Pharmaceutical Filtration Integrity Testing of Sterilising–Grade Filters

Author / Editor: DR. JENS MEYER / Dominik Stephan

Filtration – often a necessary step in pharmaceutical processes: Filters keep products reliably on highest safety standards. But who watches the watchmen? Now Sartorius Stedim Biotech has developed new solutions for the testing of sterilizing grade filters...

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Sartocheck filter integrity testing for highest demands
Sartocheck filter integrity testing for highest demands
(Picture: Sartorius Stedim Biotech)

In the manufacturing of pharmaceuticals, problems encountered during integrity testing of sterilising-grade filters can substantially delay or even entirely prevent a production lot from being released on the market and result in considerable financial damages. Accordingly, the smooth progress of this critical process step to maintain a sterile barrier will gain exceptionally high economic significance.

The use of an integrity test unit over many years requires the highest possible cleanliness during operation of this device in order to prevent it from becoming contaminated. Under specific conditions, the connection between the interior of the integrity test unit and the filter cartridge housing may cause water or even the product or aerosols to flow back through the tubing into the test unit. This article describes the measures that will lead to a substantial increase in safety and reliability during integrity testing.


Preventing Contamination of the Integrity Test Unit

The interior of the test units are not sterile as a rule, and, in certain applications, particles or other contaminants inside the units can penetrate as far as into a filter cartridge housing during testing. Although an integrity test is performed on the non-sterile or upstream side, of the filter, such contamination must be reliably prevented in order to avoid compromising safety during manufacture.

There are two possibilities, in particular, for ensuring that cross-contamination is prevented: Use of a hydrophobic protective filter in the test line. To ensure bidirectional protection, i.e., between the test unit and the filter cartridge, an additional sterile vent filter can be installed directly in the test line between the integrity tester and the filter cartridge housing.

Safety Down to the Last Pore

Such vent filters feature a 0.2 μm sterilsing- grade membrane filter. This means that the test gas is automatically sterile after passing through the filter, which reliability retains particles as well. Another feature is that hydrophobic materials, such as PTFE, are used for these filters. This not only constitutes a sterile barrier, but also at the same time provides reliable protection against the passage of aqueous liquids.