A method for quickly and accurately determining the content of organochlorine pesticides in water

Abstract

The invention discloses a method for quickly and accurately determining the content of organochlorine pesticides in water, which belongs to the field of determination of organochlorine pesticide content, and comprises the following steps: adding a regulator to a water sample and shaking it well, and shaking it well again after adding a substitute; adding sodium chloride to the water sample treated in step S1, and placing it in a liquid-liquid extraction oscillator to shake until it is completely dissolved; adding an extractant to the water sample treated in step S2, standing and stratifying after vigorous shaking, lower water sample is placed in a reagent bottle, and the upper extract is transferred to a drying column elution water and then moved into a concentration bottle; the remaining water sample in step S3 is executed again once; the eluents of steps S3 and S4 are combined, moved into a fully automatic nitrogen blowing instrument and concentrated to 1 ml, an internal standard solution is added, and a gas chromatography-mass spectrometer is analyzed after constant volume to obtain the content of organochlorine pesticides in the water sample. The invention has the beneficial effects of: having the advantages of high efficiency, rapidness and accurate detection, and the method is simple to operate, low cost, high concentration efficiency and recovery stability.

Description

Technical Field

[0001] The present invention relates to the technical field of the determination of the content of organochlorine pesticides in water, and in particular to a method for quickly and accurately determining the content of organochlorine pesticides in water. Background Art

[0002] Organochlorine pesticides (OCPs), including: alpha-HCH, beta-HCH, gamma-HCH, delta-HCH. Most organochlorine pesticides are white or light yellow crystals or solids, insoluble or slightly soluble in water, soluble in fats and most organic solvents, with low volatility, stable chemical properties, high affinity for enzymes and proteins, and extremely strong enrichment in organisms; Organochlorine pesticides are environmental pollutants that play a significant role in preventing and controlling pests and diseases, widely exist in the environment, and belong to one of the persistent organic pollutants (POPS).

[0003] Although China and most countries in the world have stopped producing and using highly toxic OCPs, the long-term and large-scale use in the past has made OCPs still transform and remain in the environment for a quite long time. The toxicity and residues of organochlorine pesticides pose great harm to the ecosystem and human health. In the analysis of environmental samples, the content of HCH is relatively low. Therefore, the pretreatment method is an important step in the whole analysis process, which affects the accuracy and reliability of the determination results. At present, common pretreatment methods for organochlorine pesticides in water environmental samples include liquid-liquid extraction, solid-phase extraction, solid-phase microextraction, etc. The liquid-liquid extraction pretreatment method has the advantages of short time consumption (6 samples per batch, 2.5 hours per batch of samples), high enrichment efficiency, and high target recovery rate (more than 95%), and is especially suitable for the analysis of multi-residue components of large batches of samples; The solid-phase extraction pretreatment method has the disadvantages of long extraction time (6 samples per batch, 4 hours per batch of samples), large loss of analytes, and low recovery rate (the recovery rate of tetrachloro-m-xylene is only 30%, and the recovery rate of the target is about 80%); The solid-phase microextraction pretreatment method still has limitations in actual application, such as poor stability of organic droplets, generation of bubbles, poor reproducibility, long extraction time, and high use cost; Concentration methods include traditional slow drying with inert gas, rotary evaporation, high-throughput vacuum parallel concentration, etc. Among them, the methods of rotary evaporation and slow drying with inert gas are very convenient for a small number of samples or small solvent volumes. When a large number of samples need to be concentrated simultaneously and the solvent volume is large, it is time-consuming (it takes 1 hour to concentrate 10 ml of n-hexane to about 1 ml), laborious (it needs to be watched to prevent drying), and the open nitrogen blowing device is extremely harmful to the health of operators; High-throughput vacuum parallel concentration is greatly affected by water bath temperature, rotation speed, vacuum degree, and type of solvent. It can be seen from the above that the existing determination methods have disadvantages such as long processing time and low target recovery rate. Summary of the Invention

[0004] The object of the present invention is to provide a method for quickly and accurately determining the content of organochlorine pesticides in water, which has the advantages of rapidity, high efficiency and accuracy in determination, effectively solves the problems of low recovery rate and too long detection time in the current detection and analysis of such substances, and provides technical assistance for "precision pollution control".

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] A method for quickly and accurately determining the content of organochlorine pesticides in water, comprising the following treatment steps:

[0007] S1. Add a regulator to the water sample and shake well, and then shake well again after adding a surrogate;

[0008] S2. Add sodium chloride to the water sample treated in step S1, and place it in a liquid-liquid extraction oscillator and shake until completely dissolved;

[0009] S3. Add an extractant to the water sample treated in step S2, shake vigorously and then let it stand for layer separation. The lower-layer water sample is placed in a reagent bottle, and the upper-layer extract is transferred to a drying column for dehydration and then moved into a concentration bottle;

[0010] S4. Perform step S3 again on the remaining water sample in step S3;

[0011] S5. Combine the eluents in steps S3 and S4, transfer them into an automatic nitrogen blowing instrument for concentration to 1 ml, add an internal standard solution, fix the volume and then perform gas chromatography-mass spectrometry analysis to obtain the content of organochlorine pesticides in the water sample.

[0012] The experimental analysis time of conventional organochlorine pesticides is relatively long. The analysis time for each batch of samples (6 - 8) (including instrument performance inspection, standard curve establishment, liquid-liquid extraction, dehydration, nitrogen blowing concentration, on-machine testing, and issuing of original records) takes about 11 hours. However, by adopting the method of this patent, the analysis time for the same number of samples only takes 6 hours, and the sample analysis efficiency is increased by about 1 time. Moreover, the recovery rate stability of organochlorine pesticides and surrogates is high, and it is not affected by environmental temperature, solvent type and different solvent ratios.

[0013] Further, in the gas chromatography - mass spectrometry analysis, the gas chromatography conditions are as follows: the chromatographic column is DB - 5MS, with a length of 30 m, a film thickness of 250 μm, and an inner diameter of 0.5 μm; the gas chromatography injection port temperature is 280 °C; the carrier gas is helium with a purity of 99.999%; the column flow rate is 1.0 mL / min; the injection volume is 1 μL; the split ratio is 5:1; the temperature - rising program is: the initial temperature is 120 °C, after holding for 1 min, it is heated to 285 °C at a rate of 25 °C / min, and then heated to 300 °C at a rate of 40 °C / min and held for 2 min. The running time of a single - needle sample is 9.975 min; the mass spectrometry conditions are: the ion source is the Extractor high - sensitivity ion source, the electron energy is 70 eV, the ion source temperature is 280 °C, the quadrupole temperature is 150 °C, the transfer line temperature is 280 °C, and the solvent delay is 5 min.

[0014] Further, the automatic nitrogen - blowing instrument controls the nitrogen - blowing pressure to be 8 - 35 psi and the temperature to be 35 - 45 °C.

[0015] Further, the regulator is methanol. Based on the water sample, the volume fraction of methanol is 10 - 20%.

[0016] Further, the volume fraction of methanol is 15%.

[0017] Further, the extractant is n - hexane. Based on the water sample, the volume fraction of n - hexane is 15%.

[0018] Further, in the elution water of the drying column, the drying column is a glass - sand chromatography column filled with anhydrous sodium sulfate, the amount of anhydrous sodium sulfate is 2 - 8 g, and the eluent is dichloromethane.

[0019] Further, in step S3, the violent oscillation frequency of the liquid - liquid extraction oscillator is 260 - 300 times / minute.

[0020] Further, the surrogate is a solution of tetrachloro - m - xylene.

[0021] Further, the original concentration of the tetrachloro - m - xylene solution is 1000 mg / L, the solvent is acetone, and it is diluted to 10 mg / L with the regulator. Based on the water sample, the volume fraction of the diluted tetrachloro - m - xylene solution is 0.02%.

[0022] The present invention has the following advantages:

[0023] 1. By pre - adding a large dose of regulator before extraction, treating with sodium chloride and then performing extraction, and concentrating by automatic nitrogen - blowing and then measuring the content of the target substance in the water sample, the present invention has the advantages of high - efficiency, rapidity, and accuracy in detection.

[0024] 2. This method is simple to operate, low in cost, and has high concentration efficiency and high recovery stability. Brief Description of the Drawings

[0025] Figure 1 This is the process schematic diagram of the present invention.

[0026] Figure 2 This is the chromatogram of the standard sample of the present invention.

[0027] Figure 3 This is the influence of nitrogen blowing pressure and temperature on the recovery rate of tetrachloro-m-xylene.

[0028] Figure 4 This is the influence of nitrogen blowing pressure and temperature on the recovery rate of alpha-hexachlorocyclohexane.

[0029] Figure 5 This is the influence of nitrogen blowing pressure and temperature on the recovery rate of beta-hexachlorocyclohexane.

[0030] Figure 6 This is the influence of nitrogen blowing pressure and temperature on the recovery rate of gamma-hexachlorocyclohexane.

[0031] Figure 7 This is the influence of nitrogen blowing pressure and temperature on the recovery rate of delta-hexachlorocyclohexane.

[0032] Figure 8 This is the influence of the dehydration method of the extraction solution on the recovery rate of the target substance.

[0033] Figure 9 This is the influence of the type of regulator on the recovery rate of the target substance.

[0034] Figure 10 This is the influence of the volume fraction of the regulator on the recovery rate of the target substance.

[0035] Figure 11 This is the influence of the mass of anhydrous sodium sulfate on the recovery rate of the target substance.

[0036] Figure 12 This is the influence of the type of eluent on the recovery rate of the target substance.

[0037] Figure 13 This is the influence of the frequency of liquid-liquid extraction oscillation on the recovery rate of the target substance. Specific embodiments

[0038] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0039] Accordingly, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0040] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0041] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0042] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0043] In the description of the present invention, it should also be noted that unless otherwise clearly specified and defined, the terms "set", "install", "connect", "couple" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0044] Embodiment 1

[0045] Refer to Figure 1 the flow schematic diagram shown. A method for quickly and accurately determining the content of organochlorine pesticides in water includes the following treatment steps:

[0046] S1. Measure 100 ml of the water sample, add a regulator to the water sample and shake well, and then shake well again after adding a surrogate.

[0047] Among them, the regulator is methanol with a volume fraction of 15%, that is, 15 ml of methanol is added; the substitute is a solution of tetrachloro-m-xylene with a stock solution concentration of 1000 mg / L and a solvent of acetone. When in use, it is diluted to 10 mg / L with methanol. Based on the water sample, the volume fraction of the diluted tetrachloro-m-xylene solution is 0.02%, that is, 20 μl of the tetrachloro-m-xylene solution is added;

[0048] S2: Add 10 g of sodium chloride to the water sample processed in step S1, and place it in a liquid-liquid extraction oscillator and shake until completely dissolved;

[0049] S3: Add an extractant to the water sample processed in step S2, shake vigorously for 15 min, and then let it stand for 15 min to separate layers. The lower-layer water sample is drained into a reagent bottle, and the upper-layer extract is transferred to a drying column to wash and dehydrate and then transferred into a concentration bottle;

[0050] Among them, the extractant is n-hexane. Based on the water sample, the volume fraction of n-hexane is 15%, that is, 15 ml of n-hexane is added; control the shaking frequency of the liquid-liquid extraction oscillator to 270 times / min. After shaking vigorously for 15 min, then let it stand for 15 min to separate layers. The lower-layer water sample is drained into a reagent bottle for later use. The upper layer is the extract, which is transferred into a glass sand core chromatography column containing 4 g of anhydrous sodium sulfate, and quickly eluted with the eluent dichloromethane and transferred into a concentration bottle for later use;

[0051] S4: Perform step S3 again on the remaining water sample in step S3;

[0052] S5: Combine the eluents from steps S3 and S4, transfer them into an automatic nitrogen blower to concentrate to 1 ml, add an internal standard solution, make the volume up to 1 ml, transfer it into a 1.5 ml injection vial for gas chromatography-mass spectrometry analysis to obtain the content of organochlorine pesticides in the water sample.

[0053] Among them, the nitrogen blowing pressure of the automatic nitrogen evaporator is 30 psi, the temperature is 44 °C. After concentrating to 1 ml, an internal standard solution (phenanthrene-d10) is added, and it is made up to 1 ml with n-hexane. After mixing evenly, it is transferred to a 1.5 ml injection vial for gas chromatography-mass spectrometry analysis. The gas chromatography conditions are as follows: the chromatographic column is DB-5MS, 30 m long, with a film thickness of 250 μm and an inner diameter of 0.5 μm. The gas chromatography injection port temperature is 280 °C, the carrier gas is helium with a purity of 99.999%, the column flow rate is 1.0 mL / min, the injection volume is 1 μL, and the split ratio is 5:1. The temperature programming is as follows: the initial temperature is 120 °C, after holding for 1 min, it is heated to 285 °C at a rate of 25 °C / min, and then heated to 300 °C at a rate of 40 °C / min and held for 2 min. The running time of a single sample is 9.975 min; the mass spectrometry conditions: the ion source is the Extractor high-sensitivity ion source, the electron energy is 70 ev, the ion source temperature is 280 °C, the quadrupole temperature is 150 °C, the transfer line temperature is 280 °C, and the solvent delay is 5 min. The solution is measured to obtain the content of organochlorine pesticides in the water sample.

[0054] The chromatogram of the standard sample is as Figure 2 shown, and the target ions, auxiliary ions, method detection limits, linear ranges and correlation coefficients are as shown in Table 1

[0055] Table 1 Analytical performance of the method

[0056] Taking surface water and groundwater as environmental media, when the spiked amount of target organochlorine is 1.50 μg / L, the spiked recovery rate of tetrachloro-m-xylene is 90.5%, the spiked recovery rate of α-BHC is 96.8%, the spiked recovery rate of β-BHC is 98.7%, the spiked recovery rate of γ-BHC is 99.4%, and the spiked recovery rate of δ-BHC is 98.1%; when the spiked amount of target organochlorine is 2.00 μg / L, the spiked recovery rate of tetrachloro-m-xylene is 97.5%, the spiked recovery rate of α-BHC is 99.5%, the spiked recovery rate of β-BHC is 100%, the spiked recovery rate of γ-BHC is 99.0%, and the spiked recovery rate of δ-BHC is 98.0%; when the spiked amount of target organochlorine is 2.50 μg / L, the spiked recovery rate of tetrachloro-m-xylene is 94.0%, the spiked recovery rate of α-BHC is 95.2%, the spiked recovery rate of β-BHC is 97.3%, the spiked recovery rate of γ-BHC is 99.6%, and the spiked recovery rate of δ-BHC is 98.0%.

[0057] Example 2

[0058] The control process steps are the same as those in Example 1, only adjusting different nitrogen gas flow pressures and water bath temperatures to study the effects of different nitrogen blowing temperatures (35 - 45 °C) and pressures (8 - 35 psi) on the recovery rate. The experimental results are asFigures 3 - 7 as shown

[0059] Specifically, the fully automatic nitrogen blowing instrument (VortexVap A12 type) adopts the vortex shear air flow technology, and uses the combined method of uniform heating by water bath and vortex nitrogen blowing to accelerate the evaporation and concentration of samples, automatically quantitatively concentrating to 1 ml. It has the advantages of uniform heat transfer, fast concentration speed (only 12 minutes for 60 ml of n-hexane), good parallelism (the time error of concentration parallelism does not exceed 5%), and good recovery rate (the recovery rate of concentration is stable and guaranteed to be over 98%).

[0060] The change of nitrogen gas flow rate is achieved by adjusting the nitrogen gas inlet pressure. With the pipe diameter unchanged, the flow rate is proportional to the pressure. The greater the pressure of the nitrogen gas flow, the greater the nitrogen gas flow rate. The nitrogen gas flow hits the test tube wall to form a vortex. The larger the contact surface area of the solvent and the vortex shear force, the faster the evaporation of the solvent. At the same time, continuously purging nitrogen gas can avoid chemical reactions between the solvent and air, but the pressure cannot be too high, as excessive pressure will cause loss of the target substance.

[0061] The concentration tube is immersed in the water bath, and the temperature of the solution in the concentration tube is controlled by heat transfer. Usually, the water bath temperature control range is from 30°C to 60°C. The temperature setting is determined according to the boiling point of the solvent in the concentration tube and the properties of the analyte. The water bath temperature generally needs to be lower than the boiling point temperature of the solvent, otherwise the evaporation speed may be too fast and the recovery rate may decrease. However, if the temperature is set too low, it will lead to too long concentration time, and long-term nitrogen purging will also cause volatilization of the analyte. When setting the water bath temperature, the boiling point and volatility of the solvent should be fully considered.

[0062] This application fully considers the influence of nitrogen blowing temperature and pressure under different conditions on the recovery rate of the target substance, and obtains the optimal combined temperature and pressure. As shown in the figure, when the pressure is 25 psi, the temperature is 39°C and when the pressure is 30 psi, the temperature is 44°C, the recovery rate of the target substance is above 95%. However, when the pressure is 30 psi and the temperature is 44°C, the concentration time of the extraction solution is the shortest, which is the most preferred. Example Three

[0063] The control process steps are the same as those in Example 1, only the dehydration method of the extraction solution is adjusted, and different extraction solution dehydration methods are selected to study the influence of glass triangular funnel + filter paper, sintered glass funnel + glass wool, and glass sintered chromatography column on the recovery rate of the target substance. The experimental results are as Figure 8 shown. Using the glass sintered chromatography column can effectively improve the recovery rate of the target substance, and the recovery rate is above 95%, which is the most preferred.

[0064] Example Four

[0065] The control process steps are the same as those in Example 1, only the types and contents of the modifiers are adjusted. Different modifiers (no modifier, methanol, acetone) and modifier contents (10%, 15%, 20%) are selected to study the influence of the modifier on the recovery rate of the target substance. The experimental results are as Figures 9 - 10 shown.

[0066] Based on the fact that the polarity of water is the strongest with a value of 10.2, and the polarities of organochlorine pesticides (alpha-BHC, beta-BHC, gamma-BHC, delta-BHC) and the surrogate (tetrachloro-m-xylene) are relatively small. By adding methanol or acetone reagents (the polarity of methanol is 6.6 and the polarity of acetone is 5.4), the polarity of the sample before extraction can be changed, thereby enriching the target substances and surrogates in the water sample, which is beneficial for the extraction agent n-hexane (polarity 0.06) to extract the target substances and surrogates from the sample into n-hexane, and improving the recovery rates of the target organochlorine pesticides and surrogates. Subsequently, the added sodium chloride adjusts the solution polarity again, reduces the solubility of organic substances in water, improves the extraction effect of polar pesticides. At the same time, it can break the liquid surface tension, making the two-phase separation easier, and can effectively avoid the emulsification that easily occurs during extraction.

[0067] As Figures 9 - 10 can be seen, when the sample pretreatment is carried out without pre-adding a modifier, the recovery rate of the target substance is low. While when a modifier is added to the water sample first and then the sample is processed, the recovery rates of the target substances and surrogates are significantly improved. Further comparing the influence of methanol and acetone on the recovery rate of the target substance, the advantage of methanol is more obvious. Further comparing different volume fractions of methanol as a modifier, when the volume fraction of the modifier is 15%, the recovery rates of the target substances and surrogates are significantly improved.

[0068] Example Five

[0069] The control process steps are the same as those in Example 1, only the mass of anhydrous sodium sulfate is adjusted, and different doses (2g, 4g, 6g, 8g) of anhydrous sodium sulfate are controlled to study the influence on the recovery rate of the target substance. The experimental results are as Figure 11 shown.

[0070] Since the extraction liquid n-hexane phase still contains trace amounts of water, and trace amounts of water are not conducive to the concentration of the extraction liquid. At the same time, when entering the gas chromatography-mass spectrometer, it will also damage the chromatographic column. Utilizing the strong water absorption ability of anhydrous sodium sulfate, anhydrous sodium sulfate is added to the funnel or chromatographic column to dehydrate the extraction liquid. However, too much mass of anhydrous sodium sulfate will adsorb the target substance, thereby affecting the recovery rate of the target substance. As Figure 11 shown, when the mass of anhydrous sodium sulfate selected is 4g, the loss of the target substance is the smallest, and the target recovery rate is above 95%.

[0071] Example Six

[0072] The control process steps are the same as those in Example 1, only the type of eluent is adjusted, and different eluents (n-hexane, dichloromethane) are selected to study the effect on the recovery rate of the target substance. The experimental results are as Figure 12 shown.

[0073] It can be analyzed from the foregoing examples that when a glass sand core chromatography column is selected and the mass of anhydrous sodium sulfate is 4 g, the loss of the target substance is the smallest. In the case where the extractant is n-hexane, the eluents are compared with n-hexane and dichloromethane. When dichloromethane is selected as the eluent, the recovery rate of the target substance is higher. Moreover, due to its high density, dichloromethane can quickly elute the anhydrous sodium sulfate target substance into the concentration bottle, reducing the probability of the anhydrous sodium sulfate caking and blocking the chromatography column when it meets water, and the concentration speed is faster, which is more superior to n-hexane.

[0074] Example Seven

[0075] The control process steps are the same as those in Example 1, only the oscillation frequency is adjusted, and the frequency of the liquid-liquid extraction oscillator (MWV-1000W type) is controlled (260 times / minute, 270 times / minute, 280 times / minute, 300 times / minute) to study the effect on the recovery rate of the target substance. The experimental results are as Figure 13 shown.

[0076] The frequency of the liquid-liquid extraction oscillator has a great influence on the extraction effect. If the frequency is too high, the recovery rate of the more volatile organic substances will be reduced; if the frequency is too low, the extraction is incomplete, affecting the recovery rate of the target substance. As Figure 13 shown, when the frequency of the liquid-liquid extraction oscillator is controlled at 270 times / minute, the loss of the target substance is the smallest, and the target recovery rate is above 95%.

[0077] Since the content of hexachlorocyclohexane is low in the analysis of environmental samples, as an important step in the whole analysis process, the pretreatment method has a significant impact on the accuracy and reliability of the measurement results. Using the measurement method of the present application, a large dose of methanol regulator is first added to the water sample and then the sample is processed. Compared with the high-throughput vacuum parallel evaporation concentration pretreatment method, the recovery rate of hexachlorocyclohexane is increased from about 80% of the existing to above 95%, and the recovery rate of 1,2,4,5-tetrachloro-3-methylbenzene is increased from about 30-70% of the existing to above 90%, greatly improving the accuracy of organochlorine pesticides (alpha-hexachlorocyclohexane, beta-hexachlorocyclohexane, gamma-hexachlorocyclohexane, delta-hexachlorocyclohexane) and substitutes (1,2,4,5-tetrachloro-3-methylbenzene).

[0078] Meanwhile, the analysis time of a batch of samples (including instrument performance inspection, standard curve establishment, liquid-liquid extraction, dehydration, nitrogen blowing concentration, machine testing, and issuance of original records) has been reduced from 11 hours to 6 hours. It has the advantages of high efficiency, rapidity, and accuracy in detecting the content of organochlorine pesticides in environmental water samples, as well as simple operation, low cost, and high concentration efficiency. The recovery rate stability of organochlorine pesticides and substitutes is high, and the recovery rate is not affected by environmental temperature, solvent type, and different solvent ratios.

[0079] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for quickly and accurately determining the content of organochlorine pesticides in water, characterized in that: The processing steps include: S1. Add the regulator to the water sample and shake well, then add the substitute and shake well again; S2, adding sodium chloride to the water sample treated in step S1, and shaking in a liquid-liquid extraction oscillator until it is completely dissolved; S3, add the extractant to the water sample treated in step S2, shake vigorously and let it stand to separate into layers, put the lower layer of water sample into the reagent bottle, transfer the upper layer of extract into the drying column, elute with water and then transfer it into the concentration bottle; S4, performing step S3 again on the remaining water samples in step S3; S5. Combine the eluates from steps S3 and S4, transfer to a fully automatic nitrogen blower and concentrate to 1 ml, add an internal standard solution, and perform gas chromatography-mass spectrometry analysis after constant volume to obtain the content of organochlorine pesticides in the water sample; The regulator is methanol, and the volume fraction of the methanol is 10-20% based on the water sample; The extractant is n-hexane, and based on the water sample, the volume fraction of n-hexane is 15%; The drying column elution water, the drying column is a glass sand chromatography column filled with anhydrous sodium sulfate, the anhydrous sodium sulfate is 2-8g, and the eluent is dichloromethane; The substitute is a tetrachloro-m-xylene solution.

2. A method for quickly and accurately determining the content of organochlorine pesticides in water according to claim 1, characterized in that: In the gas chromatography-mass spectrometer analysis, the gas chromatography conditions are as follows: the chromatographic column is DB-5MS, 30 m long, 250 μm thick, 0.5 μm inner diameter, the gas chromatography injection port temperature is 280°C, the carrier gas is 99.999% pure helium, the column flow rate is 1.0 mL / min, the injection volume is 1 μL, the split ratio is 5:1, and the heating program is as follows: the initial temperature is 120°C, and after maintaining for 1 min, the temperature is increased to 285°C at a rate of 25°C / min, and then increased to 300°C at a rate of 40°C / min, and maintained for 2 min, and the single-needle sample running time is 9.975 min; mass spectrometry conditions: the ion source is an Extractor high-sensitivity ion source, the electron energy is 70 ev, the ion source temperature is 280°C, the quadrupole temperature is 150°C, the transmission line temperature is 280°C, and the solvent delay is 5 min.

3. The method for quickly and accurately determining the content of organochlorine pesticides in water according to claim 1, characterized in that: The fully automatic nitrogen blowing instrument controls the nitrogen blowing pressure to be 8-35 psi and the temperature to be 35-45°C.

4. The method for quickly and accurately determining the content of organochlorine pesticides in water according to claim 1, characterized in that: The volume fraction of the methanol is 15%.

5. The method for quickly and accurately determining the content of organochlorine pesticides in water according to claim 1, characterized in that: In step S3, the liquid-liquid extraction oscillator has a violent oscillation frequency of 260-300 times / minute.

6. The method for quickly and accurately determining the content of organochlorine pesticides in water according to claim 1, characterized in that: The original concentration of the tetrachloro-meta-xylene solution is 1000 mg / L, and the solvent is acetone, which is diluted to 10 mg / L with a regulator. Based on the water sample, the volume fraction of the diluted tetrachloro-meta-xylene solution is 0.02%.

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