High-Throughput and Direct Microplastic Analysis via Flow Raman Spectroscopy.

Raman spectroscopy has become a widely applied and powerful analytical tool across numerous scientific disciplines due to its ability to provide detailed molecular information in a non-destructive manner. In environmental sciences, it is particularly employed for the detection and analysis of hazardous chemicals as well as for the detection and identification of micro- and nanoplastics. However, the latter remains time-consuming and labor-intensive, as extensive sample preparation is typically required prior to Raman measurements. Moreover, Raman measurements are generally performed under static conditions, which further limits throughput and applicability. In this work, we present a flow Raman spectroscopy platform combined with a dedicated evaluation procedure, specifically addressing the detection of microplastics in water samples. The approach enables semi-continuous measurements with only minimal sample preparation, thereby significantly reducing the analytical effort. We showcase the accurate quantification of particle ratios and concentrations in mixed suspensions, the ability to distinguish between polymer types, and the detection of particles with diameters as small as 2 μm. Furthermore, under optimized flow conditions, the system achieves measurement rates of up to 1500 particles per minute and a detection efficiency exceeding 85%. Lastly, we successfully employ the system to detect, identify, and image microplastics in a water sample from a wastewater treatment plant. Our results underscore the potential of flow Raman spectroscopy as a powerful tool for more efficient monitoring of microplastics in environmental applications.