Quantitative assessment of visual microscopy as a tool for microplastic research: Recommendations for improving...

Area of Science:

• Environmental Science
• Analytical Chemistry
• Materials Science

Background:

• Microscopy is a primary technique for microplastic identification, providing critical data on size, shape, and color.
• Spectroscopy is typically used for material confirmation after microscopy.
• Accurate microplastic quantification is essential for environmental risk assessment and source tracking.

Purpose of the Study:

• To evaluate the accuracy and precision of microscopy in microplastic analysis.
• To identify factors influencing microplastic recovery rates and identification accuracy.
• To provide data-driven recommendations for improving microplastic microscopy methods.

Main Methods:

• A method evaluation study involving 22 laboratories across six countries.
• Participants analyzed blind spiked clean water samples containing microplastics of various types, sizes, colors, and morphologies.
• Analysis included assessment of particle recovery, identification accuracy, and influence of laboratory experience.

Main Results:

• Poor particle recovery was observed for the smallest microplastics (3-20 micrometers).
• Overall recovery for particles >50 micrometers was 51.3% ± 21.7% after quality checks.
• Recovery varied significantly by morphology (poorest for fibers) and color (largest deviations for clear/white particles).
• Less experienced laboratories showed higher concentrations and greater variance.

Conclusions:

• Microscopy's accuracy and precision are influenced by particle characteristics and laboratory expertise.
• Improvements in training, identification keys (color, morphology), and size fractionation methods are needed.
• Despite limitations, microscopy remains a valuable tool for microplastic analysis when methods are refined.