JP-7855842-B2 - Method for pre-analysis treatment of microplastics

JP7855842B2JP 7855842 B2JP7855842 B2JP 7855842B2JP-7855842-B2

Inventors

藤里砂

Assignees

株式会社島津製作所

Dates

Publication Date: 20260511
Application Date: 20211018

Claims (1)

A pre-analysis treatment method performed before analyzing microplastics obtained by specific gravity separation treatment with an infrared spectrometer , The gravity separation process includes the step of injecting a sodium iodide solution or a sodium chloride solution into the microplastic. The aforementioned pre-analysis treatment method is: A step of putting the microplastics separated by the specific gravity separation process into a sieve, A step of immersing the sieve containing the microplastics in pure water at a depth shallower than the height of the sieve, A method for pretreatment of microplastics for analysis, comprising the steps of removing the sieve from pure water and then drying the sieve containing the microplastics in a constant-temperature dryer.

Description

This disclosure relates to a method for pre-treatment of microplastics for analysis. Microplastics are tiny plastic particles (5 mm or less). There are concerns about the impact on ecosystems caused by the incorporation of chemicals contained in or adsorbed by microplastics into the food chain. To study and address the effects of such microplastics, it is necessary to analyze them. For example, Japanese Patent Publication No. 6811370 (Patent Document 1) discloses a technique for producing samples for microplastic analysis. Patent No. 6811370 This is a diagram illustrating analysis using a Fourier transform infrared spectrophotometer (FTIR).This is a process diagram showing each step in the pretreatment method for analyzing microplastics.This is an external view of the sieve used in step S3 of Figure 3.This is a diagram to explain the water peak.This figure shows the analysis results obtained from comparison samples without pretreatment.This figure shows the analysis results obtained from pre-treated samples.This figure shows the waveforms from Figure 5 and Figure 6 superimposed on each other. The embodiments will be described in detail below with reference to the drawings. Note that identical or corresponding parts in the drawings are denoted by the same reference numerals, and their descriptions will not be repeated. When analyzing the components of microplastics, a Fourier transform infrared spectrophotometer is generally used. A Fourier transform infrared spectrophotometer is primarily used to estimate the structure of organic compounds. When infrared light is shone on a molecule, the infrared light corresponding to the vibrational energy between the atoms constituting the molecule is absorbed. By examining this absorption degree using infrared spectroscopy, a Fourier transform infrared spectrophotometer can estimate and quantify the structure of a compound. Figure 1 illustrates analysis using a Fourier transform infrared spectrophotometer (FTIR). The Fourier transform infrared spectrophotometer 1 comprises a light source 3, an interferometer 2, a detector 5, and a computer 6. The interferometer 2 includes a movable mirror 21, a beam splitter 22, and a fixed mirror 23. The infrared light emitted from the light source 3 into the interferometer 2 is separated by the beam splitter 22 into two beams: one from a fixed mirror and the other from a moving mirror. The fixed mirror 23 remains stationary, while only the moving mirror 21 moves. The light reflected by the fixed mirror 23 and the moving mirror 21 returns and is combined. This combined light is an interference wave (interferogram) with a phase difference depending on the movement distance of the moving mirror 21. This interference wave is irradiated onto the sample, and the transmitted light is detected by the detector 5. When infrared light is irradiated onto the sample 4 in this configuration, the light intensity detected by the detector differs depending on the movement distance of the moving mirror 21. The infrared spectrum is obtained by performing a Fourier transform on the output of the detector 5 using the computer 6. The following describes the pretreatment method for the sample 4 to be set in the Fourier transform infrared spectrophotometer 1. Figure 2 is a process diagram showing each step of the pretreatment method for microplastic analysis. First, in step S1, an acid hydrolysis treatment is performed on microplastics collected from environmental water to remove organic matter using hydrogen peroxide or similar substances. After dehydrating the material, in the subsequent step S2, a specific gravity separation treatment is performed by pouring in a sodium iodide solution to float the microplastics. Note that a sodium chloride solution may be used instead of the sodium iodide solution. Then, in step S3, a particle size separation treatment is performed by pouring in an aqueous solution of sodium iodide or sodium chloride and scooping up the floating microplastics with a sieve (300 μm). Figure 3 shows the external appearance of the sieve used in step S3 of Figure 3. Microplastics after specific gravity separation are collected in a stainless steel sieve like the one shown in Figure 3. Note that Figure 3 shows an example with a mesh size of 300 μm, but the mesh size may be appropriately changed depending on the particle size of the microplastics to be analyzed. Returning to Figure 2, the sodium iodide removal process is performed in the following step S4. In step S4, the sieve is immersed in pure water to a depth shallower than the sieve's height and left for about one minute. Then, the sieve is gently lifted out of the pure water. It is important to immerse the sieve in pure water stored in a container, as pouring water from above could cause microplastics to escape through the sieve's mesh due to water pressure. In this way, the sodium iodide used in the specific gravity separation process is removed. Note that if a sodium chloride solution