A method for detecting the content of hexachlorodecane in water or sediments

Abstract

The application provides a method for detecting the content of hexachlorodecane in water or sediment, and belongs to the technical field of analytical chemistry. The application obtains a to-be-detected liquid by pretreating a to-be-detected sample; the to-be-detected sample is water or sediment; the to-be-detected liquid is analyzed by using ultra-high performance liquid chromatography-quadrupole / orbitrap high-resolution mass spectrometry to obtain a chromatogram of the to-be-detected liquid; the content of hexachlorodecane in the to-be-detected sample is obtained according to a standard curve of hexachlorodecane and the chromatogram of the to-be-detected liquid; the hexachlorodecane is 1,2,5,6,9,10-hexachlorodecane. The application is aimed at detecting the content of hexachlorodecane in water and sediment, combines the high-efficiency separation capacity of ultra-high performance liquid chromatography and the accurate quantitative capacity of high-resolution mass spectrometry, and can realize rapid and accurate quantitative detection of hexachlorodecane.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry, and in particular to a method for detecting the content of hexachlorodecane in water or sediment. Background Technology

[0002] Hexachlorodecane is a chloroalkane compound widely used in lubricants, flame retardants, rubber, and leather industries due to its thermal stability, flame retardancy, and variable adhesion. However, hexachlorodecane exhibits bioaccumulation, biotoxicity, and environmental persistence, meaning it can be released into the atmosphere and adsorbed onto particulate matter during the production, transportation, and use of these products, causing long-distance migration and pollution of water bodies and sediments. Currently, there are no reports on rapid and accurate methods for detecting hexachlorodecane levels in water bodies and sediments. Summary of the Invention

[0003] The purpose of this invention is to provide a method for detecting the content of hexachlorodecane in water or sediment. The method of this invention can quickly and accurately detect the content of hexachlorodecane in water and sediment.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for detecting the content of hexachlorodecane in water or sediment, comprising the following steps:

[0006] The sample to be tested is pretreated to obtain the test solution; the sample to be tested is water or sediment.

[0007] The test solution was analyzed by ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry to obtain the chromatogram of the test solution;

[0008] The content of hexachlorodecane in the sample was obtained based on the standard curve of hexachlorodecane and the chromatogram of the test solution; the hexachlorodecane was 1,2,5,6,9,10-hexachlorodecane; the standard curve of hexachlorodecane was a linear regression equation of the mass concentration of the hexachlorodecane standard solution and the peak area of ​​the hexachlorodecane chromatogram.

[0009] The chromatographic conditions for the ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry analysis include:

[0010] An HSS PFP column with an inner diameter of 2.1 mm and a length of 100 mm was used, and the packing material particle size was 1.8 μm. The mobile phase consisted of acetonitrile and water, and gradient elution was employed. The gradient elution program was as follows: 0–2 min, acetonitrile volume fraction 40%; 2–4 min, acetonitrile volume fraction increased from 40% to 90%; 4–6 min, acetonitrile volume fraction maintained at 90%; 6–7 min, acetonitrile volume fraction decreased from 90% to 40%; 7–8 min, acetonitrile volume fraction maintained at 40%.

[0011] The mass spectrometry conditions for the ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry analysis include:

[0012] An electrospray ionization source was used, with an ion source temperature of 310℃, an ion transmission tube temperature of 320℃, a spray voltage of 2.5kV, a sheath gas flow rate of 35L / min, and an auxiliary gas flow rate of 10L / min. A negative ion full-scan monitoring mode was used, with a scanning range of 250~1200m / z and a resolution of 70000. Tetramethylammonium chloride aqueous solution was added to the mobile phase at 3~6min.

[0013] Preferably, the concentration of the tetramethylammonium chloride aqueous solution is 0.04–0.06 mM, and the flow rate is 20 μL / min.

[0014] Preferably, the flow rate of the mobile phase is 0.4 mL / min; and the column temperature of the HSS PFP column is 40 °C.

[0015] Preferably, the water body includes seawater or freshwater; the sediments include marine sediments, river sediments, or lake sediments.

[0016] Preferably, when the sample to be tested is water, the pretreatment includes sequential solid-phase extraction and elution.

[0017] Preferably, the solid-phase extraction column used is an HLB extraction column, and the eluent used for elution is acetonitrile; the elution process further includes: removing the solvent from the eluent obtained after elution, mixing the obtained residue with acetonitrile, and filtering to obtain the test solution.

[0018] Preferably, when the sample to be tested is a sediment, the pretreatment includes extraction and purification in sequence.

[0019] Preferably, the extraction is carried out in the presence of active copper powder, C18 and a mixture of hexane and dichloromethane; the mass ratio of the sediment, active copper powder and C18 is 4:0.8-1.2:0.8-1.2, based on dry weight; and the extraction is ultrasonic extraction.

[0020] Preferably, the purification is adsorption column purification, and the adsorption column used for the adsorption column purification is a Florisil column.

[0021] Preferably, the purification process further includes: removing the solvent from the purified solution, mixing the resulting residue with acetonitrile and N-propylethylenediamine solid-phase adsorbent, performing vortexing, sonication and centrifugation sequentially, collecting the supernatant and filtering it to obtain the test solution.

[0022] Beneficial Effects: This invention provides a method for detecting hexachlorodecane content in water or sediment, comprising the following steps: pretreating the sample to be tested to obtain a test solution; the sample to be tested is water or sediment; performing ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry analysis on the test solution to obtain a chromatogram of the test solution; determining the content of hexachlorodecane in the sample to be tested based on the standard curve of hexachlorodecane and the chromatogram of the test solution; wherein the hexachlorodecane is 1,2,5,6,9,10-hexachlorodecane. This invention targets the detection of hexachlorodecane content in water and sediment, combining the high efficiency of ultra-high performance liquid chromatography with the precise qualitative and quantitative capabilities of high-resolution mass spectrometry, enabling accurate quantitative detection of hexachlorodecane, effectively filling the gap in current methods for detecting hexachlorodecane in water and sediment, and possessing the advantages of short processing time and high recovery rate, making it valuable for studying the hexachlorodecane content in the environment. The results of the examples show that, using the method of the present invention to detect hexachlorodecane in seawater and marine sediments, the limit of detection (LOD) for hexachlorodecane in seawater is 10 ng / L and the limit of quantitation (LOQ) is 30 ng / L; the LOD for hexachlorodecane in marine sediments is 5 ng / g and the LOQ is 15 ng / g. When measured in parallel three times under the same method and conditions, the recoveries for seawater ranged from 61.0% to 89.4%, with RSDs of 5.30% to 11.6%, and the recoveries for marine sediments ranged from 64.3% to 88.4%, with RSDs of 10.7% to 12.7%. This indicates that the method of the present invention has good accuracy and reproducibility for detecting hexachlorodecane. Attached Figure Description

[0023] Figure 1 The graphs show the qualitative and quantitative analysis of a 500 μg / L hexachlorodecane standard solution.

[0024] Figure 2 The standard curve for hexachlorodecane;

[0025] Figure 3 The chromatogram of a 150 μg / L hexachlorodecane standard solution in the control group of Test Example 1;

[0026] Figure 4The chromatogram is of the 150 μg / L hexachlorodecane standard solution in the experimental group of Test Example 1. Detailed Implementation

[0027] This invention provides a method for detecting the content of hexachlorodecane in water or sediment, comprising the following steps:

[0028] The sample to be tested is pretreated to obtain the test solution; the sample to be tested is water or sediment.

[0029] The test solution was analyzed by ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry to obtain the chromatogram of the test solution;

[0030] The content of hexachlorodecane in the test sample was obtained based on the standard curve of hexachlorodecane and the chromatogram of the test solution; the hexachlorodecane is 1,2,5,6,9,10-hexachlorodecane.

[0031] The chromatographic conditions for the ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry analysis include:

[0032] An HSS PFP column with an inner diameter of 2.1 mm and a length of 100 mm was used, and the packing material particle size was 1.8 μm. The mobile phase consisted of acetonitrile and water, and gradient elution was employed. The gradient elution program was as follows: 0–2 min, acetonitrile volume fraction 40%; 2–4 min, acetonitrile volume fraction increased from 40% to 90%; 4–6 min, acetonitrile volume fraction maintained at 90%; 6–7 min, acetonitrile volume fraction decreased from 90% to 40%; 7–8 min, acetonitrile volume fraction maintained at 40%.

[0033] The mass spectrometry conditions for the ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry analysis include:

[0034] An electrospray ionization source was used, with an ion source temperature of 310℃, an ion transmission tube temperature of 320℃, a spray voltage of 2.5kV, a sheath gas flow rate of 35L / min, and an auxiliary gas flow rate of 10L / min. A negative ion full-scan monitoring mode was used, with a scanning range of 250~1200m / z and a resolution of 70000. Tetramethylammonium chloride aqueous solution was added to the mobile phase at 3~6min.

[0035] The method of this invention enables accurate detection of hexachlorodecane content in water or sediments based on ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry. Specifically, the hexachlorodecane mentioned in this invention is 1,2,5,6,9,10-hexachlorodecane, CAS number 189350-94-5. The method of this invention is described in detail below.

[0036] In this invention, unless otherwise specified, all raw materials used are commercially available products well known to those skilled in the art or prepared using methods well known to those skilled in the art.

[0037] This invention pretreats the sample to be tested to obtain the test solution. The sample to be tested in this invention is water or sediment; the water may include seawater or freshwater, with seawater being used as an example in the embodiments; the sediment may include marine sediment, river sediment, or lake sediment, with marine sediment being used as an example in the embodiments. In the embodiments of this invention, seawater is collected according to the "Marine Monitoring Standard" (GB 17378.3), then stored in a brown glass bottle at 4°C and transported to the laboratory in the dark; marine sediment is collected according to the "Marine Monitoring Standard" (GB 17378.3), then stored in tin foil, frozen at -20°C, and transported to the laboratory in the dark; wherein, the brown glass bottle is pre-washed three times with methanol and pure water respectively, and dried for later use; the tin foil is pre-ignited at 550°C for 5 hours for later use; if the sample to be tested cannot be measured in time after being transported to the laboratory, the sample to be tested should be stored in the dark at -20°C. This invention selects the pretreatment method according to the type of sample to be tested, which is described in detail below.

[0038] In one embodiment of the present invention, when the sample to be tested is water, the pretreatment includes sequential solid-phase extraction and elution. In another embodiment, preferably, the water is filtered and then mixed with an ammonia-methanol solution, and the resulting mixed solution is sequentially subjected to solid-phase extraction and elution to obtain an eluent. In another embodiment, the filter membrane used for filtration can be a glass fiber filter membrane with a pore size of 0.45 μm; the pH value of the ammonia-methanol solution can be 10.0, and the ammonia-methanol solution can be obtained by mixing methanol and ammonia at a volume ratio of 100:0.1, with the concentration of ammonia ensuring that the pH value of the ammonia-methanol solution meets the above requirements; the volume ratio of the filtered water to the ammonia-methanol solution can be 500:15 to 25, specifically 500:20.

[0039] In one embodiment of the present invention, the extraction column used for solid-phase extraction can be an HLB extraction column. Specifically, the packing material in the HLB extraction column used in this embodiment is polystyrene-divinylbenzene, the mass of the packing material is 60 mg, and the size of the HLB extraction column is 3 mL. The flow rate of the mixed solution during solid-phase extraction can be 2-3 mL / min, specifically 2.5 mL / min. The ammonia-methanol solution used in this invention can improve the permeability of water through the solid-phase extraction column. In another embodiment of the present invention, the eluent used for elution can be acetonitrile. The volume ratio of the filtered water to the eluent can be 500:5-7, specifically 500:6. In this embodiment, a fully automated solid-phase extraction instrument is used for solid-phase extraction, and borosilicate glass centrifuge tubes are used as receiving bottles to collect the eluent.

[0040] As one embodiment of the present invention, the elution process preferably further includes: removing the solvent from the eluent obtained after elution, mixing the obtained residue with acetonitrile, and filtering to obtain the test solution; preferably, the eluent is dried with nitrogen to remove the solvent, the temperature of the nitrogen drying can be 40-43°C, and the liquid surface should be flat with minimal fluctuations during nitrogen drying; the amount of acetonitrile used should be sufficient to meet the actual detection requirements, for example, 1 mL; the filter membrane used for filtration can be a polyvinylidene fluoride (PVDF) filter membrane, and the pore size of the PVDF filter membrane can be 0.22 μm.

[0041] In one embodiment of the present invention, when the sample to be tested is sediment, the pretreatment may include sequential extraction and purification. In another embodiment, it is preferable to pick out lumpy impurities (such as biological remains) from the sediment, then sequentially freeze-dry, grind, and sieve, collecting the undersize material as sediment powder, and then sequentially extracting and purifying it. In another embodiment, the freeze-drying time is based on ensuring sufficient drying, for example, 72 hours; the mesh size of the sieve used for sieving can be 80 mesh; and the grinding is sufficient to obtain sediment powder that meets the aforementioned particle size requirements.

[0042] In one embodiment of the present invention, the extraction is preferably carried out in the presence of active copper powder, C18, and a hexane-dichloromethane mixture. The mass ratio of the sediment, active copper powder, and C18, based on dry weight, can be 4:0.8–1.2:0.8–1.2, specifically 4:1:1. The particle size of the active copper powder can be 100 mesh, and the particle size of the C18 can be 40 μm. The present invention removes active sulfur elements from the sediment using the active copper powder and adsorbs lipids, pigments, and other organic matter using the C18. The volume ratio of hexane to dichloromethane in the hexane-dichloromethane mixture can be 1:0.8–1.2, specifically 1:1. The volume ratio of the sediment to the hexane-dichloromethane mixture, based on dry weight, can be 2 g:8–12 mL, specifically 2 g:10 mL. The hexane-dichloromethane mixture is used as an extractant to extract the target compounds from the sediment.

[0043] In one embodiment of the present invention, the sieved sediment powder is mixed with active copper powder, C18, and a hexane-dichloromethane mixture for extraction. The mixing method can be vortex mixing, with a mixing time of 50-70 seconds, specifically 1 minute. The extraction can be ultrasonic extraction, with a extraction time of 25-35 minutes, specifically 30 minutes. The extraction can be performed at room temperature (25°C). In another embodiment, the extracted material is preferably centrifuged, and the supernatant is collected for later use. The remaining material is mixed with the hexane-dichloromethane mixture, and the extraction and centrifugation are performed again according to the aforementioned steps, collecting the supernatant for later use. Specifically, the supernatants obtained after the two centrifugations are combined as the extraction liquid for subsequent purification. Each centrifugation can be performed at 8000 rpm for 10 minutes.

[0044] In one embodiment of the present invention, the purification can be performed using an adsorption column, specifically a Florisil column. The packing material in the Florisil column comprises silica, magnesium oxide, and sodium sulfate, with a mass ratio of 84:15.5:0.5. The mass of the packing material in the Florisil column is specifically 500 mg, the particle size of the packing material is 60-100 mesh, and the size of the Florisil column is 6 mL. In another embodiment of the present invention, the Florisil column is preferably activated before use. The activation reagent is n-hexane, and the amount of n-hexane used is 6 mL. Specifically, the present invention uses an activated Florisil column to purify the extract to obtain a purified solution.

[0045] As one embodiment of the present invention, the purification process preferably further includes: removing the solvent from the purified liquid, mixing the resulting residue with acetonitrile and N-propylethylenediamine solid-phase adsorbent, and sequentially performing vortexing, ultrasonication, and centrifugation, collecting the supernatant and filtering it to obtain the test liquid. As another embodiment of the present invention, the purified liquid is preferably dried with nitrogen to remove the solvent. The nitrogen drying temperature can be 40–45°C, and the liquid surface should be smooth with minimal fluctuations during nitrogen drying. The amount of acetonitrile used should be sufficient to meet the actual detection requirements, for example, 1 mL. The N-propylethylenediamine solid-phase adsorbent (denoted as PSA adsorbent) has a particle size of 50–75 μm. The PSA adsorbent can remove organic acids, pigments, and metal ions. Based on a test sample mass of 2 g, the amount of PSA adsorbent used can be 50 ± 10 mg. In one embodiment of the present invention, the vortexing time can be 20-40s, specifically 30s; the ultrasonication time can be 4-6min, specifically 5min; the centrifugation speed can be 6000rpm, and the time can be 10min; the filter membrane used for filtration can be a PVDF filter membrane, and the pore size of the PVDF filter membrane can be 0.22μm.

[0046] After obtaining the test solution, the present invention performs ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry (UHPLC-QOSMS) on the test solution to obtain a chromatogram of the test solution. In this invention, the chromatographic conditions for the UHPLC-QOSMS analysis include: using an HSS PFP column with an inner diameter of 2.1 mm and a length of 100 mm, and a packing particle size of 1.8 μm; the mobile phase includes acetonitrile and water (specifically, ultrapure water), and gradient elution is used. The gradient elution program is as follows: 0–2 min, acetonitrile volume fraction 40%; 2–4 min, acetonitrile volume fraction increased from 40% to 90%; 4–6 min, acetonitrile volume fraction maintained at 90%; 6–7 min, acetonitrile volume fraction decreased from 90% to 40%; 7–8 min, acetonitrile volume fraction maintained at 40%. In one embodiment of the present invention, the flow rate of the mobile phase can be 0.4 mL / min; the column temperature of the HSS PFP column can be 40 °C. In another embodiment of the present invention, when performing the ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry analysis, the injection volume can be 5 μL.

[0047] In this invention, the mass spectrometry conditions for ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry analysis include: using an electrospray ionization source with an ion source temperature of 310°C, an ion transfer tube temperature of 320°C, a spray voltage of 2.5 kV, a sheath gas flow rate of 35 L / min, and an auxiliary gas flow rate of 10 L / min; employing a negative ion full-scan monitoring mode with a scanning range of 250–1200 m / z and a resolution of 70,000; and adding a tetramethylammonium chloride aqueous solution to the mobile phase at 3–6 min. As one embodiment of this invention, the concentration of the tetramethylammonium chloride aqueous solution can be 0.04–0.06 mM, specifically 0.05 mM; the flow rate can be 20 μL / min. As another embodiment of this invention, preferably, a peristaltic pump is connected before the electrospray ionization source via a three-way valve, and the tetramethylammonium chloride aqueous solution is pumped into the mobile phase by the peristaltic pump. This invention uses a tetramethylammonium chloride aqueous solution to improve the ionization efficiency of hexachlorodecane, thereby improving its response on the instrument. As one embodiment of the present invention, the quantitative and qualitative ions of hexachlorodecane are shown in Table 2 of Example 1, and will not be repeated here. The present invention uses first-stage high-resolution mass spectrometry to determine the parent and daughter ions for quantification and qualitative analysis, achieving accurate qualitative and quantitative detection of hexachlorodecane based on a quadrupole / orbital ion trap high-resolution mass spectrometer.

[0048] After obtaining the chromatogram of the test solution, this invention determines the content of hexachlorodecane in the test sample based on the standard curve of hexachlorodecane and the chromatogram of the test solution. The standard curve of hexachlorodecane is a linear regression equation of the mass concentration of the hexachlorodecane standard solution and the peak area of ​​hexachlorodecane. In one embodiment of this invention, the standard curve of hexachlorodecane is plotted with the peak area of ​​hexachlorodecane on the ordinate and the mass concentration of the hexachlorodecane standard solution on the abscissa. Preferably, this invention performs ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry analysis on the hexachlorodecane standard solution under the aforementioned chromatographic and mass spectrometric conditions to obtain the chromatogram of the hexachlorodecane standard solution. Based on the peak area of ​​hexachlorodecane and the mass concentration of the hexachlorodecane standard solution, the standard curve of hexachlorodecane is obtained. Based on the chromatogram of the test solution, this invention can determine the content of hexachlorodecane in the test solution, and thus the content of hexachlorodecane in the test sample.

[0049] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0050] The main equipment and reagents used in the following embodiments include:

[0051] Ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometer (model UPLC-QExactiveFocus); fully automated solid phase extraction system (model Fotector-08HT); adjustable nitrogen blow-dryer; ultrapure water system; ultrasonic cleaner; freeze dryer centrifuge; vacuum freeze dryer; muffle furnace.

[0052] The standard was hexachlorodecane; chromatographically pure acetonitrile, methanol, n-hexane, and dichloromethane were used; HLB extraction columns (packing material was polystyrene-divinylbenzene, packing material mass was 60 mg, HLB extraction column size was 3 mL), Florisil columns (packing material composition included silica, magnesium oxide, and sodium sulfate, the mass ratio of silica, magnesium oxide, and sodium sulfate was 84:15.5:0.5, packing material mass was 500 mg, packing material particle size was 60-100 mesh, Florisil column size was 6 mL); PSA adsorbent (particle size was 50-75 μm, purchased from Agilent Technologies; analytical grade), activated copper powder (purchased from Thermo Fisher Scientific, particle size was 100 mesh; analytical grade), C18 (purchased from Agilent Technologies, particle size was 40 μm); glass cellulose filter membrane (0.45 μm), polyvinylidene fluoride (PVDF) filter membrane (0.22 μm).

[0053] Example 1

[0054] Step 1, Sample Collection and Preservation:

[0055] Seawater samples were collected according to the "Marine Monitoring Standard" (GB 17378.3) and stored in brown glass bottles at 4℃, transported to the laboratory protected from light. Marine sediment samples were collected according to the same standard, stored in aluminum foil at -20℃, and transported to the laboratory protected from light. Before placing the samples, the brown glass bottles were rinsed three times each with methanol and pure water, and then dried. The aluminum foil was ignited at 550℃ for 5 hours. Once the samples arrived at the laboratory, if they could not be measured immediately, they should be stored at -20℃ protected from light.

[0056] Step 2, Sample Preparation:

[0057] Seawater samples were brought to room temperature (25°C), filtered through a glass fiber membrane (0.45 μm), and then used. Marine sediment samples were brought to room temperature, and blocky impurities (such as biological remains) were removed. The samples were mixed and placed in a vacuum freeze dryer for 72 hours. After that, the samples were ground and sieved (80 mesh), and the sieved material was collected for use.

[0058] Step 3: Extraction of hexachlorodecane from the sample:

[0059] 100 mL of methanol was mixed with 0.1 mL of ammonia to obtain an ammonia-methanol solution (pH = 10.0). 500 mL of filtered seawater was mixed with 20 mL of the ammonia-methanol solution to obtain a mixed solution. An HLB extraction column was used as the extraction column, and the mixed solution was subjected to solid-phase extraction using an automated solid-phase extraction instrument. The flow rate of the mixed solution during solid-phase extraction was 2.5 mL / min. After solid-phase extraction, 6 mL of acetonitrile was used for elution. The eluent was collected in a borosilicate glass centrifuge tube and dried with nitrogen at 40–43 °C using an adjustable nitrogen dryer (the liquid surface should be flat with minimal fluctuations). The residue was redissolved in 1 mL of acetonitrile and filtered through a PVDF membrane (0.22 μm) to obtain the test solution, which was then analyzed.

[0060] Take 2g of sieved marine sediment into a borosilicate glass centrifuge tube, add 0.5g of activated copper powder and 0.5g of C18, then add 10mL of a hexane-dichloromethane mixture (hexane to dichloromethane volume ratio 1:1), vortex for 1min at room temperature, then sonicate for 30min, followed by centrifugation at 8000rpm for 10min, and collect 6mL of supernatant; add 10mL of the hexane-dichloromethane mixture to the remaining sediment, vortex for 1min, then sonicate for 30min, followed by centrifugation at 8000rpm for 10min, and collect 6mL of supernatant; combine the supernatants obtained from the two centrifugations to obtain the extract;

[0061] The Florisil column was activated with 6 mL of n-hexane. The activated Florisil column was used to purify the extract, and all the purified liquid was collected. The purified liquid was dried with nitrogen at 40–45 °C using an adjustable nitrogen dryer (the liquid level should be flat with minimal fluctuations). The residue was redissolved with 1 mL of acetonitrile, and 50 ± 10 mg of PSA adsorbent was added. After vortexing for 30 s, the mixture was sonicated in a water bath for 5 min, followed by centrifugation at 6000 rpm for 10 min. The supernatant was then filtered through a PVDF membrane (0.22 μm) to obtain the test solution, which was then tested.

[0062] Step 4, Ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry conditions:

[0063] Chromatographic conditions: An HSS PFP column (2.1 mm × 100 mm, 1.8 μm) was used at a column temperature of 40 °C; the mobile phase was acetonitrile and ultrapure water at a flow rate of 0.4 mL / min; the injection volume was 5 μL; gradient elution was used, and the gradient elution program is shown in Table 1.

[0064] Table 1 Gradient elution program

[0065] Time (min) Flow rate (mL / min) Acetonitrile volume fraction (%) Ultrapure water volume fraction (%) 0 0.4 40 60 2 0.4 40 60 4 0.4 90 10 6 0.4 90 10 7 0.4 40 60 8 0.4 40 60

[0066] Mass spectrometry conditions: An electrospray ionization (HESI) source was used, with an ion source temperature of 310℃, an ion transmission tube temperature of 320℃, a spray voltage of 2.5kV, a sheath gas flow rate of 35L / min, and an auxiliary gas flow rate of 10L / min. A negative ion full scan monitoring mode was used, with a scanning range of 250–1200 m / z and a resolution of 70,000. A peristaltic pump was connected to the electrospray ionization source via a three-way valve, and a 0.05mM tetramethylammonium chloride aqueous solution was pumped into the mobile phase at a flow rate of 20μL / min over 3–6 min to improve the ionization efficiency of hexachlorodecane and thus enhance its response on the instrument.

[0067] The quantitative and qualitative ions of hexachlorodecane are shown in Table 2.

[0068] Table 2. Quantitative and qualitative ions of hexachlorodecane.

[0069] Chemical formula ion Quantitative ion analysis (m / z) Qualitative ion 1 (m / z) Qualitative ion 2 (m / z) <![CDATA[C 10 H 16 Cl6]]> <![CDATA[[M+Cl] - ]]> 382.90367 384.90072 386.89777

[0070] Figure 1 The images show the qualitative and quantitative analysis of a 500 μg / L hexachlorodecane standard solution. The upper image shows the chromatogram of hexachlorodecane, and the lower image shows the mass spectrum of the actual hexachlorodecane isotope abundance ratio. The results show that the theoretical and actual mass spectra of the hexachlorosilane isotope abundance ratio are consistent, proving the accuracy of the qualitative and quantitative analysis using this method.

[0071] Step 5: Establishing the standard curve:

[0072] Accurately weigh 5 mg of hexachlorodecane and dilute to 100 mL with methanol to prepare a standard solution of 50 μg / mL. Dilute with acetonitrile to concentrations of 5 ng / mL, 10 ng / mL, 20 ng / mL, 50 ng / mL, and 100 ng / mL to obtain a series of standard solutions. Then, following the ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry conditions in step 4, using acetonitrile as the test sample, after the response curve stabilizes, the standard solutions are separated in the liquid chromatograph using an autosampler. After separation, the ions are converted into negative ions by electrospray ionization (ESI), and then analyzed by a quadrupole. The target ions are separated according to the mass-to-nucleus ratio (m / z) to form an ion stream, which is then detected by a signal detector to obtain the chromatogram and mass spectrum of hexachlorodecane. The peak area is obtained by integration algorithm. A standard curve is established with the concentration of the standard as the x-axis and the peak area as the y-axis.

[0073] Figure 2 The standard curve for hexachlorodecane was obtained, and the results showed that the standard curve was: y = 419981x + 113209, r 2 =0.9999.

[0074] Step 6, Precision and Accuracy

[0075] 1. Limit of detection and limit of quantitation

[0076] (1) Sample preparation

[0077] Seawater: NaCl was calcined in a muffle furnace at 550°C for 5 hours, and then ultrapure water was used as the solvent to prepare artificial seawater with a concentration of 30 wt%, which was used as blank seawater.

[0078] Marine sediments: Take the sieved marine sediments from step 2, wrap them in tin foil, and burn them in a muffle furnace at 550°C for 5 hours to obtain blank marine sediments.

[0079] (2) Extraction: The extraction of hexachlorodecane from seawater and marine sediments is the same as in step 3, to obtain the test solution.

[0080] (3) Detection: Same as step 4.

[0081] Ten blank seawater samples and 2g blank marine sediment samples were taken and extracted and analyzed according to the above steps. The lowest detectable concentration of the blank sample was explored by repeatedly adding hexachlorodecane standard to the samples. When the spiked sample concentration was three times that of the blank sample, this spiked concentration was determined as the limit of detection (LOD) for hexachlorodecane in the sample. The results showed that, using the method of this invention, the LOD for seawater was 10 ng / L and the LOD for quantification was 30 ng / L; the LOD for marine sediments was 5 ng / g and the LOD for quantification was 15 ng / g.

[0082] 2. Blank spike test

[0083] Spiked recovery tests were performed on blank samples following the steps described above. Specifically, 500 mL of blank seawater was taken, and 50 μL, 100 μL, and 500 μL of a 10 μg / mL hexachlorodecane standard solution were added, respectively. The samples were analyzed in triplicate according to the extraction and detection procedures described above. The recoveries ranged from 61.0% to 89.4%, with RSDs of 5.30% to 11.6% (as shown in Table 3). In addition, blank marine sediments were weighed, and 50 μL, 100 μL, and 500 μL of a 10 μg / mL hexachlorodecane standard solution were added, respectively. The samples were analyzed in triplicate according to the complete procedure. The recoveries ranged from 64.3% to 88.4%, with RSDs of 10.7% to 12.7% (as shown in Table 4).

[0084] Table 3. Statistical results of spiked recovery rates in seawater.

[0085]

[0086] Table 4. Statistical results of spiked recovery rates in marine sediments.

[0087]

[0088]

[0089] 3. Actual sample testing

[0090] According to steps 1 to 4, the surface seawater and marine sediments in a certain area of ​​Bohai Bay were tested. The results showed that the concentration of hexachlorodecane in the surface seawater was 80.44 ng / L, and the concentration of hexachlorodecane in the marine sediments was 63.79 ng / g (dry weight).

[0091] Test Example 1

[0092] Control group: Take 150 μg / L hexachlorodecane standard solution and follow step 4 in Example 1, except that the step of pumping tetramethylammonium chloride aqueous solution into the mobile phase is omitted.

[0093] Experimental group: Take 150 μg / L hexachlorodecane standard solution and follow step 4 in Example 1.

[0094] Figure 3 The chromatogram of the 150 μg / L hexachlorodecane standard solution (without tetramethylammonium chloride aqueous solution) in the control group of Test Example 1 is shown. The results show that the peak area (MA) is 28278110 and the peak height (MH) is 4035170.

[0095] Figure 4 The chromatogram of the 150 μg / L hexachlorodecane standard solution (with added tetramethylammonium chloride aqueous solution) in the experimental group of Test Example 1 shows that the peak area (MA) is 61541194 and the peak height (MH) is 8184325.

[0096] The above results show that the use of tetramethylammonium chloride aqueous solution in this invention is beneficial to improving the response of hexachlorodecane on the instrument.

[0097] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for detecting the content of hexachlorodecane in water or sediment, comprising the following steps: The sample to be tested is pretreated to obtain the test solution; the sample to be tested is water or sediment. When the sample to be tested is water, the pretreatment includes sequential solid-phase extraction and elution; The solid-phase extraction uses an HLB extraction column, and the elution uses acetonitrile as the eluent. The elution process further includes: removing the solvent from the eluent, mixing the residue with acetonitrile, and filtering to obtain the test solution. When the sample to be tested is a sediment, the pretreatment includes extraction and purification in sequence; the extraction is carried out in the presence of active copper powder, C18 and a mixture of n-hexane and dichloromethane; the mass ratio of the sediment, active copper powder and C18 is 4:0.8~1.2:0.8~1.2 on a dry weight basis; the extraction is ultrasonic extraction; the purification is adsorption column purification, and the adsorption column used for the adsorption column purification is a Florisil column; the purification process further includes: removing the solvent from the purified solution, mixing the resulting residue with acetonitrile and N-propylethylenediamine solid-phase adsorbent, and performing vortexing, ultrasonication and centrifugation in sequence, collecting the supernatant and filtering it to obtain the test solution; The test solution was analyzed by ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry to obtain the chromatogram of the test solution; The content of hexachlorodecane in the sample was obtained based on the standard curve of hexachlorodecane and the chromatogram of the test solution; the hexachlorodecane was 1,2,5,6,9,10-hexachlorodecane; the standard curve of hexachlorodecane was a linear regression equation of the mass concentration of the hexachlorodecane standard solution and the peak area of ​​the hexachlorodecane chromatogram. The chromatographic conditions for the ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry analysis include: An HSS PFP column with an inner diameter of 2.1 mm and a length of 100 mm was used, with a packing particle size of 1.8 μm. The mobile phase consisted of acetonitrile and water, and gradient elution was employed. The gradient elution program was as follows: 0–2 min, acetonitrile volume fraction 40%; 2–4 min, acetonitrile volume fraction increased from 40% to 90%; 4–6 min, acetonitrile volume fraction maintained at 90%; 6–7 min, acetonitrile volume fraction decreased from 90% to 40%; 7–8 min, acetonitrile volume fraction maintained at 40%. The mass spectrometry conditions for the ultra-high performance liquid chromatography-quadrupole / orbital ion trap high-resolution mass spectrometry analysis include: An electrospray ionization source was used, with an ion source temperature of 310℃, an ion transmission tube temperature of 320℃, a spray voltage of 2.5kV, a sheath gas flow rate of 35L / min, and an auxiliary gas flow rate of 10L / min. A negative ion full-scan monitoring mode was used, with a scanning range of 250~1200m / z and a resolution of 70000. Tetramethylammonium chloride aqueous solution was added to the mobile phase at 3~6 min.

2. The method according to claim 1, characterized in that, The concentration of the tetramethylammonium chloride aqueous solution is 0.04~0.06mM, and the flow rate is 20μL / min.

3. The method according to claim 1, characterized in that, The flow rate of the mobile phase is 0.4 mL / min; the column temperature of the HSSPFP column is 40 °C.

4. The method according to claim 1, characterized in that, The water body includes seawater or freshwater; the sediments include marine sediments, river sediments, or lake sediments.

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