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What Is a Millipore Filter?

By Jillian O Keeffe
Updated May 17, 2024
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Millipore is a company that makes scientific and manufacturing equipment. Part of their range is filters. These filters may be designed for laboratory testing or filtration steps during a manufacturing process. A Millipore filter can be a thin membrane, a syringe filter, or contained in a capsule-like housing. They can be sterile or nonsterile.

The company that makes the filters is based in Massachusetts in the United States. Millipore is part of the Merck group and has customers all over the world. Its focus is on pharmaceutical and biotechnology products and its products are sold to industries through laboratory supply companies.

A Millipore filter removes unwanted particles from a liquid or concentrates desired particles from the liquid. These particles can be inorganic matter like dust or organic matter like bacteria. Apart from manufacturing processing, the filters are used in microbiology and chemistry lab testing. Air can also be sampled using Millipore filters. The filters range in diameter from 13 millimeters (mm), or 0.5 inches, to 293 mm (11.5 inches) and are made from materials such as nitrocellulose or polyethersulfone.

Each type has a specific pore size, which prevents particles of a certain size from getting through the filter. The pore size ranges from 0.2 micrometers (µm) up to 12 µm. A pore size of 0.45 µm catches bacteria, and the smaller pore sizes are used for chemistry samples. The larger pore sizes are suitable for manufacturing steps that do not need to remove microbes from the liquid.

One filterable liquid is water, used in manufacturing a product and also used in many laboratory tests. Materials in liquid form that must be mixed up to form a product may also require filtration. The finished product may also undergo the purification process. Finally, analytical samples can be liquid or can be mixed in liquid.

Microbiology lab analysts generally use a Millipore filter in the form of a thin membrane in sample testing. These thin membranes are generally sterile and only used once. They are placed in specialized equipment such as filter funnels, removed when the water is all drawn through, and tested.

Another use for a Millipore filter is in the form of a capsule or a cartridge. This is a casing that has a membrane inside. The filter may not be sterile but may be tough enough to survive a sterilization process in an autoclave if required. They can be used to reduce the contamination of a liquid or to sterilize the liquid and are an important part of the filtration of raw materials and products in the manufacturing process.

Syringe filters reduce the potential for chemistry samples to clog up equipment. Centrifugal filters are filled with protein or genetic material. They then undergo centrifugation to spin the sample through the pores.

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