Membrane Cartridges

Types include: sterilising-grade (0.22 µm) for injectable sterile filtration; bioburden reduction (0.45–1.0 µm); clarification cartridges (1–10 µm); virus-retentive filters (20 nm) for biologic viral safety; and ultrafiltration cartridges (MWCO 1–300 kDa) for protein concentration and diafiltration in biopharmaceutical downstream processing operations.

Microfiltration (0.1–10 µm) removes bacteria, yeasts, and particulates — used for bioburden reduction and sterilising filtration. Ultrafiltration (0.005–0.1 µm or MWCO in kDa) removes viruses, endotoxins, and proteins — used in downstream bioprocessing for protein concentration, diafiltration, endotoxin removal, and viral clearance applications.

The standard sterilising-grade pore size is 0.22 µm, validated using Brevundimonas diminuta at ≥10⁷ CFU/cm² per FDA guidance and PDA Technical Report No. 26. For mycoplasma removal, 0.1 µm sterilising-grade filters are used. Mandatory pre-use and post-use integrity testing must be performed and documented in the batch record.

PVDF: excellent chemical resistance, steam-sterilisable to 125°C, low protein binding — used for bioburden reduction across aqueous and organic pharmaceutical streams. PES: very low extractables, high flow, minimal protein adsorption — preferred for sterilising filtration of injectable solutions and protein-based biologics where minimising drug product interaction is critical.

Bubble point test measures pressure at which gas displaces liquid from a wetted membrane. Forward-flow diffusion test measures sub-bubble-point gas flow rate. Both tests are performed pre-use and post-use, with results compared to manufacturer-validated specifications and documented in the pharmaceutical batch manufacturing record for full traceability.

Bioburden reduction filtration uses 0.2–0.45 µm membranes to reduce microbial load in bulk solutions upstream of the final 0.22 µm sterilising filter. It prevents premature sterilising filter plugging, controls bioburden in process streams held before filtration, and reduces sterile filtration risk — especially in large-scale biopharmaceutical manufacturing operations.

Most pharmaceutical-grade cartridges used in critical applications are single-use — discarded after one batch to eliminate cross-contamination risk and cleaning validation requirements. Where reuse is practised (e.g., water purification), validated cleaning and sanitisation procedures, periodic integrity testing, and a defined maximum reuse cycle count must be documented.