Microplastic Analysis Using the AIM-9000 Infrared Microscope

Importance of the Topic

Microplastics, defined as plastic fragments measuring a few micrometers up to 5 mm, have emerged as critical environmental pollutants. Their persistence in marine and freshwater ecosystems poses risks to wildlife and human health through ingestion and chemical contamination.

Objectives and Study Overview

This study demonstrates the qualitative identification and spatial mapping of primary and secondary microplastics using an infrared microscope. Primary microplastics from a cosmetic scrub and secondary particles collected from environmental water samples were analyzed to showcase the technique's capability in distinguishing polymer types and visualizing their distribution.

Methodology

• Primary Microplastic Analysis
  Scrub samples were dissolved in water, filtered, and individual particles were compressed in a diamond cell. Infrared transmission spectra were acquired to identify polymer type.
• Secondary Microplastic Mapping
  Environmental water samples were filtered on a PTFE membrane to collect mixed microplastics. Transmission microspectroscopic mapping was performed across a defined area to map polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) based on characteristic absorption peaks.

Instrumentation Used

• FTIR Spectrophotometer: IRTracer-100
• Infrared Microscope: AIM-9000
• Detector: Mercury Cadmium Telluride (MCT)
• Analysis Conditions:
  
  • Resolution: 8 cm-1
  • Apodization: Square-Triangle
  • Aperture Size: 50 µm × 50 µm
  • Accumulations: 40 (primary), 1 (mapping)
  • Mapping Area: 1800 µm × 2600 µm with 50 µm intervals

Main Results and Discussion

Primary microplastics extracted from the scrub were identified as polystyrene based on characteristic IR peaks. The mapping analysis of mixed particles on a PTFE filter revealed distinct spatial distributions of PE, PP, and PET by measuring peak heights at 718 cm-1, 2839 cm-1, and 1724 cm-1, respectively. Color-coded maps highlighted areas of high and low polymer concentrations, and representative spectra confirmed material assignments.

Benefits and Practical Applications

The combined FTIR microscope approach enables rapid, non-destructive identification of microplastic composition and spatial distribution at the microscale. This capability supports environmental monitoring, contamination assessment in consumer products, and quality control in microplastic research laboratories.

Future Trends and Potential Applications

Advancements may include automated spectral classification with machine learning, expanded spectral libraries for emerging polymers, and portable IR microscopy systems for field analyses. Integrating imaging analytics and high-throughput mapping will enhance large-scale environmental surveys and real-time monitoring.

Conclusion

Infrared transmission microscopy using the IRTracer-100 and AIM-9000 effectively identifies and maps primary and secondary microplastics. The method offers high sensitivity for small samples and provides detailed chemical and spatial information to support environmental studies and regulatory efforts.

References

1. Ministry of the Environment (Japan). Annual Report on the Environment, the Sound Material-Cycle Society and Biodiversity in Japan 2017; Part II, Chapter 4, Section 7.
2. Ministry of the Environment (Japan). Marine Litter: 2016 New Year Symposium on Marine Litter Documentation.