Chemical compatibility testing is used to evaluate the chemical impact of the fluid to be filtered on the filtration device under specific process conditions, in order to prevent potential damage or alteration of the filter and avoid contamination of the feed solution by leachables or particulates. Broadly speaking, consideration must be given not only to the impact of the fluid on filter performance but also to whether the filter might contaminate the product, for example, through leachables or particulate matter. Leachables are typically investigated and confirmed during “Extractables & Leachables Assessment and Verification.” In pharmaceutical processes, “chemical compatibility” generally refers to the impact of the fluid on filter performance, which is the “chemical compatibility” discussed in this article.
Given the numerous potential chemical interactions between filtration device components and the fluid to be filtered, general chemical compatibility data provided by filter manufacturers can typically serve as a basis and foundation for further testing. Filter users should conduct supplementary studies based on their specific processes. Common chemical compatibility tests may include integrity, tensile strength, non-volatile residue (NVR), extractables, particulates, flow rate, optical microscopy or scanning electron microscopy (SEM), burst pressure, and membrane/O-ring thickness. A combination of multiple testing methods is recommended, as a single test may fail to detect subtle incompatibilities.
However, it should also be noted that many of the aforementioned test methods lack validated acceptance criteria. Therefore, compatibility testing usually serves only as a supplementary basis for validation. Whether a filter is suitable for specific products and process conditions should still be evaluated and confirmed in conjunction with other validation items.
It is worth noting that the integrity of the filter membrane alone does not represent the integrity of the entire filter. Seams between membranes and weld seals connecting membranes to hardware can also affect filter integrity. Additionally, other components of the filter, such as the support layer, housing, and O-rings, may also present compatibility issues with the fluid to be filtered. Therefore, chemical compatibility testing should generally cover the entire filtration assembly, not just the filter membrane.
Furthermore, to adequately reflect worst-case conditions, the parameter settings for compatibility validation should, in principle, exceed the process temperature, and the duration should be longer than the actual contact time (which includes both the actual filtration time and any potential priming or setup time).