27-11-2012, 01:04 PM
MEMBRANE FILTERS
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Introduction
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, Cellulose Acetate,
and Nylon 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. PCTE membranes
are track etched.
Performance Characteristics of Advantec Membranes
• Strong: Advantec membranes are monitored for both
burst (longitudinal) and tensile (lateral) strength.
Supported Acetate and Nylon are the strongest reverse
phase membranes available from Advantec
• Chemically and biologically clean: As part of a comprehensive
quality program, only high purity reagents and
raw materials are used to produce Advantec membranes.
Once cast, the membranes are handled in a class 1000
clean room to minimize ambient contamination. While
some membranes require a small amount (0.1–3 weight %)
of an aqueous wetting agent, Cellulose acetate has the lowest
aqueous extractables (0.1 weight %) and Nylon, inherently
hydrophilic, contains no added wetting agents or
surfactants. All Advantec membranes are Triton-free
except Nylon
• Thin membranes with high porosity: Uniformly thin
membranes (typically 150 μm) with high porosity (about
80%) provide high gas and liquid flow per unit area. High
porosity also provides high surface area for adsorption or
binding
• Thermostable: All Advantec membranes can be sterilized
by autoclaving. Operating temperatures of up to 180°C
can be achieved depending upon the membrane polymer
(see individual membrane specifications for details).
Advantec membranes exhibit minimal shrinkage at
elevated temperatures
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
• Sterilizable: May be repeatedly sterilized without loss of integrity
or change in bubble point
• 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 (see page 4)
Disposable Syringe Filter Units – DISMIC/LABODISC
• Minimum sample hold-up: Unit housings are specifically designed to
maximize sample recovery
• High purity: Non-pigmented housing and integral filter sealing assure
that filtrates will not be adulterated due to pigment, dye, or adhesives
leaching into the filtrate
• Convenient: Each unit is clearly marked with an identifying code to
denote pore size, membrane material and housing polymer
• Sterile: Units can be purchased presterilized and individually packaged,
or nonsterile in bulk pack
• All polypropylene can be autoclaved
Acrylic can not be autoclaved