1、 Membrane technical parameters:
Biotechnology CE membrane (cellulose ester membrane), without pre-treatment before use; The content of heavy metal ions and sulfides is at the trace level, and 0.05% sodium azide anti-corrosion storage solution is used after rinsing with distilled water; Biotechnology CE membranes can only withstand neutral environments, weak acids, weak bases, or mild alcohols, and contact with strong polar organic solvents can damage the CE membrane; Biotechnology CE membranes can only be used with pH values ranging from 2 to 9 and temperatures ranging from 4 to 37 ℃. It is recommended not to use organic solvents in both the sample solution and buffer solution. When encountering organic solvents, the bag is prone to shrinkage. If you must use organic solvents, it is recommended to use a few centimeter dialysis bag for preliminary experiments first.
2、 Storage conditions:
Immerse the dialysis membrane in the storage solution and seal it in an environment between 4 and 37 ℃. It is recommended to seal and store at 4 ℃ in the refrigerator freezer.
3、 Usage of dialysis bags:
1. First, wear gloves and cut the dialysis bag into small pieces of appropriate length (about 10cm). The length can be as needed, but there must be enough containers to accommodate it.
2. Thoroughly clean the dialysis bag with distilled water, gently pinch both ends with your hands, and check for any leaking bags. The dialysis bag preservation solution contains preservatives that have an inhibitory effect on active substances. It should be rinsed repeatedly with distilled water (pure water or deionized water can be used) at least three times, and it is best to soak in distilled water for 30 minutes before use.
3. Unused dialysis membranes should be returned to the storage solution and sealed for storage. Gloves must be worn during contact with the dialysis membrane.
4. When using, clamp one end with a dialysis bag clamp, fill it with water, and apply pressure with your fingers to check for leaks. Repeat the same process on the other end to avoid insufficient tightness of the clamp. Then load the sample, usually leaving one-third to half of the space to prevent excessive water and buffer from entering the bag during dialysis and causing the bag to burst. After loading the sample, clamp the bag opening with a clamp to perform dialysis. In order to accelerate the dialysis speed, in addition to replacing the dialysis buffer multiple times, a magnetic stirrer can also be used. Dialysis containers should be larger and can be used with large beakers, large cylinders, and plastic barrels. The dialysis time can be determined based on the sample concentration, or overnight dialysis can be performed, with a recommended dialysis time of 24 to 48 hours. Hanging the dialysis bag with a wire to keep it in a suspended state can also accelerate the dialysis speed.
4、 Selection of Molecular Weight Interception (MWCO) and Width for Dialysis Bags
Selection of molecular weight for dialysis bags:
Due to the fact that dialysis membranes are composed of sponge like cross-linked polymers, the molecular weight of the membrane pore size (MWCO) is an indirect measure of membrane separation performance. More accurately, the molecular weight of the membrane can be defined as the molecular weight of the solute with a retention rate of at least 90%. Due to the fact that the permeability characteristics of solutes depend on molecular shape, hydration degree, ion charge, and polarity, we recommend choosing a dialysis bag with a molecular weight less than half of the molecular weight of the intercepted substance (smaller is better)/or more than twice the maximum molecular weight of the substance to be permeated (larger is better). In addition, the selection of molecular weight for dialysis bags should also pay attention to the following points:
The effective size of most solute molecules is influenced by the pH value and ion strength of the solution they dissolve.
When selecting the optimal MWCO for various applications, it is necessary to use multiple membranes for testing.
To maximize the dialysis rate, the membrane chosen should have the maximum MWCO and not cause significant loss of required substances.
Selection of dialysis bag width:
The choice of flat width for dialysis bags depends on the sample volume and dialysis capacity. Smaller dialysis tubes allow for faster dialysis; Larger dialysis tubes have a longer diffusion distance and slower dialysis. For ease of use, it is recommended to use a dialysis bag with a total length (including closure clips and top space) of approximately 10-15 centimeters. Simply put, the more samples to be dialyzed, the wider the dialysis bag needs to be selected, and vice versa. The relationship between the diameter and width of dialysis bags can be referred to the following figure:
The most common usage of dialysis bags:
When using, one end can be tied tightly with a rubber band or string, or a special dialysis bag clamp can be used to clamp it. The other end can be filled with water, and slightly pressurized with your fingers to check for leaks before the dialysis solution can be loaded. Usually, one-third to half of the space should be left to prevent excessive water and buffer from entering the bag and causing it to burst during the dialysis process. It is normal for a protein solution with high salt content to increase its volume by 50% when dialyzed overnight. In order to accelerate the dialysis speed, in addition to changing the dialysate multiple times, magnetic stirring can also be used. Dialysis containers should be larger and can be used with large beakers, large cylinders, and plastic barrels. For dialysis with a small volume of solution, a section of glass rod or glass tube sealed at both ends can be placed in the bag to make the dialysis bag sink below the liquid level.