Rhodamine B dye staining for visualizing microplastics in laboratory-based studies

Area of Science:

• Environmental Science
• Analytical Chemistry
• Polymer Science

Background:

• Microplastics are emerging environmental pollutants requiring effective tracking methods.
• Visualizing transparent or white microplastics in laboratory experiments is challenging.
• Accurate identification and quantification of microplastics are crucial for environmental studies.

Purpose of the Study:

• To develop and validate a simple, robust staining method for visualizing microplastics.
• To assess the effectiveness of Rhodamine B dye for microplastic labeling.
• To evaluate the stability and compatibility of the staining method under various conditions.

Main Methods:

• Staining five microplastic types (polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyurethane) with Rhodamine B.
• Investigating ethanol, acetone, and distilled water as solvents for Rhodamine B.
• Assessing Rhodamine B fluorescence stability in light, gut fluid, KOH, nitric acid, and saturated NaCl.
• Analyzing the effect of Rhodamine B staining on microplastic Raman spectra.

Main Results:

• Ethanol proved to be the most effective solvent for dissolving Rhodamine B.
• Rhodamine B staining resulted in purple/pink coloration and fluorescence under microscopy.
• The dye exhibited fluorescence stability across various tested conditions and solutions.
• Rhodamine B staining had a negligible impact on the microplastics' Raman spectra.

Conclusions:

• The Rhodamine B staining method offers a simple and robust way to visualize microplastics, particularly transparent, white, and small particles.
• This technique enhances the legibility of microplastics in laboratory experiments, aiding environmental research.
• The method's stability and minimal effect on spectral properties make it a valuable tool for microplastic analysis.