Membrane Filters
Membrane filters or “membranes” are microporous plastic films with specific pore size ratings. Also known as screen, sieve or microporous filters, membranes retain particles or microorganisms larger than their pore size primarily by surface capture. Some particles smaller than the stated pore size may be retained by other mechanisms.
Advantec membranes are produced by three different processes. Mixed Cellulose Esters and Cellulose Acetate, are reverse phase solvent cast membranes, where controlled evaporation or removal of the complex solvent system forms the porous structure. Both hydrophilic and hydrophobic PTFE are made by a patented process where the membranes are stretched biaxially to form the porous structure. Polycarbonate membranes are track etched.
Mixed Cellulose Esters (MCE)
- Composition: Mixed cellulose esters including cellulose nitrate and cellulose acetate, also known as nitrocellulose.
- High porosity provides superior flow rates.
- High protein binding can be blocked by pretreatment or utilized in applications.
- High purity: Triton-free.
- Autoclavable: Withstands autoclaving temperatures up to 130°C without adversely affecting bubble point, flow rate or microbiological recovery.
- Rapid wetting time: <3 seconds to wet a 47 mm diameter disc with aqueous 1% methylene blue.
Applications:
- Standard membranes for many laboratory applications including filter sterilizing biological fluids, microbiology, contamination analysis and air monitoring.
- Can be transparentized to view collected particles – using compatible liquid (immersion oil, toluene), OR – select Opticlear membranes for the “hot block” acetone vapor method.
- Gridded filters available for quantifying microbial growth.
- Available non-sterile or sterilized by ethylene oxide (EtO).
Cellulose Acetate
- Composition: Mixture of cellulose triacetate and diacetate.
- Characteristics: Low static charge and high strength.
- Autoclavable: Withstands autoclaving temperatures up to 130°C without adversely affecting bubble point, flow rate or microbiological recovery.
- Clean: Lowest aqueous extractables (0.1 wt%) of all Advantec membranes.
- Relative to MCE (Mixed Cellulose Esters, Nitrocellulose):
– improved solvent resistance to low molecular weight alcohols
– better heat resistance
– lower protein binding
Applications:
- Enhanced recovery of fastidious gram positive organisms.
- Filtration of enzyme solutions.
- Diagnostic cytology.
- Receptor binding studies.
Hydrophobic PTFE
- Properties: Thin, highly porous, behaves as an absolute retentive membrane.
- Inert to most chemically aggressive solvents, strong acids and bases.
- Operating Temperature Range: -120 ~ 260ºC.
- Autoclavable.
Applications:
- Sterilize gases: traps aqueous aerosols.
- Air and gas venting: allows gases to pass freely while blocking aqueous liquids, protect vacuum pumps and critical samples.
- Sterilize and clarify strong acids and many other solvents incompatible with other membranes.
Hydrophobic PTFE with Supported Polypropylene Net
- Properties: Thin, highly porous, behaves as an absolute retentive membrane.
- Supported: Hydrophobic PTFE laminated with polypropylene to improve handing.
- Inert to most chemically aggressive solvents, strong acids and bases.
- Operating Temperature Range: -35 ~ 130ºC.
- Autoclavable.
Applications:
- Sterilize gases: traps aqueous aerosols.
- Air and gas venting: allows gases to pass freely while blocking aqueous liquids, protect vacuum pumps and critical samples.
- Sterilize and clarify strong acids and many other solvents incompatible with other membrane.
Hydrophilic PTFE
- Characteristics: Maximum chemical and pH resistance.
- High flow rates with minimal aqueous extractables (<0.3 wt%).
- Optically clear when wet with water.
- Non-supported.
- Thermostable: can be used up to 100ºC.
Applications
- Ideal for HPLC and other mixtures of aqueous and organic solvents
Note: Hydrophilic PTFE membrane filters are not autoclavable.
Coated Cellulose Acetate
- Composition: Cellulose acetate cast onto a non-woven polyester support.
- Characteristics: Non-fiber releasing.
- Low protein binding relative to nitrocellulose.
- Low static charge matrix with enhanced chemical compatibility to low molecular weight alcohols.
- Autoclavable.
Applications:
- Use as a clarifying filter or prefilter
Polycarbonate
- Characteristics: Low non-specific binding and optically translucent, extremely uniform, cylindrical pores.
- Thin screen-type membranes minimize entrapment within the filter structure; resulting in surface capture of particles on the membrane.
- Stable: excellent chemical resistance, good thermal stability, non-hygroscopic and extremely weight stable.
- Autoclavable: at 121º C, 30 min.
Applications
- Epifluorescence microscopy: available in black for this method.
- Electron microscopy: smooth surface is ideal for observing captured particles.
- Light microscopy: easily transparentized for optical illumination.
- Beverage and sterility testing.