Visualization and (Semi-)quantification of submicrometer plastics through scanning electron microscopy and time-of-flight secondary ion mass spectrometry

Shih-Hsuan Chou; Yung-Kun Chuang; Chi-Ming Lee; Yu-Shan Chang; Ya-Jhu Jhang; Ching-Wen Yeh; Tai-Sing Wu; Chun-Yu Chuang; I-Lun Hsiao

doi:10.1016/j.envpol.2022.118964

Visualization and (Semi-)quantification of submicrometer plastics through scanning electron microscopy and time-of-flight secondary ion mass spectrometry

Environ Pollut. 2022 May 1:300:118964. doi: 10.1016/j.envpol.2022.118964. Epub 2022 Feb 5.

Authors

Shih-Hsuan Chou¹, Yung-Kun Chuang², Chi-Ming Lee³, Yu-Shan Chang², Ya-Jhu Jhang⁴, Ching-Wen Yeh², Tai-Sing Wu⁵, Chun-Yu Chuang⁶, I-Lun Hsiao⁷

Affiliations

¹ Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, 30013, Taiwan; Master Program in Food Safety, College of Nutrition, Taipei Medical University, Taipei, 10031, Taiwan.
² Master Program in Food Safety, College of Nutrition, Taipei Medical University, Taipei, 10031, Taiwan.
³ Core Facility Center, Office of Research and Development, Taipei Medical University, Taipei, 10031, Taiwan.
⁴ Institute of Analytical and Environmental Sciences, National Tsing Hua University, Hsinchu, 30013, Taiwan.
⁵ National Synchrotron Radiation Research Center (NSRRC), Hsinchu, 30013, Taiwan.
⁶ Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, 30013, Taiwan.
⁷ Master Program in Food Safety, College of Nutrition, Taipei Medical University, Taipei, 10031, Taiwan; School of Food Safety, College of Nutrition, Taipei Medical University, Taipei, 11031, Taiwan. Electronic address: ilunhsiao@tmu.edu.tw.

PMID: 35134427
DOI: 10.1016/j.envpol.2022.118964

Abstract

Increasing numbers of studies have demonstrated the existence of nanoplastics (1-999 nm) in the environment and commercial products, but the current technologies for detecting and quantifying nanoplastics are still developing. Herein, we present a combination of two techniques, e.g., scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), to analyze submicron-sized plastics. A drop-casting of a 20-nL particle suspension on a Piranha solution-cleaned silicon wafer with dry ice incubation and subsequent freeze-drying was used to suppress the coffee-ring effect. SEM images were used to quantify particles, and this technique is applicable for 0.195-1.04-μm polystyrene (PS), 0.311-μm polyethylene terephthalate (PET), and 0.344-μm polyethylene (PE) at a minimum concentration of 2.49 × 10⁹ particles/mL. ToF-SIMS could not quantify the particle number, while it could semi-quantitatively estimate number ratios of submicron PE, PET, polyvinyl chloride (PVC), and PS particles in the mixture. Analysis of submicron plastics released from three hot water-steeped teabags (respectively made of PET/PE, polylactic acid (PLA), and PET) was revisited. The SEM-derived sizes and particle numbers were comparable to those measured by a nanoparticle tracking analysis (NTA) regardless of whether or not the hydro-soluble oligomers were removed. ToF-SIMS further confirmed the number ratios of different particles from a PET/PE composite teabag leachate. This method shows potential for application in analyzing more-complex plastic particles released from food contact materials.

Keywords: Coffee-ring effect; Nanoparticle tracking analysis; Nanoplastics; Tea bags; ToF-SIMS.

MeSH terms

Microscopy, Electron, Scanning
Plastics* / analysis
Polyethylene
Polystyrenes / analysis
Spectrometry, Mass, Secondary Ion*

Substances

Plastics
Polystyrenes
Polyethylene