals and sending it to the sample storage unit 24. For example, the six-way valve described above can be used as the cutting unit 22 of the sampling unit 20. On the other hand, the cutting unit 22 may be composed of a valve other than a six-way valve or components other than a six-way valve. For example, a sample loop formed by shaping a SUS pipe into a loop can be used for the sample storage unit 24. The cutting unit 22 is connected to piping that connects to the outlet port of the extraction furnace 10, piping that connects to the inlet to the sample storage unit 24, and bypass piping. By operating the cutting unit 22, it is possible to sample a predetermined amount of gas transported from the outlet port of the extraction furnace 10 at any timing and time interval.

[0037] A commercially available gas chromatograph can be used as the gas chromatograph 30. Generally, a gas chromatograph has a sample gas introduction unit, a column, a column heating unit, a temperature control unit, a detector, and a chromatogram output unit. In this embodiment, the detector may be a TCD (thermal conductivity detector).

[0038] Figure 3(b) shows a second embodiment of the gas analyzer according to the present disclosure. The second embodiment differs from the first embodiment in Figure 3(a) in that it has multiple sampling units 20. The gas transported from the outlet port of the extraction furnace 10 is introduced to each of the multiple sampling units 20 through branch pipes. According to the second embodiment, for example, gas can be sampled at each sampling unit 22 at different timings and sequentially introduced into the gas chromatograph 30. In this second embodiment, sampling is performed at each sampling unit 20. Therefore, in the first embodiment, when sampling different gases, it is necessary to wait for the entire amount of sampled gas to be introduced from the sample storage unit 24 into the gas chromatograph 30 before proceeding with the next gas sampling, but this is not necessary in the second embodiment. Thus, the time required when sequentially sampling gases at different timings can be shortened. In addition, in the second embodiment, it is not necessary to provide multiple entire sampling units 20; multiple sample storage units 24 may be provided.

[0039] Furthermore, Figure 3(c) shows a third embodiment of the gas analyzer according to this disclosure. In the third embodiment, multiple pairs of sampling units 20 and gas chromatographs 30 are provided. In the third embodiment, which provides multiple pairs of sampling units 20 and gas chromatographs 30 as shown in Figure 3(c), time efficiency can be further improved.

[0040] In the second or third embodiment, the sampling step involves transporting the gas extracted from the gas extraction furnace 10 by a carrier gas, and sequentially sampling the gas flow transported by the carrier gas into multiple sample storage units 24 of predetermined capacity. In the gas chromatography analysis step, the sampled gases are each introduced into a gas chromatograph 30 to quantify multiple target gases.

[0041] As described above, in this embodiment, a portion of the continuously generated mixed gas is separated over time, and the separated mixed gas is analyzed by gas chromatography. If the timing of separation is unknown, the optimal conditions are determined experimentally by changing the separation timing.

[0042] As described above, according to this embodiment, since the mixed gas is extracted before measurement by gas chromatography, the effects of differences in extraction time and the spread of extraction time can be suppressed, making it possible to measure with high accuracy even for samples with complex component systems. Furthermore, by selecting the timing of extracting the mixed gas, it is possible to prevent degassing during crucible preheating from contaminating the column, thereby suppressing deterioration of the blank level and an increase in measurement time. Therefore, it is possible to provide a gas analysis method and gas analyzer that suppress the effects of differences in extraction time and the spread of extraction time of the analyte gas, improve separation accuracy and the limit of quantification, and shorten the measurement time. [Examples]

[0043] The present disclosure will be specifically explained below with reference to examples of embodiments. The conditions in the embodiments are merely examples adopted to confirm the feasibility and effectiveness of the present disclosure, and the present disclosure is not limited to the conditions in the embodiments. The present disclosure may adopt various conditions as long as they do not depart from its essence and achieve its objectives.

[0044] (Example 1) To confirm the effect of the cutting section 22, the change in TCD detection intensity (gas chromatogram) due to the holding time in each case of the present invention method and the comparative method was compared. Pin-shaped steel samples were dropped into a crucible heated to 2000°C from room temperature and heated and melted. He was transported as a carrier gas at a flow rate of 400 mL / min. In the comparative method, the gas transported from the extraction furnace was adjusted to a flow rate of 10 mL / min and introduced directly into the gas chromatograph. In the inventive method, the amount to be cut off was 1 mL. After dropping the sample into the crucible, 1 mL was cut off from the gas passing through in 10 seconds starting 30 seconds later, and the carrier gas flow rate was adjusted to 30 mL / min and introduced into the gas chromatograph. Figure 4 shows the chromatograms for each case of the present invention method and the comparative method. Here, Figure 4(a) shows the chromatogram of the comparative method, and Figure 4(b) shows the gas chromatogram of the present invention method. As shown in Figure 4(a), in the comparative method, the detection intensity peak is broadened due to the overlap of the extraction time and the retention time of the gas chromatograph, and the separation is insufficient. On the other hand, as shown in Figure 4(b), in the present invention, the nitrogen peak, which has a retention time of approximately 3 minutes, can be separated and measured from the peaks of other gases.

[0045] (Example 2) In Example 2, the timing for extracting the target gas by the sampling unit 20 was determined for the analysis of a pin-shaped steel sample using the inventive method. The sample was continuously and rapidly heated by dropping it into a crucible heated from room temperature to 2000°C. Ar was used as the carrier gas and transported at a flow rate of 400 mL / min. By dropping the sample into a crucible heated to 2000°C, various gases are continuously generated and extracted up to 2000°C. Therefore, the optimal extraction timing for the target gas was determined experimentally. The extraction time interval was set to 10 seconds, and the amount extracted was 1 mL. Measurements were performed by changing the extraction timing every 10 seconds starting immediately after heating.

[0046] Figure 5 is a characteristic diagram showing the measurement results, illustrating the gas chromatograms obtained for each timing when the extraction timing was set to 0 seconds, 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, and 60 seconds after dropping the material into the crucible. In Figure 5, the gas chromatogram obtained when the extraction timing was set to 0 seconds after heating is C1, the gas chromatogram obtained when the extraction timing was set to 10 seconds after heating is C2, the gas chromatogram obtained when the extraction timing was set to 20 seconds after heating is C3, and the gas chromatogram obtained when the extraction timing was set to 30 seconds after heating is C4. Also in Figure 5, the gas chromatogram obtained when the extraction timing was set to 40 seconds after heating is C5, the gas chromatogram obtained when the extraction timing was set to 50 seconds after heating is C6, and the gas chromatogram obtained when the extraction timing was set to 60 seconds after heating is C7.

[0047] As a result, for example, when selecting a gas (N2) with a column retention time of 2.5 minutes as the gas to be measured, it was found that the extraction time for separating N2 from the sample was between 20 and 50 seconds, and the proportion of N2 in the extracted mixed gas was highest at 30 seconds (gas chromatogram C4 shown in Figure 5).

[0048] (Example 3) In Example 3, we investigated improvements in the accuracy of measurements using the present invention method and comparative methods 1 (oxygen-nitrogen analyzer: ON meter) and 2 (prior research example, gas chromatograph directly connected to oxygen-nitrogen analyzer: ON meter + column). KNO3 was used as the standard reagent, and samples were prepared at three levels with nitrogen content of 100 μg, 300 μg, and 500 μg. The sampling time for the present invention method was determined using the same procedure as when the results for Example 1 were obtained. Table 1 shows the experimental results for comparative methods 1, 2, and the inventive method. Compared with comparative methods 1 and 2, the inventive method showed that the measured nitrogen content was closer to the nitrogen content in the sample, confirming improved accuracy. Thus, it was found that the inventive method improves the accuracy of measurements and allows for experimental determination of the extraction time.

[0049] [Table 1] [Explanation of symbols]

[0050] 10 Extraction furnace 20 Sampling section 22 Cutting section 24 Sample storage section 30 Gas Chromatograph 100 Gas analyzer

Claims

1. A gas extraction step in which the sample is heated in a gas extraction furnace to extract the elements contained in the sample as gas, A sampling step in which the gas extracted from the gas extraction furnace is transported by a carrier gas, and at a sampling time which is a predetermined time after a predetermined time has elapsed from an arbitrary time, the gas flow transported by the carrier gas is sampled in a sample storage unit of a predetermined capacity, The gas chromatographic analysis step involves introducing the sampled gas into a gas chromatograph and quantifying the target gas, A gas analysis method having the following characteristics.

2. The gas analysis method according to claim 1, wherein the sampling time is selected from among a plurality of different candidate sampling times based on the gas chromatogram obtained by performing the sampling step and the gas chromatography analysis step for a plurality of different candidate sampling times.

3. The gas analysis method according to claim 1, wherein the sampling time is selected from among the multiple different candidate sampling times, by sampling the gas flow carried by the carrier gas into multiple sample storage units of predetermined capacity at multiple different candidate sampling times, introducing the gas sampled in each of the multiple sample storage units into the gas chromatograph to obtain a gas chromatogram, and selecting from among the multiple different candidate sampling times based on the gas chromatogram.

4. The gas analysis method according to claim 2 or 3, wherein the sampling time is selected based on the degree of interference between the detection intensity of a gas other than the gas to be analyzed and the detection intensity of the gas to be analyzed.

5. The gas analysis method according to any one of claims 1 to 3, wherein the aforementioned arbitrary time is the timing for dropping the sample into the gas extraction furnace heated to a predetermined temperature.

6. A gas extraction step in which the sample is heated in a gas extraction furnace to extract the elements contained in the sample as gas, A sampling step in which the gas extracted from the gas extraction furnace is transported by a carrier gas, and the gas flow transported by the carrier gas is sequentially sampled in a plurality of sample storage units of a predetermined capacity, A gas chromatography analysis step is performed in which the sampled gases are each introduced into a gas chromatograph and one or more target gases are quantified. A gas analysis method having the following characteristics.

7. The gas analysis method according to claim 6, wherein the sampling step involves sampling the gas flow carried by the carrier gas at multiple sampling times, which are predetermined time intervals from any given time, in multiple sample storage units of predetermined capacity.

8. The gas analysis method according to claim 7, wherein the sampling time is selected from among a plurality of different candidate sampling times based on the gas chromatogram obtained by performing the sampling step and the gas chromatography analysis step for a plurality of different candidate sampling times.

9. The gas analysis method according to claim 7, wherein the sampling time is selected from among the multiple different candidate sampling times, by sampling the gas flow carried by the carrier gas into multiple sample storage units of predetermined capacity at multiple different candidate sampling times, introducing the gas sampled in each of the multiple sample storage units into the gas chromatograph to obtain a gas chromatogram, and selecting from among the multiple different candidate sampling times based on the gas chromatogram.

10. The gas analysis method according to any one of claims 7 to 9, wherein the sampling time is selected based on the degree of interference of the detection intensity of gases other than the gas to be analyzed with respect to the detection intensity of the gas to be analyzed.

11. The gas analysis method according to any one of claims 6 to 9, wherein the arbitrary time is the timing for dropping the sample into the gas extraction furnace heated to a predetermined temperature.

12. An extraction furnace that heats a sample to extract elements contained in the sample as gas, A sampling unit that samples the gas flow carried by a carrier gas at a sampling time which is a predetermined time after an arbitrary time, A gas chromatograph for quantifying the sampled gas, A gas analyzer equipped with the following features.

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