A method for quantitative fluorescence analysis of polystyrene microplastics and its application
The fluorescence intensity of polystyrene microplastics was measured using a fluorescence spectrophotometer, which solves the problems of complexity and inaccuracy in existing microplastic quantification methods. It provides a rapid and accurate quantification method that is applicable to different water media and aged microplastics, and has wide applicability and high accuracy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-12-09
- Publication Date
- 2026-04-07
AI Technical Summary
Existing methods for quantifying microplastics are cumbersome and inaccurate, making it difficult to effectively quantify the property changes of aged microplastics, and lacking simple and rapid quantitative analysis methods.
The fluorescence intensity of polystyrene microplastics was measured using a fluorescence spectrophotometer, and the concentration of polystyrene microplastics in water was calculated using the standard curve method. Quantitative analysis was performed using the fluorescence characteristics of polystyrene at specific wavelengths.
It enables rapid and accurate quantification of polystyrene microplastics, is applicable to different natural water media and environmental aging levels, is simple to operate and is not affected by salt ions and pH value, and has a wide detection range.
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Figure CN115931804B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for the quantitative analysis of polystyrene microplastics, specifically describing a method that utilizes the photofluorescence properties of polystyrene microplastics to determine and quantify their fluorescence intensity using a fluorescence spectrophotometer. This method is simple to operate, highly accurate, and requires no additional reagents, making it suitable for the quantitative analysis of polystyrene microplastics in water. Background Technology
[0002] As a new type of persistent organic pollutant, microplastics present both analytical and removal challenges. In addition to primary microplastics, plastics entering the environment can also generate secondary (aged) microplastics under the influence of physical and chemical factors. These microplastics are often micrometer- or nanometer-sized and can enter the food chain through biological ingestion, increasing human health risks.
[0003] Due to limitations in methods for quantifying microplastics, research on microplastics remains focused on morphological observation and aging properties. However, quantifying microplastics is essential for assessing their removal effectiveness. Existing methods for quantifying microplastics, such as pyrolysis-gas chromatography-mass spectrometry (GC-MS) and flow cytometry, rely on microplastic pretreatment, which is cumbersome and has limited accuracy. Microscopic counting is limited by the heterogeneity of microplastic particle size, and there is no reasonable quantitative analysis method for the property changes of aged microplastic particles.
[0004] Therefore, developing a simple and rapid method for quantifying microplastics is crucial for microplastic research.
[0005] Organic compounds containing unsaturated groups fluoresce at specific wavelengths. These pollutants are often partitioned based on the location of their fluorescence peaks to facilitate the qualitative analysis of unknown samples. Polystyrene, due to its benzene rings, fluoresces under ultraviolet light, similar to other substances with unsaturated bonds. Therefore, based on this characteristic of polystyrene microplastics, the concentration of polystyrene microplastics in water can be inferred by measuring the fluorescence intensity of the benzene rings. This is a rapid and accurate quantitative method that solves the problem of evaluating the effectiveness of microplastic removal research and is expected to promote and advance scientific research in this area. Summary of the Invention
[0006] To address the lack of current methods for quantifying microplastics and the complexity and inaccuracy of existing methods, this invention relates to linking the mass concentration of polystyrene microplastic suspensions with their fluorescence intensity at a specific wavelength, thereby achieving accurate quantification of polystyrene microplastics in water. This is a method that facilitates laboratory research on microplastic removal, offering advantages such as simple operation, wide applicability, and high accuracy.
[0007] The present invention also provides the application of the above-described method for quantifying polystyrene microplastics in different natural aquatic media, including tap water, lake water, river water, and sludge supernatant.
[0008] The present invention also provides the application of the above-described method for polystyrene microplastics in polystyrene microplastics with different environmental aging degrees.
[0009] The method for quantitative fluorescence measurement of polystyrene microplastics according to the present invention adopts the following technical solution:
[0010] S1. Prepare a standard stock solution of polystyrene microplastics using ultrasonic separation; take 0.05 g of polystyrene microplastics, add 1000 mL of water, and alternately stir and sonicate (5 min each time) to prepare 0.05 g L -1 Standard polystyrene suspension;
[0011] S2. The fluorescence intensity of the standard suspension was determined using a three-dimensional fluorescence spectrophotometer, and standard curves of fluorescence intensity versus mass concentration of polystyrene microplastics were plotted for different concentration ranges.
[0012] 1) Dilute the standard polystyrene suspension prepared in S1 with ultrapure water to concentrations of 0.01, 0.02, 0.03, 0.04, and 0.05 g / L. -1 The fluorescence intensity of the polystyrene suspension was measured using a fluorescence spectrophotometer at excitation / reception wavelengths of 260 / 310 nm (400 V). The measured fluorescence intensity was plotted against the corresponding mass concentration of polystyrene microplastics to form a standard curve.
[0013] 2) Dilute the standard polystyrene suspension prepared in S1 with ultrapure water to concentrations of 1, 2, 3, 4, and 5 mg / L. -1 The fluorescence intensity of the polystyrene suspension was measured using a fluorescence spectrophotometer at excitation / reception wavelengths of 260 / 310 nm (700 V) or 260 / 610 nm (700 V). The measured fluorescence intensity was plotted against the corresponding polystyrene microplastic mass concentration to form a standard curve.
[0014] S3. Measure the fluorescence intensity of a water sample with an unknown polystyrene microplastic concentration at 260 / 310 nm (low concentration: 700V) or 260 / 310 nm (high concentration: 400V). Substitute this intensity into the standard curve to calculate the concentration of microplastics in the water sample. The calculation method is as shown in formula (1), where C is the concentration of polystyrene microplastics in the water sample, E is the measured fluorescence intensity of the water sample, b is the intercept of the standard curve, and a is the slope of the standard curve.
[0015]
[0016] According to the technical solution of the present invention, the following supplements are made:
[0017] The fluorescence excitation / acceptance wavelengths used in this invention were determined by three-dimensional scanning of a standard suspension using a three-dimensional fluorescence spectrophotometer. The three-dimensional fluorescence spectral scanning range was Ex: 200-600nm, Em: 200-700nm, with a scanning voltage of 700V and a path width of 5nm.
[0018] The average mass concentration segments of the above-mentioned microplastic suspensions are reasonable, and the mass concentration segments cover a wide range, ensuring the accuracy of the fitting curves and tests. This demonstrates the advantages of this invention, which is applicable to a wide range of microplastic suspension mass concentrations and has a low detection threshold.
[0019] The method for quantitative analysis of polystyrene microplastics using benzene ring fluorescence according to embodiments of the present invention has at least the following beneficial effects:
[0020] This invention provides a benzene ring autofluorescence method for quantifying the mass concentration of polystyrene microplastics, and the quantification after environmental aging. This invention utilizes fluorescence spectrophotometry to explore and verify the quantification method for microplastic mass concentration and different aging degrees, and extends it to the quantification of polystyrene microplastics in actual water bodies. This invention fills the gap in microplastic quantification methods that do not require additional reagents. Compared with other methods, this invention has the advantages of being simple, fast, easy to operate, highly accurate, and having a wide detection range.
[0021] According to some embodiments of the present invention, the original polystyrene microplastics have an average particle size of 1.59 μm and a minimum particle size of 420 nm.
[0022] According to some embodiments of the present invention, the particle size range of the aged polystyrene is 250nm-6.34μm (aged for 36h) and 160nm-4.08μm (aged for 84h).
[0023] According to some embodiments of the present invention, the method for quantitatively determining the mass concentration of polystyrene microplastics in water using fluorescence is almost unaffected by salt ions and pH in the water.
[0024] According to some embodiments of the present invention, the method for quantitatively determining the mass concentration of polystyrene microplastics in water using fluorescence still maintains stability and accuracy in the presence of the same concentration of dissolved organic matter. Attached Figure Description
[0025] Figure 1 100mg L -1 Three-dimensional fluorescence spectrum of PS suspension;
[0026] Figure 2Concentration-fluorescence intensity mark for low-concentration PS suspension (0-5 mg / L) -1 );
[0027] Figure 3 Concentration-fluorescence intensity mark for high-concentration PS suspension (0-50 mg / L) -1 );
[0028] Figure 4 1.5mg / L -1 Fluorescence intensity of PS suspension at different CaCl2 and MgCl2 concentrations;
[0029] Figure 5 1.5mg / L -1 Fluorescence intensity of PS suspension at different NaCl and Na2SO4 concentrations;
[0030] Figure 6 1.5mg / L -1 Fluorescence intensity of PS suspension at different concentrations of NaNO3 and humic acid;
[0031] Figure 7 1.5mg / L -1 Fluorescence intensity of PS suspension at different pH values;
[0032] Figure 8 100mg L -1 Three-dimensional fluorescence spectrum of PS suspension aged for 36 hours;
[0033] Figure 9 (a) Scanning electron microscope image and (b) particle size distribution of polystyrene microplastics aged for 36 hours;
[0034] Figure 10 Concentration-fluorescence intensity standard curve of PS suspension aged for 36 hours;
[0035] Figure 11 100mg L -1 Three-dimensional fluorescence spectrum of PS suspension aged for 84 hours;
[0036] Figure 12 (a) Scanning electron microscope image and (b) particle size distribution of polystyrene microplastics aged for 84 hours;
[0037] Figure 13 Concentration-fluorescence intensity standard curve of PS suspension aged for 84 hours. Detailed Implementation
[0038] The present invention is further illustrated below by way of examples. The examples described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.
[0039] Example 1
[0040] In this example, 10 mg L -1 The standard PS suspension A was prepared first for later use. Then, specific volumes of anhydrous calcium chloride and anhydrous magnesium chloride were weighed and prepared to a concentration of 4 mg / L. -1 Stock solutions B and C were prepared. The concentrations of PS were set at 1 and 5 mg / L, respectively. -1 The concentration gradients of CaCl2 and MgCl2 are 0, 0.2, 0.5, 0.8, 1, and 2 mg / L. -1 Suspension A was prepared by mixing it with solutions B and C, respectively. Finally, the fluorescence intensity of each sample at 260 / 310 nm was measured using a three-dimensional fluorescence spectrophotometer. The results are as follows: Figure 4 For 1 and 5 mg L -1 Initial PS concentration, with Ca 2+ and Mg 2+ Ion concentration increased from 0 to 2 mg / L -1 The fluorescence intensity of the suspension hardly changed, indicating the accuracy and practicality of the method for quantitatively analyzing polystyrene microplastics in water using benzene ring fluorescence.
[0041] Example 2
[0042] In this example, 10 mg L -1 The standard PS suspension A was prepared first for later use. Then, specific volumes of anhydrous sodium chloride and anhydrous sodium sulfate were weighed and prepared into 4g L solutions. -1 Stock solutions D and E were prepared. The concentrations of PS were set at 1 and 5 mg / L. -1 The concentration gradients of NaCl and Na₂SO₄ are 0, 0.2, 0.5, 0.8, 1, and 2 g / L. -1 Suspension A was prepared by mixing it with solutions D and E, respectively. The fluorescence intensity of each sample at 260 / 310 nm was measured using a three-dimensional fluorescence spectrophotometer. The results are as follows: Figure 5 For 1 and 5 mg L -1 The initial PS concentration increased as the concentrations of NaCl and Na2SO4 increased from 0 to 2 g / L. -1 The fluorescence intensity of the suspension hardly changed, indicating the accuracy and practicality of the method for quantitatively analyzing polystyrene microplastics in water using benzene ring fluorescence.
[0043] Example 3
[0044] In this example, 10 mg L -1 The standard PS suspension A was prepared first for later use. Then, specific volumes of anhydrous sodium nitrate and fulvic acid (FA) were weighed to prepare 4 mg / L solutions. -1Stock solutions F and G were prepared. The concentrations of PS were set at 1 and 5 mg / L. -1 The concentration gradients of NaNO3 and FA were 0, 0.2, 0.5, 0.8, 1, and 2 mg / L. -1 Suspension A was prepared by mixing it with solutions F and G, respectively. The fluorescence intensity of each sample at 260 / 310 nm was measured using a three-dimensional fluorescence spectrophotometer. The results are as follows: Figure 6 For 1 and 5 mg L -1 The initial PS concentration increased as the NaNO3 concentration increased from 0 to 2 mg / L. -1 The fluorescence intensity of the suspension remained almost unchanged, demonstrating the accuracy and practicality of the method for quantitatively analyzing polystyrene microplastics in water using benzene ring fluorescence. Furthermore, at the same FA concentration, the fluorescence intensity of the suspension was only affected by the PS concentration, further proving the practicality of this invention.
[0045] Example 4
[0046] In this example, 10 mg L -1 Standard PS suspension A was prepared first for later use. Next, 0.1M NaOH and HCl solutions were prepared to adjust the pH of the suspension. Suspension A was then diluted to PS concentrations of 1 and 5 mg / L, respectively. -1 The pH of the suspension was adjusted to 6-9. The fluorescence intensity of each sample at 260 / 310 nm was measured using a three-dimensional fluorescence spectrophotometer. The results are as follows: Figure 7 For 1 and 5 mg L -1 The initial PS concentration was adjusted, and the pH value was changed from 6 to 9. The fluorescence intensity of the suspension hardly changed, which shows the accuracy and practicality of the method of quantitatively analyzing polystyrene microplastics in water using benzene ring fluorescence.
[0047] Example 5
[0048] The actual water bodies used in this example were tap water, lake water, river water, and sludge supernatant. All water bodies were filtered through a 0.45 μm filter membrane to remove interference from large suspended solids. 10 mg L of the solution was prepared using each of the four water bodies. -1 Standard PS suspensions Z (tap water), H (lake water), J (river water), and W (sludge supernatant) were prepared for use. Then, suspensions Z, H, J, and W were diluted to PS concentrations of 1 and 5 mg / L, respectively. -1 The fluorescence intensity of each sample at 260 / 310 nm was measured using a three-dimensional fluorescence spectrophotometer, and standard curves were plotted. The fitting results are shown in Table 1. In the four water bodies, the correlation between the fluorescence intensity and mass concentration standard curves of polystyrene microplastics all exceeded 0.99, indicating that the fluorescence quantitative method for microplastics described in this invention is also applicable in natural water bodies.
[0049] Table 1. Concentration-fluorescence intensity standard curves of PS suspensions in natural water bodies
[0050]
[0051] Example 6
[0052] The above polystyrene microplastics were aged under a xenon lamp for 36 hours and then prepared into a 100 mg L solution. -1 The standard suspension was subjected to three-dimensional fluorescence spectroscopy using a three-dimensional fluorescence spectrophotometer, and the fluorescence peak was determined to be located at 260 / 310 nm. Scanning electron microscopy and Nano Measurer software determined the particle size range of the aged polystyrene microplastics to be 0.25–6.34 μm.
[0053] PS aged for 36 hours was prepared into 10mg L -1 The suspension was sonicated for 15 minutes to remove air bubbles, and then deionized water was added to prepare concentrations of 0, 1, 2, 3, 4, and 5 mg / L. -1 The standard suspension was analyzed, and the fluorescence intensity was measured at 260 / 310 nm using a three-dimensional fluorescence spectrophotometer to plot a standard curve. The results are as follows: Figure 10 The correlation between the mass concentration and fluorescence intensity standard curve of polystyrene microplastics aged for 36 hours was >0.99, indicating that the fluorescence quantitative method for microplastics described in this invention has a wide range of applications and high accuracy.
[0054] Example 7
[0055] The above polystyrene microplastics were aged under a xenon lamp for 84 hours and then prepared into a 100 mg L solution. -1 The standard suspension was subjected to three-dimensional scanning using a three-dimensional fluorescence spectrophotometer, and the fluorescence peak was determined to be located at 260 / 310 nm. The particle size range of the aged polystyrene microplastics was determined to be 0.16–4.08 μm using scanning electron microscopy and Nano Measurer software.
[0056] Polystyrene microplastics aged for 84 hours were formulated into 10 mg L -1 The suspension was sonicated for 15 minutes to remove air bubbles, and then deionized water was added to prepare concentrations of 0, 1, 2, 3, 4, and 5 mg / L. -1 The standard suspension was analyzed, and the fluorescence intensity was measured at 260 / 310 nm using a three-dimensional fluorescence spectrophotometer to plot a standard curve. The results are as follows: Figure 13 The correlation between the mass concentration and fluorescence intensity curve of aged 36 polystyrene microplastics was 0.999, indicating that the microplastic quantification method of the present invention has a wide range of applications and high accuracy.
[0057] Example Attached Figure
[0058] Figure 4 1.5mg / L -1 PS suspension in different Ca 2+ Mg 2+ fluorescence intensity at concentration Figure 4 1.5mg / L -1 Fluorescence intensity of PS suspension at different NaCl and Na2SO4 concentrations Figure 5 1.5mg / L -1 Fluorescence intensity diagram of PS suspension at different NaNO3 and FA concentrations (S4, 1.5 mg / L) -1 Fluorescence intensity of PS suspension at different pH values Figure 8 100mg L -1 Three-dimensional fluorescence spectrum of PS suspension aged for 36 hours
[0059] Figure 9 (a) Scanning electron microscope image and (b) particle size distribution map of polystyrene microplastics aged for 36 hours. Figure 10 Concentration-fluorescence intensity standard curve of PS suspension aged for 36 hours Figure 11 100mg L -1 Three-dimensional fluorescence spectrum of PS suspension aged for 84 hours
[0060] Figure 12 (a) Scanning electron microscope image and (b) particle size distribution map of polystyrene microplastics aged for 84 hours. Figure 12 Concentration-fluorescence intensity standard curve of PS suspension aged for 84 hours.
Claims
1. A quantitative method for microplastics based on fluorescence intensity measurement, characterized in that, The method includes the following steps: (1) The microplastics used in the method are polystyrene microplastics, and the mass concentration range of the microplastic suspension is 0-50 mg / L. -1 ; (2) Preparation of standard microplastic suspension: Weigh a certain mass of microplastics and prepare a microplastic suspension of a certain mass concentration in an ultrasonic instrument using ultrapure water; (3) Determination of fluorescence intensity of microplastic suspension: The microplastic stock solution was diluted with ultrapure water to the target concentration and its fluorescence intensity was measured by fluorescence spectrophotometer. (4) Plotting the fluorescence intensity-mass concentration standard curve of microplastic suspension: Plot the corresponding fluorescence intensity-mass concentration standard curve of microplastic suspension according to the set high concentration gradient or low concentration gradient. (5) Determination of microplastic mass concentration in water samples: Take water samples with unknown microplastic concentration, measure their fluorescence intensity, and calculate their microplastic mass concentration using a standard curve.
2. The method for quantitative analysis of microplastics based on fluorescence intensity measurement according to claim 1, characterized in that, The wavelength for measuring the fluorescence intensity of microplastics was determined using the three-dimensional fluorescence spectrum of polystyrene microplastics. A three-dimensional fluorescence spectrophotometer was used, with a fluorescence scanning wavelength range of Ex: 200-600 nm and Em: 200-700 nm. When the measurement voltage was 700 V, the concentration range of the microplastics used was 0-5 mg / L. -1 When the measuring voltage is 400V, the concentration range of the microplastics used is 0-50 mg / L. -1 ; When the microplastic used is polystyrene microplastic containing additives, the wavelength for fluorescence measurement is Ex=260nm and Em=310nm.
3. The method for quantitative analysis of microplastics based on fluorescence intensity measurement according to claim 1, characterized in that, The choice between a high-concentration or low-concentration microplastic standard curve depends on the approximate concentration of microplastics in the water sample being measured. The high-concentration range is 0-50 mg / L. -1 The low concentration range is 0-5 mg / L. -1 .
4. The method for quantitative analysis of microplastics based on fluorescence intensity measurement according to claim 1, characterized in that, The method is applied to the quantification of virgin and aged polystyrene microplastics in salt solutions and actual water bodies, including river water, lake water, tap water, and sludge supernatant.