An automatic monitoring system for semi-volatile organic compounds in ambient air and waste gas

Abstract

The present invention discloses an automatic monitoring system for semi-volatile organic compounds in ambient air and waste gas, belonging to the technical field of environmental monitoring. The present invention includes an automatic sampling module, a sampling efficiency investigation module, a solvent addition module, a solvent blowing module, an analyte focusing module, a gas chromatography-mass spectrometer, and a waste liquid barrel; the automatic sampling module includes an automatic sampling base and a sampling chamber, the automatic sampling base includes a waiting area, a sampling area, and an extraction area, and the sampling chamber in the extraction area, the solvent blowing module, the analyte focusing module, and the gas chromatography-mass spectrometer are sequentially connected through pipelines. The present invention realizes the automation and high efficiency of the monitoring of semi-volatile organic compounds in ambient air and waste gas; at the same time, the sampling method of the system greatly increases the injection volume of the target substance, reduces the detection limit relative to the traditional analytical technical means, improves the method sensitivity, can detect more semi-volatile organic compounds, and can increase the monitoring frequency.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental monitoring, and particularly relates to an automatic monitoring system for semi-volatile organic compounds in ambient air and waste gas. Background Art

[0002] Semi-volatile organic pollutants (SVOCs) generally refer to organic compounds with boiling points between 170 and 350 °C and relatively low vapor pressures. Due to the vague classification criteria, there is often an overlap with volatile organic compounds. The SVOCs currently concerned in environmental monitoring mainly include dioxins, polycyclic aromatic hydrocarbons, organochlorine pesticides, chlorobenzenes, polychlorinated biphenyls, pyridines, quinolines, nitrobenzenes, phthalate esters, nitrosamines, anilines, phenols, polychlorinated naphthalenes, polybrominated diphenyl ethers, etc., and already include substances with boiling points exceeding 350 °C. Among them, some high-boiling, strongly polar or highly viscous SVOCs are easily adsorbed on particulate matter. Many SVOCs are directly harmful to the ecological environment or human health. For example, compounds such as dioxins, polycyclic aromatic hydrocarbons, and organochlorine pesticides exist in ambient air in the form of gas, aerosol, or attached to particulate matter. Therefore, it is necessary to monitor SVOCs in ambient air and waste gas.

[0003] The existing monitoring methods for SVOCs in the atmosphere include two modes: off-line monitoring and on-line monitoring. Off-line monitoring is carried out by sampling personnel on-site and transporting the samples to the laboratory for analysis. The entire analysis process is relatively long and requires processes such as sample collection, transportation, transfer, and analysis. On-line monitoring equipment mainly monitors gaseous SVOCs and is difficult to be used for monitoring higher-boiling SVOCs in particulate matter.

[0004] Existing monitoring technologies:

[0005] 1. Main domestic and foreign analysis methods: Using filter membranes (collecting particulate matter) + solid-phase adsorbents (enriching gaseous substances), adopting accelerated solvent extraction or Soxhlet extraction methods, extracting with organic solvents, then concentrating the extract to 0.1 - 1 mL by nitrogen blowing, and finally injecting the concentrated solution into a gas chromatograph for analysis through a liquid injector (the injection volume is generally 1 μL, basically not exceeding 2 μL).

[0006] Specific references can be made to: HJ 646 - 2013 "Determination of Polycyclic Aromatic Hydrocarbons in Ambient Air and Waste Gas - Gas Chromatography - Mass Spectrometry Method" and HJ 691 - 2014 "Sampling Technical Guidelines for Semi-volatile Organic Compounds in Ambient Air".

[0007] 2. New methods such as those of the US EPA: Using solid-phase adsorption materials for collection, then vaporizing semi-volatile organic compounds by high temperature, and then carrying them into a cold trap for enrichment by an inert gas, and finally thermally desorbing the cold trap and introducing it into a gas chromatograph for analysis.

[0008] Disadvantages of the first monitoring technique: (1) The degree of automation is not high. After concentration, it is necessary to manually transfer the concentrated solution to the instrument for analysis; (2) The injection volume is only 0.1% - 1% of the concentrated solution. The injection volume is too small, resulting in low monitoring sensitivity and making it difficult to accurately analyze some trace semi-volatile organic compounds.

[0009] Disadvantages of the second monitoring technique: It is difficult to completely vaporize and carry out the collected semi-volatile organic compounds by heating. The recovery rates of some substances with high boiling points or substances strongly bonded to the adsorbent are low, and the monitoring cost is high. Summary of the Invention

[0010] The purpose of the present invention is to provide an automatic monitoring system for semi-volatile organic compounds in ambient air and waste gas to solve the problems existing in the background technology.

[0011] The purpose of the present invention is achieved through the following technical solutions:

[0012] An automatic monitoring system for semi-volatile organic compounds in ambient air and waste gas, comprising an automatic injection module, a sampling efficiency investigation module, a solvent addition module, a solvent blowing module, a test substance focusing module, a gas chromatograph-mass spectrometer, and a waste liquid bucket;

[0013] The automatic injection module includes an automatic injection base and a sampling chamber. The automatic injection base includes a waiting area, a sampling area, and an extraction area. A plurality of the sampling chambers are respectively arranged in the waiting area, the sampling area, and the extraction area. A sampling cover and a sampling assembly are provided on the top of the sampling chamber in the sampling area, and an extraction cover is provided on the top of the sampling chamber in the extraction area;

[0014] The sampling efficiency investigation module is connected to the sampling cover; the solvent addition module is connected to the extraction cover;

[0015] The extraction cover, the solvent blowing module, the test substance focusing module, and the gas chromatograph-mass spectrometer are sequentially connected through pipelines;

[0016] The waste liquid bucket is respectively connected to the solvent addition module, the solvent blowing module, and the test substance focusing module.

[0017] Furthermore, the sampling chamber and the automatic injection base are fixed by plugging. A first temperature adjustment module is provided outside the sampling area and the extraction area. A heat insulation board is provided between the sampling area and the extraction area. The sampling chamber has an inverted conical structure. A filter membrane pressing ring, a filter membrane, a first support member, a solid phase adsorption material, and a second support member are sequentially arranged in the sampling chamber from top to bottom. An outlet channel is provided on one side of the top of the sampling chamber, and the outlet channel is communicated with the small end in the sampling chamber.

[0018] Further, the sampling cover and the extraction cover are each connected to the corresponding sampling chamber through a sealing nut. The top of the sampling cover is provided with a sampling inlet and a sampling outlet. The sampling inlet is located at the center of the sampling cover and communicates with the corresponding sampling chamber. The sampling outlet corresponds to and communicates with the outlet channel;

[0019] The top of the extraction cover is provided with an extraction liquid inlet and an extraction liquid outlet. The extraction liquid inlet is located at the center of the extraction cover and communicates with the corresponding sampling chamber. The extraction liquid outlet corresponds to and communicates with the outlet channel. The extraction liquid inlet is provided with an electromagnetic switching valve.

[0020] Further, the sampling assembly includes an oil-free air pump, a flow controller, a first three-way switching valve, and a filter. Two groups of the oil-free air pump and the flow controller are respectively connected to the first three-way switching valve. One end of the first three-way switching valve is connected to the sampling outlet, and the filter is located between the first three-way switching valve and the sampling outlet.

[0021] Further, the solvent addition module includes a first inert gas input assembly, a first multi-position selection valve, a second multi-position selection valve, and an extraction solvent bottle. The first multi-position selection valve, the second multi-position selection valve, the first inert gas input assembly, and the extraction liquid inlet are connected through a four-way connection. The extraction solvent bottle is respectively connected to the first multi-position selection valve and the second multi-position selection valve. Both the first multi-position selection valve and the second multi-position selection valve are provided with injection pumps. Outside the second multi-position selection valve, there are also a first surrogate solution bottle, a low-concentration standard solution bottle, and a high-concentration standard solution bottle. The second multi-position selection valve is connected to the waste liquid bucket.

[0022] Further, the solvent blowing module includes a six-way switching valve, an inert three-way switching valve, and a solvent removal chamber connected in sequence. The six-way switching valve is connected to the extraction liquid outlet of the extraction cover. The solvent removal chamber is of a U-shaped structure. The solvent removal chamber includes a thin tube and a thick tube. The outlet end of the thin tube is located at the bottom of the thick tube. An upper and lower independent heating module is provided outside the solvent removal chamber. The six-way switching valve and the inert three-way switching valve are respectively connected to the waste liquid bucket. Outside the six-way switching valve, there are also an internal standard solution bottle and a first quantitative loop. The internal standard solution bottle is connected to an inert gas source. Both ends of the first quantitative loop are respectively connected to the six-way switching valve.

[0023] Further, the analyte focusing module includes an inert four-way switching valve, an inert six-way switching valve, and a focusing tube connected in sequence. A second temperature adjustment module is provided outside the inert four-way switching valve and the inert six-way switching valve. A third temperature adjustment module is provided outside the focusing tube. The inert four-way switching valve is connected to the outlet end of the thick tube of the solvent removal chamber. The inert six-way switching valve is connected to the gas chromatography-mass spectrometer.

[0024] Furthermore, a second three-way switching valve and a second inert gas input assembly are provided outside the inert four-way switching valve. The second three-way switching valve, the inert four-way switching valve and the second inert gas input assembly are connected through a three-way connection, and the second three-way switching valve is connected to the waste liquid bucket.

[0025] Furthermore, the sampling efficiency investigation module includes a third multi-position selection valve, a third inert gas input assembly, a second surrogate solution bottle and a second quantitative loop. The third inert gas input assembly, the second surrogate solution bottle and the second quantitative loop are respectively connected to the third multi-position selection valve. Both ends of the second quantitative loop are connected to the third multi-position selection valve. One end of the second surrogate solution bottle is connected to an inert gas source. The third multi-position selection valve communicates with the sampling chamber in the sampling area, and the third multi-position selection valve is connected to the waste liquid bucket.

[0026] Furthermore, the extraction solvent bottle is of a sealed structure, and a one-way valve and a filter head are provided at the top of the extraction solvent bottle.

[0027] The beneficial effects of the present invention are as follows:

[0028] 1) The injection volume of the target substance is greatly increased, thereby reducing the detection limit and improving the method sensitivity. Substances with very low concentrations that need special attention can be detected, allowing for less sampling volume and sampling time, and improving the analysis efficiency, etc. In this case, some substances with very low concentrations but high toxicity can be detected, which is of great significance for environmental monitoring. Moreover, the shortening of the sampling time means higher monitoring "resolution". Within the same time, multiple analyses can be carried out. For example, originally it took 24 hours for one sample and one set of data, but now it can achieve one sample in 2 hours and 12 sets of data in 24 hours. More precise data analysis can be achieved, and the judgment of the air pollution situation is more accurate.

[0029] 2) It is convenient to achieve fully automatic unmanned operation. Human resources can be completely liberated from this, reducing the contact between people and toxic and harmful reagents, and also facilitating the implementation of the Internet of Things and cloud data. It is not only applicable to the unmanned operation of the laboratory, but also convenient for the development of automatic monitoring devices for fixed pollution source exhaust gas or environmental air points, etc.

[0030] 3) It is convenient to dispose of thermally unstable substances and substances that are difficult to vaporize due to easy deposition on the quartz surface. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of step S1 in Embodiment 1;

[0032] Figure 2 It is a schematic diagram of step S2 in Embodiment 1;

[0033] Figure 3is a schematic diagram of step S3 in Example 1;

[0034] Figure 4 is a schematic diagram of step S4 in Example 1;

[0035] Figure 5 is a schematic diagram of step S5 in Example 1;

[0036] Figure 6 is a schematic diagram of step S6 in Example 1;

[0037] Figure 7 is a schematic diagram of step S7 in Example 1;

[0038] Figure 8 is a schematic diagram of step S8 in Example 1;

[0039] Figure 9 is a schematic diagram of step S9 in Example 1;

[0040] Figure 10 is a schematic diagram of step S10 in Example 1;

[0041] Figure 11 is a schematic diagram of step S11 in Example 1;

[0042] Figure 12 is a schematic diagram of step S12 in Example 1;

[0043] Figure 13 is a schematic diagram of step S13 in Example 1;

[0044] Figure 14 is a schematic diagram of step S14 in Example 1;

[0045] Figure 15 is a schematic diagram of step S15 in Example 1;

[0046] Figure 16 is a schematic diagram of the sampling chamber in the present invention;

[0047] Figure 17 Schematic diagram of the solvent-driving chamber in the present invention;

[0048] Figure 18 is a schematic diagram of Example 2;

[0049] Figure 19 is a schematic diagram of Example 2;

[0050] Figure 20 is a schematic diagram of step T2 in Example 3;

[0051] Figure 21 is a schematic diagram of step T3 in Example 3;

[0052] In the figure, the dashed line represents the workflow path;

[0053] In the figure, 1 - automatic sampling module, 101 - waiting area, 102 - sampling area, 103 - extraction area, 11 - automatic sampling base, 12 - sampling chamber, 121 - sealing nut, 122 - solid phase adsorption material, 123 - outlet channel, 13 - sampling cover, 131 - sampling inlet, 132 - sampling outlet, 14 - extraction cover, 141 - extraction liquid inlet, 142 - extraction liquid outlet, 15 - oil-free air pump, 16 - flow controller, 17 - first three-way switching valve, 18 - filter, 19 - first temperature adjustment module, 2 - sampling efficiency investigation module, 21 - third multi-position selection valve, 22 - third inert gas input component, 23 - second surrogate solution bottle, 24 - second quantitative loop, 3 - solvent addition module, 31 - first inert gas input component, 32 - first multi-position selection valve, 33 - second multi-position selection valve, 34 - extraction solvent bottle, 341 - one-way valve, 342 - filter head, 35 - first surrogate solution bottle, 36 - low-concentration standard solution bottle, 37 - high-concentration standard solution bottle, 38 - four-way, 4 - solvent blowing module, 41 - six-way switching valve, 42 - inert three-way switching valve, 43 - solvent removal chamber, 431 - thin tube, 432 - thick tube, 433 - upper and lower independent heating module, 44 - internal standard solution bottle, 45 - first quantitative loop, 5 - analyte focusing module, 51 - inert four-way switching valve, 52 - inert six-way switching valve, 53 - focusing tube, 54 - second temperature adjustment module, 55 - third temperature adjustment module, 56 - second three-way switching valve, 57 - second inert gas input component, 6 - gas chromatography-mass spectrometer, 7 - waste liquid bucket. Specific embodiments

[0054] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present invention.

[0055] Example 1:

[0056] The present invention provides a technical solution: an automatic monitoring system for semi-volatile organic compounds in ambient air and waste gas, including an automatic sampling module 1, a sampling efficiency investigation module 2, a solvent addition module 3, a solvent blowing module 4, an analyte focusing module 5, a gas chromatography-mass spectrometer 6, and a waste liquid bucket 7;

[0057] The automatic sampling module 1 includes an automatic sampling base 11 and a sampling chamber 12. The automatic sampling base 11 includes a waiting area 101, a sampling area 102, and an extraction area 103. A plurality of the sampling chambers 12 are respectively arranged in the waiting area 101, the sampling area 102, and the extraction area 103. A sampling cover 13 and a sampling assembly are provided at the top of the sampling chamber 12 in the sampling area 102, and an extraction cover 14 is provided at the top of the sampling chamber 12 in the extraction area 103;

[0058] The sampling efficiency investigation module 2 is connected to the sampling cover 13; the solvent addition module 3 is connected to the extraction cover 14;

[0059] The extraction cover 14, the solvent blowing module 4, the analyte focusing module 5, and the gas chromatography-mass spectrometer 6 are sequentially connected by pipelines;

[0060] The waste liquid bucket 7 is respectively connected to the solvent addition module 3, the solvent blowing module 4, and the analyte focusing module 5.

[0061] Through the above technical solution, the automatic sampling module 1 is used to collect samples of ambient air or waste gas, and at the same time, semi-volatile organic compounds (SVOCs) in the samples are collected through the sampling chamber 12; then a solvent is added to the sampling chamber 12 through the solvent addition module 3, so that the collected semi-volatile organic compounds are dissolved in the organic solvent to obtain an extract; then the solvent in the extract is blown off through the solvent blowing module 4, and the semi-volatile organic compounds are vaporized by high temperature, and at the same time, they are enriched by low-temperature condensation through the focusing tube 53. Finally, the focusing tube 53 is heated to rapidly raise the temperature of the enriched semi-volatile organic compounds for desorption, and they are carried into the gas chromatography-mass spectrometer 6 by the carrier gas in the gas chromatography-mass spectrometer 6 for analysis.

[0062] Through the above technical solution, the sample finally entering the gas chromatography-mass spectrometer 6 is a gas, while the sample entering the analytical instrument in the traditional detection device is a liquid. The advantages brought by the gas injection in this method include the following points:

[0063] (1) The injection volume of the target substance is greatly increased, thereby reducing the method detection limit and improving the method sensitivity. Substances with very low concentrations that need special attention can be detected, and less sampling volume and sampling time can be allowed.

[0064] (2) It is convenient to realize automatic monitoring. The traditional method can only realize semi-automatic monitoring, and manual participation is required in each intermediate link. Volume fixing is an essential operation link in the process of processing SVOCs samples. At present, most intermediate pretreatment equipment requires analysts to fix the volume manually and then inject the sample into the instrument by themselves. This method does not have steps such as volume fixing and is convenient to realize full-automatic unmanned operation.

[0065] The specific operation process includes steps S1-S15, such asFigures 1 - 15 As shown in:

[0066] Step S1, as Figure 1 shown, at this time, a sealing cover plate is provided at the top of the sampling chamber 12 in the waiting area 101 to ensure the purity of the interior of the unsampled sampling chamber 12. At the same time, the sampling chamber 12 in the sampling area 102 and the sampling cover 13 are in a state to be installed, and the extraction cover 14 in the extraction area 103 and the corresponding sampling chamber 12 are also in a state to be installed.

[0067] Specifically refer to Figure 16 , in the inverted conical space of the sampling chamber 12, a filter membrane pressing ring, a filter membrane, a first support member, a solid phase adsorption material 122, and a second support member are sequentially arranged from top to bottom. The first support member and the second support member can be made of stainless steel mesh or sintered metal blocks, which can ensure the internal support while allowing the sample to pass through smoothly. The solid phase adsorption material 122 is stacked between the first support member and the second support member, generally spherical resin or silica gel balls, etc. If the water content of the sample is relatively high, a small amount of anhydrous sodium sulfate can be filled in the conical bottom layer inside the sampling chamber 12 to remove water. The filter membrane is made of polytetrafluoroethylene or quartz material. Preferably, a polytetrafluoroethylene filter membrane is used. Through its hydrophobicity, liquid water cannot pass through, making it difficult for water in the gas sample to enter the solvent removal chamber 43.

[0068] Furthermore, an outlet channel 123 is provided on one side of the top of the sampling chamber 12, and the outlet channel 123 communicates with the small end inside the sampling chamber 12.

[0069] For the sampling area 102, the sampling chamber 12 here is transferred from the sampling chamber 12 in the waiting area 101. The sampling cover 13 is covered on the top of the sampling chamber 12, and then it is locked by a sealing nut 121. It can be known that a sealing ring is provided at the connection between the sampling cover 13 and the sampling chamber 12 to ensure airtightness. At the same time, since a sampling inlet 131 and a sampling outlet 132 are provided on the top of the sampling cover 13, the sampling inlet 131 communicates with the sampling chamber 12, and sampling is carried out through the sampling inlet 131; the sampling outlet 132 corresponds to and communicates with the outlet channel 123, and the excess waste gas is discharged through the sampling outlet 132.

[0070] For the extraction area 103, the sampling chamber 12 here is transferred from the sampling chamber 12 after sampling is completed in the sampling area 102. The sampling cover 13 is removed and the extraction cover 14 is covered on the top of the sampling chamber 12, and then it is locked by the sealing nut 121. Similarly, a sealing ring is provided at the connection between the extraction cover 14 and the sampling chamber 12. At the same time, an extraction liquid inlet 141 and an extraction liquid outlet 142 are provided at the top of the extraction cover 14. The extraction liquid inlet 141 is also communicated with the sampling chamber 12. A solvent is added through the extraction liquid inlet 141, and the extraction liquid outlet 142 corresponds to and is communicated with the outlet channel 123, so that the extraction liquid formed after adding the organic solvent enters the solvent blowing module 4 from the extraction liquid outlet 142.

[0071] Step S2, as Figure 2 shown, at this time, the sampling chambers 12 in both the sampling area 102 and the extraction area 103 are assembled. The sampling inlet 131 is connected to the main sampling pipe or an independent sampling pipe and is communicated with the local atmosphere. At this time, the first temperature adjustment module 19 outside the sampling area 102 is in a refrigeration state, and the temperature is controlled to 5±2°C. Since the two oil-free air pumps 15 and the flow controllers 16 are respectively communicated with the first three-way switching valve 17, at this time, one group of oil-free air pumps 15 and flow controllers 16 is started (the two groups of oil-free air pumps 15 and flow controllers 16 are used alternately to extend the service life of the electrical appliances), and ambient air is collected at a constant flow rate. Preferably, the maximum sampling flow rate is 100 L / min, and the longest sampling time is 24 h. If collecting waste gas from a fixed pollution source, the sampling inlet 131 is connected to the waste gas sampling pipe, and the sampling flow rate and time are correspondingly reduced. For example, the sampling flow rate is 0.5 L / min, and the sampling time is set to 1 h. Further, a filter 18 is provided between the first three-way switching valve 17 and the sampling outlet 132. Impurities can be effectively filtered through the filter 18 to protect the switching valve, the flow meter, and the injection pump.

[0072] Continue as Figure 2 shown, at this time, the sampling area 102 is in a continuous sampling state. At this time, the second multi-position selection valve 33 is switched to the hole position communicating with the first surrogate solution bottle, and 100 μL of surrogate solution is extracted through the corresponding injection pump, and then the extracted surrogate is injected into the sampling chamber 12 in the extraction area 103.

[0073] Step S3, as Figure 3 shown, the sampling area 102 keeps sampling. The second multi-position selection valve 33 extracts 200 μL of extraction liquid from the extraction solvent bottle 34 to clean the pipeline and then discharges it into the waste liquid bucket 7. After the second multi-position selection valve 33 finishes cleaning, it is switched to the dead end position.

[0074] Furthermore, the extraction solvent bottle 34 is of a sealed structure, and a one-way valve 341 and a filter head 342 are provided at the top of the extraction solvent bottle 34.

[0075] Through the above technical solution, after the extraction solvent bottle 34 is pumped, the inside of the bottle is in a negative pressure state. When the one-way valve 341 is opened, the external air will enter the extraction solvent bottle 34 to maintain air pressure balance. At the same time, the air entering the bottle from the outside will be adsorbed and purified by the filter head 342 to prevent impurities such as organic substances from entering.

[0076] Continue as Figure 3 shown. Since the first multi-position selection valve 32, the second multi-position selection valve 33, the first inert gas input component 31 and the extraction liquid inlet 141 are connected through a four-way joint 38, by switching the first multi-position selection valve 32, the extraction liquid is pumped by an injection pump and injected into the sampling chamber 12 of the extraction area 103. The extraction liquid can be a mixed liquid of n-hexane and acetone, or dichloromethane and acetone. The extracted extraction liquid submerges the solid phase adsorption material 122 and the filter membrane. The volume of the added extraction liquid is related to the remaining space volume of the sampling chamber 12. Generally speaking, the volume of the added extraction liquid should be within 100 mL, and the specific volume can be adjusted according to the actual situation. After adding the extraction liquid to half of the set volume, the electromagnetic switch valve of the extraction cover 14 is opened to enable the residual gas in the sampling chamber 12 to be discharged. The outlet of the electromagnetic switch valve can be connected to an activated carbon adsorption tube. After reaching the full set volume of the injected extraction liquid, the electromagnetic switch valve is closed to completely seal the sampling chamber 12, and at the same time, the first multi-position selection valve 32 is switched to the dead-end position.

[0077] Step S4, as Figure 4 shown. The sampling area 102 keeps sampling. The extraction area 103 heats the corresponding sampling chamber 12 through the first temperature adjustment module 19. Specifically, it can be heated in the following two ways: 1. Ultrasonic heating method: The extraction area 103 starts to heat, and the temperature is slightly lower than the atmospheric boiling point of the extraction liquid by 2 - 4 °C. The ultrasonic waves are transmitted to the sampling chamber 12 by the ultrasonic elements arranged in the automatic sampling base 11; 2. High-temperature and high-pressure method: The extraction area 103 starts to heat, and the temperature generally does not exceed 100 °C (for example, for a boiling point of 100 °C, the corresponding pressure of acetone is 373 kPa, n-hexane is 244 kPa, and dichloromethane is 570 kPa). At this time, due to the sealing of the cavity, the extraction liquid remains in a liquid state, and at the same time, the high temperature promotes the dissolution of the target substance. The single extraction time of the sampling chamber 12 in the extraction area 103 is determined according to the debugging results and generally does not exceed 1 h.

[0078] Step S5, as Figure 5As shown, the sampling area 102 keeps sampling. The extraction actions such as heating and ultrasonic in the sampling chamber 12 of the extraction area 103 are stopped. The six-way switching valve 41 and the inert three-way switching valve 42 are connected, so that the solvent in the sampling chamber 12 flows into the solvent removal chamber 43 due to the pressure difference, reducing the pressure in the system to prevent the loss of the extract due to too fast flow rate; maintain this state for about 1 min. After the pressure is basically balanced, connect the inert four-way switching valve 51 and the second three-way switching valve 56 to connect them with the waste liquid bucket 7. Start the first inert gas input component 31. Here, the inert gas source used by the first inert gas input component 31 is nitrogen. The first inert gas input component 31 is also equipped with a gas flow controller to press all the extracts in the sampling chamber 12 into the solvent removal chamber 43 at a lower flow rate (not exceeding 40 mL / min). If multiple extractions are required, repeat steps S3 - S5. Generally, the number of extractions does not exceed 2 times.

[0079] Step S6, as Figure 6 shown, sampling continues. There is a solenoid valve between the internal standard solution bottle 44 and the inert gas source. By opening the solenoid valve, the internal standard liquid is pressed into the first quantitative loop 45 using the pressure difference. After ensuring that the internal standard liquid completely replaces the substances in the first quantitative loop 45, close the solenoid valve. Preferably, the inert gas source is nitrogen, the first quantitative loop 45 is 10 μL, and adding 5 times the volume of the quantitative loop is sufficient to ensure complete replacement, that is, 50 μL.

[0080] Step S7, as Figure 7 shown, sampling continues. At this time, the first inert gas input component 31 in the solvent addition module 3 is connected to the sampling chamber 12 of the extraction area 103, and all the internal standard liquid in the first quantitative loop 45 is introduced into the solvent removal chamber 43 using the first inert gas input component 31. The preferred nitrogen flow rate is about 40 mL / min, and the gas is introduced for about 1 min.

[0081] Step S8, as Figure 8 shown, sampling continues. Since there is an upper and lower independent heating module 433 outside the solvent removal chamber 43, the heating module below the solvent removal chamber 43 starts to heat independently at this time, with a heating rate not higher than 10 °C / min, and the temperature is controlled 2 - 5 °C below the boiling point of the extraction liquid. The upper half of the solvent removal chamber 43 does not start heating. Specifically, as Figure 17 shown, since the solvent removal chamber 43 includes a thin tube 431 and a thick tube 432, the outlet end of the thin tube 431 is located at the bottom of the thick tube 432. The high-purity nitrogen of the first inert gas input component 31 brings all the liquid in the thin tube into the thick tube, and all the extracts gather at the thick tube. At the same time, some target substances with insufficiently high boiling points that are vaporized will condense in the upper part of the thick tube 432 of the solvent removal chamber 43; the high-purity nitrogen of the first inert gas input component 31 continues to purge the extract in the solvent removal chamber 43 at a flow rate not exceeding 40 mL / min, purging the solvent in the solvent removal chamber 43 into the waste liquid bucket 7, and the semi-volatile organic compounds (SVOCs) remain in the solvent removal chamber 43.

[0082] Blow out all the solvent in the solvent removal chamber 43, or the remaining solvent is no more than 0.1 mL. If there are SVOCs with relatively low boiling points in the target substance, when only a few milliliters of solvent remain, heating can be stopped and purged at room temperature.

[0083] Furthermore, an observation hole is provided outside the thick tube 432 of the solvent removal chamber 43. Observe through the observation hole, record the time when the purging is completed, and set it into the program. Subsequently, proceed according to this time; or be equipped with components such as sensors to automatically judge whether the solvent has been blown out cleanly to achieve automation.

[0084] Step S9, as Figure 9 shown, the sampling continues. The focusing tube 53 is controlled to -30 °C by the third temperature adjustment module 55. All the upper and lower heating zones of the solvent removal chamber 43 are turned on, and heated to 400 - 450 °C at a rate of about 5 °C / min and keep the temperature constant. The high-purity nitrogen gas flow rate in the first inert gas input component 31 is 20 mL / min. The SVOCs in the solvent removal chamber 43 are vaporized and all blown into the focusing tube 53 and condensed and adsorbed by it.

[0085] Step S10, as Figure 10 shown, the sampling continues. The focusing tube 53 is heated to 400 °C at a rate not less than 60 °C / min. Switch the inert six-way valve, and use the carrier gas of the gas chromatograph - mass spectrometer 6 (GC / MS) to introduce the SVOCs in the focusing tube 53 into the GC / MS for analysis.

[0086] Meanwhile, the first multi-position selection valve 32 extracts the extraction liquid in the extraction solvent bottle 34 to the sampling chamber 12 in the extraction area 103 for cleaning the solvent removal chamber 43. At this time, the extraction liquid does not need to fill the sampling chamber 12 completely, and the volume of the extracted extraction liquid is 10 - 50 mL.

[0087] Step S11, as Figure 11 shown, the sampling continues. Through the first inert gas input component 31, the extraction liquid in the sampling chamber 12 is pressed into the solvent removal chamber 43. The inert gas flow blows all the liquid in the thin tube into the thick tube. Since the solvent removal chamber 43 is U-shaped, the liquid all accumulates at the bottom of the thick tube. At this time, the lower heating zone of the solvent removal chamber 43 is heated to make the extraction liquid slightly boil, so that its solvent evaporates to clean the inner wall of the upper half of the solvent removal chamber 43 that is not soaked. Due to the temperature difference, the solvent will condense and flow down in the upper half, cleaning the possible residues on the inner wall. The process lasts for several minutes. This step can also be carried out in step S10 to save time.

[0088] Step S12, as Figure 12As shown, the sampling continues. The inert gas source of the second inert gas input component 57 uses nitrogen. The second inert gas input component 57 is provided with a nitrogen pressure reducing valve, a gas flow controller, and a solenoid valve. Keep the solvent removal chamber 43 heated as a whole through the upper and lower independent heating modules 433. Connect the second inert gas input component 57, the second three-way switching valve 56, the inert four-way switching valve 51, and the solvent removal chamber 43. Enable the second inert gas input component 57 and introduce nitrogen. Slowly press the extraction liquid in the solvent removal chamber 43 into the waste liquid bucket 7 along the inert three-way switching valve 42 and the six-way switching valve 41 at a flow rate of about 30 mL / min. After all the extraction liquid used for cleaning the solvent removal chamber 43 is emptied, still maintain the nitrogen flushing of the second inert gas input component 57. The temperature of the solvent removal chamber 43 gradually rises from low to high, and finally rises to 400 °C, then the temperature control is stopped, and then the temperature is kept decreasing (the specific heating program and the highest temperature can be determined according to the debugging experiment). When the temperature of the solvent removal chamber 43 drops to about 60 °C, stop the nitrogen flushing of the second inert gas input component 57.

[0089] Step S13, as Figure 13 shown, the sampling continues. Flush the inert six-way switching valve 52 with nitrogen through the second inert gas input component 57 at a flow rate of about 40 mL / min for 1 min.

[0090] Step S14, as Figure 14 shown, the sampling continues. Flush the inert six-way switching valve 52 through the second inert gas input component 57 at a flow rate of about 40 mL / min. After 5 min, the temperature control of the focusing tube 53 is stopped, and the temperature continues to decrease; when the temperature of the focusing tube 53 drops by about 80 °C, stop the second inert gas input component 57. If the long-term high temperature affects the electrical life.

[0091] It can be known that during the process of steps S1 to S13, the second temperature adjustment module 54 maintains a constant temperature control at 300 °C. The second temperature adjustment module 54 mainly keeps the inert four-way switching valve 51, the inert six-way switching valve 52, and the connected pipelines heated to prevent the extraction liquid from condensing on the connecting pipelines. After Figure 14 this process, the heating of the second temperature adjustment module 54 can be stopped.

[0092] Step S15, as Figure 15 shown, the sampling in the sampling area 102 ends, and the sampling component and the first temperature adjustment module 19 are closed. Move the sampling chamber 12 that has been extracted in the extraction area 103 to the waiting area 101 through the automatic sampling base 11. Move the sampling chamber 12 that has been sampled in the sampling area 102 to the extraction area 103, and move the next sampling chamber 12 in the waiting area 101 to the sampling area 102. Start the next round of gas sampling and analysis. At this time, the second temperature adjustment module 54 is restarted and kept heated at a constant temperature of 300 °C.

[0093] Example 2:

[0094] Based on step S2 in Example 1, a scheme for adding a surrogate during the sampling process is provided.

[0095] Specifically refer to Figure 18 and Figure 19 As shown in Figure 18 , switch the third multi-position selection valve 21 to connect the second surrogate solution bottle 23 and the second metering loop 24. Since one end of the second surrogate solution bottle 23 is connected to an inert gas source, the inert gas source uses nitrogen, and at the same time, a solenoid valve is provided between the second surrogate solution bottle 23 and the inert gas source. Open the solenoid valve so that the surrogate solution in the second surrogate solution bottle 23 flows into the second metering loop 24 under the pressure difference and fully displaces the substances inside the second metering loop 24. After sufficient displacement, close the solenoid valve.

[0096] As shown in Figure 19 , switch the third multi-position selection valve 21 and start the third inert gas input component 22. The inert gas source of the third inert gas input component 22 uses nitrogen. The third inert gas input component 22 is provided with a nitrogen pressure reducing valve, a solenoid valve and a flow limiting valve. Open the solenoid valve, and under the control of the flow limiting valve, nitrogen fills the surrogate solution in the second metering loop 24 into the sampling chamber 12 at about 20 mL / min. After ensuring that all the surrogate solution in the second metering loop 24 is filled, close the solenoid valve and the third multi-position selection valve 21.

[0097] Since the surrogate is added during the sampling process, which is different from adding the surrogate during the extraction process (adding the surrogate in step S2), the former can evaluate the recovery rate of the target substance in the whole process through the surrogate recovery rate, while the latter can only evaluate the recovery rate starting from the extraction step. Therefore, in terms of comprehensiveness, the former is more important, while the latter also has significance. The combination of the two can analyze the recovery rate of the two key steps of sampling and extraction. Surrogates can be added multiple times at equal time intervals during the sampling process, and repeat the Figures 18 - 19 steps. If adding multiple times is required, the concentration of the surrogate solution should be prepared as 1 / n (n is the number of additions) of the one-time addition.

[0098] Example 3:

[0099] Based on Example 1, a scheme for the working curve quantification method mode is provided. This scheme includes steps T1 to T15. Only the sampling chamber 12 in the extraction area 103 is involved in the whole process, and the sampling chamber 12 in the sampling area 102 no longer maintains continuous sampling.

[0100] Step T1 is the same as step S1.

[0101] Step T2, refer to Figure 20, the sampling chamber 12 in the sampling area 102 does not participate in sampling. The second multi-position selection valve 33 is connected to the extraction solvent bottle 34, and the extraction liquid is drawn to clean the pipeline and then discharged into the waste liquid bucket 7, repeating this process 2 to 3 times.

[0102] Step T3, add the standard solution, specifically as Figure 21 shown. The second multi-position selection valve 33 is respectively connected to the low-concentration standard solution bottle 36 and the high-concentration standard solution bottle 37, and is added in sequence from the low-concentration standard solution to the high-concentration standard solution. For example: when plotting 6 working curve points, set the concentration difference between the low-concentration standard solution bottle 36 and the high-concentration standard solution bottle 37 to 20 times (the setting of the concentration of the surrogate in the standard solution), and take 100 μL, 200 μL, 500 μL of the low-concentration standard solution and 100 μL, 200 μL, 500 μL of the high-concentration standard solution.

[0103] During the process of plotting the working curve points, first, the second multi-position selection valve 33 is connected to the low-concentration standard solution bottle 36. First, draw 100 μL of the standard solution to clean the pipeline and then discharge it into the waste liquid bucket 7; then draw the set volume of the low-concentration standard solution again and inject it into the sampling chamber 12, and steps T4 to T15 will be carried out; after the standard solution is injected, the second multi-position selection valve draws 100 μL of the extraction liquid to clean the pipeline and then discharges it into the waste liquid bucket 7. After completion, the second multi-position selection valve 33 is switched to the dead-end position.

[0104] Step T4, except that the sampling chamber 12 in the sampling area 102 does not participate in sampling, the rest is the same as step S3.

[0105] Step T5, except that the sampling chamber 12 in the sampling area 102 does not participate in sampling, the rest is the same as step S4.

[0106] Step T6, except that the sampling chamber 12 in the sampling area 102 does not participate in sampling, the rest is the same as step S5.

[0107] Step T7, except that the sampling chamber 12 in the sampling area 102 does not participate in sampling, the rest is the same as step S6.

[0108] Step T8, except that the sampling chamber 12 in the sampling area 102 does not participate in sampling, the rest is the same as step S7.

[0109] Step T9, except that the sampling chamber 12 in the sampling area 102 does not participate in sampling, the rest is the same as step S9.

[0110] Step T11, except that the sampling chamber 12 in the sampling area 102 does not participate in sampling, the rest is the same as step S10.

[0111] Step T12, except that the sampling chamber 12 in the sampling area 102 does not participate in sampling, the rest is the same as step S11.

[0112] Step T13 is the same as step S12, except that the sampling chamber 12 in the sampling area 102 does not participate in sampling.

[0113] Step T14 is the same as step S13, except that the sampling chamber 12 in the sampling area 102 does not participate in sampling.

[0114] Step T15 is the same as step S14, except that the sampling chamber 12 in the sampling area 102 does not participate in sampling. After this step, it indicates that the working curve point is plotted. If the filter membrane and the solid-phase adsorption material 122 in the sampling chamber 12 are not damaged, the sampling chamber 12 in this extraction area 103 can still be used to add the standard solution for the next curve point starting from step T3, and so on until the curve is plotted.

[0115] Compared with the standard curve quantification method, the working curve quantification method can eliminate the errors generated in the extraction, concentration, injection and other links of the target substance. Except for the sampling part, the remaining operation steps are the same as those of the analyte to be measured, which reflects most of the analysis process. If there is a loss of the target substance, there will be a certain loss corresponding to different concentration points. The working curve quantification can better reflect the actual concentration level of the analyte in the sample, and the quantification result is more accurate under the condition of comparable linearity.

[0116] The above is only the preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be changed within the scope of the concept described herein through the above teachings or the technology or knowledge in the relevant field. And the changes and modifications made by those skilled in the art that do not depart from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. An automatic monitoring system for semi-volatile organic compounds in ambient air and exhaust gas, characterized in that: It includes an automatic sampling module (1), a sampling efficiency testing module (2), a solvent adding module (3), a solvent blowing module (4), an analyte focusing module (5), a gas chromatograph-mass spectrometer (6) and a waste liquid bucket (7); The automatic sampling module (1) comprises an automatic sampling base (11) and a sampling chamber (12); the automatic sampling base (11) comprises a waiting area (101), a sampling area (102) and an extraction area (103); a plurality of sampling chambers (12) are arranged in the waiting area (101), the sampling area (102) and the extraction area (103), respectively; the sampling chamber (12) in the waiting area (101) has a cover on the top; the sampling chamber (12) in the sampling area (102) has a sampling cover (13) and a sampling assembly on the top; and the sampling chamber (12) in the extraction area (103) has an extraction cover (14) on the top; The sampling efficiency investigation module (2) is connected to the sampling cover (13); the solvent addition module (3) is connected to the extraction cover (14); The extraction cover (14), the solvent blowing module (4), the analyte focusing module (5) and the gas chromatograph-mass spectrometer (6) are connected in sequence through pipelines; The waste liquid barrel (7) is respectively connected to the solvent adding module (3), the solvent blowing module (4) and the object to be tested focusing module (5); The sampling cavity (12) and the automatic injection base (11) are fixed by plugging, a first temperature adjustment module (19) is provided outside the sampling area (102) and the extraction area (103), a heat insulation board is provided between the sampling area (102) and the extraction area (103), the sampling cavity (12) has an inverted cone structure, and the sampling cavity (12) is provided with a filter membrane pressure ring, a filter membrane, a first support member, a solid phase adsorption material (122) and a second support member from top to bottom, and an outlet channel (123) is provided on one side of the top of the sampling cavity (12), and the outlet channel (123) is connected to the small end of the sampling cavity (12); The sampling cover (13) and the extraction cover (14) are connected to the corresponding sampling chamber (12) via a sealing nut (121), respectively; a sampling inlet (131) and a sampling outlet (132) are provided at the top of the sampling cover (13); the sampling inlet (131) is located at the center of the sampling cover (13) and is in communication with the corresponding sampling chamber (12); the sampling outlet (132) corresponds to and is in communication with the outlet channel (123); An extraction liquid inlet (141) and an extraction liquid outlet (142) are provided at the top of the extraction cover (14); the extraction liquid inlet (141) is located at the center of the extraction cover (14) and is in communication with the corresponding sampling cavity (12); the extraction liquid outlet (142) corresponds to and is in communication with the outlet channel (123); and the extraction liquid inlet (141) is provided with an electromagnetic switch valve; The solvent removal module (4) comprises a six-way switching valve (41), an inert three-way switching valve (42) and a solvent-removing chamber (43) which are connected in sequence. The six-way switching valve (41) is connected to the extraction liquid outlet (142) of the extraction cover (14). The solvent-removing chamber (43) is a U-shaped structure. The solvent-removing chamber (43) comprises a thin tube (431) and a thick tube (432). The outlet end of the thin tube (431) is located at the bottom of the thick tube (432). An upper and lower independent heating module (433) is arranged outside the solvent-removing chamber (43). The six-way switching valve (41) and the inert three-way switching valve (42) are respectively connected to the waste liquid barrel (7). An internal standard solution bottle (44) and a first quantitative ring (45) are also arranged outside the six-way switching valve (41). The internal standard solution bottle (44) is connected to an inert gas source. Both ends of the first quantitative ring (45) are respectively connected to the six-way switching valve (41). The analyte focusing module (5) comprises an inert four-way switching valve (51), an inert six-way switching valve (52) and a focusing tube (53) which are connected in sequence; the inert four-way switching valve (51) and the inert six-way switching valve (52) are provided with a second temperature regulating module (54) outside; the analyte focusing tube (53) is provided with a third temperature regulating module (55) outside; the inert four-way switching valve (51) is connected to an outlet end of a thick tube (432) of the solvent-driving chamber (43); and the inert six-way switching valve (52) is connected to the gas chromatograph-mass spectrometer (6).

2. The automatic monitoring system for semi-volatile organic compounds in ambient air and exhaust gas according to claim 1, characterized in that: The sampling assembly comprises an oil-free air pump (15), a flow controller (16), a first three-way switching valve (17) and a filter (18); the two groups of the oil-free air pump (15) and the flow controller (16) are respectively connected to the first three-way switching valve (17); one end of the first three-way switching valve (17) is connected to the sampling outlet (132); and the filter (18) is located between the first three-way switching valve (17) and the sampling outlet (132).

3. The automatic monitoring system for semi-volatile organic compounds in ambient air and exhaust gas according to claim 2, characterized in that: The solvent addition module (3) comprises a first inert gas input assembly (31), a first multi-position selector valve (32), a second multi-position selector valve (33) and an extraction solvent bottle (34); the first multi-position selector valve (32), the second multi-position selector valve (33), the first inert gas input assembly (31) and the extraction liquid inlet (141) are connected via a four-way (38); the extraction solvent bottle (34) is connected to the first multi-position selector valve (32) and the second multi-position selector valve (33), respectively; the first multi-position selector valve (32) and the second multi-position selector valve (33) are both provided with an injection pump; the second multi-position selector valve (33) is also provided with a first substitute solution bottle (35), a low-concentration standard solution bottle (36) and a high-concentration standard solution bottle (37); the second multi-position selector valve (33) is connected to the waste liquid barrel (7).

4. The automatic monitoring system for semi-volatile organic compounds in ambient air and exhaust gas according to claim 1, characterized in that: A second three-way switching valve (56) and a second inert gas input assembly (57) are also provided outside the inert four-way switching valve (51); the second three-way switching valve (56), the inert four-way switching valve (51) and the second inert gas input assembly (57) are connected via a three-way connection; the second three-way switching valve (56) is connected to the waste liquid barrel (7).

5. The automatic monitoring system for semi-volatile organic compounds in ambient air and exhaust gas according to claim 1, characterized in that: The sampling efficiency investigation module (2) comprises a third multi-position selector valve (21), a third inert gas input assembly (22), a second substitute solution bottle (23) and a second quantitative ring (24); the third inert gas input assembly (22), the second substitute solution bottle (23) and the second quantitative ring (24) are respectively connected to the third multi-position selector valve (21); both ends of the second quantitative ring (24) are respectively connected to the third multi-position selector valve (21); one end of the second substitute solution bottle (23) is connected to an inert gas source; the third multi-position selector valve (21) is communicated with the sampling chamber (12) of the sampling area (102); and the third multi-position selector valve (21) is connected to the waste liquid barrel (7).

6. The automatic monitoring system for semi-volatile organic compounds in ambient air and exhaust gas according to claim 3, characterized in that: The extraction solvent bottle (34) is a sealed structure, and a one-way valve (341) and a filter head (342) are provided on the top of the extraction solvent bottle (34).

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