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Cellulose Acetate Membrane Filters, 0.45 Micron, 25mm, 100/Pk

Composed of pure cellulose acetate, Sterlitech cellulose acetate (CA) membrane filters are Sterlitech’s lowest binding small filter devices. These cellulose membrane filters have a pore size of 0.45 microns and a diameter of 25 mm

SKU
CA04525100
Manufacturer
Sterlitech
Pore Size
0.45
Diameter (mm)
25
Pack Size
100

Details

Cellulose Acetate Membrane Filters, 0.45 Micron, 25mm, 100/Pk

Cellulose Acetate Membrane Filter Applications

  • Protein/enzyme filtration and sterilization
  • Biological fluid filtration and sterilization
  • Tissue culture media sterilization
  • Diagnostic cytology
  • Receptor binding studies
  • Enhanced recovery of fastidious gram-positive organisms

Cellulose Acetate Membrane Filter Specifications

General

 Sterilization Gamma Irradiation, EtO, Autoclave
USP Class VI Test Passed
BSA Protein Binding 3.8 µg/cm2
 Max Operating Temp 135 °C (274 °F)

Performance by Pore Size

  Nominal Thickness Flow Rate1 Min. Bubble Point
0.22 µm 65-110 µm 16.1 50 psi
0.45 µm 65-110 µm 54.7 > 30 psi
0.65 µm 65-110 µm 70.9 18 psi
0.80 µm 65-110 µm 81.3 14 psi
1.20 µm 65-110 µm 180 11 psi
3.00 µm 135 µm 500 5 psi
5.00 µm 65-110 µm 375 6 psi
*Notes:
1. Flow Rates: Measured with water as ml/min/cm2 at 10 psi (0.7kg/ cm2)

 

Documentation / Media

Cellulose Acetate Membrane Data Sheet

Frequently Asked Questions


The pores of microporous membrane filters act as small capillaries.  When hydrophilic membranes come into contact with water, capillary action associated with surface tension forces causes the water to spontaneously enter and fill the pores.  In this manner, the membranes are easily wetted and allow the bulk flow of water through the pores.  Once wetted, hydrophilic membranes will not allow the bulk flow of air or other gasses, unless they are applied at pressures greater than the membrane’s bubble point.

Hydrophilic membrane filters are typically used with water and aqueous solutions.  They can also be used with compatible non-aqueous fluids.  Hydrophilic membrane filters are typically not used for air, gas or vent filtration since the filters would block flow if inadvertently wetted, by condensation for example.

When hydrophobic membranes come into contact with water, surface tension forces act to repel the water from the pores.  Water will not enter the pores and the membranes will act as a barrier to water flow, unless the water is applied at pressures greater than the membrane’s water entry pressure.  Low surface tension fluids, such as alcohols, can spontaneously enter and fill the pores of hydrophobic membranes.  Once all the air in the pores is displaced, there are no longer any surface tension forces and water can easily enter the pores, displace the low surface tension fluid, and pass through the membrane.  The membrane will then allow bulk flow of water for as long as the pore remain water filled.  If the membrane is allowed to dry (i.e. air enters the pores), then it must be pre-wet with a low surface tension fluid again prior to use with water.

Hydrophobic membrane filters are typically used with compatible non-aqueous fluids.  They are also commonly used as air, gas, or vent filters.  Hydrophobic membrane filters are sometimes used with water or aqueous solutions; and, in these applications, they must first be prewet with a low surface tension, water miscible fluid prior to use.

Sterlitech Cellulose Acetate (CA) membranes are made from cellulose diacetate. These membrane filters also have an integral nonwoven polyester (polyethylene terephthalate) support layer. When evaluating application compatibility, both materials should be considered.

Q. What is the maximum temperature for the different filter membranes?
A. The maximum operating temperatures for Sterlitech filter membranes are listed below.

 

*5.0um and 8.0um - max temp is 180°C

Cellulose acetate (CA) membranes are made of entirely cellulose acetate polymer.  These membrane filters have the lowest protein binding of the filer types in question and typically have the greatest throughput when used with proteinaceous solutions.  They are also used in applications where maximum protein recovery is critical. The Sterlitech CA membranes have an integral nonwoven polyester support layer for improved strength and handling ease.

Ideally, nitrocellulose (NC) membranes would be made entirely of nitrocellulose polymer. However, almost all commercially available filtration grade membrane filters labeled as “nitrocellulose” are actually composed of membranes made with a mixture of nitrocellulose and cellulose acetate polymers.   This is because pure nitrocellulose membrane filters are very difficult to manufacture with accpetable characteristics. In an effort to provide clarity to consumers, some manufactures refer to membranes containing a mixture of nitrocellulose and cellulose acetate polymers as mixed cellulose esters (MCE) membranes.  In almost all applications, commercial nitrocellulose (NC) membrane filters and mixed cellulose esters (MCE) membrane filters are equivalent.

Mixed cellulose esters (MCE) membrane filters do not have a discrete support layer and are somewhat fragile and more difficult to handle
when compared to CA membrane filters.  MCE membranes exhibit greater protein binding than CA membranes.  However, MCE membranes tend to have more uniform pore structure and intrinsically greater clean water flow.  MCE membrane filters have very good biocompatibility and are commonly used for microbiological studies.  MCE filters are also traditionally used for silt density index (SDI) measurments.

Regenerated cellulose (RC) membranes are made by chemically treating nitrocellulose membranes so that the material reverts back to natural
cellulose.  RC filters have the very good solvent resistance of traditional filter papers but with the much finer retention characteristics of polymer membrane filters.   Additionally, regenerated cellulose is inherently hydrophilic and RC filters do not contain the wetting agents required by MCE and CA membrane filters.

Yes, the cellulose acetate (CA) membranes contain a proprietary surfactant.  The surfactant is used to ensure the CA membrane filters have good wettability.

Q. What is the difference between nominal and absolute pore size ratings?

Nominal pore size ratings are provided as a general indication of filter retention.  It is understood that some quantity of particles greater than, and equal to, the nominal pore size ratings will pass through the filters into the filtrate.  Some manufactures may associate nominal pore size ratings with percentage filtration efficiencies. Nominal pore size ratings vary from manufacturer to manufacturer and, consequently, are not necessarily equivalent. Filters from different manufactures with similar nominal pore size ratings may not actually exhibit similar retention characteristics.

Absolute pore size ratings are typically based on retention studies performed using challenge suspensions of standard microorganism cultures or particles of known size. Absolute pore size ratings represent the size of the smallest microorganisms or particles completely retained during these studies. Absolute pore size ratings are almost always correlated to bubble point specifications that are used for quality control during membrane manufacturing. For the most part, absolute pore size ratings, especially those based on microbial retention, are comparable from manufacturer to manufacturer. There is more uncertainty for absolute pore size ratings based on particle retention studies, especially for pore size ratings <0.2µm, since there are no standard methods for these studies.

Regardless of pore size ratings, it is important to understand that application conditions do influence particle retention. Even filters with absolute pore size ratings can be operated in conditions that will allow unexpectedly sized particles to pass.


Not including the polyester support layer, the Cellulose Acetate (CA) membrane filters are composed entirely of cellulose acetate polymer.  There may, however, still be a small amount of residual lignin present. 


 

The pore size refers to the diameter of the individual pores in a membrane filter.   Pore size is typically specified in micrometers (µm).   Most membranes and filter media actually contain a distribution of pore sizes.  Nominal pore size ratings typically refer to the predominant pore size of a filtration media; pores larger and smaller than the nominal rating may be present.  Absolute pore size ratings typically refer to the largest pore size of a membrane and it is expected that all pores will be equal to or smaller than the absolute rating.

For the polycarbonate track-etch (PCTE) and polyester track-etch (PETE) membrane filters, porosity is the percent of the total surface area occupied by the pores; it typically ranges from <1% to 16%.  For the other membrane filters, porosity is the percent of the total volume occupied by the pores; it typically ranges from 40 to 80%.

Cellulose acetate (CA) membrane filters are one of the lowest protein binding filters available. They will generally have greater throughput with proteinaceous solutions when compared to other membrane filters. CA membrane filters are ideal for filtration of protein and enzyme solutions, tissue culture media and serums, biological fluids, and similar applications where maximum recovery of protein is critical.


CA membranes are manufactured with an integral nonwoven polyester support layer resulting in a dimensionally stable strong membrane that is easier to handle and resistant to curling. The filters have superior resistance to tearing and can withstand steam sterilization up to 135°C. They are suitable for use at elevated temperatures.


CA membranes are hydrophilic and readily wet in water and aqueous solutions. They have good chemical resistance and can be used with low molecular weight alcohols. 

You can find the Sterlitech compatibility guide.  It is important to realize that application conditions, such as operating temperature, affect compatibility.  Please contact us at [email protected] if you need assistance.

The bubble point is the minimum amount of pressure required to push air bubbles through the largest pore of a wet membrane.  The bubble point is inversely proportional to the pore diameter, as the pore diameter decreases the bubble point increases and vice versa.

Retention efficiency of membrane filters can be directly measured by challenging the filters with suspensions of standard microorganism cultures or particles of known size.  Unfortunately, such efficiency testing is necessarily destructive.  However, since retention characteristics are dependent on pore size, it is possible to correlate destructive challenge testing results to non-destructive membrane bubble point tests.  In this manner, the relationship between membrane pore size and membrane bubble point is empirically determined.  Typically, a minimum bubble point can be determined and specified for a particular pore size rating.  The bubble point specification is then used for quality control during membrane manufacture.  The bubble point can also be used by the consumer as a nondestructive test to verify membrane integrity before and/or after use.    

Depth filters are constructed with relatively thick filtration media and typically have nominal pore size ratings >1µm. Due to their large void volume, they capture significant amounts of particulate within their pore structure.
Membrane filters are typically composed of polymers that have been chemically processed, resulting in highly porous thin films with microscopic pore structures. Membrane filters typically have absolute pore size ratings <1µm, with some exceptions. Because of their very fine pore structure, membrane filters tend to trap the majority of particles on the surface. However, smaller particles with diameters near or below the pore size rating can be captured within the membrane or pass through the membrane.

membrane filters vs separator papers

To ensure ease of use, the membrane filters as stacked in their packaging are interleafed with layers of separator paper.  In most cases, the membrane filters will be white in color except for the track-etch membranes which are colorless and translucent.  In some special cases, the membranes will be dyed dark grey to black in appearance.  In all cases, the separator paper will be a different color than the membrane and is usually not white.  Please contact us at [email protected] if you need assistance.