Microplastic in marine environment: reworking and optimisation of two analytical protocols for the extraction of microplastics from sediments and oysters.

Marine sediments and sessile biota (i.e. oysters) are nowadays recognised to be affected by microplastic (MP) pollution. NOAA proposes two distinct MP extraction protocols for sandy and bed sediments, which, however, were already demonstrated to suffer from many limitations. Conversely, to what concern oysters, works already published are usually time consuming, requiring a KOH 24-48 h oxidation step. The aim of this study is to show how iterative adaptation of the NOAA protocol allows to extract MPs, included PET, from marine sediments, regardless their characteristics. The method tested on PE-LD/PET/PA/PE-HD is based on density separation and oxidation treatments which were both carefully tuned, obtaining final recoveries higher than 85% for all the micropolymers (100% for PE and PA). Furthermore, a new protocol for the extraction of MPs from oysters was assessed, highlighting its efficacy (recoveries higher than 84% for all the plastics) and time-saving peculiarity. Finally, both protocols were successfully applied in the MPs extraction from real samples from Atlantic Ocean.•The extraction of PE-LD/PET/PA/PE-HD was optimised in sediments (regardless their characteristics) and oysters.•For sediments, density separation and oxidation procedures were carefully optimised.•For oysters, oxidation times were reduced from 24 to 48 h to 1 h.