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KMID : 0385520190320060243
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Analytical Science & Technology
2019 Volume.32 No. 6 p.243 ~ p.251
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Identification of Microplastics in Sea Salts by Raman Microscopy and FT-IR Microscopy
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Cho Soo-Ah
Cho Won-Bo
Kim Su-Bin
Chung Jae-Hak
Kim Hyo-Jin
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Abstract
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Microplastics (MP) are found in large quantities in the oceans, posing a major threat to the ecosystem.
In Korea, MPs have been reported to be detected in sea salts. In order to analyze MPs, information on their composition, size, and shape is required. FT-IR microscopy is used frequently to measure sizes larger than 20 μm. Recently, however, Raman microscopy, which can analyze ultrafine plastics below 20 μm, has been applied extensively. In this study, 10.0 g samples of commercially available salts were dissolved and filtered through a 45 μm mesh filter with a size of 25.4 mm × 25.4 mm. These filtered samples were then analyzed by both FT-IR microscopy and Raman microscopy. A total of four MPs, including three polyethylene (PE) of size 70- 100 μm and a polypropylene (PP) of size 170 μm, were detected by FT-IR microscopy, while 10 MPs, including nine PE of size 10-120 μm and one polystyrene (PS) of size 40 μm, were detected by Raman microscopy.
Approximately, 1,000 MPs/kg was estimated, which was almost two times higher than the previous reported levels (~550-681 particles/kg in sea salts); this is because Raman microscopy can detect much smaller MPs than FT-IR microscopy. A total of 113 particles were found using Raman microscopy: Carbon (35, 31.5 %), minerals (28, 25 %), and glass (16, 14.4 %) were dominant, forming around 70% of the total, but MPs (10, 8.8 %) and cellulose (5, 4.5 %) were also found. Raman microscopy has great potential as an accurate method for measuring MPs, as it can measure smaller size MPs than FT-IR microscopy. It also has a reduced sample preparation time.
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KEYWORD
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microplastic, Identification, Polyethylene (PE), Polypropylene (PP), raman microscopy, FT-IR microscopy, table salts
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