High-efficiency enrichment and detection method of microplastics based on thermophoresis enrichment technology

Abstract

The application discloses a high-efficiency enrichment and detection method for microplastics based on thermal migration enrichment technology, a laser light source is used to irradiate a microplastic solution to be detected with heat-generating light, and at least part of the solution generates a temperature difference relative to other positions, at least two temperature step changes exist in the solution, and microplastic particles in the solution move and are enriched along the temperature change; the distribution of the microplastics in the enrichment area is observed through a bright field microscope, and the positions of the enriched microplastic particles are determined; the enriched microplastics are detected through Raman spectrum detection, specific Raman peak signals of the microplastics are obtained, and the number of the microplastics is correspondingly converted. The application combines Raman spectrum technology to qualitatively detect the microplastics enriched through thermal migration, is convenient to operate, does not need to mark the microplastics, overcomes the technical bottleneck that it is difficult to detect low-concentration microplastics, and can be applied to rapid and sensitive detection and analysis of microplastics.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microplastic treatment, in particular to a high-efficiency enrichment and detection method for microplastics based on thermophoresis enrichment technology. BACKGROUND

[0002] Plastic materials are widely used in the world because of their good plasticity, low cost and corrosion resistance. When plastic products are discarded into the natural environment for decomposition, they will be oxidized by light, mechanically abraded by sand and water waves, and biodegraded by organisms, forming small plastic fragments or even micron-sized plastics.

[0003] Microplastics refer to plastic particles with a diameter of less than 5mm. Microplastics are easily ingested by marine organisms and deposited in the body. In addition, due to the large specific surface area of microplastics, they can easily adsorb and aggregate organic pollutants and heavy metal ions in water, which further increases the toxicity of microplastics to organisms.

[0004] Currently, microplastic analysis requires separation of microplastics in the sample before detection. The detection methods mainly include pyrolysis-gas chromatography / mass spectrometry, Fourier transform infrared spectroscopy and Raman spectroscopy. However, pyrolysis-gas chromatography / mass spectrometry has high detection cost, complex operation and long time consumption, and Fourier transform infrared spectroscopy is not suitable for microplastic detection below 10um. Compared with Fourier transform infrared spectroscopy, Raman spectroscopy can detect microplastics as small as 1um. However, when the concentration of microplastics is low, the traditional Raman spectroscopy cannot be used for low-concentration microplastic detection due to weak Raman signals. Therefore, it is necessary to improve the existing detection method to improve the detection efficiency and accuracy. SUMMARY

[0005] The main purpose of the present application is to provide a high-efficiency enrichment and detection method for microplastics based on thermophoresis enrichment technology, which aims to enrich microplastic particles in the microplastic solution to facilitate accurate detection of microplastic content.

[0006] To achieve the above purpose, the present application provides a high-efficiency enrichment and detection method for microplastics based on thermophoresis enrichment technology, comprising the following steps:

[0007] Step S1: using a laser light source to irradiate the microplastic solution to be detected with heat-generating light, and causing at least part of the solution to have a temperature difference from other positions, with at least two temperature steps in the solution, and the microplastic particles in the solution moving and enriching along the temperature change, the laser light source not producing a focal point in the solution and not producing bubbles, and the microplastic particles not being in a molten state at the enrichment position;

[0008] Step S2: observing the distribution of microplastics in the enrichment area by using a bright field microscope, and determining the position of the enriched microplastic particles;

[0009] Step S3: detecting the enriched microplastics by using a Raman spectrum detection, and obtaining specific Raman peak signals of the microplastics.

[0010] Preferably, the laser wavelength of the laser light source is 532 nm, and the laser irradiation time is 10-20 minutes.

[0011] Preferably, the microplastic solution is contained in a container, the base inside the container is a gold-coated cover glass, the thickness of the gold layer on the surface of the gold-coated cover glass is 30-100 nm, the container is a PDMS tank, and the internal length x width x height of the container is 10 mm x 10 mm x 0.1 mm.

[0012] Preferably, the magnification of the bright field microscope is 40 times.

[0013] Preferably, the peak position of the Raman peak signal related to the microplastics is located at a position of 200-2000 cm-1, which is used as a basis for judging whether the microplastics exist or not.

[0014] Preferably, the specific Raman peak signal is a Raman spectrum peak intensity.

[0015] Preferably, the base of the container containing the microplastic solution is provided with a center electromagnet arranged in the center and a peripheral electromagnet arranged in the periphery, a plurality of heating light sources are arranged in the center electromagnet, and the plurality of heating light sources can form a concentric temperature gradient change in the solution.

[0016] Preferably, the microplastic solution is added with modified ferroferric oxide, the microplastic particles in the solution are combined with the ferroferric oxide particles to form suspended particulate matters, the center electromagnet is powered on to adsorb and concentrate the suspended particulate matters, and then the power is turned off to make the center electromagnet lose magnetism;

[0017] The plurality of heating light sources form temperature walls in the solution in a parallel light manner by being controlled respectively, the peripheral electromagnet is powered on to form a peripheral magnetic field on the base, the microplastic particles are separated from the ferroferric oxide particles due to heating, the microplastic particles are concentrated to the center of the base, the moving speed of the microplastic particles is accelerated after passing through the interface between adjacent temperature walls, and the ferroferric oxide particles are concentrated to the peripheral electromagnet.

[0018] Preferably, the temperature of the plurality of heating light sources gradually decreases from the center to the periphery.

[0019] The technical scheme of the present application has the following advantages over the prior art:

[0020] The technical scheme of the present application can enhance the local concentration of microplastics in the solution, and the Raman detection signal of the microplastics can be significantly improved by combining the Raman spectrum technology with the microplastics enriched by the present application.

[0021] In addition, the microplastics can be enriched by laser irradiation of the solution, and the enriched microplastics can be detected and analyzed by Raman spectrum technology, which is more convenient than the prior art and does not require labeling of the microplastics, and the microplastics detection period can be shortened. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0023] Figure 1 The working principle diagram of the high-efficiency enrichment and detection method of microplastics based on the thermal enrichment technology of the present application;

[0024] Figure 2 The optical microscope image of the microplastics in the solution after enrichment by the thermal enrichment technology of the present application;

[0025] Figure 3 The Raman spectrum diagram obtained by Raman spectrum detection of the different number of microplastics enriched after the microplastics in the solution are enriched by the thermal enrichment technology of the present application;

[0026] Figure 4 The signal diagram obtained by detection using Raman spectrum technology after the low-concentration microplastics are enriched by the thermal enrichment technology of the present application;

[0027] Figure 5 The working principle diagram of another high-efficiency enrichment and detection method of microplastics based on the thermal enrichment technology of the present application.

[0028] Explanation of the reference signs:

[0029] 1, container; 11, base; 2, central electromagnet; 3, peripheral electromagnet; 4, heating light source; 5, ferrite particles; 6, interface; 7, microplastic particles.

[0030] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the drawings. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0032] Please refer to Figures 1 to 4 The present application provides a method for efficient enrichment and detection of microplastics based on thermal enrichment technology. First, a laser light source is used to irradiate the microplastic solution to be detected with light that can generate heat, and at least part of the solution has a temperature difference from other positions. There are at least two temperature steps in the solution, and the microplastic particles in the solution move and enrich along the temperature change. The laser light source does not generate a focal point in the solution and does not generate bubbles, and the microplastic particles do not melt at the enrichment position. Then, the distribution of microplastics in the enrichment area is observed by bright field microscopy, and the position of the enriched microplastic particles is determined. Finally, the enriched microplastics are detected by Raman spectrum detection to obtain specific Raman peak signals of the microplastics.

[0033] Preferably, the wavelength of the laser light source is 532 nm, and the laser irradiation time is 10-20 minutes.

[0034] Preferably, the microplastic solution is contained in a container, the base inside the container is a gold-coated cover glass, the surface of the gold-coated cover glass is coated with a gold layer with a thickness of 30-100 nm, and the container is a PDMS tank with a size of 10mm x 10mm x 0.1mm.

[0035] Preferably, the magnification of the bright field microscope is 40 times.

[0036] Preferably, the peak position of the Raman peak signal related to the microplastics is located at 200-2000cm -1 Position as a basis for determining whether microplastics exist.

[0037] Preferably, the specific Raman peak signal is the Raman spectrum peak intensity.

[0038] Example 1:

[0039] Step 1: In the sample cell, 3μm 25.00μg / mL polystyrene is added to the secondary water. The sample cell base is a gold-coated cover glass with a gold-coated surface thickness of 30-100nm, and the sample cell used is a PDMS tank with a size of 10mm x 10mm x 0.1mm.

[0040] Step 2, irradiate the solution in the sample cell with a 532 nm laser for 10-20 minutes, and use an optical microscope to image the enriched microplastics, with a bright field objective magnification of 40 times.

[0041] Example 2:

[0042] Step 1, in the sample cell, 3 μm 25.00 μg / mL polystyrene is added to the secondary water, the sample cell base used is a gold-coated cover glass with a gold coating thickness of 30-100 nm, and the sample cell used is a PDMS tank with a size of 10 mm x 10 mm x 0.1 mm;

[0043] Step 2, irradiate the solution in the sample cell with a 532 nm laser for 10-20 minutes, and use an optical microscope to image the enriched microplastics, with a bright field objective magnification of 40 times.

[0044] Step 3, turn on the laser, select a 785 nm laser, and collect the Raman signal of the enriched microplastics in step 2;

[0045] Step 4, data process the Raman peak signal in the collected Raman spectrum to obtain the Raman spectrum of the microplastics.

[0046] Example 3:

[0047] Step 1, in the sample cell, different numbers of 3 μm polystyrene are added to the secondary water, the sample cell base used is a gold-coated cover glass with a gold coating thickness of 30-100 nm, and the sample cell used is a PDMS tank with a size of 10 mm x 10 mm x 0.1 mm;

[0048] Step 2, irradiate the solution in the sample cell with a 532 nm laser for 10-20 minutes, and use an optical microscope to image the enriched microplastics, with a bright field objective magnification of 40 times, and count and count the polystyrene microplastics in the field of view;

[0049] Step 3, turn on the laser, select a 785 nm laser, and collect the Raman signal of the enriched different number of microplastics in step 2;

[0050] Step 4, data process the Raman peak signal in the collected Raman spectrum to obtain the Raman spectrum of the microplastics.

[0051] Example 4:

[0052] Step 1, in the sample cell, 8.33 ng / mL of 3 μm polystyrene was added to the secondary water, the sample cell base used was a gold-coated cover glass, the surface of which was gold-plated to a thickness of 30-100 nm, and the sample cell used was a PDMS tank with dimensions of 10 mm x 10 mm x 0.1 mm;

[0053] Step 2, the solution in the sample cell was irradiated with a 532 nm laser for 10-20 minutes, and the enriched polystyrene microplastics were imaged using an optical microscope with a 40x magnification bright field objective;

[0054] Step 3, the laser was turned on and a 785 nm laser was selected to collect the Raman signals of the different numbers of microplastics enriched in step 2;

[0055] Step 4, the Raman peak signals in the collected Raman spectrum were processed to obtain the Raman spectrum of the microplastics.

[0056] Example 5

[0057] See Figure 5 The present application also provides another efficient enrichment and detection method for microplastics based on thermal enrichment technology, wherein a central electromagnet 2 and a peripheral electromagnet 3 are arranged below the base 11 of the container 1 containing the microplastic solution, a plurality of heating light sources 4 are arranged concentrically above the central electromagnet 2, and the plurality of heating light sources 4 can form a concentric temperature gradient change in the solution.

[0058] When collecting microplastics, modified ferroferric oxide is added to the microplastic solution, the microplastic particles 7 in the solution combine with the ferroferric oxide particles 5 to form suspended particulate matter; the central electromagnet 2 is powered on and the suspended particulate matter is adsorbed and concentrated, and then the power is turned off to make the central electromagnet 2 lose its magnetic properties; the plurality of heating light sources 4 are controlled to form temperature walls in the solution in parallel light mode, the peripheral electromagnet 3 is powered on to form a peripheral magnetic field on the base 11; the microplastic particles 7 and the ferroferric oxide particles 5 are separated due to heating, the microplastic particles 7 are concentrated towards the center of the base 11, and the microplastic particles 7 move faster after passing through the boundary surface 6 between adjacent temperature walls, and the ferroferric oxide particles 5 are concentrated towards the peripheral electromagnet.

[0059] Preferably, the temperature of the plurality of heating light sources 4 of the present embodiment gradually decreases from the center to the periphery, so that the microplastic particles 7 can finally be concentrated at the center of the base 11, and after the ferroferric oxide particles 5 are concentrated and collected by the peripheral electromagnet 3, they can be recycled for subsequent use.

[0060] The above merely describes the preferred embodiments of the present application, and is not intended to limit the patent scope of the present application. Any equivalent structural changes made under the concept of the present application, or direct / indirect application in other related technical fields, using the content of the present application specification and drawings, are included in the patent protection scope of the present application.

Claims

1. A highly efficient method for the enrichment and detection of microplastics based on thermophoretic enrichment technology, characterized in that, Includes the following steps: Step S1: The container holding the microplastic solution has a central electromagnet and peripheral electromagnets located at the bottom of the base. Several concentric heating light sources are located directly above the central electromagnet. These heating light sources can create a concentric temperature gradient change in the solution. Modified iron(III) oxide is added to the microplastic solution, and the microplastic particles and iron(III) oxide particles in the solution combine to form suspended particulate matter. The central electromagnet is energized to adsorb and concentrate the suspended particulate matter, and then the power is turned off to de-energize the central electromagnet and make it lose its magnetism. By controlling several heating light sources to form temperature walls in the solution in a parallel light manner, the peripheral electromagnets are energized to form a magnetic field on the substrate. The microplastic particles and iron(III) oxide particles separate due to heating. The microplastic particles concentrate towards the center of the substrate. After the microplastics pass through the interface of the adjacent temperature walls, their movement speed increases, and the iron(III) oxide concentrates towards the peripheral electromagnets. The temperature of the heating light sources gradually decreases from the center to the periphery; Step S2: Use a bright-field microscope to observe the distribution of microplastics in the enrichment area and determine the location of the enriched microplastic particles. Step S3: Use Raman spectroscopy to detect the enriched microplastics and obtain specific Raman peak signals of the microplastics.

2. The method as described in claim 1, characterized in that, The bright-field microscope has a magnification of 40x.

3. The method as described in claim 1, characterized in that, The Raman peaks correlated with microplastics are located in the 200-2000 cm⁻¹ range. -1 The location is used as a basis for determining whether microplastics are present.

4. The method as described in claim 1, characterized in that, The specific Raman peak signal refers to the Raman spectral peak intensity.

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