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Filters & Filtration
Filtration is a physical separation method used to separate solids from liquids and gases. Depending on the application, different filters are required for a filtration process. A distinction is made between round and pleated filters, syringe filters, filter rolls and filter plates.
We provide everything needed in the laboratory for all filtration requirements: filter papers, glass fiber filters, membrane filters from well-known manufacturers such as Machery Nagel, Merck Millipore, Pall Corporation, Sartorius and Whatman. We also supply filter funnels, filtervials and funnels made of different materials as well as the corresponding filtration apparatuses, units and accessories.
Glass Fiber Filter
The Schleicher & Schuell brand is part of the Whatman group but their filters are graded differently. The following table should simplify the task of comparing the different glass fibre media for your filtration needs.
| Sartorius | Whatman | Schleicher & Schuell | Sartorius | Whatman | Schleicher & Schuell | |
|---|---|---|---|---|---|---|
| MGA | GF/A | GF 50 | MGF | GF/F | GF 55 | |
| MGB | GF/B | GF 51 | MGF 550-HA | 934AH | n/a | |
| MGC | GF/C | GF 52 | MK 360 | QM-A | n/a | |
| MGD | GF/D | GF 53 |
Filter Papers
Paper filters are made from natural and synthetic, organic and inorganic fibers. Depending on the material and fiber structure, they are used in the laboratory in various areas in which solids are separated from liquids and gases.
There are different types of paper filters such as folded filters, round filters or filter sheets. Special filter papers are required for filtration under pressure or in a vacuum, which have a high wet resistance due to the addition of resin.
Membrane Filter
Membrane filters allow the filtration of minute components by retaining impurities larger than the pore size on the membrane surface. This leads to a cleaning and concentration. The membrane filters differ in their pore size, material and diameter. They are mostly used for critical applications such as sterilization and end filtration. Paper filters are available as round filters or folding filters. Both differ in their diameters and thicknesses. There are also many other filter types like glass fiber filter, inline filter or gas GC filter.
In the following table the most common membrane filter materials and their retention characteristics are shown.
| Material | Retention Characteristics |
|---|---|
| Celluloseacetate (CA) | Low protein-binding, well suited for sterile filtration and clarification of aqueous solutions, nutrient media, buffers, and sera, they provide superior chemical resistance to alcohol and oil. These hydrophilic membranes offer excellent flow rates as well as thermal stability up to 180°C max. |
| Cellulosenitrate (CN) | Cellulose nitrate membranes set the standard in both analytical and microbiological filtration. Cellulose nitrate is available in a range of pore sizes and is well suited for microbial analysis in water, food and beverage applications. Available in dispenser strips or individually sealed. |
| Polyamide (PA) | Membranes are hydrophilic and are widely used in both aqueous and organic solvent filtration applications. Well suited for sterilization and clarification of buffers and nutrient media with a low level of extractables. |
| Polycarbonate (PC) | PC membranes have uniform, smooth-bore, round pores that pass straight through the membrane creating a precise capillary structure. The smooth, flat surface of the PC membrane offers high visibility of captured particles. |
| Polytetrafluorethylen (PTFE) | Permanently hydrophobic filter material, very suitable for air and gas filtration. PTFE membranes are extremely resistant to aggressive solvents and acids and can be used to filter particulate from both liquid and gas samples. |
| Regenerated Cellulose (RC) | Regenerated cellulose membranes are resistant to solvents and are hydrophilic. 0.45 μm pore size is typically used for HPLC sample preparation. |
Syringe Filter
The filter materials used for syringe filters are equivalent to the ones used in membrane filters. Please refer to the table of membrane filters above for that information.