Whatman Puradisc 25 mm H-PTFE Syringe Filters 0.45 µm, Hydrophilic, 200 Pack, 6773-2504 Whatman Puradisc 25 mm H-PTFE Syringe Filters 0.45 µm, Hydrophilic, 200 Pack, 6773-2504 Whatman’s Puradisc syringe filters are made to serve a wide variety of applications including capillary electrophoresis, biological preparations, protein filtration, and UV spectroscopy sample preparation.