Analysis of Microplastics Collected from Marine Species Using the AIM-9000 Infrared Microscope

Importance of the Topic

Microplastic contamination in marine ecosystems has become a global concern, extending even to remote regions such as the Arctic Ocean. These minute particles infiltrate the food chain, impacting species from polar cod to deepwater shrimp. Reliable identification and characterization of microplastics are essential for assessing environmental risks and informing mitigation strategies.

Objectives and Study Overview

This study aimed to isolate and identify microplastic particles collected from the stomach contents of polar cod and deepwater shrimp. Researchers sought to determine polymer composition and associated additives, thereby evaluating the extent of pollution in regions assumed to be minimally affected by human activity.

Pretreatment and Sample Handling

Strict contamination controls were applied throughout sample collection and preparation:

• Use of powder-free gloves to avoid introducing sebum or dust
• Air-filtered workspace to minimize airborne fibers
• Washing samples with potassium hydroxide solution to dissolve organic matter without altering plastic polymers

Instrumentation Used

Analysis employed an IRTracer™-100 Fourier transform infrared spectrophotometer coupled with the AIM-9000 infrared microscope. Key measurement parameters included:

• Resolution: 8 cm⁻¹
• Accumulations: 100 scans for ATR measurements, 50 scans for transmission
• Apodization functions: Happ-Genzel for ATR, Square-Triangle for transmission
• Detector: Mercury-cadmium-telluride (MCT)
• Aperture sizes: 25 µm × 25 µm for ATR, 15 µm × 15 µm for transmission

Main Results and Discussion

Polar cod microplastic particles were analyzed by microscopic attenuated total reflection (ATR). Spectral matching revealed:

• Primary polymer: Polymethylmethacrylate (PMMA)
• Additive: Kaolin (aluminum silicate)

Deepwater shrimp fragments were examined using microscopic transmission in a diamond cell. Identified components included:

• Polyethylene (PE)
• Calcium carbonate (CaCO₃) filler
• Kaolin additive

These findings confirm the presence of common consumer plastics and mineral additives in marine organisms inhabiting remote depths and polar regions.

Benefits and Practical Applications of the Method

The combination of FTIR spectroscopy and infrared microscopy provides rapid, non-destructive identification of microplastics down to tens of micrometers. Advantages include:

• High spatial resolution for individual particle analysis
• Capability to detect both organic polymers and inorganic fillers
• Minimal sample preparation artifacts

This methodology supports environmental monitoring, pollution source tracing, and impact assessments in marine research and regulatory compliance.

Future Trends and Possibilities of Use

Advances anticipated in microplastic analysis include:

• Automated image-based particle recognition to increase throughput
• Enhanced spectral libraries for a broader range of polymers and additives
• Integration with complementary techniques (e.g., Raman microscopy) for more comprehensive characterization
• Miniaturized field-deployable IR systems for in-situ monitoring

Conclusion

The study demonstrates that even remote marine species harbor microplastic contamination composed of common packaging polymers and mineral additives. Infrared microscopy coupled with FTIR spectroscopy proves to be an effective tool for detailed microplastic analysis, offering critical insights for environmental pollution research.

Reference

1. Susanne Kühn et al. In every ocean, at every depth–microfibers and microplastics: Micro FTIR analysis of smallest particles from deep sea to polar ice, SHIMADZU NEWS, 2.2018.