Detection method and detection kit for persistent organic pollutants in marine sediments

Abstract

The invention discloses a method for detecting persistent organic pollutants in marine sediments, and belongs to the technical field of marine pollutant detection methods. The method comprises the following steps: mixing a pretreated sediment sample with anhydrous sodium sulfate, soaking with an n-hexane-acetone mixed solvent and concentrated hydrochloric acid, then carrying out ultrasonic extraction, carrying out liquid-liquid distribution on an extracting solution to obtain an organic phase, concentrating the organic phase, dissolving the organic phase in methanol to obtain a methanol extracting solution, and carrying out solid-liquid separation on the methanol extracting solution; and loading the sample to an activated high-crosslinking polymethacrylate-styrene solid-phase extraction column, sequentially carrying out sectional elution by using ethyl acetate, dichloromethane and methanol, concentrating the eluent, fixing the volume, purifying, and carrying out chromatographic analysis. By optimizing an extraction system and adopting a high-selectivity solid-phase extraction material and a segmented elution procedure, the technical problem that polar and non-polar components are difficult to synchronously and efficiently extract and purify is solved. The method is stable in recovery rate, and is suitable for synchronous and accurate determination of trace persistent organic pollutants in a complex marine sediment matrix.

Description

Technical Field

[0001] This invention belongs to the technical field of marine pollutant detection methods, specifically relating to a method and reagent kit for detecting persistent organic pollutants in marine sediments. Background Technology

[0002] Organochlorine pesticides pentachlorophenol, heptachlorophenate, and dieldrin, along with the industrial chemical polychlorinated biphenyls (PCBs), are all listed as controlled persistent organic pollutants (POPs). They exhibit high stability, bioaccumulation, and carcinogenic, teratogenic, and mutagenic toxicity. Due to their strong adsorption properties, they readily accumulate in marine sediments, making marine sediments a key reservoir for POPs and a long-term, latent source of marine ecological risk, thus becoming a focal point of current marine environmental protection. Current standard methods for determining POPs in marine sediments only specify methods for non-polar organochlorine pesticides and PCBs. Polar pentachlorophenol is not specified for determination in current standards.

[0003] Pretreatment methods for POPs in marine sediments generally include Soxhlet extraction, rapid solvent extraction, ultrasonic extraction, and microwave extraction. Traditional Soxhlet extraction is time-consuming (reflux for 16 hours); rapid solvent extraction and microwave extraction are faster, but the equipment investment is higher; ultrasonic extraction, as a simple, convenient, rapid, and effective pretreatment method, has been widely used for the pretreatment of organic matter in soil and sediments. Marine sediment matrices are complex and contain many interfering substances, requiring purification of the extract before analysis.

[0004] The purification of extracts typically employs concentrated sulfuric acid washing, magnesium silicate or silica-alumina solid-phase extraction, and gel permeation chromatography. Acid washing generates large amounts of acidic waste liquid, is cumbersome, poses environmental and operational safety hazards, and may damage target compounds such as dieldrin. Magnesium silicate or silica-alumina solid-phase extraction is effective in purifying non-polar heptachlorophenate, dieldrin, and polychlorinated biphenyls (PCBs), but polar pentachlorophenol is firmly adsorbed onto the magnesium silicate or silica-alumina solid-phase extraction column, making quantitative elution difficult even with relatively strong polar solvents. Gel permeation chromatography equipment is expensive and has high operating costs. Therefore, there is a need to develop an integrated pretreatment and detection method that can simultaneously, efficiently, and environmentally friendly extract and purify both polar (e.g., pentachlorophenol) and non-polar (e.g., heptachlorophenate, dieldrin, PCBs) persistent organic pollutants (POPs) in marine sediments. Summary of the Invention

[0005] In view of the above-mentioned prior art, the present invention discloses a method for detecting persistent organic pollutants in marine sediments, so as to solve the technical problem that the existing methods cannot efficiently and simultaneously extract, purify and analyze polar and non-polar components in marine sediments.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for detecting persistent organic pollutants in marine sediments, including pentachlorophenol, heptachlorophenate, dieldrin, and polychlorinated biphenyls (PCBs), is provided. The detection method includes the following steps: S1: The marine sediment powder obtained after drying, grinding and sieving is mixed with anhydrous sodium sulfate, soaked in a hexane-acetone mixed solvent and concentrated hydrochloric acid and then subjected to ultrasonic extraction. The extract is then liquid-liquid partitioned and the organic phase is collected as the extract. S2: Concentrate the extract, then dissolve it in methanol to obtain the methanol phase extract; load the methanol phase extract onto an activated highly cross-linked polymethyl methacrylate-styrene solid phase extraction column, and then elute in fractions with ethyl acetate, dichloromethane and methanol in sequence, and collect the eluent; S3: The concentrated eluent was redissolved in hexane, and copper powder was added. After sonication, the supernatant was collected for gas chromatography analysis.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, in step S1, the drying temperature is 20~30℃, the drying time is 5~7 days, and the sieve mesh size is 80~100 mesh.

[0009] Furthermore, in step S1, the volume ratio of n-hexane to acetone in the n-hexane-acetone mixed solvent is 1:1; the ratio of marine sediment powder, anhydrous sodium sulfate, n-hexane-acetone mixed solvent, and concentrated hydrochloric acid is 10g:10g:60mL:2mL; and the soaking time is 11~13h.

[0010] Furthermore, in step S2, the highly cross-linked polymethyl methacrylate-styrene solid phase extraction column is activated by sequentially rinsing it with methanol and high-purity water at a flow rate of 3 mL / min.

[0011] Further, in step S2, the methanol phase extract is loaded onto the activated highly cross-linked polymethyl methacrylate-styrene solid phase extraction column at a flow rate of 1.0 mL / min.

[0012] Furthermore, in step S2, the volume ratio of ethyl acetate, dichloromethane, and methanol is 3:3:1.5, and each solvent is used for elution for 10 min.

[0013] Furthermore, the ultrasound time in step S3 is 5-6 minutes.

[0014] Furthermore, the chromatographic analysis conditions in step S3 are as follows: Chromatographic column: HP-5 capillary chromatography column; Carrier gas: High-purity nitrogen; Carrier gas flow rate: 0.8 mL / min; Inlet temperature: 280℃; Injection method: split injection, split ratio 5:1; Injection volume: 1.0 µL; Detector temperature: 300℃; Column oven program: Initial temperature 100℃, hold for 1 min, increase to 180℃ at a rate of 30℃ / min, then increase to 280℃ at a rate of 10℃ / min, hold for 5 min.

[0015] The present invention also discloses a kit for detecting persistent organic pollutants in marine sediments, comprising an extraction solvent, a solid-phase extraction column, and an elution solvent; the extraction solvent is composed of n-hexane, acetone, and concentrated hydrochloric acid; the solid-phase extraction column is an activated highly cross-linked polymethyl methacrylate-styrene solid-phase extraction column; and the elution solvent comprises ethyl acetate, dichloromethane, and methanol.

[0016] The beneficial effects of this invention are: 1. This application adds concentrated hydrochloric acid to the hexane-acetone extraction system to create a strongly acidic environment, converting phenolate ions into molecular form and improving the solubility of pentachlorophenol in organic solvents. The highly cross-linked polymethyl methacrylate-styrene solid-phase extraction column, after activation with methanol and high-purity water, is placed in a hydrophilic environment. Methanol, as the solvent for the sample extract, ensures effective adsorption of the target analytes onto the packing material after sample loading. Furthermore, methanol has excellent solubility for both non-polar and polar target analytes. By optimizing the elution sequence, solvent type, and extract flow rate, both polar and non-polar compounds can be purified simultaneously, and complex interfering substances in the sediment can also be effectively removed.

[0017] 2. This invention establishes an analytical method for determining 13 persistent organic pollutants, including pentachlorophenol, heptachlorophenate, dieldrin, and polychlorinated biphenyls (PCBs), in marine sediments using ultrasonic extraction-solid phase extraction-gas chromatography. This method effectively overcomes the cumbersome process of segmented extraction and purification required by traditional methods due to the large polarity differences of the target analytes, significantly shortens the sample pretreatment cycle, improves operational safety and convenience, and exhibits excellent purification efficiency for high-lipid sediments. It features rapid pretreatment, good purification effect, and stable recovery rate, meeting the need for simultaneous detection of trace polar and non-polar persistent organic pollutants in complex environmental matrices such as marine sediments. Attached Figure Description

[0018] Figure 1 The standard chromatograms are for 13 persistent organic pollutants. Detailed Implementation

[0019] 1. Main instruments and equipment Gas chromatograph: GC 2010-Plus, equipped with an electron capture µECD detector, Shimadzu Corporation; Ultrasonic cleaner: SN-QX-32, Shanghai Shangpu Instrument Equipment Co., Ltd.; Fully automated solid phase extraction device: ASPE Ultra, Ruike Group (Xiamen) Co., Ltd.; Highly cross-linked polymethyl methacrylate-styrene solid phase extraction column (Jlanzz PMA): 200mg / 6mL, Shanghai Jinlan Instrument Manufacturing Co., Ltd.

[0020] 2. Reagents and Standards n-Hexane, acetone, dichloromethane, ethyl acetate, methanol (chromatographic grade, Tianjin Concord Technology Co., Ltd.), concentrated hydrochloric acid, anhydrous sodium sulfate, copper powder (analytical grade, Tianjin Kemeio Chemical Reagent Co., Ltd.); high-purity water (purified by the MILLI-Q ultrapure water system).

[0021] The types of chromatographic standards are shown in Table 1, including chromatographic standard solutions (100 μg / mL, Tanmo Quality Inspection Technology Co., Ltd.).

[0022] Table 1

[0023] The above mixed standard solution was diluted to prepare a mixed standard working solution with a concentration of 1.0 μg / mL.

[0024] The specific embodiments of the present invention will be described in detail below with reference to examples.

[0025] Example 1 A method for detecting persistent organic pollutants in marine sediments, comprising the following steps: Sample pretreatment S1: The marine sediment samples were dried at 25℃ for 5 days, then ground in an agate mortar and passed through an 80-100 mesh sieve. The moisture content of the samples was determined according to GB 17378.5-2007. All subsequent weighings were based on dry weight. S2: Accurately weigh 10g of marine sediment powder and mix it with 10g of anhydrous sodium sulfate. Place the mixture in a round filter paper tube treated with n-hexane, put it into a 100mL stoppered colorimetric tube, add 60mL of n-hexane-acetone (1:1, v / v) and 2mL of concentrated hydrochloric acid, and soak for 12h. Then, perform ultrasonic extraction for 20min, let it stand to separate the layers, transfer the supernatant to a pear-shaped separatory funnel pre-filled with 250mL of saturated sodium sulfate solution, add 20mL of acetone and repeat ultrasonic extraction 3 times. Combine the extracts in the separatory funnel, shake for 1min, let it stand to separate the layers, discard the aqueous phase, and collect the n-hexane phase as the extract. S3: The extract was concentrated to near dryness, then dissolved in 20 mL of methanol to obtain the methanol phase extract. A Jlanzz PMA solid-phase extraction column was installed on an automated solid-phase extraction device. The column was activated by sequentially passing 10 mL of methanol and 10 mL of high-purity water through it at a flow rate of 3 mL / min. The methanol phase extract was then loaded onto the solid-phase extraction column at a flow rate of 1.0 mL / min. After loading, the column was purged with nitrogen to remove moisture. Elution was performed sequentially with 3 mL of ethyl acetate, 3 mL of dichloromethane, and 1.5 mL of methanol, each solvent for 10 min. All eluents were collected in a collection bottle, concentrated to near dryness, and then diluted to 1 mL with n-hexane. 1 g of copper powder was added to the diluted solution, and the mixture was sonicated for 5 min. The supernatant was then used for chromatographic analysis. The chromatographic conditions were as follows: Chromatographic column: HP-5 (30m×0.25mm×0.25µm) high-elasticity quartz capillary chromatography column; Carrier gas: High-purity nitrogen; Carrier gas flow rate: 0.8 mL / min; Inlet temperature: 280℃; Injection method: split injection, split ratio 5:1; Injection volume: 1.0 µL; Column oven program: Initial temperature 100℃, hold for 1 min, increase temperature to 180℃ at a rate of 30℃ / min, then increase temperature to 280℃ at a rate of 10℃ / min, hold for 5 min; Detector temperature: 300℃.

[0026] Quantification was performed using the external standard method.

[0027] The test results of 12 marine sediment samples from the sea area of ​​Tianjin Nangang Industrial Zone are shown in Table 2: Table 2

[0028] Note: ND indicates not detected. Example 2 Method performance evaluation A series of mixed standard solutions with concentration gradients of 5.0, 10.0, 20.0, 50.0, 100.0, and 200.0 µg / L were prepared using n-hexane. Analysis was performed under the aforementioned chromatographic conditions, and linear regression was conducted on the peak area (y) of the target analyte against its concentration (x, µg / L). As shown in Table 3, the results indicate that the 13 persistent organic pollutants showed good linearity within the concentration range of 5.0–200 µg / L, i.e., the concentration of the tested sediments was within the range of 0.50–20.0 ng / g, with correlation coefficients (r) all greater than 0.9990.

[0029] Anhydrous sodium sulfate was used as a blank sample. A complete sample pretreatment process was performed, and the results were repeated 11 times to determine the detection limits of each analyte. The results are shown in Table 2. The detection limits of the method for sediment samples were 0.031~0.053 ng / g, which meet the requirements of relevant standards such as GB 17378.5-2007, "Marine Monitoring Specification Part 5: Sediment Analysis", HJ 922-2017 "Determination of Organochlorine Pesticides in Soil and Sediments by Gas Chromatography", and HJ 703-2014 "Determination of Phenolic Compounds in Soil and Sediments by Gas Chromatography".

[0030] Table 3

[0031] Example 3 Mixed standard solutions at two concentration levels (low (1.0 ng / g) and high (5.0 ng / g) were added to marine sediment samples (collected from the Tianjin Nangang Industrial Zone). Six samples were treated in parallel at each level, and the analysis was performed according to the method described in Example 1. The average recovery and relative standard deviation (RSD) of each target analyte were calculated. The results are shown in Table 4. The results show that at the 1.0 ng / g spike level, the average recovery rate was 64.4%–118%; at the 5.0 ng / g spike level, the average recovery rate was 70.5%–87.4%. The RSDs of all determinations were between 2.4% and 9.9%, which meet the requirements for sediment sample determination in GB 17378.5-2007, "Marine Monitoring Specification Part 5: Sediment Analysis", HJ 922-2017 "Determination of Organochlorine Pesticides in Soil and Sediments by Gas Chromatography", and HJ 703-2014 "Determination of Phenolic Compounds in Soil and Sediments by Gas Chromatography". The method meets the accuracy and precision requirements of environmental monitoring and analysis standards (such as GB 17378.5-2007 and HJ 922-2017), proving its stability and reliability.

[0032] Table 4

[0033] Note: ND indicates not detected. While specific embodiments of the present invention have been described in detail, they should not be construed as limiting the scope of protection of the present invention. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims are still within the scope of protection of the present invention.

Claims

1. A method for detecting persistent organic pollutants in marine sediments, characterized in that, The persistent organic pollutants include pentachlorophenol, heptachlorophenate, dieldrin, and polychlorinated biphenyls (PCBs), and the detection method includes the following steps: S1: The marine sediment powder obtained after drying, grinding and sieving is mixed with anhydrous sodium sulfate, soaked in a hexane-acetone mixed solvent and concentrated hydrochloric acid and then subjected to ultrasonic extraction. The extract is then liquid-liquid partitioned and the organic phase is collected as the extract. S2: Concentrate the extract, then dissolve it in methanol to obtain a methanol phase extract; load the methanol phase extract onto an activated highly cross-linked polymethyl methacrylate-styrene solid phase extraction column, and then elute in stages with ethyl acetate, dichloromethane and methanol, and collect the eluent; S3: Concentrate the eluent and dissolve it in hexane, add copper powder, sonicate, and take the supernatant for gas chromatography analysis.

2. The method for detecting persistent organic pollutants in marine sediments according to claim 1, characterized in that, In step S1, the drying temperature is 20~30℃ and the drying time is 5~7 days; the sieve mesh size is 80~100 mesh.

3. The method for detecting persistent organic pollutants in marine sediments according to claim 1, characterized in that, In step S1, the volume ratio of n-hexane to acetone in the n-hexane-acetone mixed solvent is 1:1; the ratio of marine sediment powder, anhydrous sodium sulfate, n-hexane-acetone mixed solvent, and concentrated hydrochloric acid is 10g:10g:60mL:2mL; and the soaking time is 11~13h.

4. The method for detecting persistent organic pollutants in marine sediments according to claim 1, characterized in that, In step S2, the highly cross-linked polymethyl methacrylate-styrene solid phase extraction column is activated by sequentially rinsing it with methanol and high-purity water at a flow rate of 3 mL / min.

5. The method for detecting persistent organic pollutants in marine sediments according to claim 1, characterized in that, The methanol phase extract described in step S2 is loaded onto the activated highly cross-linked polymethyl methacrylate-styrene solid phase extraction column at a flow rate of 1.0 mL / min.

6. The method for detecting persistent organic pollutants in marine sediments according to claim 1, characterized in that, In step S2, the volume ratio of ethyl acetate, dichloromethane, and methanol is 3:3:1.5, and each solvent is used for elution for 10 min.

7. The method for detecting persistent organic pollutants in marine sediments according to claim 1, characterized in that, The ultrasound time in step S3 is 5-6 minutes.

8. The method for detecting persistent organic pollutants in marine sediments according to claim 1, characterized in that, The chromatographic analysis conditions in step S3 are as follows: Chromatographic column: HP-5 capillary chromatography column; Carrier gas: High-purity nitrogen; Carrier gas flow rate: 0.8 mL / min; Inlet temperature: 280℃; Injection method: split injection, split ratio 5:1; Injection volume: 1.0 µL; Detector temperature: 300℃; Column oven program: Initial temperature 100℃, hold for 1 min, increase to 180℃ at a rate of 30℃ / min, then increase to 280℃ at a rate of 10℃ / min, hold for 5 min.

9. A kit for detecting persistent organic pollutants in marine sediments, characterized in that, include: The extraction solvent, solid-phase extraction column, and elution solvent are provided; the extraction solvent consists of n-hexane, acetone, and concentrated hydrochloric acid; the solid-phase extraction column is an activated highly cross-linked polymethyl methacrylate-styrene solid-phase extraction column; and the elution solvent includes ethyl acetate, dichloromethane, and methanol.

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