What is a 0.2/0.22 µm Sterilizing Grade Filter primarily used for?

• A. Filter used for prefiltration
• B. Filter used to deionize water
• C. Filter used for gas filtration
• D. Filter to produce a sterile effluent

Answer: (D)

0.2/0.22 μm sterilizing-grade filters are chosen because their pore size is small enough to remove bacteria from liquids, making the liquid that passes through sterile. In pharmaceutical processes this final filtration step is used to ensure the effluent is sterile before it reaches the product or patient. Prefiltration uses larger pores to remove bulk particulates upstream, deionization uses ion-exchange resins to remove ions, and while filters for gas filtration exist, the typical and most direct use of these sterilizing-grade membranes is to produce a sterile liquid effluent.