Analysis of Microplastics Using AIRsight Infrared/Raman Microscope

Importance of topic

Microplastic contamination in aquatic environments poses growing risks to ecosystems and human health. Accurate identification of particle composition and size is critical for tracing pollution sources and assessing biological impacts. Combining infrared and Raman spectroscopy on a single platform enhances analytical efficiency and data consistency.

Objectives and study overview

This study demonstrates the use of the AIRsight infrared/Raman microscope to characterize environmental microplastics. Key goals include simultaneous material identification and size measurement of diverse microplastic particles collected from water samples.

Methodology and instrumentation

Sample collection and preparation

• Environmental water filtered through PTFE membrane filters to capture microplastics
• Filtered samples placed directly on the microscope stage without transfer

Infrared analysis

• Instrument: IRXross and AIRsight microscope
• Transmission mode on intact PTFE filter (minimal interference except around 1200 cm-1)
• Resolution 8 cm-1, 30 scans, Happ-Genzel apodization, 25 μm aperture, T2SL detector

Raman analysis

• Instrument: IRXross and AIRsight microscope with Raman unit
• Excitation wavelength 785 nm to reduce fluorescence from UV-degraded plastics
• 100× objective lens, 5 s exposure, 40 accumulations, CCD detector

Length measurement

• AMsolution software feature allows users to mark endpoints on wide-field or objective images for direct size determination

Main results and discussion

Infrared spectroscopy identified a 97 μm particle as polypropylene by matching its spectrum to a UV-irradiated PP reference, with minimal filter interference outside 1200 cm-1.

Micro-Raman spectroscopy at 785 nm characterized smaller particles: a 10 μm particle as polyethylene and a 5 μm particle as polystyrene based on Raman band patterns.

Simultaneous use of both techniques on the same stage eliminated sample handling errors and improved throughput. The length measurement tool provided reliable particle size data in conjunction with material information.

Benefits and practical applications

By integrating infrared and Raman capabilities on one platform, AIRsight reduces analysis time and avoids sample relocation. The combined approach covers a wide size range, detecting particles down to 5 μm with material specificity. The length measurement function adds quantitative size data, supporting environmental monitoring and regulatory compliance.

Future trends and applications

Advances in spectroscopic imaging and machine learning promise automated classification of microplastic types and sizes. Future instruments may incorporate higher spatial resolution optics, expanded spectral libraries for weathered polymers, and in situ monitoring capabilities for real-time water quality assessment.

Conclusion

The AIRsight infrared/Raman microscope offers a versatile solution for comprehensive microplastic analysis. It combines dual spectroscopic modes on a single stage, enabling accurate material identification of particles from 5 μm upward along with precise size measurement. This integrated workflow enhances analytical reliability for environmental research and monitoring.

References

Osawa Z Principles of Chemiluminescence Method and Applications to Polymer Degradation Material Life 3 1 32-39 1991