Evaluation of the Munich Plastic Sediment Separator efficiency in extraction of microplastics from natural marine bottom sediments

The Munich Plastic Sediment Separator (MPSS), proposed by Imhof et al. (2012), showed its high efficiency in extracting microplastics (MPs) from natural sediment samples preliminarily cleaned and then enriched by MPs in laboratory. We tested the efficiency of the MPSS, assembled at the Atlantic Branch of P.P.Shirshov Institute of Oceanology (Kaliningrad), using unprepared natural bottom deposits of different types collected in the Baltic Sea. The tests that were performed included spikes of sediments with artificial reference particles (ARPs) and the sediment samples analyses with two separate methods of extraction and determination of MPs content in residuals of MPSS. While the ARP extraction efficiency from natural sediments by the MPSS was really high (97.1% +/- 2.6%; p = 0.05; n = 14; confidence interval, t-distribution), the extraction efficiency of marine MPs was considerably lower (13-39%) than that obtained with a modification of the method previously published by NOAA. The remaining marine MPs were found in the spoil dump and in the bulk solution fractions of the separator, indicating that MPs were not perfectly cleaned from sediment particles, probably, due to presence of organic matter. It is concluded that the MPSS application for quantitative MPs analysis requires further testing and elaboration of standardized extraction procedures.