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FAQ—Solarbio Dialysis Membranes

FAQ Documentation—Common Issues with Dialysis Bags


Q01:What is the instruction manual for dialysis bags?
A01:All dialysis bags share the same instruction manual except for product code YA1051.

Q02:What is the instruction manual for bacterial strains?
A02:All bacterial strains under the LA series share the same instruction manual.

Q03:What is the instruction manual for dextran gels? (Product codes: S8121, S8131, S8141, S8151, S8161, S8171, S9191, S9160)
A03:They all have the same instruction manual.

Q04:What is the material of dialysis bags?
A04:Cellulose ester (CE) and regenerated cellulose (RC).

Q05:Where do dialysis bags originate from?
A05:They are imported from the United States.

Q06:How are dialysis bags classified, and what are the specific differences?
A06:They are classified into regular dry type and ready-to-use type.
Ready-to-use: Free from heavy metal contamination and sulfides, requiring no pretreatment and only rinsing with deionized water before use.
Regular dry type: Coated with glycerin, requiring pretreatment before use. Refer to the instruction manual for specific treatment methods.

Q07:How should dialysis bags be stored?
A07:Dry dialysis bags should be stored in polyethylene bags at room temperature or 4°C. Unopened bags should be stored at 4°C. Once wet, dialysis bags should be immersed in one of the following solutions: 0.05% sodium azide, 1% sodium benzoate, or 1% formaldehyde.

Q08:What is the shelf life of dialysis bags?
A08:Under proper storage conditions, the shelf life is two years.

Q09:How do I choose a dialysis bag based on the molecular weight cutoff (MWCO)?
A09:The permeability of solutes depends on molecular shape, hydration, ionic charge, polarity, etc. It is recommended to choose an MWCO value approximately half of the molecular weight of the macromolecule to be retained, achieving at least a 90% retention rate.

Q10:Can dialysis bags be used for protein separation?
A10:For fine purification, chromatography or other methods are recommended.

Q11:What dialysis buffers are suitable for dialysis bags?
A11:Biotech RC Membrane: Made through a regeneration process, it exhibits improved physical resistance and chemical compatibility, offering high purity and uniform MWCO similar to biotech CE membranes. It is compatible with high concentrations of weak acids/bases, low concentrations of strong acids/bases, most alcohols, and some mild or low-concentration organic solvents. Direct contact with strong polar solvents or organic solvents damages the RC membrane. It can be used in pH 2-12 and at 4-60°C.
Biotech CE Membrane: Biologically inert and ultrapure, used for the separation of charged molecules and purification of macromolecules. It has higher requirements for conditions and solvents. CE membranes are resistant to weak or diluted acid/base solutions and slight ethanol, with only minor changes in MWCO. Direct contact with organic solvents damages the CE membrane. It can be used in pH 2-9 and at 4-37°C.Compatible solvents include CaCl2, (NH4)2SO4, isopropanol, ethanol, and acetone. Incompatible solvents include nitric acid and DMF. Testing with other reagents is recommended based on actual conditions.

Q12:Regarding ready-to-use dialysis bags: The 1000D is whiter and softer, while the 5000D is yellowish and harder. When clamped with a dialysis bag clip, the 5000D is brittle and prone to breakage, making it unusable.
A12:Different dialysis bag models exhibit variations in color and hardness, which is normal. The 5000D dialysis bag inherently possesses these characteristics. Typically, using a clamp should not cause breakage.

Q13:Does a crease affect the usage of dialysis bags?
A13:As long as the dialysis bag is intact and does not leak, it will not affect the dialysis effect.

Q14:Are there differences in the transparency and stiffness of dialysis bags?
A14:Dialysis bags made of CE material exhibit a harder, polymeric molecular lattice structure, whereas those made of RC material are relatively softer. The harder, porous structure tends to be less transparent, and generally, the larger the pore size, the poorer the transparency. Both CE and RS dialysis bags can only be sealed mechanically and cannot be heat-sealed or chemically sealed.

Q15:Can they be reused?
A15:Reuse is not recommended due to potential cross-contamination, changes in the membrane properties caused by altered dialysis environments, and the risk of damage or leakage.

Q16:How do I choose a dialysis bag clip, and can it be replaced with a rope?
A16:The sealing width of a dialysis bag clip is typically 4-10 mm longer than the flattened width of the dialysis bag. A rope should not be used as a substitute as knots can cause unpredictable damage to the dialysis bag and may not provide an effective seal, leading to leakage.

Q17:Can a dialysis bag be used after it dries out or is frozen?
A17:Once a wet dialysis bag dries out, its pore size undergoes irreversible changes, making the membrane fragile and prone to leakage. Thus, it is not recommended for further use. When a dialysis bag is frozen, ice crystals can rupture the membrane, also leading to leakage, and it should not be used.

Q18:What common household item can be compared to the shape of a dialysis bag?
A18:The shape of a dialysis bag resembles an unsealed garbage bag with open ends.

Q19:What is the recommended ratio of sample to dialysis solution volume?
A19:The volume of dialysis solution should be 100 times that of the sample volume. (For example, dialyze 10 ml of sample in 1 liter of dialysis solution.)

Q20:How long should a dialysis bag be cut?
A20:The length of the dialysis bag should be determined based on the actual sample volume, typically cut into short segments of appropriate length (10-20 cm).

Q21:Explain the product code YA1070, with dialysis bag MD10 (8000-14000)D as an example?
A21:MD10 refers to a flattened width of 10 mm. 8000-14000D indicates that molecules with a molecular weight of 8000 Daltons or higher will begin to be retained, and all molecules up to 14000 Daltons will be retained within the dialysis bag.

Q22:What is the primary purpose of an ultrafiltration tube?
A22:To concentrate biological samples containing antigens, antibodies, enzymes, nucleic acids (single- or double-stranded DNA/RNA samples), microorganisms, eluates, and purified samples.

Q23:How do I select the appropriate ultrafiltration tube?
A23:Generally, the molecular weight cut-off (MWCO) should not be more than one-third of the target protein's molecular weight. For instance, if the target protein has a molecular weight of 35 kDa, a 10 kDa MWCO ultrafiltration tube can be selected. If the target protein's molecular weight is around 10 kDa, a 3 kDa MWCO ultrafiltration tube can be used.

Q24:What chemicals is an ultrafiltration tube resistant to?
A24:It is suitable for biological liquids and aqueous samples. For specific compatibility with chemical reagents, please refer to the product manual.

Q25:What are the main components of an ultrafiltration tube?
A25:An ultrafiltration tube consists of a cap, a filter, and a centrifuge tube.

Q26:Does an ultrafiltration tube require pretreatment?
A26:Newly purchased ultrafiltration tubes are dry and contain trace amounts of glycerol. They can be pre-rinsed with buffer solution or Millipore water. If interference persists, clean with 0.1 N NaOH, followed by rinsing with buffer solution or Millipore water and spinning dry.

Q27:Can an ultrafiltration tube be reused?
A27:Yes, but typically, it is replaced after one or two uses. It should be washed first with buffer solution and then repeatedly with deionized water. If there are significant residual protein impurities, clean with 0.1 N NaOH and 0.1% SDS to remove and dissolve proteins and other impurities. Soak the ultrafiltration membrane in a sodium azide solution or 20% ethanol to prevent bacterial growth and drying. Avoid re-drying once it is wetted, as drying can affect the pore size of the membrane.
Note: Do not use ultrasonic cleaning! Ensure that the pipette tip does not touch the filter membrane during cleaning.

Q28:How do I achieve a balance between rotation speed and centrifugation?
A28:Both mass and center of gravity must be balanced. Ensure that the rotation speed and acceleration are not too fast, as this can directly damage the ultrafiltration membrane. Begin centrifugation with the centrifuge pre-cooled to 4°C. The conversion of rpm to g varies between different centrifuges. Refer to the manual in the appendix for specifics. Set the centrifuge's acceleration to the lowest setting to reduce pressure on the membrane.
Note: In practical use, it is recommended to set the rotation speed lower than that specified in the manual to extend the centrifuge tube's lifespan.

Q29:Why does clogging occur during centrifugation?
A29:If precipitation occurs, identify the cause—whether it's due to excessive protein concentration or an inappropriate buffer. If it's due to high protein concentration, use multiple ultrafiltration tubes simultaneously to reduce the concentration. If the buffer is inappropriate, replace it with a suitable one until precipitation stops.

Q30:Are ultrafiltration tubes sterile?
A30:No, they are non-sterile.

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