Membrane Filtration

Membrane Filtration
- Ahlstrom Brand – ReliaDisc and ReliaPrep
- Sartorius Original
Cornelia Wiegand
Ahlstrom ReliaDiscTM Membranes
– Gridded sterile nitrocellulose membranes for use in
colony counting and microbiological quality control.
– Non-sterile microfiltration membranes used to remove
particles and microorganisms from organic solvents
(PA, PTFE, RC) and aqueous solutions (CA, CN).
Ahlstrom ReliaPrepTM Syringe Filters
– Wide variety of highest quality syringe filters for
convenient sample preparation and fluid sterilization.
– CA and PES membranes recommended for aqueous
solutions filtration; PA, PTFE and RC membranes
recommended for organic solvent filtration.
Many references available on special order.
Depth filters versus membrane filters
Syringe Filters
Application Overview
Microbiology, Colony Counting
Filter Types
Depth Filters
Filter papers are mostly made of cellulose
and are characterised by high absorbency.
They have high particle retention capacity
and allow a large sample throughput.
Depth Filter
– The filter matrix consists of a threedimensional network of fibres.
– Retention of particles and micro organisms
mainly in the "depth" of the filter matrix by
mechanical retention and adsorption.
– Advantage: High particle holding capacity
without premature clogging.
– The nominal retention rate is especially
influenced by the diameter of the fibres, the
"compactness" of the fibre structure, and the
thickness of the filter.
Depth Filter Structure
Cellulose Fibre – Glass Fibre
Filter Types
Surface Filters
–Membrane Filters are relatively thin and
made of synthetic polymers.
They are used for the filtration of fine
particles or the collection of microorganisms.
Surface Filter
The filter matrix consists of a homogeneous
"sponge-like" pore structure of high
mechanical stability and pressure
Retention of particles and micro organisms is
mainly "on or near the surface of the“ filter
matrix by mechanical means.
Advantage: High safety against breakthrough
even at high differential pressures and
pressure surges.
Surface Filter Structure
Cellulose Acetate - Polycarbonate
Scale of Dimensions
– 1 µm = 0.001 mm = 0.000001m
monkey hair
smallest particle you can see
yeast bacteria
Cellulose Acetate (CA)
- High flow rates
- Low affinity for protein
- Routinely used to filter protein solutions
e.g. Fetal calf serum (FCS)
Bovine serum Albumin (BSA)
- Good resistance to certain solvents
- Manufactured without surfactant (SFCA)
- Good handling, especially when wet
- Autoclavable
- Pore size 0.2 ; 0.45: 0.65 ; 0.8; 1.2; 5 µm
Regenerated Cellulose (RC)
For ultra cleaning and de-gasing
solvents and mobile phase for
Solvent-resistant hydrophilic
- Particle removal of solvents
- Low non-specific adsorption
- Good handling
- Pore size 0.2 and 0.45µm
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How to convert to RC
–Chemical compatibility
–Flow rates
–Non-specific binding
–Thermal stability
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Minimizing Extractables
What can cause extractables
- Solubility and chemical compatibility
- Particle displacement
Why reduce extractables?
How do you reduce
- HPLC certification
- Increase accuracy by removing unwanted particles
- Compatibility tested with commons solvents
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Polyamide (NY)
Relatively slow to moderate flow rate
due to low porosity and membrane
thickness (150- 200µm)
- Excellent solvent resistance (Ideal for
- No surfactant required
- Very low level of extractables
- High non-specific affinity for proteins.
- Used as an alternative to CN for blotting
- Not recommended for filtering proteins
e.g FCS and BSA
- Autoclavable
- Pore size 0.2 and 0.45µm
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Polyethersulphone (PES)
- Fast flow rates
- Low extractables
- Low protein binding
- Good solvent resistance
- Autoclavable
- Good membrane for FCS
- Pore size 0.1; 0.2 and 0.45µm
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Polytetrafluoroethylene (PTFE)
- PTFE is very low protein binding
- Has good to moderate flow rate
- PTFE resistant to all known
- PTFE is hydrophobic
- Used for venting applications
- Pore size 0.2 ; 0.45 ; 1.2 and
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Membrane Filtration
–Sterile filtration and ultra cleaning of liquids
=> 0.2µm
–Particulate removal of liquids, micro-biological
reduction filtration and particulate removal of dry
air and gases
=> 0.45µm and 0.8µm
–Clarification and pre-filtration
=> 1.2µm and 5.0µm
Membrane filtration has to become
supported either by vacuum or by pressure
Disc Filters and Disposables
Disc membrane filters
• used in a disc device
• autoclavable device
Ready to use filters
• have integrated membranes
• smal hold-up volumes
• available sterile or nonsterile
Vacuum glass filter holder
– For disc membranes
– Size diameter 13mm and
Syringe filters / CA
• rapid clarification or sterilization of up to 100 ml
liquid volumes
• low unspecific adsorption
• fitted to a dosing syringe makes a very convenient system
for dosing and sterilizing
• different pore size membrane filters => colour coded
• 0.45, 0.8, 1.2, 5.0 can be mounted directly in front of
an 0.2 µm syringe filter
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Syringe Filter Housing
MBS (methacrylate butadiene
styrene polymerisate or Cryolite)
– Similr to Plexiglas – good tensile
strength and impact strength
– Non-autoclavable. Can be Gi or
EtO sterilized
– Limited thermal resistance
– pH range 3 - 12
PP polypropylene
– Can be autoclaved or EtO
– Outstanding chemical
– Low extractables
– pH range 1-14
Syringe Filters, Application Overview
Recommended Application
Sterile Filtration
Removal of microorganisms from solutions with ≤0.2um hydrophilic
syringe filters: PES/CA/RC/Nylon
The pre-filtration and purification of liquids with ≥0.45um hydrophilic
syringe filters
Chromatographysample prep
Ultra cleaning of small volume samples with chemical resistant syringe
filters: RC/Nylon/PTFE
Removal of microorganisms from gasses and air with hydrophobic
0.2um syringe filters: PTFE
CA syringe filters for use in hospitals and pharmacies.
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Volume / Diameter
Volume to filter
Aqueous solution, solvents
Aggressive solution
Up to 1 ml
RC 4 mm
PTFE 4mm
Up to 5 ml
RC 15 mm
PTFE 15 mm
Up to 100 ml
RC,25 mm
PTFE 25 mm
HPLC Sample Preparation / Chromatography
Sterile Venting
Syringe filters with
integrated PTFE
membranes 0.2 µm
Reusable filter
holder 0.2 µm
PTFE membranes
DMEM-Medium plus 20%FCS
Lipofundin MCT 20% +0.1 % tween
Microbiology Products
– Colony counting
Higly symmetric
membrane structure
Optimized media
for MF method
Cellulose nitrate membranes
– Uniform distribution of culture media
– Optimal flow and retention
– High recovery of microorganisms
Varity of colors
Varity of pach