Syringe filters are ideal for filtering the sample solution before injection. These are usually membrane filters made of appropriate materials. They are also available as glass fibre filters or as membrane filters with glass fibre pre-filters in cases where a glass fibre filter is required in front of the membrane filter. When selecting syringe filters, the highest quality materials should be used as the sensitivity of the analytical method increases. These are specially tested for interfering substances. In addition, they guarantee a high batch consistency for steady, reliable analytical results.
| Filter Material |
Properties |
| Cellulose acetate (CA) |
- hydrophilic membrane
- excellent dimensional stability in aqueous solutions
- extremely low binding capacity for proteins of 21 μg/filter at a membrane diameter of 25 mm
- especially suitable for filtration of tissue cultures and biological macromolecules
|
| Glass fiber (GF) |
- inert filter
- for solutions with high suspended solids content or high viscosity
- as pre-filters for other filters they prevent clogging of the membrane
|
| Nylon (PA) |
- hydrophilic membrane
- suitable for organic/ aqueous, medium polar liquids
- resistant to many organic solvents
- not resistant to acids and bases
- high retention value for proteins
|
| Polyethersulfone (PES) |
- hydrophilic membrane
- very low adsorption of pharmaceuticals and proteins
- very stable to bases, alcohols and acids (except oxidizing acids)
- well suited for aqueous and slightly organic solutions with higher flow rates
- binding capacity for proteins: 29 μg/ filter at a membrane diameter of 25mm
- mechanically very stable
|
| Polyester (PET) |
- hydrophilic Allround Membrane
- suitable for polar as well as non-polar solvents
- not cytotoxic
|
| PTFE (PTFE) |
- hydrophobic membrane
- for nonpolar liquids and gases
- very resistant to acids, bases and solvents of all kinds
- by rinsing with alcohol and water the hydrophobic membrane can be made water-wettable
- when using a wetting agent, PTFE can be used with aqueous solutions
|
| Polyvinlyde difluoride (PVDF) |
- hydrophilic membrane
- for polar as well as non-polar solutions
- binding capacity for proteins: 82 μg/ filter with a membrane diameter of 25 mm
- ideal for use in HPLC
- unsuitable for aqueous solutions
|
| Regenerated cellulose (RC) |
- hydrophilic membrane with very low adsorbtion
- for aqueous/ organic liquids (polar - medium polar)
- binding capacity for proteins: 84μg/ filter
- with a membrane diameter of 25 mm
- ideal for biological samples
- high chemical resistance
- high flow rates
|
| Glass fibre / regenerated cellulose (GF/RC) |
- syringe filters with prefilters are recommended for solutions with high particle loads or for highly viscous solutions
- these filters combine a coarse glass fibre prefilter and a narrow-pored regenerated cellulose membrane as the main filter
- the hydrophilic RC membrane is used for filtration of aqueous and organic-aqueous liquids, i.e. polar and medium polar sample solutions
|
