Fluorescence photobleaching of microplastics: A cautionary tale

Area of Science:

• Environmental Science
• Analytical Chemistry
• Materials Science

Background:

• Fluorescence microscopy is crucial for identifying microplastics, especially transparent and white types.
• Photobleaching, the loss of fluorescence under illumination, poses a significant challenge in microplastic analysis.
• Rapid photobleaching can reduce fluorescence intensity within experimental timeframes, affecting detection and quantification.

Purpose of the Study:

• To quantify the photobleaching rates of five common plastics under fluorescence microscopy.
• To assess the potential for fluorescence recovery in these plastics after photobleaching.
• To inform researchers about the limitations and potential compromises when using fluorescence microscopy for microplastic identification.

Main Methods:

• Investigated photobleaching rates and fluorescence recovery of five common plastic types.
• Utilized fluorescence microscopy with controlled illumination intensity.
• Measured fluorescence intensity decay over time and assessed recovery after a 3-hour period.

Main Results:

• Statistically significant differences in photobleaching rates were observed among the plastic types.
• In optimal conditions, fluorescence intensity decayed by 10% in 11 seconds and 33% in 230 seconds.
• Fluorescence recovery was minimal, with a maximum of 13% observed after 3 hours.

Conclusions:

• Photobleaching significantly diminishes fluorescence in microplastics during microscopy, even under low illumination.
• The lack of substantial fluorescence recovery compromises the integrity of samples for subsequent analyses.
• Researchers must exercise caution and consider photobleaching effects when planning and executing microplastic studies using fluorescence microscopy.