A trifluralin molecularly imprinted polymer and a preparation method thereof
By using 4-methyl-3,5-dinitrobenzoic acid as a template molecule, a trifluralin molecularly imprinted polymer was prepared, which solved the problems of low affinity and high preparation cost of trifluralin adsorbent materials in the prior art, and achieved high selectivity and high efficiency adsorption effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HENAN AGRICULTURAL UNIVERSITY
- Filing Date
- 2023-09-20
- Publication Date
- 2026-07-14
AI Technical Summary
Existing fluroxypyr adsorbents, such as activated carbon, have low affinity, lack specificity, and require stringent preparation conditions and are costly, making them difficult to effectively remove fluroxypyr residues from soil.
Using 4-methyl-3,5-dinitrobenzoic acid as the template molecule, N-vinylpyrrolidone as the functional monomer, and acetonitrile as the solvent, a trifluralin molecularly imprinted polymer was prepared by bulk polymerization to form three-dimensional imprinted cavities with defined shapes and recognition sites.
It improves the adsorption selectivity and adsorption capacity of trifluralin, reduces the preparation cost, avoids the risk of template residue leakage, and the material preparation is convenient and safe.
Smart Images
Figure CN117659278B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a fluroxypyr molecularly imprinted polymer and its preparation method, belonging to the field of polymer materials technology. Background Technology
[0002] Trifluralin, also known as Solanine, is a dinitroaniline herbicide with the chemical name 2,6-dinitro-N,N-di-n-propyl-4-trifluoromethylaniline. It is an orange-yellow crystalline solid with a melting point of 48.5℃, primarily used for controlling annual weeds and broadleaf weeds. It boasts advantages such as wide applicability, broad spectrum of weed control, strong selectivity, rapid effect, long-lasting effect, low dosage, and low cost. Statistics show that the utilization rate of herbicides is only 20%-30%, with 20%-70% remaining in the soil for extended periods, thus polluting soil, groundwater, and food crops. Trifluralin exhibits high to very high toxicity to both cold-water and warm-water fish; the LC50 values for rainbow trout, bluegill sunfish, and goldfish are 41, 58, and 145 ppb, respectively. Trifluralin can cause hematologic toxicity (anemia and methylhemoglobinemia) in rats, mice, and dogs, and has mild hepatotoxicity. Fluroxypyr enters the human body through oral, skin, and eye contact, increasing liver weight and methemoglobin levels. It exhibits weak cytotoxicity and genotoxicity against human lymphocytes, inducing genotoxicity by activating oxidative stress pathways and causing chromosomal damage. Selective adsorption of fluroxypyr is an effective method for its residue detection and removal; therefore, developing materials with selective adsorption capabilities for fluroxypyr has become an urgent priority.
[0003] Existing adsorbents for trifluralin are activated carbon, which has low affinity and lacks specificity. In practical applications, natural organic matter competes for adsorption sites, causing blockage of the activated carbon pores and a decrease in adsorption performance. Patent CN201810302158 discloses a method for separating and enriching trifluralin herbicide in soil, but this technology has some drawbacks, such as high preparation temperature (600℃), harsh conditions, high cost, and lack of selectivity in application. Molecularly imprinted polymers have been widely used as adsorbents for the highly selective separation of compounds in complex mixtures. For trifluralin, the main obstacle to preparing selective molecularly imprinted polymers is that this herbicide has limited recognition sites and a low melting point. When the preparation temperature exceeds the melting point, the molecular structure of trifluralin changes, making it difficult to form three-dimensional imprinted pores. Virtual template molecular imprinting technology involves complexing a dummy template with a functional monomer in solution, and then polymerizing it with an excess of crosslinking agent through covalent or non-covalent bonds to form a highly crosslinked polymer network. This technology can imprint templates that are difficult to bind with functional monomers, as well as expensive or environmentally polluting template molecules, expanding the application scope of molecular imprinting technology and improving the selectivity of molecularly imprinted polymers. Therefore, it can avoid the impact of trace leakage of residual templates, reduce experimental costs and difficulty, and improve experimental safety. As one of the core elements in preparing highly selective molecularly imprinted polymers, the similarity between the pseudo-template molecule and the target molecule, including molecular structure and spatial positions, and characteristic groups (such as amino, hydroxyl, carboxyl groups, and covalent electrons), determines the accuracy and selectivity of the recognition site. Therefore, those skilled in the art are dedicated to developing a method for preparing a molecularly imprinted polymer of trifluralin to overcome the shortcomings of the existing technology. Summary of the Invention
[0004] In view of this, the present invention aims to provide a molecularly imprinted polymer material selective for trifluralin. Another objective is to provide a method for its preparation.
[0005] To achieve the above objectives, the technical solution of the present invention is as follows:
[0006] The trifluralin molecularly imprinted polymer material is prepared by bulk polymerization using 4-methyl-3,5-dinitrobenzoic acid as the template molecule, N-vinylpyrrolidone as the functional monomer, and acetonitrile as the aprotic solvent.
[0007] The specific preparation method is as follows:
[0008] (1) Add 4-methyl-3,5-dinitrobenzoic acid, a structural analog of trifluralin, to an acetonitrile solution as a template molecule, sonicate it to dissolve it completely, add the functional monomer N-vinylpyrrolidone, stir, introduce an inert gas to remove oxygen, heat in a water bath, prepolymerize, then add the crosslinking agent ethylene glycol dimethacrylate, add the initiator azobisisobutyronitrile, and heat in a water bath for polymerization.
[0009] (2) The polymer prepared in step (1) is extracted in a Soxhlet extractor with an extractant of methanol and glacial acetic acid. The residual glacial acetic acid is washed away with methanol, and then the polymer is dried under vacuum and ground to obtain the molecularly imprinted polymer with selective recognition of trifluralin.
[0010] Furthermore, in step (1), the molar ratio of 4-methyl-3,5-dinitrobenzoic acid, N-vinylpyrrolidone, and ethylene glycol dimethacrylate is 1:4:16.
[0011] Furthermore, in step (1), azobisisobutyronitrile accounts for 5% of the mass ratio of N-vinylpyrrolidone and ethylene glycol dimethacrylate.
[0012] Furthermore, in step (2), the volume ratio of methanol to glacial acetic acid in the extract is 9:1.
[0013] Following the above method, without adding 4-methyl-3,5-dinitrobenzoic acid, the non-imprinted polymer (NIP) corresponding to this invention is prepared.
[0014] The innovation of this invention lies in utilizing the interaction between N-vinylpyrrolidone and 4-methyl-3,5-dinitrobenzoic acid, and the high melting point of 4-methyl-3,5-dinitrobenzoic acid, to form three-dimensional imprinted pores with defined shapes and recognition sites, thereby improving the adsorption selectivity for trifluralin. A molecularly imprinted polymer with uniform particle size and selectivity for trifluralin is synthesized using bulk polymerization.
[0015] Compared with the prior art, the present invention has the following advantages:
[0016] 1. This invention introduces 4-methyl-3,5-dinitrobenzoic acid, a structural analog of trifluralin, as a template molecule and a pseudo-template molecule to prepare a trifluralin molecularly imprinted polymer. This polymer is inexpensive and heat-resistant (melting point is 155-158℃). It contains functional groups (COOH) that readily form hydrogen bonds and exhibits good selective recognition ability, instantaneous adsorption performance, and high adsorption capacity for trifluralin.
[0017] 2. The molecularly imprinted polymer of trifluralin can be prepared using conventional bulk polymerization methods, avoiding the impact of trace leakage from residual templates, reducing experimental costs and difficulty, and improving experimental safety. Furthermore, compared to existing materials for adsorbing herbicides (such as activated carbon), this method offers advantages such as convenient material preparation, high selectivity, and ease of widespread application. Attached Figure Description
[0018] Figure 1 This is a schematic diagram illustrating the preparation of the molecularly imprinted material of the present invention.
[0019] Figure 2 These are scanning electron microscope images of the molecularly imprinted polymer (a) and the non-imprinted polymer (b) prepared in Embodiment 1 of the present invention.
[0020] Figure 3 These are Fourier transform infrared spectra of the molecularly imprinted polymer and the non-imprinted polymer prepared according to the present invention, wherein: a is a pseudo-template molecule, b is a molecularly imprinted polymer (template not extracted), c is a molecularly imprinted polymer, and d is a non-imprinted polymer.
[0021] Figure 4 This is an adsorption equilibrium diagram of the molecularly imprinted polymer prepared in an embodiment of the present invention.
[0022] Figure 5 The adsorption kinetics of the molecularly imprinted polymer prepared in the embodiments of the present invention.
[0023] Figure 6 The selective properties of the molecularly imprinted polymers prepared in the embodiments of the present invention. Detailed Implementation
[0024] To make the above features and advantages of the present invention clearer and easier to understand, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
[0025] The 4-methyl-3,5-dinitrobenzoic acid, N-vinylpyrrolidone, ethylene glycol dimethacrylate, azobisisobutyronitrile, acetonitrile, methanol, and glacial acetic acid mentioned in the following examples are all commercially available and have not been treated in any way before use.
[0026] Example 1
[0027] This invention provides a method for preparing a molecularly imprinted polymer of trifluralin, the specific preparation route being as follows: Figure 1 As shown:
[0028] (1) 0.5 mmol of 4-methyl-3,5-dinitrobenzoic acid was added to an acetonitrile solution as a template molecule and sonicated until fully dissolved. 2 mmol of the functional monomer N-vinylpyrrolidone was added, and the mixture was stirred for 1 h. An inert gas was introduced to remove oxygen for 5 minutes, and the mixture was prepolymerized in a water bath at 60 °C for 4 h. Then, 8 mmol of the crosslinking agent ethylene glycol dimethacrylate and 5% of the initiator azobisisobutyronitrile were added, and the mixture was polymerized in a water bath at 60 °C for 14 h to obtain a crude molecularly imprinted polymer. The obtained molecularly imprinted polymer was extracted with an extract of methanol and glacial acetic acid (volume ratio 9:1) in a Soxhlet extractor for 36 h. The residual glacial acetic acid was washed away with methanol, and the polymer was then vacuum dried at 60 °C for 12 h and ground to obtain a molecularly imprinted polymer with selective recognition of trifluralin.
[0029] Following the above method, without adding 4-methyl-3,5-dinitrobenzoic acid, the non-imprinted polymer corresponding to this invention is prepared.
[0030] To better understand the properties of the fluroxypyr molecularly imprinted polymer prepared in this invention, it was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy.
[0031] Figure 3 These are Fourier transform infrared spectra of molecularly imprinted polymers and non-imprinted polymers. Figure 3 In the image, a represents the infrared spectrum of 4-methyl-3,5-dinitrobenzoic acid, at cm⁻¹ 1349 and 1537. -1 It is a characteristic waveband caused by the symmetrical and antisymmetrical tensile vibrations of NO2. Figure 3 In the image, b, c, and d represent the infrared spectra of the molecularly imprinted polymer with and without template molecule removal, respectively. (1161, 1158, and 1159 cm⁻¹) -1 The spectral band is attributed to the stretching vibration of CN in vinylpyrrolidone, 1260 cm⁻¹ -1 This is a stretching vibrational band representing the vinylpyrrolidone ring skeleton. 2987 cm⁻¹ -1 The band at 2955 cm⁻¹ represents the methyl stretching vibration band. -1 The band at this location represents the methylene stretching vibration. Figure 3 Compared to b, c is 1537cm -1 The disappearance of the NO2 antisymmetric stretching vibration peak indicates that the template molecule has been removed. Molecularly imprinted polymers have been successfully prepared.
[0032] Figure 2 These are scanning electron microscope images of molecularly imprinted polymers and non-imprinted polymers, respectively. As can be seen from the images, both molecularly imprinted and non-imprinted polymers consist of large particles composed of small particles, with relatively regular shapes, uniform particle size, and numerous pores on their surfaces.
[0033] Example 2
[0034] Study the adsorption properties of this material (e.g.) Figure 4 (As shown). Weigh 5 mg of the molecularly imprinted polymer and 5 mg of the non-imprinted polymer prepared in Example 1 and add them to 1.5 mL of a container containing 40-200 μg / mL of different polymers. -1 The trifluralin standard solution was placed in a centrifuge tube. The mixture was shaken at room temperature for a period of time, then centrifuged at 5000 rpm for 10 min. The concentration of trifluralin not adsorbed by the material in the supernatant was then detected using high-performance liquid chromatography (HPLC). The concentration of trifluralin was calculated based on the standard curve, and finally, the adsorption capacity was calculated. Figure 5As can be seen, with increasing trifluralin concentration, the adsorption capacity of both molecularly imprinted and non-imprinted polymers increases, and at the same concentration, the adsorption capacity of the molecularly imprinted polymer is higher than that of the non-imprinted polymer. (At 150 μg / mL...) -1 In a trifluralin solution, the adsorption capacities of the molecularly imprinted polymer and the non-imprinted polymer were 5.0 mg g and 5.0 mg g, respectively. -1 and 2.3mg g -1 The adsorption capacity of molecularly imprinted polymers is 2.2 times that of non-imprinted polymers, indicating that molecularly imprinted polymers have a high specific recognition ability for analytes.
[0035] Example 3
[0036] The kinetic properties of the adsorbent were investigated. 5 mg of the molecularly imprinted polymer and 5 mg of the non-imprinted polymer prepared in Example 1 were weighed and placed in separate centrifuge tubes, and then 1.5 mL of 150 μg / mL solution was added. -1 The trifluralin solution was incubated with shaking at room temperature for 0-11 hours, followed by centrifugation at 5000 rpm for 10 minutes. The concentration of unbound trifluralin in the supernatant was then determined using high-performance liquid chromatography (HPLC). The concentration of trifluralin was calculated based on the standard curve, and finally, the adsorption capacity was calculated. Figure 5 As shown, the adsorption of trifluralin by molecularly imprinted polymers and non-imprinted polymers reaches instantaneous adsorption equilibrium, and molecularly imprinted polymers exhibit rapid kinetic adsorption of trifluralin.
[0037] Example 4
[0038] 2,4-Dinitroaniline, furazolidone, nitrofurantoin, nitrofurantoin, carbendazim, thiabendazole, and methyl thiophanate were selected as competitors to trifluralin to study the selectivity of the molecularly imprinted material. Single-standard solutions of 2,4-dinitroaniline, furazolidone, nitrofurantoin, carbendazim, thiabendazole, methyl thiophanate, and trifluralin were prepared at concentrations of 150 μg mL⁻¹. 5 mg of the molecularly imprinted material and non-imprinted material prepared in Example 1 were added to 1.5 mL of the prepared solutions, and the mixture was shaken at room temperature for a period of time, then centrifuged at 5000 rpm for 10 min. The concentrations of unbound trifluralin and competitors in the supernatant were then detected using high-performance liquid chromatography (HPLC). The concentrations of trifluralin and competitors were calculated based on the standard curve, and finally, the adsorption capacity was calculated. Figure 6 As shown, the molecularly imprinted polymer exhibits selective recognition of trifluralin.
[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A trifluralin molecularly imprinted polymer, characterized in that, It is prepared through the following steps: (1) 4-methyl-3,5-dinitrobenzoic acid was added to acetonitrile solution as template molecule and sonicated to dissolve it completely. The functional monomer N-vinylpyrrolidone was added, stirred, and an inert gas was introduced to remove oxygen. The mixture was heated in a water bath for prepolymerization. Then, the crosslinking agent ethylene glycol dimethacrylate and the initiator azobisisobutyronitrile were added and the mixture was heated in a water bath for polymerization. (2) The polymer prepared in step (1) was extracted in a Soxhlet extractor with an extract of methanol and glacial acetic acid. The residual glacial acetic acid was washed away with methanol, and then the polymer was dried under vacuum and ground to obtain the target product.
2. The fluroxypyr molecularly imprinted polymer according to claim 1, characterized in that, In step (1), the molar ratio of 4-methyl-3,5-dinitrobenzoic acid, N-vinylpyrrolidone, and ethylene glycol dimethacrylate is 1:4:
16.
3. The fluroxypyr molecularly imprinted polymer according to claim 1, characterized in that, In step (1), azobisisobutyronitrile accounts for 5% of the mass ratio of N-vinylpyrrolidone and ethylene glycol dimethacrylate.