Function, Classification, And Selection Of Syringe Filter

 Syringe filters are divided into organic and water systems. What are they used to filter? The syringe filter structure has two parts, housing, and membrane, which can be made of different materials. Usually, housing is polypropylene pp or nylon polyamide. Polypropylene has stable properties and is resistant to various solvents.

The so-called water system/organic system should be classified according to the material of the filter membrane, which is suitable for filtering aqueous solutions (for life sciences) and organic solutions (for chemistry). The so-called organic system should be used to filter aqueous solutions without any problems, but the water system may be dissolved by organic solvents, which is not suitable for the filtration of organic systems.

Classifications

Common filter membranes have pore diameters of 0.22 micron and 0.45 micron. The diameter of the filter is 1.0, 1.3, and 2.5 cm. It is used with disposable syringes and needles. It is placed between the two and the interface is standard, which is commonly used to process HPLC samples.

The price of syringe filters is divided into one-time and multi-time, organic or water-based, the specifications are Φ13 or Φ25, used for sample filtration in liquid or gas phase analysis. Filter materials include nylon (Nylon), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), mixed cellulose (MCE), cellulose acetate (CA), glass fiber, polypropylene ( PP), polyethersulfone (PES).

Selection method of syringe filter

1) Hydrophilic samples: select hydrophilic membranes, which have an affinity for water and are suitable for filtering water-based solutions. Available filter membranes are mixed cellulose ester, polyethersulfone (PES), etc.

2) Strongly corrosive and aggressive organic solvents (Properties: transparent, colorless liquid): generally use hydrophobic membranes, such as PTFE, polypropylene (PP), and other material quality filter membranes.

3) Protein solution: Choose a membrane with low protein adsorption, such as PVDF membrane. The microporous filter membrane is made by using polymer chemical materials and applying pore-forming additives on the support layer after special treatment. To be used for the filtration of water-based solutions, it is also called a water-based membrane.

4) Ion chromatography: PES filters are generally considered to be more suitable for filtration of solutions with low inorganic ions.

In addition to considering the above factors, the volume of the sample should also be considered. Generally, when the sample size is less than 2ml, a 4mm diameter microfilter is used; when the sample size is between 2-10ml, a 13mm diameter filter is used.

When the sample size is greater than 10ml, choose a 25mm diameter filter. The microporous filter membrane is made by using polymer chemical materials and pore-forming additives after special treatment and smearing on the support layer.