Abstract: A cassette for retaining molecules during electrophoresis has a housing with a lane configured therein. The lane has a first elongate edge and a second elongate edge, and an elution module is configured to be received in the late to divide the lane into a first chamber and a second chamber. A first buffer reservoir is positioned adjacent the first elongate edge, and a second buffer reservoir is positioned adjacent the second elongate edge. The first side of the elution module facing the first chamber comprises a porous sterile filtration membrane. The second side of the elution module facing the second chamber comprises an ultrafiltration membrane that has a pore size to retain molecules during electrophoresis.