Operation Precautions of Microporous Membrane Filter

Microporous membrane filter operations include dead-end filtration (vertical flow filtration) and cross-flow filtration (tangential flow filtration). But no matter what kind of operation, there are precautions:

1. Proper Handling:

Handle membrane filters with clean hands or use gloves to prevent the introduction of contaminants. Avoid touching the membrane surface, especially for filters used in sterile applications.

2. Use Appropriate Filter Size:

Choose the filter size that corresponds to the filtration apparatus. Using an improperly sized filter may lead to leaks, improper sealing, or ineffective filtration.

3. Wet the Membrane Before Use:

Wetting the membrane with a small amount of the filtrate or a compatible solvent before filtration helps to eliminate air bubbles and enhances the wetting of the membrane surface.

4. Pre-Filtration:

For samples with high particulate matter, consider using a pre-filter with a larger pore size before the microporous membrane filter. This helps prevent clogging and extends the life of the membrane.

5. Ensure Proper Sealing:

Ensure that the filter is properly seated and sealed in the filtration apparatus to prevent bypass of the sample. An improper seal can lead to inaccurate results.

6. Compatible Filtration Apparatus:

Use filtration apparatus and holders that are compatible with the membrane filter. Follow the manufacturer’s recommendations for the appropriate setup.

7. Optimal Filtration Rate:

Control the filtration rate to optimize efficiency. Too high a filtration rate can lead to premature clogging, while too low a rate may be inefficient. Follow the manufacturer’s guidelines for recommended filtration rates.

8. Pressure Considerations:

If using a pressure-driven filtration system, ensure that the pressure is within the recommended range to avoid damaging the membrane. Excessive pressure can lead to membrane rupture.

9. Change Filters Regularly:

Change the membrane filter regularly, especially if using it for critical applications like sterilization. Membranes can become clogged over time, impacting filtration efficiency.

10. Use Membranes with Correct Pore Size:

Choose a membrane with the appropriate pore size for your application. Using a pore size that is too small may result in slow filtration, while a pore size that is too large may allow unwanted particles to pass through.

11. Avoid Membrane Drying:

Avoid allowing the membrane to dry out during filtration. Drying can lead to changes in membrane properties and may affect filtration performance.

12. Sterility Maintenance:

If using membranes for sterile filtration, maintain aseptic techniques to avoid introducing contaminants. Sterilize the filtration apparatus before use and handle membranes in a clean environment.

13. Quality Control Checks:

Perform quality control checks to ensure the integrity and efficiency of the membrane filter. This may include bubble point testing or other methods recommended by the manufacturer.

14. Used for the determination of the bubble point
The determination of the bubble point pressure can reflect the pore size of the microporous filter membrane, which is closely related to the quality of the filtered liquid and is also an important means to ensure the quality of the microporous filter membrane.

Microporous membrane filter used should be soaked in water for injection at about 70℃ for 1 h in advance. Pour out the water and soak in warm water for injection overnight. Take it out before use, rinse it with water for injection, then put it into the filter for use. Prevent the filter membrane from leaking when installed.

15. Service life extension
In order to protect and extend the service life of filter membrane, filter paper or silk cloth of the same size can be used (the silk cloth should be boiled with a mass concentration of 20 g·L-1 sodium sulfonate solution for about 30 minutes, and then washed with water for injection). Put it on the filter membrane to prevent it from breaking.

16. Pore size
The pore size is cone-shaped. There is a small pore size at the smooth and front side; the rough side has a larger pore size than the back side.

When installing, the front side (smooth side) should face up and the back side (dark side) down, otherwise it is easy to be blocked by impurities and affect the filtration rate.

When the temperature is low, the treated filter membrane should be soaked in water for injection at the same temperature as the drug solution for 5 to 10 minutes to avoid rupture caused by the drop in tensile strength of the filter membrane due to temperature differences.

17. Sterilization
Ensure that the membrane filters are properly sterilized before use in applications requiring sterility. Autoclaving or other suitable methods should be employed.

18. Handling
Always handle membrane filters with clean hands, or wear suitable gloves to prevent contamination. Avoid touching the membrane surface as much as possible.

19. Storage
Store membrane filters in a clean and dry environment, away from direct sunlight, excessive heat, and humidity. Follow the manufacturer’s recommendations for storage conditions.

20. Pre-Wetting
Depending on the application, pre-wetting the membrane with a small volume of the intended liquid (such as the sample to be filtered) can help improve filtration efficiency.

21. Chemical Compatibility
Verify the compatibility of the membrane material with the sample and any chemicals used in the filtration process to prevent chemical damage or degradation.

22. Fix an infusion needle on the skin tube head of the exhaust pipe of the filter holder and control it with a water stop clip to prevent the exhaust pressure and speed from rupturing the filter membrane.

23. Do not sterilize the filter holder together with the filter membrane, otherwise the filter membrane may become brittle and crease due to thermal expansion and contraction.

24. After use, put the microporous filter membrane in water for injection to prevent it from drying, but do not soak for too long. It cannot be used after being dehydrated and dried.

25. According to the concentration and viscosity of the liquid medicine, microporous membrane filters with different pore sizes should be selected.

26. If you find that the microporous filter membrane has small holes or small cracks, you can rinse it with the unused broken filter membrane and dry it, then tear it up and place it in a small cup of acetone, stir it into a paste-like mucus. Drop it on the small holes or cracks of the flat filter membrane. It should not be too much. The mucus should be covered by a little larger one. After it dries, you can continue to use it without affecting it.

27. When using a multi-stage filtration device with coarse filtration and then fine filtration during infusion filtration, microporous membrane filters can be used for the final fine filtration, and pressure, decompression, and azimuthal static pressure filtration methods should be used.