Plastic is one of the widely used materials in our life. Especially less than 5 mm plastic define microplastics (MPs). MPs can be classified primary and secondary microplastics. Primary microplastics refer to plastics less than 5 mm at the time of manufacture, and secondary microplastics refer to plastics that are aged and decomposed into 5 mm or less in the environment. In the case of primary microplastics, the amount of newly generated microplastics can be reduced by limiting production by country, but secondary microplastics increase over time by decomposition in the environment.<br/> These microplastics are founded not only ocean, but also in various media such as tap water, fresh water, air, soil, and sediment where plastics can exist. Therefore, it is necessary to know how many MPs are present in each media and to evaluate their behavior. However, standard microplastic sampling methods and pre-treatment procedures have not been determined for reproducible analysis results. Although research on microplastics larger than 100 μm is being actively conducted, study on MPs smaller than 50 μm, which can be more harmful to the human body, is insufficient.<br/> This study proposes sampling and pretreatment methods to collect and separate microplastics from environmental media. Sampling was based on physical filtration through a stainless filter. Wet peroxide oxidation process and density separation were performed to separate microplastics after collecting all particles. The device  was made of aluminum alloy and the filter was fabricated with 1 to 45 μm pores by woven stainless filter. The recovery rate confirmed to 93.84±2.88% using a microplastic standard material (mean size under 20 μm). As a result of the study, the more compact device developed in this study showed a higher recovery rate even from microplastics with a smaller size than in previous studies. In addition, to prevent cross-contamination that may occur during microplastic sampling, plastics are excluded from the entire process, and microplastics can be classified by size (1~5 μm, 5~20 μm, and 20~45 μm) through a simple multi-step separation structure. Microplastic samples were identified in the air, tap water, and freshwater environmental media of W city in Korea. Analysis was performed using u-Raman and u-FTIR.

Easily reproducible and compatible sampling-pretreatment methods for microplastics of a couple of microns in environmental media

ACS Spring 2022

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