Abstract: A filter device or apparatus is provided for the separation of materials, especially biomaterials from a fluid sample, under a force such as centrifugation, positive pressure, vacuum, or gravity. The device comprises two or more in-line tubular elements, one or more of which is a module that houses a filter media. The elements have complementary connection structures (e.g., elastomeric seal, O-ring, threads, Luer fittings, compression fittings, bayonet fittings, snap fittings, and the like) such that they can be assembled or reassembled in a train to form a conduit structure for leak-proof passage of a fluid sample volume. The assembly can be disassembled for collection and processing of retentate and filtrate material resulting from the filtration.