Analysis method for quantitative detection and particle size distribution of polystyrene nano-plastics

Abstract

The invention discloses a quantitative detection and particle size distribution analysis method for polystyrene nano-plastics. The method comprises the following steps: preparing a working sample; a linear model of the concentration and the scattered light intensity of the working sample is obtained under the synchronous spectrum condition that delta lambda is equal to 0 through a fluorescence spectrophotometer, and quantitative detection is achieved; the particle size of the sample is determined by utilizing the similarity between the spectrum after particle size mixing and the spectrum with the same particle size at the same concentration, the concentration percentage of the PS sample with each particle size is obtained by utilizing the additive property of the scattered light intensity after particle size mixing, selecting the scattered light intensity of different wavebands and simultaneous equations, and then the spectrum recovery is realized. The method is simple and convenient, quantitative detection (the detection limit is 4 mu g / L) of the PS nano-plastic and simultaneous determination of different particle size distribution proportions can be achieved at the same time without any pretreatment, good practicability and repeatability are achieved, and reliable detection can be provided for laboratory simulation experiments.

Description

Technical Field

[0001] The invention belongs to the technical field of nano plastic detection and analysis, and specifically relates to a method for quantitative detection of polystyrene nano plastic and analysis of particle size distribution. Background Art

[0002] Nanoplastics are a new type of pollutant that is widely present in the environment and has many adverse effects on humans. However, how to quantify NPs in the environment has become a severe challenge for existing research.

[0003] Among the existing quantitative detection technologies: technologies represented by Py-GC / MS are difficult to achieve in-situ detection and obtain the morphology, particle size and distribution information of NPs; technologies represented by electron microscopy can achieve the morphology and particle size information of NPs with smaller particle sizes, but the concentration quantification achieved by counting has large errors; Raman spectroscopy and infrared spectroscopy are commonly used technical means to detect NPs, but are limited by the optical diffraction limit. The detection of NPs below 200nm is cumbersome and time-consuming, and requires some pre-treatment methods or combination with other methods to achieve detection. Therefore, its quantification is often limited by the detection limit; scattered light technology represented by dynamic light scattering is an important means to characterize the particle size distribution of NPs, but it can often only obtain particle size distribution information and is difficult to achieve quantification. Therefore, there are some imbalances in the existing technologies for detecting NPs. When obtaining the concentration information, particle size and proportion of NPs, different instruments need to be used together to achieve them one by one. Therefore, it is very necessary to develop a method that can simultaneously achieve NPs particle size distribution, particle size proportion and concentration information. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for quantitative detection of polystyrene nanoplastics and analysis of particle size distribution. It is a new method for NPs analysis and detection based on fluorescence spectrometer, which can realize quantitative detection of microspheres in situ and without any pretreatment. It uses simple mathematical analysis methods combined with spectral analysis to realize distribution and proportion detection of PS samples with different particle sizes, thus solving the problems in the above-mentioned background technology.

[0005] The technical solution adopted by the present invention to solve the technical problem is: to provide a method for quantitative detection and particle size distribution analysis of polystyrene nanoplastics, comprising the following steps:

[0006] (1) Preparation of working samples: ultrasonically disperse a standard solution of PS microspheres with known particle size and dilute to obtain working samples with different concentration gradients;

[0007] (2) Quantitative detection: construct a linear model of the scattered light intensity and concentration of working samples with different particle sizes and samples to be tested, detect the scattered light intensity of the samples to be tested by fluorescence spectrometer, and perform quantitative analysis based on the linear model;

[0008] (3) Particle size distribution detection: PS microsphere mixed solutions of different proportions were prepared using the working sample, and the theoretical scattered light intensity of the mixed solutions of different proportions was calculated; the scattered light intensity of the sample to be tested was correlated with the scattered light intensity of the sample to be tested at the same concentration; the particle size distribution in the sample to be tested was obtained by calculating the percentage of PS microsphere concentration within the correlation coefficient range of 0.7-1.0; the theoretical scattered light intensity calculation formula of the mixed particle size ratios of different proportions is as follows:

[0009] W=I 粒径1 ·ω 粒径1 +I 粒径2 ·ω 粒径2 +I 粒径3 ·ω 粒径3 +┈

[0010] Where, W: theoretical scattered light intensity; ω 粒径x : The percentage concentration of particle size X in the mixed solution; I 粒径X : The scattered light intensity of particle size X at the percentage concentration; x represents the serial number; ω 粒径1 +ω 粒径2 +ω 粒径3 +┈=1.

[0011] Preferably, it also includes:

[0012] (4) Additivity verification: The calculated theoretical scattered light intensity is compared with the actual measured scattered light intensity to verify that after mixing particles of different sizes, their scattered light intensities are additivity at the same concentration.

[0013] Preferably, it also includes:

[0014] (5) Spectral restoration: The solution is prepared according to the concentration percentage of PS microspheres with different particle sizes to achieve spectrum restoration.

[0015] Preferably, in step (1), the particle sizes of PS nanoplastics are 25 nm, 50 nm, 200 nm, 300 nm, 500 nm, 600 nm and 1 μm, the solvent is Mlli-Q, and the dilution concentrations are 1×10 -3 g / L,1×10 -4 g / L,1×10 -5 g / L,1×10 - 6 g / L.

[0016] Preferably, in step (2), the fluorescence spectrometer conditions are: synchronous wavelength difference Δλ=0, excitation emission slit is 2nm, scanning interval is 0.1s, scanning voltage is 1V, and collection band is 250nm-700nm.

[0017] Preferably, in step (2), the corresponding relationship between the scattered light intensity at 335 nm and the concentration is selected for quantification, and the quantitative detection limit is 4 μg / L.

[0018] Preferably, in step (3), 2-3 particle size working samples are selected to form a PS microsphere mixture, the mixing ratio is recorded, and correlation analysis is performed on the spectra of the PS microsphere mixture and the single particle size working sample with the same concentration to verify the particle size relationship.

[0019] Preferably, the correlation analysis in step (3) uses the correlation analysis provided in the Origin software. The higher the correlation between the two spectra, the closer the correlation coefficient of the analysis will be to 1 in value. Preferably, in step (3), the deviation is expressed as the ratio of the difference between the measured scattered light intensity and the theoretical scattered light intensity to the theoretical scattered light intensity, with a numerical range of 0.7%-17.2%.

[0020] Preferably, in step (3), the scattered light intensities in different wavelength bands between 250 nm and 430 nm are selected, and the concentration percentages of PS samples of different particle sizes are obtained by simultaneous equations.

[0021] Preferably, in step (3), the scattered light intensity under different emission bands is selected to establish simultaneous equations, and the obtained value is obtained by solving the equations. For example, the Kandel correlation coefficient is used to perform Kandel correlation detection on the spectrum to be measured and the standard sample spectrum. The higher the correlation, the higher the similarity of the two spectra. Then, from the standard sample spectrum with high correlation, the scattered light intensities at 300nm, 335nm and 370nm are selected as A, B and C respectively, and then the equation Ax+By+Cz=intensity of the spectrum to be measured is listed; then three points are selected, and the equation is established again. The values ​​of x, y and z solved are the concentration percentages of PS samples of each particle size.

[0022] Compared with the background technology, this technical solution has the following advantages:

[0023] 1. The method of the present invention does not require any pre-treatment means to detect PS microspheres of various particle sizes, and has the advantage of being rapid in situ;

[0024] 2. The method of the present invention can simultaneously realize the quantitative detection, particle size distribution and proportion analysis of PS microspheres, and the quantitative detection results have obvious advantages over existing detection methods. The accuracy of multimodal particle size analysis results is significantly improved compared with DLS single-modal detection results;

[0025] 3. The present invention can be implemented on a common fluorescence spectrometer, and the instrument used is universal. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Quantitatively detect spectra for different working samples;

[0027] Figure 2 is the standard linear model of concentration and scattered light intensity;

[0028] Figure 3 Quantitatively detect the spectrum of the sample to be tested;

[0029] Figure 4 It is a linear relationship diagram between the concentration of the sample to be tested and the scattered light intensity;

[0030] Figure 5 PS microspheres with different particle sizes are 1×10 -3 Spectrum at g / L concentration;

[0031] Figure 6 It is the correlation heat map between the spectra of single particle size standard and mixed particle size standard;

[0032] Figure 7 The spectra of different particle size ratios and self-developed samples;

[0033] Figure 8 is the DLS characterization result of the sample to be tested;

[0034] Fig. 9 is a transmission electron microscope image of the sample to be tested;

[0035] Fig.10 UV-visible absorption spectrum, where A. Standard samples with different particle sizes, B. Toluene solvent and self-developed samples; DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further explained below with reference to specific examples and drawings.

[0037] Unless otherwise specified, the materials and reagents used in the examples can be obtained from commercial sources. The nanoplastic particle standard is a commercial aqueous solution containing polystyrene microspheres (Zhongke Leiming Technology Co., Ltd., batch number: 20230313), and the specifications of the standard sample include: mass concentration: 50 mg / mL; the particle sizes are: 25 nm, 50 nm, 200 nm, 300 nm, 500 nm, 600 nm, 1 μm, and the particle size deviation is within 20%.

[0038] Fluorescence spectrometer: Japan HORIBA; Model: QuantaMaster 8000

[0039] Nanopotentiometer: Malvern, UK; Model: Zetasizer Nano ZEN

[0040] Transmission electron microscope: Japan Hitachi; model: HT7700

[0041] Example

[0042] The present embodiment provides a method for quantitative detection and particle size distribution analysis of polystyrene nanoplastics, comprising the following steps:

[0043] (1) Preparation of working sample:

[0044] Use a 20μL pipette to take 20μL of the purchased standard 500nm PS microsphere standard and drop it into a colorimetric tube containing 9.9mL Milli-Q to dilute it 500 times. Then use a 1mL pipette to dilute it step by step into a 9.0mL colorimetric tube to obtain working sample concentrations of: 1×10 -3 g / L,1×10 -4 g / L,1×10 -5 g / L,1×10 -6 g / L; ultrasonically disperse at 40kW power for 30 minutes to make it evenly dispersed in the solution.

[0045] (2) Quantitative detection:

[0046] ① Place the above working sample in the sample pool of the fluorescence spectrometer through a cuvette, and adjust the instrument parameters, including the following parameters: in the synchronous spectrum detection mode, set the synchronous wavelength difference Δλ = 0; the scanning interval is 0.1s, the scanning voltage is 1V, the excitation and emission slits are both set to 2nm, and the collection band is 250nm-700nm. Scan its spectrum from low concentration to high concentration in turn ( Figure 1 ), the scattered light intensity at 400nm was taken to calculate the linear relationship between concentration and scattered light intensity, thus obtaining a linear interval of 1.0×10 -5 g / L-1.0×10 -3 g / L, a linear model (standard curve) was constructed with concentration as the horizontal axis and scattered light intensity as the vertical axis: y = 14273.2x + 1143669, with a correlation coefficient of R 2 =0.9576, the detection limit is 2.1×10 -6 g / L, specific results such as Figure 2 shown.

[0047] ② Use the self-ground PS powder as the sample to be tested:

[0048] Weigh 0.2500g of self-ground PS powder in 20ml toluene, add 50ml Milli-Q after dissolving completely, and ultrasonicate until all toluene evaporates to obtain self-ground PS-Milli-Q solution with a concentration of 5mg / mL; use a 200μL pipette to take 200μL of the purchased standard 500nm PS microsphere standard and drop it into a colorimetric tube containing 9.8mL Milli-Q to dilute it 50 times. Then use a 1mL pipette to dilute it step by step into a 9.0mL colorimetric tube to obtain sample concentrations of: 1×10-3 g / L,1×10 -4 g / L,1×10 -5 g / L,1×10 -6 g / L; ultrasonically disperse at 40kW power for 30 minutes to make it evenly dispersed in the solution.

[0049] The sample to be tested is placed in the sample pool of the fluorescence spectrometer through a cuvette, and the instrument parameters are adjusted, including the following parameters: in the synchronous spectrum detection mode, the synchronous wavelength difference Δλ is set to 0; the scanning interval is 0.1s, the scanning voltage is 1V, the excitation and emission slits are both set to 2nm, and the collection band is 250nm-700nm. Scan the spectrum from low concentration to high concentration in turn ( Figure 3 ), the scattered light intensity at 400nm was taken to calculate the linear relationship between concentration and scattered light intensity, thus obtaining a linear interval of 1.0×10 -5 g / L-1.0×10 -3 g / L, linear relationship curve: y=8779.3x+907352, correlation coefficient R 2 =0.9379, the detection limit is 3.4×10 -6 g / L, specific results such as Figure 4 This shows that PS samples with uneven particle size distribution can still be quantitatively detected through the linear relationship between concentration and scattered light intensity.

[0050] (3) Particle size distribution detection:

[0051] ①Use a 20μL pipette to take 20μL of the purchased standard 25nm, 50nm, 200nm, 300nm, 500nm, 600nm, and 1μm PS microsphere standards and drop them into seven colorimetric tubes filled with 9.9mL Milli-Q to dilute them 500 times. Then use a 1mL pipette to dilute them step by step into 9.0mL colorimetric tubes to obtain a uniform working solution concentration of 1.0×10 -3 g / L.

[0052] The above-mentioned sample to be tested is placed in the sample pool of the fluorescence spectrometer through a cuvette, and the instrument parameters are adjusted, including the following parameters: in the synchronous spectrum detection mode, the synchronous wavelength difference Δλ is set to 0; the scanning interval is 0.1s, the scanning voltage is 1V, the excitation and emission slits are both set to 2nm, and the collection band is 250nm-700nm. Scan the synchronous spectra of PS microspheres with different particle sizes. The spectra of PS microspheres with different particle sizes are shown in Figure 1. Figure 5 .

[0053] ② Calculate the theoretical scattered light intensity of the mixture of different particle sizes in step (3)-① respectively. The scattered light intensity calculation formula is as follows: W = I 粒径1 ·ω 粒径1 +I粒径2 ·ω 粒径2 +I 粒径3 ·ω 粒径3 +┈

[0054] Where W: theoretical scattered light intensity; ω 粒径x : The percentage concentration of particle size X in the mixed solution; I 粒径X : The scattered light intensity of particle size X at the percentage concentration; x represents the serial number; ω 粒径1 +ω 粒径2 +ω 粒径3 +┈=1.

[0055] ③Use Origin software to perform correlation analysis on the entire segment. Considering that the difference in the spectrum is mainly reflected between 250nm-430nm, the correlation analysis of the spectrum between 250nm-430nm is performed, and the correlation difference of different particle sizes is further increased; at the same concentration, the higher the proportion of PS microspheres in the mixed system, the higher the correlation between the mixed spectrum and its single particle size. The results are as follows Figure 6 The higher the correlation between the two spectra, the closer the correlation coefficient of the analysis will be to 1. The particle size distribution in the self-ground sample is determined based on the correlation. The particle size distribution in the sample to be tested is obtained by calculating the concentration percentage of several PS microspheres within the correlation coefficient range of 0.7-1.0.

[0056] Among them, by selecting the scattered light intensity under different emission bands to combine equations, the concentration percentage can be obtained by solving the equations:

[0057] Ax+By+Cz+Ds+……=measured spectral intensity

[0058] 267332.9976x+1598285.003y+1809610.003z=900177.394——Equation ①

[0059] 334863.325x+1859696.377y+2111455.75z=1099253.565——Equation ②

[0060] 290976.6626x+2045227.75333333y+2165785.5z=1000818.2815——Equation ③

[0061] By selecting the simultaneous equations of the scattering intensity of three PS standard samples with particle sizes of 25nm, 200nm and 500nm at 300nm, 335nm and 370nm, the specific values ​​of x / y / z corresponding to the proportion of their particle sizes are solved.

[0062] Furthermore, this embodiment also performs correlation verification: after mixing standards of different particle sizes in a known proportion, a spectrum of the mixed standard is obtained, and a Kandel correlation analysis is performed on the spectrum of the obtained mixed standard and the spectrum of the standard of a single particle size. The coefficient is used to indicate that the concentration of a certain particle size in the mixed standard accounts for a higher proportion, that is, the higher the similarity, the higher the concentration of the particle size standard. This is used to verify that the particle size relationship can be explained by correlation.

[0063] (4) Additivity verification:

[0064] The ratio of the scattered light intensity obtained at 270nm, 300nm, 335nm, 370nm, and 400nm of the spectrum obtained in step (3) to the calculated theoretical scattered light intensity, the ratio of the two represents the deviation, and the results are shown in Table 1. The results show that after the particle size is mixed, the scattered light intensity of the mixed system is additive.

[0065] Table 1

[0066]

[0067]

[0068] (5) Spectral restoration:

[0069] The self-developed PS-MilliQ sample was characterized by DLS and transmission electron microscopy. The DLS characterization results showed that the average particle size of the self-developed PS-MilliQ sample was 270nm. Figure 8 ; Transmission electron microscopy characterization results show that the particle size of the self-developed PS-MilliQ sample is mainly distributed between 200-300nm, and the 50nm particle size PS sample is also quite impressive. Fig. 9 The restoration results further verified the accuracy and reliability of this method.

[0070] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for quantitative detection and particle size distribution analysis of polystyrene nanoplastics, characterized in that: The steps include: (1) Preparation of working samples: ultrasonically disperse a standard solution of PS microspheres with known particle size and dilute to obtain working samples with different concentration gradients; (2) Quantitative detection: construct a linear model of the scattered light intensity and concentration of the working sample and the sample to be tested, detect the scattered light intensity of the sample to be tested by fluorescence spectrometer, and perform quantitative analysis according to the linear model; (3) Particle size distribution detection: PS microsphere mixed solutions of different proportions were prepared using the working sample, and the theoretical scattered light intensity of the mixed solutions of different proportions was calculated; the scattered light intensity of the sample to be tested was correlated with the scattered light intensity of the sample to be tested at the same concentration; the particle size distribution in the sample to be tested was obtained by calculating the percentage of PS microsphere concentration within the correlation coefficient range of 0.7-1.0; The theoretical scattered light intensity calculation formula for different mixed particle size ratios is as follows: W=I 粒径1 ·oh 粒径1 +I 粒径2 ·oh 粒径2 +I 粒径3 ·oh 粒径3 +┈ Where, W: theoretical scattered light intensity; ω 粒径x : The percentage concentration of particle size X in the mixed solution; I 粒径X : The scattered light intensity of particle size X at the percentage concentration; x represents the serial number; ω 粒径1 +ω 粒径2 +ω 粒径3 +┈=1.

2. The method for quantitative detection and particle size distribution analysis of polystyrene nanoplastics according to claim 1, characterized in that: Also includes: (4) Additivity verification: The calculated theoretical scattered light intensity is compared with the actual measured scattered light intensity to verify that after mixing particles of different sizes, their scattered light intensities are additivity at the same concentration.

3. The method for quantitative detection and particle size distribution analysis of polystyrene nanoplastics according to claim 1, characterized in that: Also includes: (5) Spectral restoration: The solution is prepared according to the concentration percentage of PS microspheres with different particle sizes to achieve spectrum restoration.

4. The method for quantitative detection and particle size distribution analysis of polystyrene nanoplastics according to claim 1, characterized in that: In step (1), the particle sizes of PS nanoplastics are 25 nm, 50 nm, 200 nm, 300 nm, 500 nm, 600 nm and 1 μm, the solvent is Mlli-Q, and the dilution concentrations are 1×10 -3 g / L,1×10 -4 g / L, 1×10 -5 g / L, 1×10 -6 g / L.

5. The method for quantitative detection and particle size distribution analysis of polystyrene nanoplastics according to claim 1, characterized in that: In step (2), the fluorescence spectrometer conditions are: synchronous wavelength difference Δλ=0, excitation emission slit is 2nm, scanning interval is 0.1s, scanning voltage is 1V, and collection band is 250nm-700nm.

6. The method for quantitative detection and particle size distribution analysis of polystyrene nanoplastics according to claim 1, characterized in that: In step (2), the corresponding relationship between the scattered light intensity and the concentration at 335 nm was selected for quantification, and the quantitative detection limit was 4 μg / L.

7. The method for quantitative detection and particle size distribution analysis of polystyrene nanoplastics according to claim 1, characterized in that: In step (3), 2-3 kinds of working samples with different particle sizes are selected to form a PS microsphere mixture, the mixing ratio is recorded, and correlation analysis is performed on the spectra of the PS microsphere mixture and the working samples with a single particle size with the same concentration.

8. The method for quantitative detection and particle size distribution analysis of polystyrene nanoplastics according to claim 1, characterized in that: In step (3), the deviation is represented by the difference between the measured scattered light intensity and the theoretical scattered light intensity and the ratio of the theoretical scattered light intensity, with a numerical range of 0.7%-17.2%.

9. The method for quantitative detection and particle size distribution analysis of polystyrene nanoplastics according to claim 1, characterized in that: In step (3), the scattered light intensity in different wavelength bands between 250 nm and 430 nm is selected, and the concentration percentage of PS samples of different particle sizes is obtained by simultaneous equations.

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