These disposable ultrafiltration units are designed for ease in concentrating, separating, or otherwise purifying small volumes (<2 mL) of liquid samples, on the basis of molecular weight cutoff using positive pressure. The unit is constructed of polypropylene cap, acrylic retentive cell, and filtrate cell. Filter media is polysulfone. To use, simply dispense sample into the retentive cell by pipette, place cap on retentive cell, and inject 10 mL of air with a syringe. Remove cap to stop filtration. Sterilization: 25% ethanol, 5% formalin.