Analysis of Microplastics by iSpect™ DIA-10 Dynamic Particle Image Analysis System and AIM-9000 Infrared Microscope

Importance of the Topic

Microplastics, ranging from a few micrometers to several millimeters, have emerged as a critical environmental and health concern. Their widespread presence in water bodies affects marine ecosystems and potentially human health. Early detection and characterization are essential for environmental protection and pollution mitigation efforts.

Objectives and Overview of the Study

This study demonstrates a hybrid analytical approach combining dynamic particle image analysis and infrared microscopy. The main objectives are:

• To quantify particle count concentration and size distribution of microplastics in environmental water.
• To characterize particle shape using high-throughput image analysis.
• To perform chemical identification and spatial mapping of microplastic composition.

Methodology and Instrumentation

The workflow integrates two key systems:

• iSpect™ DIA-10 Dynamic Particle Image Analysis System
  – Microcell imaging captures particles (5–100 μm) in a narrow flow channel
  – Sample volume as low as 50 μL
  – Frame rate: 8 fps; flow rate: 0.1 mL/min; total volume: 150 μL
• IRTracer™-100 FTIR Spectrophotometer with AIM-9000 Infrared Microscope
  – Spatial resolution via 20 μm × 20 μm aperture
  – Spectral resolution: 8 cm⁻¹; accumulation: 5 scans; apodization: square-triangle
  – Mapping range: 460 μm × 1,780 μm; MCT detector

Main Results and Discussion

Dynamic image analysis of environmental water yielded:

• Particle count concentration: 5 309 particles/mL
• Average particle size: 24.315 μm
• Size distribution peak in the 10–30 μm range
• Varied shapes observed, including rod-like and fibrous forms

Infrared mapping focused on rod-like microplastics revealed a characteristic CH₃ bending vibration at 1 400–1 339 cm⁻¹. Chemical imaging confirmed these particles as polypropylene, highlighting spatial distribution of the polymer on filter paper.

Benefits and Practical Application of the Method

This hybrid approach offers:

• High-throughput quantification of microplastic abundance and morphology
• Minimal sample consumption and automated analysis
• Rapid, non-destructive chemical identification with spatial mapping
• Applicability to environmental monitoring, QA/QC, and research settings

Future Trends and Potential Applications

Advances may include:

• Integration with machine learning for automated classification of particle types
• Real-time, in-field monitoring systems for water quality assessment
• Enhanced spectroscopic resolution for detecting smaller nanoplastics
• Expansion to soil and air sample analysis for comprehensive environmental surveillance

Conclusion

The combined use of dynamic particle image analysis and infrared microscopy enables efficient characterization of microplastic shape, concentration, and composition. This methodology supports environmental research and pollution control by delivering reliable, rapid insights into microplastic contamination.

References

Maeda H., Fuji R. Application Note A605: Spectrophotometric Analysis of Microplastics by iSpect DIA-10 and AIM-9000 Infrared Microscope. Shimadzu Corporation, First Edition: November 2019.