Method for rapidly detecting enrofloxacin adsorbed on micro-plastic surface in water body

Abstract

The invention discloses a method for rapidly detecting enrofloxacin adsorbed on the surface of micro-plastic in a water body, and belongs to the field of rapid detection of hazardous substances. The detection method comprises the following steps: filtering a collected water sample through a metal screen, subpackaging the filtered water sample into a centrifuge tube for centrifugation, collecting an upper solution, carrying out vacuum filtration, and intercepting micro-plastic particles on the surface of a filter membrane; and dropwise adding nano silver sol and a desorption solvent on the surface of the filter membrane enriched with the micro-plastic to form a'coffee ring 'structure with a compact edge, collecting an SERS signal in the'coffee ring' region, substituting the signal intensity at 1353cm <-1 > into the standard curve model, and calculating the content of enrofloxacin adsorbed on the surface of the micro-plastic in the water sample to be detected. According to the method, high-sensitivity rapid detection of the enrofloxacin on the surface of the micro-plastic in a water body is realized, the sensitivity is improved by 100 times compared with that of a traditional method, meanwhile, complex pretreatment steps such as weighing of the micro-plastic are omitted, and the detection cost is greatly reduced.

Description

Technical Field

[0001] The present invention relates to a rapid detection method for enrofloxacin adsorbed on the surface of microplastics in water bodies, belonging to the field of rapid detection of hazardous substances. Background Art

[0002] Whether traditional plastics or degradable plastic products, they all generate plastic fragments after being discarded into the environment through processes such as abrasion, oxidation, hydrolysis, and aging. Currently, microplastics are widely present in aquatic systems, and their small volume, variable morphology, and potential toxicity pose a major threat to aquatic organisms. Microplastics often coexist with other pollutants in water bodies. Their hydrophobicity and high specific surface area make them carriers of hydrophobic organic pollutants in the aquatic environment, thereby changing the migration process of pollutants, affecting their bioavailability and ecological toxicity, and posing a threat to human health through the food chain. Developing a simple, low-cost, and sensitive method for detecting pollutants adsorbed on the surface of microplastics in water bodies is of great significance.

[0003] Currently, methods for detecting pollutants on microplastics include gas chromatography-mass spectrometry (GC-MS), headspace-gas chromatography (GC-ECD), high-performance liquid chromatography-fluorescence method (HPLC-FD), and inductively coupled plasma mass spectrometry (ICP-MS), etc. Although these methods have high sensitivity and reliability, they have certain limitations, including complex sample preparation processes, the need for expensive equipment and operations, and the possibility of introducing contamination or causing losses during the extraction and separation processes.

[0004] Surface-enhanced Raman scattering (SERS) technology relies on metal nanostructures and can significantly enhance the Raman scattering signal of molecules, mainly achieved through the electromagnetic enhancement (EM) mechanism. EM generates a strong electromagnetic field on the surface of metal nanoparticles through local surface plasmon resonance (LSPR) to enhance the Raman signal. Theoretically, the enhancement coefficient of SERS technology can be as high as 10 10 or higher. Compared with traditional microplastic detection methods, this method has the advantages of simple steps, less consumption of chemical reagents, short detection time, and the ability to achieve in-situ detection of pollutants on the surface of microplastics. However, when directly applying SERS to detect pollutants on the surface of microplastics, there are still some deficiencies, such as relatively weak Raman signal intensity and poor stability, resulting in low detection accuracy and sensitivity. Summary of the Invention

[0005] [Technical Problem]

[0006] When SERS in the prior art is used to detect pollutants on the surface of microplastics, there are still factors such as relatively weak Raman signal intensity and poor stability, resulting in low detection accuracy and sensitivity.

[0007] [Technical Solution]

[0008] Aiming at the defects and deficiencies of the existing technology, the purpose of the present invention is to provide a rapid detection method for enrofloxacin adsorbed on the surface of microplastics in water. This method separates microplastics in water by centrifugation - membrane filtration and enriches them on the surface of the filter membrane. Then, silver sol and desorption solvent are dropped onto the microplastic enrichment area. Under the combined action of capillary action and evaporation effect, silver particles in the sol aggregate at the edge of the droplet to form a circular deposit, that is, a "coffee ring" is formed. At the same time, the organic solvent desorbs enrofloxacin adsorbed on the surface of the microplastics and is captured by silver particles, greatly enhancing the SERS signal of enrofloxacin, improving the sensitivity and accuracy of SERS detection of enrofloxacin. Compared with the traditional detection method, it saves costs and improves the detection efficiency.

[0009] In order to achieve the above - mentioned purpose, the following technical solutions are provided:

[0010] The present invention provides a rapid detection method for enrofloxacin adsorbed on the surface of microplastics in water, and the method comprises the following steps:

[0011] (1) Sample pretreatment

[0012] After filtering the collected water sample through a metal screen, it is placed in a centrifuge tube for centrifugation, and the upper - layer solution is collected for vacuum filtration. The microplastic particles are retained on the surface of the filter membrane.

[0013] (2) Determination of the enrofloxacin content in the water sample

[0014] Drop nano - silver sol and desorption solvent on the surface of the filter membrane enriched with microplastics in step (1) to form a "coffee ring" structure with a dense edge. Collect the SERS signal in the "coffee ring" area, and substitute the signal intensity at 1353 cm -1 into the standard curve model to calculate the enrofloxacin content adsorbed on the surface of microplastics in the water sample to be measured.

[0015] In one embodiment, the water includes the water area and surrounding waters of aquaculture areas, the effluent from urban sewage treatment plants, and the rivers and lake waters affected by agricultural runoff.

[0016] In one embodiment, the pore diameter of the metal screen in step (1) is 3 - 5 mm.

[0017] In one embodiment, the centrifugation parameters in step (1) are 8000 - 12000 r / min and the time is 10 - 15 min; preferably 8000 r / min and 15 min.

[0018] In one embodiment, the centrifugation process in step (1) is repeated 3 - 6 times; preferably 3 times.

[0019] In one embodiment, the filter membrane used in the vacuum filtration in step (1) is a cellulose acetate filter membrane with a pore size of 0.22 - 1.2 μm.

[0020] In one embodiment, the nano - silver sol in step (2) is prepared by the method of reducing AgNO3 with trisodium citrate.

[0021] In one embodiment, the specific preparation process of the nano - silver sol is as follows: Weigh silver nitrate powder and dissolve it in ultrapure water. When the solution is slightly boiling, add a 1% sodium citrate solution by mass fraction, and keep boiling for 15 - 20 min. The solution gradually changes from colorless to slightly yellow, dark yellow, and finally gray - green. Then, lower the temperature to 100 °C, keep this temperature for cooling and refluxing for 20 - 25 min, turn off the heating, keep stirring, and cool and reflux to room temperature to obtain it.

[0022] In one embodiment, the desorption solvent in step (2) is a 50 - 100% methanol solution; preferably a 70% methanol solution.

[0023] In one embodiment, the volume ratio of the nano - silver sol to the desorption solvent in step (2) is 1 - 5:1 - 5; preferably 1:1.

[0024] In one embodiment, the parameters set for collecting SERS signals in step (2) are: the excitation wavelength is (785 ± 0.5) nm, the spectral scanning range is 200 - 3200 cm -1 , the integration time is set to 2000 - 3000 ms, the laser power is 5 mW; the detection time is selected as 10 - 90 s; preferably 70 s.

[0025] In one embodiment, in step (2), calculating the content m of enrofloxacin adsorbed on the surface of microplastics in the water sample to be measured ENR测 ; it also includes using a 20 - fold optical microscope to count the number N of microplastics in the "coffee ring" area; calculating the average mass of enrofloxacin adsorbed on the surface of a single microplastic according to the following formula

[0026] In one embodiment, the process of establishing the standard curve model in step (2):

[0027] 1) Add known - mass clean microplastic particles to a series of concentration enrofloxacin standard solutions respectively, and oscillate at a constant temperature of 25 ± 1 °C for 72 h to make the microplastics and enrofloxacin reach adsorption equilibrium, and measure the total adsorption amount Q of enrofloxacin on the microplastics by HPLC method 总 ;

[0028] Q 总 = ((C0 - C e ) × V - α)

[0029] Among them, in the formula Q 总 is the total adsorption amount of enrofloxacin on polypropylene microplastics; C0 and C e are the initial concentration and equilibrium concentration (mg / L); V (L) is the solution volume; α (mg) is the blank loss;

[0030] 2) Filter the solutions after equilibration in step 1) through a vacuum filtration device. Use a cellulose acetate filter membrane with a pore size of 0.45 μm to intercept the microplastics. Drop silver sol and methanol onto the surface of the filter membrane. After the droplets dry, a "coffee ring" structure is formed. Collect the Raman spectral signals in the "coffee ring" region. With the characteristic peak intensity as the ordinate and the logarithm of the mass of enrofloxacin adsorbed on the surface of the microplastics as the abscissa, establish a standard curve model.

[0031] In one embodiment, the standard curve model is y = 2130.07x + 5163.80, and the correlation coefficient R 2 = 0.960.

[0032] The present invention also provides the application of the above-mentioned method in the field of hazard detection.

[0033] Beneficial effects:

[0034] (1) Through the synergistic enhancement technology of centrifugal enrichment and coffee ring effect, combined with the single-particle adsorption amount calculation model, the present invention realizes the highly sensitive and rapid detection of enrofloxacin on the surface of microplastics in water. The detection limit of enrofloxacin adsorbed on microplastics is as low as 0.0483 ng, and the sensitivity is 100 times higher than that of traditional methods. At the same time, complex pretreatment steps such as weighing microplastics are omitted, the detection time is greatly shortened, and the reagent cost is reduced by 60%;

[0035] (2) Based on the selective desorption of methanol and the spatial confinement effect of silver sol, the influence of microplastic particle size on the detection signal can be greatly reduced, and the direct quantification of the adsorption amount (ng / piece) of a single microplastic is realized for the first time, breaking through the limitation of the traditional mass unit (ng / g), and the individual pollution load of microplastics in actual water bodies (such as aquaculture wastewater, coastal water) can be quickly evaluated. Description of the drawings

[0036] Figure 1 is the detection flow chart of enrofloxacin adsorbed on the surface of microplastics of the present invention;

[0037] Figure 2 is the change diagram of Raman spectral signals with time in Example 1;

[0038] Figure 3Detection limit test and linear fitting diagram of enrofloxacin adsorbed on microplastics obtained in pure water and aquaculture water backgrounds; (a) Detection limit test diagram of pure water system; (b) Linear fitting diagram of pure water system; (c) Detection limit test diagram of aquaculture water system; (d) Linear fitting diagram of aquaculture water system;

[0039] Figure 4 Data graph of the influence of different plastic particle sizes on the detection recovery rate;

[0040] Figure 5 Data graph of the influence of different centrifugation conditions on the recovery rate of low-density microplastics; (a) Centrifugation speed; (b) Number of centrifugation times;

[0041] Figure 6 Detection effect diagram of enrofloxacin adsorbed on microplastics in actual aquaculture water bodies;

[0042] Figure 7 HPLC detection standard curve diagram of enrofloxacin;

[0043] Figure 8 Raman detection effect comparative diagram of cellulose acetate filter membrane and tin foil as microplastic carrier materials; (a) Raman signal intensity diagram; (b) Repeatability test result diagram of tin foil as microplastic carrier material. Specific implementation mode

[0044] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention. The following specific implementation modes further describe the present invention.

[0045] Example 1

[0046] A rapid detection method for enrofloxacin adsorbed on the surface of microplastics in water bodies includes the following steps:

[0047] (1) Preparation of silver nanosol

[0048] Weigh 0.018 g of silver nitrate powder, then dissolve it in 100 mL of ultrapure water. When the solution is slightly boiling, add 2 mL of 1% sodium citrate solution, and keep boiling for 15 - 20 min. The solution gradually changes from colorless to slightly yellow, dark yellow, and finally gray-green. Then cool the temperature to 100 °C, keep this temperature for cooling and refluxing for 25 min, turn off the heating, keep stirring, and cool and reflux to room temperature to obtain silver nanosol, which is placed in a 4 °C refrigerator for standby;

[0049] (2) Establishment of standard curve

[0050] Using ultrapure water and aquaculture water samples (pre-filtered to remove suspended particles and not detected with enrofloxacin) as background solutions, a series of standard concentration enrofloxacin solutions (0.1 - 1000 μg / L) were prepared. Weigh 10 mg of polypropylene microplastics with a particle size of 500 μm and immerse them separately into 100 mL of enrofloxacin solutions with different concentrations; place the enrofloxacin solutions containing microplastics in a constant temperature shaker incubator at 25 °C and shake continuously for 72 h. After adsorption equilibrium, vacuum filtration is used to enrich the microplastics on a 0.45 μm cellulose acetate filter membrane and store them in a glass petri dish with a lid;

[0051] Use HPLC to detect the equilibrium concentration of enrofloxacin in the filtered solution, and calculate the mass of enrofloxacin adsorbed on the microplastics according to the following formula:

[0052] Q 总 =((C0 - C e )×V - a)

[0053] where, in the formula, Q 总 is the total amount of enrofloxacin adsorbed on the polypropylene microplastics; C0 and C e are the initial concentration and equilibrium concentration (mg / L); V (L) is the solution volume; α (mg) is the blank loss;

[0054] (3) SERS spectral detection

[0055] On the surface of the microplastic sample on the cellulose acetate filter membrane in the glass petri dish with a lid, 3 μL of silver nanosol and 3 μL of 70% methanol solution are successively added. With the capillary action of the filter membrane and the evaporation effect of the liquid droplets, silver nanoparticles self-assemble to form a "coffee ring" structure with a dense edge; at the same time, methanol desorbs the enrofloxacin adsorbed on the surface of the microplastics and is captured by the silver nanoparticles as the liquid flows;

[0056] Collect SERS signals in the formed "coffee ring" region. When collecting the Raman spectrum, the set parameters are: excitation wavelength is (785 ± 0.5) nm, the spectral scanning range is 200 - 3200 cm -1 , the integration time is set to 2000 - 3000 ms, and the laser power is 5 mW; the change of the spectral signal with time is as Figure 2 shown, and the subsequent detection time is selected as 70 s;

[0057] Taking the signal intensity at 1353 cm -1 as the ordinate and the logarithm of the mass of enrofloxacin adsorbed on the surface of the microplastics as the abscissa, establish a standard curve equation; Figure 3 Shows the SERS detection results of the enrofloxacin content adsorbed on the surface of the prepared microplastic particles in the pure water system (a, b) and the aquaculture water system (c, d).

[0058] The SERS detection method has a good linear relationship in the range of 0.0483 ng - 399.62 ng for the quality detection of enrofloxacin adsorbed on the surface of microplastics in the background of ultrapure water. The fitted standard curve is y = 1420.77x + 4439.66, and the correlation coefficient R 2 = 0.9766; SERS detection was performed on the mass of enrofloxacin adsorbed by microplastics that reached adsorption equilibrium in the aquaculture water body. The results showed a good linear relationship in the range of 1.6064 - 55.496 ng. The fitted standard curve is y = 2130.07x + 5163.80, and the correlation coefficient R 2 = 0.960.

[0059] Example 2

[0060] Referring to the method of Example 1, enrofloxacin solutions with initial concentrations of 50, 100, and 500 μg / L were prepared using the aquaculture water of Litopenaeus vannamei collected from three different regions (excluding suspended particles) as the background solution, and 10 mg of polypropylene microplastics with a particle size of 500 μm were added respectively. The adsorption process was simulated and SERS detection was performed on the content of pollutants adsorbed on the surface of microplastics, and the HPLC detection results were compared. The signal intensity at 1353 cm -1 was used to calculate the spiked recovery rate; the results are shown in Table 1:

[0061] Table 1 Spiked recovery analysis results of samples (n = 6)

[0062]

[0063]

[0064] As can be seen from the results in Table 1, for the SERS detection of the content of enrofloxacin adsorbed on the surface of microplastics, the recovery rate is between 90.11 - 114.05%, meeting the detection standard, indicating that this method is applicable to the determination of the content of enrofloxacin adsorbed on the surface of microplastics in water bodies.

[0065] Example 3 Explore the influence of different particle sizes of microplastics on the detection results

[0066] 10 mg of polypropylene microplastics with different particle sizes (0.1 mm, 0.5 mm, 1 mm, 2 mm, 5 mm) were respectively immersed in 100 mL of 1000 μg / L enrofloxacin solution and shaken for 72 h until adsorption equilibrium was reached. Then, filtration was carried out to enrich the microplastics on a 0.45 μm cellulose acetate filter membrane, and the filtrate was collected to detect the total adsorption amount Q on the microplastics using HPLC;

[0067] The Raman detection of microplastics on the cellulose acetate filter membrane was carried out according to the method of Example 1. The intensity of the characteristic peak at 1353 cm-1 was extracted, and the mass of enrofloxacin on the microplastics in the coffee ring area was calculated through the standard curve. The results were compared with those of liquid chromatography and the recovery rate was calculated.

[0068] As Figure 4 shown, the recovery rates of enrofloxacin on five groups of microplastics with particle sizes of 0.1 - 5 mm were 89.6% - 96.3% (RSD = 3.21%), indicating that the detection results were independent of the particle size. This method could accurately quantify the pollutant load of microplastics with mixed particle sizes.

[0069] Example 4 Optimization of SERS Signal and Stability

[0070] (1) Referring to Example 1, 10 mg of polypropylene microplastics with a particle size of 500 μm were weighed and soaked in 100 mL of enrofloxacin solution at a concentration of 1000 μg / L. The enrofloxacin solution containing microplastics was placed in a constant temperature shaking incubator at 25 °C and shaken continuously for 72 h. After adsorption equilibrium, vacuum filtration was carried out to retain the microplastics on a 0.45 μm cellulose acetate filter membrane. The experiments were carried out for detection according to the settings in Table 2, with 5 parallels in each group: A: volume of silver sol (1 - 5 μL); B: volume of methanol (1 - 5 μL); C: methanol concentration (50% - 100%):

[0071] (2) Using a 785 nm laser Raman spectrometer (laser power 5 mW, integration time 2000 ms), 5 detection points were evenly selected at the edge of the coffee ring to collect the signals of the enrofloxacin characteristic peak (1353 cm-1), and the average signal intensity and relative standard deviation (RSD) were calculated. At the same time, an optical microscope (100×) was used to observe the coffee ring morphology, and the diameter and edge width of the coffee ring (the transition width of the silver particle deposition zone from the outer edge to the internal sparse area) were measured.

[0072] Table 2 Results under different treatment conditions

[0073] Group A (μL) B (μL) C(％) Coffee ring diameter (mm) Coffee ring edge width (μm) SERS intensity (a.u.) 1 1 1 50 2.3±0.2 120±15 3506±329 2 1 3 70 3.1±0.3 180±20 5008±239 3 1 5 100 3.8±0.4 250±30 5660±272 4 3 1 100 3.5±0.2 200±18 6201±209 5 3 3 70 4.0±0.1 210±25 6951±244 6 3 5 50 4.5±0.3 350±40 5350±257 7 5 1 70 4.2±0.3 220±20 4707±209 8 5 3 100 4.8±0.4 300±35 6252±213 9 5 5 50 5.5±0.5 400±50 4039±258 Control group 3 3 0 3.9±0.2 150±12 1752±274

[0074] As can be seen from the table results, when the amount of silver sol was 3 μL, the methanol concentration was 70%, and the methanol addition amount was 3 μL (Group 5), the coffee ring morphology and SERS signal intensity were both the best, and its relative standard deviation (RSD, RSD = S / x * 100%, where x represents the sample average value and S represents the sample standard deviation) was less than 5%, indicating that the Ag NPs were evenly distributed on the coffee ring, with good repeatability. At the same time, this optimized condition ensured the maximum enhancement effect in the hot spot area, so that the detection sensitivity reached the optimum.

[0075] Example 5

[0076] (1) Take 1 g each of low-density polypropylene microplastics (PP, ρ = 0.91 g / cm 3 ) and polyethylene microplastics (PE, ρ = 0.92 g / cm 3 ), and disperse them separately in 1 L of aquaculture water samples (pre-filtered through a 0.45 μm filter membrane to remove suspended particles) to prepare microplastic simulated water samples with a concentration of 1 mg / mL;

[0077] (2) Test the following conditions separately: centrifuge 5 times at 2000 - 12000 r / min, and centrifuge 1 - 6 times at 8000 r / min;

[0078] (3) Take 200 mL of the simulated water sample, and aliquot it into 50 mL polypropylene centrifuge tubes; centrifuge according to the preset parameters, discard the lower clear liquid, and collect the upper floating microplastics; transfer the collected microplastics to a pre-weighed cellulose acetate filter membrane (pore size 0.45 μm), vacuum filter, dry and weigh, and calculate the recovery rate (%) of the microplastics;

[0079] The results are as Figure 5 shown. When centrifuging 3 times repeatedly at 8000 r / min, the recovery rate of low-density microplastics can reach 94.2 ± 4.9%, and with the increase of the rotation speed and the number of centrifugation times, there is no significant improvement in the recovery rate (p > 0.05).

[0080] Example 6

[0081] Detection of enrofloxacin adsorbed on the surface of microplastics in aquaculture water bodies includes the following:

[0082] (1) Take 1 L of aquaculture water sample, and pre-filter large particulate matter using a 5 mm metal sieve. Subsequently, aliquot the pre-filtered water sample into centrifuge tubes, and centrifuge for 15 minutes under the centrifugation condition of 8000 r / min. After centrifugation, low-density microplastics will concentrate on the upper layer of the solution. Use a metal sampler to suck and retain the upper liquid, and repeat this centrifugation process three times to further enrich the microplastics; the collected upper solution is vacuum filtered, and a cellulose acetate filter membrane with a pore size of 0.45 μm effectively intercepts the microplastic particles on the surface of the filter membrane;

[0083] Drop 3 μL of silver nanosol and 3 μL of 70% methanol solution on the filter membrane enriched with microplastics, and collect Raman spectra in the formed coffee ring area. The set Raman detection parameters are: excitation wavelength is (785 ± 0.5) nm, spectral scanning range is 200 - 3200 cm -1 , the integration time is set to 2000 - 3000 ms, and the laser power is 5 mW; the Raman spectra are as Figure 6 shown. By comparing with the peaks of the standard sample, it is found that the characteristic Raman peaks of enrofloxacin can be detected;

[0084] (2) Determination of the content of enrofloxacin adsorbed on the surface of microplastics in the aquaculture water body

[0085] Based on the standard curve model constructed in Example 1, the mass of enrofloxacin collected from the coffee ring region was calculated to be 2.0804 ng. Using a 20-fold optical microscope, the number of microplastics in the coffee ring region was counted as 9, and the average size was 256 μm. According to this result, the loading capacity of this microplastic sample for enrofloxacin was estimated to be 0.2331 ng / piece.

[0086] Comparative Example 1

[0087] Verify the technical advantages of the "membrane filtration enrichment-in-situ SERS detection" of the present invention compared with the traditional "microplastic transfer-solvent extraction" scheme in avoiding sample loss and simplifying the operation process.

[0088] (1) Take 10 mg of polypropylene microplastics with a particle size of 100 μm and soak them in 100 mL of enrofloxacin solution prepared with ultrapure water at a concentration of 1 mg / L until adsorption equilibrium is reached. Enrich the microplastic particles on the surface of the membrane by vacuum filtration. It can be detected by HPLC that the equilibrium adsorption capacity Q of 10 mg of microplastics 总 = 9.991 μg;

[0089] (2) Refer to the method of Example 1 to perform Raman detection on the microplastics on the cellulose acetate membrane, extract the characteristic peak intensity at 1353 cm -1 , calculate the mass m of enrofloxacin on the microplastics in the coffee ring region through the standard curve ENR测 , and calculate Q i according to the area (A) of the coffee ring region and the effective filtration area (S 总 ) of the membrane, and calculate the recovery rate by comparing with the HPLC result in (1).

[0090] (3) Gently scrape the microplastic particles on the membrane onto a centrifuge tube using a non-polluting scraper, ensuring that there is as little microplastic residue on the membrane as possible. Then add a fixed volume (5 mL) of 70% methanol solution to the centrifuge tube, ultrasonically vibrate for 10 min for desorption, and then perform HPLC detection after passing through a 0.22 μm membrane. Calculate Q Figure 7 according to the established standard curve( 总 ) and the fixed volume (5 mL), and calculate the recovery rate by comparing with the HPLC result in (1).

[0091] Table 3. Comparison of detection performance between membrane filtration enrichment-in-situ SERS detection and traditional methods

[0092]

[0093]

[0094] The experimental results are shown in Table 3: Compared with the transfer-solvent desorption method, the filter membrane enrichment-SERS in-situ direct detection method involved in the present invention does not require a complex solvent extraction process, has the advantages of simple operation and high recovery rate, and is applicable to water quality assessment, pollutant monitoring, and tracing the spread of surface-adsorbed toxic substances in the aquatic environment.

[0095] Comparative Example 2

[0096] Comparison of the differences in SERS signal intensity when using a filter membrane and tin foil as the carrier materials

[0097] Referring to the method of Example 1, 10 mg of polypropylene microplastics with a particle size of 500 μm were respectively immersed in 100 mL of enrofloxacin solution prepared with ultrapure water at a concentration of 1 mg / L until adsorption equilibrium was reached; the microplastic particles were enriched on the surface of the filter membrane by vacuum filtration, which was the filter membrane group; the filtered microplastic particles were gently scraped and transferred onto tin foil using a pollution-free scraper and made to be as evenly distributed as possible, which was the tin foil group. 3 μL of silver sol and 3 μL of 70% methanol solution were added dropwise to the area where the microplastics were distributed. After the solvent evaporated to a semi-dry state, SERS signals were collected in the coffee ring area and the intensities were recorded. The results are as Figure 8 shown.

[0098] It can be seen from the results that when tin foil was used as the carrier material, the SERS signal intensity was only 60.81% of that of the filter membrane group, and the repeatability deteriorated significantly (RSD > 25%). This is because the porous structure of the filter membrane drives the directional migration of droplets through capillary action, forming a dense ring arrangement of silver particles; the hydrophobicity of the tin foil surface leads to a random droplet contraction mode, and the silver particles and the target molecules cannot be co-enriched. It is proved that the filter membrane substrate defined in the present invention is irreplaceable for achieving high-sensitivity and high-stability detection.

[0099] The embodiments provided above are not intended to limit the scope covered by the present invention, nor are the described steps intended to limit the order of their execution. Obvious improvements made by those skilled in the art to the present invention in combination with the existing common general knowledge also fall within the protection scope defined by the claims of the present invention.

Claims

1. A rapid detection method for enrofloxacin adsorbed on the surface of microplastics in water, characterized in that: The method comprises the following steps: (1) Sample pretreatment The collected water sample was filtered through a metal mesh and then placed in a centrifuge tube for centrifugation. The upper layer of solution was collected and vacuum filtered, and the microplastic particles were retained on the surface of the filter membrane. The filter membrane used for the vacuum filtration was a cellulose acetate filter membrane with a pore size of 0.22-1.2 μm. (2) Determination of enrofloxacin content in water samples Nanosilver sol and desorption solvent were added to the surface of the filter membrane enriched with microplastics in step (1) to form a "coffee ring" structure with dense edges. SERS signals were collected in the "coffee ring" area at 1353 cm -1 The signal intensity at the location is brought into the standard curve model to calculate the content of enrofloxacin adsorbed on the surface of microplastics in the water sample to be tested; the desorption solvent is 50-100% methanol solution.

2. The method according to claim 1, characterized in that The water bodies include aquaculture areas and surrounding waters, discharge water from urban sewage treatment plants, and rivers and lakes affected by agricultural runoff.

3. The method according to claim 1, characterized in that: The hole diameter of the metal screen in step (1) is 3-5 mm.

4. The method according to claim 1, characterized in that The centrifugal parameters in step (1) are 8000-12000 r / min and the time is 10-15 min.

5. The method according to claim 1, characterized in that The centrifugation process in step (1) is repeated 3 to 6 times.

6. The method according to claim 1, characterized in that The nano silver sol in step (2) is prepared by reducing AgNO3 with trisodium citrate.

7. The method according to claim 1, characterized in that The desorption solvent in step (2) is 70% methanol solution.

8. The method according to claim 1, characterized in that The volume ratio of the nano silver sol to the desorption solvent in step (2) is 1-5:1-5.

9. The method according to claim 1, characterized in that: The parameters for collecting SERS signals in step (2) are as follows: the excitation wavelength is (785 ± 0.5) nm, and the spectral scanning range is 200-3200 cm -1 , the integration time is set to 2000-3000ms, the laser power is 5mW; the detection time is selected to be 10-90s.

10. Use of the method according to any one of claims 1 to 9 in the field of hazardous object detection.

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