ABSTRACT
Sterile filtration is one example of a process using a polymeric component for which
extractables and leachables are a concern. Ideally sterile filtration removes unwanted
particles and bacteria while allowing the formulation to remain unadulterated.
Although hundreds of liters of pharmaceutical formulation may be filtered through
just a few square meters of filtration area, the effect of leachables cannot be
underestimated due to the intimate interaction of the formulation with the polymer.
While the filtration area may be small, the surfaces that experience product contact are
several thousand times larger due to the pore structure of the polymeric filter materials.
In Figure 1, the top surface is the reported filter surface area. However, the solution
contact surface also includes the surfaces of the porous “sponge” structures within
the filter. Leachables may also come from filter housings, membrane support layers,
O-rings, or any other polymeric components of the filter. Identifying and quantifying
these contaminants can be an analytical, albeit necessary, challenge. The necessity is
more apparent in the final steps of downstream processing, where impurities may have
a greater effect on the product.
