Device and method for collecting and determining volatile organic compounds in atmosphere

Abstract

The invention discloses a device and a method for collecting and determining volatile organic compounds in atmosphere, and relates to the technical field of atmosphere component determination, the technical key point is that the method comprises the following steps: connecting a micro-extraction head adapter pipe with an atmosphere sampler, setting sampling flow and time, dynamically exposing adsorption fibers to capture VOCs, and determining the volatile organic compounds in the atmosphere. Desorbing for 5 minutes at the temperature of 250 DEG C through a gas chromatograph-mass spectrometer, and completing detection by combining helium carrier gas and a DB-1MS capillary column; the device comprises a micro-extraction head adapter tube, an atmosphere sampling instrument and a GC-MS, the adapter tube is made of an inert polymer material, an adapter opening can fix micro-extraction head suites of different specifications, and rapid replacement is supported. By optimizing dynamic sampling control and GC-MS detection conditions, the method solves the problem of unstable sampling in the open environment of the traditional SPME technology, has the advantages of high sensitivity, low cost, convenience in operation and the like, and is suitable for efficiently monitoring VOCs in open environments such as cities, forests, industrial areas and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of atmospheric composition determination, in particular to a device and method for collecting and determining atmospheric volatile organic compounds. BACKGROUND

[0002] With the acceleration of industrialization and the improvement of urbanization, the pollution problem of volatile organic compounds (VOCs) in the atmosphere is becoming increasingly serious. VOCs not only participate in photochemical reactions to generate ozone and fine particulate matter (PM2.5), but also directly harm human health, such as causing respiratory diseases and carcinogenic risks. Therefore, developing efficient and sensitive atmospheric VOCs sampling and detection technology is of great significance for environmental pollution monitoring and health risk assessment.

[0003] Currently, the off-line detection technology of atmospheric VOCs mainly includes Summa canister sampling, gas bag sampling and adsorbent sampling. Among them, adsorbent sampling (such as activated carbon, Tenax-TA adsorption tube) is widely used due to its portability and high enrichment efficiency. This technology captures VOCs in the atmosphere through adsorption tube filling materials, and then analyzes them in the laboratory by thermal desorption-gas chromatography / mass spectrometry (GC / MS). However, adsorption tubes need to rely on expensive aging instruments for high-temperature desorption, and need to be strictly matched with GC / MS systems, resulting in high equipment cost and high operation threshold, which limits its popularity in some laboratories.

[0004] On the other hand, as a solvent-free, integrated sampling-enrichment-injection innovative method, solid phase microextraction (SPME) technology has been widely used in the detection of VOCs in closed containers (such as water bodies, food packaging). SPME adsorbs target compounds through fiber coating and directly analyzes them by GC / MS injection port thermal desorption, without the need for complex pretreatment equipment. However, traditional SPME technology lacks a dedicated pipeline for atmospheric sampling instruments, making it impossible to achieve dynamic air sampling in an open environment. The fiber is exposed to open air and is easily disturbed by environmental factors such as wind speed, temperature and humidity, and cannot quantitatively control the sampling flow and time, making it difficult to apply in atmospheric VOCs monitoring.

[0005] In view of the above technical bottlenecks, there is an urgent need for a solution that can retain the advantages of SPME without the need for an aging instrument, and also compatible with dynamic sampling of atmospheric sampling instruments. The present application designs a new type of microextraction head adapter tube and a matching process, for the first time seamlessly integrating SPME technology with atmospheric sampling instruments, achieving efficient collection and accurate determination of VOCs in an open environment, filling the technical gap in this field. SUMMARY

[0006] The present application aims to solve the above problems, and provides a device and method for collecting and measuring atmospheric volatile organic compounds, so as to solve the limitations of the adsorbent sampling technology of the prior art and the deficiencies of the solid phase microextraction (SPME) technology in atmospheric sampling.

[0007] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows: a method for collecting and measuring atmospheric volatile organic compounds, comprising the following steps:

[0008] S1: connecting a microextraction head adapter tube with an atmospheric sampling instrument, and inserting a solid phase microextraction head kit into an adapter port;

[0009] S2: setting the sampling flow rate of the atmospheric sampling instrument to 1.0-2.0 L / min, and the sampling time to 30-120 minutes;

[0010] S3: pushing the microextraction head adsorption fiber to the intersection of the adapter tube bulge and the air inlet tube, and performing dynamic airflow sampling;

[0011] S4: after the sampling is completed, the fiber is recovered, and the detection is completed by a gas chromatography-mass spectrometry instrument within 24 hours.

[0012] Further, the sampling flow rate is preferably 1.3-1.5 L / min, and the sampling time is preferably 60-90 minutes.

[0013] Further, the desorption temperature of the gas chromatography-mass spectrometry instrument is 250℃, the desorption time is 5 minutes, the carrier gas is helium, and the flow rate is 1.0 mL / min.

[0014] Further, the gas chromatography uses a DB-1MS capillary column, and the temperature rising program is 40℃ initially, rising to 240℃ at a rate of 6℃ / min, and maintaining for 12 minutes.

[0015] Further, the electron ionization source temperature of the mass spectrometer detector is 230℃, and the mass scan range is m / z 35-500.

[0016] Further, in the detection process of step S4, n-hexane is used as an internal standard, and the concentration is 100 μg / mL, which is used for quantitative analysis of each volatile organic compound component.

[0017] Further, the air inlet tube, the tube bulge and the air outlet tube of the microextraction head adapter tube are made of inert polymers.

[0018] Further, the microextraction head adapter tube is detachable and replaceable, and is suitable for different specifications of solid phase microextraction head kits.

[0019] Further, the detection result is qualitatively determined by comparing with a NIST standard database, the matching degree threshold is greater than 70%, and the content of each component is calculated based on an internal standard method.

[0020] Another object of the present application is to provide a device for collecting and measuring atmospheric volatile organic compounds, comprising the following components:

[0021] A micro-extraction head adapter tube, comprising an air inlet tube, a tube belly and an air outlet tube;

[0022] An air sampler in communication with the air outlet tube of the micro-extraction head adapter tube through a silica gel tube;

[0023] A solid-phase micro-extraction head kit, comprising a micro-extraction head, a guide and a handle, which can be inserted into the adapter port of the micro-extraction head adapter tube;

[0024] A gas chromatograph-mass spectrometer for desorbing and detecting the adsorbed volatile organic compounds.

[0025] Further, the length of the air inlet tube of the micro-extraction head adapter tube is 30 cm, and the inner diameter is 1 cm; the length of the tube belly is 10 cm, and the inner diameter is 3 cm; the length of the air outlet tube is 15 cm, and the inner diameter is 1 cm.

[0026] Further, the adapter port is located at the tube belly part, 5.5 cm away from the bottom of the tube belly, with an inner diameter of 1.5 cm, and is used for fixing the handle of the micro-extraction head kit.

[0027] Further, the adsorption fiber material of the solid-phase micro-extraction head is a 100 μm coating, which can be exposed and adsorb volatile organic compounds in a dynamic air flow

[0028] Compared with the prior art, the present application has the following beneficial effects: by combining the solid-phase micro-extraction technology with the dynamic air flow sampling, the efficiency and accuracy of atmospheric VOCs monitoring are significantly improved. The traditional SPME technology cannot control the sampling flow and time in an open environment due to the lack of an adapter device, resulting in low data reliability. By setting the sampling flow and time, and combining the optimized design of the micro-extraction head adapter tube, the present application ensures that the adsorption fiber is fully exposed in the dynamic air flow and does not contact the tube wall, effectively reducing the interference of environmental factors. In addition, by using high temperature desorption at 250℃, helium carrier gas and chromatographic conditions of DB-1MS capillary column, combined with NIST database qualitative and internal standard method quantitative, high sensitivity detection of trace VOCs is realized, with a detection limit as low as μg / m 3 grade, and a repeatability error less than 5%.

[0029] The application solves the equipment dependency problem of the traditional technology through modular design. The micro-extraction head adapter pipe adopts inert polymer material to avoid adsorption or reaction with VOCs. The detachable structure supports quick replacement of solid-phase micro-extraction heads with different coating thicknesses, which significantly expands the application scenarios of the device. The adapter pipe is connected vertically with the air sampling instrument through a silica gel pipe, which simplifies the on-site operation and ensures the representativeness of the sampling. Compared with the traditional adsorption pipe which relies on expensive aging instruments and complex pretreatment, the device does not require additional desorption equipment and directly completes the analysis through GC-MS, reducing the equipment cost by more than 50%, and shortening the single detection time to within 30 minutes. In summary, the application realizes breakthroughs in method efficiency, device portability, and cost controllability, providing reliable technical support for real-time monitoring of atmospheric VOCs. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a micro-extraction head adapter pipe structure schematic diagram in the embodiment of the application;

[0031] Figure 2 is a pipe connection schematic diagram in the embodiment of the application;

[0032] Figure 3 is the peak detection situation of atmospheric volatile organic compounds in embodiment 1 of the application;

[0033] Figure 4 is the peak detection situation of atmospheric volatile organic compounds in embodiment 2 of the application.

[0034] In the figure: 1, gas inlet; 2, gas inlet pipe; 3, adapter port; 4, pipe belly; 5, gas outlet pipe; 6, gas outlet; 7, micro-extraction head; 8, air sampling instrument; 9, adsorption fiber; 10, adsorption bottle hanger. DETAILED DESCRIPTION

[0035] In order to enable personnel in the art to better understand the application scheme, the technical solutions of the application will be further described in detail below in combination with the embodiments of the application and the drawings. Obviously, the described embodiments are only a part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the application.

[0036] It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other without conflict. The application will be described in detail below in combination with the embodiments.

[0037] The application provides a method suitable for solid-phase micro-extraction collection and determination of atmospheric volatile organic compounds, and the specific implementation process is as follows:

[0038] Microextraction Head 7 Adapter Tube: Microextraction Head 7 adapter tubes are designed and manufactured according to requirements, as shown in the attached document. Figure 1 As shown, it is divided into three parts: air inlet tube 2, tube body 4, and air outlet tube 5. Tube body 4 is equipped with an adapter port 3. The inner diameter of the adapter port 3 is slightly larger than the handle of the microextraction head 7. The air inlet tube 2 of the microextraction head 7 adapter tube is 30cm long and has an inner diameter of 1cm; the tube body 4 is 10cm long and has an inner diameter of 3cm; the air outlet tube 5 is 15cm long and has an inner diameter of 1cm. The adapter port 3 is located in the tube body 4, 5.5cm from the bottom of the tube body 4, and has an inner diameter of 1.5cm, so that the installed microextraction head 7 kit can be smoothly inserted into the tube.

[0039] Equipment connection and preparation before sampling: see attached. Figure 2 As shown, place and fix the atmospheric sampler at the sampling point, erect and fix the microextraction head 7 adapter tube on the atmospheric sampler, adjust the air inlet 1 of the adapter tube to a suitable sampling height, connect one end of the silicone tube to the air outlet 5 of the adapter tube, and connect the other end to the air inlet 1 of the atmospheric sampler, connect the aged microextraction head 7 to the guide and install it on the handle, and insert the handle of the assembled microextraction head 7 kit into the adapter port 3 of the adapter tube.

[0040] Atmospheric volatile organic compound sampling: Turn on the atmospheric sampler, set the ventilation flow rate and sampling time according to the actual situation, push the adsorption fiber 9 in the microextraction head 7 out of the handle to an appropriate length, so that most of it is exposed at the junction of the adapter tube 4 and the air inlet tube 2, but do not let it contact the glass tube wall. The airflow enters through the air inlet tube 2 and flows through the fiber, and then enters the atmospheric sampler's air inlet tube 2 from the air outlet tube 5 and is discharged. After the sampling time is reached, carefully retract the fiber of the microextraction head 7 into the microextraction head 7, and then take out the microextraction head 7 kit from the adapter port 3. Measure the sample within 24 hours.

[0041] Determination of atmospheric volatile organic compounds: The microextraction head 7, assembled with the handle, is inserted into the manual injection port of the gas chromatography-mass spectrometry (GC-MS) instrument. The fiber is pushed out, and desorption is performed at the set high-temperature injection port for a certain period of time. Helium is used as the carrier gas to carry the desorbed volatile organic compounds into the gas chromatograph. Mass spectrometry is used for detection. Peaks at different retention times are qualitatively analyzed by comparing with a standard database. Specific substances are used as internal standards to quantitatively analyze the separated and detected compounds and calculate the content of each component.

[0042] Example 1: Sampling and determination of atmospheric volatile organic compounds in banyan forests

[0043] 1. Sampling site and equipment preparation

[0044] A ficus grove was chosen as the sampling site. The air sampling instrument (QS-1S) was connected to a tripod and set up in the ficus grove. The microextraction head 7 adapter tube was straightened and fixed to the air sampling instrument, with the inlet tube 2 mouth adjusted to 1.5 m high. One end of the silica gel tube was connected to the outlet tube 5 of the adapter tube, and the other end was connected to the air sampling instrument inlet 1. The aged solid phase microextraction head 7 (100 μm) was connected to the guide, and then installed with the handle. The handle of the assembled microextraction head 7 kit was inserted into the adapter port 3 of the adapter tube.

[0045] 2. Sampling process

[0046] The air sampling instrument (QS-1S) switch was turned on, the ventilation flow rate was set to 1.5 L / min, the sampling time was set to 60 min, and the air pumping was started. The adsorption fiber 9 in the microextraction head 7 was carefully pushed out of the handle to the longest, so that the fiber was mostly exposed at the junction of the tube belly 4 and the inlet tube 2, but not in contact with the glass tube wall. The air flow entered through the inlet tube 2 and flowed through the fiber, and then entered the air sampling instrument inlet tube 2 from the outlet tube 5, and was discharged from the air sampling instrument. After pumping for 60 min, the microextraction head 7 fiber was carefully retracted into the microextraction head 7, and then the microextraction head 7 kit was removed from the adapter port 3, and was measured on the instrument within 24 h.

[0047] 3. Measurement process

[0048] The microextraction head 7 assembled with the handle was inserted into the manual injection port of the Agilent gas chromatograph-mass spectrometer (7890A gas chromatograph + 5975C mass spectrometer detector), the fiber was pushed out, desorbed at 250℃ in the injection port for 5 min, and the desorbed volatile organic compounds were carried into the gas chromatograph with helium as the carrier gas. The GC conditions were as follows: DB-1MS capillary column (60 m x 250 μm, 0.25 μm); temperature program: initial temperature 40℃, then increased to 240℃ at 6℃ / min, and maintained for 12 min. The carrier gas was helium, the flow rate was 1.0 mL / min, and the splitless injection was used. The MS conditions were as follows: electron ionization source, ion source temperature 230℃, interface temperature 230℃; electron energy 70 eV, mass scan range (m / z) 35-500. The peaks with different retention times were qualitatively analyzed by comparing the NIST database, and the substances with a matching degree greater than 70% were reserved. 100 μg / mL n-hexane was used as the internal standard for quantitative analysis of the separated and detected compounds. The ratio of the peak area of each component to the peak area of the internal standard was calculated, and the product of the internal standard content was obtained to calculate the content of each component. The peak detection of atmospheric volatile organic compounds is shown in the following table. Figure 3

[0049] Example 2: Sampling and measurement of atmospheric volatile organic compounds in urban square

[0050] 1. Sampling site and equipment preparation ​

[0051] A square open space was chosen as the sampling site. The air sampling instrument (QS-1S) was connected to a tripod and set up on the square open space. The microextraction head 7 adapter tube was straightened and fixed to the air sampling instrument with the inlet tube 2 mouth adjusted to 1.5 m high. The end of the silica gel tube was connected to the outlet tube 5 of the adapter tube and the other end was connected to the inlet port 1 of the air sampling instrument. The aged solid phase microextraction head 7 (100 μm) was connected to the guide and then to the handle. The handle of the assembled microextraction head 7 kit was inserted into the adapter port 3 of the adapter tube.

[0052] 2. Sampling procedure

[0053] The air sampling instrument (QS-1S) was turned on with the air flow set at 1.3 L / min and the sampling time set at 90 min. The sampling was started. The adsorption fiber 9 in the microextraction head 7 was carefully pushed out of the handle to the longest length so that the fiber was mostly exposed at the junction of the tube belly 4 and the inlet tube 2 but not in contact with the glass tube wall. The air flow entered through the inlet tube 2 and flowed through the fiber, exited from the outlet tube 5 into the air sampling instrument inlet tube 2 and then out of the air sampling instrument. After 90 min of sampling, the fiber was carefully retracted into the microextraction head 7 and the microextraction head 7 kit was removed from the adapter port 3 and analyzed on the instrument within 24 h.

[0054] 3. Analysis procedure

[0055] The microextraction head 7 assembled with the handle was inserted into the manual injection port of the Agilent GC-MS (7890A GC + 5975C MS detector) and the fiber was pushed out to be desorbed at 250 °C for 5 min. The desorbed volatile organic compounds were carried into the GC by helium as the carrier gas. The GC conditions were as follows: DB-1MS capillary column (60 m x 250 μm, 0.25 μm); temperature program: initial temperature 40 °C, then increased to 240 °C at 6 °C / min and maintained for 12 min. The carrier gas was helium with a flow rate of 1.0 mL / min and the sample was injected without splitting. The MS conditions were as follows: electron ionization source, ion source temperature 230 °C, interface temperature 230 °C; electron energy 70 eV, mass scan range (m / z) 35-500. The peaks with different retention times were qualitatively analyzed by comparing the NIST database, and the substances with a matching degree greater than 70% were reserved. The separated and detected compounds were quantitatively analyzed by taking 100 μg / mL n-hexane as the internal standard. The content of each component was calculated by multiplying the ratio of the peak area of each component to the peak area of the internal standard by the content of the internal standard. The detected peak situation of the atmospheric volatile organic compounds is shown in the accompanying Figure 4

[0056] The accompanying Figure 3 Ficus grove and the accompanying Figure 4 ​The detection spectrum of atmospheric VOCs is shown in the figure. The chromatographic peaks are sharp and the baseline is separated, indicating that the DB-1MS capillary column (60m x 250μm) combined with programmed temperature (40℃→240℃) realizes high-efficiency separation of compounds with wide boiling range. The n-hexane peak (100μg / mL internal standard) with fixed retention time in the spectrum is used as a quantitative reference, and the content of each target component is calculated by the ratio of peak area to internal standard peak area. The difference between the two figures directly reflects the environmental characteristics:

[0057] The Figure 3 The terpenes (such as α-pinene, limonene) are the main peak group, which represents the vegetation source VOCs of the fig forest;

[0058] The Figure 4 The benzene series (such as benzene, toluene) and alkane peak group are the characteristics, which represent the motor vehicle / industrial emission source of the urban square. All peaks are qualitatively determined by m / z 35-500 full scan matching NIST database (matching degree >70%), which verifies the monitoring ability of the device in the open environment for different source VOCs and the reliability of the method.

[0059] The above specific embodiments are only an explanation of the present application, which is not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, as long as the modifications are within the scope of the claims of the present application, which is protected by the patent law.

Claims

1. A method for collecting and determining atmospheric volatile organic compounds, characterized in that: Includes the following steps: S1: Connect the microextraction head (7) adapter tube to the atmospheric sampler and insert the solid phase microextraction head (7) kit into the adapter port (3); S2: Set the sampling flow rate of the atmospheric sampler to 1.0–2.0 L / min and the sampling time to 30–120 minutes; S3: Push the micro-extraction head (7) and adsorb the fiber (9) to the intersection of the adapter tube (4) and the air inlet tube (2) to perform dynamic airflow sampling; S4: After sampling, the fibers are recovered and detected by gas chromatography-mass spectrometry within 24 hours.

2. The method as described in claim 1, characterized in that: The sampling flow rate is preferably 1.3 to 1.5 L / min, and the sampling time is preferably 60 to 90 minutes.

3. The method as described in claim 1, characterized in that: The gas chromatograph-mass spectrometer has a desorption temperature of 250℃, a desorption time of 5 minutes, helium as the carrier gas, and a flow rate of 1.0 mL / min.

4. The method as described in claim 1, characterized in that: The gas chromatography used a DB-1MS capillary column, with a temperature program of starting at 40°C, increasing to 240°C at a rate of 6°C / min, and holding for 12 minutes.

5. The method as described in claim 1, characterized in that: The electron ionization source temperature of the mass spectrometer detector is 230℃, and the mass scan range is m / z 35~500.

6. The method as described in claim 1, characterized in that: In the detection process described in step S4, n-hexane is used as an internal standard at a concentration of 100 μg / mL for quantitative analysis of various volatile organic compounds.

7. The method as described in claim 1, characterized in that: The inlet tube (2), tube belly (4), and outlet tube (5) of the microextraction head (7) adapter tube are made of inert polymer.

8. The method as described in claim 1, characterized in that: The microextraction head (7) adapter tube is detachable and replaceable, and can be adapted to solid phase microextraction head (7) kits of different specifications.

9. The method as described in claim 1, characterized in that: The detection results were qualitatively analyzed by comparing them with the NIST standard database, with a matching threshold of greater than 70%, and the content of each component was calculated based on the internal standard method.

10. An apparatus for collecting and measuring atmospheric volatile organic compounds, characterized in that: Includes the following components: The microextraction head (7) adapter tube includes an air inlet tube (2), a tube belly (4), and an air outlet tube (5); The atmospheric sampler is connected to the outlet tube (5) of the adapter tube of the microextraction head (7) via a silicone tube; Solid phase microextraction head (7) kit, including microextraction head (7), guide and handle, can be inserted into the adapter port (3) of the adapter tube of the microextraction head (7); Gas chromatography-mass spectrometry (GC-MS) is used for the desorption and detection of adsorbed volatile organic compounds.

11. The apparatus of claim 10, characterized in that: The inlet tube (2) of the microextraction head (7) adapter tube is 30cm long and has an inner diameter of 1cm; the tube belly (4) is 10cm long and has an inner diameter of 3cm; the outlet tube (5) is 15cm long and has an inner diameter of 1cm.

12. The apparatus of claim 10, characterized in that: The adapter port (3) is located in the tube belly (4) part, 5.5cm away from the bottom of the tube belly (4), with an inner diameter of 1.5cm, and is used to fix the handle of the microextraction head (7) kit.

13. The apparatus of claim 10, characterized in that: The adsorption fiber (9) of the solid-phase microextraction head (7) is made of a 100μm coating, which can be exposed to and adsorb volatile organic compounds in dynamic airflow.

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