Membranes bubble-point temperature

Aseptic Lltration is necessary for parenteral formulations. Because both lipids and the structure of liposomes are unstable at high temperatures, conventional terminal steam sterilization is not suitable for liposome formulations. Thus, the membrane aseptic Lltration is the most reliable method for sterilizing liposome formulations. Since the possibility exists for the membrane being defective, it is advisable to test the integrity of the assembled unit by carrying out a bubble-point test. This test... 

In which y is the interfacial tension, 0 the contact angle, K a correction factor for the shape of the pores and d the pore diameter. Cos 0 is determined by the interfacial tensions between the three components filter membrane material, hquid and air. It is the same angle as in the wetting theory as discussed in (Sect. 18.3.2). The manufacturer supplies the value of the bubble point for hydrophilic filters for a filter moistened with purified water at a specified temperature. A different liquid or product or different temperature in the membrane results in a different interfacial tension and thus a different bubble point. 

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