SVOC semi-volatile matter enrichment method and sample introduction device

Abstract

The invention is suitable for the technical field of environmental monitoring and analysis, and provides an SVOC semi-volatile matter enrichment method and a sample introduction device, the enrichment method comprises the following steps: loading a sample containing SVOC into a sample tube, and sealing the sample tube; injecting a solvent into the sample tube, heating to 50-500 DEG C, and promoting SVOC desorption by using the steam pressure of the solvent; purging desorption substances to a liquid nitrogen cold trap by using inert gas, controlling the temperature of the liquid nitrogen cold trap to be-196 to-20 DEG C, and enriching SVOC; the liquid nitrogen cold trap is heated to 200-550 DEG C, the total SVOC is transferred to a detection instrument for analysis, SVOC semi-volatile matters adsorbed by the sample tube are more easily desorbed under the working conditions of high temperature and solvent vapor pressure, desorption sample introduction analysis only needs 10-20 minutes, and no sample is transferred; according to the analysis mode, all SVOC semi-volatile matters adsorbed by the tube are fed, and compared with the prior art, the detection sensitivity is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental monitoring and analysis, and particularly relates to a method for enriching SVOC semi-volatile substances and a sampling device. Background Art

[0002] SVOC is an organic compound that usually exists in the indoor environment. They are semi-volatile, which means that they can volatilize into gases at normal temperature, and at the same time, they will also deposit on the solid surface or sediment under certain conditions. The boiling point of SVOC ranges from 240°C to 400°C, with both gas-phase and particle-phase characteristics, and has long-term potential hazards to health.

[0003] The common methods for collecting SVOC in the air are: solid adsorbent method and filter membrane method. After extraction and elution with organic solvents, it is then concentrated to a volume of 1 ml.

[0004] The common enrichment method for SVOC in water is: after solid-phase extraction and elution with organic solvents, it is then concentrated to a volume of 1 ml.

[0005] The common enrichment method for SVOC in solids is: after Soxhlet extraction or high-pressure solvent extraction, it is then concentrated to a volume of 1 ml.

[0006] The existing SVOC enrichment technologies mainly rely on methods such as solid-phase extraction and Soxhlet extraction. After elution with organic solvents and concentration to a small volume, they are then sampled and analyzed. The following defects exist: Large solvent consumption: After elution, the solvent volume reaches 60 - 250 ml, and it needs to be concentrated to 1 ml by nitrogen blowing or parallel concentration. The process is cumbersome and vulnerable to contamination; Low efficiency: The traditional method takes more than 2 hours, and multiple sample transfers result in errors; Insufficient sensitivity: Only 1 μL of the concentrated solution is sampled, and the actual detected amount is only one-thousandth of the original sample, with limited sensitivity.

[0007] The present invention aims to provide a method and device for enriching and sampling SVOC with high efficiency, low solvent consumption, and high sensitivity. Summary of the Invention

[0008] The present invention provides a method for enriching SVOC semi-volatile substances, aiming to solve the above problems.

[0009] The present invention is implemented as follows. A method for enriching SVOC semi-volatile substances includes the following steps: Load the sample containing SVOC into a sample tube and seal it; Inject a solvent into the sample tube and heat it to 50 - 300°C, and use the solvent vapor pressure to promote the desorption of SVOC; Purge the desorbed substances with an inert gas into a liquid nitrogen cold trap, and control the temperature of the liquid nitrogen cold trap to be -196 - -20°C to enrich SVOC; The liquid nitrogen cold trap is heated to 200 - 550 °C, and all SVOCs are transferred to the detection instrument for analysis.

[0010] Preferably, the sample tube is made of 316 stainless steel and can withstand a temperature of ≥500 °C.

[0011] Preferably, the solvent injection flow rate is 10 - 2000 μL / min.

[0012] Preferably, the solvent includes methanol, acetone, and n - hexane.

[0013] Preferably, the inert gas is nitrogen, and the purge flow rate is 10 - 500 mL / min.

[0014] Preferably, the temperature control range of the liquid nitrogen cold trap is - 196 - 550 °C, and the heating rate is 10 - 50 °C / s.

[0015] The present invention also provides a sampling device for implementing the above - mentioned SVOC semi - volatile enrichment method, comprising: A sample heating inlet - outlet mechanism, which includes an autosampler and a heating component. The autosampler is used to place a plurality of sample tubes sealed at both ends with upper - machine analysis caps and can adjust the position of the sample tubes. The heating component is used to heat the sample tubes after injecting the solvent; A solvent addition unit for injecting solvent into the sample tubes; A liquid nitrogen cold trap for enriching SVOCs; A purge unit for purging and transferring SVOCs in the sample tubes to the liquid nitrogen cold trap; An injection valve switching system for switching the enrichment and injection paths.

[0016] Preferably, the autosampler includes a sample tray, a driving mechanism, and a control module. The sample tray is used to place a plurality of sample tubes sealed at both ends with upper - machine analysis caps. The driving mechanism is used to drive the sample tray to rotate. The control module is electrically connected to the driving mechanism to control the rotation of the sample tray. During operation, first, the two ends of the sample tubes are sealed with upper - machine analysis caps and placed on the sample tray of the autosampler. By controlling the rotation position of the sample tray, the selected sample for analysis is chosen to achieve automatic sampling and analysis.

[0017] Preferably, the solvent addition unit includes a plurality of solvent bottles, an electronic pressure controller, and a solvent selection valve. The plurality of solvent bottles are used to contain different solvents. The electronic pressure controller is used to control the pressure in the solvent bottles. The solvent selection valve is used to select different solvents to be added. The solvent selection valve is connected to a lower - piercing needle flow path, and the lower - piercing needle flow path can be communicated with the bottom of the sample tube through a lower - piercing needle. A sixth direct - current solenoid valve is provided between the solvent selection valve and the lower - piercing needle flow path. The N input in multiple solvent bottles2 When the pressure is applied and the solvent selection valve (multi-way valve) is switched to the addition position, under the action of air pressure, the solvent flows through the solvent selection valve (multi-way valve) into the lower needle insertion flow path, and then enters the sample tube from the bottom of the sample tube. The flow rate can be adjusted by regulating the pressure in the solvent bottle. The higher the pressure in the solvent bottle, the faster the flow rate. The on-off time of the solvent selection valve and the solvent flow path is set to control the volume of the solvent added to the sample tube.

[0018] Preferably, the heating assembly includes a heating element and a telescopic structure, and the telescopic structure is used to drive the heating element to extend or retract, and when extended, it can heat the sample tube.

[0019] Preferably, the liquid nitrogen cold trap includes a liquid nitrogen tank, a liquid nitrogen flow controller, an ultra-low temperature trapping trap, and a low-voltage high-current heating controller. The liquid nitrogen tank is connected to the liquid nitrogen inlet of the ultra-low temperature trapping trap, and a liquid nitrogen solenoid valve and a liquid nitrogen flow controller are sequentially installed on the connecting flow path between the two. The low-voltage high-current heating controller is connected to the ultra-low temperature trapping trap.

[0020] Preferably, the ultra-low temperature trapping trap includes a housing, an inert trapping tube, and a temperature sensor. The inert trapping tube is installed in the housing. The inert trapping tube is a 1 / 16-inch inertized empty tube, which enriches SVOC samples under liquid nitrogen low-temperature conditions. Both ends of the inert trapping tube are connected to the injection valve switching system through a first flow path. The first flow path is the sample inlet and outlet flow path. The temperature sensor is installed at the bottom of the inert trapping tube to monitor the temperature of the inert trapping tube. Heating joints are respectively installed at both ends of the inert trapping tube, and a liquid nitrogen inlet and a liquid nitrogen outlet that are connected to each other are provided on the housing.

[0021] Preferably, the injection valve switching system includes a six-port injection valve, which is provided with a first port, a second port, a third port, a fourth port, a fifth port and a sixth port. Both ends of the inert trapping tube of the liquid nitrogen cold trap are connected to the first port and the fourth port of the six-port injection valve through a first flow path respectively. The second port is connected to the chromatographic carrier gas flow path. The third port is connected to the chromatographic injection port. The fifth port is connected to the upper needle insertion flow path, and the upper needle insertion flow path can be communicated with the top of the sample tube through an upper needle. A second flow path is connected to the sixth port, and the end of the second flow path far from the sixth port is a vent outlet. A second direct current solenoid valve is installed on the second flow path. A third flow path and a fourth flow path are respectively connected to both sides of the second direct current solenoid valve on the second flow path. The other end of the third flow path is connected to the lower needle insertion flow path, and a third direct current solenoid valve is installed on the third flow path. The fourth flow path is connected to the fifth flow path, and the fifth flow path is connected to the lower needle insertion flow path. A fourth direct current solenoid valve is installed on the fourth flow path. The end of the fifth flow path far from the lower needle insertion flow path is a nitrogen input port. A pressure stabilizing valve, an electronic flow controller and a first direct current solenoid valve are sequentially installed on the fifth flow path. The joint of the fourth flow path and the fifth flow path is located between the electronic flow controller and the first direct current solenoid valve. A sixth flow path is connected to the part of the fifth flow path between the pressure stabilizing valve and the electronic flow controller. The other end of the sixth flow path is connected to a solvent bottle. A fifth direct current solenoid valve and an electronic pressure controller are installed on the sixth flow path. A seventh flow path for pressure relief is connected to the part of the sixth flow path between the fifth direct current solenoid valve and the electronic pressure controller. A seventh direct current solenoid valve is installed on the seventh flow path, and one end of the seventh flow path is a pressure relief port.

[0022] Preferably, the injection device further includes a bidirectional flat gasket extrusion sealing device for tightly pressing the upper machine analysis cap in both directions, and the upper and lower flat gaskets are sealed with the upper machine analysis cap.

[0023] Compared with the prior art, the embodiments of the present application mainly have the following beneficial effects: The SVOC semi-volatile substances adsorbed by the sample tube are more likely to be desorbed under high temperature and solvent vapor pressure conditions. The desorption injection analysis only takes 10 - 20 minutes without sample transfer. The traditional extraction method takes more than 1 hour, and it also takes 1 hour to concentrate to 1 ml after extraction, and the sample needs to be transferred at least 2 times.

[0024] This analysis method injects all the SVOC semi-volatile substances adsorbed by the tube. Currently, the extraction - concentration - liquid injection method adopted in the market only injects 1 μl of the 1 ml concentrated solution into the gas chromatography - mass spectrometry for analysis. The detection sensitivity of this method is increased by about 1000 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic structural diagram of an injection device provided by the present invention.

[0026] Figure 2 It is a schematic structural diagram of the liquid nitrogen cold trap provided by the present invention.

[0027] Figure 3 It is a schematic internal structure diagram of the ultra-low temperature trapping trap provided by the present invention.

[0028] Annotation of reference numerals: 1. Sampling six-way valve; 2. Liquid nitrogen cold trap; 3. Bidirectional flat gasket extrusion sealing device; 4. Sample heating inlet and outlet mechanism; 5. Solvent selection valve; 6. Electronic pressure controller; 7. Electronic flow controller; 8. Pressure stabilizing valve; 9. Liquid nitrogen tank; 10. Liquid nitrogen solenoid valve; 11. Liquid nitrogen flow controller; 12. Ultra-low temperature trapping trap; 13. Low-voltage high-current heating controller; 14. Housing; 15. Heating joint; 16. Liquid nitrogen inlet; 17. Liquid nitrogen outlet; 18. Inert trapping tube; 19. Temperature sensor; 100. First flow path; 101. Chromatographic injection port; 102. Chromatographic carrier gas flow path; 103. Vent outlet; 104. Nitrogen input port; 105. Pressure relief port; 200. Second flow path; 300. Third flow path; 400. Fourth flow path; 500. Fifth flow path; 600. Sixth flow path; 700. Seventh flow path. Detailed implementation manners

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the specification and claims of this application or the above drawings are used to distinguish different objects and not to describe a specific order.

[0030] Reference to "embodiment" herein means that a specific feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0031] Embodiment 1 The embodiment of the present invention provides a method for enriching SVOC semi-volatile substances, including the following steps: 1. Load solid adsorbents, filter membranes, and solid particles enriched in gas or liquid samples into a dedicated 316 stainless steel sample tube; 2. The two ends of the sample tube are connected and sealed with the analysis caps for machine use, and it can be placed on the sample tray of the auto-sampler. By controlling the rotation position of the sample tray, the sample to be analyzed is selected to achieve auto-sampling analysis; 3. Solvent addition: The electronic pressure controller 6 of the solvent bottle controls the pressure in the solvent bottle. The solvent selection valve can select different solvents for addition. By controlling the time when the solvent is in communication with the flow path, the volume of the solvent added into the sample tube is controlled. The higher the pressure in the solvent bottle, the faster the flow rate. The solvents include but are not limited to methanol, acetone, and n-hexane; 4. A heating component is provided. When heating is required, it mechanically extends to heat the sample tube and retracts after heating; 5. Purge and concentrate the sample to the liquid nitrogen cold trap; 6. By controlling the liquid nitrogen solenoid valve 10 and the liquid nitrogen flow controller 11, the enrichment temperature of the inert trap tube 18 is controlled. The inert trap tube 18 is a 1 / 16-inch inertized empty tube without adsorption packing. Different boiling point SVOC components are enriched by adjusting different temperatures. The boiling points of common solvents are very low, generally -80 to 50 °C, and the inert trap tube 18 cannot trap them; 7. Sampling valve switching system: Used to switch between enrichment / sampling. When sampling, the inert trap tube 18 of the liquid nitrogen cold trap is heated. The motor of the six-port sampling valve 1 rotates for switching, and the chromatographic carrier gas transfers all the SVOC components enriched in the inert trap tube 18 to the chromatographic injection port for analysis and detection.

[0032] Among them, the material of the sample tube is 316 stainless steel, with a temperature resistance of ≥500 °C. The heating temperature of the sample tube is 50 °C. The injection flow rate of the solvent is 10 μL / min. The inert gas is nitrogen, the purge flow rate is 10 mL / min, the purge time is 15 min. The temperature control range of the liquid nitrogen cold trap is -196 to 550 °C. Specifically, the low-temperature enrichment temperature of the liquid nitrogen cold trap is -196 °C, the heating and desorption temperature of the liquid nitrogen cold trap during sampling is 200 °C, the heating rate is 10 °C / s, and the sampling time is 600 seconds.

[0033] Example 2 The embodiment of the present invention provides a method for enriching SVOC semi-volatile substances, including the following steps: 1. Load the solid adsorbent, filter membrane, and solid particles enriched in the gas or liquid sample into a dedicated 316 stainless steel sample tube; 2. The two ends of the sample tube are connected and sealed with the analysis caps for machine use, and it can be placed on the sample tray of the auto-sampler. By controlling the rotation position of the sample tray, the sample to be analyzed is selected to achieve auto-sampling analysis; 3. Solvent addition: The electronic pressure controller 6 of the solvent bottle controls the pressure in the solvent bottle. The solvent selection valve can select different solvents for addition. By controlling the time when the solvent is in communication with the flow path, the volume of the solvent added to the sample tube is controlled. The higher the pressure in the solvent bottle, the faster the flow rate. The solvents include but are not limited to methanol, acetone, and n-hexane; 4. A heating component is provided, which mechanically extends when heating is required to heat the sample tube and retracts after heating; 5. Purge and concentrate the sample into the liquid nitrogen cold trap; 6. By controlling the liquid nitrogen solenoid valve 10 and the liquid nitrogen flow controller 11, the enrichment temperature of the inert trap 18 is controlled. The inert trap 18 is a 1 / 16-inch inertized empty tube without adsorption packing. Different boiling point SVOC components are enriched by adjusting different temperatures. The boiling points of common solvents are very low, generally -80 to 50 °C, and the inert trap 18 cannot trap them; 7. Injection valve switching system: Used to switch between enrichment / injection. When injecting, the inert trap 18 of the liquid nitrogen cold trap is heated. The motor of the injection six-way valve 1 rotates for switching, and the chromatographic carrier gas transfers all the SVOC components enriched in the inert trap 18 to the chromatographic injection port for analysis and detection.

[0034] Among them, the material of the sample tube is 316 stainless steel, with a temperature tolerance of ≥500 °C. The heating temperature of the sample tube is 270 °C. The injection flow rate of the solvent is 1000 μL / min. The inert gas is nitrogen, the purge flow rate is 250 mL / min, the purge time is 15 min. The temperature control range of the liquid nitrogen cold trap is -196 to 550 °C. Specifically, the low-temperature enrichment temperature of the liquid nitrogen cold trap is -100 °C, the heating and desorption temperature of the liquid nitrogen cold trap during injection is 360 °C, the heating rate is 30 °C / s, and the injection time is 600 seconds.

[0035] Example 3 The embodiment of the present invention provides a method for enriching SVOC semi-volatile substances, including the following steps: 1. Load the solid adsorbent, filter membrane, and solid particles enriched in the gas or liquid sample into a dedicated 316 stainless steel sample tube; 2. Seal the two ends of the sample tube with an upper machine analysis cap and place it on the sample tray of the automatic sampler. By controlling the rotation position of the sample tray, the selected sample for analysis is selected to achieve automatic injection analysis; 3. Solvent addition: The electronic pressure controller 6 of the solvent bottle controls the pressure in the solvent bottle. The solvent selection valve can select different solvents for addition. By controlling the time when the solvent is in communication with the flow path, the volume of the solvent added to the sample tube is controlled. The higher the pressure in the solvent bottle, the faster the flow rate. The solvents include but are not limited to methanol, acetone, and n-hexane; 4. A heating component is provided, which mechanically extends when heating is required to heat the sample tube and retracts after heating; 5. Purge and concentrate the sample into a liquid nitrogen cold trap; 6. By controlling the liquid nitrogen solenoid valve 10 and the liquid nitrogen flow controller 11, control the enrichment temperature of the inert trapping tube 18. The inert trapping tube 18 is a 1 / 16-inch inertized empty tube without adsorption packing. Different SVOC components with different boiling points are enriched by adjusting different temperatures. The boiling points of common solvents are very low, generally -80 to 50 °C, and the inert trapping tube 18 cannot trap them; 7. Injection valve switching system: used to switch between enrichment / injection. When injecting, heat the inert trapping tube 18 of the liquid nitrogen cold trap. The motor of the injection six-way valve 1 rotates and switches. The chromatographic carrier gas transfers all the SVOC components enriched in the inert trapping tube 18 to the chromatographic injection port for analysis and detection.

[0036] Among them, the material of the sample tube is 316 stainless steel, with a temperature tolerance of ≥500 °C. The heating temperature of the sample tube is 500 °C. The injection flow rate of the solvent is 2000 μL / min. The inert gas is nitrogen. The purge flow rate is 500 mL / min, and the purge time is 15 min. The temperature control range of the liquid nitrogen cold trap is -196 to 550 °C. Specifically, the low-temperature enrichment liquid nitrogen cold trap temperature is -20 °C, the desorption temperature of the liquid nitrogen cold trap is 550 °C, the heating rate is 50 °C / s, and the injection time is 600 seconds.

[0037] Example 4 The embodiment of the present invention also provides an injection device for implementing the SVOC semi-volatile enrichment method described in Embodiments 1-3, as Figures 1 - 3 shown, including: Sample heating inlet and outlet mechanism 4, which includes an autosampler and a heating component. The autosampler is used to place multiple sample tubes sealed at both ends with upper machine analysis caps and can adjust the position of the sample tubes. The heating component is used to heat the sample tubes after injecting the solvent; Solvent addition unit, used to inject solvent into the sample tubes; Liquid nitrogen cold trap 2, used to enrich SVOC; Purge unit, used to purge and transfer the SVOC in the sample tubes to the liquid nitrogen cold trap 2; Injection valve switching system, used to switch the enrichment and injection paths.

[0038] Among them, the autosampler includes a sample tray, a driving mechanism, and a control module. The sample tray is used to place multiple sample tubes sealed at both ends with upper machine analysis caps. The driving mechanism is used to drive the sample tray to rotate. The control module is electrically connected to the driving mechanism to control the rotation of the sample tray. The sample tubes are sealed at both ends with upper machine analysis caps and placed on the sample tray of the autosampler. By controlling the rotation position of the sample tray, the selected sample for analysis is realized, and automatic injection analysis is achieved.

[0039] Preferably, the solvent addition unit includes a plurality of solvent bottles, an electronic pressure controller 6, and a solvent selection valve 5. The plurality of solvent bottles are used to contain different solvents. The electronic pressure controller 6 is used to control the pressure in the solvent bottles. The solvent selection valve 5 is used to select different solvents to be added. The solvent selection valve 5 is connected to a lower needle flow path, and the lower needle flow path can be communicated with the bottom of the sample tube through a lower needle. A sixth direct current solenoid valve (DC6) is provided between the solvent selection valve and the lower needle flow path. N is input and set in a plurality of solvent bottles 2 Under pressure, the solvent selection valve 5 (multi-way valve) is switched to the addition position, and the sixth direct current solenoid valve (DC6) is opened. Under the action of air pressure, the solvent flows into the lower needle flow path through the solvent selection valve 5 (multi-way valve), and then enters the sample tube from the bottom of the sample tube. Adjusting the pressure in the solvent bottle can adjust the flow rate. The higher the pressure in the solvent bottle, the faster the flow rate. The on-off time of the solvent selection valve and the solvent flow path is set to control the volume of the solvent added to the sample tube.

[0040] Further, the heating component includes a heating element and a telescopic structure. The telescopic structure is used to drive the heating element to extend or retract, and can heat the sample tube when extending.

[0041] In this embodiment, the liquid nitrogen cold trap 2 includes a liquid nitrogen tank 9, a liquid nitrogen flow controller 11, a cryogenic trap 12, and a low-voltage high-current heating controller 13. The liquid nitrogen tank 9 is connected to the liquid nitrogen inlet 16 of the cryogenic trap 12. A liquid nitrogen solenoid valve 10 and a liquid nitrogen flow controller 11 are sequentially installed on the connection flow path between the two. A first flow path 100 is connected to the cryogenic trap 12. The first flow path 100 is a sample inlet and outlet flow path. The low-voltage high-current heating controller 13 is connected to the cryogenic trap 12.

[0042] In a specific implementation, the cryogenic trap 12 includes a housing 14, an inert trap tube 18, and a temperature sensor 19. The inert trap tube 18 is installed in the housing 14. The inert trap tube 18 is a 1 / 16-inch inertized empty tube, and SVOC samples are enriched under liquid nitrogen low-temperature conditions. Both ends of the inert trap tube 18 are connected to the injection valve switching system through the first flow path 100. The temperature sensor 19 is installed at the bottom of the inert trap tube 18 to monitor the temperature of the inert trap tube 18. Heating joints 15 are respectively installed at both ends of the inert trap tube 18. The housing 14 is provided with a liquid nitrogen inlet 16 and a liquid nitrogen outlet 17 that are communicated with each other.

[0043] Specifically, the injection valve switching system includes a six-port injection valve 1, which has a first port, a second port, a third port, a fourth port, a fifth port, and a sixth port. Both ends of the inert trapping tube 18 of the liquid nitrogen cold trap 2 are connected to the first port and the fourth port of the six-port injection valve 1 through a first flow path 100 respectively. The second port is connected to a chromatographic carrier gas flow path 102, the third port is connected to a chromatographic injection port 101, the fifth port is connected to an upper needle insertion flow path, and the upper needle insertion flow path can be communicated with the top of the sample tube through an upper needle. A second flow path 200 is connected to the sixth port, and the end of the second flow path 200 away from the sixth port is a vent outlet 103. A second direct current solenoid valve (DC2) is installed on the second flow path 200. A third flow path 300 and a fourth flow path 400 are respectively connected to both sides of the second direct current solenoid valve on the second flow path 200. The other end of the third flow path 300 is connected to a lower needle insertion flow path, and a third direct current solenoid valve (DC3) is installed on the third flow path 300. The fourth flow path 400 is connected to a fifth flow path 500, and the fifth flow path 500 is connected to the lower needle insertion flow path. A fourth direct current solenoid valve (DC4) is installed on the fourth flow path 400. The end of the fifth flow path 500 away from the lower needle insertion flow path is a nitrogen input port 104. A pressure stabilizing valve 8, an electronic flow controller 7, and a first direct current solenoid valve (DC1) are sequentially installed on the fifth flow path 500. The joint of the fourth flow path 400 and the fifth flow path 500 is located between the electronic flow controller 7 and the first direct current solenoid valve. A part of the fifth flow path 500 between the pressure stabilizing valve 8 and the electronic flow controller 7 is connected to a sixth flow path 600, and the other end of the sixth flow path 600 is connected to a solvent bottle. A fifth direct current solenoid valve (DC5) and an electronic pressure controller 6 are installed on the sixth flow path 600. A seventh flow path 700 for pressure relief is connected to a part of the sixth flow path 600 between the fifth direct current solenoid valve (DC5) and the electronic pressure controller 6. A seventh direct current solenoid valve (DC7) is installed on the seventh flow path 700, and one end of the seventh flow path 700 is a pressure relief port 105.

[0044] Furthermore, the injection device further includes a bidirectional flat gasket extrusion sealing device 3 for tightly pressing the upper machine analysis cap in both directions, and the upper and lower flat gaskets are sealed with the upper machine analysis cap.

[0045] In summary, the working process of the injection device provided by the present invention is as follows: 1. After the sample tube is installed with the upper machine analysis cap and placed in the sample tray, the injection position is automatically controlled. 2. The motor of the bidirectional flat gasket extrusion sealing device 3 rotates forward, and the sealing device tightly presses the upper machine analysis cap in both directions. The upper and lower flat gaskets are sealed with the upper machine analysis cap, and the upper needle insertion flow path and the lower needle insertion flow path are communicated. 3. Solvent addition: The set N is input into 6 solvent bottles. 2Under pressure, the 6-position solvent selection valve switches to the addition position, and DC6 is opened. Under the action of air pressure, the solvent flows into the lower needle flow path through the 6-position solvent selection valve. The flow rate can be adjusted by regulating the pressure in the solvent bottle. The on / off time of the 6-position solvent selection valve and the solvent can be set to accurately control the volume of the added solvent; 4. The heating component extends to heat the sample tube, and the semi-volatile organic compounds in the sample tube are eluted in the high-temperature solvent; 5. The liquid nitrogen cold trap is set at a low temperature of about -20 to -196 degrees; 6. Purge: N 2 According to the set flow control, DC1 and DC2 are opened. The semi-volatile organic compounds and organic solvents in the sample tube are purged by N 2 and flow into the cryogenic trap 12 through the injection six-way valve 1. The semi-volatile organic compounds are enriched in the liquid nitrogen cold trap, and most of the solvent is discharged and emptied; During enrichment, as Figure 1 shown, ports 1 and 6 of the injection six-way valve are connected, ports 2 and 3 of the injection six-way valve are connected, and ports 4 and 5 of the injection six-way valve are connected; 7. Desorption: After the purge is completed, the low-voltage high-current heating controller 13 in the cryogenic trap 12 is heated, and the temperature range is 200 - 550 degrees. The enriched semi-volatile organic compounds are vaporized; 8. Injection: The injection six-way valve is switched, and the flow path of the valve changes. Ports 1 and 2 of the injection six-way valve are connected, ports 3 and 4 of the injection six-way valve are connected, and ports 5 and 6 of the injection six-way valve are connected. The chromatographic carrier gas flows through the injection six-way valve port 2, injection six-way valve port 1, and through the cryogenic trap. The vaporized semi-volatile organic compounds pass through the injection six-way valve port 4, port 3, and enter the chromatographic injection port 101 with the chromatographic carrier gas for analysis.

[0046] 9. Activation: N 2 According to the set activation flow control, DC3 and DC4 are opened. The low-voltage high-current heating controller 13 in the liquid nitrogen cold trap is heated, and the temperature range is 200 - 550 degrees to backflush the entire sample flow path.

[0047] Specifically, DC3 / 4 is the system activation instrument turned on. The purge and activation flows are controlled by (pressure stabilizing valve, electronic flow controller) and set in the method; DC5 is the internal standard bottle pressurizing valve, which is opened according to the set pressure and closed after reaching; DC7 is the pressure relief valve, which is opened when the pressure exceeds the set pressure, and the pressure control accuracy is within 0.01 kpa.

[0048] It should be noted that, for the foregoing embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, certain steps may be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0049] In the embodiments provided in this application, it should be understood that the disclosed device can be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the above division of units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or communication connection between each other can be through some interfaces. The indirect coupling or communication connection between devices or units can be in the form of telecommunications or other forms.

[0050] The units described as separate components above may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place, or they can be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0051] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting the protection scope of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still, without conflict and without creative efforts, combine, add or delete the features in the embodiments of the present invention according to the situation, or make other adjustments, so as to obtain different technical solutions that are essentially not divorced from the concept of the present invention. These technical solutions also belong to the scope of protection of the present invention.

Claims

1. A method for enriching SVOC semivolatiles, characterized in that: include: The sample containing SVOC is placed in a sample tube and sealed; Inject solvent into the sample tube and heat it to 50-500°C, using the solvent vapor pressure to promote SVOC desorption; The desorbed product is purged with inert gas to a liquid nitrogen cold trap, and the temperature of the liquid nitrogen cold trap is controlled at -196 to -20°C to enrich SVOC; The liquid nitrogen cold trap is heated to 200-550°C to transfer the entire amount of SVOC to the detection instrument for analysis.

2. The SVOC semivolatile enrichment method according to claim 1, characterized in that: The solvent injection flow rate is 10 to 2000 μL / min.

3. The SVOC semivolatile enrichment method according to claim 1, characterized in that: The inert gas is nitrogen, and the purge flow rate is 10 to 500 mL / min.

4. The SVOC semivolatile enrichment method according to claim 1, characterized in that: The temperature control range of the liquid nitrogen cold trap is -196 to 550° C., and the heating rate is 10 to 50° C. / s.

5. A sampling device for implementing the SVOC semi-volatile enrichment method according to any one of claims 1 to 4, characterized in that: include: The sample heating in-and-out mechanism comprises an automatic sample injector and a heating component. The automatic sample injector is used to place a plurality of sample tubes whose two ends are connected and sealed with upper analysis caps and can adjust the positions of the sample tubes. The heating component is used to heat the sample tubes after the solvent is injected. A solvent adding unit, used for injecting solvent into the sample tube; A purge unit is used to purge and transfer the SVOC in the sample tube to a liquid nitrogen cold trap; Liquid nitrogen cold trap, used to enrich SVOC; Injection valve switching system, used to switch between enrichment and injection paths.

6. The sample injection device according to claim 5, characterized in that: The automatic sampler includes a sample tray, a driving mechanism and a control module. The sample tray is used to place multiple sample tubes whose two ends are connected and sealed with upper analysis caps. The driving mechanism is used to drive the sample tray to rotate. The control module is electrically connected to the driving mechanism to control the rotation of the sample tray.

7. The sample injection device according to claim 5, characterized in that: The solvent addition unit includes multiple solvent bottles, an electronic pressure controller and a solvent selection valve. The multiple solvent bottles are used to contain different solvents. The electronic pressure controller is used to control the pressure in the solvent bottles. The solvent selection valve is used to select different solvents for addition. The solvent selection valve is connected to a lower needle flow path. The lower needle flow path can be connected to the bottom of the sample tube through the lower needle. A sixth DC solenoid valve is provided between the solvent selection valve and the lower needle flow path.

8. The sample injection device according to claim 5, characterized in that: The heating assembly includes a heating element and a telescopic structure. The telescopic structure is used to drive the heating element to extend or retract, and can heat the sample tube when extended.

9. The sample injection device according to claim 5, characterized in that: The liquid nitrogen cold trap comprises a liquid nitrogen tank, a liquid nitrogen flow controller, an ultra-low temperature trap and a low-voltage and high-current heating controller. The liquid nitrogen tank is connected to the liquid nitrogen inlet of the ultra-low temperature trap, and a liquid nitrogen solenoid valve and a liquid nitrogen flow controller are sequentially installed on the connecting flow path between the two. The low-voltage and high-current heating controller is connected to the ultra-low temperature trap. The ultra-low temperature trap comprises a shell, an inert capture tube and a temperature sensor. The inert capture tube is installed in the shell. The inert capture tube is a 1 / 16-inch inertized empty tube. Both ends of the inert capture tube are connected to the injection valve switching system through a first flow path. The temperature sensor is installed at the bottom of the inert capture tube for monitoring the temperature of the inert capture tube. Both ends of the inert capture tube are respectively installed with heating joints. The shell is provided with a connected liquid nitrogen inlet and a liquid nitrogen outlet.

10. The sample injection device according to claim 9, characterized in that: The injection valve switching system includes a six-way injection valve, the six-way injection valve is provided with a No. 1 port, a No. 2 port, a No. 3 port, a No. 4 port, a No. 5 port and a No. 6 port, the two ends of the inert capture tube of the liquid nitrogen cold trap are respectively connected to the No. 1 port and the No. 4 port of the six-way injection valve through a first flow path, the No. 2 port is connected to the chromatographic carrier gas flow path, the No. 3 port is connected to the chromatographic injection port, the No. 5 port is connected to the upper needle flow path, the upper needle flow path can be connected to the top of the sample tube through the upper needle, the No. 6 port is connected to the second flow path, the end of the second flow path away from the No. 6 port is a venting outlet, a second DC solenoid valve is installed on the second flow path, the second flow path is respectively connected to a third flow path and a fourth flow path located on both sides of the second DC solenoid valve, the other end of the third flow path is connected to the lower needle flow path, a third DC solenoid valve is installed on the third flow path, and the The fourth flow path is connected to the fifth flow path, the fifth flow path is connected to the lower needle flow path, a fourth DC solenoid valve is installed on the fourth flow path, the end of the fifth flow path away from the lower needle flow path is a nitrogen input port, a pressure regulating valve, an electronic flow controller and a first DC solenoid valve are installed on the fifth flow path in sequence, the joint of the fourth flow path and the fifth flow path is located between the electronic flow controller and the first DC solenoid valve, the part of the fifth flow path located between the pressure regulating valve and the electronic flow controller is connected to the sixth flow path, the other end of the sixth flow path is connected to the solvent bottle, a fifth DC solenoid valve and an electronic pressure controller are installed on the sixth flow path, the part of the sixth flow path located between the fifth DC solenoid valve and the electronic pressure controller is connected to the seventh flow path for pressure relief, a seventh DC solenoid valve is installed on the seventh flow path, and one end of the seventh flow path is a pressure relief port.

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