Exploring Nile Red staining as an analytical tool for surface-oxidized microplastics

Area of Science:

• Environmental Science
• Analytical Chemistry
• Materials Science

Background:

• Microplastics (MPs) pose potential health risks due to their diverse physicochemical properties.
• Surface oxidation is a key property influencing MP behavior and detection.
• Nile Red is a common stain for MP detection, but its efficacy on oxidized MPs is uncertain.

Purpose of the Study:

• To evaluate the effectiveness of Nile Red staining on surface-oxidized microplastics.
• To correlate Nile Red fluorescence intensity with the degree of surface oxidation.
• To explore novel analytical methods for environmental MP investigation.

Main Methods:

• Staining of surface-oxidized polyethylene and polyvinyl chloride with Nile Red.
• Fluorescence imaging analysis to quantify staining intensity.
• Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) to determine the carbonyl index (degree of oxidation).

Main Results:

• Nile Red effectively stained both oxidized polyethylene and polyvinyl chloride.
• Fluorescence intensity varied based on hydrophobic dynamics.
• A positive correlation was observed between Nile Red fluorescence intensity and the carbonyl index.

Conclusions:

• Nile Red is a viable stain for surface-oxidized microplastics.
• Fluorescence intensity can serve as a proxy for the degree of MP surface oxidation.
• This study provides enhanced analytical approaches for environmental MP research.