Oct 29, 2021 · Red PTFE (Hydrophilic) Syringe Filters, 0.22 µm, 25 mm. Hydrophilic PTFE syringe filters have broad chemical compatibility and high pH resistance and are optically clear when wet with water. They are versatile filters for use with aqueous and aggressive organic solvent-based solutions and are especially ideal for HPLC sample preparation.