Magnetic nanofluid, preparation method thereof and application of magnetic nanofluid in detection of polycyclic aromatic hydrocarbon in water body

Abstract

The invention provides a magnetic nanofluid as well as a preparation method and application thereof in detection of polycyclic aromatic hydrocarbon in a water body. The magnetic nanofluid comprises small-particle-size Fe3O4 nano-particles coated with a deep eutectic solvent, the particle size of the small-particle-size Fe3O4 nano-particles ranges from 5.5 nm to 8.5 nm, and the deep eutectic solvent comprises a thymol-based hydrophobic deep eutectic solvent. The magnetic nanofluid is used for extracting 16 polycyclic aromatic hydrocarbons migrating from cigarette butts to a water body, after magnetic separation, the magnetic nanofluid is eluted, and the eluent directly enters a GC-MS / MS instrument for analysis. The magnetic nanofluid can realize efficient extraction and enrichment of 16 polycyclic aromatic hydrocarbons in a water body such as a cigarette butt soaking solution and the like; magnetic separation solves the problem that 16 trace polycyclic aromatic hydrocarbons in a water body are difficult to separate after being extracted by a deep eutectic solvent, and experimental operation steps are simplified; the average particle size of the magnetic Fe3O4 nanoparticles adopted in the magnetic nanofluid is small, so that the stability of the magnetic nanofluid is greatly improved; by adopting the GC-MS / MS method, the sensitivity of the method can be obviously improved.

Description

Technical Field

[0001] The present invention belongs to the field of environmental science, and in particular relates to a magnetic nanofluid, a preparation method thereof, and an application thereof in the detection of polycyclic aromatic hydrocarbons in water. Background Art

[0002] Cigarette butts, one of the most common types of litter worldwide, pose a significant threat to aquatic ecosystems through the leaching of polycyclic aromatic hydrocarbons (PAHs). PAHs in cigarette butts primarily come from tobacco combustion residues. The combustion process produces large quantities of PAHs (such as benzo[a]pyrene, phenanthrene, and pyrene), which are adsorbed on the filters or residual tobacco in cigarette butts. Studies have shown that a single cigarette butt may contain dozens of PAHs, some of which are highly toxic and carcinogenic (such as benzo[a]pyrene). When cigarette butts are discarded into water bodies (such as rivers, lakes, or oceans), PAHs gradually leach out through immersion. The leached PAHs are acutely toxic to aquatic organisms (such as fish, algae, and invertebrates), potentially causing developmental abnormalities, reproductive suppression, and even death. PAHs are also bioaccumulative and may be transferred through the food chain, ultimately impacting human health (such as carcinogenic risks). Some studies have found that PAH concentrations in cigarette butt soaks can reach levels harmful to aquatic organisms (such as exceeding EC values) within a few days. 50 Therefore, it is of great significance to study the quantitative detection method of PAHs migration from cigarette butts to water bodies.

[0003] Existing research has limited reports on quantitative detection techniques for the migration of PAHs from cigarette butts into water. Dobaradaran et al. used commercial solid-phase extraction (SPE) tips to extract PAHs from simulated water samples and then combined them with GC-MS for quantitative analysis (S. Dobaradaran, TC Schmidt, N. Lorenzo-Parodi, W. Kaziur-Cegla, MA Jochmann, I. Nabipour, HV Lutze, U. Telgheder, Polycyclicaromatichydrocarbons (PAHs) leachates from cigarette butts into water, Environmental Pollution, 259 (2020) 113916.). PAHs in lakes and rivers are typically detected using liquid chromatography with fluorescence detection (HPLC-FL), gas chromatography-mass spectrometry (GC-MS), and gas chromatography-tandem mass spectrometry (GC-MS / MS). GC-MS / MS offers higher sensitivity and precision than HPLC-FL and GC-MS. Usually, samples need to be purified before instrumental analysis, such as liquid-liquid extraction and solid-phase extraction. Liquid-liquid extraction usually consumes a large amount of organic solvents and requires multiple operations and washing steps, which is cumbersome and time-consuming. Solid-phase extraction requires the use of commercial solid-phase extraction columns, which are relatively expensive. In recent years, low eutectic solvent liquid-liquid microextraction technology has been widely used in the enrichment of trace components in complex systems. Compared with traditional organic solvents, low eutectic solvents have the following advantages: 1) green and environmentally friendly; 2) high extraction rate; 3) short extraction process. However, the existing low eutectic solvent extraction technology has the problem of difficult separation after extraction, and usually adopts high-speed centrifugation followed by layered separation. The use of this separation method increases the extraction process flow and cost. Summary of the Invention

[0004] In light of this, to address the difficulty in separating the deep eutectic solvent used in existing liquid-liquid microextraction of PAHs from cigarette butts in water, the present invention primarily utilizes a magnetic nanofluid based on a deep eutectic solvent (DES) to extract PAHs from water. This method utilizes the π-π interaction between the DES and PAHs to achieve efficient PAH extraction. Furthermore, the introduction of magnetic nanoparticles enables rapid post-extraction separation, simplifying the extraction process and pretreatment for trace detection of PAHs samples. Furthermore, the magnetic nanofluid, combined with trace detection technology, enables quantitative detection of the migration of PAHs from cigarette butts into water, demonstrating high efficiency and sensitivity. Therefore, the present invention provides a magnetic nanofluid, a preparation method thereof, and its application in the detection of PAHs in water.

[0005] In order to solve the above problems, the technical solutions adopted by the present invention are as follows: A magnetic nanofluid is used in the detection of polycyclic aromatic hydrocarbons in water. The magnetic nanofluid (MND) comprises small-sized Fe3O4 nanoparticles coated with a deep eutectic solvent (DES), wherein the particle size of the small-sized Fe3O4 nanoparticles is 5.5-8.5 nm, and the DES is a thymol-based hydrophobic deep eutectic solvent.

[0006] Furthermore, the DES is mainly composed of a hydrogen bond acceptor and a hydrogen bond donor in a molar ratio of 1:1-2, wherein the hydrogen bond acceptor is thymol and the hydrogen bond donor includes at least one of coumarin, camphor, capric acid and menthol.

[0007] MND is a colloidal suspension composed of magnetic Fe₃O₄ nanoparticles dispersed in a DES liquid carrier. The polarity of the DES prevents it from dissolving in the PAH sample being tested, while enabling efficient enrichment of PAHs in water. Magnetic separation overcomes the difficulty of post-eutectic solvent extraction, simplifying the process. Furthermore, the small average particle size of the magnetic Fe₃O₄ nanoparticles significantly enhances the stability of the nanofluid, thereby increasing the extraction rate and ensuring the stability of the extraction effect, thereby improving the sensitivity and efficiency of quantitative PAH detection in water.

[0008] If the concentration of small-sized Fe3O4 nanoparticles is too low, the solution will contain fewer magnetic particles, affecting the magnetic separation effect. If the concentration of small-sized Fe3O4 nanoparticles is too high, the DES will not be able to effectively coat the small-sized Fe3O4 nanoparticles, affecting the stability of the nanofluid. Therefore, to further improve the magnetic separation efficiency and the stability of the magnetic nanofluid, the concentration of small-sized Fe3O4 nanoparticles in the magnetic nanofluid is 20-100 mg / mL, preferably 40-60 mg / mL.

[0009] Furthermore, the application is manifested in the use of the magnetic nanofluid to enrich trace PAHs in water. The PAHs are at least one of naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[123-cd]pyrene, dibenzo[a,h]anthracene, and benzo[g,h,i]perylene. The MND can simultaneously enrich 16 representative PAHs that migrate from cigarette butts into water.

[0010] Furthermore, the application includes: using the magnetic nanofluid in combination with GC-MS / MS method in the detection of trace PAHs in water. Preferably, the PAHs are derived from cigarette butts.

[0011] In the above-mentioned application provided by the present invention, MND as an extractant has high selectivity for PAHs compounds. After selective enrichment of PAH compounds, phase separation can be achieved by an external magnetic field. The operation is simple and rapid, greatly simplifying the extraction process of PAHs in water and the pretreatment process for quantitative detection, saving a lot of time and reducing costs.

[0012] A method for quantitatively detecting the migration of polycyclic aromatic hydrocarbons (PAHs) from cigarette butts into water bodies comprises the following steps: firstly subjecting a water sample soaked in cigarette butts to vortex extraction using the MND described above, then magnetically separating the MND, and eluting with an eluent to obtain a PAHs solution to be tested; and finally subjecting the PAHs solution to GC-MS / MS analysis.

[0013] Preferably, the chromatographic column for GC-MS / MS analysis is DB-5MS.

[0014] Furthermore, the method for preparing the PAHs solution to be tested includes: smoking cigarettes using a linear smoking machine in ISO smoking mode, collecting cigarette butts, placing 5-10 cigarette butts in 10-100 mL of deionized water, and soaking them for 1-10 days; taking 1-10 mL of the cigarette butt soaking solution into a stoppered colorimetric tube, adding an internal standard solution and mixing; then dropwise adding the MND and performing a vortex extraction treatment; then performing magnetic separation to remove the aqueous phase; then adding the eluent and performing a vortex elution treatment, and filtering the eluted phase with a 0.22 μm organic filter membrane to obtain the PAHs solution to be tested.

[0015] To further optimize the extraction effect, the MND addition amount is 100-500 µL, and the extraction time is 5-30 minutes. The internal standard solution contains 0.003-0.010 µg / L of phenanthrene-d10, 0.003-0.010 µg / L of anthracene-d10, and 0.003-0.010 µg / L of benzo[a]pyrene-d12. Because PAHs can leach into plastic, the stoppered colorimetric tube is made of glass to reduce interference and improve detection accuracy.

[0016] In order to further optimize the elution effect and improve the back extraction rate, the eluent is n-hexane, the amount of the eluent is 0.5-1 mL, and the elution time is 1-5 min.

[0017] The detection method provided by the present invention can achieve baseline separation of the chromatographic peaks of 16 PAHs by setting instrument parameters during analysis, separate the target analytes, and improve the sensitivity of detection.

[0018] Therefore, the quantitative detection method for the migration of PAHs from cigarette butts into water, provided by the present invention, is unprecedented. This method utilizes MND to directly extract the cigarette butt soaking solution, utilizes magnetic separation to eliminate the centrifugation step, and, combined with GC-MS / MS technology, enables highly sensitive and low-limit-of-detection detection of PAHs migrating from cigarette butts into water. Furthermore, this method can simultaneously measure 16 representative PAHs from cigarette butts in water, expanding the PAH detection range.

[0019] A magnetic nanofluid comprises small-sized Fe3O4 nanoparticles coated with a deep eutectic solvent (DES), wherein the particle size of the small-sized Fe3O4 nanoparticles is 5.5-8.5 nm, and the DES is a thymol-based hydrophobic deep eutectic solvent.

[0020] Furthermore, the DES is mainly composed of a hydrogen bond acceptor and a hydrogen bond donor in a molar ratio of 1:1-2, wherein the hydrogen bond acceptor is thymol and the hydrogen bond donor includes at least one of coumarin, camphor, capric acid and menthol.

[0021] A method for preparing the magnetic nanofluid comprises dispersing small-sized Fe3O4 nanoparticles in DES and subjecting the solution to ultrasonic treatment, wherein the ultrasonic treatment time is preferably 10-30 minutes.

[0022] The method for preparing the small-sized Fe3O4 nanoparticles is based on existing technology. Preferably, the method may include: using ferric ammonium sulfate, ferrous ammonium sulfate, and TX-100 solution as raw materials, and preparing the small-sized Fe3O4 nanoparticles by a hydrothermal method. Preferably, the hydrothermal reaction temperature is 70-90°C, and the reaction time is 20-40 minutes.

[0023] The preparation method of the DES is an existing technology. For example, the preparation method may include: mixing the hydrogen bond acceptor and the hydrogen bond donor in a molar ratio of 1:1-2, and continuously stirring at 70-90°C for 0.5-2 hours to form a transparent and uniform liquid.

[0024] The magnetic nanofluid provided by the present invention uses small-particle Fe3O4 nanoparticles with a large specific surface area, which can effectively reduce the surface tension of DES on the Fe3O4 nanoparticles, facilitate the uniform dispersion of the Fe3O4 nanoparticles, greatly improve the stability of MND, and ensure good quality stability of the MND product; at the same time, it achieves direct, efficient and selective enrichment of PAHs in water bodies such as cigarette butt soaking liquid, which is convenient for use in the quantitative analysis and detection of PAHs in water bodies, simplifying the detection method. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the synthesis of magnetic nanofluid provided in Example 1 of the present invention; Figure 2 Figure 1 is the characterization result of Fe3O4 nanoparticles, where Figure a is the HTEM image of small-size Fe3O4 nanoparticles (S-Fe3O4), Figure b is the HRTEM image of Fe3O4 nanoparticles of common size (C-Fe3O4), and Figure c is the Zeta potential image of Fe3O4 nanoparticles of different sizes in the corresponding magnetic nanofluids; Figure 3 GC-MS / MS-SIM graphs of 16 PAHs standards provided in an embodiment of the present invention; Figure 4 This is a graph showing the time-varying amount of polycyclic aromatic hydrocarbons (PAHs) from cigarette butts into water bodies as provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below through specific implementation methods.

[0027] Unless otherwise specified, the terms used in the present invention are commonly used terms in the relevant field. The technical means used in the examples, such as preparation processes, testing methods, etc., are conventional means well known to those skilled in the art, and the reagents and products used are also commercially available.

[0028] 1. Magnetic nanofluids and their preparation methods Example 1 This embodiment provides a magnetic nanofluid, including DES-coated S-Fe3O4 nanoparticles with a particle size of 7.11±1.39 nm. In this embodiment, the DES is composed of thymol and coumarin uniformly mixed in a molar ratio of 1:2.

[0029] See also Figure 1 This embodiment also provides a method for preparing the magnetic nanofluid, comprising: Preparation of S-Fe₃O₄ nanoparticles: Dissolve 0.128 mol / L ferric ammonium sulfate and 0.064 mol / L ferrous ammonium sulfate in 100 mL of 0.40 mol / L sulfuric acid solution. Next, place 250 mL of 1.0 mol / L NaOH solution in a beaker. Add TX-100 solution to a final concentration of 0.01 mol / L. Heat the solution to 80°C. During this time, add 25 mL of the iron stock solution dropwise to the solution with vigorous stirring. Maintain the temperature at approximately 80°C (but not below 70°C). Continue stirring for 30 minutes after adding the iron stock solution. Cool the solution to room temperature, and magnetically separate the particles from the solution. Wash the solution five times with water (40 mL per wash) and three times with anhydrous ethanol (20 mL per wash). Dry the solution in a vacuum oven at 50°C for 12 hours to obtain S-Fe₃O₄ nanoparticles.

[0030] Preparation of DES: Thymol as hydrogen bond acceptor (HBA) and coumarin as hydrogen bond donor (HBD) were prepared at a molar ratio of 1:2 and magnetic stirring was performed at 80 °C for 30 min to obtain a clear and transparent DES solution.

[0031] Preparation of magnetic nanofluid MND: 50 mg of S-Fe3O4 nanoparticles as magnetic nanoparticles were dispersed in 1 mL of DES, and the mixture was sonicated for about 20 min to disperse the S-Fe3O4 nanoparticles and produce a stable magnetic nanofluid DES-FF.

[0032] Comparative Example 1 This comparative example provides a magnetic nanofluid with a composition and preparation method substantially identical to those of Example 1, the main difference being that C-Fe₃O₄ nanoparticles are used instead of the S-Fe₃O₄ nanoparticles in Example 1. The preparation method for the C-Fe₃O₄ nanoparticles comprises: dissolving 4.0 g of FeCl₃·6H₂O in 120 mL of ethylene glycol with mechanical stirring at 50°C. After complete dissolution, 8.0 g of anhydrous sodium acetate is added and stirred for 60 minutes. The mixture is then transferred to a hydrothermal reactor and maintained at 200°C for 6 hours. The nanoparticles are then purified by magnetic separation and then washed sequentially with deionized water and 95% ethanol 3-5 times to obtain Fe₃O₄ nanoparticles. The Fe₃O₄ nanoparticles are then vacuum-dried at 50°C for 12 hours to obtain the C-Fe₃O₄ nanoparticles.

[0033] The HRTEM images of the S-Fe3O4 nanoparticles used in Example 1 and the C-Fe3O4 nanoparticles used in Comparative Example 1 are as follows: Figure 2 As shown in a-2b. From the HRTEM image, it can be seen that the particle size of S-Fe3O4 synthesized by the water micelle method is 7.03±1.59 nm ( Figure 2 a), so that they can have better dispersion in DES. The particle size of C-Fe3O4 is 169.52±7.89nm( Figure 2 b).

[0034] The surface charge of S-Fe3O4 and C-Fe3O4 nanoparticles in the magnetic nanofluid was measured using a zeta potential analyzer (Malvern Mastersizer Nano ZS ZEN 3600, UK). Figure 2 c. The zeta potential values ​​of S-Fe₃O₄ and C-Fe₃O₄ more intuitively quantify the suspension stability of Fe₃O₄ nanoparticles. The zeta potential of DES-FF (Example 1) containing S-Fe₃O₄ nanoparticles is 4.56±0.37 mV, significantly higher than the zeta potential of 3.32±0.51 mV of the hydrothermally synthesized magnetic nanofluid containing C-Fe₃O₄ nanoparticles (Comparative Example 1). This indicates that the DES-FF of Example 1, which uses S-Fe₃O₄ nanoparticles, has superior stability.

[0035] Furthermore, after 48 hours of continuous stabilization, the S-Fe₃O₄ nanoparticles in the DES-FF prepared in Example 1 and Comparative Example 1 remained well suspended in the DES, resulting in the DES-FF forming a uniform, stable fluid. However, the magnetic nanofluid prepared from hydrothermally synthesized C-Fe₃O₄ nanoparticles exhibited stratification after less than 24 hours of stabilization, indicating that the larger C-Fe₃O₄ particles had begun to aggregate. These findings demonstrate that reducing the size of Fe₃O₄ nanoparticles can effectively improve the stability of the magnetic nanofluid MND.

[0036] Example 2 This embodiment provides a magnetic nanofluid having a composition and preparation method substantially the same as that of Example 1, with the main difference being that the DES in this embodiment comprises thymol and camphor in a molar ratio of 1:1. The preparation method of the DES comprises mixing thymol and camphor in a molar ratio of 1:1, stirring continuously at 90°C for 2 hours, and forming a transparent, uniform liquid.

[0037] Example 3 This embodiment provides a magnetic nanofluid having a composition and preparation method substantially the same as that of Example 1, with the main difference being that the DES in this embodiment comprises thymol and capric acid in a molar ratio of 1:1. The preparation method of the DES comprises mixing thymol and capric acid in a molar ratio of 1:1, stirring continuously at 80°C for 0.5 h, and forming a transparent, uniform liquid.

[0038] Example 4 This embodiment provides a magnetic nanofluid having a composition and preparation method substantially the same as that of Example 1, with the main difference being that the DES in this embodiment comprises thymol and menthol in a molar ratio of 1:1. The preparation method of the DES comprises mixing thymol and menthol in a molar ratio of 1:1, stirring continuously at 90°C for 2 hours, and forming a transparent, uniform liquid.

[0039] 2. Application of magnetic nanofluids in the detection of trace PAHs in water Example 5 This embodiment provides a method for quantitatively detecting the migration of polycyclic aromatic hydrocarbons from cigarette butts into water. The method includes applying magnetic nanofluid to quantitatively detect the migration of polycyclic aromatic hydrocarbons from cigarette butts into water, and includes the following steps: 1) Use a linear smoking machine in ISO smoking mode to smoke cigarettes, collect cigarette butts (cigarette filters), and place 10 butts in 50 mL of deionized water. After soaking for one day, take 5 mL of the butt soaking solution and place it in a glass stoppered colorimetric tube. Add an internal standard solution, and then add 100 µL of magnetic nanofluid MND dropwise to the butt soaking solution. Vortex extract for 5 minutes, then perform magnetic separation and remove the aqueous phase. The internal standard solution mainly consists of 0.004 µg / L phenanthrene-d10, 0.004 µg / L anthracene-d10, and 0.004 µg / L benzo[a]pyrene-d12. Subsequently, add 1 mL of n-hexane as the eluent, vortex for 5 minutes, and filter the eluate through a 0.22 µm organic filter membrane. The filtrate is the PAHs solution to be tested. Step 2) Detect and analyze the PAHs solution using a GC-MS / MS instrument, and establish a standard working curve for each target compound using the internal standard method. Specifically, the test solution is added to the GC-MS / MS instrument for analysis, and the test data is substituted into the standard working curve to calculate the concentrations of naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[123-cd]pyrene, dibenzo[a,h]anthracene, and benzo[g,h,i]perylene in the test solution.

[0040] The chromatographic conditions for GC-MS / MS analysis were as follows: an Agilent DB-5MS column with dimensions of 60 m × 250 μm × 0.25 μm; programmed temperature: 50°C for 1 min, then to 120°C at 20°C / min, then to 170°C at 8°C / min, then to 220°C at 15°C / min, then to 260°C at 5°C / min, and finally to 320°C at 2°C / min, held for 15 min; carrier gas: helium with a purity of ≥99.999% at a flow rate of 1.0 mL / min; inlet temperature: 290°C; injection method: splitless injection; injection volume: 1 µL. The mass spectrometry conditions for this GC-MS / MS analysis were as follows: electron bombardment source: 70 eV; ion source temperature: 320°C; transfer line temperature: 310°C; solvent delay: 11 min; scan mode: positive ion scan; detection mode: multiple reaction monitoring (MRM) (see Table 1). The GC-MS / MS-SIM images of the 16 PAHs standards are shown in Figure 3 .

[0041] Table 1 Quantitative ion pairs, qualitative ion pairs, dwell time, and collision voltage of each compound

[0042] Table 1 (Continued) Quantitative ion pairs, qualifier ion pairs, dwell time, and collision voltage for each compound

[0043] Note: In Table 1, a: quantitative ion, b: qualitative ion.

[0044] Table 2 shows the linear equations, correlation coefficients, limits of detection, and limits of quantification for the 16 PAHs, using a detection limit of 3 times the signal-to-noise ratio (S / N) and a quantification limit of 10 times the S / N. The limits of detection for the 16 PAHs ranged from 1.23 to 6.12 ng / L, and the limits of quantification ranged from 4.10 to 20.40 ng / L.

[0045] Table 2 Linear equations, correlation coefficients, detection limits, and quantification limits of each compound Compound Linear equations Correlation coefficient (r) Detection limit (ng / L) Limit of quantification (ng / L) Naphthalene y=3022.01x+2.71 0.9999 2.69 8.97 Acenaphthylene y=3510.53x+0.85 0.9995 1.23 4.10 Acenaphthene y=6715.77 x+0.58 0.9998 3.14 10.47 Fluorine y=1800.74x+0.42 0.9989 6.12 20.40 Philippines y=3767.03x+0.89 1.0000 2.65 8.83 anthracene y=3656.26x+0.24 0.9999 1.59 5.30 Fluoranthene y=6762.78x+0.29 0.9996 1.45 4.83 pyrene y=7347.56x+0.10 0.9998 1.48 4.93 Benz[a]anthracene y=6321.97 x+0.42 0.9994 2.56 8.53 Qu y=27842.11x+0.72 0.9999 4.53 15.10 Benzo[b]fluoranthene y=38855.19x+0.08 0.9992 4.01 13.37 Benzo[k]fluoranthene y=4508.60x+0.59 0.9999 3.93 13.10 Benzo[a]pyrene y=32142.09 x+0.33 0.9993 4.60 15.33 Indeno[123-cd]pyrene y=18064.54 x+0.17 0.9986 5.03 16.77 dibenzo[a,h]anthracene y=173929.29 x+3.57 0.9991 3.56 11.87 Benzo[g,h,i]perylene y=208594.01 x+7.47 0.9990 4.07 13.57 The same sample was measured six times in parallel within one day and over five days. The relative standard deviation (RSD) of the measurement results represents the intra-day precision and inter-day precision of the method. Spike recovery experiments were also performed at a spike concentration of 200 ng / mL. The results are shown in Table 3.

[0046] Table 3 Spiked recovery and precision of 15 PYs Compound Recovery rate (%) Intra-day precision (n = 6, %) Inter-day precision (n = 5, %) Naphthalene 86.56～108.9 2.53 5.96 Acenaphthylene 89.74～104.8 3.11 6.31 Acenaphthene 81.06～98.63 3.69 7.12 Fluorine 84.50～100.6 2.75 5.42 Philippines 95.66～105.9 2.95 6.78 anthracene 92.63～105.3 3.14 5.14 Fluoranthene 89.88～106.35 3.45 4.96 pyrene 95.75 ～101.9 2.69 6.01 Benz[a]anthracene 84.35～100.8 3.06 5.36 Qu 91.80 ～102.6 3.14 7.13 Benzo[b]fluoranthene 88.55～105.63 4.02 6.54 Benzo[k]fluoranthene 98.55～103.9 3.69 8.01 Benzo[a]pyrene 89.68～105.09 4.35 6.91 Indeno[123-cd]pyrene 97.98～108.5 4.21 7.25 dibenzo[a,h]anthracene 88.45～103.9 1.58 6.34 Benzo[g,h,i]perylene 85.62～112.0 1.63 5.42

[0047] The RSDs for the intra-day and inter-day assessments were consistently below 4.35% and 8.01%, respectively. The results in Table 3 indicate that this method has excellent precision and high spike recovery, making it suitable for the determination of the migration of PAHs from cigarette butts into water.

[0048] Example 6 This example provides a quantitative detection method for the migration of polycyclic aromatic hydrocarbons from cigarette butts into water bodies. The method is basically the same as the detection method provided in Example 9, with the main difference being that the cigarette butts in this example are soaked for 30 days, and the total concentrations of 16 PAHs in the PAHs solutions formed after soaking for 1-30 days are detected and calculated. The results are shown in FIG. Figure 4 shown.

[0049] Depend on Figure 4 The results show that the migration of PAHs from cigarette butts into water bodies gradually increased during the first 1-4 days of immersion, but remained relatively stable after 5 days. This suggests that the dissolution of PAHs from cigarette butts poses a significant threat to aquatic ecosystems.

[0050] In summary, the advantages of the technical solution provided by the embodiments of the present invention are: 1) The polarity of the low eutectic solvent DES used in the designed and synthesized magnetic nanofluid satisfies that it will not dissolve in water, and at the same time can achieve efficient extraction and enrichment of 16 polycyclic aromatic hydrocarbons in water bodies such as cigarette butt soaking liquid; 2) Magnetic separation solves the problem of difficulty in separating trace amounts of 16 polycyclic aromatic hydrocarbons in water bodies after extraction with low eutectic solvents, and simplifies the experimental operation steps; 3) The magnetic Fe3O4 nanoparticles used in the magnetic nanofluid have a small average particle size, which greatly improves the stability of the magnetic nanofluid; 4) The designed and synthesized magnetic nanofluid MND combined with the GC-MS / MS method can significantly improve the sensitivity of the method, providing technical support for studying the kinetic laws of the migration of polycyclic aromatic hydrocarbons in cigarette butts into water bodies.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solutions of the present invention. They should all be included in the scope of the technical solutions claimed for protection by the present invention.

Claims

1. An application of a magnetic nanofluid in the detection of polycyclic aromatic hydrocarbons in water, characterized in that: The magnetic nanofluid includes small-diameter Fe3O4 nanoparticles coated with a deep eutectic solvent, the particle size of the small-diameter Fe3O4 nanoparticles is 5.5-8.5 nm, and the DES is a thymol-based hydrophobic deep eutectic solvent.

2. The use according to claim 1, characterized in that The deep eutectic solvent is mainly composed of a hydrogen bond acceptor and a hydrogen bond donor in a molar ratio of 1:1-2, wherein the hydrogen bond acceptor is thymol and the hydrogen bond donor includes at least one of coumarin, camphor, capric acid and menthol.

3. The use according to claim 1 or 2, characterized in that In the magnetic nanofluid, the concentration of the small-diameter Fe3O4 nanoparticles is 20-100 mg / mL.

4. The use according to claim 3, characterized in that The application is manifested in at least one of the following aspects: 1) Application of the magnetic nanofluid in enriching trace PAHs in water; 2) Application of the magnetic nanofluid combined with GC-MS / MS method in the detection of trace PAHs in water.

5. The use according to claim 1, 2 or 4, characterized in that: The polycyclic aromatic hydrocarbons are at least one of naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[123-cd]pyrene, dibenzo[a,h]anthracene, benzo[g,h,i]perylene, etc.

6. A method for quantitatively detecting the migration of polycyclic aromatic hydrocarbons from cigarette butts into water, comprising the steps of: First, a vortex extraction treatment was performed on the water sample soaked with a magnetic nanofluid, and then MND was magnetically separated and eluted with an eluent to prepare a PAH solution to be tested; wherein, The magnetic nanofluid comprises small-sized Fe3O4 nanoparticles coated with a deep eutectic solvent, wherein the particle size of the small-sized Fe3O4 nanoparticles is 5.5-8.5 nm, and the deep eutectic solvent is a thymol-based hydrophobic deep eutectic solvent; The polycyclic aromatic hydrocarbon solution to be tested is subjected to GC-MS / MS analysis.

7. The detection method according to claim 6, characterized in that The deep eutectic solvent is mainly composed of a hydrogen bond acceptor and a hydrogen bond donor in a molar ratio of 1:1-2, wherein the hydrogen bond acceptor is thymol, and the hydrogen bond donor includes at least one of coumarin, camphor, capric acid and menthol.

8. The detection method according to claim 6 or 7, characterized in that The method for preparing the PAHs solution to be tested includes: smoking cigarettes using a linear smoking machine in ISO smoking mode, collecting cigarette butts, placing 5-10 cigarette butts in 10-100 mL of deionized water, and soaking them for 1-30 days; taking 1-10 mL of the cigarette butt soaking solution into a stoppered colorimetric tube, adding an internal standard solution and mixing; then dropwise adding the magnetic nanofluid to perform vortex extraction; then performing magnetic separation to remove the aqueous phase; then adding the eluent to perform vortex elution, and filtering the eluted phase with a 0.22 μm organic filter membrane.

9. The detection method according to claim 8, characterized in that The amount of the magnetic nanofluid added is 100-500 μL, and the extraction time is 5-30 min; the internal standard solution includes phenanthrene-d10 with a concentration of 0.003-0.010 μg / L, anthracene-d10 with a concentration of 0.003-0.010 μg / L, and benzo[a]pyrene-d12 with a concentration of 0.003-0.010 μg / L.

10. The detection method according to claim 9, characterized in that: The eluent is n-hexane, the amount of the eluent is 0.5-1 mL, and the elution time is 1-5 min.

11. A magnetic nanofluid, characterized in that: The invention comprises small-sized Fe3O4 nanoparticles coated with a low eutectic solvent, wherein the particle size of the small-sized Fe3O4 nanoparticles is 5.5-8.5 nm, and the low eutectic solvent is a thymol-based hydrophobic low eutectic solvent.

12. The magnetic nanofluid according to claim 11, characterized in that The deep eutectic solvent is mainly composed of a hydrogen bond acceptor and a hydrogen bond donor in a molar ratio of 1:1-2, wherein the hydrogen bond acceptor is thymol and the hydrogen bond donor includes at least one of coumarin, camphor, capric acid and menthol.

13. A method for preparing the magnetic nanofluid according to claim 11 or 12, comprising: The small-sized Fe3O4 nanoparticles are dispersed in the deep eutectic solvent and then subjected to ultrasonic treatment.

14. The preparation method according to claim 13, characterized in that The preparation method of the small-size Fe3O4 nanoparticles comprises: using ferric ammonium sulfate, ferrous ammonium sulfate and TX-100 solution as raw materials, performing a hydrothermal reaction at 70-90°C for 20-40 minutes, and preparing the small-size Fe3O4 nanoparticles.

15. The preparation method according to claim 13, characterized in that The preparation method of the deep eutectic solvent comprises: mixing the hydrogen bond acceptor and the hydrogen bond donor in a molar ratio of 1:1-2, and continuously stirring at 70-90°C for 0.5-2 hours to form a transparent and uniform liquid.

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