What’s the Difference between Sartorius Membrane Filters?
Sartorius offers a wide selection of membrane materials for microfiltration in a variety of applications including: cell retention, particle collection, clarification and sterile filtration of aqueous solutions, particulate analysis, microbiological analysis, and epifluorescence microscopy. Since Sartorius membrane filters are offered in a variety of materials, it is important to know the difference between them. The descriptions below will help you make well-informed decisions. The membrane filter type choices are Cellulose Nitrate, Cellulose Acetate, PTFE, Polyethersulfone (PES), Regenerated Cellulose, Polycarbonate, and Polyamide.
Cellulose Nitrate is a standard material for membrane filters. The larger pore sizes (8 µm, 5 µm, 3 µm) are best used for cell retention, while the 0.45 µm pore size is great for particle collection. The high non-specific absorption of the cellulose nitrate membrane is advantageous for diagnostic kits.
This one combines high flow rates and thermal stability with very low absorption characteristics, and is therefore well suited for use in pressure filtration devices. The 0.2µm pore size is the filter of choice for sterile filtration of aqueous solutions, such as nutrient media, buffers, and sera. Unfortunately, the results of publications on absorption are difficult to correlate. They are difficult due to factors such as different test substances, conditions, and detection methods being used.
This membrane filter is typically used for gas/air-filtration, because it is permanently hydrophobic. This means that unlike other (hydrophilic) filter types, it is not wetted by air humidity. Due to its excellent chemical compatibility, this membrane is also used for the filtration of solvents and acids. Because of its hydrophobic characteristics, a PTFE membrane must be pre-wetted with ethanol or methanol before the filtration of aqueous media.
Polyethersulfone membrane filters have exceptional flow speeds and a high filterable volume. They are able to filter biologic and pharmaceutical solutions (within the wide pH-range of pH 2-12) because of their low protein absorption. These membranes are also well suited for environmental samples, and the filter with 0.1µm can be used for the ultra-cleaning of solutions, e.g. in case of nephelometry.
Because of their solvent-resistant and hydrophilic nature, the main application for these membrane filters is the removal of particles from solvents. For example, the 0.45µm pore size filter is standardly used to ultraclean and de-gas solvents and mobile phases for HPLC. Regenerated cellulose membrane filters also feature low non-specific-adsorption.
These filters are manufactured from high-grade polycarbonate film using track-etch technology. Their capillary structure is precise and uniform, with a narrow pore size distribution. They are well-suited for the accurate fractionation of particles because of their smooth, flat surface that results in high particulate visibility. Polycarbonate membrane filters are generally used in the following applications: particulate analysis and epifluorescence. They are also used for applications such as: microscopy, fluid clarification, cytology, cell biology, bioassays, water microbiology, and environmental analysis.
These types of membrane filter are hydrophilic and chemical resistant to alkaline solutions and organic solvents. Polyamide membrane filters are excellent for use in the particle removing filtration of water. These filters are also excellent for use in aqueous solutions and solvents for analytical determination (such as HPLC), as well as the sterile filtration of the liquids mentioned. They are also highly recommended for the isolation of Legionella. They have a high non-specific absorption, which can cause the loss of important substances and therefore limits their application.
(Information provided by the Sartorius website.)