Analysis method for simultaneously detecting organochlorine pesticide and polychlorinated biphenyl

Abstract

The invention discloses an analysis method for simultaneously detecting organochlorine pesticide and polychlorinated biphenyl, which comprises the following steps of: simultaneously extracting organochlorine pesticide and polychlorinated biphenyl in a water sample by adopting a mixed extraction solvent, dehydrating, concentrating and fixing the volume of extract liquor, separating and measuring by adopting a gas chromatography-mass spectrometry method, and quantifying by adopting an internal standard method. When the mixed extraction solvent is n-hexane / dichloromethane with the volume ratio of 9: 1 and 1% by mass of polyethylene glycol 4000 is added, the recovery rates of water samples with the measured concentrations of 5.00 ng / L, 20.0 ng / L, 40.0 ng / L and 80.0 ng / L are 83.6%-95.4%, 91.2%-105.6%, 93.5%-104.7% and 92.8%-106.9% respectively, the relative standard deviations are 6.1%-9.2%, 3.3%-8.2%, 3.2%-6.3% and 3.4%-7.5% respectively, compared with the prior art, the extraction efficiency is remarkably improved, and the method has the advantages that the method is simple, the cost is low, and the method is suitable for industrial production. The accuracy and precision of the method completely meet the determination and analysis requirements for measuring complex water samples.

Description

Technical Field

[0001] The invention belongs to the field of analysis and detection, and particularly relates to an analysis method for simultaneously detecting organochlorine pesticides and polychlorinated biphenyls. Summary of the Invention

[0002] Residues of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in aquatic environments are of growing global concern. These substances are highly toxic, have long half-lives, are difficult to degrade, and are bioaccumulative. They readily enter the food chain and persist in sediments, water, and organisms for long periods of time. Accumulating through the food chain, they can adversely impact human health and the environment. In today's large-scale environmental surveys and monitoring missions, large numbers of samples are collected. Organic pollutants are unstable due to their volatility and biodegradability. Therefore, their analysis requires particular attention to timeliness: water sample pretreatment should be completed within 7-14 days of collection, and analysis should be completed within 40 days. Currently, the main methods for detecting OCPs and PCBs in the environment include gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS), and gas chromatography-tandem mass spectrometry (GC-MS / MS). However, standard analytical methods for PCBs and OCPs, both domestically and internationally, primarily involve extraction, cleanup, and determination of each separately. These methods not only have long analysis cycles, impacting the timeliness of sample testing, but also have high laboratory costs, increasing testing costs and making it difficult to meet the growing demand for analytical testing of environmental monitoring samples. Peng Jie et al. reported the simultaneous determination of polychlorinated biphenyls (PCBs) and organochlorine pesticide residues in water and sludge using gas chromatography-tandem mass spectrometry. Using different extraction solvents, including n-hexane, dichloromethane, and dichloromethane-n-hexane (1:1, v / v), the water samples were extracted. The extraction efficiency of some compounds, such as hexachlorobenzene, was only approximately 70%, indicating that this efficiency needs to be improved. Therefore, there is an urgent need to improve the determination of persistent organic pollutants (POPs) such as PCBs and OCPs in environmental samples. The development of rapid, simultaneous, and efficient sample pretreatment and instrumental integration techniques to improve pretreatment extraction efficiency and the accuracy of analytical data is of great practical significance. Summary of the Invention

[0003] In view of the problems existing in the prior art, such as separate extraction, purification and determination, which leads to a long analysis cycle and affects the timeliness of sample testing, and has high experimental consumption and increased testing costs, and the simultaneous extraction and analysis of two substances has low extraction efficiency for some test items, the present invention provides an analytical method for simultaneously detecting organochlorine pesticides and polychlorinated biphenyls. The analytical method adopts a mixed extraction solvent to simultaneously extract organochlorine pesticides and polychlorinated biphenyls in water samples, and has good analytical effect.

[0004] The technical solution of the present invention is an analytical method for simultaneously extracting organochlorine pesticides and polychlorinated biphenyls in a water sample using a mixed extraction solvent. The extract is dehydrated, concentrated and fixed to volume, and then separated and determined by gas chromatography-mass spectrometry. Qualitative analysis is performed based on retention time, fragment ion mass-to-charge ratio and different ion abundance ratios, and quantitative analysis is performed using an internal standard method. The mixed extraction solvent is selected from: n-hexane, dichloromethane or a mixed solvent of the two.

[0005] Preferably, the mixed extraction solvent is selected from: a mixed solvent of n-hexane and dichloromethane.

[0006] Preferably, the volume ratio of the mixed extraction solvent of n-hexane and dichloromethane is 9:1.

[0007] Preferably, the mixed extraction solvent further comprises polyethylene glycol, wherein the polyethylene glycol is selected from polyethylene glycol 2000, polyethylene glycol 3500 or polyethylene glycol 4000.

[0008] Preferably, the polyethylene glycol is polyethylene glycol 4000, and the added amount is 1% to 10% of the mass of the mixed extraction solvent.

[0009] Preferably, the amount of polyethylene glycol 4000 added is 1% by mass of the mixed extraction solvent.

[0010] The specific steps of the analytical method of the present invention are as follows:

[0011] Chromatographic conditions: Inlet: 300°C, splitless injection, injection volume 1uL; column flow rate 1.0mL / min, constant flow, column temperature 100°C maintained for 6min, increased at 20°C / min to 260°C, maintained for 0min, then increased at 5°C / min to 300°C and maintained for 13min, for a total run time of 35min; mass spectrometry conditions: SIM scan; ion source (EI) 300°C; quadrupole 200°C; solvent delay 15min, interface temperature 300°C; carrier gas is helium.

[0012] (1) Pretreatment: Take 1000 mL of water sample in a separatory funnel, add 10 ng of the substitute, then add 20-30 g of sodium chloride, shake until completely dissolved, extract the water sample with 30-50 mL of mixed extraction solvent, let it stand and separate the liquid, then add 30-50 mL of mixed extraction solvent and repeat the extraction 2-3 times, combine the two extracts, dehydrate with anhydrous sodium sulfate, and concentrate to 1.0 mL using a multi-sample parallel quantitative concentrator, add 20 ng of the internal standard, mix the concentrate thoroughly, and finally transfer it to a sample bottle for storage. Clean water does not require additional purification treatment, but wastewater needs to be treated with C 18 Cartridge cleanup.

[0013] (2) Drawing of calibration curve: Prepare a series of standard solutions containing 13 organochlorine pesticides, 9 polychlorinated biphenyls and 2 substitutes using a 5 mL volumetric flask. The concentrations of the standard solutions are 2.00 μg / L, 5.00 μg / L, 10.0 μg / L, 20.0 μg / L, 50.0 μg / L and 100 μg / L respectively. Add 20 μL of 1000 μg / L internal standard solution to make the concentration of each solution 20.0 μg / L. Analyze under the instrument reference conditions to obtain mass spectra of each target compound at different concentrations. Draw the calibration curve with the ratio of the target compound quantitative ion response to the internal standard compound quantitative ion response as the horizontal axis and the ratio of the target compound to the internal standard compound concentration as the vertical axis.

[0014] (3) Sample determination: The treated water sample is measured under the same instrument analysis conditions as those used to draw the calibration curve, and the measurement results are calculated.

[0015] Compared with the prior art, the present invention has achieved beneficial effects in that it can simultaneously extract, purify and determine organochlorine pesticides and polychlorinated biphenyls. The extraction efficiency is significantly improved compared with the prior art by using a mixed extraction solvent. The precision and accuracy of the method fully meet the requirements of existing environmental monitoring. The specific beneficial effects are shown in the experimental results:

[0016] (1) When the extraction solvent is n-hexane, the extraction recovery rate is 77.8%-103%. The extraction efficiency of dichloromethane is the worst, with an extraction recovery rate of 45.6%-89.6%. When the extraction solvent is a mixed solvent of dichloromethane and n-hexane, the extraction efficiency gradually increases with the increase of the proportion of n-hexane. When the volume ratio of n-hexane to dichloromethane is 9:1, the extraction recovery rate can reach 78.9%-95.7%. When 1% polyethylene glycol 4000 is added to the mixed extraction with a volume ratio of n-hexane to dichloromethane of 9:1, the extraction efficiency is significantly improved, and the extraction efficiency recovery rate reaches 84.6%-103%, indicating that the addition of polyethylene glycol 4000 has a significant improvement effect.

[0017] (2) When 0.5% by mass of polyethylene glycol 4000 was added to the mixed extraction solvent, the extraction effect did not change significantly. When 1% by mass of polyethylene glycol 4000 was added, the extraction efficiency was significantly improved. As the mass increased, the extraction efficiency decreased slightly.

[0018] (3) When polyethylene glycol is a low molecular weight polymer, the extraction effect becomes worse. This may be because low molecular weight polyethylene glycol has a strong affinity for water, which dissolves a certain amount of extracted pollutants in water, resulting in a decrease in extraction efficiency. When the molecular weight gradually increases, the extraction efficiency gradually increases. When the molecular weight increases to 2000, the extraction efficiency is improved compared with the 9:1 ratio of pure hexane and dichloromethane. Among them, the extraction efficiency is the highest when polyethylene glycol 4000 is added.

[0019] (4) Using the parameters of the present invention, the correlation coefficients of 13 organochlorine pesticides and 9 polychlorinated biphenyls of the present invention are greater than 0.997, the linear range is mostly 1-100 ng / L, and the detection limit is between 0.45 ng / L and 0.92 ng / L, which fully meets the requirements of existing standards.

[0020] (5) When the mixed extraction solvent was n-hexane / dichloromethane with a volume ratio of 9:1 and 1% of polyethylene glycol 4000 was added, the recoveries of 13 organochlorine pesticides and 9 polychlorinated biphenyl compounds in water samples with concentrations of 5.00 ng / L, 20.0 ng / L, 40.0 ng / L and 80.0 ng / L were measured in parallel for 6 times and were 83.6-95.4%, 91.2-105.6%, 93.5-104.7% and 92.8-106.9%, respectively, indicating that the accuracy of the method was good; the relative standard deviations were 6.1%-9.2%, 3.3%-8.2%, 3.2%-6.3% and 3.4%-7.5%, respectively, indicating that the precision of the method was good.

[0021] (7) When analyzing actual sewage samples from sewage treatment plants, the test results showed that both organochlorine pesticides and polychlorinated biphenyls were detected, which fully met the requirements for measuring and analyzing complex water samples. The recovery rate of the surrogate decachlorobiphenyl was between 83.7% and 106%. The results showed that the accuracy of the test results fully met the requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 : Chromatograms of 26 organochlorine pesticides and polychlorinated biphenyls. Specific implementation methods

[0023] Various exemplary embodiments of the present invention are now described in detail. Unless otherwise specified, the methods in the examples are conventional methods. Unless otherwise specified, the reagents used are conventional commercially available reagents or reagents prepared using conventional methods. This detailed description should not be considered a limitation of the present invention, but rather should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0025] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0026] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0027] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0028] Example 1

[0029] 1. Preparation of samples

[0030] Take 1000mL of water sample and place it in a 2000mL separating funnel. Add 10ng of substitute: concentration: 1000μg / L, amount added: 10μL, then add 20g of sodium chloride, shake until completely dissolved, extract the water sample with 30mL of n-hexane, let it stand and separate the liquid, then add 30mL of n-hexane and repeat the extraction twice. Combine the two extracts, dehydrate with anhydrous sodium sulfate, and concentrate to about 1mL using a multi-sample parallel quantitative concentrator. Add 20ng of internal standard: concentration: 1000μg / L, amount added: 20μL, mix the concentrate thoroughly, and finally transfer it to a sample bottle for storage.

[0031] 2. Instrument conditions

[0032] 2.1. Chromatographic Conditions: Injection: 300°C, splitless injection, 1 μL injection volume; column flow rate 1.0 mL / min, constant flow. Column temperature was maintained at 100°C for 6 min, then increased at 20°C / min to 260°C and held for 0 min, then increased at 5°C / min to 300°C and held for 13 min, for a total run time of 35 min.

[0033] Mass spectrometry conditions: SIM scan; EI ion source at 300°C; quadrupole at 200°C; solvent delay 15 min; interface temperature 300°C; helium carrier gas.

[0034] 3. Drawing of calibration curve

[0035] A series of standard solutions containing 13 organochlorine pesticides, 9 polychlorinated biphenyls, and 2 surrogate compounds were prepared using 5mL volumetric flasks. The concentrations of the standard series were 2.00μg / L, 5.00μg / L, 10.0μg / L, 20.0μg / L, 50.0μg / L, and 100μg / L, respectively. 20μL of 1000μg / L internal standard solution was added to each solution to bring the concentration to 20.0μg / L. Analysis was performed under instrument reference conditions to obtain mass spectra of each target compound at different concentrations. A calibration curve was plotted with the ratio of the target compound to the internal standard compound concentration as the horizontal axis and the ratio of the target compound quantification ion response to the internal standard compound quantification ion response as the vertical axis.

[0036] Table 1 Calibration curves of 13 organochlorine pesticides, 9 polychlorinated biphenyls, and 2 surrogates

[0037]

[0038]

[0039] 4. Sample determination

[0040] The treated water samples were measured under the same instrument analysis conditions as those used to draw the calibration curve.

[0041] 5. Result calculation and presentation

[0042] 5.1 Qualitative analysis

[0043] Data was collected in full scan mode, and qualitative analysis was performed based on the relative retention time (RRT) of the target compound in the sample and the abundance ratio of the auxiliary qualifier ion to the target ion (Q) compared to that in the standard solution. The difference between the relative retention time of the target compound in the sample and the average relative retention time of the compound in the calibration curve should be within ±0.06. The relative deviation of the peak area ratio of the auxiliary qualifier ion and quantifier ion of the target compound in the sample (Q sample) and the peak area ratio of the auxiliary qualifier ion and quantifier ion of the target compound in the standard curve (Q standard) was controlled within ±30%.

[0044] 5.2 Quantitative analysis

[0045] Data were collected using the selected ion scanning (SIM) method and quantified using the internal standard method. The mass concentration of the target compound in the sample, ρi (ng / L), was calculated according to formula (1).

[0046]

[0047] Where: ρi—concentration of PAH compounds or surrogates in the sample, ng / L;

[0048] ρis—the concentration of PAHs or their surrogates according to the standard curve, μg / L;

[0049] V—sample volume, mL;

[0050] Vs—water sample volume, mL.

[0051] Example 2

[0052] 1. Sample preparation: blank sample spiked and extracted

[0053] Take 1000mL of blank sample and place it in a 2000mL separating funnel. Add 10ng of mixed standard solution and substitute each: concentration 1000μg / L, addition volume 10μL, then add 20g of sodium chloride, shake until completely dissolved, extract the water sample with 30mL of different mixed extraction solvents, let it stand and separate the liquid, then add 30mL of extraction solvent and repeat the extraction twice. After combining the extracts, dehydrate with anhydrous sodium sulfate, concentrate to about 1mL using a multi-sample parallel quantitative concentrator, add 20ng of internal standard with concentration: 1000μg / L, addition volume: 20μL, mix the concentrate thoroughly, and finally transfer it to a sample bottle for storage and test, and test the blank sample simultaneously.

[0054] 2. Instrument conditions

[0055] Chromatographic conditions: Column: HP-5ms: 60m x 0.25mm x 0.25μm; Injection port: 300°C, splitless injection, 1 μL injection volume; Column flow rate: 1.0 mL / min, constant flow. Column temperature: 100°C, held for 6 min, then increased at 20°C / min to 260°C, held for 0 min, then increased at 5°C / min to 300°C, held for 13 min, for a total run time of 35 min.

[0056] Mass spectrometry conditions were as follows: SIM scanning; EI ion source at 300°C; quadrupole at 200°C; solvent delay of 15 min, interface temperature of 300°C; and helium as carrier gas.

[0057] 3. Selection of extraction reagents:

[0058] n-Hexane, dichloromethane, n-hexane / dichloromethane volume ratio of 3:1, 5:1, 9:1 and n-hexane + dichloromethane volume ratio of 9:1 + polyethylene glycol 4000 (the amount added is 1% of the mass of n-hexane and dichloromethane), the experimental results are shown in Table 2 below:

[0059] Table 2 Recovery rates of extractions with different extraction solvents

[0060]

[0061] The results show that when the extraction solvent is n-hexane, the extraction recovery rate is 77.8%-103%, the extraction efficiency of dichloromethane is the worst, with an extraction recovery rate of 45.6%-89.6%, and when the extraction solvent is a mixed solvent of dichloromethane and n-hexane, the extraction efficiency gradually increases with the increase of the proportion of n-hexane. When the volume ratio of n-hexane to dichloromethane is 9:1, the extraction recovery rate can reach 78.9%-95.7%. When 1% polyethylene glycol 4000 is added to the mixed extraction with a volume ratio of n-hexane to dichloromethane of 9:1, the extraction efficiency is significantly improved, and the extraction efficiency recovery rate reaches 84.6%-103%, indicating that the addition of polyethylene glycol 4000 has an improving effect.

[0062] Example 3

[0063] 1. Preparation of samples

[0064] Take 1000mL of blank sample in a 2000mL separatory funnel, add 10ng of mixed standard solution and surrogate each (1000μg / L×10μL), then add 20g of sodium chloride, shake until completely dissolved, and extract the water sample with 30mL of mixed extraction solvent (n-hexane + dichloromethane 9:1) and 1-10% mass of polyethylene glycol 4000. After standing, separate the liquid, add 30mL of the same mixed extraction solvent as the first time and repeat the extraction twice. After combining the extracts, dehydrate with anhydrous sodium sulfate and concentrate to about 1mL using a multi-sample parallel quantitative concentrator. Add 20ng of internal standard, concentration: 1000μg / L, addition volume: 20μL, mix the concentrate thoroughly, and finally transfer it to a sample bottle for testing. Test the blank sample simultaneously.

[0065] 2. Instrument conditions

[0066] Chromatographic conditions: Column: HP-5ms: 60m x 0.25mm x 0.25μm; Injection port: 300°C, splitless injection, 1 μL injection volume; Column flow rate: 1.0 mL / min, constant flow. Column temperature: 100°C, held for 6 min, then increased at 20°C / min to 260°C, held for 0 min, then increased at 5°C / min to 300°C, held for 13 min, for a total run time of 35 min.

[0067] Mass spectrometry conditions were as follows: SIM scanning; EI ion source at 300°C; quadrupole at 200°C; solvent delay of 15 min, interface temperature of 300°C; and helium as carrier gas.

[0068] 3. Selection of mixed extractant:

[0069] The volume ratio of n-hexane to dichloromethane was 9:1, and 0.5-10% of the weight of polyethylene glycol 4000 was added to the extraction mixed solvent. The experimental results are shown in Table 3 below:

[0070] Table 3 Extraction results with different amounts of polyethylene glycol 4000

[0071]

[0072] The experimental results show that when 0.5% by mass of polyethylene glycol 4000 is added to the mixed extraction solvent, the extraction effect has no obvious change. When 1% by mass of polyethylene glycol 4000 is added, the extraction efficiency is significantly improved. As the mass increases, the extraction efficiency decreases slightly.

[0073] Example 4

[0074] 1. Preparation of samples

[0075] Take 1000mL of blank sample in a 2000mL separatory funnel, add 10ng of mixed standard solution and substitute (1000μg / L×10μL), then add 20g of sodium chloride, shake until completely dissolved, and extract the water sample with 30mL of mixed extraction solvent (n-hexane + dichloromethane 9:1) and 1% of various polyethylene glycols by mass. After standing, separate the liquid, add 30mL of the same mixed extraction solvent as the first time and repeat the extraction twice. After combining the extracts, dehydrate with anhydrous sodium sulfate and concentrate to about 1mL using a multi-sample parallel quantitative concentrator. Add 20ng of internal standard, concentration: 1000μg / L, addition volume: 20μL, mix the concentrate thoroughly, and finally transfer it to a sample bottle for testing. Test the blank sample simultaneously.

[0076] 2. Instrument conditions

[0077] Chromatographic conditions: Column: HP-5ms: 60m x 0.25mm x 0.25μm; Injection port: 300°C, splitless injection, 1 μL injection volume; Column flow rate: 1.0 mL / min, constant flow. Column temperature: 100°C, held for 6 min, then increased at 20°C / min to 260°C, held for 0 min, then increased at 5°C / min to 300°C, held for 13 min, for a total run time of 35 min.

[0078] Mass spectrometry conditions were as follows: SIM scanning; EI ion source at 300°C; quadrupole at 200°C; solvent delay of 15 min, interface temperature of 300°C; and helium as carrier gas.

[0079] 3. Selection of mixed extractant:

[0080] The volume ratio of n-hexane to dichloromethane was 9:1, and 1% by weight of polyethylene glycol was added to the extraction mixed solvent, wherein the polyethylene glycol was selected from polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 1000, polyethylene glycol 1500, polyethylene glycol 2000, polyethylene glycol 3500 and polyethylene glycol 4000. The experimental results are shown in Table 4 below:

[0081] Table 4 Extraction results with different polyethylene glycol additions

[0082]

[0083]

[0084] The experimental results show that when the polyethylene glycol is a low molecular weight polymer, the extraction effect becomes worse. This may be because the low molecular weight polyethylene glycol has a strong affinity for water, dissolving a certain amount of extracted pollutants in water, resulting in a decrease in extraction efficiency. When the molecular weight gradually increases, the extraction efficiency gradually improves. When the molecular weight increases to 2000, the extraction efficiency is improved compared with the 9:1 ratio of pure hexane and dichloromethane. Among them, the extraction efficiency is the highest when polyethylene glycol 4000 is added.

[0085] Example 5

[0086] 1. Preparation of samples

[0087] Using 1000 mL of pure water as a blank, 5.0 μL of a mixed standard solution of 13 organochlorine pesticides and 9 polychlorinated biphenyls at 1000 μg / L (the spiked water sample concentration was 5 ng / L) was added. Seven spiked samples were analyzed according to the above water sample preparation and analytical methods. The detection limit and determination limit of the method were calculated with reference to the "Technical Guidelines for the Development of Environmental Monitoring Analytical Method Standards" (HJ 168-2020). Sample pretreatment was as follows: the water sample was extracted with a mixed extraction solvent of 9:1 hexane and dichloromethane and 1% polyethylene glycol 4000. After standing, the liquid was separated and the extraction was repeated twice with 30 mL of the same mixed extraction solvent. The combined extracts were dehydrated with anhydrous sodium sulfate and concentrated to approximately 1 mL using a multi-sample parallel quantitative concentrator. 20 ng of internal standard was added at a concentration of 1000 μg / L (20 μL). The concentrate was thoroughly mixed and finally transferred to a sample bottle for storage. A blank sample was also tested simultaneously.

[0088] 2. Instrument conditions

[0089] Chromatographic conditions: Column: HP-5ms: 60m x 0.25mm x 0.25μm; Injection port: 300°C, splitless injection, 1 μL injection volume; Column flow rate: 1.0 mL / min, constant flow. Column temperature: 100°C, held for 6 min, then increased at 20°C / min to 260°C, held for 0 min, then increased at 5°C / min to 300°C, held for 13 min, for a total run time of 35 min.

[0090] Mass spectrometry conditions were as follows: SIM scanning; EI ion source at 300°C; quadrupole at 200°C; solvent delay of 15 min, interface temperature of 300°C; and helium as carrier gas.

[0091] The determination results including correlation coefficient R, linear range and detection limit are shown in Table 5 below:

[0092] Table 5 Correlation coefficient R, linear range and detection limit results

[0093]

[0094]

[0095] The experimental results show that the correlation coefficient is greater than 0.997, the linear range is mostly 1-100 ng / L, and the detection limit is between 0.45 ng / L and 0.92 ng / L, which fully meets the requirements of existing standards.

[0096] Example 6

[0097] 1. Preparation of samples

[0098] Water samples at 5.00 ng / L, 20.0 ng / L, 40.0 ng / L, and 80.0 ng / L were measured six times at each concentration, and the RSD was calculated. Method precision data were calculated with reference to the "Technical Guidelines for the Development of Environmental Monitoring Analytical Method Standards" (HJ 168-2020). The accuracy and precision of the method were calculated using the results of parallel measurements of water samples at three concentration gradients, referring to the "Technical Guidelines for the Development of Environmental Monitoring Analytical Method Standards" (HJ 168-2020). The sample pretreatment is as follows: extract the water sample with a mixed extraction solvent: n-hexane + dichloromethane 9:1 and 1% polyethylene glycol 4000 by mass, let it stand and separate the liquids, then add 30 mL of the same mixed extraction solvent as the first time and repeat the extraction twice. After combining the extracts, dehydrate with anhydrous sodium sulfate and concentrate to about 1 mL using a multi-sample parallel quantitative concentrator. Add 20 ng of internal standard at a concentration of 1000 μg / L in an amount of 20 μL, mix the concentrate thoroughly, and finally transfer it to a sample bottle for storage before testing. Simultaneously test the blank sample.

[0099] 2. Instrument conditions

[0100] Chromatographic conditions: Column: HP-5ms: 60m x 0.25mm x 0.25μm; Injection port: 300°C, splitless injection, 1 μL injection volume; Column flow rate: 1.0 mL / min, constant flow. Column temperature: 100°C, held for 6 min, then increased at 20°C / min to 260°C, held for 0 min, then increased at 5°C / min to 300°C, held for 13 min, for a total run time of 35 min.

[0101] Mass spectrometry conditions were as follows: SIM scanning; EI ion source at 300°C; quadrupole at 200°C; solvent delay of 15 min, interface temperature of 300°C; and helium as carrier gas.

[0102] Table 6 Accuracy and precision data of samples at various concentrations

[0103]

[0104] The experimental results showed that the recoveries of 13 organochlorine pesticides and 9 polychlorinated biphenyl compounds in water samples with concentrations of 5.00 ng / L, 20.0 ng / L, 40.0 ng / L and 80.0 ng / L in parallel were 83.6-95.4%, 91.2-105.6%, 93.5-104.7% and 92.8-106.9%, respectively, indicating that the method had good accuracy; the relative standard deviations were 6.1%-9.2%, 3.3%-8.2%, 3.2%-6.3% and 3.4%-7.5%, respectively, indicating that the method had good precision.

[0105] Example 7

[0106] 1. Pretreatment of sewage samples

[0107] The laboratory tested the influent samples from the sewage treatment plant. 1000mL of sample was placed in a 2000mL separatory funnel. 10ng of the mixed standard solution and 10ng of the surrogate (1000μg / L×10μL) were added. 20g of sodium chloride was then added and shaken until completely dissolved. 30mL of extraction solvent (n-hexane + dichloromethane 9:1) was then used to extract the water sample. About 1% polyethylene glycol 4000 was added to the mixed extraction solvent. After standing, the liquid was separated and 30mL of the same mixed extraction solvent was added. The extraction was repeated twice. After the combined extracts were dehydrated with anhydrous sodium sulfate, the extracts were concentrated to about 1mL using a multi-sample parallel quantitative concentrator. 20ng of the internal standard (1000μg / L×20μL) was added and the concentrate was thoroughly mixed. Finally, the concentrate was transferred to a sample bottle for storage and a blank sample was tested simultaneously. The results of the sewage sample test are shown in Table 7:

[0108] 2. Instrument Conditions: Chromatographic conditions: Chromatographic column: HP-5ms (60m*0.25mm*0.25μm), Injection port: 300°C, splitless injection, injection volume: 1uL; Column flow rate: 1.0mL / min, constant flow. Column temperature: 100°C, maintained for 6 minutes, then increased at 20°C / min to 260°C (260°C for 0 minutes), then increased at 5°C / min to 300°C and held for 13 minutes, for a total run time of 35 minutes.

[0109] Mass spectrometry conditions were as follows: SIM scanning; ion source (EI) at 300°C; quadrupole at 200°C; solvent delay of 15 min, interface temperature of 300°C; and helium as carrier gas.

[0110] Table 7 Determination of actual sewage samples

[0111]

[0112]

[0113] Experimental data show that the sewage test results of the sewage treatment plant show that both organochlorine pesticides and polychlorinated biphenyls were detected, which fully meets the measurement and analysis requirements of complex water samples. The recovery rate of the substitute decachlorobiphenyl is between 83.7% and 106%. The results show that the accuracy of the results fully meets the requirements.

Claims

1. An analytical method for the simultaneous detection of organochlorine pesticides and polychlorinated biphenyls, characterized in that: A mixed extraction solvent is used to simultaneously extract organochlorine pesticides and polychlorinated biphenyls in water samples. The extract is dehydrated, concentrated and fixed to volume, and then separated and determined by gas chromatography-mass spectrometry. Qualitative analysis is based on retention time, mass-to-charge ratio of fragment ions and abundance ratio of different ions, and quantitative analysis is performed using an internal standard method. The mixed extraction solvent is selected from: n-hexane, dichloromethane or a mixed solvent of the two.

2. The analytical method for simultaneous detection of organochlorine pesticides and polychlorinated biphenyls according to claim 1, characterized in that: The mixed extraction solvent is selected from: a mixed solvent of n-hexane and dichloromethane.

3. The analytical method for simultaneous detection of organochlorine pesticides and polychlorinated biphenyls according to claim 2, characterized in that: The volume ratio of the mixed solvent of n-hexane and dichloromethane is 9:

1.

4. The analytical method for simultaneous detection of organochlorine pesticides and polychlorinated biphenyls according to claim 1, characterized in that: The mixed extraction solvent further comprises polyethylene glycol, wherein the polyethylene glycol is selected from polyethylene glycol 2000, polyethylene glycol 3500 or polyethylene glycol 4000.

5. The analytical method for simultaneous detection of organochlorine pesticides and polychlorinated biphenyls according to claim 4, characterized in that: The polyethylene glycol is polyethylene glycol 4000, and the added amount is 0.5% to 10% of the mass of the extraction solvent.

6. The analytical method for simultaneous detection of organochlorine pesticides and polychlorinated biphenyls according to claim 5, characterized in that: The amount of polyethylene glycol 4000 added is 1% of the mass of the extraction solvent.

7. An analytical method for simultaneous detection of organochlorine pesticides and polychlorinated biphenyls according to claims 1 to 6, characterized in that: The specific steps of the analysis method are as follows: Chromatographic conditions: Inlet: 300°C, splitless injection, injection volume 1uL; column flow rate 1.0 mL / min, constant flow, column temperature 100°C maintained for 6 min, increased at 20°C / min to 260°C, maintained for 0 min, then increased to 300°C at 5°C / min and maintained for 13 min, for a total run time of 35 min; mass spectrometry conditions: SIM scan; EI ion source 300°C; quadrupole 200°C; solvent delay 15 min, interface temperature 300°C; carrier gas is helium. (1) Pretreatment: Take 1000 mL of water sample in a separatory funnel, add 10 ng of the substitute, then add 20-30 g of sodium chloride, shake until completely dissolved, extract the water sample with 20-50 mL of mixed extraction solvent, let it stand and separate, then add 20-50 mL of mixed extraction solvent and repeat the extraction 2-3 times, combine the two extracts, dehydrate with anhydrous sodium sulfate, and concentrate to 0.5-2.0 mL using a multi-sample parallel quantitative concentrator, add 20 ng of the internal standard, mix the concentrate thoroughly, and finally transfer it to a sample bottle for storage; (2) Calibration curve drawing: A series of standard solutions containing 13 organochlorine pesticides, 9 polychlorinated biphenyls, and 2 surrogates were prepared using 5 mL volumetric flasks. The concentrations of the standard solutions were 2.00 μg / L, 5.00 μg / L, 10.0 μg / L, 20.0 μg / L, 50.0 μg / L, and 100 μg / L, respectively. 20 μL of 1000 μg / L internal standard solution was added to each solution to make the concentration of each solution 20.0 μg / L. The samples were analyzed under the above-mentioned instrument reference conditions to obtain mass spectra of the target compounds at different concentrations. Draw a calibration curve with the ratio of the response value of the quantitative ion of the target compound to the response value of the quantitative ion of the internal standard compound as the horizontal axis and the ratio of the concentration of the target compound to the internal standard compound as the vertical axis; (3) Sample determination: The treated water sample is measured under the same instrument analysis conditions as those used to draw the calibration curve, and the measurement results are calculated.

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