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

Abstract

The application discloses a kind of polystyrene nano plastic quantitative detection and particle size distribution analysis method, comprising the following steps: preparation work sample;Through fluorescence spectrometer, the concentration and scattering light intensity linear model of work sample is obtained under the condition of synchronous spectrum Δλ=0, quantitative detection is realized;The similarity of the spectrum after particle size mixing and the spectrum of single particle size under the same concentration is used to determine the particle size in sample, the scattering light intensity after particle size mixing has additivity, the scattering light intensity of different wave bands is selected, and the concentration percentage of each particle size PS sample is obtained by simultaneous equations, and then the spectrum is restored.This method is simple and convenient, without any pretreatment, can realize the quantitative detection (detection limit 4 μg / L) and simultaneous determination of different particle size distribution ratio of PS nano plastic at the same time, has good practicability and repeatability, can provide reliable detection for laboratory simulation experiment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nano plastic detection and analysis, and particularly relates to a polystyrene nano plastic quantitative detection and particle size distribution analysis method. BACKGROUND

[0002] Nano plastics are a kind of new pollutants widely existing in the environment, which can have many adverse effects on human beings. However, how to quantify NPs in the environment has become a severe challenge for existing research.

[0003] In existing quantitative detection technologies, the technology represented by Py-GC / MS is difficult to realize in-situ detection and obtain the morphology, particle size and distribution information of NPs; the technology represented by electron microscopy can realize the morphology and particle size information of smaller NPs, but the concentration quantification realized by counting has a large error; Raman spectroscopy and infrared spectroscopy are common technical means for detecting NPs, but are limited by the optical diffraction limit, and it is time-consuming to detect NPs below 200 nm, which needs to rely on some pretreatment means or be combined with other methods to realize detection, so the quantification is often limited by the detection limit; the scattering light technology represented by dynamic light scattering is an important means for characterizing the particle size distribution of NPs, but it can only obtain the particle size distribution information and is difficult to realize quantification, so the existing technologies for detecting NPs have some imbalances, and different instruments need to be used to realize the concentration information, particle size and proportion of NPs one by one, so it is necessary to develop a method that can realize the particle size distribution, particle size proportion and concentration information of NPs at the same time. SUMMARY

[0004] The application aims to overcome the deficiencies of the prior art and provides a polystyrene nano plastic quantitative detection and particle size distribution analysis method, which is a new NPs analysis and detection method based on a fluorescence spectrometer, can realize quantitative detection of microspheres in-situ without any pretreatment, realizes the distribution and proportion detection of PS samples with different particle sizes by means of simple mathematical analysis method combined with spectral analysis, and solves the problems in the above background.

[0005] The application adopts the technical scheme that a polystyrene nano plastic quantitative detection and particle size distribution analysis method is provided, which comprises the following steps:

[0006] (1) Preparing a working sample: ultrasonic dispersion is performed on a PS microsphere standard sample solution with a known particle size, and different concentration gradients of the working sample are obtained by dilution;

[0007] (2) Quantitative detection: a linear model of the scattering light intensity and the concentration of the working sample and the sample to be detected with different particle sizes is constructed, the scattering light intensity of the sample to be detected is detected by the fluorescence spectrometer, and quantitative analysis is performed according to the linear model.

[0008] (3) Particle size distribution detection: different proportions of PS microsphere mixed solutions are prepared using the working sample, the theoretical scattering light intensity of different proportion mixed solutions is calculated, the scattering light intensity of the sample to be tested is analyzed in correlation under the same concentration, the particle size distribution in the sample to be tested is obtained by calculating the correlation coefficient 0.7-1.0 range of PS microsphere concentration percentage; the theoretical scattering light intensity calculation formula of different mixed particle size 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] Wherein, W: theoretical scattering light intensity; ω 粒径x : particle size X in the mixed solution percentage concentration; I 粒径X : scattering light intensity of particle size X under the percentage concentration; x represents the serial number; ω 粒径1 + ω 粒径2 + ω 粒径3 +┈ = 1.

[0011] Preferably, it further comprises:

[0012] (4) Additivity verification: compare the calculated theoretical scattering light intensity with the actual measured scattering light intensity, verify the scattering light intensity of different particle size mixture under the same concentration, and verify the scattering light intensity of different particle size mixture under the same concentration.

[0013] Preferably, it further comprises:

[0014] (5) Spectrum recovery: according to the concentration percentage of different particle size PS microspheres, the solution is prepared to realize the recovery of the spectrum.

[0015] Preferably, in step (1), the PS nano plastic particle size is selected as 25nm, 50nm, 200nm, 300nm, 500nm, 600nm and 1μm, the solvent is MIlli-Q, and the dilution concentration is 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 wave band is 250nm-700nm.

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

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

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

[0020] Preferably, in step (3), the scattering light intensity of different wave bands between 250 nm and 430 nm is selected to solve the equations to obtain the concentration percentage of each particle size PS sample.

[0021] Preferably, in step (3), the scattering light intensity of different wave bands is selected to solve the equations, and the equations are solved to obtain. For example, the candela correlation coefficient is used to detect the candela correlation between the to-be-detected spectrum and the standard sample spectrum, and the higher the correlation, the higher the degree of similarity between the two spectra. Then, the scattering light intensities at 300 nm, 335 nm and 370 nm of the standard sample spectrum with high correlation are selected as A, B and C, and then the equation Ax+By+Cz=the intensity of the to-be-detected spectrum is listed. Then, three points are selected, and an equation is established, and the numerical values of x, y and z obtained by solving the equation are the concentration percentages of each particle size PS sample.

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

[0023] 1. The method of the present application does not require any pretreatment means for detecting various particle size PS microspheres, and has the advantages of in-situ rapidity;

[0024] 2. The method of the present application can simultaneously realize quantitative detection, particle size distribution and proportion analysis of PS microspheres, and the quantitative detection result has obvious advantages compared with existing detection means, and the accuracy of multi-modal particle size analysis result is obviously improved compared with the single-modal detection result of DLS;

[0025] 3. The present application can be operated on a common fluorescence spectrometer, and the instrument used has universality. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The quantitative detection spectrum of different working samples;

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

[0028] Figure 3 For the quantitative detection spectrum of the sample to be measured;

[0029] Figure 4 For the linear relationship diagram of the concentration of the sample to be measured and the scattered light intensity;

[0030] Figure 5 For the spectrum of the PS microsphere standard sample with different particle sizes at a concentration of 1x10 -3 g / L;

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

[0032] Figure 7 For the spectrum of the self-researched sample with different particle size proportions;

[0033] Figure 8 For the DLS characterization result of the sample to be measured;

[0034] Figure 9 For the transmission electron microscope image of the sample to be measured;

[0035] Figure 10 For the ultraviolet-visible absorption spectrum, A. Standard sample with different particle sizes, B. Toluene solvent and self-researched sample; DETAILED DESCRIPTION

[0036] The technical solutions of the present application will be further explained and described below in combination with specific examples and drawings.

[0037] The materials, reagents, etc. used in the examples, if not specifically stated, can be obtained from commercial channels. Among them, the nano plastic particle standard sample is a commercial water solution containing polystyrene microspheres (Zhongke Leiming Technology Co., Ltd., batch number: 20230313), and the standard sample specifications include: mass concentration: 50 mg / mL; and the particle sizes are 25 nm, 50 nm, 200 nm, 300 nm, 500 nm, 600 nm, and 1 μm, respectively, with a particle size deviation within 20%.

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

[0039] Nano potentiometer: UK Malvern; model: Zetasizer Nano ZEN

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

[0041] EXAMPLE

[0042] This 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 microspheres and drop them into a 9.9mL Milli-Q colorimetric tube 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 a power of 40 kW for 30 min to make it evenly dispersed in the solution.

[0045] (2) Quantitative detection:

[0046] ① Place the above working sample in the sample cell 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 sequence ( Figure 1 ), the Mie scattered light intensity at 400 nm was used to calculate the linear relationship between concentration and scattered light intensity, and the linear interval was 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 R 2 =0.9576, the detection limit is 2.1×10 -6 g / L, specific results such as Figure 2 shown.

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

[0048] Weigh 0.2500g of self-ground PS powder in 20ml of toluene. After complete dissolution, add 50ml of Milli-Q and sonicate until all the toluene evaporates to obtain a self-ground PS-Milli-Q solution with a concentration of 5mg / mL. Use a 200μL pipette to take 200μL of a purchased standard 500nm PS microsphere standard and drop it into a colorimetric tube containing 9.8mL of Milli-Q to dilute it 50 times. Then use a 1mL pipette to dilute it stepwise into a 9.0mL colorimetric tube to obtain sample concentrations of: 1×10-3 g / L, 1 x 10 -4 g / L, 1 x 10 -5 g / L, 1 x 10 -6 g / L; ultrasonic dispersion for 30 min at 40 kW power to make them evenly dispersed in solution.

[0049] The above sample to be tested was placed in the sample cell of the fluorescence spectrometer through a cuvette, and the instrument parameters were adjusted, specifically including the following parameters: in the synchronous spectrum detection mode, the synchronous wavelength difference Δλ = 0 was set; the scanning interval was 0.1 s, the scanning voltage was 1 V, the excitation and emission slits were both set to 2 nm, and the collection wave band was 250 nm-700 nm. The spectrum was scanned from low concentration to high concentration (see Figure 3 ), and the linear relationship between the concentration and the scattering light intensity was calculated by taking the scattering light intensity at 400 nm, so as to obtain the linear interval of 1.0 x 10 -5 g / L-1.0 x 10 -3 g / L, and the linear relationship curve was y = 8779.3x + 907352, the correlation coefficient R 2 = 0.9379, and the detection limit was 3.4 x 10 -6 g / L, and the specific results are shown in Figure 4 . It is shown that the PS sample with uneven particle size distribution can still be quantitatively detected by the linear relationship between the concentration and the scattering light intensity.

[0050] (3) Particle size distribution detection:

[0051] ① 20 μL of a 20 μL pipette was used to drop 20 μL of the purchased standard 25 nm, 50 nm, 200 nm, 300 nm, 500 nm, 600 nm, and 1 μm PS microsphere standard sample into seven cuvettes containing 9.9 mL of Milli-Q, so as to dilute them by 500 times. Then, 1 mL of a pipette was used to dilute them step by step into 9.0 mL cuvettes, so as to obtain a uniform working solution concentration of 1.0 x 10 -3 g / L.

[0052] The above sample to be tested was placed in the sample cell of the fluorescence spectrometer through a cuvette, and the instrument parameters were adjusted, specifically including the following parameters: in the synchronous spectrum detection mode, the synchronous wavelength difference Δλ = 0 was set; the scanning interval was 0.1 s, the scanning voltage was 1 V, the excitation and emission slits were both set to 2 nm, and the collection wave band was 250 nm-700 nm. The synchronous spectrum of the different particle size PS microsphere standard sample was scanned, and the spectrum of the different particle size PS microsphere is shown in Figure 5 .

[0053] ② The theoretical scattering light intensity of the different particle size mixture in step (3)-① was calculated, and the scattering light intensity calculation formula was 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 : Scattered light intensity of particle size X at a certain percentage concentration; x represents the serial number; ω 粒径1 +ω 粒径2 +ω 粒径3 +┈=1.

[0055] ③ Using Origin software, we conducted a correlation analysis on the entire segment. Since the difference in the spectrum mainly occurs between 250nm and 430nm, we conducted a correlation analysis on the spectrum between 250nm and 430nm. The correlation difference between different particle sizes was further increased. At the same concentration, the higher the concentration 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. By calculating the concentration percentage of several PS microspheres with a correlation coefficient range of 0.7-1.0, the particle size distribution in the sample to be tested is obtained.

[0056] Among them, by selecting the scattered light intensity under different emission bands to set up simultaneous 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 intensities 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] Further, the embodiment also carries out correlation verification: the standard samples of different particle sizes are mixed according to a known proportion to obtain the spectrum of the mixed standard sample, the spectrum of the mixed standard sample is subjected to Candel correlation analysis with the spectrum of the single particle size standard sample, and the concentration of the particle size in the mixed standard sample is high according to the coefficient, that is, the higher the similarity, the higher the concentration of the particle size standard sample, which is used to verify that the particle size relationship can be explained by correlation.

[0063] (4) Additivity verification:

[0064] The ratio of the scattering light intensity obtained from the spectrum obtained in step (3) at 270 nm, 300 nm, 300 nm, 370 nm, 400 nm to the theoretically calculated scattering light intensity is obtained, and the ratio of the two represents the deviation, and the results are as shown in Table 1. The results show that after mixing the particle sizes, the scattering light intensity of the mixed system has additivity.

[0065] Table 1

[0066]

[0067]

[0068] (5) Spectrum recovery:

[0069] The self-prepared PS-MilliQ sample was characterized by DLS and transmission electron microscopy. The DLS characterization results show that the average particle size of the self-prepared PS-MilliQ sample is 270 nm, and the results are as shown in Figure 8 ; the transmission electron microscopy characterization results show that the particle size of the self-prepared PS-MilliQ sample is mainly distributed between 200-300 nm, and the 50 nm particle size PS sample is also considerable, and the results are as shown in Figure 9 . The recovery results further verify the accuracy and reliability of the method.

[0070] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for quantitative detection and particle size distribution analysis of polystyrene nanoplastics, characterized by: The steps include: (1) Preparation of working samples: ultrasonically disperse a standard solution of PS microspheres of 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 based on the linear model; (3) Particle size distribution detection: PS microsphere mixtures of different proportions were prepared using the working sample, and the theoretical scattered light intensity of the mixtures of different proportions was calculated; the scattered light intensity of the mixtures was correlated with the scattered light intensity of the sample to be tested at the same concentration; the particle size distribution of 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 calculation formula for the theoretical scattered light intensity of 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 : Scattered light intensity of particle size X at a certain 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 spectrum is restored by preparing a solution based on the concentration percentage of PS microspheres of different particle sizes.

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 selected as 25 nm, 50 nm, 200 nm, 300 nm, 500 nm, 600 nm and 1 μm, the solvent is MILLI-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 as follows: 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 relationship between the scattered light intensity at 335 nm and the concentration 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 working samples of 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 single particle size working sample of 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 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% to 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 of different wavelengths 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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