KR102650236B1 - Microplastics analysis method using density separation device for quantitative analysis of microplastics - Google Patents

Abstract

The present invention relates to a density separation device that can more accurately and efficiently measure the concentration (number) of microplastics present in a sample and a microplastic analysis method using the same.

Description

Microplastics analysis method using density separation device for quantitative analysis of microplastics}

The present invention relates to a microplastic analysis method using a density separation device for measuring and analyzing microplastics. More specifically, the present invention relates to a density separation method that can more accurately and efficiently measure and analyze the concentration or number of microplastics present in a sample. This relates to a microplastic analysis method using a device.

Microplastics refer to small pieces of plastic less than 5 mm in size and can be classified into primary microplastics, which are intentionally manufactured and used, and secondary microplastics, which are naturally created by fragmentation through physical/chemical decomposition processes. . In addition, ISO/TR 21960:2020 (ISO/TC 61/SC 14) defines plastic pieces less than 5mm in size as microplastics, and those smaller than 1㎛ as nanoplastics, but in OECD and ECHA, those smaller than 0.1㎛ are defined as nanoplastics. is defined as nanoplastic.

Major microplastics include polyethylene (PE), polypropylene (PP), polybutylene (PB), polystyrene (PS), polycarbonate (PC), polyurethane (PU), cellulose acetate (CA), polyester, and polychloride. These include vinyl (PVC), polyamide (PA), polyvinyl alcohol (PVA), polyacrylic, nylon, epoxy resin, ethylene vinyl acetate, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE). .

These microplastics flow into freshwater water systems such as rivers and lakes and the sea, or when plastic that flows into freshwater water systems such as rivers and lakes and the sea is broken into small particles and turned into microplastics, plankton in freshwater water systems and the sea collects microplastics. Microplastics are ingested, and plankton that ingests microplastics travels through the food chain and eventually accumulates in the human body. In addition, microplastics have the characteristic of absorbing and accumulating harmful chemicals, heavy metals, bisphenol, etc. from the surroundings, so if microplastics and adsorbents accumulate in the human body through ingestion, they can cause cancer, fibrosis, digestive system disorders, reproductive toxicity, etc. Problems are being raised because it has the potential to cause serious illness.

Plastics are characterized by having a relatively low density and a hydrophobic surface. General plastics are subject to processing processes such as sorting using these characteristics, but due to the small size of microplastics, it is known that it is difficult to identify and sort the particle characteristics.

Currently, the microplastic measurement method in use is to place a sample and a density separation solution in a beaker, suspend it using the density difference of the microplastics present in the sample, and separate the suspended microplastics from the beaker using a reagent spoon. In order to remove interfering substances such as organic substances, methods such as oxidizing and filtering the filter and analyzing it with a device such as a Fourier transform infrared spectrometer (FT-IR spectrometer) or directly counting the number of microplastics under a microscope are used.

However, among the above microplastic measurement and analysis methods, the density separation method uses a reagent spoon to separate suspended microplastics from the beaker, so it takes a lot of time to separate and has a low recovery rate (the number of microplastics remaining on the inner wall of the container is large). ) There was a problem of low reliability, such as the accuracy of measurement and analysis results.

Korean Patent No. 10-2420703 discloses a sample pretreatment device including a density difference separation screening unit 100 and a filtering unit 200. The density separation and sorting unit of the registered patent includes a density difference separation device 120 in which the density separation solution and the sample are mixed, and is provided with a suction pipe 300 for transferring the supernatant suspended by the density difference to the filtration unit 200. The above registered patent improves the efficiency of measurement by modularizing and automating density separation and filtration, but it is very difficult to recover the microplastics remaining on the inner wall of the beaker and suction pipe during the process of transferring the supernatant through the suction pipe, such as the accuracy of the measurement and analysis results. There was a problem that reliability was rather low.

Registered Patent No. 10-2511889 provides a microplastic separation technology that can sequentially separate PP, HDPE, PS, and PET, which are microplastics existing in soil, without mixing in organic matter, and that the separated microplastics can be immediately quantified without any pretreatment process. A method is disclosed. However, the registered patent can only separate PP, HDPE, PS, and PET among numerous microplastics, making it difficult to accurately qualitatively/quantitatively analyze all microplastics present in the sample.

The present invention provides a density separation device and analysis method that can increase the reliability of measurement and analysis results, such as recovery rate, accuracy, and precision of microplastics in samples.

The present invention provides a density separation device and analysis method that can qualitatively and quantitatively measure and analyze all microplastics present in a sample.

In one aspect, the present invention:

Pedestal (10) ;

A cylindrical lower container (20) fixed to the upper part of the pedestal (10);

A valve (30) on one side of which is coupled and fixed to the upper part of the lower container; and

It is provided with a cylindrical upper container 40 that is coupled and fixed to the other side of the valve,

In the open state of the valve 30, the lower container 20, the valve 30, and the upper container 40 are in communication, and the microplastics in the sample filled inside float in the upper container by the density separation solution,

When the valve 30 is closed, the valve separates and blocks the space between the lower container 20 and the upper container 40,

The lower container, upper container, and valve are made of stainless steel and are free from microplastics, providing a density separation device for measuring and analyzing microplastics.

In another aspect, the present invention includes the steps of introducing a sample and a primary density separation solution into the density separation device 100;

A step of allowing it to stand for a predetermined period of time;

A first separation step of separating and storing the upper layer solution after blocking the valve 30 of the density separation device, and opening the valve 30 of the density separation device to leave the lower layer solution as is;

The residual sample of the lower layer solution and the secondary density separation solution are reintroduced into the density separation device, left to stand for a predetermined time, and the valve 30 of the density separation device is blocked, and then the upper layer solution is separated and stored. Separation step;

A filtration step of combining and filtering the upper layer solutions obtained and stored separately in the first and second separation steps;

Oxidizing organic matter by adding hydrogen peroxide to the residue remaining after the filtration step;

Filtering, washing and drying the residual material after the organic oxidation has been completed;

It includes the step of analyzing the residual material with a measuring device, wherein the primary density separation solution has a density of 1.8 kg/L or less, and the secondary density separation solution has a density of 1.8 to 2.3 kg/L. It is related to method.

The density separation device for microplastic analysis of the present invention can block the elution of microplastics from the container itself by using a container and valve made of stainless steel, and also has a cylindrical shape with a reduced surface area of the inner wall (inner diameter in the range of 20 to 40 mm). By using containers, the concentration or number of microplastics remaining on the inner wall of the container can be reduced. In other words, the density separation device for microplastic analysis of the present invention prevents microplastics from eluting from the container itself and reduces the concentration or number of microplastics remaining on the inner wall of the container, thereby improving the accuracy and precision of qualitative/quantitative analysis of microplastics. Reliability can be increased.

In addition, the microplastic measurement and analysis method of the present invention first separates low-density microplastics by first injecting a low-density density separation solution, and secondarily injects a high-density density separation solution into the residual sample to separate the low-density and microplastics remaining in the residual sample. By selectively and effectively suspending high-density microplastics, it is possible to recover most of the microplastics of different specific gravity in the sample.

Figure 1 is a front view of the density separation device for microplastic analysis of the present invention, Figure 2 is a side view of Figure 1, and Figure 3 is a top view of Figure 1.

Below, preferred embodiments of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the description or drawings of the following embodiments. That is, the terms used in this specification are merely used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In addition, terms such as "comprise" or "have" used in the specification are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but one or more It should be understood that this does not exclude in advance the presence or addition of other features, numbers, steps, operations, components, parts, or combinations thereof.

Additionally, terms such as “unit,” “unit,” and “module” used in the specification refer to a unit that processes at least one function or operation, and may be implemented as hardware, software, or a combination of hardware and software.

Figure 1 is a front view of the density separation device for measuring and analyzing microplastics of the present invention, Figure 2 is a side view, and Figure 3 is a plan view of Figure 1.

Referring to Figures 1 to 3, the density separation device for measuring and analyzing microplastics of the present invention includes a stand (10), a lower container (20), a valve (30), and an upper container (40).

The stand 10 is a plate-shaped structure that supports the container. The stand 10 may be made of metal such as stainless steel or synthetic resin, and is preferably made of metal.

The lower container 20 is a cylinder or tubular structure fixed to the upper part of the pedestal 10.

One side of the valve 30 is coupled and fixed to the upper part of the lower container.

The valve 30 may be a ball valve that has excellent sealing ability and in which little fluid flow occurs during the opening and closing process of the valve.

The valve 30 may include a body 31 in which a flow path a is formed, a ball 32 located in the flow path a and having a through hole, and a cock 33 that rotates the ball.

The height (h) of the valve 30 may be 1/2 to 9/10 of the container height (H), but is not necessarily limited thereto.

The upper container 40 is a cylinder or tubular container that is coupled and fixed to the other side of the valve.

Referring to Figures 1 and 2, in the density separation device, the interior of the lower container, valve, and upper container are in communication, and a sample, density separation solution, etc. can be injected into these interiors.

When a sample and a density separation solution are injected into the density separation device, the density separation solution is filled in the upper and lower containers as well as the flow path 31 of the valve 30, and the microplastics in the sample are filled in the valve flow path 31. and can be floated into the upper container through the through hole of the ball 32.

That is, when the valve 30 is open, the lower container 20, the valve 30, and the upper container 40 are in communication.

When the valve 30 is closed, the valve can separate and block the space between the lower container 20 and the upper container 40.

The lower container, upper container, and valve of the present invention are made of stainless steel. If the lower container, upper container, and valve are made of plastic or a mixed material including them, the reliability, such as the accuracy of the measurement and analysis results of the concentration or number of microplastics, is reduced due to the leaching of the plastic.

The lower container and the upper container may have an inner diameter of 20 to 40 mm, preferably the inner diameter may be 20 to 30 mm, and more preferably 20 to 25 mm.

If the inner diameter is less than 20 mm, it is difficult to inject an appropriate amount of sediment sample, and if it exceeds 40 mm, the surface area of the inner wall of the container is large, and the content of microplastics remaining on the inner wall is large, which reduces reliability, such as the accuracy of measurement and analysis results. You can.

The density separation device may have a ratio of inner diameter (a) to height (H) in the range of 1:8 to 12.

If the height ratio exceeds 12 (inner diameter ranges from 20 to 40 mm), the size of the device is large, making it inconvenient to handle and reducing ease of use and portability. If the height ratio is less than 7, the device is small or the surface area of the inner wall of the device is large, making it difficult to inject an appropriate amount of sample to ensure the reliability of the measurement and analysis results, and the representativeness is poor.

The present invention relates to a method for analyzing microplastics using the density separation device 100.

The microplastic analysis method includes an input step, a standing step, a primary separation step, a secondary separation step, a filtration step, an oxidation step, a drying step, and an analysis step.

The input step is a step of inputting the sample and the primary density separation solution into the density separation device 100. There are no special restrictions on the sample. For example, the samples may be fresh water and sea water, and sediments, plastic-containing solutions, pastes or ground solids.

The density of the primary density separation solution may be 1.8 kg/L or less, preferably the density of the primary density separation solution may be 1.0 to 1.8 kg/L, and more preferably 1.1 to 1.8 kg/L. . More specifically, the primary density separation solution may be Nal or NaCl.

The standing step is a step in which the sample and the density separation solution are stirred and then maintained at room temperature for a predetermined time. For example, the standing step may be 6 to 24 hours.

The first separation step is to separate and store the upper layer solution after blocking the valve 30 of the density separation device, and then open the valve 30 of the density separation device to separate and store the lower layer solution.

In the first separation step, the upper layer solution can be stored by pouring it into a separate beaker by tilting the density separation device with the valve closed. Then, the valve is opened and the lower layer solution containing the residual sample is allowed to remain in the density separation device.

In the secondary separation step, the residual sample from which the lower layer solution has been filtered and the secondary density separation solution are reintroduced into the density separation device, left to stand for a predetermined time, and the valve 30 of the density separation device is blocked. This is the step of separating and storing the upper layer solution.

In the second separation step, the residual sample from the lower layer solution of the first separation step is introduced into the density separation device together with the second density separation solution.

The density of the secondary density separation solution may be 1.8 to 2.3 kg/L. More specifically, the secondary density separation solution may be ZnBr ₂ .

In the second separation step, like the first separation step, the residual sample and the second density separation solution are stirred and left at room temperature for a predetermined time. Subsequently, in the secondary separation step, the valve 30 of the density separation device is blocked, the density separation device is tilted, and the upper layer solution can be poured into a separate beaker and stored.

The filtration step is a step of combining and filtering the upper layer solutions obtained and stored separately in the first separation step and the second separation step. That is, the filtration step is a step of combining the upper layer solution containing microplastics recovered using the first density separation solution and the upper layer solution containing microplastics recovered using the second density separation solution and filtering them through a filter.

The oxidation step is a step of oxidizing organic matter by adding hydrogen peroxide to the residual material remaining after the filtration step. The oxidation step can remove interfering substances such as various organic substances present on the surface of separated microplastics.

More specifically, the oxidation step is supplied together with hydrogen peroxide and heated to a temperature of 40°C to 100°C, preferably 60°C to 80°C to oxidize and remove interfering substances such as organic substances.

The drying step is a step of filtering, washing, and drying the residual material after the organic oxidation has been completed. In the drying step, the residual material after organic matter oxidation is connected to a vacuum pump to filter, the filtered residual material can be washed with distilled water, and dried in a drying oven.

The analysis step is a step in which the dried residual material is analyzed using a measuring device. The measuring device may be one or more of a Fourier transform infrared spectrometer (FT-IR spectrometer), differential scanning calorimeter (DSC), and thermogravimetry analyzer (TGA).

The microplastic measurement and analysis method of the present invention obtains the upper solution suspended in the first and second separation steps, and measures and analyzes the number or content of microplastics from the residual material recovered by filtering the upper solution. You can.

As described above, in the first separation step, low-density microplastics with a density of 1.8 kg/L or less can be separated and recovered by floating low-density microplastics with a density of 1.8 kg/L or less using Nal or NaCl with a density of 1.8 kg/L as a primary density separation solution. there is. The low-density microplastics include polyethylene (PE), polypropylene (PP), polybutylene (PB), polystyrene (PS), polycarbonate (PC), polyurethane (PU), cellulose acetate (CA), polyester, poly It may be vinyl chloride (PVC), polyamide (PA), polyvinyl alcohol (PVA), polyacrylic, nylon, epoxy resin, ethylene vinyl acetate, etc.

In the second separation step, high-density microplastics that were not recovered in the first separation step can be recovered by floating them using ZnBr ₂ with a density of 2.3 kg/L as a second density separation solution. The high-density microplastic may be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), etc.

In addition, in the second separation step, the low-density microplastics present in the residual sample (sediment sample), which settle together with the sediment in the first separation step (when surrounded by sediment or located under sediment, etc.) and cannot float, are separated into primary density. It can be suspended by adding a secondary density separation solution that has a higher density than the separation solution.

In other words, the microplastic measurement and analysis method of the present invention first selectively and effectively separates low-density microplastics by first injecting a low-density density separation solution, and secondarily injecting a high-density density separation solution into the residual sample to remove the remaining sample. By selectively and intensively suspending high-density microplastics, the recovery rate, accuracy, and precision of microplastics in the sample can be increased.

Hereinafter, the following examples are presented to aid understanding of the present invention. However, the following examples are provided only to make the present invention easier to understand, and the content of the present invention is not limited by the examples.

First standard sample preparation

200㎍ of dry polymer (Duke Standard, dry polymer microplastic, 200㎛, 4.396㎍, density 1.05 g/cm ³ ) was taken on a scale. Polymer particles (microplastics) equivalent to 200 μg were counted under a microscope. The number of particles was approximately 45 to 50.

Preparation of second standard sample (standard sample with more particles than first standard sample)

About 450 ㎍ of dry polymer (Duke Standard, dry polymer microplastick, 200㎛, 4.396㎍, density 1.05 g/cm ³ ) was taken on a scale. Polymer particles (microplastics) equivalent to 450 μg were counted under a microscope. The number of particles was approximately 90 to 96.

Example 1

(1) 100 mL of the previously prepared first standard sample (200㎍ = 50) and NaI solution (specific gravity 1.6 kg/L) were added to the density separation device of Example 1 in Table 1 below, mixed, and left for 12 hours. I ordered it. After closing the valve of the density separation device, the supernatant was poured into a separate beaker.

(2) The supernatant was poured onto filter paper and filtered (filter paper specifications: diameter 47 mm, pore size: 20 ㎛).

(3) Washing was repeated several times with distilled water. The filtered residual material (standard sample) was placed in a dry oven and dried at 45°C for 12 hours.

(4) The number of microplastics was measured using FT/IR analysis equipment with the following specifications and is shown in Table 2. When the plastic match rate was more than 65% compared to the library database, it was considered a microplastic.

Collection mode: Transmission, Detector: Array

Aperture: width 25μm, height 25 μm

Detector spectra range: (4000~715) cm ^-1

Comparative Example 1

(1) 100 mL of the previously prepared standard sample (200 ㎍ = 45) and NaI solution (specific gravity 1.6 kg/L) were added and mixed into the beaker of Comparative Example 1 in Table 1 below and allowed to stand for 12 hours.

The supernatant was taken with a reagent spoon and transferred to a new beaker. The processes (2) to (5) were performed in the same manner as in Example 1, and the measured number of microplastics is shown in Table 2.

Comparative Example 2

(1) The previously prepared standard sample (200 ㎍ = 45) and 100 mL of NaI solution (specific gravity 1.6 kg/L) were added and mixed into the device (made of plastic) of Comparative Example 2 in Table 1 below and mixed for 12 hours. It was made political.

After closing the valve of the device, the supernatant was poured into a separate beaker. The processes (2) to (5) were performed in the same manner as in Example 1, and the measured number of microplastics is shown in Table 2.

Example 2 :

(1) A sample of the previously prepared second standard sample (200 μg = 100 pieces) mixed with a pre-dried field sediment sample (5 g) and 100 mL of NaI solution (specific gravity 1.6 kg/L) were mixed according to Example 1 in Table 1 below. After being added and mixed to the density separation device, it was left to stand for 12 hours.

After closing the valve of the density separation device, the supernatant was poured into a separate beaker. Next, the valve of the density separation device was opened and the lower layer liquid was poured onto the filter paper to separate the density separation solution (first separation).

The residual sample remaining on the filter paper and 100 mL of ZnBr ₂ solution (specific gravity 2.3 kg/L) were injected and mixed into the density separation device and left for 12 hours. After closing the valve of the density separation device, the supernatant was poured into a separate beaker and transferred (secondary separation).

(2) The supernatants obtained from the first and second separations were combined and filtered (filter paper specifications: diameter 47 mm, pore size: 20 ㎛).

(3) The filter paper was transferred to a beaker, 100 mL of 30% hydrogen peroxide was added, and the mixture was heated and stirred at 62.5°C and 180 RPM. The oxidation time was at least 24 hours, and the decomposition of organic substances was checked with the naked eye.

(4) The residual material (sample) after organic matter decomposition was connected to a vacuum pump and filtered, and then washed several times with distilled water. The filtered residual material was placed in a dry oven and dried at 45°C for 12 hours.

(5) The number of microplastics was measured using FT/IR analysis equipment with the following specifications and is shown in Table 2. Compared to the library database, when the plastic match rate was more than 65%, it was considered microplastic.

Collection mode: Transmission, Detector: Array

Aperture: width 25μm, height 25 μm

Detector spectra range: (4000~715) cm ^-1

Comparative Example 3

(1) Comparative example of the sample of Example 2 (a sample mixed with the second standard sample (200 μg = 100 pieces) and pre-dried field sediment sample (5 g)) and 100 mL of NaI solution (specific gravity 1.6 kg/L) It was added and mixed into beaker 1 and left to stand for 12 hours.

The supernatant was taken with a reagent spoon and transferred to a new beaker. Next, the lower layer liquid was poured onto filter paper to separate the density separation solution (first separation).

The residual sample remaining on the filter paper and 100 mL of density-separated ZnBr ₂ solution (specific gravity 2.3 kg/L) were injected and mixed into the density separation device and left for 12 hours. The supernatant was taken with a reagent spoon and transferred to a separate beaker. The processes (2) to (5) were performed in the same manner as in Example 2, and the measured number of microplastics is shown in Table 2.

Comparative Example 1
Comparative Example 3 Comparative Example 2 Example 1
Example 2 Beaker inner diameter 65mm
Beaker height 100mm Device inner diameter 25mm
Device height 160mm Inner diameter: 23mm
Height 192mm

division Added PS (pcs) Number of PS (units) Recovery rate (%) note Example 1 50 48 94 Comparative Example 1 45 28 63 Comparative Example 2 45 36 80 Large amounts of PVC detected Example 2 93 68 73 Comparative Example 3 93 44 47

Comparative Example 1 is a case in which the supernatant was recovered using a beaker with a large inner diameter and a reagent spoon, and Comparative Example 2 is a case in which a separation device made of PVC with an inner diameter of 25 mm was used. The sample recovery rate in Comparative Example 1 was only 63% and Comparative Example 2 was only 80%, but in Example 1, the inner diameter of the device was small and only about 2 microplastics remained on the inner wall, showing an excellent recovery rate of 94%. Additionally, in Comparative Example 2, a significant amount of PVC was detected in addition to the standard sample.

Example 2 and Comparative Example 3 used samples mixed with standard samples and field sediments, Example 1 recovered the supernatant using a density separation device, and Comparative Example 3 recovered the supernatant using a beaker and reagent spoon. did.

Referring to Table 2, the recovery rate of Comparative Example 3 was 47%, which was significantly reduced compared to Example 2 (recovery rate of 73%). This is because the loss of microplastics is very large through repeated use of the density separation solution suspended from a beaker with a large inner diameter with a reagent spoon dozens of times. However, using the density separation device of the present invention, the solution can be poured and separated at once. It can be confirmed that the loss of microplastics can be minimized.

The reason why the recovery rate of Example 2 is somewhat lower than that of Example 1 is that the standard sample settles together with the sediment in the field (surrounded by sediment or located under the sediment, etc.) and cannot be effectively separated due to interfering substances. It shows that there is.

Although the present invention has been described in detail above as an example of a preferred embodiment of the present invention, this description simply describes and discloses an exemplary embodiment of the present invention. Those skilled in the art will readily recognize that various changes, modifications and variations can be made from the above description and accompanying drawings without departing from the scope and gist of the present invention.

Claims (5)

delete delete delete A pedestal 10, a cylindrical lower container 20 fixed to the upper part of the pedestal 10, a valve 30 on one side of which is coupled and fixed to the upper part of the lower container, and a cylindrical-shaped lower container 20 fixed to the other side of the valve. It is provided with an upper container 40, and when the valve 30 is opened, the lower container 20, the valve 30, and the upper container 40 are in communication, so that the microplastics in the sample filled inside are in the density separation solution. It floats in the upper container, and when the valve 30 is closed, the valve separates and blocks the space between the lower container 20 and the upper container 40, and the lower container, upper container, and valve are made of stainless steel free from microplastics. As a microplastic measurement and analysis method using the density separation device 100, which is a material, the microplastic measurement and analysis method is
Injecting the sample and the primary density separation solution into the density separation device (100);
A step of allowing it to stand for a predetermined period of time;
A first separation step of separating and storing the upper layer solution after blocking the valve 30 of the density separation device, and allowing the lower layer solution to stand by opening the valve 30 of the density separation device;
The residual sample of the lower layer solution and the secondary density separation solution are reintroduced into the density separation device, left to stand for a predetermined time, and the valve 30 of the density separation device is blocked, and then the upper layer solution is separated and stored. Separation step;
A filtration step of combining and filtering the upper layer solutions obtained and stored separately in the first and second separation steps;
Oxidizing organic matter by adding hydrogen peroxide to the residue remaining after the filtration step;
Filtering, washing and drying the residual material after the organic oxidation has been completed;
Comprising the step of analyzing the residual material with a measuring device,
The primary density separation solution has a density of 1.8 kg/L or less, and the secondary density separation solution has a density of 1.8 to 2.3 kg/L. The microplastic measurement and analysis method according to claim 4, wherein the first density separation solution is Nal or NaCl, and the second density separation solution is ZnBr ₂ .