What characteristics should the filter membrane used to filter pharmaceutical liquids have?

Membranes used to filter pharmaceutical solutions require specific characteristics to ensure effective and safe filtration. The following is an analysis of the main characteristics of membranes suitable for filtration of pharmaceutical solutions from several aspects.

1. Pore size of the filter membrane. The filter membrane should have a precise and controlled pore size in order to remove particles, bacteria and other contaminants while retaining the desired medicinal ingredients. The pore size should be small enough to prevent unwanted particles from passing through, but It should be large enough to allow target molecules to pass through. The pore size of the filter membrane is usually specified by the nominal or absolute rating. The nominal grade of the filter membrane refers to the average pore size or the size that can intercept particles with a certain efficiency. For example, the nominal accuracy is A 0.2 micron (μm) filter is designed to retain most particles larger than 0.2 µm, but smaller particles may still pass through to some extent; whereas a filter with an absolute rating indicates that it can efficiently retain particles of a specified size. For example, a filter membrane with an absolute precision of 0.2 µm can effectively intercept particles greater than or equal to 0.2 µm, with a very high efficiency, usually exceeding 99.9%.

2. Sterility performance. The membrane used for pharmaceutical filtration must be able to provide sterile filtration, effectively remove microorganisms and ensure the sterility of the filtered solution. In the process of membrane production, starting from the raw materials, that is, with extremely strict sterility Conduct production in a controlled manner with high-efficiency particulate air (HEPA) filters to minimize the presence of airborne particles and microorganisms in a clean environment; use appropriate disinfectants or sterilants to disinfect equipment, tools, and surfaces before manufacturing begins Any components or auxiliary materials in contact with the filter membrane (such as housings or support structures) are thoroughly sterilized to eliminate any potential sources of contamination; all raw materials are sterilized using methods including radiation, autoclaving, or chemical sterilization agents; Autoclaving or sterilizing agent sterilization during film formation, as well as packaging under aseptic conditions, etc., the entire production system is completed in the process of asepsis and sterilization, coupled with regular environmental monitoring, raw materials Microbiological testing, process testing and final product sterility testing are all available to ensure safe and sterile membrane products.

3. Chemical compatibility. The membrane should be chemically compatible with the drug solution and not introduce any leachables or extractables that may contaminate the solution or interact with its components. The pH value of the drug solution will vary depending on the specific formulation and intended use. The pH of pharmaceutical solutions ranges from acidic to alkaline, with eye drops and nasal sprays typically having a slightly acidic pH of 4 to 7, and oral and injectable solutions having a broader pH of 2 to 8. The range of injectable solutions, including intravenous (IV) solutions and parenteral solutions, is a neutral pH range of approximately 7. Therefore, the chemical properties of the filtration membrane must match the chemical liquid. Different membranes have different tolerances to the pH value. For example, the tolerance range of cellulose membranes is usually about 3 to 9, and the tolerance range of polymer membranes is about 3 to 9. Such as polyethersulfone (PES), polytetrafluoroethylene (PTFE), polypropylene (PP) and polyvinylidene fluoride (PVDF), which can usually tolerate a pH value of 1 to 14, covering a wide range of acidic and alkaline condition.

4. Low protein binding, surface charge and hydrophilicity, the charged membrane surface helps repel particles and improve filtration efficiency, while the hydrophilicity promotes wetting of the membrane, ensuring efficient liquid flow and minimizing clogging, Low protein binding minimizes the adsorption of proteins or other biomolecules on the membrane surface, helping to maintain the integrity and activity of drug molecules.

5. Other characteristics such as mechanical strength, biocompatibility, cleanability and reusability, high flow rate, etc. are also important factors for filter membranes in medicinal liquid filtration.

The selection of filter membrane materials depends on specific filtration requirements, compatibility with pharmaceutical solutions, industry standards and regulations, and expected results of the filtration process. The points analyzed above should be the basic requirements for filtration of pharmaceutical solutions. Hope it can be of reference to everyone.