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Identifying Microplastics in Laboratory and Atmospheric Aerosol Mixtures via Optical Photothermal Infrared and Raman
Rebecca L Parham1, Abbygail M Ayala1, Lauren Meagher1
1Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
Analytical Chemistry
|August 14, 2025
Summary
This study introduces a new method, computer-controlled optical photothermal infrared (CC-O-PTIR) coupled with Raman microspectroscopy, to identify small microplastics (MPs) in the atmosphere. This technique improves detection of airborne MPs, crucial for understanding environmental and health impacts.
Area of Science:
- Environmental Science
- Analytical Chemistry
- Spectroscopy
Background:
- Microplastics (MPs) are pervasive environmental contaminants with largely unknown impacts on human health, ecosystems, and climate.
- Current methods like Infrared (IR) microscopy are limited in detecting small, atmospherically relevant microplastics (≤10 μm) due to diffraction limits.
- Understanding atmospheric MP presence is critical for assessing exposure risks.
Purpose of the Study:
- To develop and validate a novel technique for identifying and classifying microplastics at atmospherically relevant sizes (≤10 μm).
- To enhance the spatial resolution and efficiency of microplastic analysis in environmental samples.
- To enable better assessment of airborne microplastic contamination and its potential consequences.
Main Methods:
- Utilized optical photothermal IR coupled with Raman (O-PTIR+Raman) microspectroscopy to analyze microplastics.
- Improved O-PTIR spatial resolution to detect particles ≥ ∼0.8 μm by analyzing elastic scattering changes.
- Employed a computer-controlled (CC) particle analysis module to reduce analysis time by at least 30%.
Main Results:
- Successfully identified and distinguished microplastics like high-density polyethylene (HDPE), polypropylene (PP), and polystyrene (PS) in samples containing atmospherically relevant standards and ambient particles.
- Demonstrated the capability to analyze microplastics ≤10 μm, including those impacting pre-collected atmospheric samples.
- Validated the CC-O-PTIR+Raman technique for analyzing microplastics in complex atmospheric matrices.
Conclusions:
- CC-O-PTIR+Raman significantly expands capabilities for identifying microplastics in the atmosphere, including particles ≤10 μm.
- The enhanced spatial resolution and reduced analysis time improve the efficiency of atmospheric microplastic research.
- This advancement facilitates a better understanding of atmospheric microplastic exposure and its associated health and environmental risks.
