Method for determining the content of polychlorobenzenes and polychlorobutadienes in ambient air

Abstract

The application discloses a method for determining the content of polychlorobenzene and polychlorobutadiene in ambient air, which comprises the following steps: (1) using a composite adsorption tube to adsorb and collect target substances in air, and then pressurizing and sealing the composite adsorption tube after the collection is completed; (2) placing the composite adsorption tube with the adsorbed target substances in a thermal desorption instrument to perform primary thermal desorption, and then introducing the target substances into a gas chromatography mass spectrometry analysis system after secondary focusing by a cold trap for analysis; the target substances are polychlorobenzene and polychlorobutadiene. The method can realize synchronous and accurate qualitative and quantitative analysis of wide-boiling-point chlorine-containing organic substances in a complex environmental matrix.

Description

Technical Field

[0001] This invention relates to the field of environmental technology, and in particular to a method for determining the content of polychlorinated benzenes and polychlorinated butadienes in ambient air. Background Technology

[0002] Polychlorinated benzenes (CBs) and polychlorinated butadienes (CBDs) are a class of chlorinated semi-volatile organic pollutants with high toxicity, bioaccumulation, and long-distance migration characteristics, posing significant environmental and human health risks.

[0003] Currently, the detection of polychlorinated benzenes and polychlorinated butadienes in ambient air mostly employs high-flow-rate sampling combined with adsorption material enrichment, solvent elution or solvent extraction, concentration and purification, followed by analysis using gas chromatography-mass spectrometry (GC-MS). This type of method is technically mature and has a certain application foundation, but it suffers from problems such as cumbersome pretreatment, long processing time, easy introduction of solvent contamination, significant loss of target analytes, and limited sensitivity. For example, Chinese patent document CN101126751A discloses a method for detecting organochlorine pesticides in the atmosphere using gas chromatography-ion trap tandem mass spectrometry, in which gaseous samples are extracted and concentrated using an extraction solvent before detection by GC-ion trap mass spectrometry.

[0004] Chinese patent document CN109521126A discloses a method for determining the content of 16 polycyclic aromatic hydrocarbons in incense smoke by thermal desorption / gas chromatography-mass spectrometry. The method involves igniting the sample and collecting it with a thermal adsorption tube. The doors and windows are closed during the collection process. The collection time is 40 minutes, the flow rate is 0.5 L / min, and a total of 20 L of smoke is collected in the adsorption tube.

[0005] Polychlorinated benzenes and polychlorinated butadiene homologues exhibit significant differences in volatility and a wide range of boiling points, making it difficult for a single adsorbent material to simultaneously achieve efficient enrichment of both low-boiling-point and high-boiling-point components. Furthermore, existing methods are inconvenient for sample preservation, often requiring analysis to be completed within 24 hours of sampling, which greatly increases the cost of sample collection and analysis. Summary of the Invention

[0006] This invention provides a method for simultaneous detection of polychlorinated benzene and polychloroprene in ambient air, enabling efficient, rapid, and repeatable simultaneous quantitative analysis of polychlorinated benzene and polychloroprene in ambient air.

[0007] The technical solution of the present invention is as follows: A method for determining the content of polychlorinated benzenes and polychlorinated butadienes in ambient air, comprising the following steps: (1) Use composite material adsorption tube to adsorb and collect target objects in the air, and pressurize and seal the composite material adsorption tube after collection; (2) The composite material adsorption tube with the target adsorbed is placed in a thermal desorption instrument for primary thermal desorption, and then introduced into a gas chromatography-mass spectrometry analysis system for analysis after secondary focusing through a cold trap. The target substances are polychlorinated benzene and polychlorinated butadiene.

[0008] Preferably, the filler in the composite material adsorption tube is 2,6-diphenylfuran porous polymer resin and graphitized carbon black, and the ratio of 2,6-diphenylfuran porous polymer resin to graphitized carbon black is 7:1~3.

[0009] Preferably, the composite material adsorption tube contains an isotope-labeled internal standard; the isotope-labeled internal standard is selected from 1,2-dichlorobenzene-d4 (1,2-DiCB-d4), 1,2,4-trichlorobenzene-d3 (1,2,4-TrCB-d3), 13C6-tetrachlorobenzene (13C6-TeCB), 13C6-pentachlorobenzene (13C6-PeCB), 13C6-hexachlorobenzene (13C6-HCB), 13C4-hexachlorobutadiene (13C4-HCBD) and 1,2,3,4-tetrachlorobenzene-d2 (1,2,3,4-TeCB-d2).

[0010] Preferably, in step (1), when using the composite material adsorption tube to adsorb and collect polychlorinated benzene and polychlorinated butadiene in the air, the sampling flow rate is 0.1~0.5L / min and the total sampling volume is 5~10L.

[0011] Preferably, in step (1), after the collection is completed, the composite material adsorption tube is pressurized and sealed so that the gas pressure inside the composite material adsorption tube is 180~220kPa.

[0012] After sample collection, the composite material containing the target substance is preserved under high pressure by pressurization and sealing, which increases the adsorption effect of the target substance on the composite material and reduces the escape of volatile target substances from the composite material.

[0013] Based on the high-pressure sealed adsorption tube preservation technology, the target substance is still well preserved after the sample is placed at room temperature for 72 hours after collection. The sample recovery rate is basically not reduced compared with 24 hours, and the recovery rate is significantly improved compared with the normal pressure preservation conditions.

[0014] Preferably, in step (2), the thermal desorption analysis conditions are as follows: high-purity nitrogen is used as the carrier gas, with a flow rate of 30~50 mL / min; the transfer line temperature is 130~160℃; the pre-desorption time of the adsorption tube is 1~2 min; the primary thermal desorption temperature is 280~300℃, and the primary thermal desorption time is 5~10 min; the cold trap temperature is -20~-10℃, and the heating rate is 20~40℃ / min; the secondary thermal desorption temperature is 250~320℃, and the secondary thermal desorption time is 3~5 min; and the split ratio is 1~5:1.

[0015] Further preferred, in step (2), the thermal desorption analysis conditions are as follows: high-purity nitrogen is used as the carrier gas, the flow rate is 50 mL / min; the transfer line temperature is 140℃; the pre-desorption time of the adsorption tube is 1 min; the first-stage thermal desorption temperature is 280℃, the first-stage thermal desorption time is 10 min; the cold trap temperature is -20℃, the heating rate is 40℃ / min; the second-stage thermal desorption temperature is 320℃, the second-stage thermal desorption time is 3 min; and the split ratio is 5:1.

[0016] Preferably, in step (2), the gas chromatography-mass spectrometry analysis conditions are as follows: the chromatographic column used for separation is a (5%-phenyl)-methylpolysiloxane coated inert quartz capillary, the column length is 30~60 m, the inner diameter is 0.25~0.32 mm, and the coating thickness is 0.25~1.0 μm; the gas injection port temperature is 250℃; the carrier gas is high-purity helium, constant flow mode, and the flow rate is 1.0~1.5 mL / min; splitless injection, sample injection volume is 1~2 μL; column temperature program: initial temperature 50~80℃, hold for 1 min; increase to 110~130℃ at 5~10℃ / min, hold for 3~5 min; then increase to 200~230℃ at 15~20℃ / min; finally increase to 300~320℃ at 25~30℃ / min, hold for 3~5 min; mass spectrometry conditions are: ionization energy 50~70 eV, ion source temperature 230~250℃; quantitative analysis was performed using multiple reaction monitoring mode.

[0017] Further preferred, in step (2), the gas chromatography-mass spectrometry (GC-MS) analysis conditions are as follows: the chromatographic column is an Agilent DB-5MS quartz column, with a length of 60 m, an inner diameter of 0.25 mm, and a coating thickness of 0.25 μm; the gas inlet temperature is set to 250℃; the carrier gas is high-purity helium (purity ≥99.999%), using constant flow mode at a flow rate of 1.0 mL / min; splitless injection is used, with a sample injection volume of 1 μL. The column oven temperature program is as follows: initial temperature 50℃, held for 1 min; increased to 110℃ at 10℃ / min, held for 5 min; then increased to 200℃ at 15℃ / min; finally increased to 300℃ at 30℃ / min, held for 5 min; the mass spectrometry conditions are: ionization energy 70 eV; ion source temperature 230℃; and quantitative analysis is performed using multiple reaction monitoring mode.

[0018] Preferably, the target substances include hexachlorobenzene, pentachlorobenzene, 1,2,3,4-tetrachlorobenzene, 1,2,3,5-tetrachlorobenzene, 1,2,4,5-tetrachlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,2-dichlorobenzene, 1,3,5-trichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, as well as hexachlorobutadiene, 1,1,2,3,4-pentachloro-1,3-butadiene, 1,1,2 At least one of 4,4-pentachloro-1,3-butadiene, 1,1,2,3-tetrachloro-1,3-butadiene, 1,1,2,4-tetrachloro-1,3-butadiene, (E)-1,1,3,4-tetrachloro-1,3-butadiene, (Z)-1,1,3,4-tetrachloro-1,3-butadiene, 1,1,4,4-tetrachloro-1,3-butadiene, and 1,2,3,4-tetrachloro-1,3-butadiene.

[0019] Preferably, the qualitative and quantitative ions and collision energies of the target analyte are as follows: The method of this invention enables simultaneous, accurate qualitative and quantitative analysis of chlorinated organic compounds with wide boiling points from complex environmental matrices.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention achieves efficient enrichment and analysis of gaseous polychloroprene and polychlorobenzene through composite material adsorption and thermal desorption technology. The method of the present invention does not require solvent extraction, simplifies the pretreatment process, and reduces pollution and error. (2) This invention improves sample introduction efficiency and detection sensitivity through thermal desorption and cold trap focusing; and improves method selectivity and quantitative accuracy through MRM mode; (3) The method of the present invention has a low detection limit, good recovery rate and precision, and is suitable for the analysis of air samples in complex environments with low concentrations; (4) This invention can be used for routine monitoring of polychlorinated benzene and polychlorinated butadiene in ambient air and indoor air, providing technical support for environmental risk assessment and pollution control.

[0021] (5) The present invention can achieve efficient preservation of samples at room temperature after collection, and the target substance can still maintain an average recovery rate of over 85% after 72 hours. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the sampling device structure of the present invention; Figure 2 This is a schematic diagram of a pressurized preservation method for adsorption tubes; Figure 3 This is a schematic diagram of another pressurized preservation method for adsorption tubes. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0024] The method for simultaneous determination of polychlorinated benzene and polychlorinated butadiene content in ambient air according to the present invention includes the following steps: 1. Sample Collection: Air samples were collected using an atmospheric sampling pump connected to a composite adsorption tube (a stainless steel tube with an outer diameter of 6.35 mm, an inner diameter of 4.95 mm, and a length of 89.0 mm, internally filled with 175 mg of 2,6-diphenylfuran porous polymer resin and 75 mg of graphitized carbon black in layers). To ensure data reliability and repeatability, four parallel sampling pathways were designed, such as... Figure 1 As shown, the first and second paths use two adsorption tubes connected in series for sampling, while the third and fourth paths use a single adsorption tube. In the series-flow path, an isotope internal standard is added to the adsorption tube at the distal end of the gas pump before sampling. This serves two purposes: firstly, to perform internal standard correction on the sample, and secondly, to monitor whether the target chemical substance penetrates the preceding adsorption tube.

[0025] The isotope-labeled internal standards used in this invention are: 1,2-dichlorobenzene-d4 (1,2-DiCB-d4), 1,2,4-trichlorobenzene-d3 (1,2,4-TrCB-d3), 13C6-tetrachlorobenzene (13C6-TeCB), 13C6-pentachlorobenzene (13C6-PeCB), 13C6-hexachlorobenzene (13C6-HCB), 13C4-hexachlorobutadiene (13C4-HCBD), and 1,2,3,4-tetrachlorobenzene-d2 (1,2,3,4-TeCB-d2) (Cambridge Isotope Laboratories, USA). The sampling flow rate was set to 0.5 L / min, the sampling time to 10 min, and the total sampling volume to 5 L.

[0026] 2. Preservation of the adsorption tube: After sample collection, immediately seal one end of the adsorption tube with a clamping cap, and simultaneously connect the other end to high-pressure nitrogen gas for pressurization. Set the gas pressure inside the tube to 200 kPa. Once the pressure is reached, seal the tube using the valve (e.g., ...). Figure 2 (As shown). The internal air pressure can effectively increase the fixation effect of the composite material on volatile organic compounds. In field settings or where high-pressure gas cylinders are unavailable, pre-pressurized empty adsorption tubes of the same model and size can be connected for sample pressurization and sealing preservation (e.g., ...). Figure 3 (As shown): First, pressurize the same type of clean adsorption tubes to 300 kPa in the laboratory with clean nitrogen and seal them. After the adsorption tubes have been used to collect samples on site, connect the adsorption tubes with the airflow inlet to the inlet. Then open the valve to balance the pressure of the two adsorption tubes at about 200 kPa. Store them at normal pressure. Then, analyze the sample concentration in the adsorption tubes on both sides in the laboratory. The sum of the concentrations measured by the two adsorption tubes is taken as the final measured concentration of the sample.

[0027] 3. Sample thermal desorption analysis: High-purity nitrogen was used as the carrier gas at a flow rate of 50 mL / min; the transfer line temperature was 140 ℃; the pre-desorption time of the adsorption tube was 1 min; the first-stage thermal desorption temperature was 280 ℃ and the first-stage thermal desorption time was 10 min; the cold trap temperature was -20 ℃ and the heating rate was 40 ℃ / min; the second-stage thermal desorption temperature was 320 ℃ and the second-stage thermal desorption time was 3 min; the split ratio was 5:1.

[0028] 4. Target Mass Spectrometry Analysis: The concentration of polychloroprene was analyzed using GC-MS. A DB-5MS flexible quartz capillary column (60 m × 0.25 mm × 0.25 μm) was used; the injection port temperature was 250 ℃; the carrier gas was high-purity helium (purity ≥ 99.999%), constant flow mode, flow rate 1.0 mL / min; splitless injection (injection volume 1 μL). Column temperature program: initial temperature 50 ℃, hold for 1 min; increase to 110 ℃ at 10 ℃ / min, hold for 5 min; then increase to 200 ℃ at 15 ℃ / min; finally increase to 300 ℃ at 30 ℃ / min, hold for 5 min. Mass spectrometry conditions: ionization energy 70 eV; ion source temperature 230 ℃; multiple reaction monitoring (MRM) mode was used for quantitative analysis.

[0029] The qualitative and quantitative ions, collision energies, and retention times of the target analytes are shown in Table 1. Table 1 Prepare mixed standard solutions with mass concentration gradients of 1, 5, 10, 50, and 100 mg / L, and analyze them according to the thermal desorption tandem gas chromatography-mass spectrometry method established above. Plot a standard curve with the mass concentration of the target substance as the abscissa and the peak area as the ordinate.

[0030] The results showed that the 20 target compounds exhibited good linearity in the range of 1-100 µg / L, with correlation coefficients (r) ranging from 0.9954 to 0.9997, as shown in Table 2.

[0031] The method detection limit was calculated using a signal-to-noise ratio of 3. The calculated method detection limit for each target was 1.06-4.70 ng in an actual air sampling volume of 5 L, indicating that the method has extremely high sensitivity and meets the monitoring requirements for trace targets in the air.

[0032] Table 2 Example 1 To verify the practical applicability of the method of the present invention, a sampling point was set up in a typical urban area in January 2026. Through the measurement and evaluation of the present invention, the pollution of CBs and CBDs in indoor air was quantitatively analyzed, and the results are shown in Table 3.

[0033] The test results showed that a total of 12 target compounds (including 10 CBs and 2 PCBDs) were detected in the actual sample, with a total exposure concentration of approximately 100 ng / m³. 3 Among them, 1,4-dichlorobenzene (1,4-DiCB) was the primary pollutant, with a concentration as high as 59.6 ng / m³. 3 It accounted for nearly 60% of the total detected amount; followed by hexachlorobutadiene (HCBD), with a concentration of 20.3 ng / m³. 3 (Approximately 20%); other components include 1,2,4-trichlorobenzene (7.97 ng / m³). 3 ), 1,2-dichlorobenzene (6.11 ng / m 3 The concentrations of substances such as [list of substances] are relatively low.

[0034] The results show that the high-pressure sealed adsorption tube preservation technology exhibits excellent target substance retention after the sample is placed at room temperature (20 degrees Celsius) for 72 hours following collection. The sample recovery rate is essentially unchanged compared to 24 hours, and the recovery rate is significantly improved compared to atmospheric pressure preservation conditions. The method of this invention enables simultaneous and accurate quantification of broad-boiling-point chlorinated organic compounds in complex matrices.

[0035] Table 3

[0036] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining the content of polychlorinated benzenes and polychlorinated butadienes in ambient air, characterized in that, Includes the following steps: (1) Use composite material adsorption tube to adsorb and collect target objects in the air, and pressurize and seal the composite material adsorption tube after collection; (2) The composite material adsorption tube with the target adsorbed is placed in a thermal desorption instrument for primary thermal desorption, and then introduced into a gas chromatography-mass spectrometry analysis system for analysis after secondary focusing through a cold trap. The target substances are polychlorinated benzene and polychlorinated butadiene.

2. The method for determining the content of polychlorinated benzenes and polychlorinated butadienes in ambient air according to claim 1, characterized in that, The filler in the composite material adsorption tube is 2,6-diphenylfuran porous polymer resin and graphitized carbon black, and the ratio of 2,6-diphenylfuran porous polymer resin to graphitized carbon black is 7:1~3.

3. The method for determining the content of polychlorinated benzenes and polychlorinated butadienes in ambient air according to claim 1, characterized in that, The composite material adsorption tube contains an isotope-labeled internal standard; the isotope-labeled internal standard is selected from 1,2-dichlorobenzene-d4, 1,2,4-trichlorobenzene-d3, 13C6-tetrachlorobenzene, 13C6-pentachlorobenzene, 13C6-hexachlorobenzene, 13C4-hexachlorobutadiene, and 1,2,3,4-tetrachlorobenzene-d2.

4. The method for determining the content of polychlorinated benzenes and polychlorinated butadienes in ambient air according to claim 1, characterized in that, In step (1), when using composite material adsorption tubes to adsorb and collect polychlorinated benzene and polychlorinated butadiene in the air, the sampling flow rate is 0.1~0.5 L / min and the total sampling volume is 5~10L.

5. The method for determining the content of polychlorinated benzenes and polychlorinated butadienes in ambient air according to claim 1, characterized in that, In step (1), after the collection is completed, the composite material adsorption tube is pressurized and sealed so that the gas pressure inside the composite material adsorption tube is 180~220kPa.

6. The method for determining the content of polychlorinated benzenes and polychlorinated butadienes in ambient air according to claim 1, characterized in that, In step (2), the thermal desorption analysis conditions are as follows: high-purity nitrogen is used as the carrier gas, with a flow rate of 30~50 mL / min; the transfer line temperature is 130~160℃; the pre-desorption time of the adsorption tube is 1~2 min; the first-stage thermal desorption temperature is 280~300℃, and the first-stage thermal desorption time is 5~10 min; the cold trap temperature is -20~-10℃, and the heating rate is 20~40℃ / min; the second-stage thermal desorption temperature is 250~320℃, and the second-stage thermal desorption time is 3~5 min. The split ratio is 1 to 5:

1.

7. The method for determining the content of polychlorinated benzenes and polychlorinated butadienes in ambient air according to claim 1, characterized in that, In step (2), the analytical conditions of the gas chromatography-mass spectrometry analyzer are as follows: the chromatographic column used for separation is a (5%-phenyl)-methylpolysiloxane coated inert quartz capillary, with a column length of 30~60 m, an inner diameter of 0.25~0.32 mm, and a coating thickness of 0.25~1.0 μm; the gas injection port temperature is 250℃; the carrier gas is high-purity helium, constant flow mode, and a flow rate of 1.0~1.5 mL / min; splitless injection, with a sample injection volume of 1~2 μL; the column temperature program is as follows: initial temperature 50~80℃, hold for 1 min; increase to 110~130℃ at 5~10℃ / min, hold for 3~5 min; then increase to 200~230℃ at 15~20℃ / min; finally increase to 300~320℃ at 25~30℃ / min, hold for 3~5 min; the mass spectrometry conditions are: ionization energy 50~70 eV, ion source temperature 230~250℃; quantitative analysis was performed using multiple reaction monitoring mode.

8. The method for determining the content of polychlorinated benzenes and polychlorinated butadienes in ambient air according to claim 1, characterized in that, The target substances include hexachlorobenzene, pentachlorobenzene, 1,2,3,4-tetrachlorobenzene, 1,2,3,5-tetrachlorobenzene, 1,2,4,5-tetrachlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,2-dichlorobenzene, 1,3,5-trichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, as well as hexachlorobutadiene, 1,1,2,3,4-pentachloro-1,3-butadiene, 1,1,2,4-dichlorobenzene, etc. At least one of 4-pentachloro-1,3-butadiene, 1,1,2,3-tetrachloro-1,3-butadiene, 1,1,2,4-tetrachloro-1,3-butadiene, (E)-1,1,3,4-tetrachloro-1,3-butadiene, (Z)-1,1,3,4-tetrachloro-1,3-butadiene, 1,1,4,4-tetrachloro-1,3-butadiene, and 1,2,3,4-tetrachloro-1,3-butadiene.

9. The method for determining the content of polychlorinated benzenes and polychlorinated butadienes in ambient air according to claim 8, characterized in that, The qualitative and quantitative ions and collision energies of the target analyte are shown below: 。

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