Method for testing the purity and nitrogen content of a negative pressure steel bottle canned TSA

Abstract

The present application relates to the field of semiconductor material analysis and detection, in particular to a method for testing the purity and nitrogen content of TSA in a negative pressure steel bottle, which first uses a vacuum pump to draw the whole sampling pipeline to a high vacuum state, and then uses high-purity helium to replace the air and residual nitrogen in the pipeline multiple times to create a closed sampling environment free of impurities; the pressure difference between the inside of the negative pressure steel bottle and the vacuum pipeline is used to automatically and smoothly fill the gaseous TSA sample into the quantitative ring of the gas chromatograph without the need for external pressurizing equipment; the gas chromatograph separates the main components of TSA from the nitrogen impurities through a chromatographic column, collects signals through a thermal conductivity detector, and accurately calculates the purity and nitrogen content based on the peak area; after the detection is completed, the residual TSA in the pipeline is discharged into the tail gas system through vacuum extraction and helium purging, which prevents the residual gas from polymerizing and clogging the pipeline, avoids cross contamination of the sample, and ensures the stability of multiple detections.

Description

Technical Field

[0001] This invention relates to the field of semiconductor material analysis and testing, specifically a method for testing the purity and nitrogen content of TSA packaged in a negative pressure steel cylinder. Background Technology

[0002] Trimethylsilylamine (TSA) is a chemical substance that is extremely sensitive to water and air and is widely used in semiconductor thin film deposition processes. To ensure its stability during transportation and use, TSA is usually filled into negative pressure cylinders in gaseous form. To ensure the production of TSA, it is usually necessary to test the purity and nitrogen content of the TSA stored in negative pressure cylinders.

[0003] Currently, the main methods for detecting the purity and nitrogen content of TSA in negative pressure gas cylinders are as follows: In a glove box filled with inert gas, the operator uses a gas sampling needle to extract TSA gas from the negative pressure gas cylinder, then removes the sampling needle and injects it into a gas chromatograph for analysis; at the same time, the gas chromatograph is used to separate the different components in the mixed gas and perform quantitative analysis.

[0004] However, when testing the purity and nitrogen content of TSA packaged in negative pressure cylinders, although the glove box is filled with helium, it cannot be completely sealed and still contains trace amounts of nitrogen. This nitrogen is drawn in by the sampling needle, interfering with the test results and leading to inaccurate TSA purity measurements. Furthermore, during the transfer of the sampling needle from the glove box to the GC equipment, even with a valve on the needle tip, air can still be introduced through the gap between the needle tip and the valve, further contaminating the sample. Additionally, TSA reacts readily with water and oxygen, causing the sampling needle to become clogged almost after each test, requiring frequent cleaning or replacement. Therefore, this paper proposes a method for testing the purity and nitrogen content of TSA packaged in negative pressure cylinders to address these issues. Summary of the Invention

[0005] To overcome the shortcomings of the prior art and solve at least one of the technical problems mentioned in the background art, the present invention proposes a method for testing the purity and nitrogen content of TSA packaged in negative pressure steel cylinders.

[0006] The technical solution adopted by this invention to solve its technical problem is: a method for testing the purity and nitrogen content of TSA packaged in negative pressure steel cylinders, comprising the following steps:

[0007] S1. Set up the detection system: Configure a negative pressure pipeline replacement system, and seal and connect the negative pressure pipeline replacement system to the outlet of the negative pressure TSA cylinder and the gas inlet of the gas chromatograph respectively; the negative pressure pipeline replacement system includes a helium switch valve, a cylinder interface valve, a vacuum gauge interface valve, a vacuum pump interface valve, a tail gas interface valve, a gas inlet interface valve, a pipeline flow regulating valve, a helium flow regulating valve, a vacuum gauge, a vacuum pump, and sealed connecting pipelines;

[0008] S2. Initial state reset: Close all valves, open the pipeline flow regulating valve to the maximum opening, and complete the initial preparation before testing;

[0009] S3. Vacuum Purification of Pipelines: Open the gas cylinder interface valve, vacuum gauge interface valve, vacuum pump interface valve, and gas phase inlet interface valve. Start the vacuum pump to evacuate the entire connecting pipeline. Observe that the vacuum count value stabilizes below 4 Pa ​​and no longer changes. Close the vacuum pump interface valve, open the helium switch valve and helium flow regulating valve, and introduce high-purity helium into the pipeline for purging. Repeat the vacuuming-helium purging operation at least 3 times to thoroughly remove air and residual nitrogen impurities from the pipeline.

[0010] S4. Sample equilibration injection: Close the vacuum gauge interface valve and the vacuum pump interface valve, enter the sample information in the gas chromatograph operating software, and select the valve injection mode; open the cylinder interface valve, let it stand for equilibration for 1 minute, and use the negative pressure difference between the pipeline and the cylinder to allow the TSA gaseous sample to naturally fill the quantitative loop of the gas chromatograph, and then close the cylinder interface valve.

[0011] S5. Chromatographic Detection and Analysis: Start the gas chromatograph and run the detection program. Separate the TSA main component and nitrogen impurity component in the sample through the chromatographic column. Collect the chromatographic signal through the detector and generate the detection spectrum.

[0012] S6. Residual Replacement Treatment in Pipeline: After the test is completed, open the vacuum pump interface valve to extract the residual TSA sample in the pipeline; close the vacuum pump interface valve, open the helium switch valve to introduce high-purity helium to purge the pipeline, and open the tail gas interface valve to discharge the residual gas into the tail gas treatment system; repeat the vacuum extraction-helium purging operation at least 3 times to complete the pipeline purification and wait for the next test.

[0013] S7. Data Processing: Based on the peak area and retention time of the chromatogram, calculate the purity of the TSA product and the nitrogen impurity content using the external standard method to complete the test.

[0014] Preferably, all connecting pipes in the negative pressure pipeline replacement system in S1 use corrosion-resistant stainless steel VCR sealed interfaces, without rubber hose connections, to avoid pipeline adsorption of TSA gas and infiltrated air causing detection interference.

[0015] Preferably, in step S3, the vacuuming time is no less than 2 minutes each time, and the helium replacement purging time is no less than 1 minute, to ensure that the pipeline is completely replaced and there is no residual air.

[0016] Preferably, the gas chromatograph uses a thermal conductivity detector (TCD), the chromatographic conditions are set to isothermal separation mode, and high-purity helium is used as the carrier gas, which is suitable for the accurate separation and quantification of TSA and nitrogen components.

[0017] Preferably, in step S4, the negative pressure difference is used to smoothly fill the TSA gaseous sample into the quantitative loop of the gas chromatograph; after filling is completed, the cylinder interface valve is closed to lock the sample injection volume.

[0018] Preferably, the components separated in S5 sequentially enter a thermal conductivity detector, which converts them into electrical signals to generate a standard chromatographic detection spectrum. The spectrum clearly distinguishes between the nitrogen characteristic peak and the main TSA characteristic peak.

[0019] Preferably, the residual exhaust gas in the pipeline in S6 is uniformly connected to the exhaust gas treatment system to avoid direct emission of harmful TSA gases and improve the safety of the detection operation.

[0020] Preferably, in step S7, the chromatographic spectrum is retrieved, and high-purity standard nitrogen and standard TSA gas are used as references. The peak retention time and peak area are compared using the external standard method to quantitatively calculate the purity of the TSA product and the volume percentage content of nitrogen impurities in this test.

[0021] The advantages of this invention are:

[0022] This invention utilizes the core principles of vacuum displacement impurity removal, automatic negative pressure differential injection, and chromatographic separation for quantification: First, a vacuum pump evacuates the entire sampling pipeline to a high vacuum state, followed by multiple purgings with high-purity helium to completely remove air and residual nitrogen from the pipeline, creating a clean, sealed injection environment free of impurities. Utilizing the pressure difference between the negative pressure cylinder and the vacuum pipeline, the TSA gaseous sample is automatically and stably filled into the gas chromatograph's quantitative loop without the need for external pressurization equipment. The gas chromatograph then separates the TSA main components from the nitrogen impurities using a chromatographic column, followed by thermal conductivity detection. The instrument collects signals and accurately calculates purity and nitrogen content based on peak area. After detection, residual TSA in the pipeline is discharged into the exhaust gas system through vacuum extraction and helium purging to prevent residual gas from agglomerating and clogging the pipeline, while also avoiding sample cross-contamination and ensuring the stability of multiple tests. This achieves the desired effect for testing the purity and nitrogen content of TSA in negative pressure cylinders. It solves the problem that when testing the purity and nitrogen content of TSA in negative pressure cylinders, although the glove box is filled with helium, it cannot be completely sealed and still contains trace amounts of nitrogen. This nitrogen is drawn in by the sampling needle, interfering with the test results and leading to inaccurate TSA purity measurements. Furthermore, during the transfer of the sampling needle from the glove box to the GC equipment, even with a valve on the needle tip, the gap between the needle tip and the valve still allows air to come into contact, further introducing nitrogen and oxygen, causing sample contamination. Additionally, TSA reacts readily with water and oxygen, causing the sampling needle to become clogged almost after each test, requiring frequent cleaning or replacement. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of the present invention;

[0025] Figure 2 This is a schematic diagram of the negative pressure pipeline replacement system of the present invention;

[0026] Figure 3 This is a schematic diagram of a test spectrum example of the chromatographic detection spectrum of the present invention.

[0027] In the diagram: 1. Helium switch valve; 2. Cylinder interface valve; 3. Vacuum gauge interface valve; 4. Vacuum pump interface valve; 5. Tail gas interface valve; 6. Gas phase inlet interface valve; 7. Pipeline flow regulating valve; 8. Helium flow regulating valve. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The following is in conjunction with the appendix Figures 1-2 This application will be described in further detail.

[0030] This application discloses a method for testing the purity and nitrogen content of TSA packaged in negative pressure cylinders:

[0031] Reference Figure 1 A method for testing the purity and nitrogen content of TSA (Total Vapor Absorber) in a negative pressure cylinder, comprising: S1. Setting up a testing system: configuring a negative pressure pipeline replacement system, and sealing and connecting the negative pressure pipeline replacement system to the outlet of the negative pressure TSA cylinder and the gas inlet of the gas chromatograph; the negative pressure pipeline replacement system includes a helium switch valve 1, a cylinder interface valve 2, a vacuum gauge interface valve 3, a vacuum pump interface valve 4, a tail gas interface valve 5, a gas inlet interface valve 6, a pipeline flow regulating valve 7, a helium flow regulating valve 8, a vacuum gauge, a vacuum pump, and sealed connecting pipelines;

[0032] S2. Initial state reset: Close all valves, open the pipeline flow regulating valve 7 to the maximum opening, and complete the initial preparation before testing;

[0033] S3. Vacuum Replacement and Purification of Pipeline: Open cylinder interface valve 2, vacuum gauge interface valve 3, vacuum pump interface valve 4, and gas phase inlet interface valve 6. Start the vacuum pump to evacuate the entire connecting pipeline. Observe that the vacuum count value stabilizes below 4 Pa ​​and no longer changes. Close vacuum pump interface valve 4, open helium switch valve 1 and helium flow regulating valve 8, and introduce high-purity helium into the pipeline for replacement and purging. Repeat the vacuuming-helium replacement operation at least 3 times to thoroughly remove air and residual nitrogen impurities from the pipeline.

[0034] S4. Sample equilibration injection: Close vacuum gauge interface valve 3 and vacuum pump interface valve 4. Enter sample information in the gas chromatograph operating software and select valve injection mode. Open cylinder interface valve 2, let stand for equilibration for 1 minute, and use the negative pressure difference between the pipeline and the cylinder to allow the TSA gaseous sample to naturally fill the quantitative loop of the gas chromatograph. Then close cylinder interface valve 2.

[0035] S5. Chromatographic Detection and Analysis: Start the gas chromatograph and run the detection program. Separate the TSA main component and nitrogen impurity component in the sample through the chromatographic column. Collect the chromatographic signal through the detector and generate the detection spectrum.

[0036] S6. Residual Replacement Treatment in Pipeline: After the test is completed, open the vacuum pump interface valve to extract the residual TSA sample in the pipeline; close the vacuum pump interface valve 4, open the helium switch valve 1 to purge the pipeline with high-purity helium, and open the tail gas interface valve 5 to discharge the residual gas into the tail gas treatment system; repeat the vacuum extraction-helium purging operation at least 3 times to complete the pipeline purification and wait for the next test.

[0037] S7. Data Processing: Based on the peak area and retention time of the chromatogram, calculate the purity of the TSA product and the nitrogen impurity content using the external standard method to complete the test.

[0038] S1. Setting up the detection system

[0039] according to Figure 1 The schematic diagram shown illustrates a negative pressure pipeline replacement system. This system includes: a helium switch valve 1, a gas cylinder interface valve 2, a vacuum gauge interface valve 3, a vacuum pump interface valve 4, a tail gas interface valve 5, a gas phase inlet interface valve 6, a pipeline flow regulating valve 7, a helium flow regulating valve 8, a high-precision vacuum gauge with a range of 0~1000Pa and an accuracy of ±0.5Pa, a diaphragm vacuum pump with an ultimate vacuum of ≤1Pa, and sealed connection pipelines; the main line also includes a pressure reducing valve, one branch line connected to high-purity helium, one tail gas venting line, and one branch line connected to the vacuum pump.

[0040] All connecting pipes use 316L stainless steel VCR sealing interfaces with internal electropolished finish, without any rubber tubing or rubber seals. The VCR interfaces use metal gaskets for surface contact sealing, which can withstand high vacuum and prevent atmospheric penetration, while avoiding TSA gas from coming into contact with organic materials and being adsorbed or reacting.

[0041] Connect the cylinder interface valve 2 to the outlet of the negative pressure TSA cylinder to be tested via a VCR adapter. Connect the gas chromatograph inlet interface valve 6 directly to the gas inlet of the gas chromatograph via a VCR pipeline. The gas chromatograph is equipped with a gas quantitative loop and valve injection system. The gas cylinder containing TSA is under negative pressure. Only by drawing the pipeline to the extreme negative pressure state can the TSA in the cylinder be extracted and sampled for testing.

[0042] S2, Initial State Reset

[0043] Before performing any operations, ensure all valves are closed. Turn the pipeline flow control valve 7 counterclockwise to its maximum opening to ensure there is no throttling resistance inside the pipeline, facilitating subsequent vacuuming and gas flow. This completes the initial preparations before testing.

[0044] S3, Pipeline Vacuum Replacement Purification

[0045] This step aims to thoroughly remove existing air and moisture from the piping system and eliminate background interference.

[0046] First, sequentially open valve 2 (cylinder interface), valve 3 (vacuum gauge interface), valve 4 (vacuum pump interface), and valve 6 (gas phase inlet interface) to start the diaphragm vacuum pump. The vacuum pump will evacuate the entire system through the pipeline. Observe the vacuum count value and continue evacuating for at least 2 minutes. When the vacuum gauge reading drops below 4 Pa ​​and remains stable for 30 seconds without changing, it indicates that the system has reached an absolute vacuum.

[0047] Then, close the vacuum pump interface valve 4, slowly open the helium switch valve 1 and the helium flow regulating valve 8, adjust the helium flow rate, and introduce high-purity helium into the pipeline; keep the helium purging for at least 1 minute to fill the entire pipeline with helium.

[0048] Repeat the above vacuuming and helium purging operation four times. After the last vacuuming, keep the vacuum pump running and observe that the vacuum gauge pressure stabilizes at 2.5 Pa and no longer changes. At this point, the air and residual nitrogen impurities in the pipeline have been completely removed, and the system is in a clean state with high vacuum and no nitrogen background.

[0049] S4, Sample Equilibrium Injection

[0050] Close vacuum gauge interface valve 3 and vacuum pump interface valve 4 to disconnect the vacuum pump from the pipeline system.

[0051] Enter the sample batch number, cylinder number, and other information into the gas chromatograph operating software. Select valve injection mode as the injection method and set the quantitative loop filling time to 30 seconds.

[0052] Slowly open cylinder interface valve 2. Due to the high vacuum state of the pipeline system, and the fact that the internal pressure of the negative pressure TSA cylinder is usually 10~50kPa, there is a significant positive pressure difference. Driven by this pressure difference, the TSA gaseous sample in the cylinder automatically and smoothly flows into the pipeline and fills the GC gas metering loop. Keep cylinder interface valve 2 open and allow it to stand for 1 minute to ensure that the sample gas in the metering loop and each connecting pipeline is uniform and stable.

[0053] Subsequently, the cylinder interface valve 2 is closed to lock the sample gas in the metering loop, thus completing the precise locking of the injection volume.

[0054] S5, Chromatographic Detection and Analysis

[0055] Start the gas chromatograph's operating program to perform detection and analysis; the gas chromatograph model is Agilent 8890.

[0056] In this embodiment, a thermal conductivity detector is used in the gas chromatograph, and the chromatographic conditions are set as follows:

[0057] Separation mode: Start at 40℃ and hold for 1 min, increase to 65℃ at a rate of 5℃ / min and hold for 1 min, then increase to 120℃ at a rate of 10℃ / min and hold for 1 min, then increase to 200℃ at a rate of 20℃ / min and hold for 2 min.

[0058] Chromatographic column: 5A molecular sieve capillary column, specifically designed for the separation of N2 and silanes, with a flow rate of 3 mL / min.

[0059] Detector temperature: 250℃.

[0060] Inlet temperature: 220℃.

[0061] Inlet pressure: 12.529 psi.

[0062] Inlet split ratio: 30:1.

[0063] Injection volume: 1 μL.

[0064] Carrier gas: high-purity helium, flow rate 5.0 mL / min.

[0065] Reference gas flow rate: 20 mL / min.

[0066] Under program control, the valve injection system automatically delivers the sample from the quantitative loop into the chromatographic column. The components in the sample separate within the column due to differences in their interaction with the stationary phase, flowing out sequentially and into the TCD detector. The TCD detector utilizes the difference in thermal conductivity between the components and the carrier gas to convert the concentration signal into an electrical signal, generating a standard chromatographic detection spectrum.

[0067] S6, Pipeline Residual Replacement Treatment

[0068] After the sample analysis is completed, a small amount of TSA sample may remain in the tubing and metering loop. This must be treated to prevent corrosion, blockage, and safety risks.

[0069] First, open vacuum pump interface valve 4, start vacuum pump, and evacuate the pipeline and metering loop for 2 minutes to remove residual TSA sample.

[0070] Then, close the vacuum pump interface valve 4, open the helium switch valve 1 and the helium flow regulating valve 8, and purge the pipeline with high-purity helium for 1 minute. Next, open the tail gas interface valve 5 and discharge the purged residual gas into the tail gas treatment system through a dedicated pipeline; the tail gas treatment system is a scrubbing tower filled with activated carbon and alkaline absorbent, which can effectively adsorb and neutralize TSA harmful gases, avoiding direct emissions that could cause environmental pollution or personal injury.

[0071] Keep exhaust gas inlet valve 5 open for 5 seconds, then close it. Repeat the above vacuum extraction → helium purging → exhaust gas emission operation a total of 4 times to ensure that there is no TSA residue in the pipeline and metering loop; finally, turn off the vacuum pump and all valves, and the system returns to standby mode, waiting for the next test.

[0072] S7, Data Processing

[0073] After the detection is completed, the chromatographic detection spectrum saved in the gas chromatography software is retrieved; in a typical spectrum, a nitrogen characteristic peak appears at a retention time of about 1.2 minutes, and a TSA main characteristic peak appears at a retention time of about 3.5 minutes. The resolution between the two peaks is R≥1.5, which meets the quantitative requirements.

[0074] Quantitative calculations were performed using the external standard method.

[0075] Standard curve establishment: A series of standard mixed gases with concentration gradients were prepared in advance using high-purity standard nitrogen and high-purity standard TSA gas. The mixtures were injected and analyzed under the same chromatographic conditions, and the peak areas of each mixture were recorded to plot the concentration-peak area standard curve.

[0076] Sample quantification: Substitute the sample nitrogen peak area and TSA main peak area measured in this embodiment into the corresponding standard curve regression equation to calculate the volume purity of the TSA product and the volume percentage content of nitrogen impurities in this test.

[0077] Working principle: Normally, samples are pushed into the quantitative loop by their own pressure when the valve is opened. However, this invention targets TSA gaseous samples in negative pressure cylinders. It establishes a negative pressure pipeline replacement system and uses a vacuum pump to pre-evacuate the entire pipeline and GC injection system to absolute vacuum. At this point, the pressure inside the pipeline system is much lower than the pressure inside the negative pressure cylinder, creating a significant pressure difference. When the cylinder interface valve 2 is opened, the TSA sample gas automatically and smoothly flows from the cylinder to the pipeline under the pressure difference and naturally fills the quantitative loop of the gas chromatograph. This achieves active aspiration injection of negative pressure samples, avoiding the contamination risks associated with external pressurization or manual injection.

[0078] To completely eliminate the influence of existing air and moisture in the pipeline on the test results, this invention employs a purification strategy of repeated "vacuuming-helium filling" cycles. The principle is as follows: vacuuming mechanically removes most gas molecules from the pipeline; subsequently, high-purity helium is introduced, utilizing its strong diffusivity and chemical inertness to displace and dilute residual nitrogen, oxygen, and moisture adsorbed on the pipeline wall; during the next vacuuming cycle, these diluted impurities are discharged with the gas flow. After at least three cycles, the residual concentration of interfering substances such as nitrogen in the pipeline can be reduced to 10⁻⁻⁶. 6 This reduces the background signal to below the detection limit, ensuring that the measured nitrogen signal originates entirely from the TSA cylinder sample itself.

[0079] After the TSA sample and nitrogen impurities enter the gas chromatography system via a quantitative loop, they pass through the column propelled by the carrier gas. Due to the difference in adsorption / partition coefficients between TSA and nitrogen molecules on the stationary phase, their migration rates within the column differ, thus achieving separation: nitrogen, as a small molecule permanent gas, elutes first, followed by TSA. The eluates sequentially enter a thermal conductivity detector (TCD). The TCD utilizes the temperature-dependent resistance change of a tungsten filament or thermistor. When pure carrier gas flows through, the thermal conductivity remains constant, resulting in a stable baseline. When the sample components are mixed with the carrier gas, the thermal conductivity of the mixed gas changes, causing a change in the temperature and resistance of the thermistor, resulting in chromatographic peaks on the recorder. Because helium has a much higher thermal conductivity than nitrogen and TSA, the chromatographic peaks are aligned and the response is sensitive. By analyzing peak area and retention time, combined with the external standard method, the nitrogen impurity content and TSA purity can be accurately quantified.

[0080] After testing, a small amount of highly reactive TSA gas may remain in the pipeline and metering loop. Direct discharge of this gas could corrode equipment, pollute the environment, and endanger personnel safety. This invention employs a cyclical treatment method of "vacuuming-helium purging-exhaust gas discharge": First, a vacuum is drawn to remove most of the free TSA; then, helium is introduced to displace the adsorbed TSA; finally, the exhaust gas valve 5 is opened to discharge the TSA-containing mixed gas into a dedicated exhaust gas treatment system. After multiple cycles, the residual TSA level in the pipeline is reduced to below the safe threshold, protecting the cleanliness of subsequent tests and achieving green and safe production.

[0081] The above steps constitute a complete technical closed loop: pipeline purification to eliminate background interference, negative pressure injection to solve the problem of sample introduction, chromatographic separation and detection to achieve accurate quantification of components, and system cleaning to ensure safety and repeatability. This method completely avoids the inherent defects of the traditional glove box-injection needle mode, such as unavoidable air introduction, needle blockage, and nitrogen background interference, and achieves high-precision, high-safety, and high-efficiency detection of negative pressure cylinder TSA products.

[0082] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for testing the purity and nitrogen content of TSA packaged in negative pressure steel cylinders, characterized in that: Includes the following steps: S1. Set up the detection system: Configure a negative pressure pipeline replacement system and seal and connect the negative pressure pipeline replacement system to the outlet of the negative pressure TSA cylinder and the gas inlet of the gas chromatograph respectively; the negative pressure pipeline replacement system includes a helium switch valve (1), a cylinder interface valve (2), a vacuum gauge interface valve (3), a vacuum pump interface valve (4), a tail gas interface valve (5), a gas inlet interface valve (6), a pipeline flow regulating valve (7), a helium flow regulating valve (8), a vacuum gauge, a vacuum pump and sealed connecting pipelines; S2. Initial state reset: Close all valves, open the pipeline flow regulating valve (7) to the maximum opening, and complete the initial preparation before testing; S3. Vacuum replacement and purification of pipeline: Open the cylinder interface valve (2), vacuum gauge interface valve (3), vacuum pump interface valve (4), and gas phase inlet interface valve (6), start the vacuum pump to evacuate the entire set of connecting pipelines, and observe that the vacuum count value stabilizes below 4Pa and no longer changes; close the vacuum pump interface valve (4), open the helium switch valve (1) and helium flow regulating valve (8), and introduce high-purity helium into the pipeline for replacement and purging; repeat the vacuuming and helium replacement operation at least 3 times to thoroughly remove air and residual nitrogen impurities in the pipeline; S4. Sample equilibration injection: Close the vacuum gauge interface valve (3) and the vacuum pump interface valve (4), enter the sample information in the gas chromatograph operating software, and select the valve injection mode; open the cylinder interface valve (2), let it stand for equilibration for 1 minute, and use the negative pressure difference between the pipeline and the cylinder to allow the TSA gaseous sample to naturally fill the quantitative loop of the gas chromatograph, and then close the cylinder interface valve (2). S5. Chromatographic Detection and Analysis: Start the gas chromatograph and run the detection program. Separate the TSA main component and nitrogen impurity component in the sample through the chromatographic column. Collect the chromatographic signal through the detector and generate the detection spectrum. S6. Residual replacement treatment in pipeline: After the test is completed, open the vacuum pump interface valve to extract the residual TSA sample in the pipeline; close the vacuum pump interface valve (4), open the helium switch valve (1) to purge the pipeline with high-purity helium, open the tail gas interface valve (5) to discharge the residual gas into the tail gas treatment system; repeat the vacuum extraction-helium purging operation at least 3 times to complete the pipeline purification and wait for the next test. S7. Data Processing: Based on the peak area and retention time of the chromatogram, calculate the purity of the TSA product and the nitrogen impurity content using the external standard method to complete the test.

2. The method for testing the purity and nitrogen content of TSA bottled in a negative pressure cylinder according to claim 1, characterized in that: The negative pressure pipeline replacement system in S1 uses corrosion-resistant stainless steel VCR sealed interfaces for all connecting pipelines, with no rubber hose connections, to avoid pipeline adsorption of TSA gas and infiltrated air causing detection interference.

3. The method for testing the purity and nitrogen content of TSA bottled in a negative pressure cylinder according to claim 1, characterized in that: In step S3, each vacuuming process lasts no less than 2 minutes, and the helium purging process lasts no less than 1 minute, to ensure that the pipeline is completely purged without any residual air.

4. The method for testing the purity and nitrogen content of TSA bottled in a negative pressure cylinder according to claim 1, characterized in that: The gas chromatograph uses a thermal conductivity detector (TCD), and the chromatographic conditions are set to isothermal separation mode. High-purity helium is used as the carrier gas, which is suitable for the precise separation and quantification of TSA and nitrogen components.

5. The method for testing the purity and nitrogen content of TSA bottled in a negative pressure cylinder according to claim 1, characterized in that: In step S4, the negative pressure difference is used to smoothly fill the TSA gaseous sample into the quantitative loop of the gas chromatograph; after filling, the cylinder interface valve (2) is closed to lock the sample injection volume.

6. The method for testing the purity and nitrogen content of TSA bottled in a negative pressure cylinder according to claim 1, characterized in that: The components separated in S5 enter the thermal conductivity detector in sequence, which converts them into electrical signals to generate a standard chromatographic detection spectrum. The nitrogen characteristic peak and the TSA main characteristic peak can be clearly distinguished in the spectrum.

7. The method for testing the purity and nitrogen content of TSA bottled in a negative pressure cylinder according to claim 1, characterized in that: The residual exhaust gas in the S6 pipeline is uniformly connected to the exhaust gas treatment system to avoid direct emission of harmful TSA gases and improve the safety of the detection operation.

8. The method for testing the purity and nitrogen content of TSA bottled in a negative pressure cylinder according to claim 1, characterized in that: In step S7, the chromatographic spectrum is retrieved, and high-purity standard nitrogen and standard TSA gas are used as references. The peak retention time and peak area are compared using the external standard method, and the purity of the TSA product and the volume percentage of nitrogen impurities in this test are quantitatively calculated.

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