A disposable fluid circuit for use in a centrifuge for concentrating pathogens from fluid said circuit including at least a first and second flexible plastic separation chambers adapted for cooperation with a rotatable centrifuge platform, said chambers being in series fluid flow communication in said circuit, each of said chambers having a flow path defined therein for fluid flow through the chamber, said first chamber including a flow path for removal of particles concentrated therein, and said second chamber being adapted to receive processed fluid from the first chamber and having an inlet, an outlet, and a flow path there between, said flow path being of substantially constant cross—sectional dimension between said inlet and outlet to define a substantially uniform flow field.
