Method for analyzing chlorinated paraffin in environment or food sample
By employing a two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry technique, combined with characteristic ion extraction and chlorine content correction, the problem of separating and quantifying chlorinated paraffins in food samples was solved, achieving highly selective and sensitive analytical results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- RES CENT FOR ECO ENVIRONMENTAL SCI THE CHINESE ACAD OF SCI
- Filing Date
- 2026-03-13
- Publication Date
- 2026-05-05
AI Technical Summary
Existing technologies struggle to accurately separate and quantify chlorinated paraffins in complex matrices, especially in food samples, where issues such as peak overlap, signal interference, and quantitative errors exist.
A two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry technique was used, combined with characteristic ion extraction and two-dimensional retention time, and quantitative analysis was performed using a standard curve method based on chlorine content correction.
It achieves highly selective and sensitive separation of chlorinated paraffins in complex matrices, significantly reduces quantitative errors, improves the accuracy and reliability of analysis, and meets the high-precision analysis requirements of chlorinated paraffins in environmental or food samples.
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Figure CN121978250A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of analytical testing technology, specifically relating to a method for analyzing chlorinated paraffins in environmental or food samples, and more specifically, relating to a method for analyzing chlorinated paraffins in environmental or food samples using a two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry technique. Background Technology
[0002] Chlorinated paraffins (CPs) are a class of synthetically produced straight-chain chlorinated alkane derivatives. As important industrial raw materials, they are widely used in the production of flame retardants, plasticizers, lubricants, and metal cutting fluids. Based on carbon chain length, chlorinated paraffins can be classified into short-chain (SCCPs, C...) 10 -C 13 ), and medium chain (MCCPs, C 14 -C 17Chlorinated paraffins are categorized into three types: SCCPs (persistent organic pollutants) and long-chain (LCCPs, C18 and above). Among these, SCCPs and MCCPs, due to their persistence, bioaccumulation, toxicity, and long-distance migration potential, have been listed as persistent organic pollutants under the Stockholm Convention and are subject to strict global restrictions. Despite the enormous cumulative production of chlorinated paraffins, the diverse specifications of industrial products, varying chlorine content, and lack of effective recycling and treatment regulations mean that large quantities of CPs enter the environmental media, posing a potential threat to ecosystems and human health. Accurate detection and quantification of chlorinated paraffins (CPs) in food has always been a serious challenge in the field of analytical chemistry. CPs are complex mixtures composed of thousands of homologues and isomers, with extremely similar physicochemical properties among the components, making effective separation difficult with traditional one-dimensional chromatography. Severe peak overlap and co-elution are common, and even with mass spectrometry, it is difficult to distinguish between different co-eluting components. While conventional mass spectrometry offers high selectivity in electron capture ionization (ECNI) mode, it is still prone to signal interference when faced with complex food matrices (such as oils, grains, meats, and condiments) containing other organochlorinated compounds like toxaphene and polychlorinated biphenyls, as well as interfering components such as lipids, pigments, and macromolecular nutrients inherent in the food itself. Furthermore, homologues with different carbon and chlorine numbers exhibit nominal mass differences at unit mass resolution. The potential overlap of identical isotopes poses a significant challenge. More critically, the lack of pure standard reference materials covering all homologues, coupled with the strong dependence of ionization source response on the chlorine content of compounds, and the substantial influence of chlorine content distribution in food raw materials and processing techniques (such as high-temperature cooking, fermentation, and refining), means that direct quantification using a single standard can lead to substantial errors due to inconsistencies in chlorine content distribution between the sample and the standard. Furthermore, the abundance of lipids, proteins, and other halogenated organic compounds in food samples creates greater matrix interference compared to environmental samples, further complicating pretreatment and purification and severely impacting detection sensitivity and result stability. For example, high-oil foods readily co-extract with chlorinated paraffins, while trace amounts of pigments and plant macromolecules in low-fat foods (vegetables, grains) can inhibit detection signals. Therefore, there is an urgent need to develop a method combining strong separation capabilities with a comprehensive two-dimensional chromatography technique and targeted quantitative correction strategies to achieve accurate analysis of chlorinated paraffins in food on a conventional mass spectrometry platform, providing technical support for chlorinated paraffin contamination risk assessment and food safety management. Summary of the Invention
[0003] In view of this, the present invention provides a method for analyzing chlorinated paraffins in environmental or food samples using a full two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry, so as to at least partially solve the above-mentioned technical problems.
[0004] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:
[0005] A method for analyzing chlorinated paraffins in environmental or food samples using a two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry method includes the following steps: 1) The chlorinated paraffin components in environmental or food samples are enriched and extracted, and then further purified to obtain the sample to be tested; 2) The chlorinated paraffin in the test sample was detected by a two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry. 3) Characteristic ion extraction and two-dimensional retention time were used to obtain the response information of each component in the chlorinated paraffin; 4) Quantitative analysis of each component in the chlorinated paraffin was performed using a standard curve method based on chlorine content correction.
[0006] In step 1) of the above method, the operation of enriching and extracting chlorinated paraffin components from environmental or food samples to obtain the test sample includes: The environmental or food sample is dried to constant weight and then ground to obtain sample powder; The chlorinated paraffin component in the sample powder was extracted using accelerated solvent extraction to obtain the extract. The extract was concentrated, purified, further concentrated, and diluted to a fixed volume to obtain the sample to be tested.
[0007] In step 2) of the above method, the operation of detecting chlorinated paraffin in the sample using full two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry includes: The sample to be tested was injected into a full two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometer; The components of chlorinated paraffin in the test sample were orthogonally separated using two columns of different polarities and a thermal modulator in a two-dimensional gas chromatography system. The samples were then ionized by an electron capture negative ion source and detected by a quadrupole mass spectrometer to obtain a mass spectrum.
[0008] Step 3) of the above method involves obtaining the response information of each component in chlorinated paraffin using characteristic ion extraction and two-dimensional retention time. This includes: Qualitative analysis of the mass spectra was performed using dedicated two-dimensional chromatography-quadrupole mass spectrometry data processing software. Characteristic [M-Cl] components of chlorinated paraffin were extracted within a preset mass range. - Ions are classified as qualitative and quantitative ions; Based on the retention time of each homologue group in the standard solution in the two-dimensional chromatographic space, the response area of each homologue group of chlorinated paraffin in the test sample is obtained.
[0009] Step 4) of the above method involves quantitative analysis of each component in chlorinated paraffin using a standard curve method based on chlorine content correction. Prepare chlorinated paraffin standard solutions with different chlorine contents, and add equal amounts of recovery internal standard and injection internal standard to the chlorinated paraffin standard solutions; The standard solution containing the internal standard was detected by a full two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometer. Using feature [M-Cl] - Ion extraction and two-dimensional retention time were used to obtain the relative peak areas and measured chlorine content between the chlorinated paraffin homologues and the internal standard in the standard solution. The relative response factor was obtained by combining the content of the chlorinated paraffin standard solution, and a standard curve was plotted. Based on the response area of each component of chlorinated paraffin in the test sample and the measured chlorine content, combined with the linear equation of the standard curve, the correction response factor of chlorinated paraffin in the test sample is obtained. The total content of chlorinated paraffin and the content of each component in the sample were calculated based on the correction response factor of chlorinated paraffin in the sample.
[0010] In step 1) of the above method, the environmental or food sample includes a food sample and an air sampling filter membrane; The accelerated extraction method uses diatomaceous earth as the filling material in the extraction tank, and trans-chlordane is added to the extraction tank as an internal standard for recovery. The extraction solvent includes a mixture of dichloromethane and n-hexane. The accelerated extraction method uses an extraction temperature of 100±5℃, a pressure of 10342±100 KPa, a heating time of 5±1 min, a static time of 10±2 min, a rinsing volume of 60% of the extraction tank volume, and a purging time of 60±5 s.
[0011] The operations of concentrating, purifying, re-concentrating, and adjusting the volume of the extract include: The extract was concentrated using a rotary evaporator and then transferred to a silica-alumina composite chromatography column for purification. The purified solution was then further concentrated using a rotary evaporator and a nitrogen blower. Hexachlorocyclohexane was added to the concentrated solution as an internal standard for injection, and the volume was adjusted with cyclohexane to obtain the sample to be tested.
[0012] In step 2) of the above method, in the two-dimensional gas chromatography, high-purity helium is used as the carrier gas, the flow rate is 1.0~1.5mL / min, and the injection volume is 0.5~2.0 μL; The modulator uses thermal modulation with a modulation cycle of 6.0~10.0, and the length of the second-dimensional chromatographic column is 0.5~2.0m; The first-dimensional chromatographic column is a non-polar stationary phase, and the second-dimensional chromatographic column is a moderately polar stationary phase.
[0013] In electron capture negative ionization-quadrupole mass spectrometry, an electron capture negative ionization (ECNI) ion source was used, methane was used as the reaction gas, and the flow rate was 1.5-2.5 mL / min; The filament current is 50~70 μA, the electron energy is 200~250 eV, the ion source temperature is set to 200~300℃, and the transmission line temperature is 250~300℃. The mass acquisition range is 50–1200 m / z, the scanning mode is selected ion monitoring (SIM), and the mass resolution is unit mass resolution.
[0014] The relative peak areas and measured chlorine content of each component in the chlorinated paraffin standard solution were calculated using the following strategy: First, chlorinated paraffin homologues with the same two-dimensional retention time characteristics in the mass spectrum are divided into several homologue groups, and the peak area of each group is calculated. Relative response value of chlorinated paraffin homologues = Peak area of chlorinated paraffin homologues ÷ Peak area of recovered internal standard; The measured chlorine content of a chlorinated paraffin sample = Σ(peak area of each homologue group × theoretical chlorine content of that group) ÷ Σ(peak area of each homologue group); The relative response values of each homologue of the chlorinated paraffin are summed to obtain the total relative response value. The total response factor of the standard solution is then calculated using the following formula: Total response factor of chlorinated paraffin = Total relative response value of chlorinated paraffin ÷ Total concentration of chlorinated paraffin standard solution; Using the total response factor of the chlorinated paraffin as the ordinate and the measured chlorine content of the chlorinated paraffin as the abscissa, a linear fit is performed to obtain the chlorine content correction standard curve.
[0015] The components of the chlorinated paraffin include C n H 2n+2-m Cl m ; Where n represents the number of carbon atoms, which is an integer from 10 to 17; m represents the number of chlorine atoms, which is an integer from 5 to n.
[0016] Based on the above technical solution, the method for analyzing chlorinated paraffins in environmental or food samples using a two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry provided by the present invention has at least one of the following beneficial effects: (1) In the embodiments of the present invention, the all-two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry technology provided by the present invention cleverly combines the extremely high peak capacity separation capability of all-two-dimensional gas chromatography with the high selectivity and high sensitivity of the electron capture negative ion source for halogenated compounds. This technology can effectively distinguish co-eluting components in complex matrices through orthogonal separation in unit mass resolution mode, and rapidly and accurately obtain the target chlorinated paraffin homologues (C... 10 -C 17 Characteristic ion response information.
[0017] (2) In the embodiments of the present invention, the orthogonal separation efficiency of the two-dimensional chromatography is extremely high, and the separation effect of chlorinated paraffins is significantly better than that of traditional one-dimensional chromatography, which can separate short-chain (SCCPs, C 10 -C 13 ) and middle chains (MCCPs, C 14 -C 17 Chlorinated paraffins were separated into unique "roof tile" patterns based on carbon and chlorine numbers. Simultaneously, two-dimensional chromatography was used to completely separate chlorinated paraffins from interfering substances such as toxaphene and polychlorinated biphenyls (PCBs) along the retention time dimension, and characteristic [M-Cl] was extracted using quadrupole mass spectrometry in selected ion monitoring (SIM) mode. - The method effectively eliminates isotopic interference from organohalogenated compounds and matrix background noise. It is particularly suitable for environmental or food samples containing complex matrices, such as biological tissues or sediment samples with high lipid content, reducing instrument costs and maintenance complexity while maintaining high selectivity.
[0018] (3) In the embodiments of the present invention, by establishing a linear correction model of "total response factor and measured chlorine content", the quantitative error problem caused by the inconsistency of chlorine content distribution between industrial standards and environmental or food samples is innovatively solved. This quantitative strategy does not rely on the high resolution of mass spectrometry, but corrects by calculating the weighted chlorine content of the sample and back-deriving the specific response factor, overcoming the defect that a single standard cannot represent the response behavior of complex mixtures. Experiments show that this strategy significantly reduces the quantitative relative error from more than 50% of the traditional method to less than 15%, significantly improving the accuracy and comparability of the data, enabling high-precision quantitative analysis of chlorinated paraffins on a conventional quadrupole mass spectrometry platform.
[0019] (4) In an embodiment of the present invention, by extracting feature [M-Cl] -Ion and two-dimensional retention time can accurately determine the presence and relative content of target compounds, and the total amount of CPs in the sample can be determined by combining the chlorine content correction standard curve method. Thanks to the high ionization efficiency of the ECNI source and the enrichment effect of full two-dimensional chromatography, the detection limit of this method can reach the nanogram / gram (ng / g) level, exhibiting high sensitivity, accuracy, and precision. Simultaneously, the systematic screening capability based on the retention patterns of full two-dimensional chromatography enables this method to comprehensively cover and accurately quantify common Cs in environmental or food samples. 10 -C 17 Chlorinated paraffins effectively meet the practical needs of comprehensive analysis of short-chain and medium-chain chlorinated paraffins in current environmental or food monitoring. Attached Figure Description
[0020] Figure 1 This is a flowchart of the method for analyzing chlorinated paraffins in environmental or food samples using two-dimensional gas chromatography-electron capture negative ionization-quadrupole mass spectrometry, as described in this invention.
[0021] Figure 2 This is a standard curve diagram of short-chain chlorinated paraffins in an embodiment of the present invention.
[0022] Figure 3 This is a standard curve diagram of medium-chain chlorinated paraffin in an embodiment of the present invention. Detailed Implementation
[0023] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.
[0024] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.
[0025] Currently, common methods for detecting chlorinated paraffins include gas chromatography-electron capture detector (GC-ECD), gas chromatography-electron capture negative ionization mass spectrometry (GC-ECNI-MS), and liquid chromatography-tandem mass spectrometry (LC-MS / MS). While GC-ECD is simple to operate and inexpensive, it lacks qualitative capabilities, only determining the total amount of chlorinated paraffins and unable to distinguish homologues with different carbon and chlorine numbers. Furthermore, its dynamic range is narrow, primarily suitable for short-chain chlorinated paraffins (SCCPs), and it struggles with complex matrices. GC-ECNI-MS offers better selectivity and sensitivity, but its separation capability is limited in traditional one-dimensional gas chromatography mode. When dealing with thousands of homologues and isomers of chlorinated paraffins, severe co-elution occurs, leading to signal superposition between different components. Simultaneously, structurally similar organohalogenated compounds such as toxaphene and polychlorinated biphenyls commonly found in environmental samples can cause isotopic interference, severely affecting the accuracy of qualitative and quantitative analysis. Furthermore, the quantitative results of this method are highly dependent on the matching degree of chlorine content between the standard and the sample. If the distributions of the two are inconsistent, a large quantitative error will occur. Although liquid chromatography-tandem mass spectrometry (LC-MS / MS) has certain advantages in the analysis of long-chain chlorinated paraffins (MCCPs), its ionization efficiency is relatively low, and it also faces complex matrix effects. Its quantification usually relies on complex mathematical deconvolution algorithms, and the measurement results are highly susceptible to the influence of the standard composition model. When the actual environmental sample differs significantly from the standard model, the error increases significantly, and the requirements for the mobile phase system are stringent.
[0026] In view of this, the present invention provides a method for analyzing chlorinated paraffins in environmental or food samples using a two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry. This method utilizes the orthogonal separation capability of two-dimensional chromatography to solve the co-elution problem, combines selected ion monitoring mode to eliminate isotope and matrix interference, and innovatively introduces a chlorine content correction strategy, significantly improving the C... 10 -C 17 The accuracy and reliability of qualitative and quantitative analysis of chlorinated paraffins.
[0027] Specifically, according to embodiments of the present invention, a method for analyzing chlorinated paraffins in environmental or food samples using two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry is provided. Figure 1 is a flowchart of the method for analyzing chlorinated paraffins in environmental or food samples using two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry according to an embodiment of the present invention. As shown in Figure 1, the method includes the following steps S1 to S4: In step S1, the chlorinated paraffin components in the environmental or food samples are enriched, extracted, and purified to obtain the sample to be tested. In step S2, chlorinated paraffin in the sample is detected by full two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry. In step S3, feature [M-Cl] is used. - Ion selection monitoring (SIM) and two-dimensional retention time were used to obtain response information of each homologue group in chlorinated paraffin; In step S4, the components in chlorinated paraffin are quantitatively analyzed using a standard curve method based on chlorine content correction.
[0028] According to embodiments of the present invention, chlorinated paraffin components are extracted from environmental or food samples through enrichment and detected by a two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry. This method has strong anti-interference capabilities and can effectively separate and detect the content of short-chain and medium-chain chlorinated paraffins of C10-C17. The qualitative method is based on characteristic fragment ions and orthogonal retention behavior, and does not rely on fingerprint matching of a single standard substance. The quantitative method adopts a chlorine content correction strategy, which has high sensitivity and significantly reduces the quantitative deviation caused by differences in chlorine content distribution. This method can meet the high-precision analysis requirements of CPs in actual environmental or food samples.
[0029] According to an embodiment of the present invention, step S1 involves enriching and extracting chlorinated paraffin components from environmental or food samples to obtain the sample to be tested, including steps S101 to S103: In step S101, the environmental or food sample is dried to constant weight and ground to obtain sample powder; In step S102, the chlorinated paraffin component in the sample powder is extracted using an accelerated solvent extraction method to obtain an extract. In step S103, the extract is concentrated, purified by chromatography column, further concentrated and diluted to a fixed volume to obtain the sample to be tested.
[0030] According to an embodiment of the present invention, the environmental or food samples include food samples (such as meat, total diet, etc.) and air sampling filter membranes, etc. The collected samples are air-dried or freeze-dried to constant weight, ground into powder and passed through a sieve for later use.
[0031] According to an embodiment of the present invention, in step S102, the accelerated solvent extraction method can reduce the environmental pollution caused by solvent evaporation and has the advantages of low organic solvent consumption, high extraction efficiency, high recovery rate, and automated operation. In the accelerated solvent extraction method, the filling material of the extraction tank is diatomaceous earth, and trans-chlordane is added to the extraction tank as a surrogate standard to monitor the pretreatment recovery rate; the extraction solvent includes a mixture of dichloromethane and n-hexane (volume ratio 1:1); the extraction temperature of the accelerated solvent extraction method is 100±5℃, the pressure is 10342±100 KPa (approximately 1500 psi), the heating time is 5±1 min, the static time is 10±2 min, the rinsing volume is 60% of the extraction tank volume, and the purging time is 60±5 s.
[0032] According to embodiments of the present invention, an organohalogenated compound or isotope labeling compound that is stable with chlorinated paraffin, can coexist with it, and has similar extraction behavior can be added as a substitute standard to monitor the recovery rate of the extraction and purification process without affecting the properties of the chlorinated paraffin components or the extraction process. After adding the substitute standard to the extraction tank, the sample and diatomaceous earth are thoroughly mixed, and the above-described accelerated solvent extraction method is used for extraction 2-3 times. The extracts are then combined and collected.
[0033] According to an embodiment of the present invention, step S103 involves concentrating, purifying, re-concentrating, and adjusting the volume of the extract, including: The extract was concentrated using a rotary evaporator and then transferred to a chromatography column for purification. The purified solution was then further concentrated using a rotary evaporator and a nitrogen blower. Add hexachlorocyclohexane as an internal standard to the concentrated solution and dilute to volume with cyclohexane to obtain the sample to be tested.
[0034] According to an embodiment of the present invention, the extract was concentrated to 1-2 mL using a rotary evaporator, and then purified. The purification process used a glass tube with an inner diameter of 1.0 cm, packed from bottom to top with 3 g Florisil, 2 g activated silica gel, 10 g acidic silica gel, and 4 g anhydrous sodium sulfate. Before sample loading, the column was pre-eluted with n-hexane, the eluent was discarded, and then the sample was loaded. Elution was then performed with a mixed solvent of dichloromethane and n-hexane. Specifically, the column was first pre-eluted with 50 mL of n-hexane, the eluent was discarded, the sample was loaded, and then eluted with 40 mL of n-hexane, this eluent was discarded. Subsequently, elution was performed with 100 mL of a chromatographically pure dichloromethane and n-hexane mixed solvent (1:1 v / v), and the purified solution was collected.
[0035] According to embodiments of the present invention, the purification process provided by the present invention is simple and rapid, with a high recovery rate. Only one chromatography column is needed to remove impurities that may interfere with the instrument's determination of CPs to the greatest extent, without causing the loss of CPs.
[0036] According to an embodiment of the present invention, the volume was further concentrated to approximately 40 μL using a rotary evaporator and nitrogen blowing, then 5 ng of internal standard was added, and the volume was adjusted to 100 μL with n-hexane.
[0037] According to an embodiment of the present invention, trans-chlordane (with carbon-13 isotope labeling) is recovered. 13 C 10 The amount of H6Cl8 added was 5 ng, and the internal standard for injection was hexachlorocyclohexane (C6H6Cl6), which was added in an amount of 5 ng.
[0038] According to an embodiment of the present invention, step S2, which uses a full two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry to detect chlorinated paraffin in the sample, includes steps S201 to S202: In step S201, the sample to be tested is injected into a full two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometer; In step S202, the components of chlorinated paraffin in the sample to be tested are orthogonally separated by two columns of different polarities and a thermal modulator in a two-dimensional gas chromatography system. The samples are then ionized by an electron capture negative ion source and detected by a quadrupole mass spectrometer in selected ion monitoring (SIM) mode to obtain a characteristic fragment ion chromatogram.
[0039] According to an embodiment of the present invention, the sample solution and CPs standard solution are aspirated by an autosampler and injected into a two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometer. In the two-dimensional gas chromatography, high-purity helium is used as the carrier gas at a flow rate of 1.0–1.5 mL / min (constant flow mode), and the injection volume is 1.0 μL (splitless or split injection). The modulator uses thermal modulation with a modulation period of 6.0–10.0 s. The length of the second-dimensional column is 0.5–2.0 m. The first-dimensional column is a non-polar stationary phase DB-5ms, and the second-dimensional column is a moderately polar stationary phase BPX-50.
[0040] According to embodiments of the present invention, the temperature program for full two-dimensional gas chromatography is typically as follows: after holding the initial temperature for a certain period of time, the temperature is increased to the final temperature at a certain rate. For example, the initial temperature is 80°C, held for 1 min, then increased to 280°C at a rate of 3°C / min, and held for 10 min. The temperature of the second-dimensional column oven is typically 5-10°C higher than that of the first dimension. The total analysis time is approximately 40-50 minutes to achieve the desired results for SCCPs, MCCPs, and C. 10-C 17 Complete separation of CPs.
[0041] According to an embodiment of the present invention, in electron capture negative ionization-quadrupole mass spectrometry, an electron capture negative ionization (ECNI) ion source is used, the reaction gas is methane, the flow rate is 1.5~2.5 mL / min; the filament current is 50~70 μA, the electron energy is 200~250 eV, the ion source temperature is set to 200~300℃, and the transfer line temperature is 250~300℃; selected ion monitoring (SIM) mode is used, targeting the characteristic fragment ion [M-Cl] of chlorinated paraffin. - Set a specific mass-to-charge ratio for data acquisition, and set the scan dwell time to 10~50 ms.
[0042] According to an embodiment of the present invention, step S3, which uses characteristic ion extraction and two-dimensional retention time to obtain the response information of each component in chlorinated paraffin, includes steps S301 and S302: In step S301, the SIM chromatogram is qualitatively analyzed using GC Image R2.1 software (GC Image, Lincoln, NE, USA), and the characteristic [M-Cl] of chlorinated paraffin is extracted within a preset mass-to-charge ratio window. - Ions are classified as qualitative and quantitative ions; In step S302, the response peak areas of each homologue group in the test sample are obtained based on the retention time of each homologue group in the standard solution in the two-dimensional chromatographic space.
[0043] According to an embodiment of the present invention, by extracting feature [M-Cl] - By calculating the two-dimensional retention time of each component, the presence and relative content of the target compound can be accurately determined. The high orthogonal separation capability of full two-dimensional chromatography can effectively eliminate the co-elution effects of interfering substances such as toxaphene and PCBs.
[0044] According to embodiments of the present invention, the components of chlorinated paraffin include C n H 2n+2-m Cl m ; Where n represents the number of carbon atoms, which is an integer from 10 to 17; and m represents the number of chlorine atoms, which is an integer from 5 to n. For example, m can be 5 to 10 when n is 10, 6 to 12 when n is 14, 5 to 10 when n is 17, etc., but it is not limited to the listed values. Other unlisted values within this range also apply.
[0045] According to embodiments of the present invention, qualitative and quantitative ions of each component in chlorinated paraffin are extracted, primarily focusing on extracting the negatively charged characteristic ion formed after a chlorinated paraffin molecule loses a chlorine atom, namely [M-Cl]. - Where M is a single component of chlorinated paraffin. Using the selected ion monitoring (SIM) function of quadrupole mass spectrometry, a monitoring channel is set for a specific homologue cluster. Quantitative and qualitative ions are obtained from the ion peak with the highest abundance in the isotopic cluster or a specific addition ion peak. The specific mass-to-charge ratio (m / z) to be monitored needs to be calculated based on the actual carbon number and chlorine number, and the specific values are shown in Table 1 below.
[0046] Table 1
[0047] According to an embodiment of the present invention, step S4, which involves quantitative analysis of each component in chlorinated paraffin using a standard curve method based on chlorine content correction, includes steps S401 to S405: In step S401, chlorinated paraffin standard solutions with different chlorine contents are prepared by adding an equal amount of internal standard to the chlorinated paraffin standard solutions. The chlorinated paraffin standard solutions with different chlorine contents are prepared using cyclohexane as a solvent by mixing commercially available chlorinated paraffin standard mixtures with different chlorine contents in different proportions to cover the chlorine content range of short-chain and medium-chain chlorinated paraffins.
[0048] In step S402, a standard solution containing an internal standard is detected using a two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometer. Specifically, the same amount of internal standard as the standard solution is added to the sample to be tested, and the relative peak area and measured chlorine content of each homologue group are measured.
[0049] In step S403, feature [M-Cl] is used. - Ion selective monitoring (SIM) and two-dimensional retention time were used to obtain the relative peak areas and measured chlorine content between the chlorinated paraffin homologues and the internal standard in the standard solution. Combined with the known total concentration of the chlorinated paraffin standard solution, the total relative response factor was obtained, and a chlorine content-corrected standard curve was plotted. The standard curve was plotted with the total relative response factor as the ordinate and the measured chlorine content as the abscissa.
[0050] In step S404, the correction response factor of chlorinated paraffin in the test sample is obtained based on the response area of each homologue of chlorinated paraffin in the test sample and the measured chlorine content, combined with the linear equation of the standard curve.
[0051] In step S405, the total content of chlorinated paraffin and the content of each component in the sample to be tested are calculated based on the correction response factor of chlorinated paraffin in the sample to be tested.
[0052] According to an embodiment of the present invention, the measured chlorine content of CPs in the actual sample is substituted into the linear equation of the standard curve to obtain the corresponding CPs correction response factor. Dividing the total relative response value of CPs measured in the actual sample by the CPs correction response factor yields the total concentration of CPs in the sample. By constructing a series of standard solutions with known and different chlorine contents, and based on the linear relationship between their response factors and chlorine contents, the content of the target compound in the sample can be accurately calculated, effectively overcoming the quantitative error caused by the inconsistent chlorine content distribution between the sample and the standard.
[0053] To address the challenges posed by the diverse range of chlorinated paraffin homologues and the significant differences in mass spectrometry responses resulting from varying chlorine contents, this study established a quantitative strategy based on a combination of characteristic ion peak area weighting and chlorine content correction curves. The specific steps are as follows: Step 1: Calculate the overall relative response value of the standard sample. For short-chain and medium-chain chlorinated paraffin standard samples with different chlorine contents, the following operations were performed: Based on the detection data obtained by full two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry, in selected ion monitoring (SIM) mode, the characteristic chromatographic peak areas of each chlorinated paraffin homologue were identified and integrated; the chromatographic peak areas of each homologue were divided by the corresponding internal standard response factor to obtain the normalized response value of each homologue; the normalized response values of all homologues were summed to obtain the overall relative response value of the standard sample.
[0054] Step 2: Calculate the apparent total response factor of the standard sample. Based on the results obtained in step one, the apparent total response factor of each standard sample is calculated respectively. Specifically, the overall relative response value of the standard sample is divided by the known total concentration of the standard sample to obtain the apparent total response factor corresponding to the specific chlorine content level.
[0055] Step 3: Determine the measured chlorine content of the standard sample. The measured chlorine content of each standard sample was calculated and used as the independent variable for subsequent linear fitting. The specific calculation method is as follows: a peak area weighted average strategy is adopted, that is, the chromatographic peak area of each homologue group is multiplied by its corresponding theoretical chlorine mass fraction to obtain the chlorine contribution value of each group; the chlorine contribution values of all homologue groups are summed and then divided by the sum of the chromatographic peak areas of all homologue groups to obtain the measured chlorine content of the standard sample.
[0056] Step 4: Construct a chlorine content correction model Based on data from multiple sets of standard samples with different chlorine contents, a linear regression model was constructed between the total response factor and the measured chlorine content. Specifically, using the measured chlorine content calculated in step three as the independent variable and the apparent total response factor calculated in step two as the dependent variable, a linear regression equation is obtained through linear fitting. This linear regression equation is characterized as follows: the total response factor equals the product of the slope coefficient and the measured chlorine content, plus the intercept constant. This equation is used to characterize the relationship between the instrument response and the change in sample chlorination degree.
[0057] Step 5: Calculate the total content of short-chain and medium-chain chlorinated paraffins in the actual sample. First, based on the measured chlorine content of the sample to be tested, the corresponding total corrected response factor is calculated using the linear regression equation established in step four. Then, the overall relative response value of the sample to be tested is divided by the total corrected response factor. The resulting quotient is the final measured content of short-chain chlorinated paraffins or medium-chain chlorinated paraffins in the sample to be tested.
[0058] Unless otherwise specified, the techniques or conditions described in the examples are conventional methods and can be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product manual.
[0059] The instruments and reagents used in this invention are as follows: 1. A fully two-dimensional gas chromatography-quadrupole mass spectrometry (GC-MS) system, wherein the gas chromatography section is equipped with a thermal modulator and the chromatograph is an Agilent 7890B; the mass spectrometry section is a quadrupole mass spectrometer, model Agilent 5977B GC / MSD, equipped with an electron capture negative ionization source. The system operates in selected ion monitoring mode to meet the high sensitivity requirements of chlorinated paraffin trace analysis.
[0060] 2. Accelerated solvent extraction instrument, model Dionex ASE 350; 3. Vacuum rotary evaporator; 4. Nitrogen blowing device; 5. Electronic balance; 6. Chromatography column: a glass tube with an inner diameter of 1.0 cm, filled from bottom to top with 3 g Florisil, 2 g activated silica gel, 10 g acidic silica gel, and 4 g anhydrous sodium sulfate; 7. Dichloromethane, n-hexane, methanol, and cyclohexane were all of chromatographic grade. 8. Anhydrous sodium sulfate (analytical grade): Activated at 650℃ for 6.5 h, and stored in a desiccator; 9. Florisil: Activated at 550℃ for 12 h, then stored in a desiccator; 10. Silica gel: Activate at 550℃ for 6.5 hours and store in a desiccator; 11. Acidic silica gel: Weigh 100g of silica gel, add 43mL of concentrated sulfuric acid, mix well on a shaker for 5 hours, and then seal the container. 12 Short-chain chlorinated paraffin standard solutions, with chlorination degrees of 51.5%, 55.5%, and 63%, 100 μg / mL; 13. Medium-chain chlorinated paraffin standard solutions, chlorination degrees of 42%, 52%, and 57%, 100 μg / mL; 14. Long-chain chlorinated paraffin standard solution, chlorination degree 36, 49%, 100 μg / mL; 15-carbon-13 isotope labeled trans-chlordane ( 13 C 10 H6Cl8), internal standard recovered, 100 μg / mL; 16-carbon-13 isotope labeled hexachlorocyclohexane ( 13 C6H6Cl6), internal standard for injection, 100 μg / mL.
[0061] The instrument parameters used in this invention are as follows: SCCPs and MCCPs in atmospheric samples were determined using a two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry system (GC×GC-ECNI-MS, Agilent Technologies, Santa Clara, CA, USA). The chromatographic section was equipped with a thermal modulator. The first-dimensional column was a nonpolar DB-5MS column (30 m × 0.25 mm × 0.25 μm; Agilent Technologies), and the second-dimensional column was a moderately polar BPX-50 column (1.0 m × 0.10 mm × 0.10 μm; SGE, Melbourne, Australia). High-purity helium was used as the carrier gas, and the flow rate was set to 0.8 mL / min (constant flow mode). The injection volume was 1.0 μL, using splitless injection mode, and the injector temperature was 280 °C.
[0062] The chromatographic temperature program is as follows: initial temperature 100℃, hold for 1 min, increase to 140℃ at a rate of 10℃ / min, then increase to 310℃ at a rate of 1.5℃ / min and hold for 5 min. The modulation cycle of the thermal modulator is set to 7s.
[0063] The mass spectrometry section employs an electron capture negative ionization source, with the ion source temperature set at 200 ℃ and the transfer line temperature at 280 ℃. The system operates in selected ion monitoring mode to meet the high sensitivity requirements of chlorinated paraffin trace analysis, performing qualitative and quantitative analysis by extracting characteristic ions.
[0064] The following methods were used to enrich and extract chlorinated paraffin components from environmental or food samples: After the sample was air-dried indoors to constant weight, it was ground into powder. 1 g of the sample was weighed, 5 ng of trans-chlordane was added, and the sample was placed in the extraction cell of an accelerated solvent extractor. The extraction cell was filled with diatomaceous earth. The accelerated solvent extractor was used for extraction. The parameters of the accelerated solvent extractor were as follows: the extraction solvent was a 1:1 volume mixture of dichloromethane and n-hexane, the extraction temperature was 100℃, the system pressure was 10342 kPa, the heating time was 5 minutes, the static time was 10 minutes, the cycle was repeated 3 times, the washing volume was 60%, and the purging time was 60 seconds. The extract was concentrated to approximately 2 mL using a rotary evaporator and transferred to a chromatography column for purification. Before sample loading, the column was pre-eluted with 50 mL of n-hexane. After discarding the eluent, the column was eluted with 40 mL of n-hexane and the eluent was discarded. The concentrated sample solution was then injected into the chromatography column and eluted with a 1:1 mixture of dichloromethane and n-hexane. The solution was collected and then concentrated to near dryness using a rotary evaporator and a nitrogen blower. 5 ng of hexachloro-n-hexane internal standard was added, and the volume was adjusted to 50 μL with n-hexane to obtain the sample to be tested.
[0065] Example 1: Preparation of standard solutions with different chlorination degrees To verify the qualitative and quantitative ability of the method for chlorinated paraffins with different chlorination degrees, this study used a mixed preparation method to prepare a series of standard solutions with different target theoretical chlorination degrees.
[0066] First, three short-chain chlorinated paraffin (SCCP) standard substances with different chlorine contents (51.5%, 55.5%, and 63.0%, respectively) were selected, with a stock solution concentration of 100 µg / mL for each. By mixing these standard substances at different volume ratios and diluting the final mixture to a concentration of 20 µg / mL, a series of mixed SCCP standards covering a target chlorination degree of 51.5% to 63.0% was prepared. Specific ratios are shown in Table 2.
[0067] Table 2. Preparation ratio of mixed standard solutions of SCCPs with different target chlorination degrees
[0068] Similarly, three medium-chain chlorinated paraffin (MCCPs) standards with different chlorine contents (42.0%, 52.0%, and 57.0%, respectively) were selected, with a stock solution concentration of 100 µg / mL. These were mixed and diluted to 20 µg / mL according to the proportions shown in Table 3 to prepare a series of mixed MCCP standards covering a target chlorination degree of 42.0% to 57.0%.
[0069] Table 3. Preparation ratio of mixed standard solutions for MCCPs with different target chlorination degrees
[0070] Example 2: Instrumental Analysis and Chromatographic Behavior Typical standard solutions were analyzed using a two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry system (GC×GC-ECNI-QMS). Taking short-chain chlorinated paraffins (SCCPs) with a chlorine content of 55.5% and medium-chain chlorinated paraffins (MCCPs) with a chlorine content of 52.0% as examples, the results showed that under optimized chromatographic conditions, homologues with different carbon chain lengths and chlorination generations were well separated. Simultaneously, the electron capture negative ionization (ECNI) source combined with selected ion monitoring (SIM) mode effectively suppressed matrix interference and significantly improved the detection signal-to-noise ratio.
[0071] Example 3: Standard Curve and Linear Range Based on the extraction and retention time localization of characteristic ions, the response values of each component were obtained. A standard curve was plotted with concentration on the x-axis and peak area on the y-axis. The results showed that homologues of SCCPs and MCCPs exhibited good linearity (R0) over a wide concentration range. 2 >0.99), which meets the need for simultaneous quantification of multiple components in complex environments or food samples. Figure 2 This is a standard curve diagram for short-chain chlorinated paraffins. Figure 3 This is a standard curve diagram for medium-chain chlorinated paraffins.
[0072] Example 4: Method Detection Limit and Sensitivity The method detection limit (MDL) was determined using a spiked blank sample. The blank sample was prepared by multiple extractions of collected sediment and fish samples using accelerated solvent extraction (ASE) to ensure that the chlorinated paraffin content was below the instrument detection limit. Subsequently, a low concentration of standard solution (1 µg each of SCCPs and MCCPs) was added to the blank matrix, concentrated and purified, and the measurement was repeated three times under a signal-to-noise ratio (S / N) ≥ 3:1.
[0073] The results showed that the relative standard deviations of the analytical results for both SCCPs and MCCPs were less than 20%. In pre-prepared food matrices, the method detection limits (MDL) for SCCPs were 3 ng / g and for MCCPs were 7 ng / g. The detection limits of this method are competitive with traditional high-resolution mass spectrometry methods and are suitable for the accurate analysis and determination of SCCPs and MCCPs in environmental or food samples.
[0074] Example 4: Precision and Accuracy Experiment The precision and accuracy of this method were tested as follows: Benefiting from the highly selective ionization capability of the electron-captured negative ionization (ECNI) source for halogen compounds, and the high quality, precision, and low noise characteristics of high-resolution time-of-flight mass spectrometry (HRTOF-MS), this method exhibits extremely high sensitivity: The method detection limit (MDL) was determined using spiked samples in a blank matrix. Blank samples were selected from pre-prepared foods and packaging materials that had undergone multiple accelerated solvent extraction (ASE) or ultrasonic extraction processes to ensure that the background content of chlorinated paraffins (CPs) was below the instrument detection level. Subsequently, low concentrations of SCCPs and MCCPs standard solutions (spike concentrations set at approximately 3–5 times the expected detection limit) were added to the blank matrix, along with an appropriate amount of isotopic internal standard. After concentration and purification, measurements were repeated three times under a signal-to-noise ratio (S / N) ≥ 3:1, and the method detection limit was calculated using the standard deviation of the response values.
[0075] The results showed that the relative percentage difference (RPD) of both SCCPs and MCCPs was less than 18%, indicating good precision. Under the conditions of this study, the method limit of detection (MDL) for SCCPs in pre-prepared food matrices was 3 ng / g, and the MDL for MCCPs was 7 ng / g; the MDL for SCCPs in packaging material matrices was 4 ng / g, and the MDL for MCCPs was 9 ng / g. The detection limit level of this method can meet the analytical requirements for trace chlorinated paraffins in complex food matrices.
[0076] Example 5: Accuracy Verification To verify the accuracy of the method, two typical matrix samples, pre-prepared food and packaging materials, were selected, and spiked recovery experiments were conducted according to the procedure defined in this method.
[0077] 1. Spike recovery rate of pre-prepared foods The relative percentage deviations (RPDs) of parallel sample analyses were all below 15%, indicating good precision of the analytical method. Spike recoveries were the ratio of the determined concentrations of the purified internal standard (13C10-trans-chlordane) and the injected internal standard (ε-hexachlorocyclohexane) after pretreatment to the concentration ratios of the corresponding standard mixtures. In this study, the spike recoveries of SCCPs and MCCPs in pre-prepared food samples were 48%–67% and 48%–66%, respectively.
[0078] 2. Packaging material recyclability rate The average recoveries of SCCPs were 49%–72%, and those of MCCPs were 46%–70%. The data indicate that despite the complexity of food packaging matrices, this method can still effectively extract and determine the content of chlorinated paraffins.
[0079] The above results indicate that this method has good accuracy and precision under different matrices (pre-prepared food, packaging materials), and the spiked recovery rate and relative deviation meet the requirements for the analysis of contaminants in food contact materials and food.
[0080] Based on the above experimental results, it can be seen that the two-dimensional gas chromatography-electron capture negative ionization-quadrupole mass spectrometry (GC×GC-ECNI-MS) analytical method established in this study performs excellently in the determination of chlorinated paraffins in pre-prepared foods and their packaging materials, providing reliable technical support for assessing the health risks of human intake of chlorinated paraffins through diet.
[0081] The test results showed that the spiked recoveries of short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) in pre-prepared food and packaging material matrices mainly ranged from 46% to 72% (48%–67% for SCCPs and 48%–66% for MCCPs in pre-prepared foods; 49%–72% for SCCPs and 46%–70% for MCCPs in packaging materials), with relative standard deviations (RSDs) all below 18%. Although the absolute recoveries were slightly lower than those in traditional environmental media analysis due to the complex food matrix effect, the quantitative results remained accurate and reliable thanks to the precise calibration of the isotope internal standard method, indicating that the method has good precision and applicability.
[0082] Furthermore, thanks to the excellent peak capacity separation capability of full two-dimensional gas chromatography (GC×GC) and the high selective ionization characteristics of electron capture negative ionization (ECNI) source for halogen compounds, this method has strong resistance to matrix interference and can effectively separate homologues with different carbon chain lengths and chlorination levels, achieving highly sensitive qualitative and quantitative analysis of trace SCCPs and MCCPs in pre-prepared foods and packaging materials.
[0083] In terms of quantitative performance, this method has sensitive limits of detection (as low as 3 ng / g for SCCPs and 7 ng / g for MCCPs), good linear range, and excellent repeatability (RPD < 18%), and can effectively overcome the interference of complex food matrices.
[0084] In summary, the method established in this study fully meets the requirements for the analysis and determination of trace SCCPs and MCCPs in pre-prepared foods and their packaging materials, and provides reliable technical support for assessing the dietary intake risk and human exposure level of chlorinated paraffins.
[0085] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.
Claims
1. A method for analyzing chlorinated paraffins in environmental or food samples using a two-dimensional gas chromatography-electron capture negative chemical ion source-quadrupole mass spectrometry technique, comprising the following steps: 1) The chlorinated paraffin components in environmental or food samples are enriched and extracted, and then further purified to obtain the sample to be tested; 2) The chlorinated paraffin in the test sample was detected by a two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry. 3) Characteristic ion extraction and retention time were used to obtain the response information of each component in the chlorinated paraffin; 4) Quantitative analysis of each component in the chlorinated paraffin was performed using a standard curve method based on chlorine content correction.
2. The method according to claim 1, characterized in that, The procedure for enriching, extracting, and further purifying chlorinated paraffin components from environmental or food samples to obtain the sample to be tested includes: The environmental or food sample was dried to constant weight and then ground to obtain sample powder; The chlorinated paraffin component in the sample powder was extracted using an accelerated extraction method to obtain an extract. The extract was concentrated, purified, further concentrated, and diluted to a fixed volume to obtain the sample to be tested.
3. The method according to claim 1, characterized in that, The procedure for detecting chlorinated paraffin in the sample using full two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry includes: The sample to be tested was injected into a full two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometer; The components of chlorinated paraffin in the sample were orthogonally separated using two columns of different polarities and a thermal modulator in a two-dimensional gas chromatography system. The samples were then ionized by an electron capture negative chemical ion source and detected by a quadrupole mass spectrometer to obtain a mass spectrum.
4. The method according to claim 1, characterized in that, The procedure for obtaining response information of each component in chlorinated paraffin using characteristic ion extraction and two-dimensional retention time includes: Qualitative analysis of the mass spectra was performed using dedicated two-dimensional chromatography-quadrupole mass spectrometry data processing software. The characteristic [M-Cl] components of the chlorinated paraffin were extracted within a preset characteristic mass number (m / z) window. - Ions are classified as qualitative and quantitative ions; The response area of each component of chlorinated paraffin in the test sample is obtained based on the retention time of each homologue group in the standard solution in the two-dimensional chromatographic space.
5. The method according to claim 1, characterized in that, The procedure for quantitative analysis of various components in chlorinated paraffin using a standard curve method based on chlorine content correction includes: Prepare chlorinated paraffin standard solutions with different chlorine contents, and add equal amounts of recovery internal standard and injection internal standard to the chlorinated paraffin standard solutions; The standard solution containing the internal standard was analyzed using the full two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry technique described above. Using feature [M-Cl] - Ion extraction and retention time were used to obtain the relative peak area and measured chlorine content between the chlorinated paraffin component and the internal standard in the standard solution. The relative response factor was obtained by combining the content of the chlorinated paraffin standard solution, and a standard curve was plotted. Based on the response area of each component of the chlorinated paraffin in the test sample and the measured chlorine content, combined with the linear equation of the standard curve, the response factor of the chlorinated paraffin in the test sample is obtained. The total content of chlorinated paraffin and the content of each component in the test sample were calculated based on the response factor of chlorinated paraffin in the test sample.
6. The method according to claim 2, characterized in that, The environmental or food samples include food samples and air sampling filters; The accelerated extraction method uses diatomaceous earth as the filling material in the extraction tank, and trans-chlordane is added to the extraction tank as an internal standard for recovery. The extraction solvent includes a mixture of dichloromethane and n-hexane. The accelerated extraction method has an extraction temperature of 100±5℃, a pressure of 10342±100 KPa, a heating time of 5±1 min, a static time of 10±2 min, a washing volume of 60%, and a purging time of 60±5 s.
7. The method according to claim 2, characterized in that, The operations of concentrating, purifying, re-concentrating, and adjusting the volume of the extract include: The extract was concentrated using a rotary evaporator and then transferred to a chromatography column for purification. The purified solution was then further concentrated using a rotary evaporator and a nitrogen blower. Hexachlorocyclohexane was added to the concentrated solution as an internal standard for injection, and the volume was adjusted with cyclohexane to obtain the sample to be tested.
8. The method according to claim 3, characterized in that, The conditions for the full two-dimensional gas chromatography-electron capture negative chemical ion source quadrupole mass spectrometry technique include: Column system: The first-dimensional column is a non-polar DB-5MS column; the second-dimensional column is a moderately polar BPX-50 column. Column temperature program: Initial temperature 100 ℃ held for 1 min, then increased to 140 ℃ at a rate of 10 ℃ / min, then increased to 310 ℃ at a rate of 1.5 ℃ / min and held for 5 min; Injection conditions: The injection method was splitless injection, the injection volume was 1.0 μL, and the injection port temperature was 280 ℃; Carrier gas conditions: The carrier gas is high-purity helium with a purity ≥99.999% and a constant flow rate of 0.8 mL / min; Modulation conditions: The modulator uses thermal modulation and the modulation period is 7 seconds; Mass spectrometry conditions: The ion source was an electron capture negative ionization (ECNI) source, the ion source temperature was 200 ℃, the transfer line temperature was 280 ℃, the reaction gas was methane, the mass acquisition range was 50–1200 m / z, the scanning mode was full scan or selected ion monitoring, and the mass resolution was unit mass resolution.
9. The method according to claim 5, characterized in that, The relative peak areas and measured chlorine content of each component in the chlorinated paraffin standard solution were calculated using the following strategy: First, chlorinated paraffin homologues with the same two-dimensional retention time characteristics in the mass spectrum are divided into several homologue groups, and the peak area of each group is calculated. Relative response value of chlorinated paraffin homologues = Peak area of chlorinated paraffin homologues ÷ Peak area of recovered internal standard; The measured chlorine content of a chlorinated paraffin sample = Σ(peak area of each homologue group × theoretical chlorine content of that group) ÷ Σ(peak area of each homologue group); The relative response values of each homologue of the chlorinated paraffin are summed to obtain the total relative response value. The total response factor of the standard solution is then calculated using the following formula: Total response factor of chlorinated paraffin = Total relative response value of chlorinated paraffin ÷ Total concentration of chlorinated paraffin standard solution; Using the total response factor of the chlorinated paraffin as the ordinate and the measured chlorine content of the chlorinated paraffin as the abscissa, a linear fit is performed to obtain the chlorine content correction standard curve.
10. The method according to claim 1, wherein, The components of the chlorinated paraffin include C n H 2n+2-m Cl m ; Where n represents the number of carbon atoms, which is an integer from 10 to 17; m represents the number of chlorine atoms, which is an integer from 5 to n.