The presence of microplastics in the marine environment has raised scientific interest during the last
decade. Several organisms can ingest microplastics with potentially adverse effects on the digestive tract,
respiratory system and locomotory appendages. However, a clear evidence of tissue accumulation and
transfer of such microparticles in wild organisms is still lacking, partially hampered by technical diffi-
culties in isolation and characterization protocols from biological samples. In this work, we compared the
efficacy of some existing approaches and we optimized a new protocol allowing an extraction yield of
microplastics from fish tissues ranging between 78% and 98%, depending on the polymer size. FT-IR
analyses confirmed that the extraction procedure did not affect the particles characteristics. The
method was further validated on the fish mullet, Mugil cephalus, exposed under laboratory conditions to
polystyrene and polyethylene; the particles were isolated and quantified in stomach and liver, and their
presence in the hepatic tissue was confirmed also by histological analyses. A preliminary characterization
revealed the presence and distribution of microplastics in various fish species collected along the Adriatic
Sea. FT-IR analyses indicated polyethylene as the predominant polymer (65%) in the stomach of fish. The
overall results confirmed the newly developed method as a reliable approach to detect and quantify
microplastics in the marine biota.