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Filtration steps are involved in many laboratory applications such as sample purification, sample concentration, liquid sterilization, particle sampling, and much more. The properties of your filter determine the success of your filtration step.
Selecting a filter with the correct properties can help you achieve accurate results and reach your goals faster. But with so many types of filters to choose from, how can you be sure to make the right choice?
The tabs below contain information to help you select the correct filter for your application. In addition, our laboratory filtration brochure contains more detailed information.
There may be multiple reasons for filtering a sample, such as:
The filtration step may be a direct part of the analysis or process or may be used to facilitate the analysis or process by for example removing contaminants.
For a more extensive filtration glossary, please refer to our laboratory filtration brochure.
Our Whatman brand features a large variety of filter media, such as filter papers, glass microfiber filters, and membrane filters.
Our qualitative and quantitative cellulose filters are used for general filtration and exhibit particle retention levels down to 2.5 µm. We offer a wide choice of retention/flow rate combinations to meet the needs of numerous laboratory applications.
Borosilicate glass microfibers combine fast flow rates with high loading capacities and retention of very fine particles. Glass microfiber filters must be used flat and should not be folded. Binder-free glass microfiber filters withstand temperatures up to 500ºC and can therefore be used in gravimetric analysis where ignition is involved. Glass microfiber filters exhibit excellent compatibility with organic solvents and strong acids (apart from hydrofluoric acid) and bases. They can be used as prefilters or as final filters, and can retain particles as small as 0.7 µm.
Unlike cellulose and glass microfiber depth filters, membrane filters are conventionally classified as surface filters because the filter matrix retains particles almost entirely on membrane the surface. The narrow effective pore size distribution is one of the major features of Whatman membrane filters, and the retention levels for these filters extend down to 0.02 µm.
Learn more about different membrane filter materials
The selection of a laboratory filter depends on the conditions and objectives of your experiment or analytical procedure. The three most important characteristics of any laboratory filter are:
According to your particular application, other important filter characteristics may also require examination, for example wet strength, chemical resistance, purity, and ash level.
Filtration Methods for flat filters
|Cellulose Filter Papers||Suitable||Suitable||Not generally used|
|Glass Microfiber||Not suitable||Suitable||Suitable|
Maximum practical volumes of cellulose filter paper circle sizes (quadrant folded)
|Filter Diameter (mm)||90||110||125||150||185||240|
Selection tree and tables to help you identify the appropriate filter paper
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