The ready to use dialysis bag is usually a bag shaped container made of a semi permeable membrane. During the preparation of biological macromolecules, dialysis technology is used to remove salt, a small amount of organic solvent, biological small molecule impurities, and concentrate samples. It is a bag made of small pore materials through which water molecules pass but other macromolecules do not.

Dialysis can be completed by using a special semi permeable membrane. Generally, the semi permeable membrane is made into a bag, the biopolymer sample solution is put into the bag, and the permeable bag is immersed in water or buffer solution. The high molecular weight biomacromolecules in the sample solution are retained in the bag, and the salt and small molecular substances are continuously diffused out of the bag for dialysis until the concentration on both sides of the bag is balanced. The non dialyzed sample solution left in the dialysis bag is called "retention solution", and the solution outside the bag (membrane) is called "exudate" or "dialysate".

The driving force of dialysis is diffusion pressure, which is formed by the concentration gradient on both sides of the transmembrane. The dialysis speed is inversely proportional to the membrane thickness, is proportional to the concentration gradient of small molecular solute to be dialyzed on both sides of the membrane, and is also proportional to the membrane area and temperature, usually 4 dialysis. Increasing the temperature can accelerate the dialysis speed.

Although dialysis bag is a bag that allows water molecules made of materials with small pore size to pass through, other macromolecular substances are not allowed to pass through. Reusable, put a large amount of distilled water to rinse 3-5 times. The best preservation method is to soak in 4 ℃ distilled water (cooled by refrigerator) and re distilled water. However, we do not recommend the reuse of dialysis membranes. Because specific treatment operations may contaminate the membrane, certain dialysis conditions (pH, temperature, chemical contact, etc.) may also damage the integrity of the membrane or cause leakage. Especially when opening and clamping the membrane clamp. After all, it is only an experiment, so the results are the most important. Repeated use will lead to batch differences.

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