Solving Our Plastic Problem: Advances in Microplastics Analysis

Importance of the Topic

Microplastic pollution has emerged as a global environmental and health concern due to the persistence of plastic in ecosystems and its breakdown into particles ranging from millimeters to nanometers. Reliable detection and quantification of micro- and nanoplastics are essential to assess their distribution in water, soil, air, biota, and consumer products, and to support regulatory efforts and risk assessments.

Objectives and Study Overview

This white paper reviews advances in microplastics analysis, covering the sources of particles, current analytical challenges, regulatory standardization initiatives, and key instrumental techniques. It highlights innovations by Agilent Technologies in microplastic characterization workflows, from sample preparation through high-throughput laser-based infrared imaging.

Methodology and Instrumentation

Analytical pathways for microplastics combine spectroscopic and thermal techniques:

• FTIR microscopy (single-point and FPA imaging)—mature technology with extensive spectral libraries but limited throughput and spatial resolution (≈30–50 µm).
• Raman microscopy—enables detection down to 1 µm but may suffer from fluorescence and sample damage.
• Laser Direct Infrared (LDIR) imaging (Agilent 8700)—uses a quantum cascade laser for fast area scanning and particle-by-particle spectra acquisition, detecting particles ≥10 µm without liquid-nitrogen cooling.
• Pyrolysis-GC-MS and Thermal Extraction Desorption GC-MS—provide total mass and additive identification but are destructive and lack particle-level information.

Sample preparation generally involves digestion of organic matter, density separation, filtration onto gold-coated polycarbonate filters (0.8 µm pores), and direct on-filter analysis to minimize particle loss and contamination.

Key Results and Discussion

On-filter LDIR analysis of PET bottle fragments and environmental samples demonstrated:

• High identification accuracy (>98 % correct polymer ID), even for particles down to 10 µm.
• Rapid throughput: ≈8–10 s per particle, whole-filter scans in <20 min.
• Excellent repeatability (<1 % variation in particle counts across multiple runs).
• Quantitative detection of 13 particles per liter in bottled water (mean size 77 µm) and 100 % recovery in groundwater samples (mean size 89 µm), with polymer distributions correlating to local sources.

Lack of standardized methods and interlaboratory comparisons remains a challenge. ISO and CEN are finalizing standards (ISO 24187, ISO 16094-1/-2/-3) for sampling and spectroscopic analysis of microplastics in water.

Benefits and Practical Applications

LDIR workflows deliver fully automated analysis with minimal operator intervention, high confidence in polymer identification, and broad applicability across matrices (water, sediments, biota, food). Direct-on-filter protocols reduce sample handling and contamination risks, enabling routine monitoring and data comparability.

Future Trends and Potential Uses

Emerging directions include portable QCL-based instruments for field monitoring, expansion of spectral libraries to include weathered and nanoplastic spectra, integration of machine-learning algorithms for faster particle classification, and development of standardized reference materials and proficiency tests for global method harmonization.

Conclusion

Advances in laser-based infrared chemical imaging, exemplified by the Agilent 8700 LDIR system, have revolutionized microplastics analysis by combining speed, sensitivity, and automation. Continued standardization efforts and methodological improvements will support large-scale environmental surveys and regulatory compliance.

Instrumentation Used

• Agilent 8700 Laser Direct Infrared (LDIR) Chemical Imaging System
• FTIR microscopes (single-point & focal plane array)
• Raman microscopes
• Pyrolysis-GC-MS & Thermal Extraction Desorption GC-MS
• Gold-coated 0.8 µm polycarbonate membrane filters

Reference

1. National Geographic. The World’s Plastic Pollution Crisis Explained. 2019.
2. Frias, J. P. G. L.; Nash, R. Marine Pollution Bulletin 2019, 138, 145–147.
3. National Ocean Service. What Are Microplastics? 2019.
4. Plastic Oceans. The Facts. 2019.
5. Gagné, F. Journal of Xenobiotics 2019, 9(1), 8147.
6. Agilent Technologies. Agilent Spectroscopy Product Named a “Top Innovation.” 2019.
7. Agilent Technologies. Analysis of Microplastics using FTIR Imaging. 2024.
8. Wiley Analytical Science. Polymer Analysis and Microplastics in the Environment. 2024.