Category of Membrane Filter
From the appearance point of view, the category of filter membrane can be divided into roll membrane and sheet membrane. However, when we usually choose the filter membrane, we will choose different filter materials according to different applications.
Therefore, this paper mainly classifies the filter membranes by different materials.
Different Materials Of Filter Membranes
Polyvinylidene Fluoride(PVDF)
PVDF membrane filter is hydrophobic, and the membrane pore size varies. As the membrane pore size decreases, the membrane binds to low-molecular-weight proteins more firmly. For proteins larger than 20kda, use a 0.45um membrane, and for proteins smaller than 20kda, use a 0.2um membrane.
PVDF membrane needs to be pretreated before use. The purpose of methanol treatment is to activate the positively charged groups on the membrane, making it easier to combine with negatively charged proteins. PVDF membrane has high mechanical strength and is an ideal solid support material in blotting.
Polytetrafluoroethylene(PTFE)
The characteristics of the filter membrane which is made of polytetrafluoroethylene have the widest chemical compatibility. It can tolerate strong solvents such as dimethyl sulfoxide, tetrahydrofuran, dimethylformamide, methylene dichloride, formyl trichloride, and so on. The polytetrafluoroethylene filter membrane is applied for the filtration of all sorts of organic solutions, especially for the strong solution which cannot be tolerated by other membranes.
Moreover, the polytetrafluoroethylene filter membrane has extremely stable chemical properties. It can tolerate strong acids, strong bases, strong oxidants, all kinds of corrosive liquids, and organic solvents. The operating temperature ranges from -180 °C to 250 °C.
Polyethersulfone(PES)
The polyethersulfone filter membrane is a kind of hydrophilic membrane, that has the advantages of a high flow rate, low soluble substance, and good intensity. Furthermore, the polyethersulfone filter membrane does not absorb protein and is extractive, so it will not pollute the samples.
In laboratories, according to the low protein adsorption and high medicine compatibility, the polyethersulfone filter membrane is specially designed for biochemical, inspection, pharmaceutical, and sterilization filtering devices.
Polypropylene(PP)
The advantages of polypropylene filter membranes include adhesive-free, stable chemical properties, pliable and tough, high-temperature resistance, autoclaved sterilization available, non-toxic and tasteless, and acid and alkali resistance.
This kind of membrane is always applied for making all sorts of rough filters, fine filters, and folding filter cartridges. Also, it can be widely applied in the areas of pharmacy, the chemical industry, food, and drinks.
Mixed Cellulose Ester(MCE)
MCE membrane filter also called mixed cellulose ester membrane filter, is ideal for colony counting and sterility testing. It is composed of cellulose acetate and cellulose nitrate, which has made it one of the best membranes in research and analytical applications. It is suitable for sterilizing filtration, air monitoring, and particle monitoring; it is also fit for clarification of aqueous removal and analysis and microbiology analysis.
Cellulose Acetate Membrane Filter
The protein absorption capacity of the cellulose acetate membrane is very low, which is very suitable for aqueous solution and alcohol. The cellulose acetate membrane has improved solvent resistance. The membrane filter can withstand 180℃ high temperatures, so it is suitable for hot gas and disinfection by various methods while maintaining the integrity of the membrane.
Nylon Membrane Filter
The nylon membrane filter is suitable for use with high PH samples and good for filtration of aqueous biological solutions, alcoholic solutions, and other aqueous solutions where protein, peptide, and nucleic acid binding is not a concern. Nylon membrane filter contains no wetting agents, which can greatly reduce the potential for extractable and leachable and provide good chemical resistance with aggressive fluids.
Nylon membrane filter has good mechanical strength and strong adsorption, it can withstand most organic solvents and most alkaline solutions, especially fit for the filtration of alkaline and solutions. A nylon membrane is a supported, naturally hydrophilic membrane, which is designed to wet out evenly and retain its superior strength during use in general filtration.
Produced through a proprietary manufacturing process, nylon membrane filter meets rigorous quality standards throughout every step of production. And this process generates consistent lot-to-lot binding among the membranes and ensures product uniformity. Low extractable guarantees tests will be clean and pure and lead to more stable results.
Micro-porous Glass Fiber Membrane Filter
It is made of 100% borosilicate glass fiber without binders or with the binder. The depth filter combines a fast flow rate with excellent loading capacity and retention of fine particles. The small diameter fibers endow micro-glass media with superior efficiency and dirt holding compared to cellulose and other synthetic media.
The glass fiber (GF) filter membrane belongs to the deep filtration category. Its main use is to be considered as a filter layer by directly putting on a filter membrane.
The GF filter membrane is made of 100% glass fiber without any binders. One of its most important features of it is its high flow rate. It could filter small particles with low resistance. Compared with other fiber materials and synthetic materials filter membranes, the glass fiber filter membrane has higher filtration efficiency and strong dirt-holding capacity. Moreover, it can withstand high temperatures of 500 °C, and its large surface area gives it excellent retention capacity.
The GF filter membrane can be used for the pre-filtration of membranes, which could effectively prevent the clogging of the membrane. Due to its high resistance to high temperatures, it can be used for analytical experiments that require burning and high-temperature gas filtration.
It can be widely used in daily environmental air pollution monitoring because of its large capacity and fast flow rate. When filtering more viscous and difficult-to-filter liquids, such as a serum, usually the multi-layer filtration method would be adopted. There will be a polyester separation layer between the 2-3 layers of filter membranes with different pore sizes stacked., which can facilitate liquid filtration. The uppermost layer is the GF filter membrane.
Summary
In short, the microporous filter membrane is mainly applied for the analysis of samples, especially for the filtration of the mobile phase and samples in the chromatographic analysis. It has a good effect on protecting the chromatographic column, infusion pump pipeline system, and sample valve from not being polluted.
It is widely used in gravimetric analysis, microanalysis, colloid separation, and sterility test. In general, it should be noticed that when choosing the filters, we should choose appropriate microporous filter membranes according to the physical and chemical properties of the filter media.
When purchasing, you should choose the material reasonably according to your application.
