Preparation method of magnetic nanocomposite and application of magnetic nanocomposite in enriching trace quinolones

Abstract

The application discloses a preparation method of a magnetic nanocomposite and application of the magnetic nanocomposite in enriching trace quinolones, and belongs to the technical field of nanomaterials and environmental monitoring. In the application, amino carbon nanotubes and fluorinated carbon nanotubes are used as functional monomers, mixed with iron-containing materials, and a magnetic nanocomposite is prepared through a hydrothermal method. The MNC prepared through double functionalization of amino groups and fluorine groups realizes efficient and high-selectivity capture of FQs. The material shows a lower detection limit and a higher adsorption capacity than existing materials. The one-pot method is used to prepare the MNC, the preparation process is simple and the cost is low, the use of expensive materials is reduced, the use amount of organic solvents is reduced, the detection cost is reduced, the influence on the environment is also reduced, and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nanomaterials and environmental monitoring, and particularly relates to a preparation method of a magnetic nanocomposite material and application thereof in enriching trace quinolones. BACKGROUND

[0002] In the field of environmental monitoring, especially for the detection of trace pollutants in environmental water, the existing technologies mainly include liquid chromatography mass spectrometry (LCMS), high-performance liquid chromatography (HPLC), and various solid phase extraction (SPE) techniques. These technologies have played an important role in detecting drug residues in environmental water, especially quinolone (FQs) antibiotics.

[0003] Although these methods have high sensitivity and good separation effect, they usually require complex sample pretreatment processes, tedious operation steps, and long time consumption. In addition, certain technologies such as LCMS equipment have high cost and expensive running cost, which limits their widespread application in routine environmental monitoring.

[0004] Current solid phase extraction techniques, although can effectively enrich target compounds in samples, to a certain extent, improve the detection sensitivity, but still have problems such as insufficient selectivity of adsorbents, extraction efficiency needs to be improved, and complex operation process. For example, traditional SPE methods often require the use of a large amount of organic solvent, which is not environmentally friendly. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a preparation method of a magnetic nanocomposite material and application thereof in enriching trace quinolones. The magnetic nanocomposite material of the present application is a magnetic nanocomposite material (MNC) based on aminated and fluorinated carbon nanotubes. It can quickly and efficiently enrich quinolones from environmental water, simplify the operation process, reduce the use of organic solvents, and has better environmental friendliness and economic benefits. The development of this new material provides a new idea and method for solving the problems in the prior art.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] The present application provides a preparation method of a magnetic nanocomposite material. Aminated carbon nanotubes and fluorinated carbon nanotubes are used as functional monomers, mixed with iron-containing materials, and a magnetic nanocomposite material is prepared by a hydrothermal method.

[0008] Furthermore, the mass ratio of the amino-treated carbon nanotubes to the fluorinated carbon nanotubes is (1-2):(1-2), preferably the mass ratio of the amino-treated carbon nanotubes to the fluorinated carbon nanotubes is 1:1, 2:1 or 1:2, more preferably 1:1.

[0009] Furthermore, the iron-containing material is a mixture of a divalent iron compound and a trivalent iron compound.

[0010] Furthermore, the divalent iron compound is FeCl2·4H2O, and the trivalent iron compound is FeCl3·6H2O.

[0011] Furthermore, the mass ratio of FeCl2·4H2O to FeCl3·6H2O is 2:1. 3+ (from FeCl3·6H2O) acts primarily as an oxidant in chemical reactions and can be reduced to Fe in some cases 2+ , or directly form oxides such as Fe3O4. 2+ (from FeCl2·4H2O) is usually oxidized and participates in the reaction of forming magnetic oxides such as Fe3O4 (magnetite). 2+ with Fe 3+ In a coexisting system, they can directly form Fe3O4 through a process called coprecipitation. Fe3O4 is a soft magnetic material with high saturation magnetization and low coercivity (Hc). 2+ with Fe 3+ The ratio of Fe3O4 to Fe3O4 can be adjusted to a certain extent. 2+ with Fe 3+ The ratio affects the structure of the final composite material. 2+ with Fe 3+ The higher the ratio, the more uniform the Fe3O4 particles formed may be, which is crucial for improving the efficiency of the material in catalysis, adsorption, etc. Therefore, the present invention limits the mass ratio of FeCl2·4H2O and FeCl3·6H2O to 2:1, which can greatly increase the enrichment effect of the composite material.

[0012] Furthermore, ethylenediamine was added during the hydrothermal preparation process to adjust the solution pH to 9.0-10.0, thereby optimizing the conversion process of iron ions into magnetic iron oxide (Fe3O4).

[0013] Furthermore, the hydrothermal temperature is 180° C., and the hydrothermal time is 12 h.

[0014] Furthermore, the preparation method of the magnetic nanocomposite material is:

[0015] Under the protection of nitrogen (to prevent oxidation reaction), 0.15 g of FCNs, 0.15 g of ACNs, 1.0 g of FeCl3·6H2O and 1.5 g of FeCl2·4H2O were uniformly dispersed in 100 mL of 50% (volume fraction) isopropanol (i.e. the mass ratio of ACNs to FCNs was 1:1, and the mass ratio of Fe 2+ and Fe 3+ was 1:2), and stirred at 300 r / min at 80℃ for 2 h to ensure that the components were fully mixed, thereby creating a uniform reaction environment for the subsequent synthesis reaction.

[0016] Ethylene diamine was added to the above mixture to control the pH value of the solution to 9.5, thereby promoting the conversion of iron salts to iron oxide. The mixture was then transferred to a hydrothermal reaction kettle, sealed, and reacted at 180℃ for 12 h to promote the reaction of ACNs and FCNs with iron salts to form a nanocomposite material with a magnetic core and a functionalized shell. After the reaction was completed, the nanocomposite material was separated from the reaction mixture using an external magnetic field, and washed with water and methanol to remove unreacted substances and possible impurities. The washed nanocomposite material was dried at 70℃ for 1 h to obtain the final magnetic nanocomposite material (MNC).

[0017] The method of the present application is simple to operate, has mild reaction conditions, and can directly obtain a functionalized magnetic nanocomposite material in a single reaction step. This material, due to the combination of its magnetic properties and functionality (from the amino-functionalization and fluorinated carbon nanotubes), is suitable for a variety of applications, such as the adsorption and separation of pollutants.

[0018] The present application also provides a magnetic nanocomposite material prepared by the above method.

[0019] The present application also provides the use of the magnetic nanocomposite material in the enrichment of trace quinolones, for example, the magnetic nanocomposite material can enrich norfloxacin, flumequine, danofloxacin, enrofloxacin or sarafloxacin.

[0020] Patent application CN 111426767 A discloses a magnetic nanocomposite material, its preparation, and its application in food testing. The patent uses carboxylated multi-walled carbon nanotubes, silica, and chitosan to prepare the magnetic nanocomposite material. These materials are combined through specific chemical treatment steps (e.g., using chitosan as an organic modifier) ​​to increase affinity for specific antibiotics. The patent focuses on the detection of quinolone antibiotics in food, particularly honey and milk, indicating that the method targets specific needs in the field of food safety. The present invention, on the other hand, aims to achieve efficient adsorption and facilitate rapid capture of pollutants from environmental samples. It is suitable for a wide range of pollutant detection in environmental samples and is more versatile, not limited to quinolone antibiotics or specific types of samples. The patent also utilizes a combination of ionic liquid dispersed liquid-liquid microextraction (DLLME) and magnetic solid-phase extraction (MSPE) in conjunction with ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS / MS), emphasizing high sensitivity and selective detection of specific target analytes. The present invention, however, uses MSPE as the primary technique, in conjunction with high-performance liquid chromatography or other suitable detection techniques, aiming to provide a more universal and broadly applicable method for detecting different types of pollutants. In summary, the method of patent application CN 111426767 A has clear advantages in the field of food safety monitoring, while the MNC / MSPE technology provided by the present invention is more suitable for a wide range of environmental monitoring applications.

[0021] The advantages of using MNC in MSPE and HPLC include: high efficiency. The use of MNC greatly simplifies the sample pretreatment process and improves the capture efficiency and detection sensitivity of FQs. Rapidity. Through the rapid magnetic separation and simple elution steps of MNC, the entire MSPE process time is shortened, speeding up sample processing. Accuracy. Combining the high separation capability of HPLC and the high sensitivity of FD detection, accurate quantification of FQs can be achieved, making it suitable for the analysis of complex water samples. Environmental friendliness. The preparation of MNC and the MSPE process reduce the use of organic solvents, conforming to the principles of green chemistry.

[0022] When using the magnetic nanocomposite to enrich trace quinolones, the optimal dosage of MNC is 40 mg, the optimal elution solvent is 0.50 mL of an ACN / FA (98 / 2.0, volume ratio) mixture, the optimal adsorption time is 8.0 min, the optimal desorption time is 4.0 min, the optimal solution pH is 6.0, and the optimal ionic strength is the addition of 0.020% (weight / volume ratio) NaCl.

[0023] The present invention also provides a surface molecular imprinted polymer containing the magnetic nanocomposite material, wherein the template molecule is norfloxacin, norfloxacin, danoxacin, enrofloxacin or sarafloxacin.

[0024] Compared with the prior art, the present application has the following advantages and technical effects:

[0025] (1) In the traditional method, the preparation of similar magnetic nanomaterials usually requires multiple steps, each of which may involve complex chemical reactions and tedious post-treatment (such as multiple washing and separation). The present application greatly simplifies the preparation process by one-pot method, which puts all the reaction precursors (including iron salt and carbon nanotubes) into the reaction solvent at the same time, and directly reacts to generate the final product under certain temperature and pH conditions.

[0026] (2) The MNC prepared by the dual functionalization of amino and fluorine groups in the present application realizes efficient and highly selective capture of FQs. The material exhibits lower detection limit and higher adsorption capacity than existing materials. The present application uses one-pot method to prepare MNC, which is simple and low-cost, reduces the use of expensive materials, reduces the amount of organic solvent used, reduces the detection cost, and also reduces the impact on the environment.

[0027] (3) The present application improves the repeatability of preparation and the stability of batch production. In the traditional method, multi-step reactions may cause large differences in product performance between different batches. One-pot method is simple and fast, which helps to improve the consistency of product batches, which is particularly important for commercial production.

[0028] (4) The present application can optimize the adsorption performance of the magnetic nanocomposite to the target pollutants by adjusting the ratio of aminated and fluorinated carbon nanotubes. This regulation ability is realized directly by changing the ratio of reactants without additional chemical modification steps.

[0029] (5) The method of the present application shows lower detection limit (detection limit is 0.18 ng / L-0.61 ng / L) and high precision (RSDs is 2.5-9.7%), which proves the superior sensitivity and reliability of the magnetic nanocomposite of the present application.

[0030] (6) The recovery rate of the present application is 82.3-112%, which indicates the accuracy and effectiveness of the present application method in different water samples. Combined with the high separation ability of HPLC and the high sensitivity detection of FD, the present application method can provide high-accuracy FQs concentration results, which is suitable for the analysis of various environmental water samples. BRIEF DESCRIPTION OF DRAWINGS

[0031] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments illustrated in the drawings, and their description, are used to explain the application and are not intended to limit the application unduly.

[0032] Figure 1 is a schematic diagram for the preparation of the magnetic nanocomposite of the present application;

[0033] Figure 2 For different mass ratios of FCNs and ACNs, different Fe 2+ and Fe 3+ The enrichment results of five antibiotic pollutants (NOR, FLX, DAN, ENR, SAR) prepared by magnetic nanocomposites with different mass ratios, where a is the different mass ratios of FCNs and ACNs, b is the different Fe 2+ and Fe 3+ mass ratio;

[0034] Figure 3 FT-IR spectrum, TEM image, magnetization curve and Zeta potential at different pH values ​​of the MNC prepared in Example 1, where a is the FTIR spectrum, b is the TEM image, c is the magnetization curve, and d is the Zeta potential at different pH values;

[0035] Figure 4 Transmission electron microscopy (TEM) image of the magnetic nanocomposite (MNC) prepared in Example 1;

[0036] Figure 5 Schematic diagram of the aggregation of MNC nanoparticles in Example 1 dispersed in the recovery solution;

[0037] Figure 6 is the adsorption kinetic curve of FLX by MNC / MSPE (MNC was prepared in Example 1);

[0038] Figure 7 is the static adsorption curve of LX on MNC / MSPE (MNC was prepared in Example 1);

[0039] Figure 8 The effects of different factors on the adsorption performance, where a is the amount of MNC, b is the FA content, c is the adsorption time, d is the elution time, e is the solution pH, and f is the amount of NaCl added;

[0040] Figure 9 Chromatograms obtained using high performance liquid chromatography diode array detector (HPLC / DAD); a is the peak of FQs before enrichment, and b is the peak of FQs after MNC / MSPE enrichment.

[0041] Figure 10 This is a study on the service life of the magnetic nanocomposite material (MNC) in Example 1. DETAILED DESCRIPTION

[0042] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0043] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of, for example, concentration, intensity, and time, and the like, every intermediate value of the upper and lower limits of that range is also specifically disclosed. Each smaller range of values within the range of values is also specifically disclosed. The upper and lower limits of these smaller ranges of values can independently be included or excluded in the range.

[0044] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice of the present application, the preferred methods and materials are described herein. All patents, patent applications, publications, and descriptions mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the patents, patent applications, publications, and descriptions are cited.

[0045] Many modifications and variations of this application of the present application can be made without departing from its spirit or scope, which will be apparent to those skilled in the art. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only. It is to be understood that the application is not limited in scope by the specific embodiments described herein. Rather, the intent is to embrace all changes and modifications that are within the spirit and scope of the application.

[0046] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional elements or steps.

[0047] Unless otherwise specified, the room temperature in the embodiments of the present application is 25±2°C.

[0048] All the raw materials used in the present application were obtained by commercial purchase. As an example, fluorinated carbon nanotubes (FCNs, purity > 98%) and aminated carbon nanotubes (ACNs, purity > 98%) were purchased from Nanjing Xianfeng Nanometer Co., Ltd.; ethylenediamine (purity > 99%), isopropanol (purity > 99.7%), formic acid (FA), and ferric chloride hexahydrate (FeCl3·6H2O, purity 99%) and ferrous chloride tetrahydrate (FeCl2·4H2O, purity 98%) were purchased from Guangzhou Xilong Chemical Co., Ltd.; HPLC-grade acetonitrile (ACN) and methanol were purchased from Tedia Company (USA). Ultra-pure water was prepared using a MilliQ water purification system from Millipore. Norfloxacin (NOR), flumequine (FLX), danofloxacin (DAN), enrofloxacin (ENR), and sarafloxacin (SAR) were purchased from China Institute for Drug Control. A 0.5% FA aqueous solution was purchased from Xilon Chemical Co. Ltd. (Guangzhou, China). Individual standard solutions of each analyte were prepared at a concentration of 10.0 mg / L in methanol and stored at 4°C. The desired FQs concentrations were prepared by diluting the standard solutions with ultra-pure water.

[0049] The instrument and chromatographic parameters are as follows:

[0050] Chromatographic analysis of FQs was performed on a Shimadzu LC-20AB chromatographic system, which included a Rheodyne 7725i high-pressure six-way valve, a quaternary pump (LC-20AB Quat Pump), and an RF-20A fluorescence detector. The analytes were separated using a Thermo C18 chromatographic column (5 μm particle size, 250 mm x 4.6 mm i.d.). The mobile phase consisted of acetonitrile (solvent A) and 0.5% (v / v) formic acid aqueous solution (solvent B). Gradient elution was used, starting with 82% solvent B for 5 min, then linearly decreasing to 70% B in 1 min, and maintaining until 10.5 min; after that, it was raised to 82% B in 1 min, and maintained until 14 min. The excitation wavelength for fluorescence detection was set at 280 nm and 450 nm. The flow rate and injection volume were 1.0 mL / min and 20 μL, respectively. High-performance liquid chromatography-fluorescence detection (HPLC-FD) analysis was performed at room temperature.

[0051] The morphology, microstructure, and surface properties of the prepared MNCs were examined using various characterization methods, such as elemental analysis (EA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), energy dispersive spectroscopy (EDS), Zeta potential analyzer, and Brunauer-Emmett-Teller (BET) specific surface area analysis. A SHZ-82 shaker from Jiangsu was used to perform the magnetic solid-phase extraction (MSPE) process.

[0052] The technical solution of the present invention is further illustrated by the following examples.

[0053] Example 1

[0054] Under nitrogen protection, 0.15 g FCNs, 0.15 g ACNs, 1.0 g FeCl3·6H2O and 1.5 g FeCl2·4H2O were uniformly dispersed in 100 mL of 50% (volume fraction) isopropanol (i.e., the mass ratio of ACNs to FCNs in this embodiment was 1:1, FeCl3·6H2O was 1:1, and FeCl2·4H2O was 1:1). 2+ and Fe 3+ The mass ratio of Fe is 2:1, 2+ The concentration is 2.0mmol / L, Fe 3+ The mixture was stirred at 300 rpm for 2 h at 80 °C to ensure that all components were fully mixed and to obtain a mixture, thereby creating a uniform reaction environment for the subsequent synthesis reaction.

[0055] Ethylenediamine was added to the mixture to control the pH of the solution to 9.5, promoting the conversion of the iron salt to iron oxide. The mixture was then transferred to a hydrothermal reactor, sealed, and reacted at 180°C for 12 hours. This allowed the ACNs and FCNs to react with the iron salt, forming a nanocomposite with a magnetic core and a functionalized shell. After the reaction, the nanocomposite was separated from the reaction mixture using an external magnetic field and washed with water and methanol to remove unreacted materials and possible impurities. The washed nanocomposite was dried at 70°C for 1 hour to obtain the final magnetic nanocomposite (MNC). The dried MNC should be stored at low temperature (4°C), away from light, in a dry, vibration-proof environment to avoid moisture and contamination to maintain its activity and stability.

[0056] The C, H, and N contents of the prepared MNC were determined by EA, with the results showing that the relevant contents were 18.6%, 5.3%, and 2.6% (w / w), respectively. The O and Fe contents of the MNC were determined by EDS, with the results showing that they were 20.2% and 50.6%, respectively.

[0057] In this example, a magnetic nanocomposite composed of carbon nanotubes (CNTs) (aminated and fluorinated) and iron oxide was prepared. An experiment to enrich trace amounts of quinolones was conducted. The following method was used: 50 mg of the CNTs (MNCs) was added to a 500 mL water sample containing five quinolones (norfloxacin (NOR), fluxicin (FLX), danoxacin (DAN), enrofloxacin (ENR), and sarafloxacin (SAR)). The mixture was stirred on a magnetic stirrer for 30 minutes to allow the MNCs to bind to the quinolones in the water sample. The MNCs were then separated from the water sample using magnetic separation and washed with deionized water to remove any unbound substances. The MNCs, which had adsorbed the quinolones, were then added to 10 mL of a 0.1 M hydrochloric acid solution containing 5% methanol. The mixture was stirred on a magnetic stirrer for 30 minutes at room temperature to desorb the quinolones from the MNCs. MNCs were collected by magnetic separation, and the supernatant was removed and collected for analysis by high-performance liquid chromatography with a diode array detector (HPLC / DAD). The extracts were analyzed using a fluorescence spectrophotometer, and the limit of detection (LOD) and recovery were recorded.

[0058] The experimental results showed that the detection limit (LOD) was approximately 1 ng / L, and the recovery rate was between 80% and 90%. Specifically, the LOD of NOR was 0.22 ng / L, and the recovery rate was 83%; the LOD of FLX was 0.20 ng / L, and the recovery rate was 87%; the LOD of DAN was 0.54 ng / L, and the recovery rate was 85%; the LOD of ENR was 0.54 ng / L, and the recovery rate was 86%; and the LOD of SAR was 0.61 ng / L, and the recovery rate was 86%.

[0059] Experiments have demonstrated the remarkable effectiveness of the dual-carbon nanotube magnetic nanocomposite in enriching trace quinolones. Its superior performance is attributed to the synergistic effect of the dual-carbon nanotubes, which provide more binding sites and higher surface activity, enabling it to effectively capture and enrich trace quinolones.

[0060] Double carbon nanotube magnetic nanocomposites exhibit superior performance in enriching trace quinolones and are suitable for trace pollutant detection and environmental monitoring.

[0061] Example 2

[0062] The same as Example 1, except that the amount of ACNs added is 0.3 g, that is, the mass ratio of ACNs to FCNs in this example is 2:1.

[0063] Example 3

[0064] The same as Example 1, except that the amount of FCNs added is 0.3 g, that is, the mass ratio of ACNs to FCNs in this example is 1:2.

[0065] Comparative Example 1

[0066] The same as Example 1, except that the amount of FCNs added was 0.45 g, that is, the mass ratio of FCNs to ACNs in this comparative example was 3:0, and no ACNs was added when preparing the magnetic nanocomposite material.

[0067] Comparative Example 2

[0068] The same as Example 1, except that the amount of ACNs added was 0.45 g, that is, the mass ratio of FCNs to ACNs in this comparative example was 0:3, and no FCNs was added when preparing the magnetic nanocomposite material.

[0069] Comparative Example 3

[0070] Same as Example 1, except that Fe 2+ and Fe 3+ The mass ratio of Fe is 1:1, that is, Fe 2+ The concentration is 1.0mmol / L.

[0071] Comparative Example 4

[0072] Same as Example 1, except that Fe 2+ and Fe 3+ The mass ratio of Fe is 1.5:1, 2+ The concentration is 1.5mmol / L.

[0073] Comparative Example 5

[0074] Same as Example 1, except that Fe 2+ and Fe 3+ The mass ratio of Fe is 2.5:1, 2+ The concentration is 2.5mmol / L.

[0075] Comparative Example 6

[0076] Same as Example 1, except that Fe 2+ and Fe 3+ The mass ratio of Fe is 3:1, 2+ The concentration is 3.0mmol / L.

[0077] Comparative Example 7 Preparation of Aminated Carbon Nanotubes and Iron Oxide

[0078] 1. Acid treatment of carbon nanotubes:

[0079] 1.0 g of carbon nanotubes was added to 500 mL of 68% (mass fraction) nitric acid solution, refluxed at 100° C. for 12 hours, cooled to room temperature, washed with deionized water to a neutral pH, and dried at 60° C. for 12 hours.

[0080] 2. Amino-functionalization:

[0081] The step 1 treated carbon nanotubes were dispersed in 100 mL of 25% (mass fraction, the same below) ammonia water, and stirred at 80°C for 24 hours. After the reaction, the solid was separated by centrifugation, washed with deionized water until neutral, and dried at 60°C for 12 hours to obtain the amino-functionalized carbon nanotubes.

[0082] 3. Iron oxide loading:

[0083] 2.0 grams of ferric chloride and 1.0 gram of ferrous chloride were dissolved in 200 mL of deionized water to obtain a ferric salt solution. The amino-functionalized carbon nanotubes were added to the ferric salt solution, and 25% ammonia water was added to adjust the pH of the solution to 10. The solution was stirred at 90°C for 4 hours. After the reaction, the solid was collected by magnetic separation, the supernatant was removed, and the precipitate was washed with deionized water and methanol. Finally, the composite material was dried at 60°C for 12 hours to obtain the amino-functionalized carbon nanotube loaded iron oxide (Fe3O4).

[0084] In this comparative example, a composite material containing only amino-functionalized carbon nanotubes and iron oxide was prepared to enrich trace quinolones. The experimental method was the same as in Example 1. The experimental results showed that the detection limit (LOD) was about 10 ng / L, and the recovery rate was between 50% and 60%. Specifically, the LOD of NOR was 10.1 ng / L, and the recovery rate was 53%; the LOD of FLX was 10.4 ng / L, and the recovery rate was 55%; the LOD of DAN was 10.2 ng / L, and the recovery rate was 54%; the LOD of ENR was 10.3 ng / L, and the recovery rate was 52%; and the LOD of SAR was 10.6 ng / L, and the recovery rate was 56%, which was significantly lower than the double carbon nanotube composite material in Example 1.

[0085] Effect analysis: Although the material in this comparative example showed a certain adsorption capacity, its enrichment effect was not as good as the composite material using both amino-functionalized carbon nanotubes and fluorinated carbon nanotubes in Example 1. This may be due to the insufficient surface activity and functionality of a single type of carbon nanotube, which cannot provide enough binding sites to effectively capture trace quinolones.

[0086] Preparation of fluorinated carbon nanotubes and iron oxide in Comparative Example 8

[0087] 1. Fluorination of carbon nanotubes:

[0088] 1.0 gram of carbon nanotubes was mixed with 100 mL of 48% (mass fraction) hydrogen fluoride acid at room temperature for 2 hours. Deionized water was used for washing until the washing liquid was neutral, and the fluorinated carbon nanotubes were dried at 80°C for 10 hours.

[0089] 2. Synthesis and loading of iron oxide:

[0090] The iron salt solution was prepared by dissolving 2.0 g of ferric chloride and 1.0 g of ferrous chloride in 200 mL of deionized water and mixing well. The fluorinated carbon nanotubes were added to the iron salt solution, 50 mL of 25% ammonia water was added to adjust the pH of the solution to 9, and the solution was reacted at 85°C for 6 hours with stirring. The solid was collected using magnetic separation, the supernatant was removed, the precipitate was washed with deionized water and methanol, and the precipitate was dried at 70°C for 12 hours. The obtained composite material was fluorinated carbon nanotube loaded iron oxide (Fe3O4).

[0091] In the present comparative example, a composite material containing only fluorinated carbon nanotubes and iron oxide was prepared, and an experiment of enriching trace quinolones was performed according to the method of Example 1. The experimental results show that the detection limit (LOD) is about 15 ng / L, and the recovery rate is between 40% and 50%, specifically, the LOD of NOR is 15.1 ng / L, and the recovery rate is 44%; the LOD of FLX is 15.3 ng / L, and the recovery rate is 48%; the LOD of DAN is 15.2 ng / L, and the recovery rate is 46%; the LOD of ENR is 15.4 ng / L, and the recovery rate is 45%; and the LOD of SAR is 15.5 ng / L, and the recovery rate is 49%, which is significantly lower than the double carbon nanotube composite material.

[0092] Effect analysis: Although fluorinated carbon nanotubes have a certain adsorption capacity, they cannot effectively capture and enrich trace quinolones due to their insufficient functionality. This further proves the limitations of single carbon nanotube types in composite materials and verifies the effectiveness and necessity of the double carbon nanotube strategy.

[0093] The experimental results of Comparative Example 7, Comparative Example 8 and Example 1 further prove the significant advantages of the double carbon nanotube composite strategy in the present application in improving the enrichment efficiency of trace quinolones.

[0094] Different mass ratios of FCNs to ACNs, different Fe 2+ and Fe 3+ The enrichment results of the magnetic nanocomposite materials prepared by different mass ratios of FCNs to ACNs on five antibiotic pollutants (NOR, FLX, DAN, ENR, and SAR) are shown in Table 1. Figure 2 It can be seen that by changing the mass ratio of FCNs to ACNs from 3:0 to 0:3 (3:0, 2:1, 1:1, 1:2, and 0:3), the influence of the ratio of FCNs to ACNs on the enrichment performance of several drugs (NOR, FLX, DAN, ENR, and SAR) was studied, Figure 2 The peak areas of the drugs under various conditions are shown, which reflect the amount of drugs captured. For example, Figure 2As shown in (a), when the mass ratio of FCNs to ACNs is 1:1, better enrichment results can be obtained. Figure 2 b shows different Fe 2+ and Fe 3+ The results showed that when 2.0 mmol of divalent iron (Fe 2+ ), this ratio not only helps to form purer and better crystallized iron oxide (Fe3O4), but also helps Fe 2+ As a reducing agent, Fe 3+ It directly participates in the formation of Fe3O4. 2+ / Fe 3+ The ratio plays a key role in controlling the formation rate of Fe3O4 and improving crystal quality. Under the optimized preparation conditions, the batch preparation of MNC showed good reproducibility and a significant increase in enrichment efficiency from 3.6% to 7.2%. This improvement not only confirms the efficiency and reliability of the one-pot method in the preparation process, but also emphasizes its potential for widespread application in MNC / MSPE technology, which is of great significance for environmental monitoring and effective treatment of pollutants. Optimizing the preparation of MNC through this method can not only improve the enrichment efficiency of specific pollutants, but also ensure the quality and performance of the product through a consistent preparation process, thereby promoting the widespread deployment of this technology in practical applications.

[0095] Figure 3 FT-IR spectrum, TEM image, magnetization curve and Zeta potential at different pH of MNC prepared in Example 1. FT-IR spectrum shows the infrared spectra of amino carbon nanotubes and iron oxide (ACNs@Fe3O4, I in a), fluorinated carbon nanotubes and iron oxide (FCNs@Fe3O4, II in a) and magnetic nanocomposite material in Example 1 (MNC, III in a). Through these spectra, specific absorption peaks of three compounds (ACNs@Fe3O4, FCNs@Fe3O4, MNC) can be seen. These absorption peaks represent the presence of different chemical groups in the material, such as CF bonds, CN bonds and Fe-O-Fe bonds, which help to confirm the chemical structure of the material and the successful introduction of functional groups. Figure 4The TEM images can observe the microstructure of MNCs, such as particle size, shape, and the distribution of carbon nanotubes and iron oxide nanoparticles. It can be seen that the MNCs prepared in Example 1 can be clearly seen under a transmission electron microscope image at a magnification of 10,000x. The particle size of Fe3O4 and the diameter of carbon nanotubes are about 35 nm and 2050 nm, respectively. The TEM image shows the microstructure of the magnetic nanocomposite (MNC), and the iron oxide (Fe3O4) nanoparticles can be clearly seen to be wrapped by carbon nanotubes (CNTs). The diameter of the carbon nanotubes is about 20 to 50 nm, and the particle size of the iron oxide nanoparticles is about 35 nm. This structure shows that the iron oxide nanoparticles are uniformly distributed on the carbon nanotubes, forming a composite material with a magnetic core and a functional shell. Such a microstructure is beneficial to the material to exhibit excellent performance in magnetic separation and pollutant adsorption. Figure 3 As shown in FIG. 1C, the magnetization curve of the Fe3O4 nanoparticles shows that although the magnetic saturation value (MSV) and the magnetic susceptibility of the MNCs are low, it still exhibits typical paramagnetic behavior. Specifically, the magnetic saturation value of Fe3O4 is 78.6 emu / g, and the magnetic saturation value of the MNCs is slightly lower, mainly because the FCNs and ACNs cover the magnetic core. Nevertheless, the magnetic response of these nanocomposites is sufficient to support rapid magnetic separation. Figure 5 To recover the dispersed MNC nanoparticles in the solution in Example 1, only by applying a simple magnetic field, the dispersed MNC nanoparticles can be quickly recovered from the sample solution in 10 seconds. This rapid magnetic response is very advantageous for rapid processing and separation in practical applications. From the magnetization curve, it can be seen that the magnetism of the MNCs is lower than that of pure iron oxide due to the wrapping of carbon nanotubes, but it is still sufficient to achieve a rapid magnetic response. The zeta potential reflects the strength of the charge on the surface of the particles, which is crucial for understanding the stability of the particles in the solution and the interaction with drug molecules. It can be seen that the MNCs show positive charge under acidic conditions. With the increase of pH value, the positive charge decreases obviously, and the electric neutrality can be observed at pH value of 5.5. At the same time, with the continuous increase of pH value, the MNCs show more and more negative charge. The results show that the pH value of the solution has a significant effect on the charge properties and existing form of the MNCs. Therefore, when using MNCs to capture FQs, the pH value of the solution should be strictly controlled.

[0096] The above characterization results show that the FCNs and ACNs are successfully anchored on Fe3O4, and the obtained MNCs contain abundant functional groups, good magnetism and sufficient charge.

[0097] In order to study the adsorption characteristics of quinolone antibiotics (FQs) by MNC / MSPE (MNC was used in magnetic solid phase extraction (MSPE) technology), norfloxacin (FLX) was selected as the test analyte for the adsorption characteristics of the FQs. Figure 6 The adsorption kinetics curve of FLX on MNC shown in the figure shows that the enrichment of FLX increases rapidly with the increase of adsorption time and reaches the adsorption equilibrium after 6.0 min.

[0098] In addition, the experimental data were simulated by pseudo-first-order and pseudo-second-order kinetic models to investigate the dominant factors in the adsorption process of FLX on MNC. The data summarized in Table 1 show that the correlation coefficients (R 2 ) were 0.9871 and 0.6485, respectively. Therefore, chemisorption plays a dominant role in the capture of FQs. (The pseudo-second-order kinetic model is more suitable for describing the adsorption process of flunitrazepam on MNCs because its correlation coefficient is higher, indicating that chemisorption may be the dominant mechanism for flunitrazepam adsorption.)

[0099] Table 1 Pseudo-first-order kinetic and pseudo-second-order kinetic parameters during FLX adsorption

[0100]

[0101]

[0102] The present invention also conducted a static adsorption experiment to test the adsorption capacity of the prepared adsorbent. Figure 7 As shown in Figure 2, the adsorption amount of FLX by MNC increased significantly with the increase of the initial FLX concentration. When the concentration of FLX was 30 mg / L, the adsorption reached equilibrium. In addition, the maximum adsorption capacity of MNC for FLX was calculated based on the static adsorption curve, and the relevant value was as high as 10.2 mg / g. Compared with previous studies, the adsorption capacity obtained was satisfactory. Further, the results of the adsorption isotherm were simulated by the Langmuir and Freundlich models. As listed in Table 2, the R of the Langmuir model was 2 The value is 0.1738, which is much lower than the R of the Freundlich model. 2The values of the Langmuir and Freundlich models were calculated and listed in Table 2. The results showed that the Freundlich model was more suitable for describing the adsorption of FQs on MNC, with a higher correlation coefficient, indicating that the model more accurately reflected the adsorption phenomenon. The lower correlation coefficient of the Langmuir model indicated that it was less suitable for describing this adsorption process.

[0103] Table 2 Langmuir and Freundlich model parameters for the adsorption of FLX on magnetic nanocomposite (MNC) / magnetic solid-phase extraction (MSPE)

[0104]

[0105] As an example, the MNC prepared in Example 1 was used to test its detection effect on trace quinolones in environmental water bodies:

[0106] Application Example 1

[0107] MNC / MSPE procedure:

[0108] 50 mL of sample to be tested (including lake water, river water and wastewater collected from Haichang Lake in Xiamen City, Jiulong River in Zhangzhou City and Xiamen Sewage Treatment Plant, respectively) was collected and filtered through a 0.45 μm PTFE membrane, and the pH value of the solution was adjusted to 6.0. Then 40 mg of MNC was added to capture the FQs under study, and adsorbed in a constant temperature oscillator (200 rpm) for 8.0 min. After adsorption, the MNC was collected from the sample solution using a magnet. 0.5 mL of acetonitrile / formic acid (98 / 2.0, by volume) solution was used to elute the FQs retained on the adsorbent, and eluted for 4.0 min at 200 rpm. After elution, the MNC was collected using an external magnetic field, and the eluate was blown dry with nitrogen, then eluted with 100 μL of acetonitrile / formic acid solution, and the MNC was again collected using an external magnetic field while the eluate was dried with nitrogen, and then redissolved with 100 μL of acetonitrile. The redissolved solution was subjected to quantitative analysis of FQs content by high performance liquid chromatography / fluorescence detection (HPLC / FD). The adsorbent used was first rinsed with elution solvent and ultrapure water for 10 min. The MNC after rinsing was used to capture FQs in other samples.

[0109] This MSPE procedure not only details the steps for the enrichment and quantitative analysis of FQs from samples, but also demonstrates how to efficiently recover and reuse MNCs from complex matrices through the magnetic separation and elution processes, and how to achieve effective enrichment and analysis of FQs in samples.

[0110] Investigation of adsorption characteristics

[0111] Adsorption isotherm and adsorption kinetics studies were performed using norfloxacin (FLX) as the test solute to investigate the adsorption characteristics of MNC / MSPE for FQs. For the adsorption isotherm experiment, a series of FLX solutions with different initial concentrations were prepared. The solution volume was controlled at 50 mL, and 40 mg of MNC was used for adsorption. The adsorption duration was controlled at 8.0 min in a constant-temperature shaker at 200 rpm. After adsorption, the residual content of FLX in the solution was detected using HPLC / FD. The adsorption capacity of FLX on MNC was calculated based on equation (1):

[0112]

[0113] where Q e is the adsorption capacity (μg / g); c i and c e are the initial and equilibrium concentrations of FLX (μg / L), respectively; V is the solution volume (50 mL in this invention); and w is the mass of the adsorbent (40 mg).

[0114] The experimental data were fitted with the Langmuir (equation 2) and Freundlich (equation 3) models, respectively.

[0115]

[0116] where C e (mg / L) is the equilibrium concentration of FLX in the solution, Q e (mg / g) and Q max (mg / g) are the equilibrium and maximum adsorption capacities, respectively, K L and K F are the Langmuir and Freundlich characteristic constants.

[0117] Kinetic experiments of FLX (1000 μg / L) on MNC (40 mg) were performed by measuring the FLX concentration at different time intervals (0.25, 0.50, 1.0, 2.0, 3.0, 4.0, 6.0, 8.0, and 10 min) to calculate the adsorption capacity Qt (mg / g) at different times t. Pseudo-first-order (equation 4) and pseudo-second-order (equation 5) kinetic models were adopted for kinetic analysis.

[0118] ln(Qe -Q t )=lnQ e -K1t (4)

[0119]

[0120] where Q e (mg / g) and Q t (mg / g) are the FLX adsorption amounts at equilibrium and time t (μg / g), respectively; K1 and K2 are the rate constants of the pseudo-first-order and pseudo-second-order models, respectively.

[0121] MNC combined with HPLC for FQs detection:

[0122] Chromatographic conditions: A high performance liquid chromatography system equipped with a fluorescence detector (FD) was used for separation using a ThermoC18 column. The mobile phase consisted of ACN (solvent A) and a 0.5% FA solution in water (solvent B), with gradient elution.

[0123] Sample injection and analysis: The prepared samples were injected into the HPLC system through an automatic sample injector, and the detection wavelength was set according to the specific fluorescence characteristics of FQs for quantitative analysis.

[0124] Data Processing and Analysis: Chromatographic data collected by the HPLC system are processed and the concentration of FQs is quantified based on retention time and peak area. The actual concentration of FQs in the water sample is calculated by combining the standard curve and the volume change during sample preparation.

[0125] The present invention also evaluated the performance of the proposed MNC / MSPE in adsorbing FQs from water samples. According to the method of Application Example 1, single-factor experiments were conducted to optimize the following factors: the amount of MNC used (20 mg, 30 mg, 50 mg, 60 mg), the formic acid content in the elution solvent (composed of acetonitrile and formic acid), the adsorption time (5 min, 6 min, 7 min, 9 min), the elution time (2 min, 3 min, 5 min, 6 min), the solution pH (pH = 2.0, pH = 3.0, pH = 4.0, pH = 5.0, pH = 7.0, pH = 8.0, pH = 9.0, pH = 10.0), and the salt concentration of the sample solution (the salt was sodium chloride (NaCl). When the salt content was increased, the coexistence of salting-out effect and salting-in effect occurred. The ionic strength of the sample solution was adjusted by adding different concentrations of NaCl, ranging from 0.0% to 20% (weight / volume). The results are as follows: Figure 8The results show that the enrichment performance decreased significantly with the addition of NaCl, which is probably due to the dominant role of the salting-in effect when the ionic strength increases. Therefore, the ionic strength of the solution was not adjusted in the subsequent experiments. The effects of the adsorption time and the elution time were investigated to obtain the best enrichment performance. The experiments were carried out at room temperature and repeated three times for each experiment. The results show that the best adsorption and elution effects can be obtained when the adsorption time is controlled at 8.0 min and the elution time is controlled at 4.0 min. In addition, the effect of the solution pH value was investigated, which shows that the capture performance of MNC / MSPE for FQs is best at pH 6.0.

[0126] The effect of the MNC dosage on the adsorption performance was evaluated, and the dosage of MNC included 20, 30, 40, 50 and 60 mg. Figure 8 The change curves shown in Fig. a show that when the dosage of MNC increases from 20 mg to 40 mg, the peak areas of all analytes increase significantly, and when the dosage of MNC continues to increase, the peak areas do not change significantly. Therefore, 40 mg of MNC was selected to capture FQs in the subsequent experiments.

[0127] Considering that multiple interactions contribute to the capture of FQs on MNC, a mixture of ACN and FA was selected as the double elution solvent. Figure 8 The effect of the FA content on the elution performance is shown in Fig. b. The results show that the elution performance improves with the increase of the FA content in the elution solvent, because FA can destroy the FF bond and hydrogen bonding force between MNC and FQs, which is beneficial to the release of FQs from MNC. However, when the content of FA exceeds 2.0% (volume ratio), the elution performance decreases. Based on these results, 0.50 mL of ACN / FA (98 / 2.0, volume ratio) mixture was selected as the best elution solvent in the subsequent studies.

[0128] For MSPE, the adsorption performance depends largely on the adsorption time. In the present application, the effect of the adsorption time on the enrichment performance was evaluated by increasing the adsorption time from 5.0 min to 9.0 min. Figure 8 Fig. c reveals that the maximum adsorption amount can be obtained when the adsorption time is 8.0 min. At the same time, the effect of the elution time in the range of 2.0 to 6.0 min with an interval of 1.0 min was investigated. From Figure 8 As can be seen from Fig. d, the retained FQs can be completely eluted from MNC after 4.0 min. Accordingly, the most suitable adsorption and elution times are controlled at 8.0 min and 4.0 min, respectively.

[0129] The presence of various polar groups in FQs and MNCs. Therefore, the existing form of FQs and adsorbents is related to the pH of the solution (referring to the pH of the sample solution used when performing magnetic solid phase extraction (MNC / MSPE)). In other words, the capture performance of MNC / MSPE for FQs depends on the pH of the sample solution. In this invention, the effect of solution pH was evaluated by increasing the pH from 2.0 to 10.0. Figure 8 The change profile shown in Figure e indicates that the peak area of all the studied FQs rapidly increased as the pH increased from 2.0 to 6.0, and then decreased from 6.0 to 10.0. Therefore, in the subsequent study, the pH of the solution was controlled at 6.0.

[0130] When the ionic strength in the sample matrix changes, salting-out and salting-in effects (which have opposite effects on the enrichment performance) coexist. In this invention, the ionic strength of the sample solution was adjusted by adding different amounts of NaCl (0.0-20%, w / v). Figure 8 The results described in Figure f indicate that the enrichment performance decreased significantly as the amount of added NaCl increased. The reason could be that the salting-in effect dominates when the ionic strength increases. Therefore, the ionic strength of the solution was not adjusted in the subsequent experiments.

[0131] Under the optimal enrichment parameters, the established MNC / MSPE technology showed satisfactory enrichment ability for the studied FQs. The chromatograms obtained using high-performance liquid chromatography-diode array detector (HPLC / DAD) were used to analyze the pollutants in water and soil samples treated with magnetic nanocomposites (MNCs) / magnetic solid phase extraction (MSPE).

[0132] (a) Blank water and soil samples before treatment:

[0133] The purple line shows the results of water and soil samples without added pollutants after MNC / MSPE treatment. It demonstrates the effect of the treatment process on the natural pollutants or background signals that may exist in the samples.

[0134] (b) Sample treatment results after adding standard substances:

[0135] The blue line shows the results of samples with known concentrations of standard substances after MNC / MSPE treatment. This demonstrates the detection results of these compounds after MNC / MSPE treatment, which helps to evaluate the capture and removal efficiency of MNC / MSPE treatment for specific compounds.

[0136] Experimental conditions:

[0137] Amount of MNC used: 40 mg of MNC was used in each sample.

[0138] Elution solution: A mixture of 0.5 mL of acetonitrile and formic acid (98 / 2 by volume) was used as the eluent to release the adsorbed contaminants from the MNC.

[0139] Adsorption and desorption time: The adsorption time was 8 minutes, and the desorption time was 4 minutes, which were optimized based on previous experiments to ensure efficient contaminant capture and subsequent rapid release.

[0140] pH and ionic strength of the sample: The pH of the sample was set to 6.0 without adjusting the ionic strength. This helped maintain a certain chemical environment to facilitate efficient adsorption of contaminants.

[0141] Sample volume and spiking concentration: The sample volume was 50 milliliters, and the spiking concentration of each compound was 100 micrograms per liter, which ensured sufficient amounts of contaminants for analysis and evaluation of enrichment effectiveness.

[0142] Figure 9 For the chromatograms obtained using high-performance liquid chromatography with a diode array detector (HPLC / DAD). Before enrichment, the peaks of FQs were very small and difficult to identify Figure 9 a). However, after effective enrichment by MNC / MSPE, the peak heights of all analytes increased significantly Figure 9 b). The enrichment factors of NOR, FLX, DAN, ENR, and SAR by MNC / MSPE were up to 196, 212, 178, 223, and 306, respectively. The high enrichment performance indicated that better sensitivity could be achieved. At the same time, adsorption and desorption cycle experiments were conducted (using MNC prepared in Example 1 as an example) to evaluate the service life and regeneration ability of MNC, and the specific process of the adsorption and desorption cycle experiment was as follows:

[0143] 1. Adsorption experiment: Take 50 mg of MNC and add it to 100 mL of water sample containing a fixed concentration (1.0 mg / L) of quinolones (NOR, FLX, DAN, ENR, and SAR).

[0144] At room temperature, use a magnetic stirrer to stir for 30 minutes to allow the MNC to fully adsorb the quinolones in the water sample.

[0145] Use magnetic separation to collect the MNC, remove the supernatant, and wash the MNC with deionized water to remove unbound substances.

[0146] 2. Desorption experiment: Add the MNC adsorbed with quinolones to 10 mL of 0.1 M hydrochloric acid solution containing 5% methanol.

[0147] At room temperature, use a magnetic stirrer to stir for 30 minutes to allow the quinolones in the MNC to desorb.

[0148] MNC were collected using magnetic separation, supernatant was removed, and the supernatant was collected for high performance liquid chromatography diode array detector (HPLC / DAD) analysis.

[0149] 3. Cycling experiment: The above adsorption and desorption processes were repeated for 50 times to evaluate the regeneration ability of MNC.

[0150] After each cycle, the quinolones in the desorption solution were detected using HPLC / DAD, and the efficiency of each adsorption and desorption was recorded.

[0151] Regeneration ability evaluation: As shown in Figure 10 , the magnetic nanocomposite prepared by the present application showed good regeneration ability as an adsorbent in 50 cycles of the experiment, and the efficiency of each adsorption and desorption remained basically stable, indicating that MNC could be reused for more than 50 times without losing the enrichment ability.

[0152] Experimental conclusion: Through the above adsorption and desorption cycle experiment, it is verified that the double carbon nanotube magnetic nanocomposite (MNC) has excellent regeneration ability and long service life in enriching trace quinolones. This shows that MNC not only has high enrichment performance, but also can be repeatedly used through a simple adsorption and desorption process, and has good practical application prospect.

[0153] Analytical characteristics of the established method

[0154] The introduced MNC / MSPE technique was combined with HPLC / FD for the determination of trace FQs in water samples. Before application, various analytical characteristics including linear range, correlation coefficient (R 2 ), limit of detection (LODs), limit of quantification (LOQs), and precision were investigated. As listed in Table 3, the linear range was 1.010000 ng / L for NOR, FLX, and ENR, and 2.010000 ng / L for DAN and SAR. All the calibration curves presented good linearity with R 2 values varying between 0.9913 and 0.9978. The LODs based on a signal-to-noise ratio of 3 were in the range of 0.180.61 ng / L, and the LOQs (signal-to-noise ratio of 10) were in the range of 0.592.0 ng / L. In addition, intra- and inter-day precision experiments at low (10.0 ng / L) and high (1000 ng / L) spiked levels were performed to examine the precision of the method. The data in Table 3 indicated that the RSDs were in the range of 2.59.7% and 2.79.6% for low and high spiked concentrations, respectively.

[0155] Table 3 Performance results of analyzing quinolone drugs in water samples using the method of the present application

[0156]

[0157] a: Includes peak levels of 1.0, 2.0, 5.0, 10.0, 50.0, 100.0, 500.0, 1000, 5000, and 10000 ng / L.

[0158] Linear range: 1.0-10000 ng / L for norfloxacin, fluxicin and enrofloxacin; 2.0-10000 ng / L for danoxacin and sarafloxacin.

[0159] Correlation coefficient (R 2 ): The correlation coefficients of these drugs ranged from 0.9913 to 0.9972, showing a good linear relationship.

[0160] Limit of detection (LOD) and limit of quantification (LOQ): The LOD ranged from 0.18 ng / L to 0.61 ng / L, and the LOQ ranged from 0.59 ng / L to 2.0 ng / L, indicating that the method had good detection capability for extremely low concentrations of quinolones.

[0161] Precision: The intra-day and inter-day relative standard deviations (RSD%) ranged from 2.5% to 9.7%, indicating that the method had reasonable repeatability and stability.

[0162] These data demonstrate the effectiveness and reliability of this method for the detection of trace levels of quinolones in water, making it suitable for environmental monitoring and quality control.

[0163] Determination of actual water samples

[0164] To evaluate the utility of the developed MNC / MSPEHPLC / FD method for quantifying low-level FQs, three real-world water samples (including lake water, river water, and wastewater) were processed and analyzed. Data summary shows that 3.01 ng / L of FLX and 2.62 ng / L of SAR were detected in the lake water sample. Low levels of NOR, FLX, and ENR were observed in the river water sample. In the wastewater sample, NOR, DAN, and SAR were found at 8.61, 10.2, and 9.36 ng / L, respectively. To assess the anti-interference ability of the developed method, recoveries at 10.0, 100, and 1000 ng / L were evaluated. As shown in Table 4, recoveries ranged from 82.3% to 112%, and the RSDs for repeatability ranged from 0.91% to 9.2%.

[0165] Table 4 shows the results of the analysis of the recovery of the fluoroquinolones (FQs) studied in real samples. This table relates to three different types of water samples: lake water, river water and waste water. For each sample, tests were carried out without the addition of standards (i.e. the natural content) and with the addition of standards of different concentrations (10 ng / L, 100 ng / L, 1000 ng / L).

[0166] Results of the experiments:

[0167] 1. Lake water sample:

[0168] Without the addition of standards, the contents of fleroxacin (FLX) and sarafloxacin (SAR) were detected, which were 3.01 ng / L and 2.62 ng / L, respectively.

[0169] With the addition of 10 ng / L of standards, the recoveries were 102% and 92%, respectively.

[0170] With the addition of 100 ng / L of standards, the recoveries were 98.3% and 102%, respectively.

[0171] With the addition of 1000 ng / L of standards, the recoveries were 110% and 99.2%, respectively.

[0172] 2. River water sample:

[0173] Without the addition of standards, only low contents of norfloxacin (NOR) and enrofloxacin (ENR) were detected.

[0174] With the addition of 10 ng / L of standards, the recoveries of norfloxacin, fleroxacin and enrofloxacin were 100%, 90% and 92%, respectively.

[0175] With the addition of 100 ng / L of standards, the recoveries were between 87% and 100%.

[0176] With the addition of 1000 ng / L of standards, the recoveries were 109%, 91.8% and 99.3%.

[0177] 3. Waste water sample:

[0178] Without the addition of standards, the contents of norfloxacin, danofloxacin (DAN) and sarafloxacin were detected, which were 8.61 ng / L, 10.2 ng / L and 9.36 ng / L, respectively.

[0179] With the addition of 10 ng / L of standards, the recoveries were 106%, 93.6% and 95%, respectively.

[0180] With the addition of 100 ng / L of standards, the recoveries were 90.6%, 109% and 104%, respectively.

[0181] The recoveries were 100%, 99.7%, and 91.8% after the addition of 1000 ng / L standards.

[0182] The data in Table 4 clearly show the effectiveness of the MNC / MSPE method in real water samples and the stable recovery performance at different concentration levels.

[0183] Table 4. Results of the analysis of the recoveries of the studied fluoroquinolones (FQs) in real samples

[0184]

[0185]

[0186] Note: ND means not detected.

[0187] To further evaluate the advantages of the developed method in the quantification of FQs in water samples, the results obtained were compared with the reported MSPE-based methods. As shown in Table 5, the total extraction time, including adsorption and desorption times, of the developed method was 12 min, which was shorter than that of the existing partial methods. In addition, compared with the reported studies, the method of the present application provided a wider linear range and lower detection limit. The recovery of the method was comparable to other methods. In addition, the ecological scale score (ESS) related to the greenness of the adsorbent preparation was also compared. The higher the ESS, the greener the color. As shown in Table 5, the ESS value of the prepared MNC was 87, which was higher than that of most reported magnetic adsorbents coated with sodium dodecyl sulfate (NCSDS) nanoparticles except for iron. Through comparison, it was further confirmed that the developed method had the advantages of greenness in the preparation of adsorbents, fast extraction speed, high sensitivity, etc. Therefore, the established method was feasible in the pre-concentration and quantification of trace FQs in water samples.

[0188] Table 5. Comparison of the method of the present application with the previously reported methods

[0189]

[0190] Note: a: magnetic metal-organic framework, b: Fe3O4nanoparticles coated with sodium dodecyl sulfate, c: Fe3O4@3-(trimethoxysilyl)propyl methacrylate nanoparticle polymerized ionic liquid, d: ionic liquid functionalized magnetic nanocomposite, e: magnetic multi-template molecularly imprinted polymer (MIP), f: magnetic molecularly imprinted adsorbent based on a double-template molecule, g: magnetic MIP with a clear core-shell structure.

[0191] The references in Table 5 are as follows:

[0192] [1] H. Wang, X. Y. Zhao, J. W. Xu, Y. Z. Shang, H. Wang, P. Wang, X. T. He, J. Tan, Determination of quinolones in environmental water and fish by magnetic metalorganic frameworks based magnetic solid phase extraction followed by high performance liquid chromatography tandem mass spectrometry, J. Chromatogr. A. 1651 (2021) 462286.

[0193] [2] L. Wang, Q. X. Yuan, G. X. Liang, L. B. Shi, Q. Zhan, Magnetic mixed hemimicelles solid phase extraction coupled with high performance liquid chromatography for the extraction and rapid determination of six fluoroquinolones in environmental water samples, J. Sep. Sci. 38 (2015) 996-1001.

[0194] [3] H. Wu, Y. T. Shi, X. Z. Guo, S. L. Zhao, J. L. Du, H. P. Jia, L. N. He, L. M. Du, Determination and removal of sulfonamides and quinolones from environmental water samples using magnetic adsorbents, J. Sep. Sci. 39 (2016) 4263-4658.

[0195] [4] D. Lu, M. Qin, C. Liu, J. Deng, G. Shi, T. Zhou. Ionic liquid functionalized magnetic metalorganic framework nanocomposites for efficient extraction and sensitive detection of fluoroquinolone antibiotics in environmental water, ACS Appl. Mater. Interfaces. 13 (2021) 53575367.

[0196] [5] Y. M. Fan, G. L. Zeng, X. G. Ma. Multitemplates surface molecularly imprinted polymer for rapid separation and analysis of quinolones in water, Environ. Sci. Pollut. R. 27 (2020) 71777187.

[0197] [6] Y. Z. Xie, Q. Y. Li, L. L. Qin, X. B. Zhou, Y. M. Fan. Multitemplates surface molecularly imprinted polymer for simultaneous and rapid determination of sulfonamides and quinolones in water: effect of carbon carbon double bond, Environ. Sci. Pollut. R. 28 (2021) 5495054959.

[0198] [7] Y. F. Huang, Y. Y. Zhang, Y. L. Yu, X. C. Song, X. J. Huang. One pot preparation of magnetic molecularly imprinted adsorbent with dual template molecules for simultaneously specific capture of sulfonamides and quinolones in water and milk samples, Food Chem. 434 (2024) 137412.

[0199] [8] X. J. Dai, Y. F. Wu, Z. H. Jia, C. M. Bo. Preparation of water compatible magnetic imprinted nanospheres using heptakis(beta cyclodextrin ionic liquid) as functional monomer for selective recognition of fluoroquinolones in water samples, Microchem. J. 171 (2021) 106793.

[0200] From Table 5, it can be seen that:

[0201] Extraction time: The extraction time of the method of the present application is 12 minutes, which is shorter than that of some existing methods.

[0202] Linear range: The linear range provided by the method of the present application is wider, from 0.001 pg / L to 10 pg / L, which is better than most of the comparative methods.

[0203] Limit of detection (LOD): The LOD of the method of the present application is from 0.00018 pg / L to 0.00061 pg / L, showing higher sensitivity.

[0204] Recovery rate: Compared with other methods, the recovery rate of the method of the present application is between 82.3% and 112%, showing good recovery effect.

[0205] Environmental sustainability score (ESS): The ESS score of the method of the present application is 87, which is higher than most of the reported magnetic adsorbents, indicating that the method of the present application is more environmentally friendly in the preparation process of the adsorbent.

[0206] The MNC of the present application has shorter extraction time and lower LOD, and the environmental sustainability score also shows that the green preparation advantage of the method of the present application is more obvious.

[0207] The present application adopts one-pot hydrothermal method to quickly and conveniently prepare a novel functional group-rich magnetic nanocomposite material. The material exhibits good magnetic performance and high capture performance for five FQs through FF, hydrogen bonding, π-π stacking, dipole-dipole force and hydrophobic force and other interactions. The adsorption experiment shows that chemical interaction plays a dominant role in the extraction process. Similarly, due to the uneven distribution of active sites in the adsorbent, the adsorption process of MNC / MSPE for FQs is a multilayer adsorption. Under the most suitable MNC and MNC / MSPE preparation parameter conditions, the proposed MNC / MSPE HPLC / FD is successfully applied to low-level quantification of different water samples, and compared with the reported MSPE-based method, it has some advantages. Therefore, the introduced method can become a competitive method for routine monitoring of trace or ultra-trace FQs in water and other complex samples.

[0208] The present application details the preparation and application process of MNC, and demonstrates the superior performance of the present application in improving the sensitivity and efficiency of FQs detection in environmental water samples. Through this detailed embodiment, the present application provides a new and effective technical means for environmental monitoring. Compared with existing FQs measurement methods, the method of the present application shows a lower detection limit of 0.18 ng / L to 0.61 ng / L, a relative standard deviation (RSD) of precision of 2.5% to 9.7%, and a recovery rate of different spiked levels of 82.3% to 112%. The superior sensitivity and reliability of the magnetic nanocomposite material of the present application are proved. The accuracy and effectiveness of the method of the present application in different water samples are shown, and combined with the high separation ability of HPLC and the high sensitivity detection of FD, the method of the present application can provide high-accuracy FQs concentration results, and shows some advantages in the rapidity and environmental friendliness of the preparation of the adsorbent, high sensitivity and cost-effectiveness.

[0209] In summary, the MNC prepared by dual functionalization of amino and fluoro groups in the present application realizes efficient and highly selective capture of FQs, and the material exhibits lower detection limit and higher adsorption capacity than existing materials.

[0210] The experimental data of the present application show that MNC has excellent capture effect on FQs in complex environmental water samples, exhibits superior chemical and physical stability, and can still maintain high performance after multiple cycles, proving its long-term usability in practical applications.

[0211] The use of MNC of the present application significantly simplifies the sample pretreatment step, reduces the complexity and time cost of operation, and at the same time improves the overall detection process efficiency.

[0212] The MNCs of the present application not only solve the limitations of traditional adsorption materials in treatment efficiency and selectivity, but also exhibit significant advantages in environmental compatibility and economic benefits, and provide a new efficient and reliable technical solution for detection of trace FQs in water samples.

[0213] The above merely provides the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a magnetic nanocomposite material, characterized in that: Aminated carbon nanotubes and fluorinated carbon nanotubes are used as functional monomers, mixed with iron-containing materials, and ethylenediamine is used to adjust the pH to 9.0-10.0 to prepare magnetic nanocomposites through a hydrothermal method. The mass ratio of the amino-treated carbon nanotubes to the fluorinated carbon nanotubes is (1-2): (1-2); The iron-containing material is a mixture of a divalent iron compound and a trivalent iron compound; The hydrothermal temperature is 180° C., and the hydrothermal time is 12 h.

2. The method for preparing the magnetic nanocomposite material according to claim 1, wherein: The divalent iron compound is FeCl2·4H2O, and the trivalent iron compound is FeCl3·6H2O.

3. The method for preparing the magnetic nanocomposite material according to claim 2, wherein: The mass ratio of the FeCl2·4H2O to FeCl3·6H2O is 2:

1.

4. A magnetic nanocomposite material, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 3.

5. Use of the magnetic nanocomposite material according to claim 4 in enriching trace amounts of quinolones.

6. A surface molecularly imprinted polymer, characterized in that The magnetic nanocomposite material according to claim 4, wherein the template molecule is norfloxacin, norfloxacin, danoxacin, enrofloxacin or sarafloxacin.

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