A method for detecting the persistent organic pollutant dichlorobenzene in soil sediments
By employing the UPLC-APCI-MS/MS detection method, combined with a unique extraction solvent and solid-phase extraction purification process, the accuracy and sensitivity issues of trace dichloronaphthalene detection in complex soil matrices have been resolved, achieving efficient and accurate determination of dichloronaphthalene.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- INTEGRATED TECH SERVICE CENT SANMING ENTRY EXIT INSPECTION & QUARANTINE BUREAU
- Filing Date
- 2026-05-15
- Publication Date
- 2026-06-30
AI Technical Summary
Existing detection methods are difficult to accurately and efficiently determine trace amounts of dichloronaphthalene in complex soil matrices, and are easily affected by interference, lacking high sensitivity and selectivity.
The method employs ultra-high performance liquid chromatography-atmospheric pressure chemical ionization source mass spectrometry (UPLC-APCI-MS/MS), combined with a unique extraction solvent system and solid-phase extraction purification process. By using UPLC separation and atmospheric pressure chemical ionization source (APCI) for multiple reaction monitoring, interference from complex matrices is eliminated, enabling accurate determination of various trace amounts of dichloronaphthalene.
The method achieves highly sensitive detection of trace dichloronaphthalene in soil sediments, with a limit of quantitation as low as 5 μg/kg, stable recovery rate of 70.2%~87.9%, and relative standard deviation of less than 9.1%. It is simple and efficient to operate.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of environmental analytical chemistry and persistent organic pollutant (POPs) detection technology, specifically involving a method for determining the residual amounts of six dichloronaphthalene isomers in soil sediments using ultra-high performance liquid chromatography-atmospheric pressure chemical ionization source mass spectrometry (UPLC-APCI-MS / MS). Background Technology
[0002] Dichloronaphthalene (DCN) is a persistent organic pollutant that is difficult to degrade. It is a moderately to weakly polar compound, primarily existing as an impurity in industrial chemicals. Due to its bioaccumulation and potential toxicity, it poses a threat to the ecological environment. Soil and sediments are the main accumulation sites for this type of hydrophobic organic matter.
[0003] Soil is the source of all life, the material foundation upon which humans depend for survival, playing an irreplaceable role, and is also a non-renewable natural resource. With the rapid development of society in recent years, agricultural soils in many places have suffered varying degrees of pollution and damage, all due to human negligence. Among these, the most critical form of pollution is persistent organic pollutants (POPs).
[0004] Sediments are the core accumulation carriers of dissolved carbon (DCN) in aquatic ecosystems. As the habitat of aquatic organisms, DCN in sediments can be released back into the overlying water through bioturbation, or absorbed by benthic organisms and enter the food chain, forming a "sediment-aquatic organism-human" exposure pathway. Benthic fish, in particular, frequently come into contact with sediments during their growth and are highly susceptible to accumulating DCN through feeding and absorption from their body surface. Therefore, sediment DCN detection is a crucial foundation for assessing environmental risks in aquaculture.
[0005] Traditional detection of dichloronaphthalene often employs gas chromatography (GC) or gas chromatography-mass spectrometry (GC-MS). However, GC requires stringent derivatization steps or high-temperature conditions and is susceptible to interference from complex co-extractants in the matrix. Existing liquid chromatography methods mostly utilize low-sensitivity UV or fluorescence detectors. APCI is a gas-phase ionization technique where the sample is first vaporized, then solvent molecules are ionized via corona discharge, and these ions transfer charge to sample molecules through chemical reactions (such as proton transfer). This process is well-suited for compounds like dichloronaphthalene, which are weakly polar small molecules that do not readily form ions in solution and possess certain volatility and thermal stability. Therefore, there is an urgent need to develop a highly sensitive and selective detection method based on UPLC-APCI-MS / MS to meet the analytical needs of trace dichloronaphthalene in complex soil matrices. Currently, there are no reports on UPLC-APCI-MS / MS detection methods for dichloronaphthalene, a persistent organic pollutant in soil sediments, both domestically and internationally. Furthermore, no relevant standards have been found through novelty searches of ISO, ASTM, GB, SN, and other standards, and no relevant patent reports have been found through patent searches. Therefore, there is an urgent need to develop an accurate and efficient UPLC-APCI-MS / MS quantitative detection technology for dichloronaphthalene, a persistent organic pollutant in soil sediments. Summary of the Invention
[0006] The technical problem to be solved by the present invention is to provide a method for detecting the persistent organic pollutant dichloronaphthalene in soil sediments. This method can effectively eliminate interference from complex matrices and accurately determine six trace dichloronaphthalenes, namely 1,2-dichloronaphthalene, 1,4-dichloronaphthalene, 1,5-dichloronaphthalene, 1,8-dichloronaphthalene, 2,3-dichloronaphthalene and 2,6-dichloronaphthalene. It has the advantages of high sensitivity, strong anti-interference ability, simple operation and high detection accuracy.
[0007] This invention is implemented as follows: A method for detecting dichloronaphthalene, a persistent organic pollutant, in soil sediments, comprising the following steps: Step 1: Sample preparation. Collect soil or sediment samples, freeze-dry, grind and sieve to obtain a uniform sample; Step 2: Extraction and purification. Weigh the sample for extraction. The extract is concentrated, purified, and diluted to a fixed volume to obtain the test solution. Step 3: Instrumental analysis. The test solution is analyzed and detected by ultra-high performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry to obtain the response value of dichloronaphthalene in the test solution. Based on the response value, the corresponding standard working solution is selected for chromatographic analysis. The standard working solution has 6 concentration gradients including zero point, and the response values of dichloronaphthalene in both the standard working solution and the test solution should be within the linear response range of the instrument. A blank control is also set up at the same time. Step 4: Quantitative calculation. Substitute the fractionation ratio obtained from ultra-high performance liquid chromatography-tandem mass spectrometry detection and the peak area of dichloronaphthalene into the following formula to calculate the measured value of dichloronaphthalene in the test solution. ; in: X — Residual dichloronaphthalene content in the sample, μg / kg; A — Peak area of dichloronaphthalene in the test solution; As — Peak area of dichloronaphthalene in the standard working solution; c — Concentration of dichloronaphthalene in the standard working solution, μg / L; V — Final volume of the test solution, mL; m — mass of the sample, in grams; R — the percentage of shares to be distributed.
[0008] Furthermore, the conditions for the ultra-high performance liquid chromatography-tandem mass spectrometry are as follows: A. Ultra-high performance liquid chromatography: Chromatographic column: ACQUITY UPLC® BEH-C18 column, 100 mm × 2.1 mm, 1.7 µm; flow rate: 0.3 mL / min; injection volume: 10 μL; column temperature: 40 ℃; gradient elution program as follows:
[0009] B. Mass spectrometry conditions: Ion source: Atmospheric pressure chemical ionization source (APCI), negative ions; Scanning mode: Multiple reaction monitoring (MRM); Ion source temperature: 400℃; Sprayer current: 4μA; Nebulizing gas, curtain gas, auxiliary heating gas, and collision gas are all high-purity nitrogen; Monitored ion pairs, quantitative ion pairs, declustering voltage, collision gas energy, and collision cell outlet voltage are as follows:
[0010] Note: * indicates quantitative ion pairs.
[0011] Furthermore, the method can simultaneously detect six dichloronaphthalene isomers, including: 1,2-dichloronaphthalene (CAS No.: 2050-69-3), 1,4-dichloronaphthalene (CAS No.: 1825-31-6), 1,5-dichloronaphthalene (CAS No.: 1825-30-5), 1,8-dichloronaphthalene (CAS No.: 2050-74-0), 2,3-dichloronaphthalene (CAS No.: 2050-75-1), and 2,6-dichloronaphthalene (CAS No.: 2065-70-5).
[0012] Furthermore, the specific operations of steps one and two are as follows: (1) Sample preparation: Collect soil or sediment samples, remove stones, plant roots and stems, crush, air dry naturally, freeze dry, grind and pass through a 60-mesh sieve to obtain uniform samples for later use; (2) Sample extraction: Weigh 2.0 g of the sample, add 10 mL of water, adjust the pH to 5.0 with glacial acetic acid, then add 50 mL of extraction solution, vortex for 2 min and soak for 5 min, add 5.0 g of anhydrous sodium sulfate, shake for 10 min, centrifuge at 8000 r / min for 5 min, and take 25 mL of supernatant. (3) Sample purification: Add 2 g of anhydrous sodium sulfate to the solid phase extraction column, and pre-wash with 5 mL of n-hexane and 5 mL of extraction solution in sequence. When the liquid level reaches the sodium sulfate surface, quickly transfer the supernatant into the solid phase extraction column, discard the eluent, and then elute with 10 mL of elution solution. Collect the eluent, blow it dry with nitrogen, dissolve it with 1 mL of 95% methanol aqueous solution, and filter it through a 0.22 µm organic filter membrane to obtain the test solution for later use. The eluent is a mixture of acetone, methanol and dichloromethane in a volume ratio of 1:2:1.
[0013] Furthermore, the extract is a mixture of methanol, toluene, and nonane in a volume ratio of 1:1:8.
[0014] Furthermore, the solid-phase extraction column is packed with 1 g / 6 mL silica gel.
[0015] The present invention has the following advantages: High sensitivity and anti-interference capability: Employing a unique extraction solvent system (methanol-toluene-nonane) and solid-phase extraction purification process, combined with ultra-high performance liquid chromatography separation and atmospheric pressure chemical ionization source (APCI) and multiple reaction monitoring mode, it can effectively eliminate interference from complex matrices and achieve accurate determination of various trace dichloronaphthalenes, with a method quantitation limit as low as 5 μg / kg.
[0016] Accurate quantification: Method validation showed that the recoveries at different spiking levels remained stable between 70.2% and 87.9%, with a relative standard deviation of less than 9.1%, and good linearity, meeting the requirements for accurate quantitative analysis.
[0017] Simple and efficient operation: The pretreatment steps are reasonably designed, easy to operate and standardize in the laboratory, and provide a reliable technical means for environmental monitoring and pollution assessment. Detailed Implementation
[0018] This invention relates to a method for detecting dichloronaphthalene, a persistent organic pollutant, in soil sediments, comprising the following steps: Step 1: Sample preparation: Collect soil or sediment samples, remove stones, plant roots and other debris, crush them, air dry them naturally, freeze dry them, grind them, and pass them through a 60-mesh sieve to obtain a uniform sample for later use. Step 2: Sample extraction: Weigh 2.0 g of the sample, add 10 mL of water, adjust the pH to 5.0 with glacial acetic acid, then add 50 mL of extraction solution, vortex for 2 min, soak for 5 min, add 5.0 g of anhydrous sodium sulfate, shake for 10 min, centrifuge at 8000 r / min for 5 min, and take 25 mL of supernatant. Sample purification: Add 2 g of anhydrous sodium sulfate to the solid-phase extraction column, and pre-wash with 5 mL of n-hexane and 5 mL of extraction buffer sequentially. When the liquid level reaches the sodium sulfate surface, quickly transfer the supernatant into the solid-phase extraction column, discard the eluent, and then elute with 10 mL of elution buffer. Collect the eluent, dry it with nitrogen, dissolve it in 1 mL of 95% methanol aqueous solution, and filter it through a 0.22 µm organic filter membrane to obtain the test solution for later use. The eluent is a mixture of acetone, methanol, and dichloromethane in a volume ratio of 1:2:1; the extraction buffer is a mixture of methanol, toluene, and nonane in a volume ratio of 1:1:8; the packing material of the solid-phase extraction column is 1 g / 6 mL silica gel. Step 3: Instrumental analysis. The test solution is analyzed and detected by ultra-high performance liquid chromatography-atmospheric pressure chemical ionization source mass spectrometry to obtain the response value of dichloronaphthalene in the test solution. Based on the response value, the corresponding standard working solution is selected for chromatographic analysis. The standard working solution has 6 concentration gradients including zero point, and the response values of dichloronaphthalene in both the standard working solution and the test solution should be within the linear response range of the instrument. A blank control is also set up at the same time. The conditions for the ultra-high performance liquid chromatography-tandem mass spectrometry are as follows: A. Ultra-high performance liquid chromatography: Chromatographic column: ACQUITY UPLC® BEH-C18 column, 100 mm × 2.1 mm, 1.7 µm; flow rate: 0.3 mL / min; injection volume: 10 μL; column temperature: 40 ℃; gradient elution program as follows: ; B. Mass spectrometry conditions: Atmospheric pressure chemical ionization source (APCI), negative ions; scanning mode: multiple reaction monitoring (MRM); ion source temperature: 400℃; nebulizer current: 4μA; atomizing gas, curtain gas, auxiliary heating gas, and collision gas are all high-purity nitrogen; monitored ion pairs, quantitative ion pairs, declustering voltage, collision gas energy, and collision cell outlet voltage are as follows:
[0019] Note: * indicates quantitative ion pairs.
[0020] The method can simultaneously detect six dichloronaphthalene isomers, including: 1,2-dichloronaphthalene (CAS No.: 2050-69-3), 1,4-dichloronaphthalene (CAS No.: 1825-31-6), 1,5-dichloronaphthalene (CAS No.: 1825-30-5), 1,8-dichloronaphthalene (CAS No.: 2050-74-0), 2,3-dichloronaphthalene (CAS No.: 2050-75-1), and 2,6-dichloronaphthalene (CAS No.: 2065-70-5).
[0021] Step 4: Quantitative calculation. Substitute the fractionation ratio obtained from ultra-high performance liquid chromatography-tandem mass spectrometry detection and the peak area of dichloronaphthalene into the following formula to calculate the measured value of dichloronaphthalene in the test solution. ; in: X — Residual dichloronaphthalene content in the sample, μg / kg; A — Peak area of dichloronaphthalene in the test solution; As — Peak area of dichloronaphthalene in the standard working solution; c — Concentration of dichloronaphthalene in the standard working solution, μg / L; V — Final volume of the test solution, mL; m — mass of the sample, in grams; R — the percentage of shares to be distributed.
[0022] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0023] Example 1: Sample to be tested—soil sediment 1.1 Sample preparation: Collect soil or sediment samples, remove stones, plant roots and stems, crush, air dry naturally, freeze dry, grind and pass through a 60-mesh sieve to obtain uniform samples. The test is divided into two parts, which are placed in clean containers, sealed and labeled, and stored at -20℃ for later use.
[0024] 1.2 Standard Curve Construction: Blank samples were added to a standard series (2, 5, 10, 20, 50 μg / kg), and then processed according to the methods described in steps one to three above, followed by sequential injection and analysis. A working curve was plotted using the peak area y of the analyte against its mass concentration x (μg / L). The six dichloronaphthalene isomers showed good linearity in the concentration range of 2–50 μg / kg. The linear range, correlation coefficient (r), limit of detection (ILOD, S / N>3), and limit of quantitation (MLOQ, S / N>10) for each analyte are shown in Table 1.
[0025] Table 1. Linear equations, correlation coefficients, limits of detection, and limits of quantitation for six dichloronaphthalene isomers.
[0026] 1.3 Background test: Weigh 2.0 g (accurate to 0.01 g) of the sample obtained in Section 1.1 into each of six 100 mL stoppered centrifuge tubes, and then operate according to the method described in steps one to three above. The actual measured values and average values are shown in Table 2. The average value is the background value.
[0027] Table 2. Background values of dichloronaphthalene in soil sediments.
[0028] 1.4 Verification 1: Adding 5 μg / kg dichloronaphthalene Weigh 2.0 g (accurate to 0.01 g) of the sample obtained in 1.1 into each of six 100 mL stoppered centrifuge tubes. Then add 0.1 mL of 0.1 mg / L dichloronaphthalene standard solution to each centrifuge tube. Then operate according to the method described in steps one to three above. The recovery results are listed in Table 3.
[0029] Table 3 Recovery rates of dichloronaphthalene (5 μg / kg) in soil sediment samples
[0030] 1.4 Verification 2: Addition of 10 μg / kg dichloronaphthalene Weigh 2.0 g (accurate to 0.01 g) of the sample obtained in 1.1 into each of six 100 mL stoppered centrifuge tubes. Then add 0.1 mL of 0.2 mg / L dichloronaphthalene standard solution to each centrifuge tube. Then operate according to the method described in steps one to three above, and list the final calculated recovery results in Table 4.
[0031] Table 4. Recovery rates of dichloronaphthalene with 10 μg / kg added to soil sediment samples
[0032] The experimental results above show that when this invention is applied to detect the content of six dichloronaphthalene isomers in soil sediment samples, the detection limit is 5 μg / kg, the recovery rate is 70.2-87.9%, the standard curve shows good linearity in the range of 2-50 μg / L, and the correlation coefficient r is greater than 0.999.
[0033] The recovery rate and RSD values in the respective verification results indicate that the detection method of the present invention is feasible and highly accurate.
[0034] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and not intended to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered within the scope of protection of the claims of the present invention.
Claims
1. A method for detecting dichloronaphthalene, a persistent organic pollutant, in soil sediments, characterized in that, The ultra-high performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (UHPLC-ATC-MS / MS) technique was employed, including sample preparation, extraction and purification, instrumental analysis, and quantitative calculation steps, as detailed below: Step 1: Sample preparation. Collect soil sediment samples, freeze-dry, grind and sieve to obtain uniform samples; Step 2: Extraction and purification. Weigh the sample for extraction. The extract is concentrated, purified, and diluted to a fixed volume to obtain the test solution. Step 3: Instrumental analysis. The test solution is analyzed and detected by ultra-high performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry to obtain the response value of dichloronaphthalene in the test solution. Based on the response value, the corresponding standard working solution is selected for chromatographic analysis. The standard working solution has 6 concentration gradients including zero point, and the response values of dichloronaphthalene in both the standard working solution and the test solution should be within the linear response range of the instrument. A blank control is also set up at the same time. Step 4: Quantitative calculation. Substitute the fractionation ratio obtained from ultra-high performance liquid chromatography-tandem mass spectrometry detection and the peak area of dichloronaphthalene into the following formula to calculate the measured value of dichloronaphthalene in the test solution. ; in: X — Residual dichloronaphthalene content in the sample, μg / kg; A — Peak area of dichloronaphthalene in the test solution; As — Peak area of dichloronaphthalene in the standard working solution; c — Concentration of dichloronaphthalene in the standard working solution, μg / L; V — Final volume of the test solution, mL; m — mass of the sample, in grams; R — the percentage of shares to be distributed.
2. The method for detecting dichloronaphthalene, a persistent organic pollutant in soil sediments according to claim 1, is characterized in that: The conditions for the ultra-high performance liquid chromatography-tandem mass spectrometry are as follows: A. Ultra-high performance liquid chromatography: Chromatographic column: ACQUITY UPLC® BEH-C18 column, 100 mm × 2.1 mm, 1.7 µm; flow rate: 0.3 mL / min; injection volume: 10 μL; column temperature: 40 ℃; gradient elution program as follows: ； B. Mass spectrometry conditions: Ion source: Atmospheric pressure chemical ionization source (APCI), negative ions; Scanning mode: Multiple reaction monitoring (MRM); Ion source temperature: 400℃; Sprayer current: 4μA; Nebulizing gas, curtain gas, auxiliary heating gas, and collision gas are all high-purity nitrogen; Monitored ion pairs, quantitative ion pairs, declustering voltage, collision gas energy, and collision cell outlet voltage are as follows: 。 3. The method according to claim 1, characterized in that: The method can simultaneously detect six dichloronaphthalene isomers, including: 1,2-dichloronaphthalene, 1,4-dichloronaphthalene, 1,5-dichloronaphthalene, 1,8-dichloronaphthalene, 2,3-dichloronaphthalene, and 2,6-dichloronaphthalene.
4. The method for detecting dichloronaphthalene, a persistent organic pollutant in soil sediments, according to claim 1, is characterized in that: The specific operations for steps one and two are as follows: (1) Sample preparation: Collect soil sediment samples, remove stones, plant roots and stems, crush, air dry naturally, freeze dry, grind and pass through a 60-mesh sieve to obtain uniform samples for later use; (2) Sample extraction: Weigh 2.0 g of the sample, add 10 mL of water, adjust the pH to 5.0 with glacial acetic acid, then add 50 mL of extraction solution, vortex for 2 min and soak for 5 min, add 5.0 g of anhydrous sodium sulfate, shake for 10 min, centrifuge at 8000 r / min for 5 min, and take 25 mL of supernatant. (3) Sample purification: Add 2 g of anhydrous sodium sulfate to the solid phase extraction column, and pre-wash with 5 mL of n-hexane and 5 mL of extraction solution in sequence. When the liquid level reaches the sodium sulfate surface, quickly transfer the supernatant into the solid phase extraction column, discard the eluent, and then elute with 10 mL of elution solution. Collect the eluent, blow it dry with nitrogen, dissolve it with 1 mL of 95% methanol aqueous solution, and filter it through a 0.22 µm organic filter membrane to obtain the test solution for later use. The eluent is a mixture of acetone, methanol and dichloromethane in a volume ratio of 1:2:
1.
5. The method for detecting dichloronaphthalene, a persistent organic pollutant in soil sediments, according to claim 4, is characterized in that: The extract is a mixture of methanol, toluene, and nonane in a volume ratio of 1:1:
8.
6. The method for detecting dichloronaphthalene, a persistent organic pollutant in soil sediments, according to claim 4, is characterized in that: The solid-phase extraction column is packed with 1 g / 6 mL silica gel.