Abstract: A centrifugal filtering device including a filter unit comprising an open-ended sample tube; a filter support element, with a central open-ended passage, ultrasonically welded to the outlet end of the sample tube at an annular joint and having a seat at its outer end; and a filter clamped between the sample tube and the support element, through which liquid is forced from the sample tube when the device is centrifuged. The complete device also includes a receiving vessel, for collecting filtered liquid, removably mounted on the support element seat, and a cap for the inlet end of the sample tube. The annular weld joint is made relatively weak to enable separation of the support element and sample tube for recovery of the filter. The sample tube, support element and receiver vessel are made of polypropylene.