Pharmaceutical filtration: microfiltration, ultrafiltration, nanofiltration, how to choose? What is the difference?

When choosing a filtration process, ask yourself three questions first!

What do I want to separate/remove? (Bacteria? Proteins? Pyrogens? Salts?) 2 What is the size/molecular weight of the target substance?   3. What is the purpose of the process? (Sterilization? Concentration? Purification? Desalination?)

Microfiltration, ultrafiltration, and nanofiltration are not simply sorted by size, but each have their own separation principles and objectives.

Understanding pore size, molecular weight cutoff, and application logic is the first step in ensuring efficient pharmaceutical processes and product safety!   

1. Microfiltration (MF): Coarse sieving with a pore size of 0.1 10 microns (like a fishing net). Skills: Filter out bacteria, suspended particles, and large colloids, but cannot block viruses and large molecules. Pressure: Low operating pressure, 1 3

Bar is enough.   

Pore size: 0.001 0.1 micrometers (1100 nanometers, like a fine mesh) Skill: Separation of biomolecules such as proteins, viruses, polysaccharides, etc., is the main force for concentration and purification in biopharmaceuticals. Pressure: higher than microfiltration, moderate pressure.   

Pore size: about 0.001 micrometers (1 nanometer, similar to a molecular level filter) 

Skills: capable of intercepting small organic molecules and divalent ions (such as sulfate ions and calcium magnesium ions), excellent in removing heat and desalination. 

Pressure: When choosing a filtration process with the highest operating pressure, ask yourself three questions first!

What do I want to separate/remove? (Bacteria? Proteins? Pyrogens? Salts?) 2 What is the size/molecular weight of the target substance?   3. What is the purpose of the process? (Sterilization? Concentration? Purification? Desalination?)

2、 Practical scenario microfiltration (MF): sterilization filtration of drug/buffer solutions (terminal control), air sterilization (essential for aseptic processes), and clarification of cell harvest solutions.

Ultrafiltration (UF): a crucial step in the concentration and desalination of biomolecules such as monoclonal antibodies and vaccines (by changing buffer solutions), removal of small molecule impurities (such as HCP and DNA), and virus removal/inactivation.

Nanofiltration (NF): precise removal of endotoxins, small molecule drugs, or antibiotics through concentration and purification, partial desalination, and softening (to remove calcium and magnesium ions).

1. The size of the "sieve" in a pore size membrane, measured in micrometers (μ m) or nanometers (nm), directly determines how large particles can be blocked.   

2. Definition of molecular weight cutoff (MWCO): A membrane is capable of intercepting more than 90% of the molecular weight of a specific standard substance (commonly spherical protein or PEG). 

Relationship: The smaller the pore size, the lower the molecular weight cut-off (such as ultrafiltration membranes with specifications of 1 kDa, 30 kDa, etc., while nanofiltration membranes are mostly between 100 and 1000 Da).   

be careful! The shape of molecules has a huge impact: linear molecules (such as DNA, PEG) may "drill through" membranes with lower molecular weight than the nominal cut-off; Spherical molecules (such as proteins) are more easily blocked by membranes that approach the cut-off molecular weight.   

1. Electron microscope: Scanning the surface of the membrane to obtain a pore size distribution map, the narrower the peak, the more uniform the pore size.   

2. Bubble point testing method: commonly used in production quality control, it measures the maximum pore size of the membrane - when the pressure reaches the bubble point, the first bubble to break through is the maximum pore size.