A dynamic dilution preparation system and preparation method for a gas reference material

Abstract

The present invention relates to a dynamic dilution preparation system and a preparation method for a gas reference material. The system includes a dilution gas source (10), a raw material gas source (20), a plurality of flow meters (30), a humidifying device (40), connecting pipelines, a mixing chamber (50), a temperature and humidity meter (60), and a heating device (70). The dilution gas source (10) is connected to the humidifying device (40) via a connecting pipeline through a first flow meter (30-1), and the humidifying device (40) is connected to the mixing chamber (50) via a connecting pipeline. The raw material gas source (20) is connected to the mixing chamber (50) via a connecting pipeline through a second flow meter (30-2). The temperature and humidity meter (60) is connected to the outlet connecting pipeline (51) of the mixing chamber (50). The humidifying device (40), the mixing chamber (50), and the temperature and humidity meter are arranged in the heating device (70).

Description

Technical Field

[0001] The present invention relates to the technical field of gas reference materials, and particularly relates to a dynamic dilution preparation system and a preparation method for gas reference materials. Background Art

[0002] For gas components with unstable chemical properties or low concentrations that are prone to adsorption, it is difficult to meet the experimental requirements using bottled standard gases. In this case, the dynamic gas mixing method is usually required. In this method, a raw gas with a known concentration and a dilution gas continuously enter a mixer at a constant ratio, so that a standard gas with a certain concentration can be continuously prepared and supplied. The dilution ratio can be calculated based on the flow rate ratio of the two gas flows, and then the concentration of the standard gas can be calculated based on the dilution ratio. The dynamic gas mixing method can not only provide a large amount of standard gas, but also obtain a standard gas with the required concentration by adjusting the flow rate ratio of the raw gas and the dilution gas. This method is particularly suitable for preparing low-concentration or reactive standard gases.

[0003] However, there are some defects in the above-mentioned prior art. For example, for unstable gas components, such as volatile organic compounds, they are prone to adsorb on the inner wall of the container during the dilution process, resulting in a decrease in the quantity value, thus causing a deviation in the accurate quantity value of the generated standard gas; for low-concentration components, due to the adsorption phenomenon, it often takes a long time to purge to make the system reach stability, which greatly reduces the use efficiency of the standard dilution device; in addition, the main goal of the prior art is to obtain a standard gas with a specific concentration, but the generated standard gases are all dry gases, which still have differences from real air samples. For sensors with a large influence of humidity, such as electrochemical sensors or mass spectrometry components, there is a large deviation between the calibration result using dry standard gas and the real value.

[0004] Therefore, there is a need for new preparation technologies and equipment for gas reference materials. Summary of the Invention

[0005] In order to solve at least some of the problems existing in the above-mentioned prior art, the technical object of the present invention is to provide a dynamic dilution preparation system and a preparation method for gas reference materials, which can reduce the adsorption of components on the inner wall of the dilution system, reduce the purging time for the system to reach a stable concentration, improve the working efficiency of the system, and can control the humidity level in the standard gas and eliminate problems such as water condensation on the inner wall of the gas mixing pool.

[0006] According to one aspect of the present invention, there is provided a dynamic dilution preparation system for gas reference materials, which includes:

[0007] Dilution gas source (10), raw material gas source (20), multiple flow meters (30), humidifying device (40), connecting pipelines, mixing chamber (50), temperature and humidity meter (60), heating device (70),

[0008] The dilution gas source (10) is connected to the humidifying device (40) via the first flow meter (30-1) through a connecting pipeline,

[0009] The humidifying device (40) is connected to the mixing chamber (50) via a connecting pipeline;

[0010] The raw material gas source (20) is connected to the mixing chamber (50) via the second flow meter (30-2) through a connecting pipeline;

[0011] The temperature and humidity meter (60) is connected to the outlet connecting pipeline (51) of the mixing chamber (50);

[0012] The humidifying device (40), the mixing chamber (50) and the temperature and humidity meter are arranged in the heating device (70).

[0013] According to an embodiment of the present invention, a third flow meter (30-3) is arranged between the first flow meter (30-1) and the humidifying device (40), and a connecting pipeline is led out between the first flow meter (30-1) and the third flow meter (30-3) and connected to the connecting pipeline between the humidifying device (40) and the mixing chamber (50), thereby forming a bypass.

[0014] According to an embodiment of the present invention, the mixing chamber is a silanized glass mixing chamber or a 316L passivated mixing chamber.

[0015] According to an embodiment of the present invention, the heating method of the heating device (70) is selected from air bath heating, heating jacket and resistance wire heating.

[0016] According to an embodiment of the present invention, the humidifying device (40) is selected from a bubbling bottle, a nafion humidifying tube, and an ultrasonic humidifier.

[0017] According to an embodiment of the present invention, the humidifying device (40) is a two-stage glass bubbling bottle.

[0018] According to an embodiment of the present invention, the connecting pipelines between the above-mentioned components are silanized glass pipelines or 316L passivated pipelines.

[0019] According to an embodiment of the present invention, the flow meter (30) is selected from a mass flow meter, a capillary restrictor, a sonic nozzle flow meter, a laminar flow meter, and an electronic needle valve flow meter.

[0020] According to an embodiment of the present invention, the dynamic dilution preparation system for the gas reference material further includes a flow control valve (41) provided on the inlet and outlet pipelines of the humidifying device (40) and / or provided on the bypass.

[0021] According to an embodiment of the present invention, the dynamic dilution preparation system for the gas reference material further includes a control module, and the flowmeter, the temperature and humidity meter, and the heating device are connected to the control module.

[0022] According to another aspect of the present invention, there is provided a method for dynamically diluting and preparing a gas reference material, the method including a pre-purging step, and the pre-purging step includes:

[0023] a. Using a heating device (70) to heat the humidifying device (40) and the mixing chamber (50) to a predetermined temperature;

[0024] b. Closing the outlet of the mixing chamber (50), then opening the dilution gas source (10) to increase the pressure in the dilution gas pipeline to a predetermined pressure, and then closing the dilution gas source (10);

[0025] c. Opening the outlet of the mixing chamber (50) to release the pressure;

[0026] d. Repeating steps b-c multiple times to fill the dilution gas pipeline with the dilution gas, and then closing the dilution gas pipeline;

[0027] e. Closing the outlet of the mixing chamber (50), then opening the raw material gas source (20) to increase the pressure in the raw material gas pipeline to a predetermined pressure, and then closing the raw material gas source (20);

[0028] f. Opening the outlet of the mixing chamber (50) to release the pressure;

[0029] g. Repeating steps e-f multiple times to fill the raw material gas pipeline with the raw material gas.

[0030] According to an embodiment of the present invention, the method further includes a step of dynamically diluting and preparing the gas reference material after the pre-purging step, and the dynamic dilution preparation step includes humidifying the dilution gas by using the humidifying device (40).

[0031] According to an embodiment of the present invention, the humidifying device (40) is a two-stage glass bubbler.

[0032] According to an embodiment of the present invention, the dilution gas pipeline is divided into two paths, one path does not pass through the humidifying device (40), and the other path is humidified by passing through the humidifying device (40), and then the two paths are combined.

[0033] According to an embodiment of the present invention, the connecting pipelines in the dilution gas pipeline and the raw material gas pipeline are silanized glass pipelines or 316L passivated pipelines.

[0034] According to an embodiment of the present invention, the mixing chamber is a silanized glass mixing chamber or a 316L passivated mixing chamber.

[0035] The present invention adopts passivated pipelines, which greatly reduces the adsorption of unstable components on the inner wall of the dilution system. Before dilution, the system is purged and cleaned, and a cleaning mode of multiple cycles of system closed pressure - baking - venting - purging is adopted, which greatly reduces the purging time for the system to reach a stable concentration. In the gas mixing pool (mixing chamber), a silanized glass gas pool or a passivated mixing chamber is used, and both the pipeline and the gas mixing pool can be temperature - controlled and heated, minimizing problems such as inner wall adsorption and water condensation in the gas mixing pool. In addition, the present invention uses a method of mixing wet gas and dry gas in proportion to generate a dilution gas with a specific humidity, and remixes it with the sample gas to form a standard gas with a certain concentration, specific humidity, and temperature, integrating the functions of quantitative humidification and quantitative dilution. Brief Description of the Drawings

[0036] The same reference numerals in the drawings denote the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. The objectives and features of the present invention will become more apparent in view of the following description in conjunction with the drawings, in which:

[0037] Figure 1 is a schematic diagram of a dynamic dilution and preparation system for a gas reference material according to an embodiment of the present invention.

[0038] Figure 2 is a schematic diagram of the operation interface of the control software according to an embodiment of the present invention.

[0039] Figure 3 is a schematic diagram of the experimental results of the comparison of the humidification performance of a single - stage glass bottle and a double - stage glass bottle according to an embodiment of the present invention.

[0040] Figure 4 is a schematic diagram of the experimental results of the influence of different mixer materials on the system stabilization time according to an embodiment of the present invention.

[0041] Figure 5 is a schematic diagram of the experimental results of the influence of different temperatures on the system stability time according to an embodiment of the present invention. Detailed Description of the Embodiments

[0042] The specific embodiments of the present invention will be described in detail hereinafter with reference to the drawings in an exemplary but not restrictive manner.

[0043] Figure 1Schematic diagram of a dynamic dilution preparation system for a gas reference material according to an embodiment of the present invention. Refer to Figure 1 , the preparation system for the volatile organic compound gas reference material of the present invention may include: a dilution gas source (10), a raw material gas source (20), a plurality of flow meters (30), a humidifying device (40), connecting pipelines, a mixing chamber (50), a temperature and humidity meter (60), a heating device (70). The dilution gas source (10) is connected to the humidifying device (40) via a connecting pipeline through a first flow meter (30-1), and the humidifying device (40) is connected to the mixing chamber (50) via a connecting pipeline; the raw material gas source (20) is connected to the mixing chamber (50) via a connecting pipeline through a second flow meter (30-2); the temperature and humidity meter (60) is connected to the outlet connecting pipeline (51) of the mixing chamber (50); the humidifying device (40), the mixing chamber (50), and the temperature and humidity meter are arranged in the heating device (70).

[0044] More specifically, the dilution gas source (10) is a carrier gas, for example, it can be high-purity nitrogen, hydrogen, helium, etc., and is loaded in a high-pressure gas cylinder as the dilution gas source (10). The dilution gas is decompressed by a first pressure reducing valve 11. For example, according to user requirements, the gas pressure in the high-pressure gas cylinder can be reduced to a specified range. Then it is filtered through a filtering device to further purify the carrier gas. For example, an activated carbon filter 12 and a 5A molecular sieve filtering device 13 can be used for filtering.

[0045] The purified carrier gas flows through the first flow meter (30-1), and then is divided into two gas paths. One path flows through the third flow meter (30-3) and a flow control valve (41) and enters the humidifying device (40) for humidification. The other path flows through the flow control valve (41-2) without humidification. The flow meter can be selected from a mass flow meter, a capillary restrictor, a sonic nozzle flow meter, a laminar flow meter, an electronic needle valve flow meter, etc., and can accurately control and measure the gas flow rate. The flow control valve (41) can be a stop valve, etc., and can be used to adjust the opening and closing degree and the switch of the gas path.

[0046] As Figure 1 shown, a humidifying device 40 is arranged on the humidifying flow path, and flow control valves (41-1, 41-3) can be arranged on the inlet and outlet pipelines of the humidifying device (40), thereby facilitating the control of the humidifying device 40. The humidifying device 40 can be, for example, a bubbler bottle, a nafion humidifying tube, an ultrasonic humidifier, etc. Two series-connected bubbler bottles are shown in the figure, and a water filling port is arranged on the bubbler bottle for facilitating water filling.

[0047] On the non-humidifying flow path, a rotameter 42 can also be arranged. The rotameter is completely emptied and only functions to indicate the flow rate.

[0048] When the dry dilution function is required, the third flowmeter 30-3, the flow control valve 41-1 and the flow control valve 41-3 are closed to shut off the humidification flow path. The carrier gas is restricted in flow rate by the first flowmeter 30-1 and flows through the flow control valve 41-1 and the rotameter 42 at a fixed flow rate. The rotameter is completely emptied and only functions to indicate the flow rate, and then enters the mixing chamber (50).

[0049] When the wet dilution function is required, the first flow control valve 41-1 and the third flow control valve 41-3 are opened. After the carrier gas is restricted in flow rate by the first flowmeter 30-1, it is divided into two paths. One path passes through the third flowmeter 30-3 again to control the flow rate and enters the secondary glass bottle for bubbling to form a gas with a certain humidity, such as a saturated humidity gas; the other path passes through the second flow control valve 41-2 and the rotameter 42 and is mixed with the saturated humidity gas to form a carrier gas with a specific humidity.

[0050] The raw material gas source (20) can be, for example, a high-concentration high-pressure sample gas to be diluted, such as styrene, xylene, formaldehyde, etc. The raw material gas is depressurized by the second pressure reducing valve 21. For example, according to user requirements, the gas pressure in the high-pressure gas cylinder can be reduced to a specified range. Then it is restricted in flow rate by the second flowmeter 30-2 and flows to the mixing chamber 50 at a fixed flow rate. It is diluted and mixed with the above-mentioned carrier gas here to form a sample gas with a specific concentration and a specific humidity. In order to reduce or prevent the adsorption of the gas, the mixing chamber can be a passivated mixing chamber, such as a silanized glass mixing chamber or a 316L passivated mixing chamber.

[0051] The mixed wet gas is divided into two paths. One path is measured for temperature and humidity by the temperature and humidity meter 60 and then emptied. A rotameter 42-2 can also be set in this flow path to indicate the flow rate; the other path enters the sampling device or the analysis device.

[0052] In the dynamic dilution and preparation system of the gas reference material of the present invention, the connecting pipelines between the above-mentioned components can be passivated pipelines, such as silanized glass pipelines or 316L passivated pipelines, thereby reducing or preventing the adsorption of the sample gas.

[0053] Reference attachment Figure 1, the dynamic dilution and preparation system of the gas reference material of the present invention may further include a heating device (70) (shown by a dotted line), and the humidifying device (40), the mixing chamber (50) and the temperature and humidity meter (60) are arranged in the heating device (70). For example, the heating device (70) may be integrally formed as a chamber, and the humidifying device (40), the mixing chamber (50) and the temperature and humidity meter (60) are arranged in this chamber. The heating device (70) can use various heating methods such as air bath heating, heating jacket and resistance wire heating to heat the chamber, so that the humidifying device (40), the mixing chamber (50) and the temperature and humidity meter (60) therein can maintain a predetermined temperature.

[0054] By using the heating device (70), precise adjustment and calculation of humidity at a specific temperature can be achieved, and the humidifying device and the mixing chamber (50) are arranged in the heating device (70), thereby reducing or preventing problems such as adsorption on the inner wall of the gas mixing pool and water condensation.

[0055] The dynamic dilution and preparation system of the gas reference material of the present invention further includes a control module (not shown). For example, the opening and closing of valves and the control of gas flow, temperature and humidity as well as the collection of corresponding data can be realized through control software. Figure 2 It is a schematic diagram of the operation interface of the control software of an embodiment of the present invention. As shown in Reference 2. The set flow rates of each flow meter 30 can be directly input into the corresponding window, and the data is input and the "send" key is clicked for setting. For the heating temperature, the target temperature can be input in the column below "PID temperature", and the "send" key is clicked for setting. When long-term monitoring of the fluctuations of flow rate, gas temperature and humidity is required, the "sampling period" (data collection frequency) and "sampling time" can be set, and the "start" key is clicked for data collection. The results of data collection are updated in real time in the upper right corner of the software interface. When data analysis and processing are required, the "data export" function can be used to convert the collected data into a file recognizable by excel software for analysis.

[0056] In addition, due to the adoption of the heating device (70), the passivation pipeline and the mixing chamber, the system of the present invention can perform a pre-purging step through the "system closed pressure - baking - venting - purging" mode, thereby enabling the system to achieve stability in a short time and greatly improving the system utilization efficiency.

[0057] The following will describe in detail the pre-purging step of the "system closed pressure - baking - venting - purging" mode of the system of the present invention with reference to the accompanying drawings.

[0058] First, a. Use the heating device (70) to heat the humidifying device (40) and the mixing chamber (50) to a predetermined temperature;

[0059] b. Close the outlet of the mixing chamber (50), then open the dilution gas source (10) to increase the pressure in the dilution gas pipeline to a predetermined pressure, for example, slowly increase it to about 10 atmospheres, and then close the dilution gas source (10);

[0060] c. Open the outlet of the mixing chamber (50) to release the pressure.

[0061] d. Repeat steps b - c multiple times, for example, 3 - 5 times, so that the dilution gas pipeline is filled with dilution gas, and then close the dilution gas pipeline;

[0062] e. Close the outlet of the mixing chamber (50), then open the raw material gas source (20) to slowly increase the pressure in the raw material gas pipeline to a predetermined pressure, for example, about 10 atmospheres, and then close the raw material gas source (20);

[0063] f. Open the outlet of the mixing chamber (50) to release the pressure.

[0064] g. Repeat steps e - f multiple times, for example, 3 - 5 times, so that the raw material gas pipeline is filled with raw material gas.

[0065] Then open each flow meter and flow control valves 1 - 3, and set all the flows normally, so that the system can quickly reach a stable state. Then adjust the precise flow and temperature as needed to configure a standard gas with a specific humidity and concentration.

[0066] Due to the use of passivated pipelines and mixing chambers, combined with the cleaning mode of multiple cycles of system closed - pressure - baking - venting - purging, the time for the system to reach stability can be greatly reduced.

[0067] Example 1 - Comparison of the humidification performance of single - stage glass bottles and double - stage glass bottles

[0068] When the ambient temperature is 25 °C and the set gas flow rate is 5 L, the carrier gas humidity at the outlet of the system with single - stage glass bottles and double - stage glass bottles is detected respectively.

[0069] The experimental results of the humidification performance of single - stage and double - stage glass bottles are as Figure 3 shown. When using a single - stage glass bottle for bubbling saturation, the maximum humidification capacity is only 40% R.H., while when using a double - stage glass bottle for bubbling, the maximum humidification capacity can reach 90% R.H.. This shows that after the double - stage glass bottles are connected in series, the humidification capacity of the system is significantly higher than that of the single - stage glass bottle. Therefore, using a double - stage glass bottle for bubbling can greatly improve the humidification efficiency.

[0070] Example 2 - Influence of different mixer materials on the system stability time

[0071] The heating temperature was selected as 28 °C. Styrene in nitrogen at 40 ppm was used as the sample gas (styrene has strong adsorption), and high-purity nitrogen was used as the diluent gas. Mixers made of different materials, namely silica gel, polytetrafluoroethylene, ordinary stainless steel, 316L passivated stainless steel, and silanized glass, were used to investigate the concentration stability of the diluted gas. The target dilution concentration was set at 110.3 ppb. The concentration was measured using an Agilent gas chromatography-mass spectrometry instrument. The chromatographic column was Stable-Wax 30m * 0.32mm * 1.0μm. The analysis was performed in the SCAN full-scan mode, and quantitative integration was performed using the peak area automatic integration mode.

[0072] The experimental results are as Figure 4 shown. From Figure 4 it can be seen that after purging the silica gel mixing pipeline for 150 minutes, the outlet concentration value was only 102.3 ppb and still did not reach stability. The passivated glass pipeline had the shortest purging time to reach stability, only 10 minutes, and the outlet gas concentration was close to 110 ppb; the purging of the 316L passivated stainless steel pipeline was the second, and it took about 20 minutes to reach the 110 ppb concentration level; the time required for ordinary stainless steel and polytetrafluoroethylene to reach 110 ppb was 50 minutes and 110 minutes respectively.

[0073] The time required to reach the stable target dilution concentration of 110 ppb can reflect the adsorption of the material for the target substance. When the adsorption of the material is smaller, the time required to reach the stable target concentration is shorter. From the results, it can be seen that when using the passivated glass pipeline and the 316L passivated stainless steel pipeline, the required purging time is less than 20 minutes. Therefore, using these two materials can significantly improve the dilution efficiency.

[0074] Example 3 - Influence of Different Temperatures on the System Stability Time

[0075] Styrene in nitrogen at 40 ppm was used as the sample gas, the target dilution concentration was set at 110.3 ppb, and 316L passivated stainless steel and silanized glass were used for the experiment.

[0076] The experimental results are as Figure 5 shown. Compared with the data at 28 °C in Figure 4 , increasing the temperature to 50 °C significantly reduced the stability time of the 316L passivated stainless steel system. For the system that originally reached stability after 20 minutes of purging, after only 10 minutes of purging, the concentration had reached the 110 ppb concentration level. The stability time of the passivated glass material was also improved, but not as significantly as that of the 316L passivated stainless steel. Thus, it can be seen that temperature also has an important influence on the stability of the system.

[0077] Example 4 - Temperature, Flow Rate, and Humidity Stability Experiments

[0078] Set the system temperature to 30 °C, record the temperature and humidity at the gas outlet, the flow rates of each flow meter, and calculate the ratio of its experimental standard deviation to the average value to investigate the system stability.

[0079] The experimental results are shown in Table 1 below:

[0080]

[0081] The experimental results show that the volatility of the system flow rate is small, and the maximum relative standard deviation is within 0.016%, indicating that the dilution ratio can be controlled within a stable range. In addition, the relative standard deviations of the gas temperature, humidity, and PID heating temperature are 1.095%, 0.577%, and 0.572% respectively, indicating that the concentration, temperature, and humidity of the dilution gas can be well controlled within the set range during the experimental time.

[0082] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations. In addition, in the description of the present invention, unless otherwise stated, the meaning of "plurality" is two or more.

[0083] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A dynamic dilution and preparation system for gas reference materials, characterized in that, Comprising: A dilution gas source (10), a raw material gas source (20), a plurality of flow meters (30), a humidifying device (40), connecting pipelines, a mixing chamber (50), a temperature and humidity meter (60), a heating device (70), The dilution gas source (10) is connected to the humidifying device (40) via a connecting pipeline through a first flow meter (30-1), The humidifying device (40) is connected to the mixing chamber (50) via a connecting pipeline; The raw material gas source (20) is connected to the mixing chamber (50) via a connecting pipeline through a second flow meter (30-2); The temperature and humidity meter (60) is connected to the outlet connecting pipeline (51) of the mixing chamber (50); The humidifying device (40), the mixing chamber (50) and the temperature and humidity meter are arranged in the heating device (70); Wherein, the mixing chamber is a silanized glass mixing chamber or a 316L passivated mixing chamber; Wherein, the humidifying device (40) is a secondary glass bubbler bottle; Wherein, the connecting pipelines between the components are silanized glass pipelines or 316L passivated pipelines.

2. The dynamic dilution and preparation system for gas reference materials according to claim 1, characterized in that A third flow meter (30-3) is arranged between the first flow meter (30-1) and the humidifying device (40), and a connecting pipeline is led out between the first flow meter (30-1) and the third flow meter (30-3) and connected to the connecting pipeline between the humidifying device (40) and the mixing chamber (50), thereby forming a bypass.

3. The dynamic dilution and preparation system for gas reference materials according to claim 1, wherein It further includes a control module, and the flow meter, the temperature and humidity meter and the heating device are connected to the control module.

4. A method for preparing a gas reference material by using the dynamic dilution preparation system of the gas reference material according to any one of claims 1-3, including a pre-purging step, and the pre-purging step includes: a. Using the heating device (70) to heat the humidifying device (40) and the mixing chamber (50) to a predetermined temperature; b. Closing the outlet of the mixing chamber (50), then opening the dilution gas source (10) to raise the pressure in the dilution gas pipeline to a predetermined pressure, and then closing the dilution gas source (10); c. Opening the outlet of the mixing chamber (50) to release the pressure, d. Repeating steps b-c multiple times to fill the dilution gas pipeline with dilution gas, and then closing the dilution gas pipeline; e. Closing the outlet of the mixing chamber (50), then opening the raw material gas source (20) to raise the pressure in the raw material gas pipeline to a predetermined pressure, and then closing the raw material gas source (20); f. Opening the outlet of the mixing chamber (50) to release the pressure, g. Repeating steps e-f multiple times to fill the raw material gas pipeline with raw material gas; Wherein the method further includes a dynamic dilution preparation step of the gas reference material after the pre-purging step, and the dynamic dilution preparation step includes humidifying the dilution gas by using the humidifying device (40).

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