Issues in the Analysis of Microplastics

Importance of the Topic

Microplastic pollution has emerged as a critical environmental concern due to its potential effects on marine ecosystems and food chains. Reliable identification of microplastic fragments is essential for understanding their distribution, degradation pathways and ecological impact. Traditional libraries of infrared spectra often fail to match weathered or thermally altered plastics, creating a gap in qualitative analysis capabilities.

Objectives and Study Overview

This work presents an analytical framework combining Fourier transform infrared (FTIR) spectroscopy with specialized spectral libraries to improve identification of degraded microplastics. Key aims include:

• Demonstrating the challenge of matching degraded polymers against standard libraries.
• Illustrating the benefit of UV- and thermal-damaged plastics libraries for accurate identification.
• Showcasing case studies of microplastic analysis collected from environmental samples.

Applied Methodology and Instrumentation

Microplastic samples were analyzed using ATR-FTIR and infrared microscopy. The instrumentation and resources comprised:

• IRSpirit™ FTIR spectrophotometer with QATR™-S single-reflection ATR attachment for bulk measurements.
• Infrared Microscope AIM-9000 for analysis of particles tens to hundreds of micrometers in size.
• Plastic Analyzer method package with two proprietary spectral libraries:
  
  • UV-Damaged Plastics Library (300+ spectra, 14 polymer types, accelerated 10-year equivalent weathering).
  • Thermal-Damaged Plastics Library (100+ spectra, 13 polymer types, degraded at 200–400 °C).

Main Results and Discussion

Three case studies highlight the improved analytical performance:

• Example 1 – White polypropylene shard from seashore: standard libraries misidentified multiple polymers, while the UV-Damaged Library correctly ranked UV-degraded polypropylene as the top match.
• Example 2 – Time-dependent UV irradiation of polypropylene: FTIR spectra reveal increasing O–H and C=O radical peaks after 100–550 hours, illustrating chemical changes not present in unaged standards.
• Example 3 – Blue microplastic from Arctic cod: microscopic ATR identified polymethyl methacrylate (PMMA) as the major component and detected kaolin (aluminum silicate) as an additive, demonstrating simultaneous organic and inorganic analysis.

Benefits and Practical Applications

Integrating damage-specific spectral libraries with FTIR methodologies offers:

• Enhanced identification accuracy for aged or weathered plastics in environmental monitoring.
• Rapid screening of microscopic particles down to tens of micrometers.
• Improved detection of additives and contaminants alongside polymer identification.
• Support for regulatory compliance, QA/QC in manufacturing and research on plastic degradation.

Future Trends and Potential Applications

Emerging directions to extend this approach include:

• Expanding spectral libraries to cover a broader range of polymers and degradation conditions.
• Incorporating machine-learning algorithms for automated spectral matching and classification.
• Developing portable ATR-FTIR instruments for field-based microplastic screening.
• Combining FTIR with imaging and Raman techniques for multidimensional characterization.

Conclusion

The combination of FTIR spectroscopy, microscopic ATR and specialized UV-/thermal-damaged plastics libraries provides a powerful platform for reliable microplastic identification. This approach addresses the shortcomings of standard libraries when faced with degraded materials and offers practical solutions for environmental analysis and industrial quality control.