Measurement of Microplastics and Use of Thermal-Damaged Plastics Library

Significance of the topic

The accumulation of microplastics in marine environments poses a threat to ecosystems and human health. Identification of polymer types and degradation states is essential for tracking pollution sources and informing mitigation strategies.

Objectives and overview of the study

This work demonstrates a spectrophotometric approach using a compact ATR-FTIR instrument combined with a thermal-damaged plastics spectral library to qualitatively identify microplastics collected from a sea coast.

Methodology and instrumentation

Microplastics under 5 mm were analyzed by the ATR method. Samples were placed on a diamond ATR prism to obtain surface absorption spectra with a penetration depth of several micrometers. A thermal-damaged plastics library containing infrared spectra for 13 polymers heated from 200 to 400 °C was employed to match degraded samples.

Instrumentation

• IRSpirit Compact Fourier Transform Infrared Spectrophotometer
• QATR-S Attenuated Total Reflection accessory with diamond prism
• DLATGS detector
• Resolution 4 cm-1 with 40 scan accumulation and Happ-Genzel apodization

Main results and discussion

White and red microplastic particles were matched to polypropylene heated at 200 °C for 4 hours and polyethylene heated at 200 °C for 2 hours, respectively. Similar oxidative degradation patterns, including OH and C=O stretching, were observed in both UV and thermal degradation studies, confirming the suitability of the thermal library.

Benefits and practical applications

This compact ATR-FTIR setup enables rapid and simple qualitative analysis of environmental microplastics. The use of a thermal-damaged library facilitates identification of UV-degraded polymers without extensive sample preparation.

Future trends and opportunities

• Expansion of spectral libraries to cover a broader range of polymers and degradation conditions
• Integration with imaging techniques for spatial distribution analysis
• Automation of spectral matching workflows
• Application in routine monitoring of freshwater and marine pollution

Conclusion

The combination of a portable ATR-FTIR instrument and a thermal-damaged plastics library offers a practical solution for the qualitative identification of degraded microplastics in environmental research.

Reference

1. Hiroshi Yamanoi 2007 The Mechanisms of Polymer Degradation Discoloration and Stabilization Journal of the Materials Life Society Japan 19 3 103 108
2. Yoshio Oki 1973 Degradation of Plastic Materials Journal of the Metal Finishing Society of Japan 24 4 229 238