Comprehensive Approach for Successful Microplastics Analysis

Significance of the Topic

Microplastics are pervasive environmental pollutants requiring detailed characterization of their size distribution count shape and composition to assess ecological and human health risks

Study Objectives and Overview

This work integrates dynamic particle imaging and infrared spectroscopy techniques in accordance with ASTM standards to develop a comprehensive workflow for quantitative and qualitative analysis of microplastics in water spanning particle sizes from 5 to several hundred micrometers

Methodology and Instrumentation

• Sampling and sample preparation following ASTM D8332 D8333 and D8402 procedures to create synthetic mixtures of polypropylene polyethylene and polystyrene fragments sieved to target size fractions
• Dynamic image analysis of 5–100 μm particles using Shimadzu iSpect DIA-10 with methanol-glycerin suspension and seven replicate measurements for size distribution shape and particle count determination
• Bulk infrared identification of larger particles using Shimadzu IRTracer-100 FTIR spectrophotometer equipped with QATR 10 attenuated total reflection module under 4 cm⁻¹ resolution and 30 scans
• Microspectroscopic mapping of particles below a few hundred micrometers using Shimadzu IRXross FTIR system combined with AIMsight infrared microscope performing area scans with 50 μm apertures

Key Results and Discussion

• Dynamic imaging yielded an average concentration of 3479 particles/mL for the <100 μm fraction with RSD below 7 % overall and detailed size distribution profiles between 5 and 100 μm
• FTIR-ATR analysis identified a selection of larger particles confirming polypropylene polystyrene and polyethylene composition and provided individual spectra and length measurements
• Infrared microscopy mapping detected 3000–4000 particles per filter with chemical identification ratios demonstrating successful differentiation of PP PS and PE across multiple measurement areas

Benefits and Practical Applications

• Enables simultaneous quantitation of particle count size distribution shape and chemical composition across a broad size range
• Reduces manual sorting and handling through automated imaging and mapping workflows
• Complies with emerging ASTM standards providing a validated approach for routine environmental and quality control laboratories

Future Trends and Opportunities

Advanced automation and integration of machine learning for spectral identification development of field-portable combined imaging and spectroscopy platforms and expansion of standardized libraries and protocols to support regulatory monitoring and large scale environmental surveys

Conclusion

The combined use of dynamic particle image analysis and FTIR spectroscopy under ASTM guidelines offers a robust and comprehensive solution for microplastics analysis in water delivering precise quantitation of particle size distribution and reliable material identification from 5 μm to several hundred micrometers

References

1. Shimadzu App News GCMS-2202 An Automated Workflow for Quantitative Analysis of Microplastics in Environmental Samples via Pyrolysis-GC/MS
2. Shimadzu App News 01-00396-en Analysis of Microplastics Using AIRsight Infrared/Raman Microscope
3. WK 87463 Standard Test Method for Spectroscopic Identification and Quantification of Microplastic Particles in Water Using Infrared Spectroscopy
4. Shimadzu Whitepaper New Standard Determination of Microplastics Particle and Fiber Size Distribution Shape and Concentration in Waters with High to Low Suspended Solids Using a Dynamic Image Particle Size and Shape Analyzer September 2022 Whitepaper-STP-DIA
5. ASTM D8402 Standard Practice for Development of Microplastic Reference Samples for Calibration and Proficiency Evaluation in All Types of Water Matrices with High to Low Levels of Suspended Solids