Microplastics on plankton samples: Multiple digestion techniques assessment based on weight, size, and FTIR...

Area of Science:

• Environmental Science
• Analytical Chemistry
• Marine Biology

Background:

• Accurate quantification of microplastics (MPs) requires effective organic matter (OM) digestion protocols.
• Existing methods may alter MP characteristics, affecting abundance and feature analysis.

Purpose of the Study:

• To assess the efficiency of 2-step (KOH and H2O2 + Fe2+) and 3-step (2-step + enzymes) digestion techniques on plankton samples.
• To evaluate the impact of different digestion conditions (duration, temperature) on MP weight, size, and polymer integrity.

Main Methods:

• Comparison of 2-step and 3-step digestion protocols.
• Variation of digestion duration and temperature.
• Analysis of MP weight, size, and polymer changes using spectroscopy.

Main Results:

• Both 2-step and 3-step techniques effectively digested OM.
• Inconsistent weight changes were observed for PET, polystyrene foam, PVC, and polycarbonate with 2-step digestion.
• Significant size changes occurred for PET at 60°C, while 40°C for 72h preserved MP size.
• Polymer fingerprints remained unaffected by all tested digestion methods.

Conclusions:

• Digestion protocols using high temperatures can damage microplastics, affecting their measured characteristics.
• Lower temperatures and longer durations are preferable for preserving MP integrity during digestion.
• Enzymatic steps can aid in preserving weathered MPs.