Exploring the potential of photoluminescence spectroscopy in combination with Nile Red staining for microplastic detection.

The significant amount of plastic litter in the form of microplastics (size <5 mm) is garnering attention owing to its potential threat to marine life. Reliable, cost- and time-efficient analysis methods for monitoring microplastic abundance globally are still missing. Several studies proposed a fast detection method by binding the solvatochromic dye Nile Red on the surface of microplastics and using fluorescence microscopy for their detection. All the staining approaches reported so far differ in terms of Nile Red concentration, solvents, and staining procedure. Here, we compare the staining protocols published prior to 2019 and propose an optimized staining protocol. Furthermore, we explore the potential of Nile Red staining in combination with photoluminescence spectroscopy to identify the polymer type and to distinguish plastics from non-plastics.