What is the Role of Filter Membrane in the Syringe Filter?

As one of the most frequently used tools in experiments, the syringe filter brings much convenience, and here are three key parameters of a syringe filter.

  1. Filter membrane material: such as nylon, polyethersulfone, polytetrafluoroethylene
  2. Aperture: such as 0.22μm, 0.45μm, and 1-5μm, whether it’s for general chromatographic requirements, requirements for removing very fine particles, or pre-filtration.
  3. Diameter: such as 13mm, 25mm, 47mm

The commonly used microporous filter membrane is generally a disc filter membrane, such as a 25mm disc microporous filter membrane, which can be used with a syringe filter connected to a syringe. For the 47mm disc microporous membrane, you can use it in the membrane filter, Buchner funnel, pressure vessel, etc. with the vacuum pump and pressure pump. There are also larger diameter microporous membranes, which also require corresponding clamps and pressure to be used together.

Today, starting from the core membrane materials, HAWACH discusses the performance and material of the membrane materials to make you choose easily and correctly. With the deepening of modern life science research, the role of experimental sample filtration in the entire experiment is becoming more and more important. However, there are many membrane materials on the market. How to choose membrane materials according to your own application needs? It is not easy for workers. For example, how to choose a syringe filter in LCMS, how to choose a filter membrane when the solvent is unknown, whether there is a universal membrane that can be used in the world, etc. All trouble the experimenters in daily experimental work.

Usually, we pay attention to several important parameters when selecting products based on applications. The key factors for investigation are sample throughput and applicable membrane materials. Here we focus on how to choose a suitable filter membrane material. The membrane material is the “active” part of the filtration product or the part where the product plays a role. Understanding the characteristics of membrane materials can help us choose the most suitable filter material.

hydrophilic ptfe membrane filter hydrophobic ptfe membrane filter hydrophobic membrane and hydrophilic membrane

The following is a summary of commonly used membrane materials on the market.

1. Hydrophilic filter membrane material

(1) Hydrophilic polypropylene membrane

Polypropylene membrane is a kind of “universal” membrane with a wide range of applications. Its hydrophilic properties make it applicable to the filtration of aqueous solutions as well as the filtration of organic solutions. This polypropylene membrane has strong chemical compatibility and is more commonly used in environmental testing and applications that require exposure to organic solvents. Its performance has been tested and verified in the application of HPLC (High-Performance Liquid Chromatography), this kind of membrane will not cause contamination of the test sample due to the eluate in use. This feature also eliminates the possibility of contamination of the sample caused by the leachate of the membrane.

The self-fluorescence value of the polypropylene membrane is very low, so it will not increase the background “noise” in the application of distinguished fluorescence detection. It is also a non-adsorbent membrane that can prevent the non-specific binding of target molecules. There are two pore sizes of 0.2μm and 0.45μm to choose from.

The scope of the application includes:

  • Strong organic solvents required
  • High-throughput screening
  • Receptor: Ligand Screening
  • Compound library screening
  • HPLC sample preparation
  • Shearing reaction
  • Metabolism research
  • Routine sample preparation

(2) Hydrophilic polyethersulfone membrane

It is optimized specifically for the needs of biological, and pharmaceutical industries and sterilization filtration. PES membrane has low protein binding properties and is a good choice for the recovery of trace samples. It has a wide range of drug compatibility and moderate chemical resistance/compatibility. Its characteristics include high flow rate, high throughput; low protein adsorption; high temperature and high-pressure sterilization; low dissolution; and high consistency. PES membranes are available in pore sizes of 0.1μm, 0.2μm, 0.45μm, 0.8μm, and 1.2μm.

The scope of the application includes:

  • Screening for neonatal metabolic diseases
  • Application based on microsphere/resin
  • Receptor: ligand analysis
  • Lysate clarification
  • Routine sample preparation

(3) Nylon membrane

Nylon membrane has a wide range of applications. Modification can be used to optimize the grade of the membrane. It can be used for high or low adsorption capacity, environmental atmospheric monitoring, and even sample preparation for chemical analysis. Nylon transfer membrane is a product optimized for the combination of biomolecules and is suitable for radiological and non-radioactive detection systems. There is also a low absorption membrane, which is 25-50 times lower than the traditional nylon transfer membrane. Another kind is an acid rain detection membrane, which is also a clean membrane and is very suitable for the preparation of analytical samples before HPLC analysis. Nylon membranes are available in pore sizes of 0.2μm, 0.45μm, 1μm, and 1.2μm.

The scope of the application includes:

  • Sample Preparation
  • Environmental monitoring: used for acid deposition
  • Bead-based analysis
  • Drug combination research
  • Recovery of nucleic acid samples in acrylamide gel

2. Hydrophobic membrane material

(1) PTFE membranes

PTFE membrane is a hydrophobic material membrane that can be used in a variety of routine sample preparation and filtration. PTFE membrane filters can be used when the membrane material is required to exhibit hydrophobic properties to prevent the flow of moisture and allow air or gas to filter through. PTFE membrane has a wide range of applications in filtering gas. The membrane will not allow liquid to filter through until it is “soaked”. PTFE shows an excellent blocking effect on passive fluids, which is very suitable for filtration that requires an incubation step. PTFE membranes are available with 0.2μm, 0.45μm and 1μm pore diameters.

The scope of the application includes:

  • Molecular synthesis reaction
  • Drug synthesis reaction
  • Organic sample preparation
  • Ventilation of fermentation tanks and fermentation barrels

pvdf membrane filter hydrophobic ptfe membrane filter ptfe membrane filters

3. Pre-filter membrane material

The pre-filtered membrane can be used to increase the flow rate of the filtrate and remove particles for clarification experiments. The large pore size of the pre-filtration membrane helps to remove particles and cell debris. The membrane has the same non-adsorption characteristics as previously described. There are many different configurations of pre-filtration membranes to choose from.

The scope of the application includes:

  • Clarification of cell lysate
  • Plasmid preparation
  • Preparation of samples saturated with particles
  • Preparation of protein solution

4. Molecular separation (ultrafiltration) membrane material

Ultrafiltration membrane

It is a modified polyethersulfone membrane designed to reduce the adsorption of proteins and nucleic acids. The membrane is based on the principle of molecular exclusion to separate samples according to their molecular weight. Molecular exclusion can be achieved by selecting a suitable molecular weight cut-off membrane to separate large and small molecules, and then separating samples by vacuum or centrifugal filtration. Modification of the membrane can prevent the adsorption of biomolecules to the membrane and facilitate the concentration of larger molecules on the membrane surface. The low adsorption of the membrane gives it many advantages, including high recovery of low concentrations of biomolecules and lower surface contamination, which may weaken the membrane’s retention.

Generally, choosing the right molecular weight cut-off is consistent with the principle of choosing the right centrifugal concentrated product. The molecular weight cut-off of the membrane should be 1/6 to 1/3 of the molecular weight of the biomolecules that are cut off. For example, if the molecular weight of the protein to be retained is 60K, a membrane with a molecular weight cut-off of 10K should be selected. The available membrane molecular weight cut-offs include 1K, 3K, 5K, 10K, 30K, 50K, 100K, and 300K.

The scope of the application includes:

  • Concentration, purification, and desalination of peptides, proteins, oligonucleotides, DNA, and RNA
  • Labeling reaction and PCR reaction recovery
  • Separate DNA from agarose gel
  • Size exclusion chromatography

5. Filter membrane material combined with biomolecules

Glass fiber membrane filters with polypropylene as the backing layer
The use of glass fibers in the filter plate provides an economical and feasible solution for removing particulate matter in the sample and maintaining the integrity of the sample. This is a good choice for low-cost, crude sample preparation. The glass fiber is made of non-sticky borosilicate glass, which will not cause impurities to dissolve out and contaminate the sample. The glass fiber membrane is supported by a polypropylene layer. The support layer will not have eluted matter and can prevent the glass fiber from falling into the sample. Available aperture specifications include 1.0μm and 3.0μm.

  • The scope of application of glass fiber membranes includes:
  • Cell-based analysis
  • Coarse fractionation
  • Receptor: ligand binding analysis
  • DNA binding
  • Plasmid DNA extraction

(1) Anion exchange membrane

The membrane has super anion exchange capacity, a fast sample processing flow rate, and does not affect the binding and recovery, and its binding capacity per well can reach 0.38mg bovine serum albumin/well. There are two product forms filter plate and syringe filter.

The scope of the application includes:

  • Removal of virus particles
  • Binding and elution of negatively charged proteins
  • DNA purification

(2) Cation exchange membrane

The membrane has a super strong cation exchange capacity to process samples with a fast flow rate and does not affect the binding and recovery, and its adsorption capacity per hole can reach 0.29mg lysozyme/well. The membrane is available in two product forms: filter plate and syringe filter.

The scope of the application includes:

  • Kinase detection
  • Binding and elution of positively charged proteins

(3) Pure nitrocellulose membrane

With a pore size of 0.2μm, it is a 100% pure nitrocellulose membrane with good durability and high binding ability to proteins and nucleic acids. The binding effect of the membrane is based on its hydrophobic and electrostatic effects, which makes it very suitable for spot hybridization of proteins and nucleic acids. The membrane is widely used and can be used for chemiluminescence, fluorescence, colorimetric, and radioisotope detection.

The scope of the application includes:

  • Nucleic acid transfer and detection
  • Solid-phase ELISA (enzyme-linked immunosorbent assay)
  • Radioimmunoassay
  • Fluorescence or chemiluminescence detection

(4) PVDF (polyvinylidene fluoride) membrane

PVDF filter has a wide range of uses and can be used for the combination of nucleic acid and protein. The membrane has a pore size of 0.45μm and has wide compatibility with common solvents. The background value of the PVDF membrane is very low when it is used for chemiluminescence detection. It will not fade during use and is durable. The binding reaction of the PVDF membrane is hydrophobic, and biomolecules can be immobilized on the membrane by UV cross-linking and base immobilization. Because PVDF membrane is not easy to fade, it is very suitable for the detection of color reactions.

The scope of the application includes:

  • Protein: Nucleic Acid Interaction Research
  • Western blot
  • Solid-phase ELISA (enzyme-linked immunosorbent assay)
  • Radioimmunoassay
  • Fluorescence or chemiluminescence detection
  • Use combined biomolecules for drug development
  • ELISA Spot EliSpots

As the saying goes, a good experiment depends on a good sample, a good sample depends on a good filtration, and a good filtration depends on the selection of the right membrane material. Based on the above introduction, HAWACH believes that your experiment has been half successful. With the further development of material technology, filtration technology will play an increasingly important role in our lives and work. Welcome to share more with us.

Please click here to know PVDF vs PTFE