Issues in the Analysis of Microplastics

Significance of the Topic

Microplastics are emerging contaminants with the potential to disrupt aquatic ecosystems, wildlife, and human health. Accurate identification and quantification of microscopic plastic particles, especially those altered by environmental weathering, are critical for reliable environmental monitoring, regulatory compliance, and risk assessment.

Objectives and Study Overview

This work introduces Shimadzu’s Plastic Analyzer system and associated analytical strategies designed to enhance the qualitative and quantitative analysis of microplastics. The primary aims include: reproducing environmental degradation in spectral libraries for plastics, improving match accuracy for weathered polymers, and characterizing microplastics down to a few micrometers via microscopy.

Methodology and Instrumentation Employed

The analytical workflow integrates bulk and microscopic spectroscopic techniques:

• FTIR Spectrophotometry with single-reflection ATR for preliminary screening.
• Plastic Analyzer method package, comprising:
  • UV-Damaged Plastics Library: 300 + spectra from 14 polymers aged under accelerated UV exposure (up to 10 years equivalent).
  • Thermal-Damaged Plastics Library: 100 + spectra from 13 polymers heated between 200–400 °C.
• Infrared Microscope (AIMsight™) for transmittance mapping of particles from a few micrometers to several hundred micrometers.
• Infrared/Raman Microscope (AIRsight™) for complementary molecular identification and micro-sizing, controlled by AMsolution software with a length-measurement function.

Main Results and Discussion

Illustrative case studies highlight system performance:

• Example 1: Shore-collected white plastic shards analyzed with standard libraries produced ambiguous matches. The UV-Damaged Plastics Library unequivocally identified UV-degraded polypropylene.
• Example 2: Microplastics filtered on PTFE paper were mapped by IR transmittance, revealing a majority of polypropylene and a minority of polyethylene.
• Example 3: Raman microspectroscopy of sub-10 μm particles distinguished polyethylene and polystyrene, and the software measured particle dimensions (~5 μm).

Benefits and Practical Applications

Specialized degraded-plastic spectral libraries markedly enhance identification accuracy for weathered microplastics, enabling reliable qualitative and quantitative analyses. The combined FTIR and Raman microscopy approach supports detailed compositional profiling and size characterization at micrometer scales, benefiting environmental monitoring, quality control in plastics manufacturing, and academic research on microplastic distribution.

Future Trends and Potential Applications

Advances may include expansion of degradation libraries to additional polymer types, implementation of machine-learning algorithms for automated spectral recognition, and integration with other hyphenated techniques (e.g., imaging-mass spectrometry). Development of high-throughput workflows and standardized protocols will facilitate broader adoption in regulatory laboratories and research institutions.

Conclusion

Shimadzu’s Plastic Analyzer system, with its UV- and thermal-degradation libraries and advanced microscopy capabilities, addresses key challenges in microplastic analysis by improving the accuracy, sensitivity, and throughput of both compositional and size determinations.