Cellulose Acetate Membrane Filters, 0.8 Micron, 293mm, 25/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 0.8 microns and a diameter of 293 mm
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General
| Sterilization | Gamma Irradiation, EtO, Autoclave |
| USP Class VI Test | Passed |
| BSA Protein Binding | 3.8 µg/cm2 |
| Max Operating Temp | 135 °C (275 °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 |
1. Flow Rates: Measured with water as ml/min/cm2 at 10 psi (0.7kg/ cm2)
- 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
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Frequently Asked Questions
Q: What is the difference between hydrophilic and hydrophobic membrane filters?
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.
Q: Is your Cellulose Acetate (CA) membrane made of mono-, di-, or triacetate?
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?
The maximum operating temperatures for Sterlitech filter membranes are listed below.
- Sterlitech Silver Metal - 427°C
- Sterlitech Ceramic - 350°C
- Sterlitech Polycarbonate Track Etch - 140°C
- Sterlitech Polyester - 140°C
- Sterlitech Nitrocellulose (MCE) - 130°C
- Sterlitech Nylon - 180°C
- Sterlitech Polyethersulfone (PES) - *130°C
- Sterlitech Polypropylene - 82°C
- Sterlitech Cellulose Acetate - 135°C
- Sterlitech PTFE (Laminated) - 130°C
- Sterlitech PTFE (Unlaminated) - 260°C
*5.0um and 8.0um - max temp is 180°C
Q: What are the differences between cellulose acetate (CA), nitrocellulose (NC), Mixed Cellulose Esters (MCE) and regenerated cellulose (RC) membrane filters?
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.
Q: What is the shelf life of your membranes?
Cellulose acetate (CA) and nitrocellulose (MCE) membranes will last 2 1/2 to 3 years before reverting to their natural hydrophobic states. Nylon, on the other hand, is naturally hydrophilic so it does not have a shelf life.
An easy test for older membranes is to perform a "wetting out" test. Dipping a small portion of the membrane into water (hydrophilic membranes) or an alcohol (hydrophobic membranes) works well. If the membrane absorbs the material, or "wets out", it has not gone past the shelf life.
Q: Do Sterlitech cellulose acetate (CA) membrane filters contain a surfactant?
Yes, the cellulose acetate (CA) membranes contain a proprietary surfactant. The surfactant is used to ensure the CA membrane filters have good wettability.
Q: Do you need a Chemical Compatibility Chart?
We have a Chemical Compatibility Chart that you can use for reference.
Q: What is the difference between nominal and absolute pore size ratings?
Nominal pore size ratings provide a general indication of filter retention efficiency, meaning some particles equal to or larger than the stated pore size may pass through the filter. Nominal ratings can vary by manufacturer, so filters with the same nominal pore size may not offer equivalent filtration performance.
Absolute pore size ratings are determined through controlled particle or microbial retention testing and represent the smallest particles that are consistently retained by the membrane. These ratings are often correlated with bubble point specifications and are generally more comparable across manufacturers.
Important: Actual filtration performance depends on application conditions, even when using filters with absolute pore size ratings.
Q: What is the amount of Lignin, if any, in the Cellulose Acetate membranes?
Excluding the polyester support layer, Cellulose Acetate (CA) membrane filters are composed entirely of cellulose acetate polymer. There may be a very small amount of residual lignin present as a trace component. This minimal lignin content does not affect the performance, purity, or reliability of CA membrane filters in typical laboratory, analytical, and sample filtration applications.
Q: What is the difference between pore size and porosity?
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%.
Q: What are the advantages of Cellulose Acetate (CA) membrane filters?
Cellulose Acetate (CA) membrane filters are among the lowest protein-binding membranes available, making them ideal for applications requiring maximum protein recovery. They provide high throughput with protein-rich solutions and are commonly used for filtering proteins, enzymes, tissue culture media, serums, and biological fluids.
CA membranes feature an integral nonwoven polyester (PET) support layer, offering strength, dimensional stability, and easy handling, with resistance to tearing and curling. They are naturally hydrophilic, wet easily with aqueous solutions, offer good chemical resistance, are compatible with low molecular weight alcohols, and can withstand steam sterilization up to 135 °C.
Q: How do I determine if my filter is compatible with my application?
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.
Q: What is a bubble point and how is it determined?
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.
Q: What is the difference between a depth filter and membrane filter?
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.
Q: What's the benefit of purchasing sample packs?
Sample packs allow the customer to purchase small quantities of membrane filters at nominal cost, with various diameters and pore sizes as selected. This allows the customer to preform trials as needed to determine the optimal filter for their application before committing to purchasing standard pack quantities.
Q: Are membrane filter samples available in diameters others than 13, 25, or 47mm?
In most cases, membrane filter samples can be purchased in sizes that are not listed in the standard sample packs. Please contact us at [email protected] to inquire about availability and pricing.
Q: How can I tell the difference between the separator papers and the membrane filters?
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.
