Reliable Identification of Microplastics of any Dimension, on any Filter

Significance of the topic

Reliable identification of microplastics is critical due to their ubiquity in environmental waters, potential to carry pathogens and pollutants, and suspected health risks upon entering food chains and drinking water. Accurate analysis informs remediation strategies and regulatory decisions.

Objectives and Study Overview

This application note presents a workflow combining visual microscopy with ATR-FTIR to detect and identify microplastic particles down to 5 µm on any filter or matrix. Two case studies involving bottled drinking water and river sediment illustrate method performance and material assignment.

Methodology and Instrumentation

The analysis employs the fully automated LUMOS II FTIR microscope with integrated ATR objective and motorized stage. Key features include:

• ATR measurement for high-quality spectra independent of particle size, shape, or filter material
• Visual enhancements with crossed polarizers and darkfield illumination for improved particle localization
• Adjustable knife-edge apertures to isolate individual particles and avoid background interference
• Spectral libraries: specialized polymer library by Bruker and Kunststoff Institut Lüdenscheid and ATR-LIB-COMPLETE database with over 26 000 entries

Main Results and Discussion

Case Study 1 Bottled Drinking Water

• A red fiber isolated on a filter was measured with an aperture matching its dimensions. The ATR spectrum matched polyester in the polymer library, indicating contamination from manufacturing residues.
• In a second sample on a different filter, bright particles visible under an 8× objective were identified as inorganic silica, confirming non-plastic origin.

Case Study 2 River Sediment

• Sediment samples yielded thin fibers on the surface. ATR-FTIR analysis with a fitted aperture produced pristine spectra and identified the fibers as polyamide.

These examples demonstrate reliable detection, high spectral quality, and unambiguous polymer assignment on various substrates.

Benefits and Practical Applications

The presented approach offers:

• Particle detection down to 5 µm on virtually any filter or complex matrix
• Efficient sample handling with a stand-alone automated microscope
• Minimized spectral interference through targeted apertures and ATR measurement
• Broad applicability in environmental monitoring, water quality control, and research on microplastic pollution

Future Trends and Potential Applications

Advancements may include integration of machine learning for automated spectral matching, expansion of spectral databases covering emerging plastic additives, and development of field-portable ATR-FTIR systems. Coupling microscopy with hyperspectral imaging could accelerate throughput and enable in situ monitoring.

Conclusion

Bruker’s combined visual and ATR-FTIR microscopy with LUMOS II provides a robust solution for microplastic analysis across dimensions, shapes, and matrices. The method delivers high-quality spectra, precise polymer identification, and streamlined workflows that support environmental research and industrial quality assurance.

References

1. I. L. Nerland et al., Microplastics in Marine Environments Occurrence, Distribution, and Effects Norwegian Institute for Water Research 2014
2. D. Y. Feng et al., Tissue accumulation of microplastics in mice and biomarker responses suggest widespread health risks of exposure Scientific Reports 2017
3. R. Dris et al., Synthetic fibers in atmospheric fallout A source of microplastics in the environment Marine Pollution Bulletin 2016 104 290–293
4. A. P. W. Barrows et al., Marine environment microfiber contamination Global patterns and the diversity of microparticle origins Environmental Pollution 2018 237 275–284
5. G. Peng et al., Microplastics in freshwater river sediments in Shanghai China A case study of risk assessment in mega cities Environmental Pollution 2018 234 448–456
6. O. Güven et al., Microplastic litter composition of the Turkish territorial waters of the Mediterranean Sea and its occurrence in the gastrointestinal tract of fish Environmental Pollution 2017 223 286–294