Qualitative and semi-quantitative synchronous detection method for micro-plastic and polycyclic aromatic hydrocarbon loaded by micro-plastic in environmental water body

Abstract

The invention discloses a qualitative and semi-quantitative synchronous detection method for micro-plastics and polycyclic aromatic hydrocarbons loaded on the micro-plastics in an environmental water body. The method comprises the following steps: constructing a detection model for qualitative and semi-quantitative analysis of the micro-plastics and the polycyclic aromatic hydrocarbons loaded on the micro-plastics; determining detection conditions and setting instrument parameters; determining indication fragments corresponding to the target polycyclic aromatic hydrocarbon and the target micro-plastic; establishing a standard curve of each target polycyclic aromatic hydrocarbon and each target micro-plastic; the method comprises the following steps: collecting a to-be-detected environmental water sample, enriching micro-plastics in the to-be-detected environmental water sample, and sequentially carrying out thermal desorption-gas chromatography-mass spectrometry detection and thermal cracking-gas chromatography-mass spectrometry detection; and analyzing gas chromatography-mass spectrometry detection data according to the detection model to realize qualitative and semi-quantitative synchronous detection and analysis of the micro-plastics and the loaded polycyclic aromatic hydrocarbons in the environmental water body to be detected. The detection method provided by the invention can realize integrated sample treatment and qualitative and semi-quantitative analysis of micro-plastic-polycyclic aromatic hydrocarbon combined pollution in the environmental water body, and improves the detection efficiency and the comparability and integrity of data.

Description

Technical Field

[0001] This invention relates to the field of environmental testing technology, and in particular to a method for simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies. Background Technology

[0002] Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent organic pollutants composed of two or more fused benzene rings. They have significant carcinogenic, teratogenic, and mutagenic effects and are key toxic and hazardous substances monitored in drinking water and environmental water bodies. Current environmental monitoring methods for PAH determination mainly employ solid-phase extraction or liquid-liquid extraction combined with gas chromatography-mass spectrometry (GC-MS) or gas chromatography-tandem mass spectrometry (GC-MS). These methods typically require long extraction equilibration times and large amounts of organic solvents, involve complex sample pretreatment procedures, are prone to operational errors, and are not suitable for rapid detection of large batches of samples.

[0003] Microplastics (MPs) refer to plastic particles, fragments, or fibers with a particle size typically less than 5 mm. They are widely found in surface water, drinking water sources, and marine environments. Microplastics have a large specific surface area and are hydrophobic, making them prone to accumulating hydrophobic organic pollutants such as PAHs, posing a potential risk to aquatic ecosystems and human health. Current methods for microplastic detection mostly rely on microscopic observation combined with Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy for morphological and species identification. However, these methods struggle to accurately determine mass concentrations and have low detection throughput.

[0004] With the development of pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), existing techniques have proposed using characteristic pyrolysis products generated by polymers at high temperatures to achieve qualitative and quantitative analysis of microplastics such as polyethylene, polypropylene, and polystyrene. This allows for the determination of microplastic mass concentration without relying on visual counting or spectral imaging. However, current pyrolysis-GC-MS methods are mostly applicable to single or a few polymers, and are only used for the determination of microplastic mass concentration, without addressing the simultaneous detection of loaded polycyclic aromatic hydrocarbons (PAHs).

[0005] In real-world water bodies, polycyclic aromatic hydrocarbons (PAHs) can exist in dissolved form in the aqueous phase or be loaded onto the surfaces of suspended particulate matter and microplastics. Current techniques typically require separate sampling, pretreatment, and analysis of PAHs and microplastics: PAHs are purified using organic solvent extraction before instrumental analysis, while microplastics are detected using spectroscopic or pyrolysis methods. The detection procedures for these two types of pollutants are independent, making it difficult to obtain quantitative results for both PAHs and microplastics from the same sample. This fails to effectively characterize the complex pollution characteristics of "microplastic-PAH" composites in environmental water bodies.

[0006] Furthermore, existing pyrolysis-GC-MS methods for microplastics mostly focus on establishing standard curves for a specific type of plastic. When simultaneously quantifying multiple polymers, separate standard preparation and repeated testing are often required, limiting the method's throughput and applicability. For environmental monitoring departments, it is necessary to develop a method with a unified sample pretreatment process that can simultaneously quantify the mass concentrations of polycyclic aromatic hydrocarbons and multiple polymer microplastics on the same pyrolysis-GC-MS analysis platform. This would improve detection efficiency, reduce organic solvent usage, and provide reliable data support for the risk assessment of complex pollution in environmental water bodies. Summary of the Invention

[0007] This invention provides a method for simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies, realizing integrated sample processing and qualitative and semi-quantitative analysis of "microplastic-polycyclic aromatic hydrocarbon" complex pollution in environmental water bodies, improving detection efficiency and the comparability and integrity of data.

[0008] The technical solution of the present invention is as follows: A method for simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies includes the following steps: A thermal pyrolysis-gas chromatography-mass spectrometry detection model was constructed for the qualitative and semi-quantitative analysis of microplastics and their supported polycyclic aromatic hydrocarbons, including: (i) Change the pyrolysis system mode, and change the original single-stage pyrolysis mode to a single-stage thermal desorption plus two-stage pyrolysis mode; (ii) Determine the detection conditions and instrument parameter settings for polycyclic aromatic hydrocarbon thermal desorption-gas chromatography-mass spectrometry detection and microplastic thermal decomposition-gas chromatography-mass spectrometry detection; (iii) Identify the indicator fragments corresponding to the target polycyclic aromatic hydrocarbon and the target microplastic; (iv) Establish peak area-concentration standard curves for each target polycyclic aromatic hydrocarbon and peak area-mass standard curves for each target microplastic; (2) Collect water samples from the environment to be tested, and obtain the test samples by separating, flotation and ultrasonic enrichment of microplastics and their loaded polycyclic aromatic hydrocarbons; (3) Quantitatively transfer the sample to be tested and perform thermal desorption-gas chromatography-mass spectrometry detection and thermal pyrolysis-gas chromatography-mass spectrometry detection in sequence; analyze the gas chromatography-mass spectrometry detection data according to the detection model constructed in step (1) to realize the qualitative and semi-quantitative simultaneous detection and analysis of microplastics and their loaded polycyclic aromatic hydrocarbons in the water body to be tested.

[0009] The detection method of this invention can be used for the simultaneous monitoring and evaluation of organic pollutants and microplastic composite pollution in environmental water bodies such as drinking water sources, rivers and lakes.

[0010] The detection method of this invention employs a pyrolysis-gas chromatography-mass spectrometry (GC-MS) system, which includes a pyrolysis unit and a gas chromatograph-mass spectrometer connected in sequence. The thermally desorbed gas generated by thermal desorption in the pyrolysis unit, or the pyrolyzed gas generated by thermal pyrolysis in the pyrolysis unit, directly enters the gas chromatograph-mass spectrometer for GC-MS analysis.

[0011] The pyrolysis instrument was a CDS Pyroprobe 6150 pyrolysis instrument, and the gas chromatograph-mass spectrometer was a Shimadzu GC-MS TQ8050 gas chromatograph-triple quadrupole mass spectrometer. The chromatographic column was a DB-5ms (30m×0.25mm I.D.×0.25μm).

[0012] In step (i), the pyrolysis system mode is changed from the original single-stage pyrolysis mode to a two-stage combined mode of single-stage pyrolysis followed by two-stage pyrolysis. In this two-stage combined mode, the polycyclic aromatic hydrocarbons loaded on microplastics in the environmental water sample are first thermally desorbed, so that the target analytes are desorbed from the surface of the microplastics and enter the gas chromatograph. Then, a second-stage pyrolysis is performed, and deep pyrolysis is carried out at the preset pyrolysis temperature and time parameters to further release the pyrolyzed microplastic components. At the same time, the desorption and pyrolysis parameters are set and optimized in this process. Through parameter optimization, the efficient release and separation of the target analytes are achieved, thereby improving the sensitivity and accuracy of subsequent detection.

[0013] The target polycyclic aromatic hydrocarbon is at least one of naphthalene, acenaphthene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, indo(1,2,3-c,d)pyrene, dibenzo(a,h)anthene, and benzo(g,h,i)perylene.

[0014] The target microplastic is at least one of polycarbonate (PC), polyvinyl chloride (PVC), polystyrene (PS), polymethyl methacrylate (PMMA), polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET).

[0015] Preferably, in step (ii), the detection conditions for polycyclic aromatic hydrocarbon thermal desorption-gas chromatography-mass spectrometry detection are as follows: The thermal desorption conditions are as follows: nitrogen is used as the carrier gas, the furnace temperature is raised from 50~100℃ to 300~450℃ at a rate of 150~250℃ / min, and the furnace temperature is held for 10min after reaching the target furnace temperature; the interface and transmission line temperature is 280~320℃. The desorbed gas was analyzed by a gas chromatograph-mass spectrometer. The gas chromatographic conditions were as follows: injection port temperature 280-320℃; column temperature program: initial temperature 40-80℃, hold for 0.5-3 min, increase to 260-310℃ at 8-12℃ / min, then increase to 280-320℃ at 6-10℃ / min and hold for 7-12 min; splitless injection with a split ratio of 10-15:1; helium as carrier gas at a flow rate of 1.0 mL / min; and mass spectrometry conditions: transfer line temperature 280℃, ion source temperature 300℃, electron impact ionization mode, electron energy 70 eV, Q3 selected ion monitoring mode, and solvent delay time of 5-7 min.

[0016] More preferably, in step (ii), the detection conditions for polycyclic aromatic hydrocarbon thermal desorption-gas chromatography-mass spectrometry detection are as follows: The thermal desorption conditions are as follows: nitrogen is used as the carrier gas, the furnace temperature is raised from 80℃ to 350℃ at a rate of 150℃ / min, and held at 350℃ for 10min; the interface temperature is 290℃ and the transmission line temperature is 290℃. The desorbed gas was analyzed by a gas chromatograph-mass spectrometer. The gas chromatographic conditions were as follows: injection port temperature 290℃; column temperature program: initial 60℃ for 1 min, increased to 280℃ at 10℃ / min, then increased to 310℃ at 8℃ / min and held for 9 min; injection method: splitless injection, split ratio 10:1 after 0.75 min; carrier gas: helium, flow rate 1.0 mL / min; mass spectrometry conditions: transfer line temperature 280℃, ion source temperature 300℃, electron impact ionization (EI) mode, electron energy 70 eV, Q3 selected ion monitoring (SIM) mode, and solvent delay time set to 6 min.

[0017] Preferably, in step (ii), the detection conditions for microplastic pyrolysis-gas chromatography-mass spectrometry are as follows: The thermal decomposition conditions are as follows: nitrogen is used as the carrier gas, and thermal decomposition is carried out at 620~800℃ for 30~70s; the interface temperature is 270~330℃, the transmission line temperature is 310~340℃, and the valve box temperature is 290~330℃. The pyrolysis gas was analyzed by gas chromatography-mass spectrometry (GC-MS). The GC conditions were as follows: injection port temperature 280–340 °C; column temperature program: 36–42 °C for 0.75–1.5 min, ramped up to 140–160 °C at 10–25 °C / min and held for 0.8–1.6 min, ramped up to 270–310 °C at 8–12 °C / min and held for 6–10 min, and finally ramped up to 290–330 °C at 8–12 °C / min and held for 13–18 min; split ratio 20–60:1; carrier gas: helium at a flow rate of 1.0 mL / min. The mass spectrometry conditions were as follows: transfer line temperature 290–340 °C; ion source temperature 260–310 °C; electron impact ionization; electron energy 70 eV; Q3 full scan mode; scan range 40–1000 m / z.

[0018] More preferably, in step (ii), the detection conditions for microplastic pyrolysis-gas chromatography-mass spectrometry are as follows: The thermal decomposition conditions are as follows: nitrogen is used as the carrier gas, and thermal decomposition is carried out at 700℃ for 40s; the interface temperature is 300℃, the transmission line temperature is 320℃, and the valve box temperature is 300℃. The pyrolysis gas was analyzed by gas chromatography-mass spectrometry (GC-MS). The GC conditions were as follows: injection port temperature 320℃, column temperature program 40℃ for 1 min, ramping up to 150℃ at 20℃ / min and holding for 1 min, ramping up to 300℃ at 10℃ / min and holding for 8 min, and finally ramping up to 320℃ at 10℃ / min and holding for 15 min; split ratio 50:1, carrier gas helium at a flow rate of 1.0 mL / min; and mass spectrometry conditions 320℃ transfer line temperature, ion source temperature 280℃, electron impact ionization, electron energy 70 eV, Q3 full scan mode, and scan range 40–1000 m / z.

[0019] In step (iii), the indicator fragments of the target polycyclic aromatic hydrocarbon include quantitative ions and auxiliary qualitative ions; the quantitative ions and auxiliary qualitative ions are: Compound Name Quantitative Ion (m / z) Auxiliary Qualitative Ion (m / z) Naphthalene 128 129,127 Acenaphthylene 152 151,153 Acenaphthene 154 153,152 Fluorene 166 165,167 Phenanthrene 178 179,176 Anthracene 178 179,176 Fluoranthene 202 101,203 Pyrene 202 101,203 Benzo(a)anthracene 228 114,226,229 Chrysene 228 114,226,229 Benzo(b)fluoranthene 252 126,253 Benzo(k)fluoranthene 252 126,253 Benzo(a)pyrene 252 126,253 Indeno(1,2,3-c,d)pyrene 276 138,277 Dibenzo(a,h)anthracene 278 139,279 Benzo(g,h,i)perylene 276 138,277

[0020] Preferably, in step (iii), the indicator fragments of the target microplastic include characteristic fragment ions, quantitative ions, and auxiliary qualitative ions; the characteristic fragment ions, quantitative ions, and auxiliary qualitative ions are: Microplastics Characteristic Fragment Ion Quantitative Ion (m / z) Auxiliary Qualitative Ion (m / z) Polycarbonate Bisphenol A 213 119,228 Polyvinyl Chloride Naphthalene 128 102 Polystyrene 1,3,5-Triphenylcyclohexane 91 117,207 Polymethyl Methacrylate Methyl Methacrylate 69 99,100 Polypropylene 2,4-Dimethyl-1-heptene 55 43,70 Polyethylene 1-Decene 71 57,85 Polyethylene Terephthalate Vinyl Benzoate 105 77,51

[0021] Preferably, step (iv) includes: (iv-1) Prepare multiple standard solutions of various target polycyclic aromatic hydrocarbons with concentration gradients, and perform thermal desorption-gas chromatography-mass spectrometry detection and analysis. Perform qualitative and quantitative analysis according to the quantitative and qualitative ions of each target polycyclic aromatic hydrocarbon, and establish peak area-concentration standard curves for each target polycyclic aromatic hydrocarbon. (iv-2) Prepare multiple standard solutions with concentration gradients for various types of target microplastics, and perform thermal pyrolysis-gas chromatography-mass spectrometry detection and analysis. Perform qualitative and quantitative analysis according to the characteristic fragment ions, quantitative ions and auxiliary qualitative ions of each target microplastic, and establish the peak area-mass standard curve of each target microplastic.

[0022] In step (iv-1), the concentrations of the multiple standard solutions with concentration gradients are 10.0 μg / L, 25.0 μg / L, 50.0 μg / L, 100 μg / L, 250 μg / L, and 500 μg / L, respectively.

[0023] In step (iv-2), the concentrations of the multiple standard solutions with concentration gradients are 1000 mg / L, 100 mg / L and 10 mg / L, respectively.

[0024] Preferably, step (2) includes: Water samples were collected from the sampling points of the water body to be tested, and the water samples were filtered through a 1-1000μm filter membrane. After drying the filter membrane containing microplastics, density separation was performed using a saturated sodium chloride solution. After standing for 10-20 hours, the supernatant was taken and filtered through the filter membrane again. The filter membrane was rinsed and dried, and the microplastics on the filter membrane were transferred to methanol to obtain a microplastic-methanol suspension. The microplastic-methanol suspension was concentrated and transferred to a pyrolysis tube, then dried to obtain the sample to be tested for thermal desorption or pyrolysis analysis.

[0025] This step omits the digestion process, thus avoiding damage to the polycyclic aromatic hydrocarbons loaded on the microplastics and preserving the complete chemical information of the target pollutant.

[0026] Step (3) includes: (3-1) The organic matter loaded with microplastics was thermally desorbed at the mid-temperature end of the pyrolysis instrument. The desorbed gas was analyzed by gas chromatography-mass spectrometry. The polycyclic aromatic hydrocarbons in the thermally desorbed gas were qualitatively identified based on quantitative ions and auxiliary qualitative ions. The polycyclic aromatic hydrocarbons in the thermally desorbed gas were quantitatively identified based on the peak area-concentration standard curve of the target polycyclic aromatic hydrocarbons. (3-2) The microplastics after thermal desorption are thermally decomposed at the high-temperature end of the thermal pyrolysis instrument. The pyrolysis gas is analyzed by gas chromatography-mass spectrometry. The microplastics in the pyrolysis gas are qualitatively identified based on characteristic fragment ions, quantitative ions and auxiliary qualitative ions. The microplastics in the pyrolysis gas are semi-quantitatively identified based on the peak area-mass standard curve of the target microplastic.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: To address the challenge of existing technologies being unable to qualitatively or quantitatively determine the capacity of microplastics loaded with toxic organic matter, this invention provides a qualitative and semi-quantitative detection method for microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies based on thermal pyrolysis-gas chromatography-mass spectrometry.

[0028] The detection method of this invention optimizes the pretreatment technology for microplastics and their loaded organic matter, enabling simultaneous extraction and purification of microplastics and their loaded polycyclic aromatic hydrocarbons (PAHs). It also adjusts the pyrolysis parameters of the pyrolysis instrument, employing a two-step pyrolysis mode. First, the organic matter loaded on the microplastics is thermally desorbed at an intermediate temperature, and the desorbed organic matter is analyzed by gas chromatography-mass spectrometry (GC-MS) with the carrier gas. Then, the microplastics are thermally pyrolyzed at a high temperature, and the pyrolysis gas is also analyzed by GC-MS. This invention uses an adjusted thermal desorption and pyrolysis program and GC-MS conditions to determine various PAHs by selected ion monitoring mode and to determine the mass concentration of various polymer microplastics by characteristic pyrolysis fragments.

[0029] The detection method of this invention has a unified operation process and can simultaneously obtain semi-quantitative results of polycyclic aromatic hydrocarbons and quantitative results of multiple microplastics on the same sample. It has the advantages of wide linear range, low detection limit, good spiked recovery rate and precision, and can be used for the synchronous monitoring and evaluation of organic pollutants and microplastic complex pollution in environmental water bodies such as drinking water sources, rivers and lakes. Attached Figure Description

[0030] Figure 1 The flowchart shows the present invention: a method for simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies based on thermal pyrolysis-gas chromatography-mass spectrometry. Figure 2 Selected ion scanning (SIM) chromatograms of polycyclic aromatic hydrocarbon standards: 1-naphthalene, 2-acenaphthene, 3-acenaphthene, 4-fluorene, 5-phenanthrene, 6-anthracene, 7-fluoranthracene, 8-pyrene, 9-benzo(a)anthracene, 10-chrysene, 11-benzo(b)fluoranthracene, 12-benzo(k)fluoranthracene, 13-benzo(a)pyrene, 14-indeno(1,2,3-c,d)pyrene, 15-dibenzo(a,h)anthracene, 16-benzo(g,h,i)perylene; Figure 3 Extracted ion chromatograms of characteristic pyrolysis products of microplastic standards; Figure 4 The image shows the total ion chromatogram (TIC) of microplastics in an actual water sample and a magnified view of a portion thereof. Figure 5 This is the total ion chromatogram (TIC) of polycyclic aromatic hydrocarbons in an actual water sample and its magnified portion. Detailed Implementation

[0031] 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.

[0032] like Figure 1 As shown, a method for simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies based on pyrolysis-gas chromatography-mass spectrometry includes the following steps: A pyrolysis-gas chromatography-mass spectrometry (PCMS) model was constructed for the qualitative and semi-quantitative analysis of microplastics and their supported polycyclic aromatic hydrocarbons, including: (i) Change the pyrolysis system mode, change the original single-stage pyrolysis mode to a single-stage pyrolysis desorption plus two-stage pyrolysis mode, and set and optimize the desorption and pyrolysis parameters; (ii) Determine the pyrolysis-gas chromatography-mass spectrometry detection conditions and instrument parameter settings; (iii) Identify the corresponding indicator fragments for 16 polycyclic aromatic hydrocarbons and various microplastics; (iv) Fit the concentration of polycyclic aromatic hydrocarbon standard samples with the corresponding indicator fragment chromatographic peak area to obtain peak area-concentration standard curves for various polycyclic aromatic hydrocarbons; fit the mass of various microplastic standard samples with the corresponding indicator fragment chromatographic peak area to obtain peak area-mass standard curves for various microplastics. (2) Collect water samples from the environment to be tested and enrich them with microplastics; (3) Quantitatively transfer microplastic samples for thermal pyrolysis-gas chromatography-mass spectrometry detection; analyze the thermal pyrolysis-gas chromatography-mass spectrometry detection data according to the established detection and analysis model to realize the qualitative and semi-quantitative simultaneous detection and analysis of microplastics and their loaded polycyclic aromatic hydrocarbons in the water body to be tested.

[0033] Using the unified sampling and microplastic enrichment pretreatment process described above, a two-step pyrolysis mode was employed to perform polycyclic aromatic hydrocarbon (PAH) thermal desorption-gas chromatography-mass spectrometry (GC-MS) analysis and microplastic pyrolysis-GC-MS analysis on the same sample. This yielded the mass concentrations of 16 PAHs loaded with microplastics in environmental water bodies, as well as the mass concentrations of various polymer microplastics such as PC, PVC, PS, PMMA, PP, PE, and PET. This enabled qualitative and semi-quantitative analysis of microplastics and their loaded PAHs in environmental water bodies, which can be used for the analysis of complex pollution characteristics and risk assessment of drinking water sources, rivers, and lakes.

[0034] The following examples illustrate the specific application of the method of the present invention in the qualitative and semi-quantitative analysis of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies.

[0035] Example 1 (1) Standard solutions of polycyclic aromatic hydrocarbons and thermal desorption-gas chromatography-mass spectrometry analysis (1-1) Preparation of standard solutions Take a mixed standard stock solution of polycyclic aromatic hydrocarbons (PAHs) and use acetonitrile as solvent to prepare standard working solutions with mass concentrations of 10.0 μg / L (concentration of each PAH is 10.0 μg / L), 25.0 μg / L (concentration of each PAH is 25.0 μg / L), 50.0 μg / L (concentration of each PAH is 50.0 μg / L), 100 μg / L (concentration of each PAH is 100 μg / L), 250 μg / L (concentration of each PAH is 250 μg / L), and 500 μg / L (concentration of each PAH is 500 μg / L). These solutions are used to establish standard curves for 16 PAHs.

[0036] The 16 polycyclic aromatic hydrocarbons include naphthalene, acenaphthene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, indo(1,2,3-c,d)pyrene, dibenzo(a,h)anthene, and benzo(g,h,i)perylene.

[0037] (1-2) Setting up the thermal desorption-GC-MS analyzer A CDS Pyroprobe 6150 pyrolysis instrument was used in conjunction with a Shimadzu GC-MS TQ8050 gas chromatograph-triple quadrupole mass spectrometer. The chromatographic column was a DB-5ms (30m × 0.25mm I.D. × 0.25μm).

[0038] The thermal desorption conditions are as follows: nitrogen is used as the carrier gas, the furnace temperature is raised from 80℃ to 350℃ at a rate of 150℃ / min, and the temperature is held at 350℃ for 10min; the interface temperature is 290℃, and the transmission line temperature is 290℃.

[0039] The gas chromatography conditions were as follows: injection port temperature 290℃; column temperature program: initial temperature 60℃ for 1 min, increased to 280℃ at 10℃ / min, then increased to 310℃ at 8℃ / min and held for 9 min; injection mode was splitless, with a split ratio of 10:1 after 0.75 min (in split injection mode, the ratio of the carrier gas flow rate vented from the injection port to the carrier gas flow rate entering the column is 10:1); the carrier gas was helium, with a flow rate of 1.0 mL / min.

[0040] The mass spectrometry conditions were as follows: transfer line temperature 280℃, ion source temperature 300℃, electron impact ionization (EI) mode with electron energy 70eV, Q3 selected ion monitoring (SIM) mode for data acquisition, and solvent delay time set to approximately 6 minutes.

[0041] (1-3) Establishment of the standard curve Mass spectra of standard solutions at different concentrations were obtained by analysis under the instrument reference conditions. Selected ion scanning (SIM) chromatograms of polycyclic aromatic hydrocarbons are shown below. Figure 2 A standard series of at least five concentration points (excluding the zero concentration point) covering the sample concentration range can also be formulated according to the instrument's sensitivity or linear range.

[0042] The qualitative and quantitative ions of 16 polycyclic aromatic hydrocarbons are shown in Table 1.

[0043] Table 1 Compound Name Quantitative Ion (m / z) Auxiliary Qualitative Ion (m / z) Retention Time (min) Naphthalene 128 129,127 8.995 Acenaphthylene 152 151,153 12.967 Acenaphthene 154 153,152 13.420 Fluorene 166 165,167 14.752 Phenanthrene 178 179,176 17.220 Anthracene 178 179,176 17.355 Fluoranthene 202 101,203 20.295 Pyrene 202 101,203 20.869 Benzo(a)anthracene 228 114,226,229 23.973 Chrysene 228 114,226,229 24.067 Benzo(b)fluoranthene 252 126,253 26.711 Benzo(k)fluoranthene 252 126,253 26.780 Benzo(a)pyrene 252 126,253 27.541 Indeno(1,2,3-c,d)pyrene 276 138,277 30.898 Dibenzo(a,h)anthracene 278 139,279 30.990 Benzo(g,h,i)perylene 276 138,277 31.834

[0044] Sixteen polycyclic aromatic hydrocarbons were qualitatively identified using preset quantitative and auxiliary qualitative ions, and their retention times were used for confirmation.

[0045] For each polycyclic aromatic hydrocarbon (PAH), a standard curve was established with the quantitative ion peak area of ​​each PAH as the ordinate and the PAH concentration as the abscissa, as shown in Table 2.

[0046] Table 2 Compound Name Linear Range Linear Equation <![CDATA[Linear (R 2 )]]> RSD (%) Naphthalene 10 - 500 ug / L y = 73.355065 * x - 404.164356 0.999 5.46~16.03 Acenaphthylene 10 - 500 ug / L y = 73.738880 * x + 1800.607904 0.997 4.34~17.29 Acenaphthene 10 - 500 ug / L y = 58.471087 * x - 187.994341 0.999 8.91~16.10 Fluorene 10 - 500 ug / L y = 56.749194 * x - 209.027200 0.999 5.00~12.56 Phenanthrene 10 - 500 ug / L y = 111.767628 * x - 474.260915 0.999 3.54~14.75 Anthracene 10 - 500 ug / L y = 96.782813 * x - 1658.280078 0.999 1.35~16.70 Fluoranthene 10 - 500 ug / L y = 112.981105 * x - 1029.249944 0.999 4.43~13.77 Pyrene 10 - 500 ug / L y = 112.018658 * x - 994.157470 0.997 3.96~11.45 Benzo(a)anthracene 10 - 500 ug / L y = 180.508055 * x - 1823.755179 0.999 5.59~18.57 Chrysene 10-500ug / L y = 194.540924 * x - 2242.793913 0.999 5.73~15.47 Benzo(b)fluoranthene 10-500ug / L y = 89.674288 * x - 842.743166 0.997 6.78~13.41 Benzo(k)fluoranthene 10-500ug / L y = 97.548427 * x + 1534.870084 0.999 5.36~11.14 Benzo(a)pyrene 10-500ug / L y = 60.807740 * x + 903.127207 0.998 6.98~17.20 Indeno(1,2,3-c,d)pyrene 10-500ug / L y = 836.145836 * x - 14796.342237 0.998 4.05~16.99 Dibenzo(a,h)anthracene 10-500ug / L y = 422.826236 * x - 4798.453969 0.999 7.05~12.84 Benzo(g,h,i)perylene 10-500ug / L y = 542.820845 * x - 9877.560426 0.996 5.84~12.51

[0047] The above method exhibits a linear correlation coefficient R0 in the range of 10–500 μg / L. 2 The range of concentrations was 0.996–0.999, the limit of detection was 0.64–7.66 ng / L, and the limit of quantitation was 2.56–30.64 ng / L.

[0048] (2) Microplastic standard solution and thermal pyrolysis-GC-MS analysis (2-1) Preparation of microplastic standard solutions and calibration samples Some microplastic polymers are soluble, while a few are insoluble. Some microplastic polymers contain multiple chemical functional groups. Currently, no single solvent has been found that can dissolve all seven target microplastics; therefore, they need to be grouped according to their solubility (as shown in Table 3). The dissolved microplastic aliquots are mixed in a predetermined order in a sample cup, which becomes the recorded "calibration" sample.

[0049] Table 3 Microplastics Solvents used PS dichloromethane PVC Tetrahydrofuran PP Toluene (heated) PET Hexafluoroisopropanol PE Toluene (heated) PC dichloromethane PMMA Tetrahydrofuran

[0050] Weigh 0.01 g each of pure powders of polycarbonate (PC), polyvinyl chloride (PVC), polystyrene (PS), polymethyl methacrylate (PMMA), polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET), and dissolve them separately in their respective solvents to prepare microplastic stock solutions with a mass concentration of 10,000 ppm. Then, dilute the above stock solutions proportionally to prepare standard solutions of different concentrations, such as 1,000 ppm, 100 ppm, and 10 ppm.

[0051] According to the predetermined injection volume, each standard solution is added to the pyrolysis sample cup, so that the injection mass of a single polymer in the sample cup is within the preset linear range, for example: PC 0.1~50μg, PVC 0.1~25μg, PS 0.1~35μg, PMMA 0.1~20μg, PP 0.1~10μg and 10~150μg, PE 1~10μg and 10~130μg, PET 1~10μg and 10~200μg, respectively, to establish standard curves.

[0052] (2-2) Instrument conditions for pyrolysis-gas chromatography-mass spectrometry The same CDS Pyroprobe 6150 pyrolysis instrument as in Example 1 was used in conjunction with a Shimadzu GC-MS TQ8050 instrument, with a DB-5ms column.

[0053] The pyrolysis sample cup containing the standard polymer sample was placed into the pyrolysis apparatus. Nitrogen was used as the carrier gas, and the pyrolysis was carried out at 700℃ for 40s. The interface temperature was 300℃, the transmission line temperature was 320℃, and the valve box temperature was 300℃.

[0054] The gas chromatography conditions were as follows: injection port temperature 320℃, column temperature program 40℃ for 1 min, ramping up to 150℃ at 20℃ / min and holding for 1 min, ramping up to 300℃ at 10℃ / min and holding for 8 min, and finally ramping up to 320℃ at 10℃ / min and holding for 15 min; split ratio 50:1, carrier gas helium, flow rate 1.0 mL / min.

[0055] The mass spectrometry conditions were: transfer line temperature 320℃, ion source temperature 280℃, electron bombardment ionization, electron energy 70eV, Q3 full scan mode, and scan range 40~1000m / z.

[0056] (2-3) Establishment of the standard curve for microplastics Under the above conditions, microplastic standard samples were analyzed, and characteristic pyrolysis products and characteristic ions of the corresponding microplastic polymers were extracted, such as... Figure 3 As shown in Table 4.

[0057] Table 4 Microplastics Characteristic fragment ions Quantitative ion analysis (m / z) Auxiliary qualitative ions (m / z) Retention time (min) PC Bisphenol A 213 119,228 17.708 PVC Naphthalene 128 102 7.308 PS 1,3,5-Triphenylcyclohexane 91 117,207 20.030 PMMA Methyl methacrylate 69 99,100 3.069 PP 2,4-Dimethyl-1-heptene 55 43,70 4.194 PE 1-Decene 71 57,85 26.417 PET Vinyl benzoate 105 77,51 6.752

[0058] The seven microplastics were qualitatively analyzed using preset quantitative and auxiliary qualitative ions, and their retention times were used for confirmation.

[0059] For each type of microplastic, standard curves were established with the quantitative ion peak area of ​​each characteristic pyrolysis product as the ordinate and the microplastic mass as the abscissa, as shown in Table 5.

[0060] Table 5 Microplastics Characteristic fragment ions Linear range Linear equations <![CDATA[Linear (R 2 )]]> RSD (%) PC Bisphenol A 0.1-50ug y=132615x-35592 0.99 2.1-18.2 PVC Naphthalene 0.1-25ug y=1139x+1104 0.99 3.6-16.7 PS 1,3,5-Triphenylcyclohexane 0.1-35ug y=166047x-57085 0.99 8.19-15.7 PMMA Methyl methacrylate 0.1-20ug y=65462x-22968 0.99 7.75-12.6 PP 2,4-Dimethyl-1-heptene 0.1-10ug y = 10366x + 1169 0.99 5.2-14.0 PP 2,4 - Dimethyl - 1 - heptene 10 - 150 ug y = 6180x + 14917 0.99 7.59-12.6 PE 1 - Decene 1 - 10 ug y = 9982x + 1769 0.99 3.8-17.2 PE 1 - Decene 10 - 130 ug y = 9465x + 38716 0.99 8.38-11.9 PET Vinyl benzoate 1 - 10 ug y = 1354x - 774 0.98 5.9-17.8 PET Vinyl benzoate 10 - 200 ug y = 2535x - 14574 0.99 2.9-15.3

[0061] The results showed that PC, PVC, PS, and PMMA exhibited good linearity within the ranges of 0.1–20 μg or 0.1–50 μg, while PP, PE, and PET showed good linearity within their respective mass ranges. The linear correlation coefficients R0 were all within the ranges. 2 The range is 0.98–0.99. Based on the signal-to-noise ratio calculation method for low-concentration standard samples, the limit of detection and limit of quantitation for microplastics are 0.05–0.22 μg / L and the limit of quantitation is 0.19–0.86 μg / L.

[0062] (3) Water sample collection and pretreatment At multiple sampling points (S1-S7) in the water body to be tested, surface water samples were collected at a depth of approximately 0.5 m below the water surface using stainless steel water samplers. The samples were then placed in pre-cleaned borosilicate glass bottles, with three parallel samples taken from each sampling point. The collected water samples were stored at low temperature and protected from light at 4–8°C and sent to the laboratory for analysis as soon as possible.

[0063] A certain volume of water sample was taken from each sampling point and sequentially filtered through 1000μm, 50μm, and 1μm stainless steel filter membranes. Particulate matter and microplastics trapped on the filter membranes were collected. The filter membranes were placed in clean glass petri dishes and allowed to air dry in the dark, covered with aluminum foil to reduce external contamination.

[0064] The dried filter membrane was placed in a separatory funnel and density separation was performed using 40 mL of saturated sodium chloride solution. After standing for about 12 hours, the supernatant was taken and vacuum filtered again onto a stainless steel filter membrane. Then it was rinsed with ultrapure water and dried.

[0065] The dried microplastic sample was extracted with methanol by ultrasonic extraction. The microplastics on the filter membrane were transferred to the methanol solution. The resulting microplastic-methanol suspension was gradually transferred to a 10mL brown glass bottle. The evaporation volume was adjusted to 1-2mL. The suspension was then transferred to a pyrolysis tube and dried in a 60℃ oven to ensure that all microplastics were loaded into the pyrolysis tube, thus obtaining the sample to be tested for pyrolysis analysis.

[0066] The test samples were subjected to thermal desorption-gas chromatography-mass spectrometry (GC-MS) analysis to obtain GC-MS data of organic compounds loaded on microplastics. The thermally desorbed microplastics were then subjected to thermal pyrolysis-GC-MS analysis to obtain GC-MS data of the microplastics. Substituting the GC-MS data of the environmental water samples into the corresponding standard curves yielded the mass concentrations of various polycyclic aromatic hydrocarbons (PAHs) (as shown in Table 6) and the masses of various microplastics. Combined with the volume conversion of the pretreated water sample, the mass concentrations of various microplastics in the environmental water were obtained (as shown in Table 7), thus realizing the quantitative detection of microplastics and their loaded PAHs in environmental water using the method of this invention.

[0067] Table 6 Serial number Unit: ng / g S1 S2 S3 S4 S5 S6 S7 1 Naphthalene 14.49 49.80 12.62 5.10 9.76 33.49 29.07 2 Acenaphthylene ND 57.72 15.33 ND ND ND ND 3 Acenaphthene ND ND ND ND 8.06 34.04 32.23 4 Fluorene 16.25 ND ND ND ND ND 26.29 5 Phenanthrene 4.81 ND ND ND ND ND 4.36 6 Anthracene ND ND ND ND ND ND 1.75 7 Fluoranthene 3.67 42.12 11.13 ND ND 20.40 ND 8 Pyrene 4.47 41.51 11.11 ND ND 13.23 ND 9 Benzo(a)anthracene 0.84 47.77 12.20 ND ND 2.68 ND 10 Chrysene ND ND ND 7.96 9.42 ND ND 11 Benzo(b)fluoranthene 0.94 9.42 2.56 ND ND ND ND 12 Benzo(k)fluoranthene ND 91.24 23.72 ND ND ND ND 13 Benzo(a)pyrene ND 84.75 14.11 ND ND ND ND 14 Indeno(1,2,3 - c,d)pyrene ND 38.51 7.19 ND ND ND ND 15 Dibenzo(a,h)anthracene 1.32 18.48 ND ND ND ND ND 16 Benzo(g,h,i)perylene ND ND ND ND ND ND ND

[0068] Table 7 Serial number Unit: ug / L S1 S2 S3 S4 S5 S6 S7 1 PC 29.13 ND ND ND ND 19.19 38.00 2 PVC 1025.16 224.78 907.54 1079.14 484.54 480.90 192.00 3 PS ND 6.06 ND ND ND ND ND 4 PMMA 30.85 ND ND 10.46 14.45 10.98 26.60 5 PP 111.18 ND ND 59.00 56.20 56.96 115.98 6 PE 362.48 57.74 15.21 13.38 53.06 85.89 ND 7 PET 239.09 ND 194.51 286.31 ND 976.62 705.09 8 Total 1797.89 288.58 1117.26 1448.29 608.25 1630.53 1171.71

[0069] Environmental water samples known to be free of or have low microplastic content were taken, and standard solutions of PC, PVC, PS, PMMA, PP, PE, and PET were added at three levels: 5 μg / L, 10 μg / L, and 20 μg / L, respectively. Pretreatment and determination were performed according to the method described in this embodiment. The spiked recoveries and relative standard deviations were calculated based on the results. The spiked recoveries for each polymer ranged from 72.9% to 95.4%, and the intra-day and inter-day relative standard deviations ranged from 2.1% to 14.7%, indicating that the method of this invention has good accuracy and precision and is suitable for the quantitative analysis of multiple microplastics in environmental water bodies.

[0070] 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 simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies, characterized in that, Includes the following steps: (1) Constructing a thermal pyrolysis-gas chromatography-mass spectrometry detection model for the qualitative and semi-quantitative analysis of microplastics and their loaded polycyclic aromatic hydrocarbons, including: (i) Change the pyrolysis system mode, and change the original single-stage pyrolysis mode to a single-stage thermal descaling plus two-stage pyrolysis mode; (ii) Determine the detection conditions and instrument parameter settings for polycyclic aromatic hydrocarbon thermal desorption-gas chromatography-mass spectrometry detection and microplastic thermal decomposition-gas chromatography-mass spectrometry detection; (iii) Identify the indicator fragments corresponding to the target polycyclic aromatic hydrocarbon and the target microplastic; (iv) Establish peak area-concentration standard curves for each target polycyclic aromatic hydrocarbon and peak area-mass standard curves for each target microplastic; (2) Collect water samples from the environment to be tested, and obtain the test samples by separating, flotation and ultrasonic enrichment of microplastics and their loaded polycyclic aromatic hydrocarbons; (3) Quantitatively transfer the sample to be tested and perform thermal desorption-gas chromatography-mass spectrometry detection and thermal pyrolysis-gas chromatography-mass spectrometry detection in sequence; analyze the gas chromatography-mass spectrometry detection data according to the detection model constructed in step (1) to realize the qualitative and semi-quantitative simultaneous detection and analysis of microplastics and their loaded polycyclic aromatic hydrocarbons in the water body to be tested.

2. The method for simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies according to claim 1, characterized in that, The target polycyclic aromatic hydrocarbon is at least one of naphthalene, acenaphthene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, indo(1,2,3-c,d)pyrene, dibenzo(a,h)anthene, and benzo(g,h,i)perylene.

3. The method for simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies according to claim 1 or 2, characterized in that, The detection conditions for thermal desorption-gas chromatography-mass spectrometry (GC-MS) of polycyclic aromatic hydrocarbons are as follows: The thermal desorption conditions are as follows: nitrogen is used as the carrier gas, the furnace temperature is raised from 50~100℃ to 300~450℃ at a rate of 150~250℃ / min, and the furnace temperature is held for 10min after reaching the target furnace temperature; the interface and transmission line temperature is 280~320℃. The desorbed gas was analyzed by a gas chromatograph-mass spectrometer. The gas chromatographic conditions were as follows: injection port temperature 280-320℃; column temperature program: initial temperature 40-80℃, hold for 0.5-3 min, increase to 260-310℃ at 8-12℃ / min, then increase to 280-320℃ at 6-10℃ / min and hold for 7-12 min; splitless injection with a split ratio of 10-15:1; helium as carrier gas at a flow rate of 1.0 mL / min; and mass spectrometry conditions: transfer line temperature 280℃, ion source temperature 300℃, electron impact ionization mode, electron energy 70 eV, Q3 selected ion monitoring mode, and solvent delay time of 5-7 min.

4. The method for simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies according to claim 2, characterized in that, The indicator fragments for the target polycyclic aromatic hydrocarbon include quantitative ions and auxiliary qualitative ions; the quantitative ions and auxiliary qualitative ions are:

5. The method for simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies according to claim 1, characterized in that, The target microplastic is at least one of polycarbonate, polyvinyl chloride, polystyrene, polymethyl methacrylate, polypropylene, polyethylene and polyethylene terephthalate.

6. The method for simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies according to claim 1 or 5, characterized in that, The detection conditions for microplastic pyrolysis-gas chromatography-mass spectrometry are as follows: The thermal decomposition conditions are as follows: nitrogen is used as the carrier gas, and thermal decomposition is carried out at 620~800℃ for 30~70s; the interface temperature is 270~330℃, the transmission line temperature is 310~340℃, and the valve box temperature is 290~330℃. The pyrolysis gas was analyzed by gas chromatography-mass spectrometry (GC-MS). The GC conditions were as follows: injection port temperature 280–340 °C; column temperature program: 36–42 °C for 0.75–1.5 min, ramped up to 140–160 °C at 10–25 °C / min and held for 0.8–1.6 min, ramped up to 270–310 °C at 8–12 °C / min and held for 6–10 min, and finally ramped up to 290–330 °C at 8–12 °C / min and held for 13–18 min; split ratio 20–60:1; carrier gas: helium at a flow rate of 1.0 mL / min. The mass spectrometry conditions were as follows: transfer line temperature 290–340 °C; ion source temperature 260–310 °C; electron impact ionization; electron energy 70 eV; Q3 full scan mode; scan range 40–1000 m / z.

7. The method for simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies according to claim 5, characterized in that, The indicator fragments of the target microplastics include characteristic fragment ions, quantitative ions, and auxiliary qualitative ions; Characteristic fragment ions, quantitative ions, and auxiliary qualitative ions are:

8. The method for simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies according to claim 1, characterized in that, Step (iv) includes: (iv-1) Prepare multiple standard solutions of various target polycyclic aromatic hydrocarbons with concentration gradients, and perform thermal desorption-gas chromatography-mass spectrometry detection and analysis. Perform qualitative and quantitative analysis according to the quantitative and qualitative ions of each target polycyclic aromatic hydrocarbon, and establish peak area-concentration standard curves for each target polycyclic aromatic hydrocarbon. (iv-2) Prepare multiple standard solutions with concentration gradients for various types of target microplastics, and perform thermal pyrolysis-gas chromatography-mass spectrometry detection and analysis. Perform qualitative and quantitative analysis according to the characteristic fragment ions, quantitative ions and auxiliary qualitative ions of each target microplastic, and establish the peak area-mass standard curve of each target microplastic.

9. The method for simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies according to claim 1, characterized in that, Step (2) includes: Water samples were collected from the sampling points of the water body to be tested, and the water samples were filtered through a 1-1000μm filter membrane. After drying the filter membrane containing microplastics, density separation was performed using a saturated sodium chloride solution. After standing for 10-20 hours, the supernatant was taken and filtered through the filter membrane again. The filter membrane was rinsed and dried, and the microplastics on the filter membrane were transferred to methanol to obtain a microplastic-methanol suspension. The microplastic-methanol suspension was concentrated and transferred to a pyrolysis tube, then dried to obtain the sample to be tested for thermal desorption or pyrolysis analysis.

10. The method for simultaneous qualitative and semi-quantitative detection of microplastics and their loaded polycyclic aromatic hydrocarbons in environmental water bodies according to claim 1, characterized in that, Step (3) includes: (3-1) The organic matter loaded with microplastics was thermally desorbed at the mid-temperature end of the pyrolysis instrument. The desorbed gas was analyzed by gas chromatography-mass spectrometry. The polycyclic aromatic hydrocarbons in the thermally desorbed gas were qualitatively identified based on quantitative ions and auxiliary qualitative ions. The polycyclic aromatic hydrocarbons in the thermally desorbed gas were quantitatively identified based on the peak area-concentration standard curve of the target polycyclic aromatic hydrocarbons. (3-2) The microplastics after thermal desorption are thermally decomposed at the high-temperature end of the thermal pyrolysis instrument. The pyrolysis gas is analyzed by gas chromatography-mass spectrometry. The microplastics in the pyrolysis gas are qualitatively identified based on characteristic fragment ions, quantitative ions and auxiliary qualitative ions. The microplastics in the pyrolysis gas are semi-quantitatively identified based on the peak area-mass standard curve of the target microplastic.

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