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available . . . in
Syringe Filters
0.45 and 0.22um
13, 25, 33mm Diameter
CA, PES, Nylon, PP, PVDF, PTFE
Non-sterile
STERILE
Normal single filter
GF preFilter 1um / Main
multiLayer 10,1.0,0.7um / Main
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Whatman GD/X PVDF
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Membrane Disc Filters 
BottleFilters and Glass Funnels
0.45um
Nylon, PVDF,
Glass Fibre 1um
47mm Diam
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Filtration Speed
- micron size of filter media
0.45um > 0.22um >>0.1um
- surface area of media
33 > 25 > 13mm Syringe Filter
90mm VacuCap > 70mm >50mm BottleTop Filter
- source of pressure
Positive pressure OR Vacuum
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“how long is a piece of string” . . . it All depends . . .
it IS VERY sample dependant . . . Trial and Error required
- particulate matter; how dirty and NOT just visible dirt but from product manufacture re crude paper filter methods - “invisible fibres” etc
Factors :
Viscosity . . . temperature dependant / dilution if possible oils/solvents
warm fluid . . . in extreme cases use Syringe Pump and heated Syringe Jacket
Chemical Compatability / wettability sample fluid & filtration media and equipment
Specifics : Teflon and PVDF may need to be prewetted - isopropanol
Structure of different OEM filter media for same nominal pore size may be different
random fibres vs mesh type : pore size is a average pore size measurement and porosity depends on dispersion of pores about a mean size
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some Equipment Limitations
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BottleTop Filter  preferred for aqueous media and medium Vac < 250mm Hg
- higher vacuum can collapse plastic vacuum bottles
- plastic bottles can be softened with “oils” particularly if media has to be warmed )
- aggressive solvents can soften filter housing material (PP/syringe filters )
- filter fibres can swell ( close off pores ) if filter media and fludis are ”less” compatible
match hydrophyllic with hydrophyllic and hydrophobic with hydrophobic
- non polar oils use PP, Teflon PVDF
- essential oils/ fatty acids ester oil PVDF, Nylon perhaps
- aqueous solution, high speed PES (polyetherSulfone), Nylon
Glass Filtration Equipment - requires Heavy Duty Glass receiver
- more expensive . . . initial cost
- very robust ( but NOT unbreakable )
- safer for higher vacuum if required ( use safety shield as glass can implode if scratched or cracked )
- can be easily cleaned . . . sterilised in needed
- will handle most aggressive fluids and solvents
Vacu-Cap  - for large batches ( 100ml to 1000ml )of fast fluids, generally aqueous and often HandVacuum pump adequate and controllable /managable.
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Vacuum System
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Hand Vacuum Pump : can develop higher vacuum at slow filtration speeds and collapse plastic filtration vacuum bottles
- use small filter flasks less pumping required - can be tedious/tiresome for large batches and fast flow fluids
Motorised Vacuum Pump : for large batches, vacuum can be regulated and filtration pumps 250mm HG is adequate for most fluids
- takes tedium out of slow filtration fluids ie set and “forget”
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Syringe Filter 
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- pressurised by thumb pressure ( syringe dispenser )
33mm for 50 to 200ml, 25mm 25 to 100ml, 13ml 5 to 25ml - depending
for large through puts - tedious and thumb soreness are issues
- slow fluids use a Syringe Pump - for viscous fluids either dilute with a solvent or use a Syringe Heater jacket ( can easily develop 100psi ) Syringe Filters are rated only to 50-75psi max
Use Heavy Duty Glass Syringe or SS syringe if necessary
- come in a variety of filter materials; CA, Nylon, PES, PP, PVDF, Teflon
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Prefilters
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- are used to speed up flow and SF capacity coarser layer traps large particles and helps protect the main filter material
- Glass Fibre preFilter usually 1umlayer built-in ( Membrane Solutions )
- multiLayer preFilter : 10um, 1um , 0.7um layers then main filter 0.45um or 0.22um
- Glass Fibre preFilter can also be used with Filter Funnel systems - either stand-alone GF Filter or separate membrane filter added on top of main filter / combined
Whatman GD/X PVDF Syringe Filters . . . are AGAIN now available from Chromalytic Tech
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re “Sterility”
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This is not to be regarded as advice re TGA implications - see Chromalytic DISCLAIMER
Sterile equipment; filters etc WILL NOT sterilise unsterile fluids
Where originally STERILE Fluids need to be filtered AND Sterility needs to be maintained then ALL filtration equipment including Filter Media must be purchased sterile or suitably sterilised in-situ and recommended handling proceedures / asceptic conditions
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some methods
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disinfectants, boiling water, dry heat 300deg C ( borosilicate glass )
(steam) autoclaving ( 130degC )
industrial , ethylene oxide gas; gamma irradiation . . . with clean room handling/packaging to strict TGA requirements . . . for pharmaceuticals and medical use
MicroFiltration : 0.45um sterile filters - only part successful ( arbitrary 60% )
0.22um sterile filters much more effective ( 90% )
0.1um sterile filters - 98% - but NO GUARANTEES !
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