Membrane Filter Selection Method

Microporous membrane is made of polymer chemical materials, and pore-forming additives are specially treated and applied to the support layer.

Features

Properties: flammable, should be sealed during storage, moisture-proof and fire-proof.

1. Features: relatively uniform pore size, high porosity, no medium shedding, thin texture, small resistance, fast filtration speed, and minimal adsorption.

2. Main uses: filter out bacteria from particles of liquid medicine, gas, oil, beverage, alcohol, electronic instruments, etc., and can also be used for particle and bacteria plug tests.

Selection method of filter membrane

1. Determine the membrane pore size

Different organisms have different particle sizes, so these differences need to be considered when choosing the appropriate membrane pore size.

For example, bacteria typically have a particle size between 1-10 μm, while viruses typically have a particle size between 0.05 and 0.1 μm. Therefore, the membrane pore size should be selected to ensure that the target substance passes through while filtering out the undesirable particles.

2. Characteristics of filtered samples:

A: Hydrophilic samples: Hydrophilic membranes are suitable for filtering solutions with water as the matrix. Such as tap water, and surface water, and the available filter membranes are: water system membranes (mixed cellulose esters), and nylon membranes (polyamide).

B: Organic and inorganic compounds (alcohols, esters, oils) samples are suitable for nylon membranes (polyamide).
C: Protein solution samples: Suitable for filter membranes with low protein adsorption. That is, PVDF membrane.
D: Strong acid and strong base samples suit hydrophobic PTFE (polytetrafluoroethylene membrane).

3. Determine the sample volume

Filter flow reference

Filter membrane diameter Φ13mm filter 2-10mL

Filter membrane diameter Φ25mm filter 10-100mL (pre-filtration up to 200mL)

Filter membrane diameter Φ50mm filter 0.2-8L

Characteristics and applications of several commonly used filter membranes:

Types and applications of microporous filter membranes
To filter solvents, generally use solvent filters + membrane filtration
To filter samples, generally use needle filters

4. Determine the membrane type

1. CA Cellulose Acetate

Features: Good hydrophilicity, very low binding force for most macromolecules, and good applicability for experiments with high requirements for reducing protein binding.

Applications: Suitable for filtering buffers, aqueous reagents, and solutions, including EIA and ELISA samples.

2. PES Polyethersulfone Membrane

Features: The filter membrane has low protein binding capacity, ultra-low extractable content, and high flow rate, making it the preferred choice for filtering culture media. The flow rate of PES membranes is also higher than that of cellulose or nylon membranes. PES Express has a faster filtration speed and a lower clogging rate.

Applications: Commonly used for filtering general aqueous solutions, culture media, serum, or protein solutions in laboratories.

3. Water-based membrane (mixed cellulose ester CN-CA)

Characteristics: uniform pore size, high porosity, no media shedding, thin texture, low resistance, fast filtration rate, low cost, but not resistant to organic solutions, and strong acids and alkalis.

Applications: drinking water, surface water, well water, etc., sterilization filtration, analysis of particles and oil-insoluble substances in solutions, determination of water pollution index, filtration of particles and bacteria such as gas, oil, beverages, and wine. It is one of the most widely used filter membranes in sample pretreatment filtration.

The actual volume filtered depends on the membrane material, membrane pore size, the solution itself, and the speed at which it blocks the membrane. Relatively clear solutions that do not contain a large number of particles or a large amount of protein will be easier to filter, thereby allowing more volume to pass through the membrane effectively. On the other hand, solutions with a high number of particles may block the membrane after passing through a few milliliters.