ABSTRACT
Membrane filters have been employed in sterile filtration processes for over 20 years. Inertial impaction refers to the deviation of a particle from its streamline during flow because of inertia, resulting in the retention of the particle by the membrane. An electrostatic attraction can exist or be induced between the membrane material and particles in the fluid stream. This attraction can enhance the removal of particles and their retention by the filter membrane. Sterilizing grade hydrophilic membrane filters require testing using a liquid bacterial suspension challenge that is sensitive enough to detect the passage of any microorganisms, for the establishment of the micron rating of the filter. Membrane filters used for sterile liquid filtration are typically constructed of hydrophilic materials, such as nylon, cellulose acetate, modified polyvinylidene difluoride, or other polymers. In order to design a sterile filtration process properly, all of the requirements for the total system must be considered.
