Method for detecting pesticide residues based on fluorescent covalent organic polymer
By preparing fluorescent covalent organic polymers and plotting standard curves, the problems of high cost and complexity of existing trifluralin detection methods have been solved, achieving sensitive, convenient, and efficient detection of trifluralin, which is suitable for quantitative analysis in aqueous solutions.
Patent Information
- Application Number
- CN202511273992.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-08
- Publication Date
- 2025-11-28
AI Technical Summary
Existing methods for detecting fluroxypyr have limitations such as expensive instruments, complex operation, and poor portability, which restrict the development of real-time and on-site detection.
A method for detecting pesticide residues based on the preparation of fluorescent covalent organic polymers is proposed. The method includes preparing the fluorescent covalent organic polymer, plotting a standard curve, and performing sample detection.
It enables sensitive, convenient, and efficient detection of trifluralin, with a low detection limit (LOD=0.06µmol/L), and is suitable for quantitative detection in aqueous solutions.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of pesticide detection, and particularly relates to a method for detecting pesticide residues based on fluorescent covalent organic polymers. BACKGROUND
[0002] Pesticides are widely used in agricultural production to improve productivity and improve the quality of agricultural products. Among various pesticides, herbicides have become the most widely used class of pesticides in the world because they can control and change the phytosociological composition of weeds and have no negative impact on crop yield. Lontrel is a cheap and efficient general dinitroaniline herbicide suitable for almost all large-scale crops such as cotton, sugarcane, sunflower and soybean. Although Lontrel is listed as one of the five most dangerous pesticides, its global annual usage is estimated to be more than 4400 tons. Due to its mutagenicity and endocrine disrupting effects, the residues of Lontrel pose a serious threat to human health and the environment. Lontrel is relatively stable in chemical properties and can exist in soil, groundwater and rivers for a long time. Therefore, it is of great significance to monitor and detect excessive Lontrel residues in the environment for human health and safety.
[0003] At present, the detection methods of Lontrel mainly include chromatography-mass spectrometry, liquid nuclear magnetic resonance spectroscopy and electrochemical technology. However, these technologies usually have the shortcomings of expensive instruments, complex operation and poor portability, which hinder the further development of real-time and on-site detection. Therefore, it is particularly important to develop a simple and direct method to detect pesticide residues. SUMMARY
[0004] The purpose of the present application is to provide a method for detecting pesticide residues based on fluorescent covalent organic polymers, which solves the limitations in the current pesticide residue detection methods, including expensive instruments, complex operation and poor portability.
[0005] The method for detecting pesticide residues in an aqueous solution based on fluorescent covalent organic polymers according to the present application comprises the following steps: S1: using tetra-(ethylene-1,1,2,2-tetrayl) tetrakis(diphenyl-4-formaldehyde) and 4,4'-diamino-2,2'-bistrifluoromethyl diphenyl as raw materials, a fluorescent covalent organic polymer is prepared; S2: preparing Lontrel standard solutions with different concentrations, adding the prepared fluorescent covalent organic polymer to the standard solutions, taking the fluorescence intensity of the standard solution as the ordinate y and the concentration of Lontrel as the abscissa x, and drawing a standard curve y=ax+b, a and b being constants; S3: adding Lontrel to the liquid sample to be tested to prepare a spiked sample, determining the fluorescence intensity of the spiked sample and substituting it into the standard curve to obtain the concentration of Lontrel in the spiked sample.
[0006] The specific preparation method of the fluorescent covalent organic polymer in step S1 includes the following steps: (1) Take tetra-(ethylene-1,1,2,2-tetrayl) tetra(biphenyl-4-formaldehyde) (CAS: 1624970-54-2) and 4,4'-diamino-2,2'-bistrifluoromethyl biphenyl (CAS: 341-58-2) as the reaction raw materials; mix mesitylene, 1,4-dioxane and acetic acid solution to prepare a reaction solvent; dissolve the reaction raw materials in the reaction solvent, mix uniformly to prepare a mixed solution; The molar ratio of tetra-(ethylene-1,1,2,2-tetrayl) tetra(biphenyl-4-formaldehyde) and 4,4'-diamino-2,2'-bistrifluoromethyl biphenyl is 2:1; in the reaction solvent, the concentration of acetic acid solution is 6 M, and the volume ratio of mesitylene, 1,4-dioxane and acetic acid solution is (1-9):(1-9):1; for every 0.02 mmol-0.1 mmol of reaction raw materials, 1 mL-2 mL of reaction solvent is added.
[0007] (2) After the mixed solution is degassed, the reaction is carried out in a vacuum environment, the reaction temperature is 120℃-180℃, preferably 140℃-160℃; the reaction time is 48 h-96 h; after the reaction is completed, the solid phase separated is the fluorescent covalent organic polymer.
[0008] Step (2) includes the following specific contents: transfer the mixed solution to a Pyrex tube, cool the Pyrex tube containing the mixed solution to solidification in liquid nitrogen, then take out the Pyrex tube and thaw it at room temperature until the materials in the Pyrex tube become completely liquid, complete the first cooling-thawing degassing, repeat the above operation for a total of three times of cooling-thawing degassing; after the degassing of the Pyrex tube is completed, seal the top of the Pyrex tube with a flame and then carry out the reaction; After the reaction is completed, centrifugal separation is carried out to separate the solid phase, the centrifugal separation is carried out at a speed of 5000 r / min-6000 r / min for 5 min-10 min; the separated solid phase is washed with anhydrous tetrahydrofuran (THF) for three times, then washed with acetone for three times, and then vacuum dried to obtain the fluorescent covalent organic polymer.
[0009] The prepared fluorescent covalent organic polymer has an optimal emission wavelength of 530 nm, a maximum excitation wavelength of 420 nm, a stable fluorescence intensity in an aqueous solution for 140 min, and selectivity for trifluralin detection.
[0010] The standard curve in step S2 is: y=0.031x+0.305, R 2 =0.996, the molar concentration of trifluralin in the standard solution is 0.2 µM-100 µM, and the minimum detection limit is 0.06 µmol / L.
[0011] y is the treated fluorescence intensity, y=I0 / I-1, wherein I0 is the detected fluorescence intensity of the covalent organic polymer, and I is the detected fluorescence intensity of the standard solution or the spiked sample.
[0012] The concentration of the fluorescent covalent organic polymer in the standard solution or the spiked sample is 0.55 mg / mL.
[0013] The spiked concentration of trifluralin in the spiked sample in step S3 is 5 µM-60 µM, the recovery rate of the spiked sample is 97.80%-102.40%, and the relative standard deviation is less than 3.21%.
[0014] Compared with the prior art, the present application has the following beneficial effects: 1. The present application has the advantages of sensitivity, convenience, high efficiency, low cost, independence on professional inspectors, and no need for expensive instruments and equipment.
[0015] 2. The present application realizes the quantitative detection of trifluralin and has good linearity (R 2 >0.99) and a low detection limit (LOD=0.06 µmol / L) through the influence of trifluralin on the π-π stacking of the fluorescent covalent organic polymer layer and the fluorescence quenching phenomenon of the polymer. BRIEF DESCRIPTION OF DRAWINGS
[0016] Figure 1 FIG. 1 is a schematic diagram of the preparation process of the fluorescent covalent organic polymer of the present application; Figure 2 FIG. 2 is a three-dimensional fluorescence spectrum of the fluorescent covalent organic polymer of the present application; Figure 3 FIG. 3 is a fluorescence spectrum of the fluorescent covalent organic polymer of the present application during the dispersion process in water for 140 min; Figure 4 FIG. 4 is a selectivity diagram of the fluorescent covalent organic polymer of the present application to different drugs; Figure 5 FIG. 5 is a fluorescence spectrum of different concentrations of trifluralin standard solution containing the fluorescent covalent organic polymer; Figure 6 FIG. 6 is a standard curve diagram obtained by detecting different concentrations of trifluralin standard solution by the fluorescent covalent organic polymer. DETAILED DESCRIPTION
[0017] The technical solutions of the present application will be described clearly and completely in combination with the embodiments and the drawings. It should be noted that the embodiments described in the present application are only used to further explain and illustrate, but not to limit the application range. Based on the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.
[0018] The trifluralin, ciprofloxacin, enrofloxacin, norfloxacin, amoxicillin, streptozotocin, tetracycline, erythromycin, oxytetracycline, metronidazole used in the present application are purchased from Shanghai Aladdin Bio-Chem Technology Co., Ltd.
[0019] Example 1
[0020] Preparation of the fluorescent covalent organic polymer S1: (1) Take tetra-(vinyl-1,1,2,2-tetra radical) tetra(biphenyl-4-formaldehyde) and 4,4'-diamino-2,2'-bistrifluoromethyl biphenyl as the reaction raw materials, and the molar ratio is 2:1; mix mesitylene, 1,4-dioxane and acetic acid solution to prepare the reaction solvent, and the molar ratio is 1:9:1; dissolve the reaction raw materials in the reaction solvent, mix uniformly to prepare a mixed solution; (2) Cool the Pyrex tube containing the mixed solution to solidification in liquid nitrogen, then take out the Pyrex tube and thaw it at room temperature until the material in the Pyrex tube completely forms a liquid, complete the first cooling-thawing degassing, repeat the above operation, and the cooling-thawing degassing is repeated for three times; seal the top of the Pyrex tube with flame after completing the degassing; react at 120°C for 72h, and the reaction process is shown in Figure 1 ; and the product mixture is obtained after the reaction is completed; Centrifuge the product mixture at a speed of 6000r / min to separate out the solid phase, wash the solid phase with anhydrous THF for three times, then wash with acetone for three times, and then vacuum dry, to obtain the fluorescent covalent organic polymer after treatment.
[0021] S1-1 Determine the optimal emission wavelength and maximum excitation wavelength of the fluorescent covalent organic polymer: Weigh 5.5mg of the fluorescent covalent organic polymer, add 10ml of water, then ultrasonic, to obtain a uniformly dispersed aqueous solution of the fluorescent covalent organic polymer, and the concentration is 0.55mg / mL; take 200µL of the aqueous solution and add it into a fluorescence cuvette, and then use a fluorescence spectrometer to test. As shown in Figure 2 , the optimal emission wavelength of the fluorescent covalent organic polymer is 530nm, and the maximum excitation wavelength is 420nm. Therefore, the following emission spectrum is measured at an excitation wavelength of 420nm.
[0022] S1-2 Investigate the stability of the fluorescent covalent organic polymer: Take 100 μL of the above uniformly dispersed fluorescent covalent organic polymer aqueous solution, add 400 μL of water to prepare a mixed solution. After placing for 0, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, respectively, take 200 μL of the mixed solution placed for different times into a fluorescence cuvette to measure the fluorescence intensity. As shown in Figure 3 , the fluorescence intensity of the fluorescent covalent organic polymer does not change substantially during the 140 min of placement, proving that the substance has certain stability and can be used for subsequent research.
[0023] S1-3 investigates the selectivity of the fluorescent covalent organic polymer to trifluralin detection: Prepare drug solutions with a concentration of 10 mmol / L, and the drug types are as follows: ciprofloxacin, enrofloxacin, norfloxacin, amoxicillin, streptozotocin, tetracycline, erythromycin, terramycin, metronidazole, and trifluralin, corresponding to numbers 1-10. Take 100 μL of a dispersed solution of the fluorescent covalent organic polymer with a concentration of 0.55 mg / mL, and then take 400 μL of each of the above drug solutions and mix them uniformly to obtain control solutions of each drug. Take 400 μL of water to mix as a blank sample. Then take 200 μL of each drug control solution and the blank sample, and add them to a fluorescence cuvette to measure the fluorescence intensity of each solution. As shown in Figure 4 , compared with the blank sample, the fluorescence intensity of the control solutions of the other drugs changes slightly, and only the solution with trifluralin shows obvious fluorescence quenching. This shows that the fluorescent covalent organic polymer can selectively detect trifluralin and has good specificity.
[0024] S2 uses the fluorescent covalent organic polymer to detect trifluralin standard solution: Add trifluralin to a dispersed aqueous solution of the fluorescent covalent organic polymer with a concentration of 0.55 mg / mL, mix uniformly to obtain a standard solution of trifluralin with a concentration of 0.2 μM-100 μM, and then measure the fluorescence intensity of the standard solution. Figure 5 From top to bottom, the concentrations of trifluralin are 0.2 μM, 1 μM, 2 μM, 4 μM, 6 μM, 8 μM, 10 μM, 20 μM, 40 μM, 60 μM, 80 μM, and 100 μM, respectively. As the concentration of trifluralin increases, the fluorescence intensity gradually decreases, indicating that trifluralin has a good quenching effect on the fluorescent covalent organic polymer. I0 is the fluorescence intensity of the covalent organic polymer, I is the fluorescence intensity of the solution to be measured, and I0 / I-1 is the relative fluorescence intensity. As shown in Figure 6As shown, a standard curve is made with relative fluorescence intensity as the ordinate y and trifluralin molar concentration as the abscissa x: y=0.031x+0.305, and the curve R 2 The detection limit is 0.06 µmol / L, indicating that the fluorescent covalent organic polymer can quickly and sensitively detect trifluralin in an aqueous solution.
[0025] S3 The fluorescent covalent organic polymer is used for detection of trifluralin residues in actual samples: Laboratory tap water, Songhua River water and commercially available milk are selected as actual detection samples. The sample pretreatment method is as follows: 10 mL of laboratory tap water and 10 mL of Songhua River water are centrifuged at 8000 rpm for 5 min, 10 mL of commercially available milk is diluted 100 times with a PBS solution, and solid impurities are removed by using a 0.22 µm water filter membrane.
[0026] A trifluralin solution with a concentration of 1 mmol / L is prepared, 50 µL, 200 µL and 600 µL of the trifluralin solution is taken, 9.95 mL, 9.8 mL and 9.4 mL of the above-mentioned treated tap water detection sample is added respectively, and the mixture is uniformly mixed to prepare a tap water spiked sample, i.e. a tap water sample to be tested, the trifluralin concentration in the sample to be tested is 5 µM, 20 µM and 60 µM respectively. In the same way, Songhua River water samples to be tested and commercially available milk samples to be tested with trifluralin concentrations of 5 µM, 20 µM and 60 µM are prepared. 200 µL of each sample to be tested is taken in a fluorescence cuvette, the fluorescence intensity of the sample to be tested is measured, and the relative fluorescence intensity is converted into the standard curve to obtain the trifluralin concentration in the sample to be tested, and the results are shown in Table 1, the detection concentration column.
[0027] In order to verify the accuracy of the detection results, the sample to be tested is detected by using a gas chromatography-mass spectrometry instrument, and the obtained data are shown in Table 1. The recovery rate of the spiked sample is 97.80% to 102.40%, and the relative standard deviation (RSD) is less than 3.21%. It is proved that the method has certain sensitivity and can be used for detection of the concentration of trifluralin in an actual sample.
[0028] Table 1: Detection results of trifluralin residues in actual samples:
[0029] In summary, the method for detecting pesticide residues in an aqueous solution based on the fluorescent covalent organic polymer can realize quantitative detection of trifluralin in an aqueous solution by preparing a fluorescent covalent organic polymer. The detection method provided by the present application has the characteristics of sensitivity, high efficiency and low detection limit, and meets the requirements of pesticide residue analysis, and can provide effective detection technology support for the field of pesticide residue detection and supervision.
[0030] It will be obvious to a person skilled in the art that the application is not limited to the details of the foregoing exemplary embodiments and can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. The embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.
Claims
1. A method for detecting pesticide residues based on fluorescent covalent organic polymers, characterized in that, Includes the following: S1: A fluorescent covalent organic polymer was prepared using tetra-(ethylene-1,1,2,2-tetramethyl)tetra(biphenyl-4-carboxaldehyde) and 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl as reactants. S2: Prepare standard solutions of trifluralin at different concentrations, add the prepared fluorescent covalent organic polymer to the standard solutions, and plot the standard curve y=ax+b with the fluorescence intensity of the standard solution as the ordinate and the trifluralin concentration as the abscissa, where a and b are constants. S3: Add trifluralin to the liquid sample to be tested to prepare a spiked sample. Measure the fluorescence intensity of the spiked sample and substitute it into the standard curve to obtain the concentration of trifluralin in the spiked sample.
2. The method for detecting pesticide residues based on fluorescent covalent organic polymers according to claim 1, characterized in that, The fluorescent covalent organic polymer has an optimal emission wavelength of 530 nm and a maximum excitation wavelength of 420 nm. Its fluorescence intensity is stable in aqueous solution for 140 min, and it exhibits selectivity for the detection of trifluralin.
3. The method for detecting pesticide residues based on fluorescent covalent organic polymers according to claim 1, characterized in that, The preparation method of the fluorescent covalent organic polymer in step S1 is as follows: (1) Tetra-(ethylene-1,1,2,2-tetramethyl)tetra(biphenyl-4-carboxaldehyde) and 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl were used as reactants; a reaction solvent was prepared by mixing mesitylene, 1,4-dioxane and acetic acid solution; and a mixed solution was prepared from the reactants and the reaction solvent. (2) The mixed solution is reacted in a vacuum environment at a temperature of 120℃~180℃ for a time of 48h~96h; after the reaction, a fluorescent covalent organic polymer is obtained.
4. The method for detecting pesticide residues based on fluorescent covalent organic polymers according to claim 3, characterized in that, The reaction temperature in step (2) is 140℃~160℃.
5. The method for detecting pesticide residues based on fluorescent covalent organic polymers according to claim 3, characterized in that, Step (1) includes the following specific contents: The molar ratio of tetra-(ethylene-1,1,2,2-tetramethyl)tetra(biphenyl-4-carboxaldehyde) and 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl is 2:1; in the reaction solvent, the volume ratio of mesitylene, 1,4-dioxane and acetic acid solution is (1-9):(1-9):1; for every 0.02 mmol to 0.1 mmol of reaction raw material, 1 mL to 2 mL of reaction solvent is added accordingly.
6. The method for detecting pesticide residues based on fluorescent covalent organic polymers according to claim 3, characterized in that, Step (2) includes the following specific contents: The mixed solution is transferred to a Pyrex tube and cooled in liquid nitrogen until solidified. The Pyrex tube is then removed and thawed at room temperature until the material inside the Pyrex tube becomes completely liquid, completing one cooling-thawing degassing cycle. This process is repeated several times to complete the degassing. The degassed Pyrex tube is then sealed and the reaction proceeds.
7. The method for detecting pesticide residues based on fluorescent covalent organic polymers according to claim 3, characterized in that, After the reaction was completed, the solid phase was separated by centrifugation at a speed of 5000 r / min to 6000 r / min for 5 min to 10 min. The separated solid phase was washed with anhydrous tetrahydrofuran and acetone and dried under vacuum to obtain the fluorescent covalent organic polymer.
8. The method for detecting pesticide residues based on fluorescent covalent organic polymers according to claim 1, characterized in that, The standard curve mentioned in step S2 is: y = 0.031x + 0.305, and the limit of detection is 0.06 µmol / L.
9. The method for detecting pesticide residues based on fluorescent covalent organic polymers according to claim 8, characterized in that, y represents the fluorescence intensity after treatment, y = I0 / I-1; where I0 is the detection fluorescence intensity of the covalent organic polymer, and I is the detection fluorescence intensity of the standard solution or spiked sample.
10. The method for detecting pesticide residues based on fluorescent covalent organic polymers according to claim 8, characterized in that, The molar concentration of trifluralin in the standard solution was 0.2 µM–100 µM; the concentration of the fluorescent covalent organic polymer in the standard solution or spiked sample was 0.55 mg / mL; the spiked concentration of trifluralin in the spiked sample was 5 µM–60 µM; the recovery rate of the spiked sample was 98.40%–102.40%; and the relative standard deviation was less than 3.21%.