Method for detecting specific pollutants in pesticide production plot

Abstract

The invention discloses a method for detecting specific pollutants in a pesticide production plot, which can simultaneously detect six specific pollutants including three organophosphorus pesticides including isocarbophos, isofenphos-methyl and profenofos. One pesticide degradation product is dimethyl phosphate; the intermediate product of one pesticide is dimethyl phosphite, and the production raw material of the other pesticide is dimethyl sulfate. The method comprises the following steps: carrying out freeze-drying and grinding on a soil sample, and sieving with a sieve with the aperture of 0.25 mm; uniformly stirring the soil sample and diatomite, and adding a substitute and an extracting agent for extraction treatment to obtain a sample extracting solution; carrying out dehydration treatment on the sample extracting solution; and performing concentration treatment on the sample extracting solution to obtain a to-be-detected sample solution containing six target objects. The method can be used for simultaneously detecting specific pollutants of 6 pesticide production plots, and the detection rate is high; by adding an interior label, the accuracy of the method is improved; and the qualification rate of sample detection is improved by adding a substitute.

Description

Technical Field

[0001] The invention belongs to the technical field of soil sample pesticide detection, and in particular relates to a method for detecting characteristic pollutants in a pesticide production plot. Background Art

[0002] Due to the lack of relevant testing standards and methods for some pesticide indicators, pesticide production raw materials or pesticide degradation product indicators, the characteristic pollutants of some pesticide plots cannot be detected and are ignored. However, some agricultural production raw materials, pesticide degradation products or pesticide intermediates are highly toxic compounds, such as dimethyl sulfate, dimethyl phosphate, and dimethyl phosphite, which cannot be ignored when investigating pesticide production plots, so it is particularly necessary to develop accurate and efficient analytical methods.

[0003] The chemical name of propyl bromide is O-ethyl-O-(2-chloro-4-bromophenyl)-S-propyl thiophosphate, which has a special garlic smell. Its pure product is a light yellow oily transparent liquid. It is a thiophosphate insecticide containing n-propylthio group in the molecule. It is often used to control pests of crops such as cotton and vegetables. It has obvious effects and strong adsorption capacity. It is currently a widely used type of pesticide.

[0004] Methyl isothioate and isocarbophos are highly toxic pesticides.

[0005] Dimethyl phosphate is the degradation product of pesticides such as fenthion, methyl phosphonium, and omethoate; dimethyl phosphite is the intermediate product of omethoate and trichlorfon; dimethyl sulfate is the raw material for the production of oxadiazine, thiram, and fenthion, all of which are highly toxic. Therefore, it is necessary to establish a sensitive and accurate analytical method to monitor the characteristic pollutants involved in the upstream and downstream of the production process of organophosphorus pesticides in the soil, so as to facilitate the investigation and evaluation of pesticide plots. Summary of the invention

[0006] In view of the above problems, the present invention discloses a method for detecting characteristic pollutants in a pesticide production plot, comprising the following steps:

[0007] Pre-treatment of soil samples;

[0008] The soil sample and diatomaceous earth are mixed evenly, and a substitute and an extractant are added to perform extraction treatment to obtain a sample extract;

[0009] Dehydrating and purifying the sample extract;

[0010] Concentrating the sample extract after dehydration and purification to obtain a sample solution containing isocarbophos, isothioate-methyl, profenofos, dimethyl phosphate, dimethyl phosphite, and dimethyl sulfate;

[0011] An internal standard is added to the sample solution to detect the content of the target substance.

[0012] Furthermore, the pretreatment of the soil sample comprises the following steps:

[0013] Take soil samples, remove weeds and stones from the soil samples, and seal them in brown glass bottles;

[0014] The soil sample is placed in an enamel or glass tray, and then branches and leaves are removed, and the soil sample is thoroughly mixed.

[0015] Furthermore, the soil samples were freeze-dried, ground, and sieved through a 0.25 mm sieve.

[0016] Furthermore, the extractant is a mixed solvent of n-hexane and acetone in a volume ratio of 1:1.

[0017] Furthermore, the dehydration and purification of the sample extract comprises the following steps:

[0018] Step 1: Extract the sample with liquid nitrogen or evaporate it to 3-5 mL;

[0019] Step 2: Add 10-20 mL of n-hexane to the sample extract, continue nitrogen blowing or rotary evaporation to 3-5 mL, repeat steps 1 and 2 twice, and then nitrogen blow or rotary evaporate the sample extract to 1.5-2.5 mL;

[0020] Step 3: Dehydrating the sample extract after dehydration using anhydrous sodium sulfate;

[0021] Step 4: Purify the sample extract after dehydration.

[0022] Furthermore, the conditions of the concentration treatment are: water temperature 30-35°C, nitrogen blowing speed 2-3mL / min.

[0023] Furthermore, the purification process uses a silica gel solid phase extraction column.

[0024] Furthermore, the elution solvent of the target object is ethyl acetate, a low-toxic solvent with similar polarity to the target object.

[0025] Furthermore, the characteristic pollutants of the pesticide production plot are carbofuran, methyl isothioate, propyl bromide, dimethyl phosphate, dimethyl phosphite, and dimethyl sulfate.

[0026] Furthermore, the internal standard substances are naphthalene-d8, phenanthrene-d10, and 1,4-dichlorobenzene-d4.

[0027] Furthermore, the substitutes are 2-fluorophenol and p-terphenyl-d14.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: it solves the problem that the pollution degree of soil plots cannot be effectively evaluated due to the lack of detection standards or detection methods for isocarbophos, methyl isofos, profenofos, dimethyl phosphate, dimethyl phosphite, and dimethyl sulfate in the soil when investigating pesticide production plots. At the same time, the detection method can detect the above 6 targets at the same time, and the detection rate is high. Ethyl acetate, a low-toxic solvent with similar polarity to the target, is used as an eluent to improve the recovery rate of the target. Adding internal standards and substitutes to soil samples can improve the accuracy and precision of the method.

[0029] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 shows a total ion current diagram of a soil sample 1 solution according to an embodiment of the present invention;

[0032] Figure 2 shows a total ion current diagram of a spiked soil sample 1 solution according to an embodiment of the present invention;

[0033] Figure 3 shows a total ion current diagram of a soil sample 2 solution according to an embodiment of the present invention;

[0034] Figure 4 shows a total ion current diagram of a spiked soil sample 2 solution according to an embodiment of the present invention;

[0035] Figure 5 shows a total ion current diagram of a soil sample 3 solution according to an embodiment of the present invention;

[0036] Figure 6 shows a total ion current diagram of a spiked soil sample 3 solution according to an embodiment of the present invention; DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The reagents and equipment used in the examples of the present invention are as follows.

[0039] Reagents:

[0040] n-Hexane: Pesticide Residue Grade

[0041] Acetone: pesticide residue level;

[0042] Ethyl acetate: pesticide residue grade;

[0043] Diatomaceous earth: high-grade pure;

[0044] Solid phase extraction column: The filler is silica gel, 1 g, and the column volume is 6 mL;

[0045] Anhydrous sodium sulfate: high purity;

[0046] Internal standards: naphthalene-d8, phenanthrene-d10, 1,4-dichlorobenzene-d4, 1000 mg / L;

[0047] Alternatives: 2-fluorophenol and terphenyl-d14, 1000 mg / L.

[0048] instrument:

[0049] Small funnel: Tianjin Tianbo Glass Co., Ltd.;

[0050] Separatory funnel: Tianjin Tianbo Glass Co., Ltd.;

[0051] Concentrate cup: 250mL, 100mL produced by Beijing Labtech Instrument Co., Ltd.

[0052] Brown glass bottle: Tianjin Tianbo Glass Co., Ltd.

[0053] Parallel concentrator: MultiVap, Beijing Labtech Instrument Co., Ltd.;

[0054] Rotary evaporator: BUCHI rotary evaporator R-300;

[0055] Gas chromatograph mass spectrometer: Agilent GCMS7890B-5977B.

[0056] The present invention provides a method for detecting characteristic pollutants in a pesticide production plot, comprising the following steps:

[0057] Pre-treatment of soil samples;

[0058] The soil sample was freeze-dried, and most of the water in the sample was removed before grinding and passing through a 0.25 mm sieve. Take part of the ground and sieved soil sample and stir it evenly with diatomaceous earth, add a substitute, add a mixed solvent of n-hexane and acetone in a volume ratio of 1:1 as an extractant, perform extraction treatment, and obtain a sample extract. At this time, the sample extract is an acetone-n-hexane-water extraction solution of phosphamidon, methyl isofenphos, bromophos, dimethyl phosphate, dimethyl phosphite, and dimethyl sulfate (hereinafter referred to as the target substance); exemplarily, take 10g of freeze-dried, ground and sieved soil sample, stir the soil sample evenly with diatomaceous earth, on the one hand further remove water from the soil sample, and on the other hand disperse the soil sample to increase the specific surface area of ​​the soil sample; the substitutes are 2-fluorophenol and terphenyl-d14, which can monitor the loss or contamination of the target substance in the pretreatment operation of the soil sample; the extraction treatment uses extraction equipment such as a rapid solvent extractor, a microwave extractor or a Soxhlet extractor; the amount of the extractant used is related to the size of the extraction pool and the number of extractions. For example, for a 40mL extraction pool, the extraction is performed twice, and the amount of the extractant used is 80mL;

[0059] The sample extract is converted into a n-hexane solvent system using n-hexane, and then dehydrated; the dehydration is chemical dehydration, and anhydrous sodium sulfate is used to remove residual water in the sample extract;

[0060] The sample extract after dehydration and purification is concentrated to obtain a sample solution containing the target object; the conditions for the concentration treatment are: water temperature 30-35°C, nitrogen blowing rate 2-3mL / min, preferably water temperature 30°C, nitrogen blowing rate 3mL / min, and the concentration treatment can reduce the detection limit of the target object;

[0061] An internal standard is added to the sample solution to be tested, and the solution is transferred to a 2 mL injection vial, and the content of the target substance is detected by a gas chromatograph-mass spectrometer. The internal standard is naphthalene-d8, phenanthrene-d10, and 1,4-dichlorobenzene-d4.

[0062] Since the 1:1 ratio of acetone to n-hexane contains polar and non-polar solvents, acetone can destroy the water film in the soil so that the extractant can directly contact the target in the soil, greatly improving the extraction efficiency. Therefore, the extractant must be a mixed solvent of n-hexane and acetone in a volume ratio of 1:1.

[0063] The pretreatment of soil samples includes the following steps:

[0064] Take soil samples, remove weeds and stones from the soil samples, and seal them in brown glass bottles;

[0065] The soil sample is placed in an enamel or glass tray, and then the branches and leaves are removed and the mixture is thoroughly mixed. The mixed soil sample is freeze-dried in a vacuum freeze dryer for preliminary dehydration, which improves the sample extraction efficiency and reduces the pressure of subsequent dehydration and purification of the sample.

[0066] The dehydration treatment of the sample extract comprises the following steps:

[0067] Step 1: Extract the sample with liquid nitrogen and blow or evaporating to 3-5 mL; at this time, the solution is a small amount of acetone, n-hexane and water. If the sample has a large water content, the amount of water will not be reduced due to its high boiling point, and the solution is turbid. Water and acetone are mutually soluble, but insoluble in n-hexane;

[0068] Step 2: Add 10-20 mL of n-hexane to the sample extract, continue nitrogen blowing or rotary evaporation to 3-5 mL, repeat steps 1 and 2 twice, and then nitrogen blow or rotary evaporate the sample extract to 1.5-2.5 mL; the boiling point of acetone is lower than that of n-hexane, and n-hexane is added for multiple nitrogen blowing or rotary evaporation operations, the acetone is basically evaporated, and the remaining solution is n-hexane and water, which are immiscible, and the solution is in a state of upper and lower layers, requiring subsequent dehydration treatment;

[0069] Among them, the presence of acetone will affect the subsequent dehydration effect, the presence of water will affect the purification efficiency, and poor purification of the sample solution will affect the detection results of the target object, so the solvent transfer treatment step is crucial.

[0070] The dehydration and purification of the sample extract after the solvent transfer treatment comprises the following steps:

[0071] The sample extract after the solvent transfer treatment was dehydrated using anhydrous sodium sulfate;

[0072] The dehydrated sample extract was purified using a silica gel solid phase extraction column.

[0073] Exemplarily, the specific steps of dehydration and purification of the sample extract are as follows: fix the silica gel solid phase extraction column on the solid phase extraction device, close the control valve, plug the small funnel with glass wool, put anhydrous sodium sulfate in the small funnel, and put the small funnel on the silica gel solid phase extraction column; first pour 15mL of n-hexane into the small funnel, rinse the small funnel, anhydrous sodium sulfate and silica gel solid phase extraction column in turn (this step is to clean the vessel, anhydrous sodium sulfate and activated silica gel solid phase extraction column), open the control valve to discard the effluent, before the anhydrous sodium sulfate and silica gel solid phase extraction column filler are exposed to the air, close the control valve, and then transfer the sample extract after the solvent transfer treatment to the small funnel evenly for dehydration, and the effluent enters the silica gel solid phase extraction column to remove impurities. Wash the concentration vessel three times with 2ml of n-hexane, transfer all the washing liquid into the small funnel, slowly open the control valve, and use a 100mL concentration cup to receive the sample extract after purification of the silica gel solid phase extraction column. Before the filler is exposed to the air, use 15 mL of ethyl acetate solvent to elute the anhydrous sodium sulfate and silica gel solid phase extraction column. After the eluent has soaked the silica gel solid phase extraction column, close the control valve and soak for 2 minutes. Slowly open the control valve and continue to receive it with the above-mentioned 100 mL concentration cup for concentration treatment.

[0074] Among them, it should be noted that when washing anhydrous sodium sulfate and activated silica gel solid phase extraction column with n-hexane solvent, it is necessary to keep anhydrous sodium sulfate moist, and there is n-hexane solvent above the sieve plate of silica gel solid phase extraction column, and the solvent cannot be completely volatilized to prevent air from entering the filler, thereby blocking the target solution from flowing out, which will increase the time of purification to a certain extent, and will lose a certain target. The anhydrous sodium sulfate in the purification step is used to remove a small amount of water remaining in the target solution in the n-hexane system to obtain a target solution of n-hexane without moisture. Since the soil freeze-drying process has removed most of the water, when anhydrous sodium sulfate is used to remove a small amount of water remaining in the target solution in the n-hexane system, water will not penetrate the anhydrous sodium sulfate to cause the anhydrous sodium sulfate to harden, which is conducive to the subsequent elution of the target, improves the recovery rate of the target, and can also save the use of anhydrous sodium sulfate and reduce the detection cost.

[0075] After multiple tests, ethyl acetate was found to have high elution efficiency and low toxicity for the target substances, so ethyl acetate was selected as the elution solvent for the six target substances.

[0076] The sample extract after dehydration and purification is concentrated to obtain a sample solution containing the target substance, which comprises the following steps:

[0077] The sample extract was concentrated to a volume of 1 mL using a parallel concentrator or a nitrogen blowdown instrument to obtain a sample solution to be tested.

[0078] Chromatographic conditions:

[0079] Inlet temperature: 280°C, no split, or split injection (when the sample concentration is high or the instrument sensitivity is sufficient);

[0080] Injection volume: 1.0 μL;

[0081] Column flow rate: 1.0 mL / min (constant flow);

[0082] Column temperature: 50℃ for 2 min, then increase to 100℃ at a rate of 20℃ / min, then increase to 295℃ at a rate of 25℃ / min and maintain for 8 min;

[0083] Mass spectrometry reference conditions:

[0084] Electron impact source (EI);

[0085] Ion source temperature: 230°C;

[0086] Ionization energy: 70eV;

[0087] Interface temperature: 280℃;

[0088] Quadrupole temperature: 150℃;

[0089] Mass scanning range: 45amu~450amu;

[0090] Solvent delay time: 5min;

[0091] Scan mode: full scan or ion mode (SIM).

[0092] Embodiment 1:

[0093] According to the above experimental process, 12.04g (accurate to 0.01g) of soil sample 1 (TG20230617-0711-202) was taken to measure its background concentration, and 11.41g (accurate to 0.01g) of the same soil sample was added with 5000ng of isothiocarb, methyl isofenphos, profenofos, dimethyl phosphate, and dimethyl phosphite standard solutions as spiked soil sample 1 (TG20230617-0711-202 spiked) to measure its spiked recovery rate. Figure 1 , Figure 2 As shown, the method of the present invention can measure 6 kinds of target substances, and their retention time and quantitative ion are shown in Table 1. Naphthalene-d8, phenanthrene-d10, and 1,4-dichlorobenzene-d4 are used as internal standards to eliminate the injection error of the instrument. The results of the spike recovery experiment are shown in Table 1, and the spike recovery rates of the 6 kinds of target substances all meet the requirements.

[0094] Table 1 Experimental results of spiked recovery of soil sample 1

[0095]

[0096] Embodiment 2:

[0097] According to the above experimental process, 11.09g (accurate to 0.01g) of soil sample 2 (TG20230617-0712-051) was taken to measure its background concentration, and 12.21g (accurate to 0.01g) of the same soil sample was added with 5000ng of isocarbophos, methyl isofenphos, profenofos, dimethyl phosphate, and dimethyl phosphite standard solution as spiked soil sample 2 (TG20230617-0712-051 spiked) to measure its spiked recovery rate. Figure 3 , Figure 4 As shown, the method of the present invention can measure 6 kinds of target substances, and their retention time and quantitative ion are shown in Table 1. Naphthalene-d8, phenanthrene-d10, and 1,4-dichlorobenzene-d4 are used as internal standards to eliminate the injection error of the instrument. The results of the spike recovery experiment are shown in Table 1, and the spike recovery rates of the 6 kinds of target substances all meet the requirements.

[0098] Table 2 Experimental results of spiked recovery of soil sample 2

[0099]

[0100] Embodiment 3:

[0101] According to the above experimental process, 11.66g (accurate to 0.01g) of soil sample 3 (TG20230617-0712-101) was taken to measure its background concentration, and another 11.66g (accurate to 0.01g) of the same soil sample was added with 5000ng of isothiocarb, methyl isofenphos, profenofos, dimethyl phosphate, and dimethyl phosphite standard solution as spiked soil sample 3 (TG20230617-0712-101 spiked), and its spiked recovery rate was measured. Figure 5 , Figure 6 As shown, the method of the present invention can measure 6 kinds of target substances, and their retention time and quantitative ion are shown in Table 1. Naphthalene-d8, phenanthrene-d10, and 1,4-dichlorobenzene-d4 are used as internal standards to eliminate the injection error of the instrument. The results of the spike recovery experiment are shown in Table 1, and the spike recovery rates of the 6 kinds of target substances all meet the requirements.

[0102] Table 3 Experimental results of spiked recovery of soil sample 3

[0103]

[0104] Using 2-fluorophenol and terphenyl-d14 as substitutes can monitor the extraction and concentration process, and the recovery rate of the substitutes in the soil sample is shown in Table 4. It can be seen from Table 4 that the recovery rate of the substitutes is between 40% and 97%, which meets the requirement of 40% to 150%, proving the effectiveness of the present invention.

[0105] Table 4 Experimental results of surrogate recovery in soil samples

[0106]

[0107]

[0108] It can be seen from the above embodiments that, using the method for detecting characteristic pollutants in pesticide production plots proposed in the present invention, the spiked recovery rate of the method is determined to be in the range of 70.7% to 100.3%, and the recovery rate of the substitute is in the range of 73% to 103%, which meets the method requirements and proves the effectiveness of the present invention.

[0109] The present invention proposes a method for detecting characteristic pollutants of pesticide production plots, which can determine isocarbophos, methyl isofos, profenofos, dimethyl phosphate, dimethyl phosphite, and dimethyl sulfate in soil samples, solving the problem of no detection standards and detection methods for common characteristic pollutants in pesticide plots. The simultaneous detection of 6 substances greatly improves the detection efficiency; the freeze-drying method is used for soil samples to reduce the water content in the sample at the source, improve the sample extraction efficiency, and reduce the amount of anhydrous sodium sulfate used in subsequent sample dehydration, prevent anhydrous sodium sulfate from being penetrated and hardened by the aqueous phase, and reduce the elution pressure of the target. Ethyl acetate, which has extremely low toxicity and can improve the elution efficiency of the target, is used as the elution solvent to improve the recovery rate of the target. The internal standard method and the addition of substitutes can improve the accuracy of sample detection and the qualified rate of the sample.

[0110] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting characteristic pollutants in pesticide production plots, characterized in that: The following steps are involved: Pre-treatment of soil samples; The soil sample was freeze-dried using a freeze dryer, then ground and passed through a 0.25 mm pore size sieve. The ground soil and diatomaceous earth are mixed evenly, and a substitute and an extractant are added to perform extraction treatment to obtain a sample extract; Purifying the extract; The sample extract after purification is concentrated to obtain a sample solution containing six characteristic pollutants of pesticide production plots; An internal standard is added to the sample solution to be tested, and the contents of isocarbophos, isothioate-methyl, profenofos, dimethyl phosphate, dimethyl phosphite and dimethyl sulfate are detected.

2. The method for detecting characteristic pollutants in a pesticide production plot according to claim 1, characterized in that: The soil sample is pretreated comprising the following steps: Take soil samples, remove weeds and stones from the soil samples, and seal them in brown glass bottles; The soil sample is placed in an enamel or glass tray, and then branches and leaves are removed and mixed thoroughly. The soil sample was freeze-dried using a vacuum freeze dryer and then ground through a 0.25 mm sieve to remove moisture from the soil.

3. The method for detecting characteristic pollutants in a pesticide production plot according to claim 1, characterized in that: The extractant is a mixed solvent of n-hexane and acetone in a volume ratio of 1:1, and the extraction method is a pressurized fluid extraction method.

4. The method for detecting characteristic pollutants in a pesticide production plot according to claim 1, characterized in that: The sample extract is subjected to solvent conversion treatment, comprising the following steps: Step 1: Extract the sample with liquid nitrogen or evaporate it to 3-5 mL; Step 2: Add 10-20 mL of n-hexane to the sample extract, continue nitrogen blowing or rotary evaporation to 3-5 mL, repeat steps 1 and 2 twice, and then nitrogen blow or rotary evaporate the sample extract to 1.5-2.5 mL.

5. The method for detecting characteristic pollutants in a pesticide production plot according to claim 1, characterized in that: Purifying the sample extract after the solvent transfer treatment comprises the following steps: The sample extract after solvent transfer treatment is purified using an activated silica gel column.

6. The method for detecting characteristic pollutants in a pesticide production plot according to claim 1, characterized in that: The conditions of the concentration treatment are: water temperature 30-35°C, nitrogen blowing speed 2-3mL / min.

7. A method for detecting characteristic pollutants in a pesticide production plot according to claim 1 or 5, characterized in that: The purification process uses a silica gel solid phase extraction column.

8. The method for detecting characteristic pollutants in a pesticide production plot according to claim 1, characterized in that: The method can simultaneously determine isocarbophos, isothioate-methyl, profenofos, dimethyl phosphate, dimethyl phosphite and dimethyl sulfate in soil.

9. The method for detecting characteristic pollutants in a pesticide production plot according to claim 1, characterized in that: The internal standards are naphthalene-d8, phenanthrene-d10, and 1,4-dichlorobenzene-d4.

10. The method for detecting characteristic pollutants in a pesticide production plot according to claim 1, characterized in that: The substitutes are 2-fluorophenol and p-terphenyl-d14.

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