Abstract: A rotor assembly for a laboratory centrifuge includes a rotor body having a loading region encircled by an annular first bearing surface. A lid is configured to be removably secured to the rotor body so as to substantially cover the loading region. The lid includes an annular second bearing surface. Disposed between the lid and the rotor body when the two are secured together is an annular sealing element. The sealing element has a substantially U-shaped transverse cross section and includes an outward facing annular base. An annular first sealing lip projects inward from the upper end of the base and is biased in sealed engagement with the second bearing surface of the lid. An annular second sealing lip projects inward from the lower end of the base and is biased in sealed engagement with second bearing surface of the rotor body. An annular collecting groove is formed on the sealing element between the first sealing lip and the second sealing lip.