Nowadays, environmental pollution represents a global-scale problem. During the environmental degradation of plastic waste, micro- and nanosized plastic particles are formed, which pose potential health risks; at the same time, their detection and characterization constitute a significant analytical challenge.
Currently, the detection of microplastics is carried out primarily using microscopic techniques. The most commonly applied fluorescent dye, Nile Red [1], does not bind, or binds only under more intensive staining conditions, to several frequently occurring plastic types (such as PVC, PA, and PET), which makes the development of new, more efficient fluorescent labeling agents necessary.
In the present study, various solvatochromic dyes have been tested as tools for the quantification and visualization of microscopic plastic fragments. Since different plastic types possess distinct dielectric constants, these dyes may be suitable for the qualitative characterization of microplastics by exhibiting plastic-type-dependent changes in their fluorescence emission. The applicability of DANS (4-dimethylamino-4′-nitrostilbene) has already been demonstrated in the literature [2]; in our own research, we developed this approach further. Due to the apolar nature of many plastics, their dielectric constant values are relatively close to one another, resulting in significant overlap in the fluorescence emission spectra for certain plastic types (such as PE and PP). However, even in such cases, the fluorescence decay times may be significantly different, which can be exploited as a secondary selectivity parameter for qualitative discrimination. The measurement method was also extended to additional solvatochromic fluorescent probes.
[1] Shim, W. J.; Song, Y. K.; Hong, S. H.; Jang, M. Identification and Quantification of Microplastics Using Nile Red Staining. Marine Pollution Bulletin 2016, 113 (1), 469–476. https://doi.org/10.1016/j.marpolbul.2016.10.049.
[2] Sancataldo, G.; Ferrara, V.; Bonomo, F. P.; Chillura Martino, D. F.; Licciardi, M.; Pignataro, B. G.; Vetri, V. Identification of Microplastics Using 4-Dimethylamino-4′-Nitrostilbene Solvatochromic Fluorescence. Microscopy Research and Technique 2021, 84 (12), 2820–2831. https://doi.org/10.1002/jemt.23841.
