Plastic debris is constantly accumulating in aquatic environments. A first important step to assess the consequences of plastic debris in aquatic ecosystems is the establishment of a reliable, verified, and standardized method to quantify the amount of plastic particles in the environment.

We improved the density separation approach by the construction of the MicroPlastic Sediment Separator (MPSS). It enables a reliable separation of different ecologically relevant size classes of plastic particles from sediment samples. A high dense separation fluid allows for an extraction of plastic particles ranging from large fragments (L-MPP) to small microplastic particles (S-MPP). Identification and quantification of the particles with spatial resolution down to 1μm can be performed using Raman microspectroscopy.

Our study is the first providing validated recovery rates of 100% for large microplastic particles L-MPP and 95.5% for S-MPP. The recovery rate for S-MPP, using the MPSS, was significantly higher than the value obtained by application of classical density separation setup (39.8%). Moreover, our recovery rates were significantly higher than those based on froth flotation (55.0% for L-MPP) commonly used in recycling industries.

Hence, our improved method can be used for a reliable and time-efficient separation, identification and quantification of plastic fragments down to S-MPP.