Abstract: A device (100) having a proximal end (20) and end a distal end (40) for withdrawal of a liquid sample, fractionation, and separation of one or more fractions comprising: a piston assembly (300) comprising a piston (302) dismountably attached at its proximal end (20) to an actuating rod (350); a container (200) having a body (202) disposed with a cylindrical chamber (204) for slidable movement of the piston (302) therein; wherein the cylindrical chamber (204) is provided at the distal end (40) with a resealable septum (410) for co-operation with a puncture needle assembly (600) for withdrawal of the liquid sample, an at the proximal end (20) with a stop member (206), which stop member (206) limits movement of the piston (300) in a proximal direction, wherein the container body (202) is dimensioned to fit inside a centrifuge rotor, and is configured for breakability into two parts at a temperature of 0 deg C. or lower at a breakable zone (210).