How to Use the Filter Membrane Correctly?

How to choose a suitable filter membrane?

HAWACH is dedicated to providing professional experiment consumables, such as serological pipettes, filter paper, syringe filters, and various filter membranes. Filter membrane is one of the most frequently used consumables in lab experiments. The main function of the filter membrane is to achieve separation, purification, and purification by retaining particles, bacteria, and other impurities from the gas or liquid phase. Hawach provides Microporous Glass Fiber Membrane Filters, PVDF Membrane Filters, PES Membrane Filters, MCE Membrane Filters, and other membrane filters for your choice. The following three factors are to be considered when choosing a filter membrane:

1. The material of the filter membrane is its chemical compatibility: when selecting a filter membrane, chemical compatibility must be considered first, like whether the solvent contains acid or alkali and whether it is an organic solvent, and so on. For details, check the filter membrane chemical compatibility table by ourselves or consult the HAWACH team who will provide you with professional advice.

2. The pore size of the filter membrane: We need to determine the correct range of filter membrane pore size according to the size of the filtered molecules or particles.

3. In addition to the filter membrane, we also need to consider the characteristics of the sample:
1) If you are dealing with hydrophilic samples, use a hydrophilic membrane. The available filter membranes are mixed cellulose membranes, polyethersulfone, etc.
2) For strong corrosive organic solvents, hydrophobic membranes are generally used.
3) If it is a protein solution, we need to choose a filter with low protein adsorption, such as a PVDF filter.
4) For ion chromatography, we would recommend a PES membrane, which is more suitable for the filtration of solutions with low inorganic ions.

How to use filter membranes in the right way?

After we get the suitable filter membranes, we also need to know how to use them rightly. Here are some tips for better use of filter membranes.
1. Determination of bubble point: Determination of bubble point pressure can reflect the pore size of the filter membrane, which is related to the filter. The quality of the liquid medicine is closely related, and it is also an important means to ensure the quality of the filter membrane. The filter membrane used should be soaked in water for injection at about 70°C for 1 hour in advance. Take out the water and use warm water to soak it overnight. For temporary use, take it out and rinse it with water, then put it into a filter. Please note, do not let the filter membrane leak when installed.

2. Use same-size filter paper or silk cloth (but silk cloth needs to be boiled with a mass concentration of 20g·L-1 sodium sulfonate solution for about 30 minutes, and then washed with water for injection). Doing, it is to protect and prolongs the filter membrane service life.

3. The pore size of the microporous filter membrane is cone-shaped, the smooth side has a small pore size, and the rough side has a large pore size. Otherwise, the pore size will be easily blocked by impurities, which will affect the filtration rate. When the temperature is low, the treated filter membrane should be soaked in water for injection with the same temperature as the liquid for 5-10 minutes to avoid rupture due to the decrease of the tensile strength of the filter membrane due to the temperature difference.

4. On the leather tube head of the exhaust pipe of the filter holder, fix a 16-gauge infusion needle and control it with a water stop clip to avoid filter membrane rupture, because of the excessive speed and exhaust pressure.

5. Do not sterilize the filter frame together with the filter membrane, otherwise, the filter membrane will be brittle and wrinkled due to thermal expansion and contraction.

6. After use, put the filter membrane in water for injection to prevent drying, but do not soak it for too long, and the filter membrane that has been dehydrated and dried cannot be used.

7. Filter membranes with different pore sizes should be selected according to the concentration and viscosity of the liquid.

8. If it is found that the filter membrane has small holes or small cracks, it can be rinsed with the original broken filter membrane and dried, then shredded and placed in a small cup of acetone, stirred into a paste-like mucus, and the mucus drops. In the small holes or small cracks of the flat filter membrane, it should not be too much. It is enough to cover the mucus and make it slightly larger. After drying, you can continue to use it without affecting it.

9. When using a multi-stage filtration device with coarse filtration and then fine filtration during infusion filtration, the filter membrane can be used as the final fine filtration, and pressure, decompression, and azimuth static pressure filtration should be used.