Method for detecting polychlorinated naphthalene in food based on magnetic solid phase extraction-gas chromatography-mass spectrometry
By employing magnetic solid-phase extraction-gas chromatography-mass spectrometry (MS/MS) with tannic acid-modified magnetic adsorbents, the problems of high solvent consumption and poor selectivity in traditional methods have been solved, enabling efficient and accurate detection of polychlorinated naphthalenes in food.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 合肥海关技术中心
- Filing Date
- 2026-03-03
- Publication Date
- 2026-04-21
AI Technical Summary
Existing technologies for detecting polychlorinated naphthalenes (PCNs) in food rely on liquid-liquid extraction, which consumes large amounts of solvent and is cumbersome to operate. Traditional solid-phase extraction has poor selectivity and is difficult to efficiently adsorb trace PCNs from complex matrices, thus limiting its application.
A magnetic solid-phase extraction combined with gas chromatography-mass spectrometry (GC-MS) method was adopted. Tannic acid-modified magnetic adsorbents were used to bind to PCNs molecules through π-π interactions, and virtual template molecules were introduced to enhance selectivity. An external magnet was used to achieve rapid separation. Qualitative and quantitative analysis was performed by combining GC-MS with selected ion monitoring mode.
It enables the detection of polychlorinated naphthalenes that is simple to operate, rapid, highly sensitive, and environmentally friendly, significantly reducing solvent consumption, improving analytical efficiency and accuracy, and is suitable for a variety of food matrices.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of food testing technology, specifically to a method for detecting polychlorinated naphthalenes in food based on magnetic solid phase extraction-gas chromatography-mass spectrometry. Background Technology
[0002] Polychlorinated naphthalenes (PCNs) are a class of persistent organic pollutants with structures similar to dioxins. They have potential toxicity, such as carcinogenicity and teratogenicity, and can enter the food chain through environmental accumulation, posing significant food safety risks. Therefore, it is crucial to establish efficient and accurate detection methods.
[0003] Currently, the pretreatment techniques for detecting PCNs in the aforementioned foods mainly rely on liquid-liquid extraction and solid-phase extraction. Liquid-liquid extraction typically consumes large amounts of organic solvents. Although traditional solid-phase extraction is widely used, its operation steps are cumbersome, and for complex matrices, the purification effect of conventional packing materials is limited. Furthermore, co-extracted impurities such as fats and proteins can easily interfere with subsequent instrumental analysis.
[0004] Magnetic solid-phase extraction (MSPE) is an emerging sample pretreatment technique that uses an external magnet to separate adsorbents and is easy to operate. However, existing magnetic adsorbents generally suffer from poor selectivity and insufficient adsorption capacity, making it difficult to simultaneously and efficiently adsorb trace amounts of PCNs from complex matrices with significant differences, such as grains and their products, meat and their products, aquatic products and their products, and vegetables, thus limiting their practical applications.
[0005] Based on the above, the present invention provides a method for detecting polychlorinated naphthalenes in food based on magnetic solid phase extraction-gas chromatography-mass spectrometry, so as to solve the technical problems mentioned above. Summary of the Invention
[0006] The detection method for polychlorinated naphthalene provided by this invention has the advantages of simple operation, speed, high sensitivity and environmental friendliness. It is suitable for the efficient and accurate detection of polychlorinated naphthalene in a variety of foods such as grains and their products, meat and its products, aquatic products and their products, and vegetables.
[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for detecting polychlorinated naphthalenes in food based on magnetic solid-phase extraction-gas chromatography-mass spectrometry includes the following steps: Step 1: Homogenize the food sample to be tested, then weigh 1.0-5.0g of the food sample to be tested and place it in a centrifuge tube and add 10-30mL of acetonitrile. Vortex mix for 1-3min, then extract by sonication for 10-20min. Then centrifuge at 3-5℃, collect the supernatant, concentrate it to 0.1mL and add 10mL of ultrapure water and mix well to obtain the food sample extract. Step 2: Add 10-50 mg of magnetic adsorbent and 0.5-2 g of sodium chloride to the food sample extract, vortex mix for 1-3 min, and then oscillate at a frequency of 600-800 Hz at room temperature for 10-30 min to adsorb. Step 3: Use an external magnet to separate the magnetic adsorbent that adsorbed the target substance in Step 2 from the solution. Discard the supernatant and wash the magnetic adsorbent with ultrapure water. Discard the washing liquid and elute with a hexane-acetone mixed solvent. After vortexing for 2-3 minutes, collect all the eluent under the action of an external magnet. The volume ratio of hexane to acetone in the hexane-acetone mixed solvent is 8:2. Step 4: Blow the eluent collected in Step 3 to near dryness with nitrogen in a water bath at 40-50℃, then redissolve it with n-hexane, vortex mix it, and transfer the resulting solution to a vial for subsequent analysis. Step 5: Prepare a series of polychlorinated naphthalene standard working solutions and use gas chromatography-mass spectrometry to determine and analyze the solutions obtained in Step 4 and the polychlorinated naphthalene standard working solutions. Select ion monitoring mode for detection, qualitatively identify polychlorinated naphthalene based on retention time and characteristic ions, and quantify using the internal standard method. The internal standard method for quantification includes the following steps: Step 1: Plot a standard curve with the ratio of the peak area of the analyte to the peak area of the internal standard in a series of polychlorinated naphthalene standard solutions as the ordinate and the ratio of the concentration of the analyte to the concentration of the internal standard in the standard solutions as the abscissa. The second step is to calculate the content of the polychlorinated naphthalene using the following formula: ; In the formula, : Indicates the content of polychlorinated naphthalene in the sample, in mg / kg; : Indicates the mass concentration of polychlorinated naphthalene in the sample solution obtained from the standard curve, in ng / mL; : Indicates the final volume of the sample solution, in mL; : Indicates the mass of the sample taken, in grams; : Indicates the dilution factor.
[0008] Furthermore, in step one, the power for ultrasonic extraction is set to 300-500W, and the ultrasonic frequency is set to 35-45kHz.
[0009] Furthermore, in step one, the centrifugal speed is set to 3500-5000 r / min, and the centrifugal time is set to 5-10 min.
[0010] Furthermore, the preparation method of the magnetic adsorbent includes the following steps: Step 1: Synthesis of tannic acid-modified magnetic iron(III) oxide: Nano-iron oxide (Fe3O4) with a mass of 20-40 times that of tannic acid was added to a 0.8-1.2 mol / L aqueous solution of tannic acid. The mixture was stirred at room temperature for 2 hours, magnetically separated, washed three times with water, and dried under vacuum at 60°C to obtain tannic acid-modified magnetic iron oxide. Step 2: Synthesis of RAFT-modified magnetic iron(III) oxide: Tannic acid-modified magnetic iron oxide was dispersed in anhydrous ethanol; 4-cyano-4-[(dodecylthio)carbonyl]thiovalerate and N,N'-dicyclohexylcarbodiimide were added, and the mixture was reacted at room temperature in the dark for 12 h. After magnetic separation and washing with ethanol, RAFT-modified magnetic iron oxide was obtained. The ratio of tannic acid-modified magnetic iron oxide, anhydrous ethanol, 4-cyano-4-[(dodecylthio)carbonyl]thiovalerate and N,N'-dicyclohexylcarbodiimide was 1 g:30 mL:5-20 mg:10-40 mg. Step 3: Synthesize the target magnetic molecular imprinted adsorbent: A virtual template molecule mixture, 4-vinyl-3-fluorophenylboronic acid, and ethylene glycol dimethacrylate were dissolved in ethanol / water (volume ratio 4:1) and shaken at room temperature for 4 h to form a halogen bond / π-π pre-assembled complex. RAFT-modified magnetic iron oxide and azobisisobutyronitrile were added, and the mixture was ultrasonically dispersed for 5 min, followed by nitrogen purging for 10 min. The mixture was then reacted in an oil bath at 60 °C for 12 h with shaking. After magnetic separation, the mixture was washed three times with ethanol and dried under vacuum at 60 °C to obtain the target magnetic molecularly imprinted adsorbent. The ratio of the virtual template molecule mixture, 4-vinyl-3-fluorophenylboronic acid, ethylene glycol dimethacrylate, RAFT-modified magnetic iron oxide, and azobisisobutyronitrile was 1 mmol:4-8 mmol:18-20 mmol:0.1-0.5 g:0.2-0.8 mg. The ratio of 1-bromonaphthalene and 1,4-dibromonaphthalene in the virtual template molecule mixture was 1 mmol:1-4 mmol.
[0011] Furthermore, the series of polychlorinated naphthalene standard working solutions are mixed polychlorinated naphthalene standard working solutions with mass concentrations of 10 μg / L, 20 μg / L, 50 μg / L, 100 μg / L, and 200 μg / L, and the concentration of the internal standard in the mixed polychlorinated naphthalene standard working solution is 50 μg / L.
[0012] Furthermore, the conditions for gas chromatography analysis are as follows: a DB-5MS capillary column is used; the injection method is splitless injection, and the injection volume is 1-3 μL; the carrier gas is helium with a purity of 99.999%, and the flow rate is 1.0 mL / min.
[0013] Furthermore, the following steps are used for programmed temperature rise during gas chromatography analysis: hold the initial temperature of 100℃ for 1-4 min; raise the temperature to 300℃ at 8-14℃ / min and hold for 8-12 min; then raise the temperature to 310℃ at 20℃ / min and hold for 4 min.
[0014] Furthermore, the mass spectrometry detection conditions were as follows: electron impact ionization (EI) was used as the ionization method; the transfer line temperature was 250-280℃; the ion source temperature was 230-250℃; the solvent delay time was 3-5 min; and the ion monitoring mode was selected to detect the target polychlorinated naphthalene homologues.
[0015] Furthermore, the isotopic internal standards used in the internal standard method described in step five are 13C12-labeled 1-chloronaphthalene, 1,5-dichloronaphthalene, 1,2,3-trichloronaphthalene, 1,2,3,4-tetrachloronaphthalene, 1,2,3,5,7-pentachloronaphthalene, 1,2,3,4,6,7-hexachloronaphthalene, 1,2,3,4,5,6,7-heptachloronaphthalene, and octachloronaphthalene.
[0016] Furthermore, the food sample to be tested can be any one of grains and their products, meat and its products, aquatic products and their products, or vegetables.
[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. The magnetic adsorbent prepared in this invention uses tannic acid as a functional monomer. Its abundant benzene ring structure can efficiently bind to PCNs molecules through π-π interactions and hydrophobic interactions. A virtual template molecular template mixture (a complex of 1-bromonaphthalene and 1,4-dibromonaphthalene) is introduced to avoid template residue. The functional monomer 4-vinyl-3-fluorophenylboronic acid is used to improve molecular imprinting selectivity. The magnetic adsorbent exhibits excellent selective adsorption capacity for PCNs and can effectively avoid interference from matrices such as fats and proteins.
[0018] 2. The magnetic solid-phase extraction technology provided by this invention eliminates the need for complex steps such as column packing, centrifugation, and filtration. It achieves complete separation of the adsorbent and solution within seconds using only an external magnet, significantly shortening pretreatment time and improving analytical efficiency. Furthermore, this method significantly reduces the consumption of organic solvents, lowering experimental costs and environmental pollution. Simultaneously, the raw materials for preparing the magnetic adsorbent are readily available and inexpensive. In addition, this invention combines the high selectivity of gas chromatography-mass spectrometry with selected ion monitoring mode, resulting in a method with low detection limits for PCNs, good reproducibility, high recovery rate, and accurate quantification. Detailed Implementation
[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0020] In the following embodiments: Tannic acid-modified magnetic iron(III) oxide is represented by Fe3O4@TA. Magnetic iron(III) oxide modified with RAFT agent is represented as Fe3O4@TA-RAFT. The abbreviation for 4-cyano-4-[(dodecylthio)carbonyl]thiopentanoic acid is CDTPA. The abbreviation for N,N'-dicyclohexylcarbodiimide is DCC. The abbreviation for 4-vinyl-3-fluorophenylboronic acid is 4-VFBA. The virtual template molecular template mixture is a mixture of 1-bromonaphthalene and 1,4-dibromonaphthalene. Ethylene glycol dimethacrylate is abbreviated as EGDMA. The abbreviation for azobisisobutyronitrile is AIBN.
[0021] Example 1 A method for detecting polychlorinated naphthalenes in fish meat based on magnetic solid-phase extraction-gas chromatography-mass spectrometry includes the following steps: Step 1: Homogenize the fish sample to be tested, then weigh 5.0g of the fish sample to be tested and place it in a centrifuge tube and add 10mL of acetonitrile. Vortex mix for 3min and then extract by sonication for 10min. Then centrifuge at 3℃, collect the supernatant, concentrate it to 0.1mL and add 10mL of ultrapure water and mix well to obtain the food sample extract. The ultrasonic extraction power was set to 400W and the ultrasonic frequency was set to 40kHz. The centrifugation speed was set to 3500 r / min, and the centrifugation time was set to 10 min. Step 2: Add 10 mg of magnetic adsorbent and 0.5 g of sodium chloride to the fish meat sample extract, vortex mix for 3 min, and then oscillate at a frequency of 600 Hz at room temperature for 20 min to adsorb. Step 3: Use an external magnet to separate the magnetic adsorbent that adsorbed the target substance in Step 2 from the solution. Discard the supernatant and wash the magnetic adsorbent with ultrapure water. Discard the washing liquid and elute with a hexane-acetone mixed solvent. After vortexing for 2 minutes, collect all the eluent under the action of an external magnet. The volume ratio of hexane to acetone in the hexane-acetone mixed solvent is 8:2. Step 4: Blow the eluent collected in Step 3 to near dryness with nitrogen in a 40°C water bath, then redissolve it with n-hexane, vortex mix it, and transfer the resulting solution to a vial for subsequent analysis. Step 5: Prepare a series of polychlorinated naphthalene standard working solutions and use gas chromatography-mass spectrometry to determine and analyze the solutions obtained in Step 4 and the polychlorinated naphthalene standard working solutions. Select ion monitoring mode for detection, qualitatively identify polychlorinated naphthalene based on retention time and characteristic ions, and quantify using the internal standard method. The series of polychlorinated naphthalene standard working solutions are mixed polychlorinated naphthalene standard working solutions with mass concentrations of 10 μg / L, 20 μg / L, 50 μg / L, 100 μg / L, and 200 μg / L, and the concentration of internal standard in the mixed polychlorinated naphthalene standard working solutions is 50 μg / L; The internal standard method for quantification includes the following steps: Step 1: Plot a standard curve with the ratio of the peak area of the analyte to the peak area of the internal standard in a series of polychlorinated naphthalene standard solutions as the ordinate and the ratio of the concentration of the analyte to the concentration of the internal standard in the standard solutions as the abscissa. The second step is to calculate the content of polychlorinated naphthalene using the following formula: ; In the formula, : Indicates the content of polychlorinated naphthalene in the sample, in mg / kg; : Indicates the mass concentration of polychlorinated naphthalene in the sample solution obtained from the standard curve, in ng / mL; : Indicates the final volume of the sample solution, in mL; : Indicates the mass of the sample taken, in grams; : Indicates the dilution factor.
[0022] The preparation method of magnetic adsorbent includes the following steps: Step 1: Synthesis of tannic acid-modified magnetic iron(III) oxide (Fe3O4@TA): Nano-iron oxide (Fe3O4@TA) with a mass of 20 times that of tannic acid was added to a 0.8 mol / L aqueous solution of tannic acid. The mixture was stirred at room temperature for 2 h, magnetically separated, washed three times with water, and dried under vacuum at 60 °C to obtain tannic acid-modified magnetic iron oxide (Fe3O4@TA). Step 2: Synthesis of RAFT-modified magnetic iron(III) oxide (Fe3O4@TA-RAFT): Fe3O4@TA was dispersed in anhydrous ethanol, and 4-cyano-4-[(dodecylthio)carbonyl]thiopentanoic acid (CDTPA) and N,N'-dicyclohexylcarbodiimide (DCC) were added. The mixture was reacted at room temperature in the dark for 12 h, followed by magnetic separation and washing with ethanol to obtain Fe3O4@TA-RAFT. The ratio of Fe3O4@TA, anhydrous ethanol, CDTPA, and DCC was 1 g:30 mL:10 mg:16 mg. Step 3: Synthesize the target magnetic molecular imprinted adsorbent: A virtual template molecular template mixture, 4-vinyl-3-fluorophenylboronic acid (4-VFBA), and ethylene glycol dimethacrylate (EGDMA) were dissolved in ethanol / water (volume ratio 4:1) and shaken at room temperature for 4 h to form a halogen bond / π-π pre-assembled complex. Fe3O4@TA-RAFT and azobisisobutyronitrile (AIBN) were added, and the mixture was ultrasonically dispersed for 5 min and purged with nitrogen for 10 min. The mixture was then reacted in an oil bath at 60 °C for 12 h with shaking. After magnetic separation, the mixture was washed three times with ethanol and dried under vacuum at 60 °C to obtain the target magnetic molecularly imprinted adsorbent. The ratio of the virtual template molecular template mixture, 4-vinyl-3-fluorophenylboronic acid (4-VFBA), ethylene glycol dimethacrylate (EGDMA), Fe3O4@TA-RAFT, and azobisisobutyronitrile was 1 mmol:4 mmol:20 mmol:0.1:0.2 mg. The ratio of 1-bromonaphthalene and 1,4-dibromonaphthalene in the virtual template molecular template mixture was 1 mmol:2 mmol.
[0023] The conditions for gas chromatography analysis were as follows: a DB-5MS capillary column was used; the injection method was splitless injection, and the injection volume was 1 μL; the carrier gas was helium with a purity of 99.999%, and the flow rate was 1.0 mL / min. When performing gas chromatography analysis, the following temperature program is used: hold the initial temperature of 100℃ for 2 min; increase the temperature to 300℃ at 12℃ / min and hold for 10 min; then increase the temperature to 310℃ at 20℃ / min and hold for 4 min.
[0024] The mass spectrometry detection conditions were as follows: electron impact ionization (EI) was used; the transfer line temperature was 250℃; the ion source temperature was 230℃; the solvent delay time was 5 min; and the ion monitoring mode was selected to detect the target polychlorinated naphthalene homologues. The internal standard method uses 13C12-labeled isotopic internal standards for 1-chloronaphthalene, 1,5-dichloronaphthalene, 1,2,3-trichloronaphthalene, 1,2,3,4-tetrachloronaphthalene, 1,2,3,5,7-pentachloronaphthalene, 1,2,3,4,6,7-hexachloronaphthalene, 1,2,3,4,5,6,7-heptachloronaphthalene, and octachloronaphthalene.
[0025] The test data of polychlorinated naphthalene obtained in this embodiment are recorded in the table below:
[0026] As shown in the table above, the accuracy (recovery rate) and precision (RSD) of this embodiment are within acceptable ranges at different spiking concentrations, indicating that the detection method is effective and reliable.
[0027] Example 2 A method for detecting polychlorinated naphthalenes in wheat flour based on magnetic solid-phase extraction-gas chromatography-mass spectrometry includes the following steps: Step 1: Homogenize the wheat flour sample to be tested, then weigh 5.0g of the wheat flour sample to be tested and place it in a centrifuge tube and add 30mL of acetonitrile. Vortex mix for 3min and then extract by sonication for 20min. Then centrifuge at 5℃, collect the supernatant, concentrate it to 0.1mL and add 10mL of ultrapure water and mix well to obtain wheat flour sample extract. The power during ultrasonic extraction was set to 500W, and the ultrasonic frequency was set to 45kHz. The centrifugation speed was set to 5000 r / min, and the centrifugation time was set to 5 min. Step 2: Add 50 mg of magnetic adsorbent and 2 g of sodium chloride to the wheat flour sample extract, vortex mix for 3 min, and then oscillate at 800 Hz at room temperature for 30 min to adsorb. Step 3: Use an external magnet to separate the magnetic adsorbent that adsorbed the target substance in Step 2 from the solution. Discard the supernatant and wash the magnetic adsorbent with ultrapure water. Discard the washing liquid and elute with a hexane-acetone mixed solvent. After vortexing for 3 minutes, collect all the eluent under the action of an external magnet. The volume ratio of hexane to acetone in the hexane-acetone mixed solvent is 8:2. Step 4: Blow the eluent collected in Step 3 to near dryness with nitrogen in a 50°C water bath, then redissolve it with n-hexane, vortex mix it, and transfer the resulting solution to a vial for subsequent analysis. Step 5: Prepare a series of polychlorinated naphthalene standard working solutions and use gas chromatography-mass spectrometry to determine and analyze the solutions obtained in Step 4 and the polychlorinated naphthalene standard working solutions. Select ion monitoring mode for detection, qualitatively identify polychlorinated naphthalene based on retention time and characteristic ions, and quantify using the internal standard method. The internal standard method for quantification includes the following steps: Step 1: Plot a standard curve with the ratio of the peak area of the analyte to the peak area of the internal standard in a series of polychlorinated naphthalene standard solutions as the ordinate and the ratio of the concentration of the analyte to the concentration of the internal standard in the standard solutions as the abscissa. The second step is to calculate the content of polychlorinated naphthalene using the following formula: ; In the formula, : Indicates the content of polychlorinated naphthalene in the sample, in mg / kg; : Indicates the mass concentration of polychlorinated naphthalene in the sample solution obtained from the standard curve, in ng / mL; : Indicates the final volume of the sample solution, in mL; : Indicates the mass of the sample taken, in grams; : Indicates the dilution factor.
[0028] The preparation method of magnetic adsorbent includes the following steps: Step 1: Synthesis of tannic acid-modified magnetic iron(III) oxide (Fe3O4@TA): Nano-iron oxide (Fe3O4@TA) with a mass of 25 times that of tannic acid was added to a 1 mol / L aqueous solution of tannic acid. The mixture was stirred at room temperature for 2 h, magnetically separated, washed three times with water, and dried under vacuum at 60 °C to obtain tannic acid-modified magnetic iron oxide (Fe3O4@TA). Step 2: Synthesis of RAFT-modified magnetic iron(III) oxide (Fe3O4@TA-RAFT): Fe3O4@TA was dispersed in anhydrous ethanol, and 4-cyano-4-[(dodecylthio)carbonyl]thiopentanoic acid (CDTPA) and N,N'-dicyclohexylcarbodiimide (DCC) were added. The mixture was reacted at room temperature in the dark for 12 h, followed by magnetic separation and washing with ethanol to obtain Fe3O4@TA-RAFT. The ratio of Fe3O4@TA, anhydrous ethanol, CDTPA, and DCC was 1 g:30 mL:10 mg:16 mg. Step 3: Synthesize the target magnetic molecular imprinted adsorbent: A virtual template molecular template mixture, 4-vinyl-3-fluorophenylboronic acid (4-VFBA), and ethylene glycol dimethacrylate (EGDMA) were dissolved in ethanol / water (volume ratio 4:1) and shaken at room temperature for 4 h to form a halogen bond / π-π pre-assembled complex. Fe3O4@TA-RAFT and azobisisobutyronitrile (AIBN) were added, and the mixture was ultrasonically dispersed for 5 min and purged with nitrogen for 10 min. The mixture was then reacted in an oil bath at 60 °C for 12 h with shaking. After magnetic separation, the mixture was washed three times with ethanol and dried under vacuum at 60 °C to obtain the target magnetic molecularly imprinted adsorbent. The ratio of the virtual template molecular template mixture, 4-vinyl-3-fluorophenylboronic acid (4-VFBA), ethylene glycol dimethacrylate (EGDMA), Fe3O4@TA-RAFT, and azobisisobutyronitrile was 1 mmol:5 mmol:20 mmol:0.15 g:0.25 mg. The ratio of 1-bromonaphthalene and 1,4-dibromonaphthalene in the virtual template molecular template mixture was 1 mmol:1-3 mmol.
[0029] The series of polychlorinated naphthalene standard working solutions are mixed polychlorinated naphthalene standard working solutions with mass concentrations of 10 μg / L, 20 μg / L, 50 μg / L, 100 μg / L, and 200 μg / L, and the concentration of internal standard in the mixed polychlorinated naphthalene standard working solutions is 50 μg / L.
[0030] The conditions for gas chromatography analysis were as follows: a DB-5MS capillary column was used; the injection method was splitless injection, and the injection volume was 3 μL; the carrier gas was helium with a purity of 99.999% and the flow rate was 1.0 mL / min.
[0031] When performing gas chromatography analysis, the following temperature program is used: hold the initial temperature of 100℃ for 3 min; increase the temperature to 300℃ at 10℃ / min and hold for 12 min; then increase the temperature to 310℃ at 20℃ / min and hold for 4 min.
[0032] The mass spectrometry detection conditions were as follows: electron impact ionization (EI) was used as the ionization method; the transfer line temperature was 280℃; the ion source temperature was 250℃; the solvent delay time was 5 min; and the ion monitoring mode was selected to detect the target polychlorinated naphthalene homologues.
[0033] The internal standard method uses 13C12-labeled isotopic internal standards for 1-chloronaphthalene, 1,5-dichloronaphthalene, 1,2,3-trichloronaphthalene, 1,2,3,4-tetrachloronaphthalene, 1,2,3,5,7-pentachloronaphthalene, 1,2,3,4,6,7-hexachloronaphthalene, 1,2,3,4,5,6,7-heptachloronaphthalene, and octachloronaphthalene.
[0034] The test data of polychlorinated naphthalene obtained in this embodiment are recorded in the table below: Table 2
[0035] As shown in the table above, the accuracy (recovery rate) and precision (RSD) of this embodiment are within acceptable ranges at different spiking concentrations, indicating that the detection method is effective and reliable.
[0036] The detection method for polychlorinated naphthalenes provided by this invention has the advantages of simple operation, rapid speed, high sensitivity, and environmental friendliness. It is suitable for the efficient and accurate detection of polychlorinated naphthalenes in various foods such as grains and their products, meat and their products, aquatic products and their products, and vegetables. This indicates that the detection method for polychlorinated naphthalenes in food based on magnetic solid-phase extraction-mass spectrometry provided by this invention has a broader market prospect and is more suitable for widespread application.
[0037] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0038] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims
1. A method for detecting polychlorinated naphthalenes in food based on magnetic solid-phase extraction-gas chromatography-mass spectrometry, characterized in that, Includes the following steps: Step 1: Homogenize the food sample to be tested, then weigh 1.0-5.0g of the food sample to be tested and place it in a centrifuge tube and add 10-30mL of acetonitrile. Vortex mix for 1-3min, then extract by sonication for 10-20min. Then centrifuge at 3-5℃, collect the supernatant, concentrate it to 0.1mL and add 10mL of ultrapure water and mix well to obtain the food sample extract. Step 2: Add 10-50 mg of magnetic adsorbent and 0.5-2 g of sodium chloride to the food sample extract, vortex mix for 1-3 min, and then oscillate at a frequency of 600-800 Hz at room temperature for 10-30 min to adsorb. Step 3: Use an external magnet to separate the magnetic adsorbent that adsorbed the target substance in Step 2 from the solution. Discard the supernatant and wash the magnetic adsorbent with ultrapure water. Discard the washing liquid and elute with a hexane-acetone mixed solvent. After vortexing for 2-3 minutes, collect all the eluent under the action of an external magnet. The volume ratio of hexane to acetone in the hexane-acetone mixed solvent is 8:
2. Step 4: Blow the eluent collected in Step 3 to near dryness with nitrogen in a water bath at 40-50℃, then redissolve it with n-hexane, vortex mix it, and transfer the resulting solution to a vial for subsequent analysis. Step 5: Prepare a series of polychlorinated naphthalene standard working solutions and use gas chromatography-mass spectrometry to determine and analyze the solutions obtained in Step 4 and the polychlorinated naphthalene standard working solutions. Select ion monitoring mode for detection, qualitatively identify polychlorinated naphthalene based on retention time and characteristic ions, and quantify using the internal standard method. The internal standard method for quantification includes the following steps: Step 1: Plot a standard curve with the ratio of the peak area of the analyte to the peak area of the internal standard in a series of polychlorinated naphthalene standard solutions as the ordinate and the ratio of the concentration of the analyte to the concentration of the internal standard in the standard solutions as the abscissa. The second step is to calculate the content of the polychlorinated naphthalene using the following formula: ； In the formula, : Indicates the content of polychlorinated naphthalene in the sample, in mg / kg; : Indicates the mass concentration of polychlorinated naphthalene in the sample solution obtained from the standard curve, in ng / mL; : Indicates the final volume of the sample solution, in mL; : Indicates the mass of the sample taken, in grams; : Indicates the dilution factor.
2. The method for detecting polychlorinated naphthalenes in food based on magnetic solid-phase extraction-gas chromatography-mass spectrometry according to claim 1, characterized in that: In step one, the power for ultrasonic extraction is set to 300-500W, and the ultrasonic frequency is set to 35-45kHz.
3. The method for detecting polychlorinated naphthalenes in food based on magnetic solid-phase extraction-gas chromatography-mass spectrometry according to claim 1, characterized in that: In step one, the centrifugation speed is set to 3500-5000 r / min, and the centrifugation time is set to 5-10 min.
4. The method for detecting polychlorinated naphthalenes in food based on magnetic solid phase extraction-gas chromatography-mass spectrometry according to claim 1, characterized in that, The preparation method of the magnetic adsorbent includes the following steps: Step 1: Synthesis of tannic acid-modified magnetic iron(III) oxide: Nano-iron oxide (Fe3O4) with a mass of 20-40 times that of tannic acid was added to a 0.8-1.2 mol / L aqueous solution of tannic acid. The mixture was stirred at room temperature for 2 hours, magnetically separated, washed three times with water, and dried under vacuum at 60°C to obtain tannic acid-modified magnetic iron oxide. Step 2: Synthesis of RAFT-modified magnetic iron(III) oxide: Tannic acid-modified magnetic iron oxide was dispersed in anhydrous ethanol; 4-cyano-4-[(dodecylthio)carbonyl]thiovalerate and N,N'-dicyclohexylcarbodiimide were added, and the mixture was reacted at room temperature in the dark for 12 h. After magnetic separation and washing with ethanol, RAFT-modified magnetic iron oxide was obtained. The ratio of tannic acid-modified magnetic iron oxide, anhydrous ethanol, 4-cyano-4-[(dodecylthio)carbonyl]thiovalerate and N,N'-dicyclohexylcarbodiimide was 1 g:30 mL:5-20 mg:10-40 mg. Step 3: Synthesize the target magnetic molecular imprinted adsorbent: The virtual template molecular template mixture, 4-vinyl-3-fluorophenylboronic acid, and ethylene glycol dimethacrylate were dissolved in ethanol / water (volume ratio 4:1) and shaken at room temperature for 4 h. RAFT-modified magnetic iron oxide and azobisisobutyronitrile were added, and the mixture was ultrasonically dispersed for 5 min, followed by nitrogen purging for 10 min. The mixture was then reacted in an oil bath at 60 °C with shaking for 12 h. Magnetic separation was performed, followed by washing three times with ethanol and vacuum drying at 60 °C to obtain the target magnetic molecularly imprinted adsorbent. The ratio of the virtual template molecular template mixture, 4-vinyl-3-fluorophenylboronic acid, ethylene glycol dimethacrylate, RAFT-modified magnetic iron oxide, and azobisisobutyronitrile was 1 mmol:4-8 mmol:18-20 mmol:0.1-0.5 g:0.2-0.8 mg. The ratio of 1-bromonaphthalene and 1,4-dibromonaphthalene in the virtual template molecular template mixture was 1 mmol:1-4 mmol.
5. The method for detecting polychlorinated naphthalenes in food based on magnetic solid-phase extraction-gas chromatography-mass spectrometry according to claim 1, characterized in that: The series of polychlorinated naphthalene standard working solutions are mixed polychlorinated naphthalene standard working solutions with mass concentrations of 10 μg / L, 20 μg / L, 50 μg / L, 100 μg / L, and 200 μg / L, and the concentration of the internal standard in the mixed polychlorinated naphthalene standard working solution is 50 μg / L.
6. The method for detecting polychlorinated naphthalenes in food based on magnetic solid-phase extraction-gas chromatography-mass spectrometry according to claim 1, characterized in that, The conditions for gas chromatography analysis were as follows: DB-5MS capillary column was used; the injection method was splitless injection, and the injection volume was 1-3 μL; the carrier gas was helium with a purity of 99.999% and the flow rate was 1.0 mL / min.
7. The method for detecting polychlorinated naphthalenes in food based on magnetic solid-phase extraction-gas chromatography-mass spectrometry according to claim 1, characterized in that, When performing gas chromatography analysis, the following steps are used for temperature programming: hold the initial temperature of 100℃ for 1-4 min; increase the temperature to 300℃ at 8-14℃ / min and hold for 8-12 min; then increase the temperature to 310℃ at 20℃ / min and hold for 4 min.
8. The method for detecting polychlorinated naphthalenes in food based on magnetic solid-phase extraction-gas chromatography-mass spectrometry according to claim 1, characterized in that, The mass spectrometry detection conditions were as follows: electron impact ionization (EI) was used as the ionization method; the transfer line temperature was 250-280℃; the ion source temperature was 230-250℃; the solvent delay time was 4-6 min; and the ion monitoring mode was selected to detect the target polychlorinated naphthalene homologues.
9. The method for detecting polychlorinated naphthalenes in food based on magnetic solid-phase extraction-gas chromatography-mass spectrometry according to claim 1, characterized in that: The isotopic internal standard used in the internal standard method described in step five is: 13 C 12 The labeled 1-chloronaphthalene, 1,5-dichloronaphthalene, 1,2,3-trichloronaphthalene, 1,2,3,4-tetrachloronaphthalene, 1,2,3,5,7-pentachloronaphthalene, 1,2,3,4,6,7-hexachloronaphthalene, 1,2,3,4,5,6,7-heptachloronaphthalene, and octachloronaphthalene.
10. The method for detecting polychlorinated naphthalenes in food based on magnetic solid-phase extraction-gas chromatography-mass spectrometry according to claim 1, characterized in that, The food sample to be tested can be any one of grains and their products, meat and its products, aquatic products and their products, or vegetables.