Fe3O4 (at) PS-TMG material and extraction detection method thereof

Abstract

The invention discloses a preparation and extraction detection method of a Fe3O4 (at) PS-TMG material, and the method comprises the following steps: S1, preparing a Fe3O4 magnetic fluid by adopting a coprecipitation method, and then drying the Fe3O4 magnetic fluid by using anhydrous Na2SO4 for later use; s2, a miniemulsion polymerization method is adopted to prepare Fe3O4 (at) Chloromethyl PS nano particles, and the Fe3O4 (at) Chloromethyl PS nano particles are prepared; s3, continuously adding tetrahydrofuran, TMG, Bu4NI and NaOH into the Fe3O4 and Chloromethyl PS nanoparticles according to the molar ratio of 1: 1: 1: 1: 1: 4, and carrying out reflux reaction under the protection action of nitrogen gas, wherein the molar ratio of the tetrahydrofuran to the TMG to the Bu4NI to the NaOH to the Fe3O4 and Chloromethyl PS nanoparticles is 1: 1: 1: 1: 4; and S4, after the reaction is finished, performing freeze drying to obtain the Fe3O4 coated PS-TMG material. The method provided by the invention has the advantages of high detection speed, high precision, high extraction rate, low material consumption, low loss, good reproducibility and the like, and has good economic benefits and application prospects in the aspect of pesticide residue detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of agricultural residue detection, and specifically relates to an Fe3O4@PS-TMG material and an extraction and detection method thereof. Background Art

[0002] Organophosphorus pesticides are mainly used in the prevention and control of agricultural and forestry pests, and have made important contributions to the growth and yield increase of crops. At the same time, due to the overuse of organophosphorus pesticides, it has caused serious threats to the ecological environment and organisms. Residual organophosphorus and its metabolites in food will cause pollution of agricultural and livestock products and the ecological environment and threaten human life and health. Organophosphorus pesticides are one of the most widely used insecticides in the world, with the characteristics of high efficiency, low toxicity, and low residue.

[0003] However, organophosphorus pesticides cause an increase in the content of acetylcholine in the human body mechanism by inhibiting acetylcholinesterase, and when accumulated to a certain extent, it will cause muscarinic symptoms. Severe acute poisoning patients will also experience delayed sudden death. Delayed neuropathy may occur within 8-14 days after organophosphorus poisoning, and organophosphorus poisoning will cause a rapid decline in the activity of cholinesterase in the blood.

[0004] Existing pretreatment methods for agricultural residues include liquid-liquid extraction, solid-phase extraction, liquid-phase microextraction, matrix solid-phase dispersion extraction, stir bar sorptive extraction, magnetic solid-phase extraction, and QuEChERS method. However, these pretreatment methods for agricultural residues mainly have the following defects: 1. It is impossible to completely remove all agricultural residues: The current pretreatment methods for agricultural residues mainly rely on chemical treatment methods, so it is difficult to completely remove all agricultural residues, and the residue rate of agricultural residues will reach more than 50%. 2. The treatment time is relatively long: Many pretreatment methods for agricultural residues require a certain amount of time to achieve an ideal treatment effect, which may have a certain impact on some products that need to be processed urgently. 3. The treatment effect is difficult to guarantee: Different pretreatment methods for agricultural residues may have different treatment effects on different agricultural residues, and different products may require different treatment methods. 4. Impact on the environment: Some pretreatment methods for agricultural residues may have an adverse impact on the environment. For example, the use of organic solvents may pollute the water source. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an Fe3O4@PS-TMG material and an extraction and detection method thereof, which solve the above technical problems existing in the prior art.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The preparation of an Fe3O4@PS-TMG material includes the following steps:

[0008] S1. Prepare Fe3O4 magnetic fluid by coprecipitation method, and then dry it with anhydrous Na2SO4 for later use;

[0009] S2. Prepare Fe3O4@Chloromethyl PS nanoparticles by miniemulsion polymerization method;

[0010] S3. Subsequently, add tetrahydrofuran, TMG, Bu4NI, and NaOH to the Fe3O4@Chloromethyl PS nanoparticles according to the molar ratio of 1:1:1:1:4, and reflux the reaction under the protection of nitrogen;

[0011] S4. After the reaction, freeze-dry to obtain Fe3O4@PS-TMG material.

[0012] Further, in S3, the reflux reaction time is 24 h.

[0013] Further, before freeze-drying, wash with tetrahydrofuran and methanol in sequence.

[0014] A kind of Fe3O4@PS-TMG material is applied to the detection of organophosphorus pesticide residues.

[0015] Further, when the Fe3O4@PS-TMG material is used for the detection of organophosphorus pesticide residues, the extraction method for pretreatment includes the following steps:

[0016] S11. Activation: Add the weighed Fe3O4@PS-TMG material to methanol and water with a volume ratio of 1:1 for activation, and then perform ultrasonic treatment;

[0017] S12. Magnetic separation: After the Fe3O4@PS-TMG material is activated, perform magnetic separation, and sample after standing until the water sample is clear;

[0018] S13. Ultrasonic extraction: Then add the sample solution to the sampled liquid, and then perform ultrasonic treatment again to make the Fe3O4@PS-TMG material fully adsorb the target analyte as a magnetic adsorbent;

[0019] S14. Secondary magnetic separation: After ultrasonic treatment, perform magnetic separation on the sample again, and pour out the liquid sample after standing until the water sample is clear;

[0020] S15. Elution: Perform elution after the liquid sample is removed;

[0021] S16. Tertiary magnetic separation: After elution, perform magnetic separation on the material, pour the eluate into a test tube after standing until the liquid sample is clear, and collect the eluate for nitrogen blowing;

[0022] S17. Nitrogen blowing: Make a constant volume of the eluate after nitrogen blowing;

[0023] S18, constant volume, filtration and bottling.

[0024] Furthermore, in S11, the activation time is 1 - 2 min.

[0025] Furthermore, in S11, the ultrasonic time is 4 - 5 min.

[0026] Advantages of the present invention:

[0027] 1. In this application, Fe3O4 in Fe3O4@PS-TMG is the most widely used in soft magnetic materials. The product Fe3O4@Chloromethyl PS after being coated with PS exhibits the properties of a superparamagnetic material. Tetramethylguanidine can not only serve as the catalytic active center but also regulate the surface activity of substances. The Fe3O4@PS-TMG material modified by tetramethylguanidine not only does not lose the original properties of Fe3O4@Chloromethyl PS but also has stronger surface activity.

[0028] 2. In this application, the Fe3O4@PS-TMG material is obtained by coating or modifying the original magnetic material through a modification method. Analyzing this topic with this material has the significance of phased improvement. It can not only be used as an adsorbent for pesticide residue detection but also can inversely characterize the defects of the unmodified magnetic material, which is of great significance for using this series of magnetic materials as magnetic solid-phase extraction adsorbents for pesticide residue detection.

[0029] 3. In this application, the extraction and detection method based on the Fe3O4@PS-TMG material has a relatively high extraction efficiency, and basically can reach 80%. At the same time, it has the characteristics of fast detection, high precision, less material consumption, and less loss. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art.

[0031] Figure 1 It is the infrared spectrum diagram of Fe3O4@PS-TMG in the embodiment of the present invention;

[0032] Figure 2 It is the XRD spectrum diagram of Fe3O4@PS-TMG in the embodiment of the present invention;

[0033] Figure 3 It is the TEM spectrum diagram of Fe3O4@PS-TMG in the embodiment of the present invention;

[0034] Figure 4 It is the comparison diagram of the extraction rates of different sulfur and phosphorus content pesticide residues in the embodiment of the present invention;

[0035] Figure 5 It is a comparison chart of extraction rates of different elution solvent types in the embodiments of the present invention;

[0036] Figure 6 It is a comparison chart of extraction rates with different ultrasonic extraction times in the embodiments of the present invention;

[0037] Figure 7 It is a comparison chart of extraction rates when the Fe3O4@PS-TMG material is used 6 times in the embodiments of the present invention. Detailed implementation manners

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0039] Regarding the preparation of the Fe3O4@PS-TMG material, Fe3O4 magnetic fluid was prepared by the co-precipitation method, and then dried with anhydrous Na2SO4 for later use. Fe3O4@Chloromethyl PS nanoparticles were prepared by the miniemulsion polymerization method. Then, the materials were weighed according to the following proportions: Fe3O4@Chloromethyl PS (1 mmol·g –1 -CH2Cl, 1 g), tetrahydrofuran (75 mL), TMG (0.12 g / 0.23 g / 0.58 g), Bu4NI (0.25 g) and NaOH (0.5 g) were added to a 250 mL round-bottom flask. The reaction was refluxed for 24 h under N2 protection. After the reaction, it was washed successively with tetrahydrofuran (3×50 mL) and methanol (3×50 mL), and freeze-dried for 12 h to obtain the Fe3O4@PS-TMG material.

[0040] The obtained Fe3O4@PS-TMG is magnetic iron oxide (Fe3O4) nanoparticles coated with polystyrene (PS) modified by tetramethylguanidine, and has a micro-orange appearance and uniform particle size of nanospheres.

[0041] As Figure 1 shown, the Fe3O4@PS-TMG was analyzed by an infrared spectrometer. At 589 cm -1 the bending vibration peak of Fe-O is the characteristic peak of Fe3O4; the bending vibration peak of C-H on the surface at 670 cm -1 ; at 756 cm -1 is the characteristic peak of monosubstitution of the benzene ring; at 1492 cm -1 and 1600 cm -1 are the benzene ring skeletal vibration peaks; 1650 cm -1is the characteristic peak of the C=N bond; the absorption peaks appearing at 2832 cm -1 and 2923 cm -1 were found to be possibly the stretching vibration peaks of saturated C-H after comparing the spectra; the stretching vibration peak of C-H on the benzene ring appeared at 3032 cm -1 . The above results indicate that TMG has been successfully loaded on Fe3O4@PS. According to the infrared characterization spectrum, the approximate functional groups and structure of Fe3O4@PS-TMG can be known, and its performance can be speculated.

[0042] As Figure 2 shown, by using XRD to analyze Fe3O4@PS-TMG, the scanning speed was set at 5 deg / min and scanned from 10 deg to 90 deg. The results are as shown above. A distinct large peak appeared at 19.8° for the Fe3O4@PS-TMG material. Combining with other two-phase characterizations, it can be speculated that it is the characteristic diffraction peak of Fe3O4@PS, while the peaks appearing in the range of 30° - 65° are the diffraction peaks of Fe3O4. Among them, the diffraction peak appearing at 30.1° corresponds to the (220) crystal plane of Fe3O4, the diffraction peak appearing at 25.5° corresponds to the (331) crystal plane of Fe3O4; the diffraction peak appearing at 43.1° corresponds to the (400) crystal plane of Fe3O4; the diffraction peak appearing at 57.0° corresponds to the (511) crystal plane of Fe3O4; the diffraction peak appearing at 62.6° corresponds to the (440) crystal plane of Fe3O4.

[0043] As Figure 3 shown, using TEM to analyze Fe3O4@PS-TMG, the TEM image as shown in the figure was obtained. From the figure with a scale of 100 nm, the morphology of Fe3O4@PS-TMG can be clearly seen. The particle size of Fe3O4@PS-TMG is about 50 nm - 100 nm, and the appearance is a series of connected and uniformly sized small balls. There are several small balls connected around a large ball with an indefinite number. The large ball in the middle is dark gray and opaque, and the small balls on the outside are light gray. From its structure, it can be speculated that the dark gray and opaque large ball in the middle is Fe3O4, and the light gray small balls with uniform particle size connected on the side are Fe3O4@PS. The above results indicate that Fe3O4@PS-TMG belongs to the nanometer category.

[0044] When testing the performance of the magnetic substance Fe3O4@PS-TMG, first activate the substance:

[0045] Sample weighing: Weigh 10 mg of the Fe3O4@PS-TMG material using an analytical balance and label for remarks.

[0046] S11. Activation: Add the weighed materials to 3 mL of methanol and 3 mL of water for activation respectively. After shaking well, activate for 2 min. Sonicate for 5 min. To ensure that the materials are evenly dispersed without agglomeration and to achieve as complete activation as possible, the sample state can be observed during sonication, and the materials can be intermittently shaken alternately while sonicating.

[0047] S12. Primary magnetic separation: After the Fe3O4@PS-TMG materials are activated, perform magnetic separation, and let it stand until the water sample is clear, then pour out the liquid sample.

[0048] Add water standard sample: After pouring out the liquid sample, add 20 mL of the mixed standard solution of four sulfur and phosphorus compounds (fenthion, parathion, phoxim, and etrimfos) (4 μg / mL) to the bottle. Use a pipette or graduated cylinder and a microsyringe to take the water sample and the sulfur and phosphorus mixed standard solution respectively, and shake well.

[0049] S13. Ultrasonic extraction: Sonicate the Fe3O4@PS-TMG materials added with the mixed standard for 5 min to allow the magnetic adsorbent to fully adsorb and extract the four sulfur and phosphorus pollutants.

[0050] S14. Secondary magnetic separation: After sonication, perform magnetic separation on the sample again, and let it stand until the water sample is clear, then pour out the liquid sample.

[0051] S15. Elution: After pouring out the liquid sample, add 3 mL of methanol to the bottle for elution, and use a pipette to transfer methanol for elution. Shake slightly to fully disperse the materials.

[0052] S16. Tertiary magnetic separation: After elution, perform magnetic separation on the materials, and let it stand until the liquid sample is clear. Then pour the eluate into a test tube and collect the eluate for nitrogen blowing.

[0053] S17. Nitrogen blowing: Blow the eluate by nitrogen until it is less than 1 mL and then make up the volume to 1 mL. Cover and label, and then send it to the liquid chromatography-mass spectrometry instrument for analysis, or seal it with a sealing film and store it in the refrigerator.

[0054] S18. Make up the volume, filter and bottle.

[0055] The chromatographic and mass spectrometric methods are as follows:

[0056] Chromatographic column: 2.6 μm F5 Column (LC Column 100*3.0 mm); Column temperature: 40 °C; Injection volume: 10 μL; Phase A is ammonium formate solution, and Phase B is chromatographically pure acetonitrile. The gradient elution process is listed in Table 1.

[0057] Table 1

[0058]

[0059]

[0060] Ionization mode: Atmospheric pressure electrospray ionization source (ESI), positive ion mode; Scanning type: Multiple reaction monitoring (MRM); Ion source temperature: 140 °C; Nitrogen flow rate: 0.12 mL / min; Single cycle time: 0.8401 sec; Number of cycles: 571 times; Period: 7.995 min; Single scan time: 0.8401 sec; Total ion count: 10891 (megaohm), and the monitored ions of the analyte are shown in Table 2.

[0061] Table 2

[0062]

[0063] As Figure 4 shown, the effect of the amount of Fe3O4@PS-TMG magnetic material on the extraction rate is presented. The amount of the magnetic material (Fe3O4@PS-TMG) used in this study was divided into five groups, namely 2 mg, 4 mg, 6 mg, 8 mg, and 10 mg. When the amount of the material gradually increased from 2 mg to 4 mg, the extraction rates of the four target substances generally increased gradually, and the extraction rates of two of the target substances approached 100% (parathion and fenitrothion), and the extraction rates of all four target substances were above 80%. Overall, its extraction efficiency is relatively high. For the blank group of the comparative example (i.e., without adding Fe3O4@PS-TMG magnetic material), its extraction efficiency was less than 10% (not shown in the figure).

[0064] From left to right are fenthion, parathion, phoxim, and fenitrothion.

[0065] As Figure 5 shown, 4 mg of Fe3O4@PS-TMG material was used as the adsorbent for magnetic solid-phase extraction, and four different organic solvents were used in the elution step. Acetonitrile, methanol, ethanol, and acetone were used as the elution solvents. Therefore, considering comprehensively, the extraction rate can reach more than 80% for various types of elution solvents. For the blank group of the comparative example (i.e., without adding Fe3O4@PS-TMG magnetic material), ultrasonic extraction was used, and its extraction efficiency was less than 10% (not specifically shown in the figure).

[0066] From left to right are fenthion, parathion, phoxim, and fenitrothion.

[0067] As Figure 6 shown, in this study, 4 mg of Fe3O4@PS-TMG material was used as the adsorbent. Therefore, in the ultrasonic extraction stage, the extraction time was adjusted from 5 min to 1 min, 2 min, 3 min, 4 min, 5 min, and 6 min. The results showed that the extraction effect on the target substances was the best when the extraction time was 4 min, and the extraction rates of the four target substances were more ideal than those of other groups, all reaching more than 60%.

[0068] From left to right are fenthion, parathion, phoxim, and phenthoate in turn.

[0069] As Figure 7 shown, for the reuse of Fe3O4@PS-TMG material: After 4 mg of Fe3O4@PS-TMG material was reused 6 times, the extraction effect on the four groups of target substances decreased slightly but the amplitude was very small, which can be considered as basically no change. The experiment shows that the feasibility of this exploration and the recovery rate of Fe3O4@PS-TMG material are both high, and it also shows that Fe3O4@PS-TMG material has great prospects in magnetic solid-phase extraction and the detection of organophosphorus pesticide residues.

[0070] After optimizing each parameter, magnetic solid-phase extraction was used to analyze three different water samples, namely well water, farmland water, and irrigation water. The three water samples were respectively prepared into spiked water samples with different concentrations under the same conditions (including water samples without organophosphorus pesticides), and then instrumental analysis was carried out at the same time and under the same conditions, and this experiment was repeated many times. Specifically, 20 mL of each of the three different water samples was taken and filtered, and then spiked water samples were prepared by adding 0 μg (not added), 0.1 μg (25 μL of a mixed standard solution of 4 μg / mL of four thiophosphates), and 10 μg (25 μL of a mixed standard solution of 40 μg / mL of four thiophosphates) of thiophosphates, and the experiment was carried out in combination with the optimal parameters. To verify the reproducibility and feasibility of the method, and to analyze the pollution situation of the three different water samples. As shown in Table 1 below.

[0071] Table 3

[0072]

[0073] The above table reflects the adsorption rates of the three water samples at spiked amounts of 5 μg / L and 50 μg / L. The experiment proves that when the spiked amount is 5 μg / L, the spiked recovery rates of the three water samples are between 99.1% and 108.69%. Although the extraction of different thiophosphates by water samples in different environments is slightly different, overall, the spiked recovery rate reflects that this method is actually feasible, and after multiple experiments, it is verified that this method has high accuracy and good reproducibility.

[0074] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. Preparation of a Fe3O4@PS-TMG material, characterized in that, It includes the following steps: S1. Prepare Fe3O4 magnetic fluid by coprecipitation method, and then dry it with anhydrous Na2SO4 for later use; S2. Prepare Fe3O4@Chloromethyl PS nanoparticles by miniemulsion polymerization method; S3. Subsequently, continue to add tetrahydrofuran, TMG, Bu4NI, and NaOH to the Fe3O4@Chloromethyl PS nanoparticles according to the molar ratio of 1:1:1:1:4, and carry out reflux reaction under the protection of nitrogen; S4. After the reaction is completed, freeze-dry to obtain Fe3O4@PS-TMG material.

2. Preparation of the Fe3O4@PS-TMG material according to claim 1, characterized in that, In S3, the reflux reaction time is 24 h.

3. The preparation of the Fe3O4@PS-TMG material according to claim 1, characterized in that, Before freeze-drying, wash with tetrahydrofuran and methanol in sequence.

4. The Fe3O4@PS-TMG material according to any one of claims 1-3, characterized in that, It is applied to the detection of organophosphorus pesticide residues.

5. The extraction and detection method of the Fe3O4@PS-TMG material according to claim 4, characterized in that, When the Fe3O4@PS-TMG material is used for the detection of organophosphorus pesticide residues, the extraction method for pretreatment includes the following steps: S11. Activation: Add the weighed Fe3O4@PS-TMG material to methanol and water with a volume ratio of 1:1 for activation, and then carry out ultrasonic treatment; S12. Primary magnetic separation: After the Fe3O4@PS-TMG material is activated, perform magnetic separation, and wait until the water sample is clarified before sampling; S13. Ultrasonic extraction: Then add the sample solution to be detected to the sampled liquid, and then carry out ultrasonic treatment again to make the Fe3O4@PS-TMG material fully adsorb the target analyte as a magnetic adsorbent; S14. Secondary magnetic separation: After ultrasonic treatment, perform magnetic separation on the sample again, and wait until the water sample is clarified before discarding the sample solution; S15. Elution: Perform elution after the liquid sample is completely absorbed; S16. Tertiary magnetic separation: After elution is completed, perform magnetic separation on the material, wait until the liquid sample is clarified, pour the eluate into a test tube, and collect the eluate for nitrogen blowing; S17. Nitrogen blowing: Make a constant volume of the nitrogen-blown eluate; S18. Constant volume, filtration and bottling.

6. The extraction and detection method of the Fe3O4@PS-TMG material according to claim 1, characterized in that, In S11, the activation time is 1 - 2 min.

7. The extraction and detection method of the Fe3O4@PS-TMG material according to claim 1, characterized in that, In S11, the ultrasonic time is 4 - 5 min.

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