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Quantification of small (1-10 µm) microplastic particles in soil matrices using automated scanning electron

Ralf Kaegi1, Matthias Philipp2, Isabel S Jüngling3

  • 1Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, CH-8600, Dübendorf, Switzerland. ralf.kaegi@eawag.ch.

Analytical and Bioanalytical Chemistry
|October 14, 2025
PubMed

Insights

This study introduces a gold coating for polycarbonate membranes to improve microplastic particle detection using scanning electron microscopy. This method enhances elemental contrast, enabling more accurate identification of microplastics in complex environmental samples.

Area of Science:

  • Environmental Science
  • Analytical Chemistry
  • Materials Science

Background:

  • Scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis is crucial for microplastic particle (MP) identification.
  • Polycarbonate (PC) membranes used for MP isolation offer poor elemental contrast with MPs, hindering automated detection.
  • A novel approach is needed to enhance contrast for accurate MP analysis in complex matrices.

Purpose of the Study:

  • To develop and optimize a method for improving microplastic particle detection using SEM-EDX.
  • To introduce elemental contrast between microplastic particles and polycarbonate membranes.
  • To validate the method's effectiveness in complex environmental samples like soil.

Main Methods:

  • Application of a gold (Au) coating to PC membranes to enhance elemental contrast.
  • Optimization of SEM operational conditions (3 kV acceleration voltage, 40 nm Au coating) using Monte Carlo simulations.
  • Density separation techniques to isolate MPs from soil suspensions.
  • Comparison of SEM-EDX results with Raman spectroscopy for MP identification.

Main Results:

  • A 40 nm gold coating on PC membranes at 3 kV acceleration voltage was identified as optimal for elemental contrast.
  • Recoveries of polyethylene (PE) and polyvinyl chloride (PVC) particles from soil suspensions were approximately 70% and 50%, respectively.
  • High agreement was observed between SEM-EDX and Raman measurements for microplastic identification.
  • Minimal cross-contamination was detected between PE and PVC in stock suspensions and soil samples.

Conclusions:

  • Gold-coated polycarbonate membranes significantly improve microplastic particle detection via SEM-EDX.
  • The developed method is effective for analyzing small microplastic particles in complex environmental matrices.
  • This technique offers a robust approach for accurate microplastic quantification and characterization.
Keywords:
Automated electron microscopyMicroplasticsMonte Carlo simulationSample preparationSingle particle analysis

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